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PRO/II CASEBOOK

Air Separation Plant

ABSTRACT

The production of oxygen and nitrogen is an essential step in many chemical processes. Argon is also widelyused as an inerting gas. Computer simulation is an essential tool in the design of new air separation plantsand in modifying existing designs to meet new requirements.

This casebook demonstrates the use of PRO/II ®

in simulating an air separation process. The process hasnitrogen, oxygen and argon products. The simulation includes precooling the air and the use of a turbo-expander to produce the refrigeration. The process contains one material recycle and a number of thermalrecycles.

The process involves separating close boiling components at very low temperatures. Special thermodynam-ics are used in order to predict the separations accurately.

Casebook #5. Air Separation PlantRev. 0 February 1993

® PRO/II is a registered mark of SIMULATION SCIENCES INC.

© Copyright 1993, SIMULATION SCIENCES INC. ALL RIGHTS RESERVED.



SIMSCISimulation Sciences Inc.

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INTRODUCTION

Air separation is a commercially important process because both oxygen and nitrogen are essential materialsin today’s process industries. The main constituents of air are nitrogen and oxygen with a small amount ofargon. There are also traces of other rare gases but these are only present in ppm.

Oxygen

The steel industry is the major oxygen consumer using over 50% of all production. Oxygen is injected intofurnaces to give more efficient combustion than air.

The manufacture of chemicals uses another 20% of oxygen production. Of this, the manufacture of ethyleneoxide and acetylene take about 60%, while titanium dioxide, propylene oxide and vinyl acetate take another30% or more. The chemical industry uses a further 10% of oxygen production for partial oxidation processessuch as ammonia and methanol production.

Other uses for the remaining 20% of oxygen produced include: coal gasification and liquefaction; oxy-acety-lene welding; non-ferrous metallurgical processes; waste water treatment; and medical applications.

Nitrogen

Around 25% of nitrogen produced is used as a gaseous blanket to exclude oxygen and moisture. This may

be to reduce explosion hazards in hydrocarbon liquid storage or to avoid corrosion with liquids such as sulfuricacid.

In the metals industry, nitrogen is used as a blanket to prevent oxidation of the metal during smelting and tocool and purge molds of oxygen before pouring in the metal. The metals industry uses about 15% of nitrogenproduced.

Another 25% of nitrogen is used in the oil exploration industry. Gaseous nitrogen is used for enhanced oilrecovery to maintain pressure in the wells. Liquid nitrogen is used to fracture the production section of oilwells.

A rapidly growing area for the use of nitrogen is the electronics industry which uses about 15% of currentproduction. Very high purity nitrogen is used to provide an inert, dust-free, environment for the productionof complex miniature components.

Liquid nitrogen is widely used in cryogenic applications such as: food freezing and refrigeration; lowtemperature metal treatment; shrink fitting of parts; the storage of biological materials such as blood andorgans; and in cryosurgical procedures.

The nitrogen must be dry and have a low oxygen content. The amount of oxygen allowed depends on theapplication and some typical values are shown in Table 1.

Table 1Nitrogen Purities for Various Applications

Application Phase Purity (ppm Oxygen)

Refineries, hydrogen storage blanketing gas 5000

Pharmaceuticals, food and drink gas and liquid 1-200

Electronics gas and liquid 0.5-100

Well fracturing liquid 1-10

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Argon

The steel industry is probably the largest user of argon because of its inert properties. It is used to removeoxygen from molds in pressure die-casting and to protect the molten metal in continuous casting.

Argon is also widely used as a high-grade inerting medium in welding in order to prevent oxidation at thewelded joint. It must be used in preference to nitrogen in high quality aluminium welding to avoid the formation

of nitrides.Other uses of argon are: to fill light bulbs; gas chromatography; and as an inert medium or carrier gas in theproduction of semiconductors.

Manufacture

The vast majority of nitrogen, oxygen and argon is produced by the cryogenic separation of air. Nitrogen mayalso be separated from oxygen by the combustion of hydrocarbons in air. This process, which also producescarbon dioxide, does not produce the same high purity nitrogen as cryogenic separation and is much lesscommon today.

Oxygen can also be obtained by the electrolytic dissociation of water but this is expensive and virtually alloxygen is produced from air. A small amount of medium purity (90-95%) oxygen is produced by pressure

swing adsorption processes but cryogenic separation is the predominant method. This is because, in additionto allowing the production of large quantities of high purity oxygen, cryogenic processes can produce oxygenas a liquid.

Virtually all argon is produced from the cryogenic separation of air processes. A small amount of argon isalso produced as a by-product from ammonia synthesis. The purge drawn from the synthesis loop containsup to 6.5 mole per cent argon which may be recovered by cryogenic technology.

The configuration of a cryogenic separation process depends on which products are to be made togetherwith the phases and purities required. In small plants which supply only nitrogen or oxygen, the separationis usually carried out in a single distillation column. However, in larger plants, