materials for participants – module instruction sequence ...dlewin/cache_workshop/workshop...

Materials for Participants – Module Instruction Sequence and Problem Statements by Core Course

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Workshop 12 “Simulators for Design Across the Curriculum” ASEE Summer School, Colorado, August 2002

Workshop Leaders: Daniel R. Lewin (DRL), Dept. of Chemical Engineering, Technion. Warren D. Seider (WDS), Dept. of Chemical Engineering, Penn. Workshop Objective: During the senior year design project, teams of students carry out an integrated process design, determining its technical, environmental, safety, and economic feasibility. Due to the problem scale, this inevitably involves the use of a process simulator to formulate and solve the material and energy balances, with phase and chemical equilibria and chemical kinetics, for cost estimation and economic evaluation. The availability of a reliable process model allows the design team to assess rapidly the economic potential for alternative designs, as well as to derive operating conditions using optimization methods that incorporate economics. To ensure that students are prepared to meet the challenges of the design project, they should be prepared for the competent and critical use of the process simulators. This is best achieved by a gradual exposure to aspects of their use through various exercises in the core courses. This workshop, which is intended for chemical engineering faculty, shows one way to achieve this objective.

Contents: This document is an assembly of: (1) suggested instruction sequences, using the multimedia CD-ROM (Using Process Simulators in Chemical Engineering: A Multimedia Guide for the Core Curriculum), henceforth referred to as the multimedia, and (2) problem statements and solutions for class exercises and projects using process simulators to support many of the chemical engineering core courses. Materials are included for courses on: Material and Energy Balances, Thermodynamics, Heat Transfer, Separation Principles, and Reactor Design. ASPEN PLUS, HYSYS.Plant, BATCH PLUS, and IPE files used for the solutions of the exercises are also available on this CD. In addition, each participant of Workshop 12 will receive a CD Containing Version 1.2 of Using Process Simulators in Chemical Engineering: A Multimedia Guide for the Core Curriculum.


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Chemical Engineering Principles and Material and Energy Balances

HYSYS.Plant

The materials supporting a course in material and energy balances assume that that at least four hours of computer laboratory time is allocated to the exercises. A self-paced approach using the multimedia allows the students to bring themselves “up-to-speed” on the use of a process simulator to develop and solve material and energy balances of process flowsheets involving simple models of unit operations and recycles. The following sequence of modules is recommended:

Session 1: Under Principles of Process Flowsheet Simulation, access Getting Started in HYSYS (overview). Its main menu consists of four sections (1. Define the Fluid Package, 2. Set Up the Simulation, 3. Convergence of Simulation, and 4. Advanced Techniques). Students should review all three modules in the first section on the fluid package, and the first three modules in the second section on setting up the simulation.

Session 2: At this point, the student should be ready to construct and solve a relatively simple

example. The first tutorial supporting a course in M&E balances, Ammonia/Water Separation, is appropriate. The student should follow the multimedia while at the same time develop his/her version of the simulation using HYSYS.Plant.


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Session 3: Begin by reviewing material learned so far – review the module “Do It Yourself (the fifth module under Getting Started in HYSYS - 2. Set Up the Simulation). Next briefly review the section Getting Started in HYSYS - 3. Convergence of Simulation, paying particular attention to the section on Recycle Implementation.

Session 4: At this point, the student should try to set up and solve a flowsheet involving

material recycle. The second tutorial supporting a course in M&E balances, Ethylchloride Manufacture, is appropriate. The student should follow the multimedia while at the same time develop his/her version of the simulation using HYSYS.Plant.

Session 5: If additional time is available, the student can complete the review of materials

supporting initial use of HYSYS.Plant, i.e., the remaining items in Getting Started in HYSYS - 3. Convergence of Simulation, and Getting Started in HYSYS - 4. Advanced Techniques. The most important features that should be covered are the materials that support for the use of the Spreadsheet and Databook, to assist in sensitivity analysis. If time is available, the student should also cover the use of Set and Adjust (in Part 3) and the Optimizer (in Part 4).

A project should be assigned to groups of up to three students, to reinforce their acquired capabilities. A typical project definition is provided.


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Chemical Engineering Principles and Material and Energy Balances

ASPEN PLUS

The materials supporting a course in material and energy balances assume that that at least four hours of computer laboratory time is allocated to the exercises. A self-paced approach using the multimedia allows the students to bring themselves “up-to-speed” on the use of a process simulator to develop and solve material and energy balances of process flowsheets involving simple models of unit operations and recycles. The following sequence of modules is recommended. Note that this sequence has not been class-tested using ASPEN PLUS. However, a similar sequence using HYSYS.Plant, on the previous two pages, has been class-tested successfully:

Session 1: Under Principles of Process Flowsheet Simulation, access Getting Started in ASPEN PLUS (overview). Its main menu consists of five sections (1. Brief Introduction, 2. Setting Up, 3. Convergence, 4. Sensitivity Analysis, and 5. Sample Problem). Students should review modules 1-3 and 5.

Session 2: At this point, the student should be ready to construct and solve a relatively simple

example. The first tutorial supporting a course in M&E balances, Ammonia/Water Separation, is appropriate. The student should follow the multimedia while at the same time develop his/her version of the simulation using ASPEN PLUS.


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Session 3: Briefly review the section ASPEN -Getting Started - 3. Convergence, paying particular attention to the section on Recycle.

Session 4: At this point, the student should try to set up and solve a flowsheet involving

material recycle. The second tutorial supporting a course in M&E balances, Ethylchloride Manufacture, is appropriate. The student should follow the multimedia while at the same time develop his/her version of the simulation.

Session 5: If additional time is available, the student can complete the review of materials

supporting initial use of ASPEN PLUS, i.e., the remaining items in ASPEN - Getting Started - 3. Convergence (especially, Control Blocks), and ASPEN - Getting Started - 4. Sensitivity Analysis.

A project should be assigned to groups of up to three students, to reinforce their acquired capabilities. A typical project definition is provided. Three homework problems are suggested: (Exercise A.1) (Exercise A.2) (Exercise A.3)

BATCH PLUS BATCH PLUS, an Aspen Tech product, carries out material and energy balances for batch plants and prepares operating schedules (Gantt charts). In the second edition of SSL, we have added material on the synthesis of a process to manufacture tissue plasminogen activator (tPA). Then, a simulation of the tPA process is carried out using BATCH PLUS. For a course on chemical engineering principles and material and energy balances at the sophomore level, this material could be presented with the exercise provided below. The file TPA SYNTHESIS.PDF provide the text that covers the synthesis and simulation steps.


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Material and Energy Balances – Example Project

Methanol is manufactured in a “synthesis loop,” in which a mixture of carbon dioxide and hydrogen is reacted to form the methonal product at high pressure:

OHOHCH H 3+ CO 2322 +←→

The synthesis gas fed to the process, illustrated above, is largely composed of hydrogen

and carbon dioxide, but with traces of inert gases as in Table 1. Additional specifications for the process are: SRK property predictions should be employed Pressure drops is all units can be neglected Converter feed temperature is set to 400 oC The converter can be approximated as a conversion reactor, operating

adiabatically. The reactor conversion depends of the operating pressure, according to Table 2. The reactor effluent is cooled to a temperature of TS using a cooler, and fed to a

flash unit, modeled by a separator.

Table 1. Process feed stream specification. Composition ( mol %) Hydrogen 74.85 Carbon dioxide 24.95 CH4 0.1 Argon 0.1

Flow rate (kgmol/hr) 1000 Temperature (oC) 50

Pressure (MPa) PS

Table 2. Conversion as a function of pressure PS [MPa] CO2 conversion [%] PS [MPa] CO2 conversion [%]

5.0 28.0 20.0 35.5 7.5 29.5 22.5 37.0

10.0 31.0 25.0 38.5 12.5 32.5 30.0 40.0 15.0 34.0

Feed 500CPs

S-1 S-2 S-3

S-4 Ts

Product

Purge

Separator

AdiabaticConverter

4000C

Heater

Cooler

S-5

S-6


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Your tasks: 1. Solve the material and energy balances for the flowsheet for a purge flow rate of 600

kg/h, and values for PS and TS by group, according to Table 3. Ensure an accuracy of 3 significant figures.

Table 3. Operating specifications by student group.

Group No. TS (°C) PS (MPa) Group No. TS (°C) PS (MPa) 1 10 16 10 2 20 17 20 3 30

5.0 18 30

17.5

4 10 19 10 5 20 20 20 6 30

7.5 21 30

20.0

7 10 22 10 8 20 23 20 9 30

10.0 24 30

22.5

10 10 25 10 11 20 26 20 12 30

12.5 27 30

25.0

13 10 28 10 14 20 29 20 15 30

15.0 30 30

30.0

2. An operating window for the process is defined by a closed polygon in TS –Purge space,

within which, the following constraints are met: 200 < Purge < 1000 kg/h

0 < TS < 40oC Mass flow rate of recycle ≤ 35 T/hr

CO2 mol. fraction in product ≤ 2.5 mol % Mass flow rate of methanol in product ≥ 7,200 kg/hr

Determine the operating window for the operating pressure for your group in Table 3. Try and estimate the limits of the operating window as accurately as possible, and plot the result as a function of TS and Purge flow rate, as shown below.

HYSYS.Plant Solution

Purge [kg/h]

T s [o C

] Operating Window


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Exercise A.1 Flash with Recycle Problem (Exercise 3.1, SSL)

a. Consider the flash separation process shown below:

If using ASPEN PLUS, solve all three cases using the MIXER, FLASH2,

FSPLIT, and PUMP subroutines and the RK-SOAVE option set for thermophysical properties. Compare and discuss the flow rates and compositions for the overhead stream produced by each of the three cases.

b. Modify Case 3 of Exercise 3.1a to determine the flash temperature

necessary to obtain 850 lb/hr of overhead vapor. If using ASPEN PLUS, a design specification can be used to adjust the temperature of the flash drum to obtain the desired overhead flow rate.

ASPEN PLUS Solution


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Exercise A.2 Ammonia Synthesis Loop Problem (Example 4.3, SSL)

For the ammonia process in Example 4.3, consider operation of the reactor at 932°F and

400 atm. Use a simulator to show how the product, recycle, and purge flow rates, and the mole fractions of argon and methane, vary with the purge-to-recycle ratio. How do the power requirements for compression increase? Example 4.3 Ammonia Process Purge

In this example, the ammonia reactor loop:

is simulated using ASPEN PLUS to examine the effect of the purge-to-recycle ratio on the purge stream and the recycle loop. For the ASPEN PLUS flowsheet below, the followingspecifications are made:

Simulation Unit Subroutine T,°F P,atm

R1 REQUIL 932 200

F1 FLASH2 -28 136.3

and the Chao-Seader option set is selected to estimate the thermophysical properties. Note that the REQUIL subroutine calculates chemical equilibria at the temperature and pressure specified, as discussed in the REQUIL module on the multimedia CD-ROM.

The combined feed stream, at 77°F and 200 atm, is comprised of:

lbmole/hr Mole fraction H2 24 0.240 N2 74.3 0.743 Ar 0.6 0.006 CH4 1.1 0.011 100.0 1.000

ASPEN PLUS Solution


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Exercise A.3 Near-isothermal Distillation (Cavett) Problem (Exercise 3.7, SSL)

A near-isothermal distillation process, having multiple recycle loops formulated by R. H. Cavett (Proc. Am. Petrol. Inst., 43, 57 (1963)), has been used extensively to test tearing, sequencing, and convergence procedures. Although the process flowsheet requires compressors, valves, and heat exchangers, a simplified ASPEN PLUS flowsheet is (excluding the recycle convergence units):

In this form, the process is the equivalent of a four-theoretical-stage, near-isothermal distillation (rather than the conventional near-isobaric type), for which a patent by A. Gunther (U.S. Patent 3,575,077, April 13, 1971) exists. For the specifications shown on the flowsheet, use a process simulator to determine the component flow rates for all streams in the process.

ASPEN PLUS Solution


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Exercise A.4 Scheduling Batch Reactors Problem (New Exercise 4.19, SSL)

Debottlenecking Reactor Train. To prepare for this exercise, read the background materials in TPA SYNTHESIS.PDF. These new sections are for the second edition of SSL.

When the third tPA cultivator in Section 3.4 is added to the two cultivators in Example

4.1, as shown in Figure 4.25a, a significant time strain is placed on the process because the combined feed, cultivation, harvest, and cleaning time in this largest vessel is long and rigid. Consequently, the remainder of the process is designed to keep this cultivator in constant use, so as to maximize the yearly output of product. Note that, in many cases, when an equipment item causes a bottleneck, a duplicate is installed so as to reduce the cycle time.

For this exercise, the third cultivator is added to the simulation in Example 4.1, with the specifications for the mixer, filter, holding tank, heat exchanger 1, and first two cultivators identical to those in Example 4.1. After the cultivation is completed in Cultivator 2, its cell mass is transferred as inoculum to Cultivator 3 over 0.5 day. Then, the remaining media from the mixing tank is heated to 37°F and added over 1.5 day, after which cultivation takes place over eight days. Immediately after the transfer from Cultivator 2 to Cultivator 3, Cultivator 2 is cleaned-in-place using 600 Kg of water over 20 hours. The yield of the cultivation in Cultivator 3 is 11.4 wt% tPA-CHO cells, 7.7 × 10-5 wt% endotoxin, 88.9 wt% water, and 0.0559 wt% tPA. When the cultivation is completed in Cultivator 3, its contents are cooled in a heat exchanger to 4°C and transferred to the centrifuge holding tank over one day, and Cultivator 3 is cleaned using 600 Kg of water over 67 hours and sterilized using the procedure for Cultivators 1 and 2.

To eliminate an undesirable bottleneck(s), and reduce the cycle time to 14 days (total

operation time of Fermenter 3), it may be necessary to add an equipment unit(s). Print and submit the text recipes and 3-batch schedules for both the original process and

the modified process, if debottlenecking is necessary, as prepared by BATCH PLUS.

For background materials and BATCH PLUS solution, see

TPA SYNTHESIS.PDF


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Material and Energy Balances – Solution Sketch of Example Project using HYSYS.Plant

1. The flowsheet is set up and its material and energy balance solved using HYSYS.Plant is

a straight-forward fashion. A sample solution file is given as METHANOL_PART1.hsc.

2. The second part of the problem is more interesting. This involves the use of the

Spreadsheet, to generate Boolean variables corresponding to the feasibility of each of the

three constraints:

Recycle: Mass flow rate of recycle ≤ 35 T/hr

Purity: CO2 mol. fraction in product ≤ 2.5 mol %

Production: Mass flow rate of methanol in product ≥ 7,200 kg/hr

Subsequently, the Databook is used to construct 3D plots involving the Boolean variables

as a function of TS and Purge. Sample operating windows in TS –Purge space, for

flowsheets designed for PS = 5 and 30 MPa are shown in Figure 1, noting that the

interpretation of the operating widows is given schematically in Figure 2. In general, the

recycle and production constraints lead to lower and upper limits on the allowed purge

flow rate, both of which are relatively independent on the separation temperature, TS. In

constrast, the purity constraint leads to a lower limit on TS, whose value increases with

increasing purge flow rate. As seen in Figure 1, the operating window is significantly

more limited for operation at lower pressures. The files METHANOL_PART2_05.hsc

and METHANOL_PART2_30.hsc provide sample solutions.

(a) (b) Figure 1: Operating windows for (a) PS = 5 MPa; (b) PS = 30 MPa


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Purge

TS

0 oC

40 oC

Operating Window Purity

Recycle

Production

Figure 2: Interpretation of constraints bounding the operating window.

The selection of operating point should consider the cost of energy, which increases

significantly as TS decreases, and the equipment costs, which increase exponentially with

decreasing purge flow rate. An appropriate choice would be at the top right-hand corner of the

operating window.


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Exercise A.1 Solution using ASPEN.PLUS

3.1 a. ASPEN PLUS Flowsheet – simulation results can be reproduced using the file EXER3-1A.BKP on the CD-ROM.

ASPEN PLUS Simulation Flowsheet

S4S4*

S2

LP

VP

M1MIXER

FEED1

FEED2

$OLVER01

F1FLASH2

S5 S3

S1FSPLIT

P1PUMP

M1

S5

FEED2

FEED1

S2

F1

VP

S3

S1LPS4

P1


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ASPEN PLUS Program IN-UNITS ENG

DEF-STREAMS CONVEN ALL DATABANKS PURE93 / AQUEOUS / SOLIDS / INORGANIC / &

NOASPENPCD PROP-SOURCES PURE93 / AQUEOUS / SOLIDS / INORGANIC COMPONENTS METHANE CH4 METHANE / ETHANE C2H6 ETHANE / PROPANE C3H8 PROPANE / N-BUTANE C4H10-1 N-BUTANE / 1-BUTENE C4H8-1 1-BUTENE / 1,3-BUTA C4H6-4 1,3-BUTA FLOWSHEET BLOCK M1 IN=S5 FEED2 FEED1 OUT=S2 BLOCK F1 IN=S2 OUT=VP S3 BLOCK S1 IN=S3 OUT=LP S4 BLOCK P1 IN=S4 OUT=S5 PROPERTIES RK-SOAVE PROP-DATA RKSKIJ-1 IN-UNITS ENG PROP-LIST RKSKIJ BPVAL METHANE ETHANE -7.8000000E-3 BPVAL METHANE PROPANE 9.00000000E-3 BPVAL METHANE N-BUTANE 5.60000000E-3 BPVAL ETHANE PROPANE -2.2000000E-3 BPVAL ETHANE N-BUTANE 6.70000000E-3 BPVAL ETHANE METHANE -7.8000000E-3 BPVAL PROPANE ETHANE -2.2000000E-3 BPVAL PROPANE N-BUTANE 0.0 BPVAL PROPANE METHANE 9.00000000E-3 BPVAL N-BUTANE ETHANE 6.70000000E-3 BPVAL N-BUTANE PROPANE 0.0 BPVAL N-BUTANE METHANE 5.60000000E-3 BPVAL N-BUTANE 1-BUTENE -4.8000000E-3 BPVAL N-BUTANE 1,3-BUTA 8.10000000E-3 BPVAL 1-BUTENE N-BUTANE -4.8000000E-3 BPVAL 1-BUTENE 1,3-BUTA -4.4000000E-3 STREAM FEED1 SUBSTREAM MIXED TEMP=85 <C> PRES=100 MASS-FLOW METHANE 50 / ETHANE 100 / PROPANE 700 STREAM FEED2 SUBSTREAM MIXED TEMP=85 <C> PRES=100 MOLE-FLOW N-BUTANE 15 / 1-BUTENE 21 / 1,3-BUTA 95 BLOCK M1 MIXER BLOCK S1 FSPLIT FRAC S4 0.5 BLOCK F1 FLASH2 PARAM TEMP=5 <C> PRES=25 BLOCK P1 PUMP PARAM PRES=100

Calculation Sequence SEQUENCE USED WAS: $OLVER01 P1 M1 F1 S1 (RETURN $OLVER01)


– 16 –

Stream Variables

FEED1 FEED2 LP S2 S3--------------------

STREAM ID FEED1 FEED2 LP S2 S3FROM : ---- ---- S1 M1 F1TO : M1 M1 ---- F1 S1

SUBSTREAM: MIXEDPHASE: VAPOR VAPOR LIQUID MIXED LIQUIDCOMPONENTS: LBMOL/HR

METHANE 3.1166 0.0 2.1961-02 3.1386 4.3923-02ETHANE 3.3256 0.0 0.1616 3.4872 0.3232PROPANE 15.8742 0.0 2.7989 18.6731 5.5978N-BUTANE 0.0 15.0000 6.8587 21.8587 13.71751-BUTENE 0.0 21.0000 9.0466 30.0466 18.09321,3-BUTA 0.0 95.0000 41.5243 136.5243 83.0487

TOTAL FLOW:LBMOL/HR 22.3165 131.0000 60.4122 213.7286 120.8245LB/HR 850.0000 7188.8147 3280.9932 1.1320+04 6561.9864CUFT/HR 1472.6295 8135.3222 84.7851 8814.7421 169.5702

STATE VARIABLES:TEMP F 185.0000 185.0000 41.0000 126.7191 41.0000PRES PSI 100.0000 100.0000 25.0000 100.0000 25.0000VFRAC 1.0000 1.0000 0.0 0.7434 0.0LFRAC 0.0 0.0 1.0000 0.2565 1.0000SFRAC 0.0 0.0 0.0 0.0 0.0

ENTHALPY:BTU/LBMOL -4.0234+04 2.9758+04 1.3635+04 1.7911+04 1.3635+04BTU/LB -1056.3433 542.2708 251.0564 338.1758 251.0564BTU/HR -8.9789+05 3.8983+06 8.2371+05 3.8281+06 1.6474+06

ENTROPY:BTU/LBMOL-R -53.9876 -41.3689 -63.1321 -48.0510 -63.1321BTU/LB-R -1.4174 -0.7538 -1.1624 -0.9072 -1.1624

DENSITY:LBMOL/CUFT 1.5154-02 1.6103-02 0.7125 2.4247-02 0.7125LB/CUFT 0.5772 0.8836 38.6977 1.2841 38.6977

AVG MW 38.0883 54.8764 54.3100 52.9634 54.3100

S4 S5 VP--------

STREAM ID S4 S5 VPFROM : S1 P1 F1TO : P1 M1 ----

SUBSTREAM: MIXEDPHASE: LIQUID LIQUID VAPORCOMPONENTS: LBMOL/HR

METHANE 2.1961-02 2.1961-02 3.0947ETHANE 0.1616 0.1616 3.1639PROPANE 2.7988 2.7988 13.0753N-BUTANE 6.8587 6.8587 8.14111-BUTENE 9.0466 9.0466 11.95331,3-BUTA 41.5243 41.5243 53.4756

TOTAL FLOW:LBMOL/HR 60.4121 60.4121 92.9041LB/HR 3280.9860 3280.9860 4757.8142CUFT/HR 84.7849 84.9629 1.9089+04

STATE VARIABLES:TEMP F 41.0000 42.9764 41.0000


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PRES PSI 25.0000 100.0000 25.0000VFRAC 0.0 0.0 1.0000LFRAC 1.0000 1.0000 0.0SFRAC 0.0 0.0 0.0

ENTHALPY:BTU/LBMOL 1.3635+04 1.3701+04 1.2859+04BTU/LB 251.0555 252.2685 251.0950BTU/HR 8.2371+05 8.2769+05 1.1947+06

ENTROPY:BTU/LBMOL-R -63.1321 -63.0428 -44.6262BTU/LB-R -1.1624 -1.1607 -0.8714

DENSITY:LBMOL/CUFT 0.7125 0.7110 4.8669-03LB/CUFT 38.6977 38.6166 0.2492

AVG MW 54.3100 54.3100 51.2120

Selected Process Unit Output BLOCK: F1 MODEL: FLASH2------------------------------

INLET STREAM: S2OUTLET VAPOR STREAM: VPOUTLET LIQUID STREAM: S3PROPERTY OPTION SET: RK-SOAVE STANDARD RKS EQUATION OF STATE

*** MASS AND ENERGY BALANCE ***IN OUT RELATIVE DIFF.

TOTAL BALANCEMOLE(LBMOL/HR) 213.729 213.729 0.132980E-15MASS(LB/HR ) 11319.8 11319.8 -0.299808E-10ENTHALPY(BTU/HR ) 0.382808E+07 0.284209E+07 0.257568

*** INPUT DATA ***TWO PHASE TP FLASHSPECIFIED TEMPERATURE F 41.0000SPECIFIED PRESSURE PSI 25.0000MAXIMUM NO. ITERATIONS 30CONVERGENCE TOLERANCE 0.00010000

*** RESULTS ***OUTLET TEMPERATURE F 41.000OUTLET PRESSURE PSI 25.000HEAT DUTY BTU/HR -0.98599E+06VAPOR FRACTION 0.43468

V-L PHASE EQUILIBRIUM :

COMP F(I) X(I) Y(I) K(I)METHANE 0.14685E-01 0.36352E-03 0.33311E-01 91.633ETHANE 0.16316E-01 0.26757E-02 0.34056E-01 12.728PROPANE 0.87369E-01 0.46330E-01 0.14074 3.0378N-BUTANE 0.10227 0.11353 0.87630E-01 0.771851-BUTENE 0.14058 0.14975 0.12866 0.859201,3-BUTA 0.63877 0.68735 0.57560 0.83742


– 18 –

The results above are for Case 1 (50% bottoms recycle) in Figure 3.11. For Cases 2 (25% bottoms recycle) and 3 (no recycle), the vapor and liquid product streams are identical to those for Case 1. That is, the product streams and the heat removed from the flash vessel are identical regardless of the amount of recycle. This is because the vapor and liquid product streams are in phase equilibrium at the conditions of the flash vessel.

Acyclic Simulation Flowsheet

Since the product streams do not change with recycle flow rate, they can be computed at the conditions of the flash vessel. Then, given the recycle fraction, the other streams can be computed. This is accomplished using the following ASPEN PLUS simulation flowsheet.

S5 S2

S3

S4FEED2

FEED1

LPA

LPB

S1

S1B

S1A

LP

F1FLASH2

D1DUPL

MIX1MIXER

D2DUPL

MUL1MULT

P1PUMP

M1MIXER

MUL2MULT

VP

Using this flowsheet, identical results are obtained.

3.1 b. ASPEN PLUS Flowsheet – identical to that in Exer. 3.1a. The recycle flow rate is zero.

Simulation results can be reproduced using the file EXER3-1B.BKP on the CD-ROM.

ASPEN PLUS Simulation Flowsheet

FT

T

$OLVER02

S4 LP

VP

S2*M1MIXER

FEED1

FEED2

S2$OLVER01 F1

FLASH2

S5 S3

S1FSPLIT

P1PUMP

850 lb/hr


– 19 –

ASPEN PLUS Program – identical to that in Exer. 3.1a with following change and addition:

BLOCK S1 FSPLIT FRAC S4 0 DESIGN-SPEC OVHD DEFINE OVHD STREAM-VAR STREAM=VP SUBSTREAM=MIXED & VARIABLE=MASS-FLOW SPEC "OVHD" TO "850" TOL-SPEC "0.01 " VARY BLOCK-VAR BLOCK=F1 VARIABLE=TEMP SENTENCE=PARAM LIMITS "0" "100" Calculation Sequence SEQUENCE USED WAS: $OLVER01 *P1 M1 | $OLVER02 F1 | (RETURN $OLVER02) | S1 (RETURN $OLVER01) Stream Variables FEED1 FEED2 LP S2 S3--------------------

STREAM ID FEED1 FEED2 LP S2 S3FROM : ---- ---- S1 M1 F1TO : M1 M1 ---- F1 S1

SUBSTREAM: MIXEDPHASE: VAPOR VAPOR LIQUID VAPOR LIQUIDCOMPONENTS: LBMOL/HR

METHANE 3.1166 0.0 0.2336 3.1166 0.2336ETHANE 3.3256 0.0 1.3166 3.3256 1.3166PROPANE 15.8742 0.0 11.8773 15.8742 11.8773N-BUTANE 0.0 15.0000 13.9004 15.0000 13.90041-BUTENE 0.0 21.0000 19.2870 21.0000 19.28701,3-BUTA 0.0 95.0000 87.4743 95.0000 87.4743

TOTAL FLOW:LBMOL/HR 22.3165 131.0000 134.0894 153.3165 134.0894LB/HR 850.0000 7188.8147 7188.8082 8038.8147 7188.8082CUFT/HR 1472.6295 8135.3222 184.0987 9621.0871 184.0987


ENTHALPY:BTU/LBMOL -4.0234+04 2.9758+04 1.0003+04 1.9570+04 1.0003+04BTU/LB -1056.3433 542.2708 186.5833 373.2382 186.5833BTU/HR -8.9789+05 3.8983+06 1.3413+06 3.0004+06 1.3413+06


DENSITY:LBMOL/CUFT 1.5154-02 1.6103-02 0.7283 1.5935-02 0.7283LB/CUFT 0.5772 0.8836 39.0486 0.8355 39.0486


– 20 –

AVG MW 38.0883 54.8764 53.6120 52.4327 53.6120

S4 S5 VP--------STREAM ID S4 S5 VPFROM : S1 P1 F1TO : P1 M1 ----

SUBSTREAM: MIXEDPHASE: MISSING MISSING VAPORCOMPONENTS: LBMOL/HR

METHANE 0.0 0.0 2.8829ETHANE 0.0 0.0 2.0090PROPANE 0.0 0.0 3.9969N-BUTANE 0.0 0.0 1.09951-BUTENE 0.0 0.0 1.71291,3-BUTA 0.0 0.0 7.5256

TOTAL FLOW:LBMOL/HR 0.0 0.0 19.2270LB/HR 0.0 0.0 850.0064CUFT/HR 0.0 0.0 3852.4889

STATE VARIABLES:TEMP F MISSING MISSING 24.4944PRES PSI MISSING 100.0000 25.0000VFRAC MISSING MISSING 1.0000LFRAC MISSING MISSING 0.0SFRAC MISSING MISSING 0.0

ENTHALPY:BTU/LBMOL MISSING MISSING -3598.6336BTU/LB MISSING MISSING -81.4008BTU/HR MISSING MISSING -6.9191+04

ENTROPY:BTU/LBMOL-R MISSING MISSING -43.0246BTU/LB-R MISSING MISSING -0.9732

DENSITY:LBMOL/CUFT MISSING MISSING 4.9908-03LB/CUFT MISSING MISSING 0.2206

AVG MW MISSING MISSING 44.2088

Selected Process Unit Output BLOCK: F1 MODEL: FLASH2------------------------------

INLET STREAM: S2OUTLET VAPOR STREAM: VPOUTLET LIQUID STREAM: S3PROPERTY OPTION SET: RK-SOAVE STANDARD RKS EQUATION OF STATE

*** MASS AND ENERGY BALANCE ***IN OUT RELATIVE DIFF.

TOTAL BALANCEMOLE(LBMOL/HR) 153.317 153.317 -0.185379E-15MASS(LB/HR ) 8038.81 8038.81 -0.138062E-11ENTHALPY(BTU/HR ) 0.300039E+07 0.127212E+07 0.576015

*** INPUT DATA ***TWO PHASE TP FLASHSPECIFIED TEMPERATURE F 24.4945SPECIFIED PRESSURE PSI 25.0000MAXIMUM NO. ITERATIONS 30CONVERGENCE TOLERANCE 0.00010000

*** RESULTS ***


– 21 –

OUTLET TEMPERATURE F 24.494OUTLET PRESSURE PSI 25.000HEAT DUTY BTU/HR -0.17283E+07VAPOR FRACTION 0.12541

V-L PHASE EQUILIBRIUM :

COMP F(I) X(I) Y(I) K(I)METHANE 0.20328E-01 0.17428E-02 0.14994 86.038ETHANE 0.21691E-01 0.98189E-02 0.10449 10.641PROPANE 0.10354 0.88578E-01 0.20788 2.3469N-BUTANE 0.97837E-01 0.10367 0.57185E-01 0.551631-BUTENE 0.13697 0.14384 0.89091E-01 0.619391,3-BUTA 0.61963 0.65236 0.39141 0.60000


– 22 –


Several variables are tabulated as a function of the purge/recycle ratio:

Purge Purge

Purge/RecycleRatio

PROD flow rate, lbmole/h

Recycle flow rate, lbmole/h

Purge flow rate, lbmole/h

Mole fraction

Ar

Mole fraction

CH4

0.1 39.2 191.0 19.1 0.028 0.052 0.08 40.75 209.3 16.7 0.033 0.060 0.06 42.4 233.9 14.0 0.040 0.074 0.04 44.3 273.5 10.9 0.053 0.093 0.02 45.8 405.6 8.1 0.072 0.133

In all cases, the mole fraction of Ar and CH4 in the purge are significantly greater than in the feed. As the purge/recycle ratio is decreased, the vapor effluent from the flash vessel becomes richer in the inert species and less H2 and N2 are lost in the purge stream. However, this is accompanied by a significant increase in the recycle rate and the cost of recirculation, as well as reactor volume. Note that the EXAM4-3.BKP file on this CD-ROM can be used to reproduce these results. Although not implemented in this file, the purge/recycle ratio can be adjusted parametrically by varying the fraction of stream S5 purged in a sensitivity analysis, which is one of the model analysis tools in ASPEN PLUS. The capital and operating costs can be estimated and a profitability measure optimized as a function of the purge/recycle ratio.


– 23 –


ASPEN PLUS Flowsheet - simulation results can be reproduced using the file EXER3-7.BKP on the CD-ROM.

ASPEN PLUS Program

IN-UNITS ENGDEF-STREAMS CONVEN ALLDESCRIPTION "General Simulation with English Units :

F, psi, lb/hr, lbmol/hr, Btu/hr, cuft/hr.Property Method: None Flow basis for input: MoleStream report composition: Mole flow "

DATABANKS PURE10 / AQUEOUS / SOLIDS / INORGANIC / &NOASPENPCD

PROP-SOURCES PURE10 / AQUEOUS / SOLIDS / INORGANICCOMPONENTS

NITROGEN N2 NITROGEN /CO2 CO2 CO2 /H2S H2S H2S /METHANE CH4 METHANE /ETHANE C2H6 ETHANE /PROPANE C3H8 PROPANE /ISOBU-01 C4H10-2 ISOBU-01 /

FLASH2

F1

V2 L1

V1

FLASH2

F2FEED

V3

L2

FLASH2

F3

V4 L3

FLASH2

F4

L4


– 24 –

N-BUT-01 C4H10-1 N-BUT-01 /2-MET-01 C5H12-2 2-MET-01 /N-PEN-01 C5H12-1 N-PEN-01 /N-HEX-01 C6H14-1 N-HEX-01 /N-HEP-01 C7H16-1 N-HEP-01 /N-OCT-01 C8H18-1 N-OCT-01 /N-NON-01 C9H20-1 N-NON-01 /N-DEC-01 C10H22-1 N-DEC-01 /N-DOD-01 C12H26 N-DOD-01

FLOWSHEETBLOCK F1 IN=V2 OUT=V1 L1BLOCK F2 IN=FEED L1 V3 OUT=V2 L2BLOCK F3 IN=L2 V4 OUT=V3 L3BLOCK F4 IN=L3 OUT=V4 L4

PROPERTIES RK-SOAVEPROP-DATA RKSKIJ-1

IN-UNITS ENGPROP-LIST RKSKIJBPVAL NITROGEN CO2 -.0315000000BPVAL NITROGEN H2S .1696000000BPVAL NITROGEN METHANE .0278000000BPVAL NITROGEN ETHANE .0407000000BPVAL NITROGEN PROPANE .0763000000BPVAL NITROGEN ISOBU-01 .0944000000BPVAL NITROGEN N-BUT-01 .0700000000BPVAL NITROGEN 2-MET-01 .0867000000BPVAL NITROGEN N-PEN-01 .0878000000BPVAL NITROGEN N-HEX-01 .1496000000BPVAL NITROGEN N-HEP-01 .1422000000BPVAL NITROGEN N-OCT-01 -.4000000000BPVAL CO2 H2S .0989000000BPVAL CO2 METHANE .0933000000BPVAL CO2 ETHANE .1363000000BPVAL CO2 PROPANE .1289000000BPVAL CO2 ISOBU-01 .1285000000BPVAL CO2 N-BUT-01 .1430000000BPVAL CO2 2-MET-01 .1307000000BPVAL CO2 N-PEN-01 .1311000000BPVAL CO2 N-HEX-01 .1178000000BPVAL CO2 N-HEP-01 .1100000000BPVAL CO2 NITROGEN -.0315000000BPVAL H2S CO2 .0989000000BPVAL H2S ETHANE .0852000000BPVAL H2S PROPANE .0885000000BPVAL H2S ISOBU-01 .0511000000BPVAL H2S N-PEN-01 .0689000000BPVAL H2S NITROGEN .1696000000BPVAL METHANE CO2 .0933000000BPVAL METHANE ETHANE -7.8000000E-3BPVAL METHANE PROPANE 9.00000000E-3BPVAL METHANE ISOBU-01 .0241000000BPVAL METHANE N-BUT-01 5.60000000E-3BPVAL METHANE 2-MET-01 -7.8000000E-3BPVAL METHANE N-PEN-01 .0190000000BPVAL METHANE N-HEX-01 .0374000000BPVAL METHANE N-HEP-01 .0307000000BPVAL METHANE N-OCT-01 .0448000000BPVAL METHANE NITROGEN .0278000000BPVAL METHANE N-NON-01 .0448000000BPVAL ETHANE CO2 .1363000000BPVAL ETHANE H2S .0852000000BPVAL ETHANE METHANE -7.8000000E-3BPVAL ETHANE PROPANE -2.2000000E-3BPVAL ETHANE ISOBU-01 -.0100000000BPVAL ETHANE N-BUT-01 6.70000000E-3


– 25 –

BPVAL ETHANE N-PEN-01 5.60000000E-3BPVAL ETHANE N-HEX-01 -.0156000000BPVAL ETHANE N-HEP-01 4.10000000E-3BPVAL ETHANE N-OCT-01 .0170000000BPVAL ETHANE NITROGEN .0407000000BPVAL PROPANE CO2 .1289000000BPVAL PROPANE H2S .0885000000BPVAL PROPANE METHANE 9.00000000E-3BPVAL PROPANE ETHANE -2.2000000E-3BPVAL PROPANE ISOBU-01 -.0100000000BPVAL PROPANE N-BUT-01 0.0BPVAL PROPANE 2-MET-01 7.80000000E-3BPVAL PROPANE N-PEN-01 .0233000000BPVAL PROPANE N-HEX-01 -2.2000000E-3BPVAL PROPANE N-HEP-01 4.40000000E-3BPVAL PROPANE NITROGEN .0763000000BPVAL ISOBU-01 CO2 .1285000000BPVAL ISOBU-01 H2S .0511000000BPVAL ISOBU-01 METHANE .0241000000BPVAL ISOBU-01 ETHANE -.0100000000BPVAL ISOBU-01 PROPANE -.0100000000BPVAL ISOBU-01 N-BUT-01 1.10000000E-3BPVAL ISOBU-01 NITROGEN .0944000000BPVAL N-BUT-01 CO2 .1430000000BPVAL N-BUT-01 METHANE 5.60000000E-3BPVAL N-BUT-01 ETHANE 6.70000000E-3BPVAL N-BUT-01 PROPANE 0.0BPVAL N-BUT-01 ISOBU-01 1.10000000E-3BPVAL N-BUT-01 N-PEN-01 .0204000000BPVAL N-BUT-01 N-HEX-01 -.0111000000BPVAL N-BUT-01 N-HEP-01 -4.0000000E-4BPVAL N-BUT-01 NITROGEN .0700000000BPVAL 2-MET-01 CO2 .1307000000BPVAL 2-MET-01 METHANE -7.8000000E-3BPVAL 2-MET-01 PROPANE 7.80000000E-3BPVAL 2-MET-01 N-PEN-01 0.0BPVAL 2-MET-01 NITROGEN .0867000000BPVAL N-PEN-01 CO2 .1311000000BPVAL N-PEN-01 H2S .0689000000BPVAL N-PEN-01 METHANE .0190000000BPVAL N-PEN-01 ETHANE 5.60000000E-3BPVAL N-PEN-01 PROPANE .0233000000BPVAL N-PEN-01 N-BUT-01 .0204000000BPVAL N-PEN-01 2-MET-01 0.0BPVAL N-PEN-01 N-HEP-01 1.90000000E-3BPVAL N-PEN-01 N-OCT-01 -2.2000000E-3BPVAL N-PEN-01 NITROGEN .0878000000BPVAL N-HEX-01 CO2 .1178000000BPVAL N-HEX-01 METHANE .0374000000BPVAL N-HEX-01 ETHANE -.0156000000BPVAL N-HEX-01 PROPANE -2.2000000E-3BPVAL N-HEX-01 N-BUT-01 -.0111000000BPVAL N-HEX-01 N-HEP-01 -1.1000000E-3BPVAL N-HEX-01 NITROGEN .1496000000BPVAL N-HEP-01 CO2 .1100000000BPVAL N-HEP-01 METHANE .0307000000BPVAL N-HEP-01 ETHANE 4.10000000E-3BPVAL N-HEP-01 PROPANE 4.40000000E-3BPVAL N-HEP-01 N-BUT-01 -4.0000000E-4BPVAL N-HEP-01 N-PEN-01 1.90000000E-3BPVAL N-HEP-01 N-HEX-01 -1.1000000E-3BPVAL N-HEP-01 NITROGEN .1422000000BPVAL N-OCT-01 METHANE .0448000000BPVAL N-OCT-01 ETHANE .0170000000BPVAL N-OCT-01 N-PEN-01 -2.2000000E-3


– 26 –

BPVAL N-OCT-01 NITROGEN -.4000000000BPVAL N-NON-01 METHANE .0448000000

STREAM FEEDSUBSTREAM MIXED TEMP=120. PRES=284.7MOLE-FLOW NITROGEN 358.2 / CO2 4965.6 / H2S 339.4 / &

METHANE 2995.5 / ETHANE 2395.5 / PROPANE 2291. / &ISOBU-01 604.1 / N-BUT-01 1539.9 / 2-MET-01 790.4 / &N-PEN-01 1129.9 / N-HEX-01 1764.7 / N-HEP-01 2606.7 / &N-OCT-01 1844.5 / N-NON-01 1669. / N-DEC-01 831.7 / &N-DOD-01 1214.5

BLOCK F1 FLASH2PARAM TEMP=100. PRES=814.7




Calculation Sequence

SEQUENCE USED WAS:$OLVER01 F2 F1 F3 F4(RETURN $OLVER01)

Stream Variables FEED L1 L2 L3 L4----------------STREAM ID FEED L1 L2 L3 L4FROM : ---- F1 F2 F3 F4TO : F2 F2 F3 F4 ----

SUBSTREAM: MIXEDPHASE: MIXED LIQUID LIQUID LIQUID LIQUIDCOMPONENTS: LBMOL/HR

NITROGEN 358.2000 7.2105 22.8707 0.4965 1.7507-02CO2 4965.6000 332.2386 1913.4766 309.4625 74.1176H2S 339.4000 36.5041 290.1682 110.4444 52.4278METHANE 2995.5000 116.1405 445.3504 24.4871 2.1453ETHANE 2395.5000 237.2793 1510.5860 404.8408 145.5180PROPANE 2291.0000 275.7346 2608.0792 1543.6508 1020.4873ISOBU-01 604.1000 53.7814 701.2211 556.9299 461.9468N-BUT-01 1539.9000 114.5864 1742.7375 1472.3644 1284.45812-MET-01 790.4000 37.2868 845.8587 785.7948 741.2558N-PEN-01 1129.9000 44.8785 1191.6967 1125.5810 1077.0711N-HEX-01 1764.7000 35.8039 1803.2644 1769.6980 1745.8170N-HEP-01 2606.7000 24.9910 2628.7094 2611.1753 2599.6604N-OCT-01 1844.5000 7.6824 1850.3056 1846.0705 1843.5053N-NON-01 1669.0000 2.9719 1670.9576 1669.5788 1668.8073N-DEC-01 831.7000 0.6467 832.0568 831.8028 831.6730N-DOD-01 1214.5000 0.1750 1214.5759 1214.5223 1214.4983

TOTAL FLOW:LBMOL/HR 2.7341+04 1327.9123 2.1272+04 1.6277+04 1.4763+04LB/HR 1.8877+06 5.9910+04 1.7211+06 1.5183+06 1.4479+06CUFT/HR 2.1582+05 1766.0410 4.4062+04 3.7357+04 3.4976+04


ENTHALPY:


– 27 –

BTU/LBMOL -9.0812+04 -8.1807+04 -9.0021+04 -9.2361+04 -9.5063+04BTU/LB -1315.3024 -1813.2724 -1112.5881 -990.1566 -969.2754BTU/HR -2.4829+09 -1.0863+08 -1.9149+09 -1.5033+09 -1.4035+09


DENSITY:LBMOL/CUFT 0.1266 0.7519 0.4827 0.4357 0.4221LB/CUFT 8.7464 33.9231 39.0618 40.6431 41.3986

AVG MW 69.0427 45.1156 80.9113 93.2790 98.0761

V1 V2 V3 V4-----------STREAM ID V1 V2 V3 V4FROM : F1 F2 F3 F4TO : ---- F1 F2 F3

SUBSTREAM: MIXEDPHASE: VAPOR VAPOR VAPOR VAPORCOMPONENTS: LBMOL/HR

NITROGEN 358.1823 365.3929 22.8531 0.4790CO2 4891.4779 5223.7206 1839.3587 235.3453H2S 286.9707 323.4754 237.7394 58.0165METHANE 2993.3523 3109.4945 443.2043 22.3418ETHANE 2249.9775 2487.2597 1365.0663 259.3229PROPANE 1270.4888 1546.2281 1587.5726 523.1608ISOBU-01 142.1566 195.9392 239.2790 94.9836N-BUT-01 255.4380 370.0255 458.2766 187.90592-MET-01 49.1434 86.4305 104.6024 44.5389N-PEN-01 52.8281 97.7067 114.6249 48.5097N-HEX-01 18.8826 54.6866 57.4472 23.8809N-HEP-01 7.0393 32.0304 29.0488 11.5148N-OCT-01 0.9946 8.6771 6.8003 2.5651N-NON-01 0.1926 3.1645 2.1503 0.7715N-DEC-01 2.6929-02 0.6736 0.3837 0.1297N-DOD-01 1.6948-03 0.1767 7.7688-02 2.4046-02

TOTAL FLOW:LBMOL/HR 1.2577+04 1.3905+04 6508.4859 1513.4910LB/HR 4.3973+05 4.9964+05 2.7320+05 7.0356+04CUFT/HR 6.5192+04 2.7614+05 5.8513+05 3.1096+05

STATE VARIABLES:TEMP F 100.0000 120.0000 96.0000 85.0000PRES PSI 814.7000 284.7000 63.7000 27.7000VFRAC 1.0000 1.0000 1.0000 1.0000LFRAC 0.0 0.0 0.0 0.0SFRAC 0.0 0.0 0.0 0.0

ENTHALPY:BTU/LBMOL -8.8006+04 -8.5897+04 -7.7953+04 -6.5079+04BTU/LB -2517.1525 -2390.5307 -1857.0901 -1399.9728BTU/HR -1.1069+09 -1.1944+09 -5.0736+08 -9.8497+07

ENTROPY:BTU/LBMOL-R -27.9154 -26.5798 -39.3918 -53.5736BTU/LB-R -0.7984 -0.7397 -0.9384 -1.1524

DENSITY:LBMOL/CUFT 0.1929 5.0355-02 1.1123-02 4.8671-03LB/CUFT 6.7451 1.8093 0.4669 0.2262

AVG MW 34.9626 35.9322 41.9759 46.4861


– 28 –

Thermodynamics

HYSYS.Plant The materials that support a course in thermodynamics have not yet been class-tested. However, it is recommended that thermodynamics instructors consider allotting three hours of computer laboratory time for the exercises. A self-paced approach using the multimedia allows the students to bring themselves “up-to-speed” on the selection of property prediction methods, and their applications in VLE calculations, and to perform chemical equilibrium calculations. The following sequence of modules is recommended: Session 1: Under HYSYS – Physical Property Estimation – Package selection, students are

provided with a guide to the correct selection of physical property methods, and their impact on VLE calculations. It is recommended that students be assigned an exercise that allows them to test the recommendations, which are implemented as decision-trees (e.g., Exercise B.2).

Session 2: Under HYSYS – Separators, the main menu refers to item 1, Flash. Students

should review the background material on K-value computations for VLE computations and see the video of an industrial flash vessel. They will also find helpful the section on the use of the HYSYS Separator, modeling the flash unit.


– 29 –

Session 3: Under HYSYS – Chemical Reactors, the main menu refers to item 3, Setting up Reactors. Students can review the modules on the Equilibrium Reactor, for calculations involving the mass-action equations, and on the Gibbs Reactor for calculations involving the direct minimization of the Gibbs free energy.

To reinforce their acquired capabilities, students should be assigned a homework exercise. Three typical exercises are provided:

Exercise B.1 Refrigerator Design Problem

Exercise B.2 VLLE Problem

Exercise B.4 Chemical Equilibrium Problem


– 30 –

ASPEN PLUS The materials that support a course in thermodynamics have not yet been class-tested. However, it is recommended that thermodynamics instructors consider allotting four hours of computer laboratory time for the exercises. A self-paced approach using the multimedia allows the students to bring themselves “up-to-speed” on the use of a process simulator to carry out the energy balances in a refrigerator, to perform VLE calculations, and to perform chemical equilibrium calculations. The following sequence of modules is recommended: Session 1: Under ASPEN – Pumps & Compressors, the main menu refers to item 2,

Compressors and Expanders. Students should see the video of an industrial compressor and review the module on ASPEN PLUS (COMPR, MCOMPR). Then, under ASPEN PLUS – Heat Exchangers, the main menu refers to item 2, Heat Requirement Models. Students should review this module. For the refrigerator process, the multimedia doesn’t have a module on valves. Students can use the ASPEN PLUS VALVE subroutine with little preparation.

Session 2: Under ASPEN – Separators, the main menu refers to item 3, Phase Equil. and

Flash. Students should see the video of an industrial flash vessel and review the two modules on FLASH 2 and FLASH 3.

In addition, under Physical Property Estimation, the main menu refers to item 3, Property Estimation. Students can review the basis for VLE calculations in module on Phase Equilibria, methods for using ASPEN PLUS to draw equilibrium


– 31 –

diagrams in the modules on Binary Phase Diagrams and Phase Envelopes, and methods for regressing VLE data in the module Property Data Regression.

Session 3: Under ASPEN – Reactors, the main menu refers to item 3, Equilibrium Reactors.

Students can review the modules on the Equilibrium Reactor (REQUIL), for calculations involving the mass-action equations, and on the Gibbs Reactor (RGIBBS) for calculations involving the direct minimization of the Gibbs free energy.

To reinforce their acquired capabilities, students should be assigned a homework exercise. Five typical exercises are provided:



Exercise B.3 VLE Data Regression Problem


Exercise B.5 Selection of an Environmentally-friendly Refrigerant


– 32 –


This is extension of Example 6.2 in Seider, Seader, and Lewin (1999), which involves a refrigeration loop:

In this problem, it is desired to: a. simulate the refrigeration cycle assuming that the compressor has an isentropic efficiency of

0.9. For the evaporator and condenser, do not simulate the heat exchangers. Instead, use models that compute the “heat required” to be absorbed by the evaporating propane and to be removed from the condensing propane. Use the Soave-Redlich-Kwong equation and a propane flow rate of 5,400 lb/hr. Set the pressure levels as indicated above, but recognize that the temperatures may differ due to the VLE model.

b. calculate the lost work and the thermodynamic efficiency for the refrigeration cycle.

HYSYS.Plant Solution ASPEN PLUS Solution


– 33 –


An equimolar stream of benzene, toluene, and water at 150 kgmole/hr, 100°C, and 7 bar enters a flash vessel. It is expanded to 0.5 bar and cooled to 60°C. Use a process simulator with the UNIFAC method, having liquid-liquid interaction coefficients, for estimating liquid-phase activity coefficients to compute the flow rates and compositions of the three product streams. Also, determine the heat added or removed. If using ASPEN PLUS, the FLASH3 subroutine and the UNIF-LL property option are appropriate. If using HYSYS.Plant, use the 3-phase Separator, and select the appropriate physical property method as guided by the multimedia.



– 34 –

Exercise B.3 VLE Data Regression Problem

The following vapor-liquid equilibrium data for ethanol and benzene at 1 atm have been taken from the Gmehling and Onken data bank: x y T,°C

0 0 80.13 0.025 0.1303 76.29

0.05 0.2117 73.77 0.075 0.2654 72.09

0.1 0.3029 70.94 0.125 0.3304 70.12

0.15 0.3514 69.53 0.175 0.3681 69.08

0.2 0.3818 68.75 0.225 0.3933 68.49

0.25 0.4033 68.28 0.275 0.4121 68.12

0.3 0.4201 68.00 0.325 0.4274 67.90

0.35 0.4343 67.82 0.375 0.4408 67.76

0.4 0.4472 67.72 0.425 0.4534 67.69

0.45 0.4596 67.68 0.475 0.4659 67.68

0.5 0.4724 67.69 0.525 0.4791 67.72

0.55 0.4860 67.77 0.575 0.4935 67.82

0.6 0.5015 67.90 0.625 0.5101 68.00

0.65 0.5195 68.13 0.675 0.5298 68.28

0.7 0.5413 68.47 0.725 0.5542 68.69

0.75 0.5689 68.97 0.775 0.5856 69.30

0.8 0.6049 69.70 0.825 0.6273 70.19

0.85 0.6539 70.78 0.875 0.6855 71.49

0.9 0.7238 72.36 0.925 0.7707 73.41

0.95 0.8293 74.72 0.975 0.9036 76.32

1 1 78.31


– 35 –

For the design of a distillation column to produce nearly pure ethanol, it is desired to obtain a close match between the computed VLE and the Gmehling and Onken data. a. Use the binary interaction coefficients for the UNIQUAC equation for liquid-phase

interaction coefficients, in the data bank of a process simulator, to prepare T-x-y and x-y diagrams.

b. Use data points having ethanol mole fractions above its azeotropic mole fraction with a

regression program in a process simulator. Determine interaction coefficients that give better agreement with the Gmehling and Onken data at high ethanol concentrations. Show how the T-x-y and x-y diagrams compare using these data points.

ASPEN PLUS Solution


An equimolar stream of ammonia, oxygen, nitrogen oxide (NO), nitrogen dioxide (NO2), and water at 100 lbmole/hr, 300°F, and 1 atm enters a tank reactor. Determine the flow rate and composition of the reactor effluent, assuming that chemical equilibrium is attained. Use a process simulator, assuming that the ideal gas law applies. a. Determine the number of independent reactions. Then, determine a set of independent

reactions. b. Obtain chemical equilibrium by solving the mass-action equations (using K-values). If

using ASPEN PLUS, the REQUIL subroutine is appropriate. c. Obtain chemical equilibrium by minimizing the Gibbs free energy. Note that it is not

necessary to specify an independent reaction set. If using ASPEN PLUS, the RGIBBS subroutine is appropriate.

ASPEN PLUS Solution

Exercise B.5 Selection of an Environmentally-friendly Refrigerant

It is desired to find a refrigerant that removes heat at -20°C and rejects heat at 32°C. Desirable refrigerants should have Ps{-20°C} > 1.4 bar, Ps{32°C} < 14 bar, ∆Hv{-20°C} > 18.4 kJ/mol, and cpl{6°C} > 18.4 kJ/mol. For the candidate groups, CH3, CH, F, and S, formulate a mixed-integer nonlinear program and use GAMS to solve it. Hint: maximize the objective function, ∆Hv{-20°C}.


– 36 –

Exercise B.1 Solution using HYSYS.Plant

Refrigerator Design Problem Solution

a. Solution using HYSYS.Plant. This solution can be reproduced using the file, REFRIG.HSC.

HYSYS.Plant Report.

Fluid Package: Basis-1 Property Package: SRK Material Stream: S-1 Overall Vapour Phase Liquid Phase Vapour / Phase Fraction 1 1 0Temperature: (F) 8.44E-02 8.44E-02 8.44E-02Pressure: (psia) 38.37 38.37 38.37Molar Flow (lbmole/hr) 122.5 122.5 0Mass Flow (lb/hr) 5400 5400 0Liquid Volume Flow (barrel/day) 729.8 729.8 0Molar Enthalpy (Btu/lbmole) -4.61E+04 -4.61E+04 -5.38E+04Molar Entropy (Btu/lbmole-F) 33.92 33.92 17.21Heat Flow (Btu/hr) -5.65E+06 -5.65E+06 0 Material Stream: S-2 Overall Vapour Phase Vapour / Phase Fraction 1 1 Temperature: (F) 118.7 118.7 Pressure: (psia) 187 187 Molar Flow (lbmole/hr) 122.5 122.5 Mass Flow (lb/hr) 5400 5400 Liquid Volume Flow (barrel/day) 729.8 729.8 Molar Enthalpy (Btu/lbmole) -4.45E+04 -4.45E+04 Molar Entropy (Btu/lbmole-F) 34.23 34.23 Heat Flow (Btu/hr) -5.45E+06 -5.45E+06 Material Stream: S-3 Overall Liquid Phase Vapour Phase Vapour / Phase Fraction 0 1 0


– 37 –

Temperature: (F) 97.52 97.52 97.52Pressure: (psia) 185 185 185Molar Flow (lbmole/hr) 122.5 122.5 0Mass Flow (lb/hr) 5400 5400 0Liquid Volume Flow (barrel/day) 729.8 729.8 0Molar Enthalpy (Btu/lbmole) -5.10E+04 -5.10E+04 -4.50E+04Molar Entropy (Btu/lbmole-F) 22.65 22.65 33.46Heat Flow (Btu/hr) -6.25E+06 -6.25E+06 0 Material Stream: S-4 Overall Vapour Phase Liquid Phase Vapour / Phase Fraction 0.3596 0.3596 0.6404Temperature: (F) 2.193 2.193 2.193Pressure: (psia) 40 40 40Molar Flow (lbmole/hr) 122.5 44.03 78.42Mass Flow (lb/hr) 5400 1942 3458Liquid Volume Flow (barrel/day) 729.8 262.4 467.3Molar Enthalpy (Btu/lbmole) -5.10E+04 -4.61E+04 -5.38E+04Molar Entropy (Btu/lbmole-F) 23.29 33.9 17.33Heat Flow (Btu/hr) -6.25E+06 -2.03E+06 -4.22E+06 Cooler: E-100 Pressure Drop: 2.000 psi Duty: 7.920e+005 Btu/hr Volume: 3.531 ft3 Heater: E-101 PARAMETERS Pressure Drop: 1.630 psi Duty: 5.970e+005 Btu/hr Volume: 3.531 ft3 Compressor: K-100 Duty: 1.9503e+05 Btu/hr Adiabatic Eff.: 89.00 PolyTropic Eff.: 90.21 Speed: Adiabatic Head: 2.501e+004 ft Polytropic Head: 2.535e+004 ft Polytropic Exp. 1.063 Isentropic Exp. 1.044 Poly Head Factor 1.015 User Variables Valve: VLV-100 Pressure Drop: 145.0 psi b. Lost work (see Eq. (6.23), Seider, Seader, Lewin (1999)):

EvapEvaporator

in QT

TWLW

−+= 01

= 70 kW + (1 – 537/470)×176.3 kW = 70 – 25.1 = 44.9 kW Thermodynamic efficiency (see Eq. (6.27), Seider, Seader, Lewin (1999)):

LWgoalmain

goalmaingoal −

=−)(η 359.09.441.25

1.25=

−−−

=

See SSL for calculations of the lost work in each process unit. Also, see Example 6.3 in which the valve is replaced by a power recovery turbine.


– 38 –

Exercise B.1 Solution using ASPEN.PLUS

a. Solution using ASPEN PLUS. This solution can be reproduced using the file,

REFRIG.BKP.

EVAP1COND1

C1

V1

S1

S2

S3S4

ASPEN PLUS Program

TITLE 'PROPANE REFRIGERATION LOOP'IN-UNITS ENGDEF-STREAMS CONVEN ALLDESCRIPTION "

General Simulation with English Units :F, psi, lb/hr, lbmol/hr, Btu/hr, cuft/hr.Property Method: NoneFlow basis for input: MoleStream report composition: Mole flow"



PROPANE C3H8FLOWSHEET

BLOCK EVAP1 IN=S4 OUT=S1BLOCK COND1 IN=S2 OUT=S3BLOCK C1 IN=S1 OUT=S2BLOCK V1 IN=S3 OUT=S4

PROPERTIES RK-SOAVESTREAM S3

SUBSTREAM MIXED PRES=185. VFRAC=0. MASS-FLOW=5400.MOLE-FRAC PROPANE 1.

BLOCK COND1 HEATERPARAM PRES=185. VFRAC=0.

BLOCK EVAP1 HEATERPARAM PRES=38.37 VFRAC=1.

BLOCK C1 COMPRPARAM TYPE=ISENTROPIC PRES=187. SEFF=0.9

BLOCK V1 VALVEPARAM P-OUT=40.

EO-CONV-OPTISTREAM-REPOR MOLEFLOW

Stream Variables S1 S2 S3 S4-----------


– 39 –

STREAM ID S1 S2 S3 S4FROM : EVAP1 C1 COND1 V1TO : C1 COND1 V1 EVAP1

MAX CONV. ERROR: 0.0 0.0 -8.8208-08 0.0SUBSTREAM: MIXEDPHASE: VAPOR VAPOR LIQUID MIXEDCOMPONENTS: LBMOL/HR

PROPANE 122.4586 122.4586 122.4586 122.4586TOTAL FLOW:

LBMOL/HR 122.4586 122.4586 122.4586 122.4586LB/HR 5400.0000 5400.0000 5400.0000 5400.0000CUFT/HR 1.4709+04 3328.3100 182.1782 5122.5994


ENTHALPY:BTU/LBMOL -4.6438+04 -4.4857+04 -5.1349+04 -5.1349+04BTU/LB -1053.0957 -1017.2552 -1164.4737 -1164.4737BTU/HR -5.6867+06 -5.4932+06 -6.2882+06 -6.2882+06


DENSITY:LBMOL/CUFT 8.3256-03 3.6793-02 0.6722 2.3906-02LB/CUFT 0.3671 1.6224 29.6413 1.0542

AVG MW 44.0965 44.0965 44.0965 44.0965

Selected Process Unit Output BLOCK: C1 MODEL: COMPR-----------------------------

*** RESULTS ***

INDICATED HORSEPOWER REQUIREMENT HP 76.0637BRAKE HORSEPOWER REQUIREMENT HP 76.0637NET WORK REQUIRED HP 76.0637ISENTROPIC HORSEPOWER REQUIREMENT HP 68.4573CALCULATED OUTLET TEMP F 120.174ISENTROPIC TEMPERATURE F 112.749EFFICIENCY (POLYTR/ISENTR) USED 0.90000HEAD DEVELOPED, FT-LBF/LB 25,101.0MECHANICAL EFFICIENCY USED 1.00000INLET HEAT CAPACITY RATIO 1.14081INLET VOLUMETRIC FLOW RATE , CUFT/HR 14,708.6OUTLET VOLUMETRIC FLOW RATE, CUFT/HR 3,328.31INLET COMPRESSIBILITY FACTOR 0.93399OUTLET COMPRESSIBILITY FACTOR 0.81679AV. ISENT. VOL. EXPONENT 1.04889AV. ISENT. TEMP EXPONENT 1.16052AV. ACTUAL VOL. EXPONENT 1.06586AV. ACTUAL TEMP EXPONENT 1.17158


– 40 –

BLOCK: COND1 MODEL: HEATER------------------------------

*** RESULTS ***OUTLET TEMPERATURE F 97.564OUTLET PRESSURE PSI 185.00HEAT DUTY BTU/HR -0.79498E+06

BLOCK: EVAP1 MODEL: HEATER------------------------------

*** RESULTS ***OUTLET TEMPERATURE F 0.13477OUTLET PRESSURE PSI 38.370HEAT DUTY BTU/HR 0.60144E+06

BLOCK: V1 MODEL: VALVE-----------------------------

*** RESULTS ***

VALVE PRESSURE DROP PSI 145.000

b. Lost work (see Eq. (6.23), Seider, Seader, Lewin (1999)):

EvapEvaporator

in QT

TWLW

−+= 01

= 70 kW + (1 – 537/470)×176.3 kW = 70 – 25.1 = 44.9 kW Thermodynamic efficiency (see Eq. (6.27), Seider, Seader, Lewin (1999)):

LWgoalmain

goalmaingoal −

=−)(η

359.09.441.25

1.25=

−−−

=

See SSL for calculations of the lost work in each process unit. Also, see Example 6.3 in which the valve is replaced by a power recovery turbine.


– 41 –

Exercise B.2 Solution using HYSYS.Plant

Solution using 3-phase Separator in HYSYS.Plant. This solution can be reproduced using the file, VLLE.HSC. Note that the physical properties are predicted using the NRTL activity method, with UNIFAC-LL binary interaction coefficients, and assuming ideal vapor, as recommended by both Eric Carlson and Bob Seader (Both indicate that the UNIFAC LL estimation method is appropriate). The option to check for the possibility of two liquid phases should be activated.

NAME FEED VAP LIQ1 LIQ2 SEP-DUTY Vapor Fraction 0 1 0 0 Temperature [C] 100 60 60 60 Pressure [bar] 7 0.5 0.5 0.5 Molar Flow [kgmol/h] 150 106.929 35.82939 7.241573 Mass Flow [kgl/h] 9413.295 6158.99 3123.628 130.6777 Liquid Volume Flow [m3/h] 10.6248 6.918751 3.575073 0.13098 Heat Flow [kcal/h] -2318423 -1321315 249418 -488242 758284.7 Molar Enthalpy [kcal/kgmol] -15456.2 -12356.9 6961.269 -67422 Comp Molar Flow (Benzene) [kgmol/h] 50 38.05983 11.93832 1.85E-03 Comp Molar Flow (Toluene) [kgmol/h] 50 26.2453 23.75324 1.47E-03 Comp Molar Flow (Water) [kgmol/h] 50 42.62391 0.137836 7.238254

In the above table, values in blue are the process specifications, with the remaining values being computed results. Note that the organic liquid product is LIQ1 and the aqueous liquid product is LIQ2. To satisfy the energy balance, HYSYS.Plant computes 0.758 MMKcal/hr are added to the flash vessel.


– 42 –


Solution using the FLASH3 subroutine in ASPEN PLUS. This solution can be reproduced using the file, VLLE.BKP.

FEED

VAP

LIQ1

LIQ2

F1

ASPEN PLUS Program

TITLE 'VLLE - BENZENE, TOLUENE, WATER'

IN-UNITS MET VOLUME-FLOW='cum/hr' ENTHALPY-FLO='MMkcal/hr' &HEAT-TRANS-C='kcal/hr-sqm-K' PRESSURE=bar TEMPERATURE=C &VOLUME=cum DELTA-T=C HEAD=meter MOLE-DENSITY='kmol/cum' &MASS-DENSITY='kg/cum' MOLE-ENTHALP='kcal/mol' &MASS-ENTHALP='kcal/kg' HEAT=MMkcal MOLE-CONC='mol/l' &PDROP=bar

DEF-STREAMS CONVEN ALLSIM-OPTIONS NPHASE=3DESCRIPTION "

General Simulation with Metric Units :C, bar, kg/hr, kmol/hr, MMKcal/hr, cum/hr.Property Method: NoneFlow basis for input: MoleStream report composition: Mole flow



BENZENE C6H6 /TOLUENE C7H8 /WATER H2O

FLOWSHEETBLOCK F1 IN=FEED OUT=VAP LIQ1 LIQ2

PROPERTIES UNIF-LLPROPERTIES IDEAL / UNIFAC

STREAM FEEDSUBSTREAM MIXED TEMP=100. PRES=7. MOLE-FLOW=150.MOLE-FLOW BENZENE 50. / TOLUENE 50. / WATER 50.


STREAM-REPOR MOLEFLOW


– 43 –

Stream Variables FEED LIQ1 LIQ2 VAP------------------STREAM ID FEED LIQ1 LIQ2 VAPFROM : ---- F1 F1 F1TO : F1 ---- ---- ----

SUBSTREAM: MIXEDPHASE: LIQUID LIQUID LIQUID VAPORCOMPONENTS: KMOL/HR

BENZENE 50.0000 14.3925 2.0372-03 35.6055TOLUENE 50.0000 26.3020 1.3751-03 23.6966WATER 50.0000 0.1748 10.4077 39.4175

TOTAL FLOW:KMOL/HR 150.0000 40.8693 10.4111 98.7197KG/HR 9413.4720 3550.8775 187.7831 5674.8114CUM/HR 11.7432 4.2699 0.1958 5408.5900

STATE VARIABLES:TEMP C 100.0000 60.0000 60.0000 60.0000PRES BAR 7.0000 0.5000 0.5000 0.5000VFRAC 0.0 0.0 0.0 1.0000LFRAC 1.0000 1.0000 1.0000 0.0SFRAC 0.0 0.0 0.0 0.0

ENTHALPY:KCAL/MOL -15.5331 6.9826 -67.6121 -12.4644KCAL/KG -247.5143 80.3676 -3748.5570 -216.8315MMKCAL/HR -2.3300 0.2854 -0.7039 -1.2305

ENTROPY:CAL/MOL-K -52.4388 -68.6094 -36.9819 -26.1730CAL/GM-K -0.8356 -0.7897 -2.0504 -0.4553

DENSITY:KMOL/CUM 12.7734 9.5715 53.1678 1.8252-02KG/CUM 801.6136 831.6121 958.9778 1.0492

AVG MW 62.7565 86.8838 18.0368 57.4841

Note that the stream LIQ1 contains the organic phase and the stream LIQ2 contains the aqueous phase.

Selected Process Unit Output

BLOCK: F1 MODEL: FLASH3------------------------------

PROPERTY OPTION SET: UNIF-LL UNIFAC / REDLICH-KWONG

*** RESULTS ***OUTLET TEMPERATURE C 60.000OUTLET PRESSURE BAR 0.50000HEAT DUTY MMKCAL/HR 0.68096VAPOR FRACTION 0.658131ST LIQUID/TOTAL LIQUID 0.79698

V-L1-L2 PHASE EQUILIBRIUM :

COMP F(I) X1(I) X2(I) Y(I) K1(I) K2(I)BENZENE 0.333 0.352 0.196E-03 0.361 1.02 0.184E+04TOLUENE 0.333 0.644 0.132E-03 0.240 0.373 0.182E+04WATER 0.333 0.428E-02 1.00 0.399 93.4 0.399

To satisfy the energy balance, 0.681 MMKcal/hr are added to the flash vessel.


– 44 –


Solution obtained using ASPEN PLUS with the UNIQUAC method for estimating liquid-phase activity coefficients. Results can be reproduced using the file, VLEREG.BKP. a. From the ASPEN PLUS data banks, the following binary interaction

coefficients are used: aij = -0.464, aji = 0.4665, bij = 137.8, bji = -1,001.7

Using these interaction coefficients, T-x-y and x-y graphs are prepared.

b. Using the data points for ethanol concentrations greater than or equal to 0.6 from the Gmehling and Onken data bank, the binary interaction coefficients are adjusted by the ASPEN PLUS data regression program to:

aij = -0.464, aji = 0.4665, bij = 14.96, bji = -441.7

In this case, just small changes are observed in the T-x-y and x-y diagrams.


– 45 –

Exercise B.4 Solution using ASPEN PLUS

Chemical Equilibrium Problem Solution

a. NC = 5, R = rank of atom matrix = 3. Hence, NR = no. of independent chemical reactions = NC – R = 5 – 3 = 2. For the atom matrix, see the solution to part ‘c’.

b. Solution using the REQUIL subroutine in ASPEN PLUS. This solution can be

reproduced using the file, REQUIL.BKP.

FEED

VAP

LIQ

R1

Note that when using the REQUIL subroutine, streams for both vapor and liquid effluents must be defined, even when one doesn’t exist.

The two independent reactions are selected arbitrarily: NO + 1/2O2 = NO2 4NH3 + 5O2 = 4NO + 6H2O ASPEN PLUS Program

TITLE 'CHEMICAL EQUILIBRIUM - K-VALUES'IN-UNITS ENGDEF-STREAMS CONVEN ALLDATABANKS PURE10 / AQUEOUS / SOLIDS / INORGANIC / &

NOASPENPCDPROP-SOURCES PURE10 / AQUEOUS / SOLIDS / INORGANICCOMPONENTS

AMMON-01 H3N /OXYGE-01 O2 /NITRI-01 NO /NITRO-01 NO2 /WATER H2O

FLOWSHEETBLOCK R1 IN=FEED OUT=VAP LIQ

PROPERTIES IDEALSTREAM FEED

SUBSTREAM MIXED TEMP=300. PRES=1. <atm> MOLE-FLOW=100.MOLE-FRAC AMMON-01 0.2 / OXYGE-01 0.2 / NITRI-01 0.2 / &

NITRO-01 0.2 / WATER 0.2BLOCK R1 REQUIL

PARAM NREAC=2 TEMP=300. PRES=1. <atm> NPHASE=2STOIC 1 NITRI-01 -1. * / OXYGE-01 -0.5 * / NITRO-01 1. &

*STOIC 2 AMMON-01 -4. * / OXYGE-01 -5. * / NITRI-01 4. &

* / WATER 6. *TAPP-SPEC 1 0.0 / 2 0.0



– 46 –

Stream Variables FEED LIQ VAP------------

STREAM ID FEED LIQ VAPFROM : ---- R1 R1TO : R1 ---- ----

SUBSTREAM: MIXEDPHASE: VAPOR MISSING VAPORCOMPONENTS: LBMOL/HR

AMMON-01 20.0000 0.0 0.0OXYGE-01 20.0000 0.0 1.5913-06NITRI-01 20.0000 0.0 50.0042NITRO-01 20.0000 0.0 10.0027WATER 20.0000 0.0 50.0042

TOTAL FLOW:LBMOL/HR 100.0000 0.0 110.0111LB/HR 2861.1264 0.0 2861.4532CUFT/HR 5.5473+04 0.0 6.1027+04

STATE VARIABLES:TEMP F 300.0000 MISSING 300.0000PRES PSI 14.6959 14.6959 14.6959VFRAC 1.0000 MISSING 1.0000LFRAC 0.0 MISSING 0.0SFRAC 0.0 MISSING 0.0

ENTHALPY:BTU/LBMOL -1.2315+04 MISSING -2.6587+04BTU/LB -430.4089 MISSING -1022.1591BTU/HR -1.2315+06 MISSING -2.9249+06

ENTROPY:BTU/LBMOL-R -3.1492 MISSING -0.2405BTU/LB-R -0.1101 MISSING -9.2445-03

DENSITY:LBMOL/CUFT 1.8027-03 MISSING 1.8027-03LB/CUFT 5.1577-02 MISSING 4.6888-02

AVG MW 28.6113 MISSING 26.0106


*** RESULTS ***OUTPUT TEMPERATURE F 300.00OUTPUT PRESSURE PSI 14.696HEAT DUTY BTU/HR -0.16934E+07VAPOR FRACTION 1.0000

REACTION EQUILIBRIUM CONSTANTS:

REACTION EQUILIBRIUMNUMBER CONSTANT

1 1663.32 0.99999+1003

c. Solution using the RGIBBS subroutine in ASPEN PLUS. This solution can be reproduced using the file, RGIBBS.BKP.


– 47 –

FEED VAP

LIQ

R1

Note that when using the REQUIL subroutine, streams for both vapor and liquid effluents must be defined, even when one doesn’t exist. ASPEN PLUS Program – only those paragraphs that differ from the program above are included.

TITLE 'CHEMICAL EQUILIBRIUM - MINIMIZATION OF G'

BLOCK R1 RGIBBSPARAM TEMP=300. PRES=1. <atm>

Stream Variables

FEED LIQ VAP------------STREAM ID FEED LIQ VAPFROM : ---- R1 R1TO : R1 ---- ----

SUBSTREAM: MIXEDPHASE: VAPOR MISSING VAPORCOMPONENTS: LBMOL/HR

AMMON-01 20.0000 0.0 0.0OXYGEN 20.0000 0.0 1.5905-06NITRO-01 20.0000 0.0 10.0000NITRI-01 20.0000 0.0 50.0000WATER 20.0000 0.0 50.0000

TOTAL FLOW:LBMOL/HR 100.0000 0.0 110.0000LB/HR 2861.1264 0.0 2861.1264CUFT/HR 5.5473+04 0.0 6.1021+04

STATE VARIABLES:TEMP F 300.0000 MISSING 300.0000PRES PSI 14.6959 MISSING 14.6959VFRAC 1.0000 MISSING 1.0000LFRAC 0.0 MISSING 0.0SFRAC 0.0 MISSING 0.0

ENTHALPY:BTU/LBMOL -1.2315+04 MISSING -2.6588+04BTU/LB -430.4089 MISSING -1022.2009BTU/HR -1.2315+06 MISSING -2.9246+06

ENTROPY:BTU/LBMOL-R -3.1492 MISSING -0.2403BTU/LB-R -0.1101 MISSING -9.2405-03

DENSITY:LBMOL/CUFT 1.8027-03 MISSING 1.8027-03LB/CUFT 5.1577-02 MISSING 4.6888-02

AVG MW 28.6113 MISSING 26.0102

Note that these results are nearly identical to those for part ‘a’. Tight convergence tolerances are satisfied by the RGIBBS subroutine, while small material balance differences between the inlet and outlet streams are reported by the REQUIL subroutine.


– 48 –


FLUID PHASE SPECIES IN PRODUCT LIST:AMMON-01 OXYGEN NITRO-01 NITRI-01 WATER

ATOM MATRIX:ELEMENT H N O

AMMON-01 3.00 1.00 0.00OXYGEN 0.00 0.00 2.00NITRO-01 0.00 1.00 2.00NITRI-01 0.00 1.00 1.00WATER 2.00 0.00 1.00

*** RESULTS ***TEMPERATURE F 300.00PRESSURE PSI 14.696HEAT DUTY BTU/HR -0.16932E+07VAPOR FRACTION 1.0000NUMBER OF FLUID PHASES 1

FLUID PHASE MOLE FRACTIONS:

PHASE VAPOROF TYPE VAPORPHASE FRACTION 1.000000PLACED IN STREAM VAP

AMMON-01 0.0000000E+00OXYGEN 0.1445920E-07NITRI-01 0.4545455WATER 0.4545454


– 49 –

Heat Transfer HYSYS.Plant

The materials supporting a course in heat transfer assume that two hours of computer

laboratory time is allocated to the exercises. The multimedia includes a section that provides a self-paced overview on heat transfer equipment in general and the models available in HYSYS.Plant in particular. The following sequence is suggested:

Session 1: In the first part of the exercise session, the student should review the entire section on HYSYS – Heat Exchangers in the multimedia. This consists of modules describing the simple heater/cooler and the more rigorous heat exchanger. The modules each illustrate the use of the models in example applications.

Session 2: The tutorial Toluene Manufacture should be reviewed, while at the same time, the

student should develop his/her version of the simulation using HYSYS.Plant.

To reinforce their acquired capabilities, students should be assigned a homework exercise. Two typical exercises are provided: (a) The rating of a 2-8 heat exchanger for process heat transfer; (b) Completing the Toluene Manufacture heat-integrated process to determine the optimum pre-heat temperature.


– 50 –

Heat Transfer ASPEN PLUS

The materials supporting a course in heat transfer assume that two hours of computer laboratory time is allocated to the exercises. The multimedia includes a section that provides a self-paced overview on heat transfer equipment in general and the models available in ASPEN PLUS in particular. The following sequence is suggested. Note that this sequence has not been class-tested using ASPEN PLUS. However, a similar sequence using HYSYS.Plant, on the previous page, has been class-tested successfully:

Session 1: In the first part of the exercise session, the student should review the first three sections on Heat Exchangers in the multimedia (1. Introduction with Videos, 2. Heat Requirement Modules, and 3. Shell-and-Tube Heat Exchangers.) These consist of modules describing the simple heater/cooler and the more rigorous heat exchanger. The modules each illustrate the use of the models in example applications. Note that videos are provided of industrial 1-2 shell-and-tube heat exchangers and fin-fan heat exchangers.

Session 2: The student should review the tutorial involving Toluene Manufacture, while at the

same time, develop his/her version of the simulation using ASPEN PLUS.

To reinforce their acquired capabilities, students should be assigned a homework exercise. Two typical exercises are provided: (a) The rating of a 2-8 heat exchanger for process heat transfer; (b) Completing the Toluene Manufacture heat-integrated process to determine the optimum pre-heat temperature.


– 51 –

Exercise C.1 Heat Exchanger Rating Problem

An existing 2-8 shell-and-tube heat exchanger is to be used to transfer heat to a toluene feed stream from a styrene product stream. The toluene enters the exchanger on the tube side at a flow rate of 125,000 lb/hr at 100oF and 90 psia. The styrene enters on the shell side at a flow rate of 150,000 lb/hr at 300oF and 50 psia. The exchanger shell and tubes are carbon steel. The shell has an inside diameter of 39 in. and contains 1,024 3/4-in., 14 BWG, 16-ft-long tubes on a 1-in. square pitch. Thirty-eight segmental baffles are used with a baffle cut of 25%. Shell inlet and outlet nozzles are 2.5-in., schedule 40 pipe, and tube-side inlet and outlet nozzles are 4-in., schedule 40 pipe. Fouling factors are estimated to be 0.002 (hr-ft2-oF)/Btu on each side. Determine the exit temperatures of the two streams, the heat duty, and the pressure drops. In ASPEN PLUS, use the HEATX subroutine, and in HYSYS.Plant, use Heat Exchanger. Note that this problem is solved in Example 8.7 of Seider, Seader, and Lewin (1999).


Exercise C.2 Heat Exchanger Design Problem

Complete the class exercise in which a heat integrated process was developed for the

manufacture of toluene from n-heptane. You are required to determine the optimum pre-heat temperature to minimize the annual cost, involving both the cost of the preheater and the energy costs associated with preheating the feed stream. The following data is provided:

U = 65 Btu/h ft2 °F (assumed constant) Cost of Super-heater Fuel = 0.02 $/Btu h-1 y-1 Bare Modules Cost (for kettle reboiler), in $:

[ ] [ ]{ }2exp 11.967 0.8709 ln( ) 0.09005 ln( )BC A A= − + ,

where A is the exchanger surface area in ft2. The annualized equipment cost, assuming 20% depreciation, is CA = 1.05×4.8×CB/5 It is suggested that you use the Spreadsheet to compute the annual costs based on the above data and the Databook to carry out a sensitivity analysis to show the effect of preheat temperature on annual cost. Your solution should include the following:

a) A plot showing the annual cost as a function of the super-heater feed temperature. What is the maximum possible temperature attainable?

b) A definition of the optimal value of the super-heater feed temperature, optimal pre-heater heat exchange area, and the corresponding annual cost.

c) Comparison of the optimal annual cost incurred with that of the cases where (a) no preheater installed; (b) a preheater is installed to bring the n-heptane to its dew point.



– 52 –

Exercise C.1 Solution using HYSYS.Plant

These results can be reproduced using the file HEATEX.hsc

The heat exchanger in HYSYS.Plant is used to make the calculations. In its rating mode,

it uses built-in correlations of the type described in Chapter 8 (Seider, Seader, and Lewin) for

estimating shell-side and tube-side heat-transfer coefficients and pressure drops. The following

results are obtained (both streams are liquid):

Toluene exit temperature = 252.6 oF

Styrene exit temperature = 179.3 oF

Tube-side pressure drop = 0.02 psi (this is well-below expected)

Toluene exit pressure = 89.98 psia

Shell-side pressure drop = 0.716 psia (this is well-below expected)

Styrene exit pressure = 54.28 psia

Heat-transfer area (tube outside) = Two shells, with 1,608 ft2 per shell.

Heat duty = 8.70×106 Btu/hr

Estimated shell-side film coefficient =110.3 Btu/hr-ft2-R

Estimated tube-side film coefficient = 393.7Btu/hr-ft2-R

Estimated overall heat transfer coefficient = 58.1 Btu/hr-ft2-R

Log-mean temperature difference based on countercurrent flow = 46.5 oF

Correction factor for 2-8 exchanger, FT = 0.750


– 53 –

Exercise C.1 Solution using ASPEN.PLUS

The HEATX subroutine (block) of the ASPEN PLUS simulator is used to make the

calculations. It has built-in correlations of the type described in Chapter 8 (Seider, Seader, and

Lewin) for estimating shell-side and tube-side heat-transfer coefficients and pressure drops. The

following results are obtained (both streams are liquid):

Toluene exit temperature = 255.0oF

Styrene exit temperature = 178.1oF

Tube-side tube pressure drop = 3.59 psi

Tube-side nozzle pressure drop = 0.55 psi

Toluene exit pressure = 85.86 psia

Shell-side baffled pressure drop = 4.55 psia

Shell-side nozzle pressure drop = 5.18 psia

Styrene exit pressure = 40.28 psia

Heat-transfer area (tube outside) = 3,217 ft2

Heat duty = 8,625,200 Btu/hr

Estimated (Uo) clean = 90.4 Btu/hr-ft2-R

Estimated (Uo ) dirty = 64.0 Btu/hr-ft2-R

Log-mean temperature difference based on countercurrent flow = 41.9oF

Correction factor for 2-8 exchanger, FT = 0.712

Velocity in the tubes = 3.02 ft/s

Maximum Reynolds number in the tubes = 45,700

Crossflow velocity in the shell = 2.59 ft/s

Maximum crossflow Reynolds number in the shell = 50,300

Flow regime on tube and shell sides = turbulent

ASPEN PLUS Program

TITLE 'HEAT EXCHANGER DESIGN - EXAMPLE 13.7 (OLD 8.7)'

IN-UNITS ENG

DEF-STREAMS CONVEN ALL

DESCRIPTION "

General Simulation with English Units :

F, psi, lb/hr, lbmol/hr, Btu/hr, cuft/hr.

Property Method: None

Flow basis for input: Mole


– 54 –

Stream report composition: Mole flow

DATABANKS PURE11 / AQUEOUS / SOLIDS / INORGANIC / &

NOASPENPCD

PROP-SOURCES PURE11 / AQUEOUS / SOLIDS / INORGANIC

COMPONENTS

TOLUENE C7H8 /

STYRENE C8H8

FLOWSHEET

BLOCK H1 IN=HOTIN COLDIN OUT=HOTOUT COLDOUT

PROPERTIES RK-SOAVE

PROPERTIES BWR-LS / BWRS / CHAO-SEA / IDEAL / LK-PLOCK /

PENG-ROB

STREAM COLDIN

SUBSTREAM MIXED TEMP=100. PRES=90. MASS-FLOW=125000. &

FREE-WATER=NO NPHASE=2 PHASE=V

MOLE-FRAC TOLUENE 1. / STYRENE 0.

STREAM HOTIN

SUBSTREAM MIXED TEMP=300. PRES=50. MASS-FLOW=150000.

MOLE-FRAC TOLUENE 0. / STYRENE 1.

BLOCK H1 HEATX

PARAM CALC-TYPE=SIMULATION AREA=3217. TYPE=COUNTERCURRE &

NPOINTS=5 P-UPDATE=YES U-OPTION=FILM-COEF &

F-OPTION=GEOMETRY CALC-METHOD=DETAILED FC-USE-AVTD=YES

FEEDS HOT=HOTIN COLD=COLDIN

PRODUCTS HOT=HOTOUT COLD=COLDOUT

HEAT-TR-COEF SCALE=1.

FLASH-SPECS HOTOUT NPHASE=1 PHASE=L FREE-WATER=NO

FLASH-SPECS COLDOUT NPHASE=1 PHASE=L FREE-WATER=NO

EQUIP-SPECS TUBE-NPASS=8 TEMA-TYPE=F SHELL-DIAM=39. <in> &

SHELL-BND-SP=0.25 <in>

TUBES TOTAL-NUMBER=1024 PATTERN=SQUARE LENGTH=16. &

INSIDE-DIAM=0.584 <in> OUTSIDE-DIAM=0.75 <in> PITCH=1. <in> &

TCOND=25.

NOZZLES SNOZ-INDIAM=2.469 <in> SNOZ-OUTDIAM=2.469 <in> &

TNOZ-INDIAM=4.026 <in> TNOZ-OUTDIAM=4.026 <in>

SEGB-SHELL NBAFFLE=38 NSEAL-STRIP=1 BAFFLE-CUT=0.25 &

SHELL-BFL-SP=0.1 <in> TUBE-BFL-SP=0.1 <in> IN-BFL-SP=0.6 &

OUT-BFL-SP=0.6

HOT-HCURVE 1 NPOINT=20

COLD-HCURVE 1 NPOINT=20

HOT-SIDE H-OPTION=GEOMETRY H-SCALE=1. FOUL-FACTOR=0.002 &

SHELL-TUBE=SHELL DP-OPTION=GEOMETRY

COLD-SIDE H-OPTION=GEOMETRY H-SCALE=1. FOUL-FACTOR=0.002 &

DP-OPTION=GEOMETRY

REPORT PROFILE

EO-CONV-OPTI


------------------------------------------------------------------------ Stream Variables


– 55 –

COLDIN COLDOUT HOTIN HOTOUT---------------------------STREAM ID COLDIN COLDOUT HOTIN HOTOUTFROM : ---- H1 ---- H1TO : H1 ---- H1 ----

SUBSTREAM: MIXEDPHASE: LIQUID LIQUID LIQUID LIQUIDCOMPONENTS: LBMOL/HR

TOLUENE 1356.6236 1356.6236 0.0 0.0STYRENE 0.0 0.0 1440.2094 1440.2094

TOTAL FLOW:LBMOL/HR 1356.6236 1356.6236 1440.2094 1440.2094LB/HR 1.2500+05 1.2500+05 1.5000+05 1.5000+05CUFT/HR 2353.1302 2618.0856 3140.9333 2899.5818


ENTHALPY:BTU/LBMOL 6023.3178 1.2381+04 5.4993+04 4.9004+04BTU/LB 65.3710 134.3724 528.0063 470.5051BTU/HR 8.1714+06 1.6797+07 7.9201+07 7.0576+07


DENSITY:LBMOL/CUFT 0.5765 0.5182 0.4585 0.4967LB/CUFT 53.1207 47.7448 47.7565 51.7316

AVG MW 92.1405 92.1405 104.1515 104.1515

Selected Process Unit Output BLOCK: H1 MODEL: HEATX-----------------------------

FLOW DIRECTION AND SPECIFICATION:COUNTERCURRENT HEAT EXCHANGERSPECIFIED EXCHANGER AREASPECIFIED VALUE SQFT 3217.0000

EQUIPMENT SPECIFICATIONS:NUMBER OF SHELL PASSES 2NUMBER OF TUBE PASSES 8TEMA SHELL TYPE FORIENTATION HORIZONTALBAFFLE TYPE SEGMENTALSHELL INSIDE DIAMETER FT 3.2500SHELL TO BUNDLE CLEARANCE FT 0.0208

SPECIFICATIONS FOR TUBES:TOTAL NUMBER OF TUBES 1024TUBE TYPE BARETUBE PATTERN SQUARETUBE MATERIAL CARBON-STEELTUBE LENGTH FT 16.0000TUBE INSIDE DIAMETER FT 0.0487TUBE OUTSIDE DIAMETER FT 0.0625TUBE PITCH FT 0.0833TUBE THERMAL CONDUCTIVITY BTU-FT/HR-SQFT-R 25.0000

SPECIFICATIONS FOR SEGMENTAL BAFFLE SHELL:NUMBER OF BAFFLES 38NUMBER OF SEALING STRIP PAIRS 1TUBES IN WINDOW YESBAFFLE CUT 0.2500SHELL TO BAFFLE CLEARANCE FT 0.0083TUBE TO BAFFLE CLEARANCE FT 0.0083CENTRAL BAFFLE SPACING FT 0.8222INLET BAFFLE SPACING FT 0.6000


– 56 –

OUTLET BAFFLE SPACING FT 0.6000

SPECIFICATIONS FOR NOZZLES:SHELL INLET NOZZLE DIAMETER FT 0.2058SHELL OUTLET NOZZLE DIAMETER FT 0.2058TUBE INLET NOZZLE DIAMETER FT 0.3355TUBE OUTLET NOZZLE DIAMETER FT 0.3355

*** OVERALL RESULTS ***STREAMS:

--------------------------------------| |

HOTIN ----->| HOT (SHELL) |-----> HOTOUTT= 3.0000D+02 | | T= 1.7813D+02P= 5.0000D+01 | | P= 4.0277D+01V= 0.0000D+00 | | V= 0.0000D+00

| |COLDOUT <-----| COLD (TUBE) |<----- COLDINT= 2.5498D+02 | | T= 1.0000D+02P= 8.5874D+01 | | P= 9.0000D+01V= 0.0000D+00 | | V= 0.0000D+00

--------------------------------------

DUTY AND AREA:CALCULATED HEAT DUTY BTU/HR 8625176.3970CALCULATED (REQUIRED) AREA SQFT 3216.9807ACTUAL EXCHANGER AREA SQFT 3217.0000PER CENT OVER-DESIGN 0.0006

HEAT TRANSFER COEFFICIENT:AVERAGE COEFFICIENT (DIRTY) BTU/HR-SQFT-R 63.9835AVERAGE COEFFICIENT (CLEAN) BTU/HR-SQFT-R 90.4114

LOG-MEAN TEMPERATURE DIFFERENCE:THERMAL EFFECTIVENESS (XI) 0.7777NUMBER OF TRANSFER UNITS (NTU) 3.6905LMTD CORRECTION FACTOR 0.7116LMTD (CORRECTED) F 41.9036

STREAM VELOCITIES:SHELLSIDE MAX. CROSSFLOW VEL. FT/SEC 2.5906SHELLSIDE MAX. CROSSFLOW REYNOLDS NO. 50327.8397SHELLSIDE MAX. WINDOW VEL. FT/SEC 2.0860SHELLSIDE MAX. WINDOW REYNOLDS NO. 40525.1971TUBESIDE MAX. VELOCITY FT/SEC 3.0208TUBESIDE MAX. REYNOLDS NO. 45680.4836

PRESSURE DROP:SHELLSIDE, BAFFLED FLOW AREA PSI 4.5462SHELLSIDE, NOZZLE PSI 5.1766SHELLSIDE, TOTAL PSI 9.7228TUBESIDE, TUBES PSI 3.5838TUBESIDE, NOZZLE PSI 0.5421TUBESIDE, TOTAL PSI 4.1259

PRESSURE DROP PARAMETER:SHELL SIDE: 149301.6600TUBE SIDE: 92382.6749

*** ZONE PROFILES ***ZONE 1:-----------

SHELLSIDE:CROSSFLOW/WINDOW CROSSFLOW/WINDOW

TEMPERATURE VELOCITY REYNOLDS NUMBER PRANDTL NUMBERPOINT F FT/SEC

1 288.526 2.591/ 2.086 50327.8/ 40525.2 4.3422 265.138 2.549/ 2.052 46299.3/ 37281.3 4.4853 241.133 2.508/ 2.020 42175.1/ 33960.4 4.6734 216.468 2.469/ 1.988 37975.8/ 30579.0 4.9215 191.094 2.430/ 1.957 33728.7/ 27159.1 5.246


– 57 –

TUBESIDE:

TEMPERATURE VELOCITY REYNOLDS NUMBER PRANDTL NUMBERPOINT F FT/SEC

1 240.793 3.021 45680.5 4.2342 211.649 2.956 39388.8 4.5723 181.392 2.893 33807.1 4.9484 149.899 2.833 28784.9 5.3825 117.018 2.774 24146.0 5.921

HEAT TRANSFER:

WALL TEMP. HS HT U AREAPOINT F <---- BTU/HR-SQFT-R ----> SQFT

1 256.885 164.203 322.868 66.895 759.2182 230.204 161.888 304.803 65.481 692.1523 202.722 159.126 286.554 63.909 634.9564 174.391 155.866 267.773 62.139 586.0645 145.187 152.050 247.796 60.094 544.591

HEATX COLD-HCURVE: H1 HCURVE 1-------------------------------------

INDEPENDENT VARIABLE: DUTYPRESSURE PROFILE: CONSTANTPROPERTY OPTION SET: RK-SOAVE STANDARD RKS EQUATION OF STATE

-----------------------------------------------------! DUTY ! PRES ! TEMP ! VFRAC !! ! ! ! !! ! ! ! !! ! ! ! !! BTU/HR ! PSI ! F ! !! ! ! ! !!============!============!============!============!! 0.0 ! 85.8741 ! 100.0291 ! 0.0 !! 4.1072+05 ! 85.8741 ! 108.1814 ! 0.0 !! 8.2145+05 ! 85.8741 ! 116.2416 ! 0.0 !! 1.2322+06 ! 85.8741 ! 124.2125 ! 0.0 !! 1.6429+06 ! 85.8741 ! 132.0969 ! 0.0 !!------------+------------+------------+------------!! 2.0536+06 ! 85.8741 ! 139.8974 ! 0.0 !! 2.4643+06 ! 85.8741 ! 147.6163 ! 0.0 !! 2.8751+06 ! 85.8741 ! 155.2561 ! 0.0 !! 3.2858+06 ! 85.8741 ! 162.8189 ! 0.0 !! 3.6965+06 ! 85.8741 ! 170.3070 ! 0.0 !!------------+------------+------------+------------!! 4.1072+06 ! 85.8741 ! 177.7224 ! 0.0 !! 4.5179+06 ! 85.8741 ! 185.0669 ! 0.0 !! 4.9287+06 ! 85.8741 ! 192.3424 ! 0.0 !! 5.3394+06 ! 85.8741 ! 199.5507 ! 0.0 !! 5.7501+06 ! 85.8741 ! 206.6935 ! 0.0 !!------------+------------+------------+------------!! 6.1608+06 ! 85.8741 ! 213.7722 ! 0.0 !! 6.5716+06 ! 85.8741 ! 220.7884 ! 0.0 !! 6.9823+06 ! 85.8741 ! 227.7435 ! 0.0 !! 7.3930+06 ! 85.8741 ! 234.6388 ! 0.0 !! 7.8037+06 ! 85.8741 ! 241.4755 ! 0.0 !!------------+------------+------------+------------!! 8.2145+06 ! 85.8741 ! 248.2548 ! 0.0 !! 8.6252+06 ! 85.8741 ! 254.9779 ! 0.0 !-----------------------------------------------------

HEATX HOT-HCURVE: H1 HCURVE 1-------------------------------------

INDEPENDENT VARIABLE: DUTYPRESSURE PROFILE: CONSTANTPROPERTY OPTION SET: RK-SOAVE STANDARD RKS EQUATION OF STATE

-----------------------------------------------------! DUTY ! PRES ! TEMP ! VFRAC !! ! ! ! !! ! ! ! !


– 58 –

! ! ! ! !! BTU/HR ! PSI ! F ! !! ! ! ! !!============!============!============!============!! 0.0 ! 40.2773 ! 300.0369 ! 0.0 !! -4.1072+05 ! 40.2773 ! 294.5902 ! 0.0 !! -8.2145+05 ! 40.2773 ! 289.1111 ! 0.0 !! -1.2322+06 ! 40.2773 ! 283.5989 ! 0.0 !! -1.6429+06 ! 40.2773 ! 278.0534 ! 0.0 !!------------+------------+------------+------------!! -2.0536+06 ! 40.2773 ! 272.4740 ! 0.0 !! -2.4643+06 ! 40.2773 ! 266.8601 ! 0.0 !! -2.8751+06 ! 40.2773 ! 261.2113 ! 0.0 !! -3.2858+06 ! 40.2773 ! 255.5271 ! 0.0 !! -3.6965+06 ! 40.2773 ! 249.8068 ! 0.0 !!------------+------------+------------+------------!! -4.1072+06 ! 40.2773 ! 244.0498 ! 0.0 !! -4.5179+06 ! 40.2773 ! 238.2557 ! 0.0 !! -4.9287+06 ! 40.2773 ! 232.4237 ! 0.0 !! -5.3394+06 ! 40.2773 ! 226.5533 ! 0.0 !! -5.7501+06 ! 40.2773 ! 220.6438 ! 0.0 !!------------+------------+------------+------------!! -6.1608+06 ! 40.2773 ! 214.6946 ! 0.0 !! -6.5716+06 ! 40.2773 ! 208.7049 ! 0.0 !! -6.9823+06 ! 40.2773 ! 202.6741 ! 0.0 !! -7.3930+06 ! 40.2773 ! 196.6014 ! 0.0 !! -7.8037+06 ! 40.2773 ! 190.4863 ! 0.0 !!------------+------------+------------+------------!! -8.2145+06 ! 40.2773 ! 184.3278 ! 0.0 !! -8.6252+06 ! 40.2773 ! 178.1253 ! 0.0 !-----------------------------------------------------


– 59 –

Exercise C.2 Solution using HYSYS.Plant

These results can be reproduced using the file: TOLUENE_MANUFACTURE_EX.HSC

a) The annual costs computed using HYSYS is plotted below. The maximum

possible preheat temperature is 617 oF (here the temperature profiles in the heat

exchanger are almost pinched).

b) From the above results, it is noted that the optimal pre-heat temperature is 600 oF,

at which the annual cost is $369,500. For this value of pre-heat temperature, the

required heat transfer area is 7,110 ft2

c) The total annual cost with no pre-heating is $1,173,000. To bring the n-heptane to

its dew point, the pre-heat temperature needs to be 209.3 oF (computed by setting

the vapor fraction to unity), for which the annual cost is $765,300.


– 60 –

Separations

HYSYS.Plant

The materials supporting a course in separations assume that the students have already covered most of the theory on multicomponent separations (flash and distillation). It is recommended that 1-2 hours of computer laboratory time be allocated to allow students to review the multimedia support available. The following sequence of modules is recommended:

Session 1: Cover all of the material under HYSYS – Separations in the multimedia: Click on Overview, and the cover all of the materials supporting Flash and Distillation. The latter provides a framework for systematic multicomponent distillation column design, in which the Component Splitter assists in the selection of operating pressure, the Short-cut Column, using FUG methods, is employed to estimate the number of stages, the location of the feed tray, and the required reflux ratio, and finally the Column is used for the rigorous solution of MESH equations.

Session 2: Many students require assistance in the correct selection of property estimation

methods. It may be helpful to review the module on Physical Property Estimation – Package Selection. Advanced students are encouraged to also review the tutorial on multi-draw tower optimization.

To reinforce their acquired capabilities, students should be assigned one or more homework exercises. Two example exercises are provided: (a) The design of a series of two columns for the separation of a mixture of alcohols; (b) A single multicomponent column.


– 61 –

Separations ASPEN PLUS

The materials supporting a course in separations assume that the students have already

covered most of the theory on multicomponent separations (flash and distillation). It is recommended that 1-2 hours of computer laboratory time be allocated to allow students to review the multimedia support available. The following sequence of modules is recommended: Session 1: Under ASPEN – Tutorials – Separations, the main menu refers to item 2.

Distillation. Students should see the videos of an industrial distillation complex and a laboratory tower. Then, they should review the module on Split-fraction Model (SEP2), which shows how to set the tower pressure, given specifications of the split fractions. Then, they should refer to the module on FUG Shortcut Design (DSTWU) to review methods for estimating the number of trays, the feed tray, and the reflux ratio. Finally, they should review the module on MESH Equations (RADFRAC)

Session 2: Many students require assistance in the correct selection of property estimation

methods. It may be helpful to review the module on Physical Property Estimation – Package Selection.

To reinforce their acquired capabilities, students should be assigned one or more homework exercises. Two typical exercises are provided: (a) The design of a series of two columns for the separation of a mixture of alcohols; (b) A single multicomponent column.

ICARUS Process Evaluator (IPE) IPE, an Aspen Tech product, takes results from any of the major process simulators, involving many kinds of equipment items, and estimates equipment sizes, purchase costs and installation costs leading to the total capital investment, operating costs, and profitability measures. WDS has developed a set of course notes, which are provided with these materials. Also, he is developing multimedia materials to provide instruction on the use of IPE. Eventually, these can be used in the separations course to estimate the investment costs for a distillation complex, as well as other separators. In these materials, we are providing Exercise 9.1 (SSL), which involves the sizing and costing of a distillation complex. Exercise 9.1 has been modified to include the usage of IPE.


– 62 –

Exercise D.1 Multicomponent Distillation Design Problem 1

In the manufacture of higher alcohols from carbon monoxide and hydrogen, a mixture of alcohols is obtained, which must be separated into desired products. A feed mixture of:

mol% ethanol 25 n-propanol 50 iso-butanol 10 n-butanol 15

has been isolated from methanol and heavier alcohols in prior distillation steps. It is a saturated liquid at the pressure of the first distillation column, to be determined in ‘a’ below. The three desired products are streams containing: 1. At least 98% of the ethanol at a purity of 98 mol%. 2. N-propanol with essentially all of the remaining ethanol and no more than 2% of the

isobutanol in the feed mixture. 3. At least 98% of the iso-butanol, all of the n-butanol, and no more than 1% of the n-propanol,

in the feed mixture. Two distillation towers are used. The first receives the feed mixture. Its distillate is fed to the second tower, which produces ethanol-rich and n-propanol-rich products. Use a process simulator to:

a. Determine the tower pressures that permit cooling water to be used in the condensers; that is,

let the cooling water be heated from 90-120°F and the bubble-point of the condensed overhead vapor be 130°F or higher. This assures that the minimum approach temperature difference is 10°F. Use total condensers. To avoid vacuum operation, pressures in the towers must exceed 20 psia. Assume no pressure drop in the towers. In ASPEN PLUS, use the SEP2 subroutine. In HYSYS.Plant, use Splitter.

b. Determine the minimum number of trays and the minimum reflux ratio. Then, let the actual

reflux ratio be 1.3 × Rmin and use the Gilliland correlation to determine the theoretical number of trays and the location of the feed tray. In ASPEN PLUS, use the DSTWU subroutine. In HYSYS.Plant, use Short-cut Column.

c. Using the design determined in a and b, simulate the towers; that is, solve the MESH

equations. In ASPEN PLUS, use the RADFRAC subroutine. In HYSYS.Plant, use Column.



– 63 –

Exercise D.2 Multicomponent Distillation Design Problem 2

The composition of a stream of 100 kgmol/hr at of a multicomponent mixture is:

mol% benzene 12.5toluene 22.5o-xylene 37.5n-propylbenzene 27.5

It is required to design a distillation column to separate the mixture such that the distillate contains at least 99% of the toluene and the bottoms at least 99.4% of the o-xylene, given that the stream is supplied at its bubble point, and both of the product streams are to be drawn as liquids. Use a process simulator to:

(a) Determine the tower pressure that permit cooling water to be used in the condenser;

that is, let the cooling water be heated from 25-40°C and the bubble-point of the condensed overhead vapor 50°C, with a lower bound on the operating pressure being 20 psia. You may neglect the pressure drop in the column throughout this exercise. In ASPEN PLUS, use the SEP2 subroutine. In HYSYS.Plant, use Splitter.

(b) Determine the minimum number of trays and the minimum reflux ratio. Then, let the actual reflux ratio be 1.3 × Rmin and use the Gilliland correlation to determine the theoretical number of trays and the location of the feed tray. In ASPEN PLUS, use the DSTWU subroutine. In HYSYS.Plant, use Short-cut Column.

(c) Using the design determined in a and b, simulate the towers; that is, solve the MESH equations. In ASPEN PLUS, use the RADFRAC subroutine. In HYSYS.Plant, use Column.

(d) Following fouling of the heat transfer surface in the reboiler, it is estimated that the available heat transfer duty has dropped by 40%. Is it possible to make a design change in the column to allow the two specifications met previously to be maintained? Alternatively, without changing the number of trays or the location of the feed tray determined previously, what is the reflux ratio that will allow at recovery of at least 90% of the toluene and 90% of the o-xylene for the fouled reboiler?



– 64 –

Exercise D.3 Distillation Sizing and Costing Problem (Exercise 9.1 (SSL) – Revised for IPE)

The feed to a sieve-tray distillation column operating at 1 atm is 700 lbmol/hr of 45 mol%

benzene and 55 mol% toluene at 1 atm and its bubble-point temperature of 201°F. The distillate contains 92 mol% benzene and boils at 179°F. The bottoms product contains 95 mol% toluene and boils at 227°F. The column has 23 trays spaced 18 in. apart, and its reflux ratio is 1.25. Column pressure drop is neglected. Tray efficiency is 80%. Estimate the total bare-module cost of the column, condenser, reflux accumulator, condenser pump, reboiler, and reboiler pump. Also, estimate the total permanent investment. Results should be computed using: (1) the cost charts in Chapter 9, and (2) IPE (ICARUS Process Evaluator). Compare the results.

Data

Molal heat of vaporization of distillate = 13,700 Btu/lbmol

Molal heat capacity of distillate = 40 Btu/lbmol °F

Overall U of condenser = 100 Btu/hr ft2 °F

Cooling water from 90°F to 120°F Heat flux for reboiler = 12,000 Btu/hr ft2

Saturated steam at 60 psia

Reflux accumulator residence time = 5 minutes at half full; L/D = 4

Pump heads = 50 psia; suction pressure = 1 atm, efficiency = 1 Calculate the flooding velocity of the vapor using the procedure in Example 10.2. Use 85 percent of the flooding velocity to determine the column diameter.

Notes

The file, BENTOLDIST.BKP, is included on the CD-ROM that accompanies these notes. It contains the simulation results using the RADFRAC subroutine in ASPEN PLUS. This file should be used to prepare the report file for IPE. Note that the simulation was carried out using 20 stages (18 trays plus the condenser and reboiler). When using IPE, set the tray efficiency to 0.8 and IPE will adjust the number of trays to 23.

Since IPE does not size and cost a reboiler pump, a centrifugal pump should be added.

Also, since Chapter 9 does not include the cost charts for a pump, copies from Ulrich (1984) are attached.

IPE estimates the physical properties and heat-transfer coefficients. Do not adjust these.

In IPE, reset the temperatures of cooling water (90 and 120°F) and add a utility for 60

psia steam. Use the steam tables to obtain the physical properties.

Use a kettle reboiler with a floating head.


– 65 –

IPE sizes the tower using a 24 in tray spacing as the default. After sizing (mapping) is complete, adjust the tray spacing to 18 in. Note that the height of the tower must be adjusted accordingly.

Note that IPE estimates the costs of Direct Material and Manpower for each equipment

item. These are also referred to as the costs of direct materials and labor, CDML = CP + CM + CL.

To Be Submitted

Include your hand calculations using the cost charts and the methods in Chapter 9. (Note that these methods are identical to those in Example 10.2).

Do not submit the entire IPE Capital Estimate Report. Instead, prepare a table showing a

comparison of the equipment sizes and purchased costs. When using the methods in Chapter 9, show the bare module cost. For IPE, show the direct cost of materials and labor. It is sufficient to take the numbers from IPE. For both methods, show the calculations leading to the total permanent investment. Discuss the results.

ASPEN PLUS Solution


– 66 –

Exercise D.1 Solution using HYSYS.Plant

Solution reproduced in: DISTIL_EX_1.hsc

Based upon the specifications, the desired product streams are determined by material balance:

FEED D1 B1 D2 B2 Ethanol 25.0 25.0 - 24.5 0.5

1-Propanol 50.0 49.5 0.5 0.5 49.0 i-Butanol 10.0 0.2 9.8 - 0.2 1- Butanol 15.0 - 15.0 - -

Total 100.0 74.7 25.3 25.0 49.7 a. In HYSYS.Plant, the column pressures are determined using the Component

Splitter, adjusting the distillate pressure to achieve distillate bubble points at 130°F, with lower bounds of 20 psia to avoid vacuum operation. Note that because the most volatile species, ethanol, is present in the distillate of both towers, the pressure is adjusted to its lower bound in both towers.

Component Splitter: X-100 PARAMETERS Stream Specifications Overhead Pressure: 20.00 psia Overhead Vapour Fraction: 0.0000 Bottoms Pressure: 20.00 psia Bottoms Vapour Fraction: 0.0000 SPLITS Component Fraction To Overhead Component Overhead Fraction Ethanol 1 1-Propanol 0.99 PROPERTIES


– 67 –

F1 Overall Liquid Phase Vapour Phase Vapour/Phase Fraction 0 1 0 Temperature: (F) 215.7 215.7 215.7 Pressure: (psia) 20 20 20 Molar Flow (lbmole/hr) 100 100 0 Mass Flow (lb/hr) 6010 6010 0 Liquid Volume Flow (barrel/day) 511.6 511.6 0 Molar Enthalpy (Btu/lbmole) -1.24E+05 -1.24E+05 -1.05E+05 Mass Enthalpy (Btu/lb) -2065 -2065 -1882 Molar Entropy (Btu/lbmole-F) 13.49 13.49 36.13 Mass Entropy (Btu/lb-F) 0.2245 0.2245 0.6496 Heat Flow (Btu/hr) -1.24E+07 -1.24E+07 0 D1 Overall Liquid Phase Vapour Phase Vapour/Phase Fraction 0 1 0 Temperature: (F) 207.6 207.6 207.6 Pressure: (psia) 20 20 20 Molar Flow (lbmole/hr) 74.7 74.7 0 Mass Flow (lb/hr) 4141 4141 0 Liquid Volume Flow (barrel/day) 353.7 353.7 0 Molar Enthalpy (Btu/lbmole) -1.21E+05 -1.21E+05 -1.03E+05 Mass Enthalpy (Btu/lb) -2188 -2188 -1947 Molar Entropy (Btu/lbmole-F) 9.962 9.962 34.28 Mass Entropy (Btu/lb-F) 0.1797 0.1797 0.6464 Heat Flow (Btu/hr) -9.06E+06 -9.06E+06 0 B1 Overall Liquid Phase Vapour Phase Vapour/Phase Fraction 0 1 0 Temperature: (F) 251.5 251.5 251.5 Pressure: (psia) 20 20 20 Molar Flow (lbmole/hr) 25.3 25.3 0 Mass Flow (lb/hr) 1868 1868 0 Liquid Volume Flow (barrel/day) 157.9 157.9 0 Molar Enthalpy (Btu/lbmole) -1.31E+05 -1.31E+05 -1.15E+05 Mass Enthalpy (Btu/lb) -1778 -1778 -1558 Molar Entropy (Btu/lbmole-F) 21.03 21.03 43.53 Mass Entropy (Btu/lb-F) 0.2848 0.2848 0.5912 Heat Flow (Btu/hr) -3.32E+06 -3.32E+06 0


– 68 –

Component Splitter: X-101 PARAMETERS Stream Specifications Overhead Pressure: 20.00 psia Overhead Vapour Fraction: 1.0000 Bottoms Pressure: 20.00 psia Bottoms Vapour Fraction: 0.0000 SPLITS Component Fraction To Overhead Component Overhead Fraction Ethanol 0.98 1-Propanol 0.0101 PROPERTIES Overall Liquid Phase Vapour Phase D1 0 1 0 Vapour/Phase Fraction 207.6 207.6 207.6 Temperature: (F) 20 20 20 Pressure: (psia) 74.7 74.7 0 Molar Flow (lbmole/hr) 4141 4141 0 Mass Flow (lb/hr) 353.7 353.7 0 Liquid Volume Flow (barrel/day) -1.21E+05 -1.21E+05 -1.03E+05 Molar Enthalpy (Btu/lbmole) -2188 -2188 -1947 Mass Enthalpy (Btu/lb) 9.962 9.962 34.28 Molar Entropy (Btu/lbmole-F) 0.1797 0.1797 0.6464 Mass Entropy (Btu/lb-F) -9.06E+06 -9.06E+06 0 Heat Flow (Btu/hr) Overall Vapour Phase Liquid Phase D2 1 1 0 Vapour/Phase Fraction 188.1 188.1 188.1 Temperature: (F) 20 20 20 Pressure: (psia) 25 25 0 Molar Flow (lbmole/hr) 1159 1159 0 Mass Flow (lb/hr) 99.65 99.65 0 Liquid Volume Flow (barrel/day) -9.95E+04 -9.95E+04 -1.16E+05 Molar Enthalpy (Btu/lbmole) -2147 -2147 -2487 Mass Enthalpy (Btu/lb) 31.08 31.08 6.095 Molar Entropy (Btu/lbmole-F) 0.6705 0.6705 0.1307 Mass Entropy (Btu/lb-F) -2.49E+06 -2.49E+06 0 Heat Flow (Btu/hr) Overall Liquid Phase Vapour Phase B2 0 1 0 Vapour/Phase Fraction 221.6 221.6 221.6 Temperature: (F) 20 20 20 Pressure: (psia) 49.7 49.7 0 Molar Flow (lbmole/hr) 2983 2983 0 Mass Flow (lb/hr) 254 254 0 Liquid Volume Flow (barrel/day) -1.24E+05 -1.24E+05 -1.07E+05 Molar Enthalpy (Btu/lbmole) -2062 -2062 -1789


– 69 –

Mass Enthalpy (Btu/lb) 10.7 10.7 35.11 Molar Entropy (Btu/lbmole-F) 0.1783 0.1783 0.5865 Mass Entropy (Btu/lb-F) -6.15E+06 -6.15E+06 0 Heat Flow (Btu/hr)

b. Using the tower pressures determined in ‘a’, the numbers of trays and the reflux ratios are determined using short-cut column in HYSYS.Plant, for splits specified to give the desired products. For the first column, the minimum number of trays is 22. For 1.3Rmin, the design calls for 44 trays with reflux ratio of 2.298. For the second column, Nmin = 12, with a design for 1.3Rmin giving 23 trays and a reflux ratio of 3.604.

Shortcut Column: T-100B Parameters Component Mole Fraction Light Key 1-Propanol 1.98E-02 Heavy Key i-Butanol 2.70E-03 Pressures (psia) Reflux Ratios Condenser Pressure 20 External Reflux Ratio 2.298 Reboiler Pressure 20 Minimum Reflux Ratio 1.768 User Variables Results Summary Trays / Temperatures Flows Minimum # of Trays 21.52 Rectify Vapour (lbmole/hr) 246.4 Actual # of Trays 43.63 Rectify Liquid (lbmole/hr) 171.7 Optimal Feed Stage 24.7 Stripping Vapour (lbmole/hr) 246.4 Condenser Temperature (F) 207.6 Stripping Liquid (lbmole/hr) 271.7 Reboiler Temperature (F) 251.5 Condenser Duty (Btu/hr) -4.11E+06 Reboiler Duty (Btu/hr) 4.14E+06


– 70 –

Shortcut Column: T-101B Parameters Component Mole Fraction Light Key Ethanol 1.01E-02 Heavy Key 1-Propanol 2.00E-02 Pressures (psia) Reflux Ratios Condenser Pressure 20 External Reflux Ratio 3.604 Reboiler Pressure 20 Minimum Reflux Ratio 2.772 User Variables Results Summary Trays / Temperatures Flows Minimum # of Trays 11.94 Rectify Vapour (lbmole/hr) 115.1 Actual # of Trays 23.76 Rectify Liquid (lbmole/hr) 90.09 Optimal Feed Stage 11.89 Stripping Vapour (lbmole/hr) 115.1 Condenser Temperature (F) 187.6 Stripping Liquid (lbmole/hr) 164.8 Reboiler Temperature (F) 221.6 Condenser Duty (Btu/hr) -1.88E+06 Reboiler Duty (Btu/hr) 1.89E+06

c. Using the design determined in ‘a’ and ‘b’, the MESH equations are solved using column in HYSYS.Plant. Note that minor adjustments in the the reflux ratios in both columns are made by the internal design specification to achieve the required component molar flow rates: In the first column, the reflux ratio is decreased from 2.298 to 2.192, while in the second column, it is reduced from 3.60 to 3.54.

Distillation: T-100C @Main MONITOR Specifications Summary Specified Value Current Value Wt. Error Wt. Tol. Abs. Tol. Active EIso-prop in D 49.50 lbmole/hr 49.50 lbmole/hr 2.62E-08 1.00E-02 2.205 lbmole/hr On OIso-butanol in B 9.800 lbmole/hr 9.800 lbmole/hr 1.39E-08 1.00E-02 2.205 lbmole/hr On ODistillate Rate 74.70 lbmole/hr 74.70 lbmole/hr 5.28E-07 1.00E-02 2.205 lbmole/hr Off OReflux Ratio 2.298 2.192 -4.61E-02 1.00E-02 1.00E-02 Off OReflux Rate 163.7 lbmole/hr 1.00E-02 2.205 lbmole/hr Off OBtms Prod Rate 25.30 lbmole/hr 1.00E-02 2.205 lbmole/hr Off O


– 71 –

SPECS Column Specification Parameters Iso-prop in D Draw: D1C Flow Basis: Molar Phase: Liquid Components: 1-Propanol Iso-butanol in B Draw: B1C Flow Basis: Molar Phase: Liquid Components: i-Butanol Distillate Rate Stream: D1C Flow Basis: Molar Reflux Ratio Stage: Condenser Flow Basis: Molar Liquid Specification: Reflux Rate Stage: Condenser Flow Basis: Molar Liquid Specification: Btms Prod Rate Stream: B1C Flow Basis: Molar User Variables PROFILES General Parameters Sub-Flow Sheet: T-100C (COL1) Number of Stages: 44 SOLVER Column Solving Algorithm: HYSIM Inside-Out Solving Options Acceleration Parameters Maximum Iterations: 10000 Accelerate K Value & H Model Parameters: Off Equilibrium Error Tolerance: 1.000e-07 Heat/Spec Error Tolerance: 1.000e-007 Save Solutions as Initial Estimate: On Super Critical Handling Model: Simple K Trace Level: Low Init from Ideal K's: Off Damping Parameters Initial Estimate Generator Parameters Azeotrope Check: Off Iterative IEG (Good for Chemicals): Off Fixed Damping Factor: 1 PROPERTIES Properties : F3 Overall Vapour Phase Liquid Phase Vapour/Phase Fraction 0 0 1 Temperature: (F) 215.7 215.7 215.7 Pressure: (psia) 20 20 20 Molar Flow (lbmole/hr) 100 5.12E-09 100 Mass Flow (lb/hr) 6010 2.85E-07 6010 Liquid Volume Flow (barrel/day) 511.6 2.43E-08 511.6 Molar Enthalpy (Btu/lbmole) -1.24E+05 0 -1.24E+05 Mass Enthalpy (Btu/lb) -2065 0 -2065 Molar Entropy (Btu/lbmole-F) 13.49 0 13.49 Mass Entropy (Btu/lb-F) 0.2245 0 0.2245 Heat Flow (Btu/hr) -1.24E+07 0 -1.24E+07


– 72 –

Properties : D1C Overall Vapour Phase Liquid Phase Vapour/Phase Fraction 0 0 1 Temperature: (F) 207.6 207.6 207.6 Pressure: (psia) 20 20 20 Molar Flow (lbmole/hr) 74.7 0 74.7 Mass Flow (lb/hr) 4141 0 4141 Liquid Volume Flow (barrel/day) 353.7 0 353.7 Molar Enthalpy (Btu/lbmole) -1.21E+05 -1.03E+05 -1.21E+05 Mass Enthalpy (Btu/lb) -2188 -1947 -2188 Molar Entropy (Btu/lbmole-F) 9.962 34.28 9.962 Mass Entropy (Btu/lb-F) 0.1797 0.6464 0.1797 Heat Flow (Btu/hr) -9.06E+06 0 -9.06E+06 Properties : B1C Overall Vapour Phase Liquid Phase Vapour/Phase Fraction 0 0 1 Temperature: (F) 251.5 251.5 251.5 Pressure: (psia) 20 20 20 Molar Flow (lbmole/hr) 25.3 0 25.3 Mass Flow (lb/hr) 1868 0 1868 Liquid Volume Flow (barrel/day) 157.9 0 157.9 Molar Enthalpy (Btu/lbmole) -1.31E+05 -1.15E+05 -1.31E+05 Mass Enthalpy (Btu/lb) -1778 -1558 -1778 Molar Entropy (Btu/lbmole-F) 21.03 43.53 21.03 Mass Entropy (Btu/lb-F) 0.2848 0.5912 0.2848 Heat Flow (Btu/hr) -3.32E+06 0 -3.32E+06

Tray Summary Flow Basis: Molar Reflux Ratio: 2.192 Temp. Pressure Liquid Vapour Feeds Draws Duties (F) (psia) (lbmole/hr) (lbmole/hr) (lbmole/hr) (lbmole/hr) (Btu/hr) Condenser 207.6 20 163.7 74.7 L -3.98E+06 1__Main TS 213 20 163.9 238.4 2__Main TS 215.7 20 164 238.6 3__Main TS 217 20 164.1 238.7 4__Main TS 217.5 20 164.2 238.8 5__Main TS 217.8 20 164.2 238.9 6__Main TS 217.9 20 164.2 238.9 7__Main TS 218 20 164.2 238.9 8__Main TS 218.1 20 164.2 238.9 9__Main TS 218.1 20 164.2 238.9 10__Main TS 218.2 20 164.2 238.9 11__Main TS 218.3 20 164.2 238.9 12__Main TS 218.4 20 164.2 238.9 13__Main TS 218.5 20 164.1 238.9 14__Main TS 218.6 20 164.1 238.8 15__Main TS 218.7 20 164.1 238.8 16__Main TS 218.9 20 164.1 238.8 17__Main TS 219 20 164 238.8


– 73 –

18__Main TS 219.2 20 164 238.7 19__Main TS 219.5 20 163.9 238.7 20__Main TS 219.7 20 163.8 238.6 21__Main TS 220.1 20 163.7 238.5 22__Main TS 220.5 20 163.5 238.4 23__Main TS 221.1 20 163.3 238.2 24__Main TS 221.9 20 163 238 25__Main TS 222.9 20 263.7 237.7 100 L 26__Main TS 225 20 264.2 238.4 27__Main TS 226.3 20 264.5 238.9 28__Main TS 227.1 20 264.7 239.2 29__Main TS 227.8 20 264.8 239.4 30__Main TS 228.4 20 264.8 239.5 31__Main TS 229 20 264.8 239.5 32__Main TS 229.8 20 264.9 239.5 33__Main TS 230.7 20 264.9 239.6 34__Main TS 231.9 20 264.9 239.6 35__Main TS 233.3 20 265 239.6 36__Main TS 234.9 20 265.2 239.7 37__Main TS 236.6 20 265.3 239.9 38__Main TS 238.4 20 265.5 240 39__Main TS 240.3 20 265.6 240.2 40__Main TS 242.2 20 265.7 240.3 41__Main TS 244 20 265.6 240.4 42__Main TS 245.9 20 265.4 240.3 43__Main TS 247.7 20 265.1 240.1 44__Main TS 249.6 20 264.7 239.8 Reboiler 251.5 20 239.4 25.3 L 4.01E+06


– 74 –

Distillation: T-101C @Main MONITOR Specifications Summary Specified Value Current Value Wt. Error Wt. Tol. Abs. Tol. AbEthanol in D 24.50 lbmole/hr 24.50 lbmole/hr 5.99E-09 1.00E-02 2.205 lbmole/hr 2.2Iso-propanol in B 49.00 lbmole/hr 49.00 lbmole/hr -1.58E-08 1.00E-02 2.205 lbmole/hr 2.2Distillate Rate 25.00 lbmole/hr 25.00 lbmole/hr 5.68E-07 1.00E-02 2.205 lbmole/hr 2.2Reflux Ratio 3.6 3.537 -1.75E-02 1.00E-02 1.00E-02 Reflux Rate 88.43 lbmole/hr 1.00E-02 2.205 lbmole/hr 2.2Btms Prod Rate 49.70 lbmole/hr 1.00E-02 2.205 lbmole/hr 2.2SPECS Column Specification Parameters Ethanol in D Draw: D2C @COL2 Flow Basis: Molar Phase: Liquid Components: Ethanol Iso-propanol in B Draw: B2C @COL2 Flow Basis: Molar Phase: Liquid Components: 1-Propanol Distillate Rate Stream: D2C @COL2 Flow Basis: Molar Reflux Ratio Stage: Condenser Flow Basis: Molar Liquid Specification: Reflux Rate Stage: Condenser Flow Basis: Molar Liquid Specification: Btms Prod Rate Stream: B2C @COL2 Flow Basis: Molar User Variables PROFILES General Parameters Sub-Flow Sheet: T-101C (COL2) Number of Stages: 24 SOLVER Column Solving Algorithm: HYSIM Inside-Out Solving Options Acceleration Parameters Maximum Iterations: 10000 Accelerate K Value & H Model Parameters: Off Equilibrium Error Tolerance: 1.000e-07 Heat/Spec Error Tolerance: 1.000e-007 Save Solutions as Initial Estimate: On Super Critical Handling Model: Simple K Trace Level: Low Init from Ideal K's: Off Damping Parameters Initial Estimate Generator Parameters Azeotrope Check: Off Iterative IEG (Good for Chemicals): Off Fixed Damping Factor: 1 PROPERTIES Properties : D1C @COL2 Overall Liquid Phase Vapour/Phase Fraction 0 1


– 75 –

Temperature: (F) 207.6 207.6 Pressure: (psia) 20 20 Molar Flow (lbmole/hr) 74.7 74.7 Mass Flow (lb/hr) 4141 4141 Liquid Volume Flow (barrel/day) 353.7 353.7 Molar Enthalpy (Btu/lbmole) -1.21E+05 -1.21E+05 Mass Enthalpy (Btu/lb) -2188 -2188 Molar Entropy (Btu/lbmole-F) 9.962 9.962 Mass Entropy (Btu/lb-F) 0.1797 0.1797 Heat Flow (Btu/hr) -9.06E+06 -9.06E+06 Properties : D2C @COL2 Overall Vapour Phase Liquid Phase Vapour/Phase Fraction 0 0 1 Temperature: (F) 187.6 187.6 187.6 Pressure: (psia) 20 20 20 Molar Flow (lbmole/hr) 25 0 25 Mass Flow (lb/hr) 1159 0 1159 Liquid Volume Flow (barrel/day) 99.65 0 99.65 Molar Enthalpy (Btu/lbmole) -1.16E+05 -9.94E+04 -1.16E+05 Mass Enthalpy (Btu/lb) -2498 -2152 -2498 Molar Entropy (Btu/lbmole-F) 5.864 30.95 5.864 Mass Entropy (Btu/lb-F) 0.1265 0.6698 0.1265 Heat Flow (Btu/hr) -2.90E+06 0 -2.90E+06 Properties : B2C @COL2 Overall Vapour Phase Liquid Phase Vapour/Phase Fraction 0 0 1 Temperature: (F) 221.6 221.6 221.6 Pressure: (psia) 20 20 20 Molar Flow (lbmole/hr) 49.7 0 49.7 Mass Flow (lb/hr) 2983 0 2983 Liquid Volume Flow (barrel/day) 254 0 254 Molar Enthalpy (Btu/lbmole) -1.24E+05 -1.07E+05 -1.24E+05 Mass Enthalpy (Btu/lb) -2062 -1789 -2062 Molar Entropy (Btu/lbmole-F) 10.7 35.11 10.7 Mass Entropy (Btu/lb-F) 0.1783 0.5865 0.1783 Heat Flow (Btu/hr) -6.15E+06 0 -6.15E+06

Tray Summary Flow Basis: Molar Reflux Ratio: 3.537 Temp. Pressure Liquid Vapour Feeds Feeds Draws Duties (F) (psia) (lbmole/hr) (lbmole/hr) (lbmole/hr) (lbmole/hr) (lbmole/hr) (Btu/hr) Condenser 187.6 20 88.43 25 L -1.85E+061__Main TS 188.1 20 88.3 113.4 2__Main TS 189 20 88.11 113.3 3__Main TS 190.2 20 87.86 113.1 4__Main TS 192 20 87.54 112.9 5__Main TS 194.2 20 87.19 112.5 6__Main TS 196.9 20 86.87 112.2 7__Main TS 199.7 20 86.61 111.9


– 76 –

8__Main TS 202.3 20 86.45 111.6 9__Main TS 204.6 20 86.36 111.4 10__Main TS 206.3 20 86.32 111.4 11__Main TS 207.5 20 86.3 111.3 12__Main TS 208.4 20 161 111.3 74.7 75.7 13__Main TS 209.4 20 161 111.3 14__Main TS 210.6 20 161 111.3 15__Main TS 211.9 20 161.1 111.3 16__Main TS 213.4 20 161.1 111.4 17__Main TS 214.8 20 161.2 111.4 18__Main TS 216.2 20 161.3 111.5 19__Main TS 217.5 20 161.5 111.6 20__Main TS 218.6 20 161.6 111.8 21__Main TS 219.5 20 161.7 111.9 22__Main TS 220.2 20 161.8 112 23__Main TS 220.8 20 161.9 112.1 24__Main TS 221.3 20 161.9 112.2 Reboiler 221.6 20 112.2 49.7 L 1.86E+06


– 77 –

Exercise D.1 Solution using ASPEN.PLUS Based upon the specifications, the desired product streams are determined by material balance:

FEED DIS1 BOT1 DIS2 BOT2 EtOH 25.0 25.0 - 24.5 0.5 nPOH 50.0 49.5 0.5 0.5 49.0 iBOH 10.0 0.2 9.8 - 0.2 nBOH 15.0 - 15.0 - -

Total 100.0 74.7 25.3 25.0 49.7 a. The column pressures are determined using the SEP2 subroutine in ASPEN

PLUS with design specifications that adjust the distillate pressure to achieve distillate bubble points at 130°F. The lower bound of 20 psia to avoid vacuum operation. Note that because the most volatile species, ethanol, is present in the distillate of both towers, the pressure is adjusted to its lower bound in both towers. The results below can be reproduced using the file SEP2.BKP.

FEED

BOT1

DIS1

DIS2

BOT2

D1 D2

ASPEN PLUS Program

TITLE 'PRESSURE DETERMINATION' IN-UNITS ENG DEF-STREAMS CONVEN ALL DESCRIPTION " General Simulation with English Units : F, psi, lb/hr, lbmol/hr, Btu/hr, cuft/hr. Property Method: None Flow basis for input: Mole Stream report composition: Mole flow DATABANKS PURE11 / AQUEOUS / SOLIDS / INORGANIC / & NOASPENPCD PROP-SOURCES PURE11 / AQUEOUS / SOLIDS / INORGANIC COMPONENTS ETHANOL C2H6O-2 / PROPANOL C3H8O-1 / ISOBU-01 C4H10O-3 /


– 78 –

N-BUT-01 C4H10O-1 FLOWSHEET BLOCK D1 IN=FEED OUT=DIS1 BOT1 BLOCK D2 IN=DIS1 OUT=DIS2 BOT2 PROPERTIES IDEAL STREAM FEED SUBSTREAM MIXED PRES=20. <psia> VFRAC=0. MOLE-FLOW=100. MOLE-FRAC ETHANOL 0.25 / PROPANOL 0.5 / ISOBU-01 0.1 / & N-BUT-01 0.15 BLOCK D1 SEP2 FRAC STREAM=DIS1 SUBSTREAM=MIXED COMPS=ETHANOL PROPANOL & ISOBU-01 N-BUT-01 FRACS=1. 0.99 0.02 0. FLASH-SPECS DIS1 PRES=20. VFRAC=0. FLASH-SPECS BOT1 PRES=20. VFRAC=0. BLOCK D2 SEP2 FRAC STREAM=DIS2 SUBSTREAM=MIXED COMPS=ETHANOL PROPANOL & ISOBU-01 N-BUT-01 FRACS=0.98 0.0101 0. 0. FLASH-SPECS DIS2 PRES=20. VFRAC=0. FLASH-SPECS BOT2 PRES=20. VFRAC=0. DESIGN-SPEC DS-1 DEFINE DIS1T STREAM-VAR STREAM=DIS1 SUBSTREAM=MIXED & VARIABLE=TEMP SPEC "DIS1T" TO "130" TOL-SPEC "0.001" VARY BLOCK-VAR BLOCK=D1 VARIABLE=PRES SENTENCE=FLASH-SPECS & ID1=DIS1 LIMITS "20" "100" DESIGN-SPEC DS-2 DEFINE DIS2T STREAM-VAR STREAM=DIS2 SUBSTREAM=MIXED & VARIABLE=TEMP SPEC "DIS2T" TO "130" TOL-SPEC "0.001" VARY BLOCK-VAR BLOCK=D2 VARIABLE=PRES SENTENCE=FLASH-SPECS & ID1=DIS2 LIMITS "20" "100" EO-CONV-OPTI STREAM-REPOR MOLEFLOW

Stream Variables BOT1 BOT2 DIS1 DIS2 FEED------------------------

STREAM ID BOT1 BOT2 DIS1 DIS2 FEEDFROM : D1 D2 D1 D2 ----TO : ---- ---- D2 ---- D1

SUBSTREAM: MIXEDPHASE: LIQUID LIQUID LIQUID LIQUID LIQUIDCOMPONENTS: LBMOL/HR

ETHANOL 0.0 0.5000 25.0000 24.5000 25.0000PROPANOL 0.5000 49.0001 49.5000 0.5000 50.0000ISOBU-01 9.8000 0.2000 0.2000 0.0 10.0000N-BUT-01 15.0000 0.0 0.0 0.0 15.0000



ENTHALPY:BTU/LBMOL -1.3208+05 -1.2398+05 -1.2143+05 -1.1582+05 -1.2441+05


– 79 –

BTU/LB -1788.6308 -2066.0146 -2190.2920 -2498.7500 -2070.2178BTU/HR -3.3417+06 -6.1620+06 -9.0707+06 -2.8954+06 -1.2441+07



AVG MW 73.8456 60.0113 55.4391 46.3496 60.0959

b. Using the tower pressures determined in ‘a’, the numbers of trays and the reflux ratios are determined using the DSTWU subroutine in ASPEN PLUS, for splits specified to give the desired products. The towers have 41 and 23 stages and reflux ratios of 2.39 and 3.64. The results below can be reproduced using the file DSTWU.BKP.

ASPEN PLUS Program – paragraphs that differ from above.

TITLE 'DESIGN CALCULATIONS'

BLOCK D1 DSTWU PARAM LIGHTKEY=1-PRO-01 RECOVL=0.99 HEAVYKEY=ISOBU-01 & RECOVH=0.02 PTOP=20. PBOT=20. RDV=0.0 RR=-1.3 BLOCK D2 DSTWU PARAM LIGHTKEY=ETHAN-01 RECOVL=0.98 HEAVYKEY=1-PRO-01 & RECOVH=0.0101 PTOP=20. PBOT=20. RR=-1.3


BLOCK: D1 MODEL: DSTWU-----------------------------

*** INPUT DATA ***HEAVY KEY COMPONENT ISOBU-01RECOVERY FOR HEAVY KEY 0.020000LIGHT KEY COMPONENT 1-PRO-01RECOVERY FOR LIGHT KEY 0.99000TOP STAGE PRESSURE (PSI ) 20.0000BOTTOM STAGE PRESSURE (PSI ) 20.0000REFLUX RATIO -1.30000DISTILLATE VAPOR FRACTION 0.0

*** RESULTS ***DISTILLATE TEMP. (F ) 207.805BOTTOM TEMP. (F ) 251.098MINIMUM REFLUX RATIO 1.83652ACTUAL REFLUX RATIO 2.38747MINIMUM STAGES 22.2947ACTUAL EQUILIBRIUM STAGES 40.9995NUMBER OF ACTUAL STAGES ABOVE FEED 18.5858DIST. VS FEED 0.74700CONDENSER COOLING REQUIRED (BTU/HR ) 4,381,070.NET CONDENSER DUTY (BTU/HR ) -4,381,070.REBOILER HEATING REQUIRED (BTU/HR ) 4,409,900.NET REBOILER DUTY (BTU/HR ) 4,409,900.

BLOCK: D2 MODEL: DSTWU-----------------------------

*** INPUT DATA ***HEAVY KEY COMPONENT 1-PRO-01RECOVERY FOR HEAVY KEY 0.010100LIGHT KEY COMPONENT ETHAN-01RECOVERY FOR LIGHT KEY 0.98000


– 80 –

TOP STAGE PRESSURE (PSI ) 20.0000BOTTOM STAGE PRESSURE (PSI ) 20.0000REFLUX RATIO -1.30000DISTILLATE VAPOR FRACTION 0.0

*** RESULTS ***DISTILLATE TEMP. (F ) 187.935BOTTOM TEMP. (F ) 221.633MINIMUM REFLUX RATIO 2.80216ACTUAL REFLUX RATIO 3.64280MINIMUM STAGES 12.1016ACTUAL EQUILIBRIUM STAGES 22.2106NUMBER OF ACTUAL STAGES ABOVE FEED 11.6852DIST. VS FEED 0.33467CONDENSER COOLING REQUIRED (BTU/HR ) 1,918,790.NET CONDENSER DUTY (BTU/HR ) -1,918,790.REBOILER HEATING REQUIRED (BTU/HR ) 1,932,040.NET REBOILER DUTY (BTU/HR ) 1,932,040.

c. Using the design determined in ‘a’ and ‘b’, the MESH equations are solved using the RADFRAC subroutine in ASPEN PLUS. The results below can be reproduced using the file RADFRAC.BKP. Note that the reflux ratio in the second column is increased using an internal design specification to achieve a molar flow rate of n-pentanol in the distillate of 0.5 lbmole/hr. The reflux ratio is increased from 3.64 to 4.28.

ASPEN PLUS Program – paragraphs that differ from above.

TITLE 'RADFRAC SIMULATION'

BLOCK D1 RADFRAC PARAM NSTAGE=41 COL-CONFIG CONDENSER=TOTAL FEEDS FEED 19 PRODUCTS DIS1 1 L / BOT1 41 L P-SPEC 1 20. COL-SPECS DP-COL=0. MOLE-D=74.7 MOLE-RR=3.65 SC-REFLUX DEGSUB=0. BLOCK D2 RADFRAC PARAM NSTAGE=23 COL-CONFIG CONDENSER=TOTAL FEEDS DIS1 12 PRODUCTS DIS2 1 L / BOT2 23 L P-SPEC 1 20. COL-SPECS DP-COL=0. MOLE-D=25. MOLE-RR=3.64 SC-REFLUX DEGSUB=0. SPEC 1 MOLE-FLOW 0.5 COMPS=1-PRO-01 STREAMS=DIS2 VARY 1 MOLE-RR 3.6 8.

Stream Variables

BOT1 BOT2 DIS1 DIS2 FEED------------------------STREAM ID BOT1 BOT2 DIS1 DIS2 FEEDFROM : D1 D2 D1 D2 ----TO : ---- ---- D2 ---- D1


– 81 –

SUBSTREAM: MIXEDPHASE: LIQUID LIQUID LIQUID LIQUID LIQUIDCOMPONENTS: LBMOL/HR

ETHAN-01 1.7690-08 0.5000 25.0000 24.5000 25.00001-PRO-01 0.3762 49.1238 49.6238 0.5000 50.0000ISOBU-01 9.9239 7.6048-02 7.6055-02 6.6135-06 10.0000N-BUT-01 14.9999 1.1262-04 1.1262-04 1.2194-10 15.0000



ENTHALPY:BTU/LBMOL -1.3213+05 -1.2396+05 -1.2141+05 -1.1582+05 -1.2441+05BTU/LB -1787.5949 -2066.7655 -2190.8725 -2498.7491 -2070.2178BTU/HR -3.3429+06 -6.1607+06 -9.0693+06 -2.8954+06 -1.2441+07



AVG MW 73.9142 59.9763 55.4158 46.3496 60.0959


BLOCK: D1 MODEL: RADFRAC-------------------------------

INLETS - FEED STAGE 19OUTLETS - DIS1 STAGE 1

BOT1 STAGE 41

**** COL-SPECS ****

MOLAR VAPOR DIST / TOTAL DIST 0.0MOLAR REFLUX RATIO 3.65000MOLAR DISTILLATE RATE LBMOL/HR 74.7000DIST + REFLUX DEG SUBCOOLED F 0.0

*** COMPONENT SPLIT FRACTIONS ***

OUTLET STREAMS--------------

DIS1 BOT1COMPONENT:ETHAN-01 1.0000 .70758E-091-PRO-01 .99248 .75233E-02ISOBU-01 .76055E-02 .99239N-BUT-01 .75079E-05 .99999

*** SUMMARY OF KEY RESULTS ***

TOP STAGE TEMPERATURE F 207.785BOTTOM STAGE TEMPERATURE F 251.236TOP STAGE LIQUID FLOW LBMOL/HR 272.655BOTTOM STAGE LIQUID FLOW LBMOL/HR 25.3000TOP STAGE VAPOR FLOW LBMOL/HR 0.0BOTTOM STAGE VAPOR FLOW LBMOL/HR 339.834MOLAR REFLUX RATIO 3.65000MOLAR BOILUP RATIO 13.4322CONDENSER DUTY (W/O SUBCOOL) BTU/HR -6,046,320.REBOILER DUTY BTU/HR 6,075,370.DIST + REFLUX SUBCOOLED TEMP F 207.785


– 82 –

SUBCOOLED REFLUX DUTY BTU/HR 0.0

ENTHALPYSTAGE TEMPERATURE PRESSURE BTU/LBMOL HEAT DUTY

F PSI LIQUID VAPOR BTU/HR

1 207.78 20.000 -0.12141E+06 -0.10277E+06 -.60463+07SUBC 207.78 20.000 -0.12141E+06

2 213.04 20.000 -0.12249E+06 -0.10400E+063 216.05 20.000 -0.12305E+06 -0.10477E+06

17 220.75 20.000 -0.12449E+06 -0.10608E+0618 221.49 20.000 -0.12477E+06 -0.10622E+0619 222.55 20.000 -0.12513E+06 -0.10641E+0620 224.14 20.000 -0.12542E+06 -0.10690E+0640 249.40 20.000 -0.13235E+06 -0.11469E+0641 251.24 20.000 -0.13213E+06 -0.11449E+06 .60754+07

STAGE FLOW RATE FEED RATE PRODUCT RATELBMOL/HR LBMOL/HR LBMOL/HR

LIQUID VAPOR LIQUID VAPOR MIXED LIQUID VAPOR1 272.7 0.0000E+00

SUBC 272.7 74.70002 271.1 347.43 270.5 345.8

17 268.9 344.018 268.4 343.6 .20341-0319 368.2 343.1 99.999820 368.1 342.940 365.1 340.541 25.30 339.8 25.3000

Block D1: Liquid Composition Profiles

Stage

X (m

ole

frac)

1 6 11 16 21 26 31 36 41

0.2

0.4

0.6

0.8

1

ETHAN-011-PRO-01ISOBU-01N-BUT-01

BLOCK: D2 MODEL: RADFRAC-------------------------------

INLETS - DIS1 STAGE 12OUTLETS - DIS2 STAGE 1

BOT2 STAGE 23

**** COL-SPECS ****

MOLAR VAPOR DIST / TOTAL DIST 0.0MOLAR REFLUX RATIO 3.64000MOLAR DISTILLATE RATE LBMOL/HR 25.0000DIST + REFLUX DEG SUBCOOLED F 0.0


– 83 –

*** COMPONENT SPLIT FRACTIONS ***

OUTLET STREAMS--------------

DIS2 BOT2COMPONENT:ETHAN-01 .98000 .20000E-011-PRO-01 .10076E-01 .98992ISOBU-01 .86957E-04 .99991N-BUT-01 .10828E-05 1.0000

*** SUMMARY OF KEY RESULTS ***

TOP STAGE TEMPERATURE F 187.935BOTTOM STAGE TEMPERATURE F 221.593TOP STAGE LIQUID FLOW LBMOL/HR 107.050BOTTOM STAGE LIQUID FLOW LBMOL/HR 49.7000TOP STAGE VAPOR FLOW LBMOL/HR 0.0BOTTOM STAGE VAPOR FLOW LBMOL/HR 124.782MOLAR REFLUX RATIO 4.28199MOLAR BOILUP RATIO 2.51071CONDENSER DUTY (W/O SUBCOOL) BTU/HR -2,180,430.REBOILER DUTY BTU/HR 2,193,610.DIST + REFLUX SUBCOOLED TEMP F 187.935SUBCOOLED REFLUX DUTY BTU/HR 7.60648

ENTHALPYSTAGE TEMPERATURE PRESSURE BTU/LBMOL HEAT DUTY

F PSI LIQUID VAPOR BTU/HR

1 187.93 20.000 -0.11582E+06 -99230. -.21804+07SUBC 187.93 20.000 -0.11582E+06 7.6064

2 188.46 20.000 -0.11600E+06 -99304.3 189.31 20.000 -0.11630E+06 -99424.

10 206.29 20.000 -0.12107E+06 -0.10245E+0611 208.05 20.000 -0.12146E+06 -0.10283E+0612 209.28 20.000 -0.12173E+06 -0.10311E+0613 210.82 20.000 -0.12204E+06 -0.10346E+0622 221.26 20.000 -0.12390E+06 -0.10620E+0623 221.59 20.000 -0.12396E+06 -0.10630E+06 .21936+07

STAGE FLOW RATE FEED RATE PRODUCT RATELBMOL/HR LBMOL/HR LBMOL/HR

LIQUID VAPOR LIQUID VAPOR MIXED LIQUID VAPOR1 107.0 0.0000E+00

SUBC 107.0 25.00002 106.8 132.03 106.4 131.8

10 101.7 127.111 101.5 126.7 .89755-0512 175.9 126.5 74.699913 175.6 126.222 174.5 124.823 49.70 124.8 49.7000


– 84 –

Block D2: Liquid Composition Profiles

Stage

X (m

ole

frac)

1 3 5 7 9 11 13 15 17 19 21 23

0.2

0.4

0.6

0.8

1

ETHAN-011-PRO-01ISOBU-01N-BUT-01


– 85 –

Exercise D.2 Solution using HYSYS.Plant

Solution reproduced in: DISTIL_EX_2.hsc

Based upon the specifications, the desired product streams (in kgmol/hr) are determined by material balance:

FEED D1 B1 Benzene 12.5 12.50 - Toluene 22.5 22.275 0.2250 o-Xylene 37.5 0.2250 37.275

n-PBenzene 27.5 - 27.50 Total 100.0 35.00 65.00

a. In HYSYS.Plant, the column pressures are determined using the Component

Splitter, adjusting the distillate pressure to achieve distillate bubble points at 50°C, with lower bounds of 20 psia to avoid vacuum operation. Note that due to volatiles in the overhead, the column pressure is dictated by this lower bound.

Component Splitter: X-100 PARAMETERS Stream Specifications Overhead Pressure: 20.00 psia Overhead Vapor Fraction: 0.00 Bottoms Pressure: 20.00 psia Bottoms Vapor Fraction: 0.00 SPLITS Component Fraction To Overhead Component Overhead Fraction Benzene 1 Toluene 0.99 PROPERTIES


– 86 –

F1 Overall Liquid Phase Vapor Phase Vapour/Phase Fraction 0 1 0 Temperature: (C) 134.6 134.6 134.6 Pressure: (psig) 5.304 5.304 5.304 Molar Flow (kgmole/h) 100 100 0 Mass Flow (kg/h) 1.03E+04 1.03E+04 0 Liquid Volume Flow (m3/h) 11.82 11.82 0 Molar Enthalpy (kJ/kgmole) 1.06E+04 1.06E+04 6.41E+04 Mass Enthalpy (J/kg) 1.03E+05 1.03E+05 6.88E+05 Molar Entropy (kJ/gmole-C) 3.66E-02 3.66E-02 6.85E-02 Mass Entropy (kJ/g-C) 3.54E-04 3.54E-04 7.35E-04 Heat Flow (kJ/h) 1.06E+06 1.06E+06 0 D1 Overall Liquid Phase Vapor Phase Vapour/Phase Fraction 0 1 0 Temperature: (C) 107.7 107.7 107.7 Pressure: (psig) 5.304 5.304 5.304 Molar Flow (kgmole/h) 35 35 0 Mass Flow (kg/h) 3053 3053 0 Liquid Volume Flow (m3/h) 3.493 3.493 0 Molar Enthalpy (kJ/kgmole) 3.81E+04 3.81E+04 7.68E+04 Mass Enthalpy (J/kg) 4.37E+05 4.37E+05 9.11E+05 Molar Entropy (kJ/gmole-C) -7.86E-02 -7.86E-02 -5.09E-03 Mass Entropy (kJ/g-C) -9.01E-04 -9.01E-04 -6.04E-05 Heat Flow (kJ/h) 1.33E+06 1.33E+06 0 B1 Overall Liquid Phase Vapor Phase Vapour/Phase Fraction 0 1 0 Temperature: (C) 161.4 161.4 161.4 Pressure: (psig) 5.304 5.304 5.304 Molar Flow (kgmole/h) 65 65 0 Mass Flow (kg/h) 7283 7283 0 Liquid Volume Flow (m3/h) 8.327 8.327 0 Molar Enthalpy (kJ/kgmole) -261.3 -261.3 3.76E+04 Mass Enthalpy (J/kg) -2332 -2332 3.39E+05 Molar Entropy (kJ/gmole-C) 9.96E-02 9.96E-02 0.1951 Mass Entropy (kJ/g-C) 8.89E-04 8.89E-04 1.76E-03 Heat Flow (kJ/h) -1.70E+04 -1.70E+04 0

d. Using the tower pressures determined in ‘a’, the numbers of trays and the reflux ratios are determined using short-cut column in HYSYS.Plant, for splits specified to give the desired products. The minimum number of trays is 13. For 1.3Rmin, the design calls for 26 trays, with feed entering on the 13th tray, with a reflux ratio of 2.206.


– 87 –

Shortcut Column: T-100 Component Mole Fraction Light Key Toluene 3.46E-03 Heavy Key o-Xylene 6.43E-03 Pressures (psig) Reflux Ratios Condenser Pressure 20 External Reflux Ratio 2.206 Reboiler Pressure 20 Minimum Reflux Ratio 1.697 User Variables Results Summary Trays / Temperatures Flows Minimum # of Trays 12.63 Rectify Vapour (kgmole/h) 112.2 Actual # of Trays 26.1 Rectify Liquid (kgmole/h) 77.21 Optimal Feed Stage 12.9 Stripping Vapour (kgmole/h) 112.2 Condenser Temperature (C) 129.3 Stripping Liquid (kgmole/h) 177.2 Reboiler Temperature (C) 185.2 Condenser Duty (kJ/h) -3.57E+06 Reboiler Duty (kJ/h) 3.82E+06

e. Using the design determined in ‘a’ and ‘b’, the MESH equations are solved using column in HYSYS.Plant. Note that a minor adjustment in the reflux ratio is made by the internal design specification to achieve the required component molar flow rates: 2.206 to 2.49.


– 88 –

Distillation: T-101 MONITOR

Specifications Summary Specified Value Current Value Wt. Error Wt. Tol. Abs. Tol. Active Estimate Toluene Recovery 0.99 0.99 1.06E-08 1.00E-02 1.00E-03 On On Xylene Recovery 0.994 0.994 8.59E-10 1.00E-02 1.00E-03 On On Distillate Rate 35.00 kgmole/h 35.00 kgmole/h 3.36E-05 1.00E-02 1.000 kgmole/h Off On Reflux Ratio 2.206 2.493 0.13 1.00E-02 1.00E-02 Off On Reflux Rate 87.25 kgmole/h 1.00E-02 1.000 kgmole/h Off On Btms Prod Rate 65.00 kgmole/h 1.00E-02 1.000 kgmole/h Off On SPECS Column Specification Parameters Toluene Recovery Draw: D3 @COL1 Flow Basis: Molar Components: Toluene Xylene Recovery Draw: B3 @COL1 Flow Basis: Molar Components: o-Xylene Distillate Rate Stream: D3 @COL1 Flow Basis: Molar

Reflux Ratio Stage: Condenser Flow Basis: Molar Liquid Specification: Reflux Rate Stage: Condenser Flow Basis: Molar Liquid Specification: Btms Prod Rate Stream: B3 @COL1 Flow Basis: Molar User Variables PROFILES General Parameters Sub-Flow Sheet: T-101 (COL1) Number of Stages: 26 SOLVER Column Solving Algorithm: HYSIM Inside-Out Solving Options Acceleration Parameters Maximum Iterations: 10000 Accelerate K Value & H Model Parameters: Off Equilibrium Error Tolerance: 1.000e-07 Heat/Spec Error Tolerance: 1.000e-007 Save Solutions as Initial Estimate: On Super Critical Handling Model: Simple K Trace Level: Low Init from Ideal K's: Off Damping Parameters Initial Estimate Generator Parameters Azeotrope Check: Off Iterative IEG (Good for Chemicals): Off Fixed Damping Factor: 1


– 89 –

PROPERTIES Properties : F3 @COL1 Overall Liquid Phase Vapour/Phase Fraction 0 1 Temperature: (C) 158.2 158.2 Pressure: (psig) 20 20 Molar Flow (kgmole/h) 100 100 Mass Flow (kg/h) 1.03E+04 1.03E+04 Liquid Volume Flow (m3/h) 11.82 11.82 Molar Enthalpy (kJ/kgmole) 1.59E+04 1.59E+04 Mass Enthalpy (J/kg) 1.54E+05 1.54E+05 Molar Entropy (kJ/gmole-C) 4.92E-02 4.92E-02 Mass Entropy (kJ/g-C) 4.76E-04 4.76E-04 Heat Flow (kJ/h) 1.59E+06 1.59E+06 Properties : D3 @COL1 Overall Vapour Phase Liquid Phase Vapour/Phase Fraction 0 0 1 Temperature: (C) 129.3 129.3 129.3 Pressure: (psig) 20 20 20 Molar Flow (kgmole/h) 35 0 35 Mass Flow (kg/h) 3053 0 3053 Liquid Volume Flow (m3/h) 3.493 0 3.493 Molar Enthalpy (kJ/kgmole) 4.19E+04 7.86E+04 4.19E+04 Mass Enthalpy (J/kg) 4.80E+05 9.29E+05 4.80E+05 Molar Entropy (kJ/gmole-C) -6.90E-02 -2.25E-03 -6.90E-02 Mass Entropy (kJ/g-C) -7.91E-04 -2.65E-05 -7.91E-04 Heat Flow (kJ/h) 1.47E+06 0 1.47E+06 Properties : B3 @COL1 Overall Vapour Phase Liquid Phase Overall Vapour Phase Liquid Phase Vapour/Phase Fraction 0 0 1 Temperature: (C) 185.2 185.2 185.2 Pressure: (psig) 20 20 20 Molar Flow (kgmole/h) 65 0 65 Mass Flow (kg/h) 7283 0 7283 Liquid Volume Flow (m3/h) 8.327 0 8.327 Molar Enthalpy (kJ/kgmole) 5852 4.19E+04 5852 Mass Enthalpy (J/kg) 5.22E+04 3.78E+05 5.22E+04 Molar Entropy (kJ/gmole-C) 0.1133 0.1996 0.1133 Mass Entropy (kJ/g-C) 1.01E-03 1.80E-03 1.01E-03 Heat Flow (kJ/h) 3.80E+05 0 3.80E+05


– 90 –

SUMMARY Tray Summary Flow Basis: Molar Reflux Ratio: 2.493 Temp. Pressure Liquid Vapour Feeds Draws Duties (C) (psig) (kgmole/h) (kgmole/h) (kgmole/h) (kgmole/h) (KJ/h) Condenser 129.3 20 87.25 35 L -3.89E6 1__Main TS 135 20 86.57 122.3 2__Main TS 138.3 20 86.1 121.6 3__Main TS 140.5 20 85.41 121.1 4__Main TS 142.4 20 84.38 120.4 5__Main TS 144.6 20 83.02 119.4 6__Main TS 147.4 20 81.48 118 7__Main TS 150.6 20 80.02 116.5 8__Main TS 154 20 78.81 115 9__Main TS 157.1 20 77.91 113.8 10__Main TS 159.7 20 77.23 112.9 11__Main TS 161.8 20 76.67 112.2 12__Main TS 163.6 20 76.16 111.7 13__Main TS 165.2 20 177.6 111.2 100 L 14__Main TS 168.8 20 178.7 112.6 15__Main TS 171.5 20 179.4 113.7 16__Main TS 173.8 20 179.9 114.4 17__Main TS 175.8 20 180.3 114.9 18__Main TS 177.4 20 180.7 115.4 19__Main TS 178.9 20 181.1 115.7 20__Main TS 180.1 20 181.4 116.1 21__Main TS 181 20 181.7 116.4 22__Main TS 181.8 20 181.9 116.7 23__Main TS 182.4 20 182.1 116.9 24__Main TS 183 20 182.1 117.1 25__Main TS 183.5 20 182.1 117.1 26__Main TS 184.2 20 181.9 117.1 Reboiler 185.2 20 116.9 65 L 4.14E+06


– 91 –

f. It is noted from the solution for (c) that the heat duty for the reboiler needed to meet the design specifications is 4.14E+06 KJ/h. If this value is reduced by 20%, that is, to 3.312+06 KJ/h, then clearly, this new specification is substituted for one of the others. It is not possible to meet both of the product specifications simultaneously for the lower level of reboiler heat duty. The following table indicates the impact of possible alternative design specifications accounting for fouling. Note that cases B and C, in which one of the two product specifications is maintained leads to a serious reduction in the recovery of the species whose specification is sacrifices. In contrast, with case D, it is possible to back off both of the specifications simultaneously, and to recover at least 93% of both of the desired products even when the reboiler is fouled (20% less duty).

Case Specification 1 Specification 2 Outcome

A Toluene recovery, 0.99

o-Xylene recovery, 0.994

Base case design, with RR = 2.493

B Reboiler Duty, 3.312+06 KJ/h


RR = 2.02, and toluene recovery drops to 0.862.

C Reboiler Duty, 3.312+06 KJ/h

Toluene recovery, 0.99


D Reboiler Duty, 3.312+06 KJ/h




– 92 –

Exercise D.3 Solution using ASPEN.PLUS

9.1 Mass balances Benzene 05.092.045.0700 ×+×=× BD Overall BD +=700 Solving: lbmole/hr 2.378 lbmole/hr, 8.321 == BD

lbmole/hr 724.1402.3321.8LDV

lbmole/hr 3.4028.32125.1=+=+=

=×=×= DRL

Tower dimensions Diameter Vapor density – assume ideal gas at highest temperature = 227°F

lbmolelb92

ftlbmole 001993.0

R687Rlbmole

atm ft0.7302

atm 133 ×=

°×°

==RTP

vρ

= 0.18343ft

lb

Flooding velocity – see Example 10.2

981.0 20

2.18 20

2.02.0

21

=

=

=

−=

σ

ρρρ

ST

V

VLFSTf

F

CFU

Note: σ is for toluene at 227°F

0341.0 7.48

1834.01.7243.402 2

121

≅

≅

=

L

V

VLFP

ρρ

Note: 48.7 is the density of toluene at 227°F

mm 2.457in

mm 4.25in 18 =×=TS

( ) ( ) 842.00341.0463.1755.04 2.45710127.80105.0 −−×+= eCF

sm0866.00761.00105.0 =+=

sft53.4

sm38.1

1834.01834.07.480866.0981.0

21

==

−

×=fU

sft85.353.485.0 =×=U


– 93 –

( )

21

3

21

sft85.3

ftlb1834.014.39.0

s 3600hr 1

lbmolelb92

hrlbmole1.7244

9.04

×××=

=

UVD

vπρ

m 86.1ft 09.6 == Height ( ) m 3.14ft 47105.11234 ==+−+=H Costs Column Eqs. (9.7) – FM = 1 (Fig. 9.3(c)) ( ) ( ) 640,38$86.13.14780,1 23.187.0 ==PC From Figs 9.3(c) and 9.3(d) – FP = 1, FBM = 4.5 CBM = 38,640 × 4.5 = $173,900 Trays Figure 9.4 – fq = 1, Nact = 23, FBM = 1.2 CBM = [193.04 + 22.72(1.86) + 60.38(1.86)2] (1.2)(23)(1) = $12,300 / tray Tower CBM = 173,900 + 12,300 = $186,200 Condenser

hr

Btu1092.9lbmole

Btu700,13hr

lbmole1.724 6×=×=CQ

( ) ( ) F98.72

120-17990-179ln

12017990179LM °=

−−−=∆T

226

m 3.126ft360,198.72100

1092.9==

××

=CA

Eqs. (9.5) ( ) 300,13$3.126450 7.0 ==PC Fig. 9.1(a) - 1=MF , Fig 9.1(b) - 1=PF , Fig. 9.1(c) 2.3=BMF =×= 2.3300,13BMC $42,600


– 94 –

Reboiler Overall energy balance BCDRF BHQDHQFH ++=+ FCBDR FHQBHHDQ −++= Let 0=DH (sat’d liq. at 179°F)

( ) F179227Flbmole

Btu5.43hr

lbmole2.3780 °−×°

×+=RQ

( )1792014.397001092.9 6 −×−×+

hr

Btu101.10 6×=

226

m 2.78ft 842000,12

101.10==

×=A

Eqs. (9.5) ( ) 510,9$2.78450 7.0 ==PC Fig. 9.1(a) - 1=MF , Fig 9.1(b) - 1=PF , Fig. 9.1(c) - 2.3=BMF 400,30$2.3510,9BM =×=C Reflux Accumulator

condensate ben. hrlb480,56

lbmolelb78

hrlbmole1.724 −=×=V

minft5.18

hrft110,1

lb 7.50ft 1

hrlb480,56

333

==×=

Note: 50.7 is the density of benzene at 179°F For a residence time = 5 min at half full: Volume 33 m 24.5ft 185105.18 ==×= For 4=DL :

m 19.124.5 31

31

=

=

=

ππVD

m 76.4=L Fig. 9.3(a) 000,6$=− PC 9.3(c) 1 ,1 ==− PM FF 9.3(d) 0.3BM =− F 000,18$0.3000,6BM =×=C


– 95 –

Reflux Pump – centrifugal

KW 7.1 slbft7376.0

W1s 3,600

hr 1ftin144

inlb50

lbft

7.501

lbmolelb78

hrlbmole3.4021

F2

2

2F

3

=

⋅×××

×××=∆= PmWs ρ&&

Figs. 5.49 – 5.51 – Ulrich 800,3$=PC , 2.3 ,1 ,1 BM === FFF PM 200,12$2.3800,3BM =×=C

Reboiler Pump – centrifugal hr

lbmole7003.402 +=+=− FLm&

hr

lbmole3.102,1=

W7376.0600,3

144507.48

1923.102,11××

×××=∆= PmWs ρ&&

6.5= KW Figs. 5.49 – 5.51 – Ulrich 500,5$=PC , 2.3 ,1 ,1 BM === FFF PM 600,17$2.3500,5BM =×=C Total Bare Module Cost Tower 186,200 Condenser 42,600 Reboiler 30,400 Reflux accumulator 18,000 Reflux pump 12,200 Reboiler pump 17,600 $307,000 - mid-1982 In mid-1999:

000,382$315392000,307 =×=TBMC


– 96 –

Total Permanent Investment CTBM = 382,000 Csite + Cserv = 0.1CTBM = 38,200 CDPI $420,200 Ccont = 0.15 CDPI = 63,000 CTDC $483,200 Cland = 0.02 CTDC = 9,700 Croyal = - Cstart = 0.10 CTDC = 48,300 CTPI $541,200 (mid-1999) IPE Results IPE Cost Charts in Chapter 9 – 1999 Costs

Distillation Tower

Diameter (ft) 6.0 6.09 Height (ft) 47.0 47.0 CP ($) 81,100 48,760×(392/315) = 60,700 CDML ($) 214,000 CBM ($) 186,200×(392/315) =231,700 Condenser Area (ft2) 555 1,360 CP ($) 15,000 13,300×(392/315) = 16,600 CDML ($) 57,100 CBM ($) 42,600×(392/315) = 53,000 Reboiler Area (ft2) 1,332.8 842 CP ($) 26,900 9,510×(392/315) = 11,800 CDML ($) 87,700 CBM ($) 30,400×(392/315) =37,800 Reflux Accumulator Volume (gal) 719.8 1,384


– 97 –

Diameter (ft) 3.5 3.9 Height (ft) 10 15.6 CP ($) 10,000 6,000×(392/315) = 7,500 CDML ($) 70,500 CBM ($) 18,000×(392/315) =22,400 Reflux Pump Power (KW) 2.2 1.7 CP ($) 3,400 3,800×(392/315) = 4,700 CDML ($) 22,600 CBM ($) 12,200×(392/315) =15,200 Reboiler Pump Power (KW) 7.5 5.6 CP ($) 4,500 5,500×(392/315) = 6,800 CDML ($) 32,100 CBM ($) 17,600×(392/315) =21,900

The equipment sizes and purchased costs are comparable with the exception of the reboiler. IPE does not design for the heat flux of 12,000 Btu/hr ft2. IPE estimates the direct materials and labor costs, CDML, for each equipment item. These estimates do not include the indirect project expenses, while the bare module factors from the cost charts include these expenses. Note, however, that the IPE estimates of CDML are considerably higher than CBM for the reboiler and reflux accumulator.

Total Permanent Investment The total permanent investment is calculated in the table below. Note

that the purchased equipment cost, $145,800, is obtained from line 1 of the Contract Summary in the IPE Capital Estimate Report. The total direct materials and labor costs are obtained from line 11, $450,300 and $146,500, respectively. These sum to CDML = $596,800. The direct installation cost is obtained by difference. The material and manpower costs associated with G&A Overhead and Contract Fees are obtained by adding the entries on lines 13 and 14; that is, $52,200 . The Contractor Engineering and Indirect Costs are obtained from line 15.


– 98 –

IBL (Inside Battery Limits)

Cost $ Source

Purchased Equipment Cost 145,800 IPE Equipment List Direct Installation Cost 451,000 By difference

Total Direct Materials and Labor Cost, CDML =CDI 596,800 IPE Contract Summary

Pipe Racks (10% of CDML) 59,700 Recommended by Instructor Sewers/Sumps (10% of CDML) 59,700 Recommended by

Instructor Mat’l and Labor G&A Overhead and Contract Fees 52,200 IPE Contract Summary Contractor Engineering 390,400 IPE Contract Summary Indirects 358,900 IPE Contract Summary IBL Total Bare Module Cost, CTBM 1,517,700


– 99 –

OBL (Outside Battery Limits)

Site Preparation & Service Facil. (10% of CTBM) 151,800 Allocated Costs for Utilities 0 Storage 0 Environmental 0 OBL Total 151,800

Direct Permanent Investment, CDPI 1,669,500 Contingencies (15% of CDPI) 250,400

Total Depreciable Capital, CTDC 1,919,900 Land (2% of CTDC) 38,400 Royalty 0 Start Up (10% of CTDC) 192,000 Total Permanent Investment, CTPI 2,150,300

Comparison of Results Using the cost charts in Chapter 9, the total bare module cost, CTBM =

$382,000, as compared with the IPE estimate for the total direct materials and labor cost of $596,800. This is partially due to the increase in reboiler area due to IPE’s inability to design for a heat flux of 12,000 Btu/hr ft2. The remaining difference is likely due to IPE’s detailed estimates of installation costs.

Of greater consequence, the IPE estimate for the total permanent investment, CTPI = $2,150,300, is substantially greater than that obtained using the cost charts, $541,200. Although the IPE Project Type is Plant addition – suppressed infrastructure, the IPE estimates for the contractor engineering and indirect costs are substantial. These cause the total permanent investment to far exceed that computed using the cost charts. This is probably because the bare module factors in the cost charts are not sufficiently large to represent the contractor engineering and indirect costs. However, some of the IPE estimates may be large for this distillation plant, which has only six equipment items. When added to the costs for more typical plants, with an order-of-magnitude more equipment items, these large estimates would have a less significant impact on the total permanent investment.


– 100 –

Reactor Design HYSYS.Plant

The materials supporting a course in heat transfer assume that 2-3 hours of computer

laboratory time is allocated to the exercises. The multimedia includes a section that provides a self-paced overview on reactors in general and the models available in HYSYS.Plant in particular. The following sequence is suggested:

Session 1: In the first part of the exercise session, the student should review the entire section on Reactors in the multimedia. This consists of modules describing all of the reactor models available in HYSYS.Plant, each illustrated by an example application. The students should ensure that they have covered the modules describing the PFR and the CSTR.

Session 2: The tutorial Ammonia Converter Design should be reviewed, while at the same time,

the student should develop his/her version of the simulation using HYSYS.Plant.

To reinforce their acquired capabilities, students should be assigned a homework exercise. A typical exercise is provided.


– 101 –

Reactor Design ASPEN PLUS

The materials supporting a course in heat transfer assume that 2-3 hours of computer

laboratory time is allocated to the exercises. The multimedia includes a section that provides a self-paced overview on reactors in general and the models available in ASPEN PLUS in particular. The following sequence is suggested:

Session 1: In the first part of the exercise session, the student should review the entire section on Reactors in the multimedia. This consists of modules describing all of the reactor models available in ASPEN PLUS, each illustrated by an example application. The students should ensure that they have covered the modules describing the PFR and the CSTR.

Session 2: The tutorial Ammonia Converter Design should be reviewed, while at the same time,

the student should develop his/her version of the simulation using ASPEN PLUS.

To reinforce their acquired capabilities, students should be assigned a homework exercise. A typical exercise is provided.


– 102 –

Exercise E.1 Reactor Design Problem

Maleic anhydride is manufactured by the oxidation of benzene over vanadium pentoxide catalyst (Westerlink and Westerterp, 1988), with excess air. The following reactions occur:

Reaction 1: OH2 CO2 OHC O HC 22324229

66 ++→+ (1)

Reaction 2: OH CO4 3O OHC 222324 +→+ (2)

Reaction 3: OH3 CO6 O HC 222215

66 +→+ (3)

Since air is supplied in excess, the reaction kinetics are approximated as first-order rate laws:

A P B

C

r1 r2

r3

PA Ckr,Ckr 2211 == and ACkr 33 = (4)

In the above, A is benzene, P is maleic anhydride (the desired product), and B and C are the undesired byproducts (H2O and CO2), with kinetic rate coefficients in s-1:

[ ][ ]

[ ]

−=−=−=

RT00021 exp 26RT00030 exp 00070

RT00025 exp 3004

3

2

1

,k,,k

,,k (5)

In Eq. (5), the activation energies are in kcal/kgmol.

The objective of this exercise is to design a plug flow reactor to maximize the yield of MA, for a feed steam of 200 kgmol/hr of air (21 mol % O2 and 79 mol % N2) and 2 kgmol/hr of benzene, at 200 oC and 1.5 Bar. Assume a reactor diameter of 2 m, neglect pressure drops, and design for adiabatic operation.

a) For fixed reactor tube length of 7 m, define the optimum reactor feed temperature to

maximize MA yield (Hint: check values in the range 700-800 oC) b) Investigate the effect of both reactor tube length, in the range 5-15 m, and feed

temperature, in the range 700-800 oC, on the MA yield. Define the optimum combination of both of these variables.



– 103 –

Exercise E.1 Solution using HYSYS.Plant

Solution reproduced in: REACT_EX_1.hsc

a) The process is simulated using the Antoine equation for vapor pressure estimation (in the reaction conditions, the system is in the vapor phase, so that VLE calculations are not performed anyway). A PFD for the process is set up as below, noting that a heater, E-101, is installed to bring the reactor feed to the desired temperature.

The Databook is used to investigate the sensitivity of yield (computed as the ratio of the molar flow rate of MA in PRODUCTS and the molar flow rate of benzene in S-2, 2 kgmol/hr), and selectivity (computed as the ratio of MA in PRODUCTS and the molar flow rates in the same stream of the byproducts, H2O and CO2). A parametric run for a reactor of length 7 m is shown next.


– 104 –

b) It is noted that for a reactor tube length of 7 m, the optimal feed temperature appears to be 780 oC; here the yield is just over 22% and the selectivity is about 16%. An additional sensitivity analysis, testing the variation of both feed temperature and reactor tube length, gives the following result:

The peak in yield occurs approximately at a reactor tube length of 14 m, with a feed temperature of 710 oC. Complete results for these operating conditions are listed below.

Fluid Package: Basis-1 Property Package: Antoine Plug Flow Reactor: PFR-100 PARAMETERS Physical Parameters

Type : User Specified Pressure Drop: 0.0000 bar

Heat Transfer : Heating Type : Direct Q Value Energy Stream : Duty : 0.0000 kcal/h Dimensions Total Volume: 43.98 m3 Length: 14.00 m Diameter: 2.000 m Number of Tubes: 1 Wall Thickness: 5.000e-003 m Void Fraction: 1.0000 Void Volume: 43.98 m3 Reaction Info


– 105 –

Reaction Set: Global Rxn Set Initialize From: Current Integration Information

Number of Segments: 30 Minimum Step Fraction: 1.0e-06

Minimum Step Length: 1.4e-05 m

Length (m) Temperature (C)

0.233 712.90.7 715.9

1.167 719.11.633 722.3

2.1 725.72.567 729.23.033 732.9

3.5 736.83.967 740.84.433 745

4.9 749.55.367 754.25.833 759.1

6.3 764.46.767 769.97.233 775.9

7.7 782.28.167 7898.633 796.4

9.1 804.39.567 813

10.033 822.610.5 833.1

10.967 844.911.433 858.3

11.9 873.612.367 891.412.833 912.6

13.3 938.413.767 971.2


– 106 –

Mole Fractions Length (m) Oxygen CO2 H2O Benzene MaleicAnhydr Nitrogen 0.2333 0.2077 0.0001 0.0001 0.0098 0.0001 0.7822 0.7 0.2074 0.0002 0.0002 0.0098 0.0001 0.7822 1.167 0.2071 0.0004 0.0004 0.0097 0.0002 0.7822 1.633 0.2068 0.0005 0.0005 0.0097 0.0002 0.7823 2.1 0.2065 0.0007 0.0006 0.0096 0.0003 0.7823 2.567 0.2062 0.0008 0.0008 0.0095 0.0004 0.7823 3.033 0.2059 0.001 0.0009 0.0095 0.0004 0.7823 3.5 0.2056 0.0011 0.0011 0.0094 0.0005 0.7824 3.967 0.2052 0.0013 0.0012 0.0093 0.0006 0.7824 4.433 0.2048 0.0015 0.0014 0.0092 0.0006 0.7824 4.9 0.2044 0.0017 0.0016 0.0091 0.0007 0.7824 5.367 0.204 0.0019 0.0017 0.0091 0.0008 0.7825 5.833 0.2036 0.0021 0.0019 0.009 0.0009 0.7825 6.3 0.2031 0.0024 0.0021 0.0089 0.0009 0.7825 6.767 0.2026 0.0026 0.0024 0.0088 0.001 0.7825 7.233 0.2021 0.0029 0.0026 0.0087 0.0011 0.7826 7.7 0.2016 0.0032 0.0028 0.0086 0.0012 0.7826 8.167 0.201 0.0036 0.0031 0.0084 0.0013 0.7826 8.633 0.2003 0.004 0.0034 0.0083 0.0014 0.7826 9.1 0.1996 0.0044 0.0037 0.0082 0.0015 0.7827 9.567 0.1989 0.0048 0.004 0.0081 0.0016 0.7827 10.03 0.1981 0.0053 0.0043 0.0079 0.0017 0.7827 10.5 0.1971 0.0059 0.0047 0.0077 0.0018 0.7827 10.97 0.1961 0.0066 0.0052 0.0076 0.0019 0.7827 11.43 0.1949 0.0073 0.0056 0.0074 0.002 0.7827 11.9 0.1936 0.0082 0.0062 0.0072 0.0021 0.7827 12.37 0.1921 0.0093 0.0068 0.0069 0.0022 0.7827 12.83 0.1903 0.0106 0.0076 0.0066 0.0023 0.7827 13.3 0.188 0.0122 0.0085 0.0063 0.0023 0.7826 13.77 0.1852 0.0144 0.0096 0.0059 0.0024 0.7825

PROPERTIES S-2 Overall Vapour Phase Vapour/Phase Fraction 1 1 Temperature: (C) 710 710 Pressure: (bar) 1.5 1.5 Molar Flow (kgmole/h) 202 202 Mass Flow (kg/h) 5926 5926 Liquid Volume Flow (m3/h) 6.847 6.847 Molar Enthalpy (kcal/kgmole) 5507 5507 Mass Enthalpy (kcal/kg) 187.7 187.7 Molar Entropy (kJ/kgmole-C) 189 189 Mass Entropy (kJ/kg-C) 6.442 6.442 Heat Flow (kcal/h) 1.11E+06 1.11E+06


– 107 –

PRODUCTS Overall Vapour Phase Vapour/Phase Fraction 1 1 Temperature: (C) 971.2 971.2 Pressure: (bar) 1.5 1.5 Molar Flow (kgmole/h) 201.9 201.9 Mass Flow (kg/h) 5926 5926 Liquid Volume Flow (m3/h) 6.872 6.872 Molar Enthalpy (kcal/kgmole) 5509 5509 Mass Enthalpy (kcal/kg) 187.7 187.7 Molar Entropy (kJ/kgmole-C) 197.9 197.9 Mass Entropy (kJ/kg-C) 6.742 6.742 Heat Flow (kcal/h) 1.11E+06 1.11E+06


– 108 –

Exercise E.1 Solution using ASPEN PLUS

a. The reactor is simulated using a 7 m tube length, with its feed temperature

varied between 700 and 800°C. The results below can be reproduced using the file MA.BKP.

MIX-100 E-101 PFR-100AIR

S-1 S-2 PRODUCTS

BENZENE

ASPEN PLUS Program

TITLE 'MALEIC ANHYDRIDE MANUFACTURE'IN-UNITS MET VOLUME-FLOW='cum/hr' ENTHALPY-FLO='MMkcal/hr' &

HEAT-TRANS-C='kcal/hr-sqm-K' PRESSURE=bar TEMPERATURE=C &VOLUME=cum DELTA-T=C HEAD=meter MOLE-DENSITY='kmol/cum' &MASS-DENSITY='kg/cum' MOLE-ENTHALP='kcal/mol' &MASS-ENTHALP='kcal/kg' HEAT=MMkcal MOLE-CONC='mol/l' &PDROP=bar

DEF-STREAMS CONVEN ALLDESCRIPTION "

General Simulation with Metric Units :C, bar, kg/hr, kmol/hr, MMKcal/hr, cum/hr.Property Method: NoneFlow basis for input: MoleStream report composition: Mole flow"



BENZENE C6H6 /MA C4H2O3 /WATER H2O /OXYGEN O2 /NITROGEN N2 /CO2 CO2

FLOWSHEETBLOCK MIX-100 IN=AIR BENZENE OUT=S-1BLOCK E-101 IN=S-1 OUT=S-2BLOCK PFR-100 IN=S-2 OUT=PRODUCTS

PROPERTIES IDEALSTREAM AIR

SUBSTREAM MIXED TEMP=200. PRES=1.5 MOLE-FLOW=200.MOLE-FRAC OXYGEN 0.21 / NITROGEN 0.79

STREAM BENZENESUBSTREAM MIXED TEMP=200. PRES=1.5 MOLE-FLOW=2.MOLE-FRAC BENZENE 1.

BLOCK MIX-100 MIXERPARAM PRES=1.5

BLOCK E-101 HEATERPARAM TEMP=700. PRES=1.5

BLOCK PFR-100 RPLUGPARAM TYPE=ADIABATIC LENGTH=7. <meter> DIAM=2. <meter> &

PRES=1.5REACTIONS RXN-IDS=R-1

EO-CONV-OPTISENSITIVITY S-1


– 109 –

DEFINE FMAPR MOLE-FLOW STREAM=PRODUCTS SUBSTREAM=MIXED &COMPONENT=MA

DEFINE FBENS2 MOLE-FLOW STREAM=S-2 SUBSTREAM=MIXED &COMPONENT=BENZENE

DEFINE FWATPR MOLE-FLOW STREAM=PRODUCTS SUBSTREAM=MIXED &COMPONENT=WATER

DEFINE FCO2PR MOLE-FLOW STREAM=PRODUCTS SUBSTREAM=MIXED &COMPONENT=CO2

F SELEC = FMAPR/(FWATPR + FCO2PR)F YIELD = FMAPR/FBENS2

TABULATE 1 "SELEC" COL-LABEL="SELEC"TABULATE 2 "YIELD" COL-LABEL="YIELD"VARY BLOCK-VAR BLOCK=E-101 VARIABLE=TEMP SENTENCE=PARAMRANGE LOWER="700" UPPER="800" INCR="5"

STREAM-REPOR MOLEFLOWREACTIONS R-1 POWERLAW

REAC-DATA 1 PHASE=VREAC-DATA 2 PHASE=VREAC-DATA 3 PHASE=VRATE-CON 1 PRE-EXP=4300. ACT-ENERGY=25000. <kcal/kmol>RATE-CON 2 PRE-EXP=70000. ACT-ENERGY=30000. <kcal/kmol>RATE-CON 3 PRE-EXP=26. ACT-ENERGY=21000. <kcal/kmol>STOIC 1 MIXED BENZENE -1. / OXYGEN -4.5 / MA 1. / CO2 &

2. / WATER 2.STOIC 2 MIXED MA -1. / OXYGEN -3. / CO2 4. / WATER &

1.STOIC 3 MIXED BENZENE -1. / OXYGEN -7.5 / CO2 6. / &

WATER 3.POWLAW-EXP 1 MIXED BENZENE 1. / MIXED OXYGEN 0. / MIXED &

MA 0. / MIXED CO2 0. / MIXED WATER 0.POWLAW-EXP 2 MIXED MA 1. / MIXED OXYGEN 0. / MIXED CO2 &

0. / MIXED WATER 0.POWLAW-EXP 3 MIXED BENZENE 1. / MIXED OXYGEN 0. / MIXED &

CO2 0. / MIXED WATER 0.

Stream Variables

AIR BENZENE PRODUCTS S-1 S-2----------------------------

STREAM ID AIR BENZENE PRODUCTS S-1 S-2FROM : ---- ---- PFR-100 MIX-100 E-101TO : MIX-100 MIX-100 ---- E-101 PFR-100

SUBSTREAM: MIXEDPHASE: VAPOR VAPOR VAPOR VAPOR VAPORCOMPONENTS: KMOL/HR

BENZENE 0.0 2.0000 1.7957 2.0000 2.0000MA 0.0 0.0 0.1817 0.0 0.0WATER 0.0 0.0 0.4312 0.0 0.0OXYGEN 42.0000 0.0 41.0127 42.0000 42.0000NITROGEN 158.0000 0.0 158.0000 158.0000 158.0000CO2 0.0 0.0 0.4991 0.0 0.0

TOTAL FLOW:KMOL/HR 200.0000 2.0000 201.9205 202.0000 202.0000KG/HR 5770.0794 156.2273 5926.3067 5926.3067 5926.3067CUM/HR 5245.2337 52.4523 1.1505+04 5297.6860 1.0896+04

STATE VARIABLES:TEMP C 200.0000 200.0000 754.7921 200.0000 700.0000PRES BAR 1.5000 1.5000 1.5000 1.5000 1.5000VFRAC 1.0000 1.0000 1.0000 1.0000 1.0000LFRAC 0.0 0.0 0.0 0.0 0.0SFRAC 0.0 0.0 0.0 0.0 0.0

ENTHALPY:KCAL/MOL 1.2291 24.3408 5.3789 1.4579 5.3768KCAL/KG 42.6010 311.6074 183.2702 49.6925 183.2702MMKCAL/HR 0.2458 4.8682-02 1.0861 0.2945 1.0861

ENTROPY:CAL/MOL-K 3.4826 -26.4277 9.4157 3.2968 8.9069CAL/GM-K 0.1207 -0.3383 0.3208 0.1124 0.3036

DENSITY:KMOL/CUM 3.8130-02 3.8130-02 1.7551-02 3.8130-02 1.8539-02


– 110 –

KG/CUM 1.1001 2.9785 0.5151 1.1187 0.5439AVG MW 28.8504 78.1136 29.3497 29.3382 29.3382


BLOCK: PFR-100 MODEL: RPLUG-----------------------------

*** INPUT DATA ***REACTOR TYPE:

ADIABATICVAPOR FLUID PHASE

REACTOR TUBE LENGTH METER 7.0000DIAMETER METER 2.0000

NUMBER OF REACTOR TUBES 1REACTOR VOLUME CUM 21.991

*** RESULTS ***

REACTOR DUTY MMKCAL/H 0.00000E+00RESIDENCE TIME HR 0.19685E-02REACTOR MINIMUM TEMPERATURE C 700.00REACTOR MAXIMUM TEMPERATURE C 754.79

*** RESULTS PROFILE (PROCESS STREAM) ***

LENGTH PRESSURE TEMPERATURE VAPOR FRAC RES-TIMEMETER BAR C HR

0.00000E+00 1.5000 700.00 1.0000 0.00000E+000.70000 1.5000 704.18 1.0000 0.20124E-031.4000 1.5000 708.57 1.0000 0.40166E-032.1000 1.5000 713.18 1.0000 0.60121E-032.8000 1.5000 718.06 1.0000 0.79980E-033.5000 1.5000 723.22 1.0000 0.99742E-034.2000 1.5000 728.70 1.0000 0.11940E-024.9000 1.5000 734.54 1.0000 0.13894E-025.6000 1.5000 740.81 1.0000 0.15837E-026.3000 1.5000 747.52 1.0000 0.17768E-027.0000 1.5000 754.79 1.0000 0.19685E-02

*** TOTAL MOLE FRACTION PROFILE (PROCESS STREAM) ***

LENGTH BENZENE MA WATER OXYGENMETER0.00000E+00 0.99010E-02 0.00000E+00 0.00000E+00 0.207920.70000 0.98209E-02 0.76249E-04 0.16503E-03 0.207551.4000 0.97375E-02 0.15496E-03 0.33777E-03 0.207172.1000 0.96503E-02 0.23630E-03 0.51903E-03 0.206762.8000 0.95588E-02 0.32064E-03 0.71030E-03 0.206343.5000 0.94628E-02 0.40802E-03 0.91208E-03 0.205884.2000 0.93616E-02 0.49880E-03 0.11262E-02 0.205404.9000 0.92548E-02 0.59306E-03 0.13535E-02 0.204895.6000 0.91416E-02 0.69119E-03 0.15963E-02 0.204346.3000 0.90214E-02 0.79328E-03 0.18559E-02 0.203757.0000 0.88931E-02 0.89979E-03 0.21357E-02 0.20311

LENGTH NITROGEN CO2METER

0.00000E+00 0.78218 0.00000E+000.70000 0.78221 0.17757E-031.4000 0.78224 0.36562E-032.1000 0.78226 0.56546E-032.8000 0.78229 0.77933E-033.5000 0.78233 0.10081E-024.2000 0.78236 0.12549E-024.9000 0.78239 0.15208E-025.6000 0.78242 0.18102E-02


– 111 –

6.3000 0.78245 0.21252E-027.0000 0.78249 0.24719E-02

The variation of the selectivity (ratio of maleic anhydride in the product stream to the sum of the water and CO2 in the product stream) and the yield (ratio of maleic anhydride in the product stream to the benzene in stream S-2) are graphed as a function of the reactor feed temperature:

Sensitivity S-1 Results Summary

VARY 1 E-101 PARAM TEMP C

700 725 750 775 800

0.1

0.15

0.2

0.25

00.

050.

10.

150.

2

SELEC YIELD

Note that for a reactor tube length of 7 m, the yield is a maximum at approximately 780°C. b. Results are not presented for the variation with the reactor length.

materials for participants – module instruction sequence ...dlewin/cache_workshop/workshop...

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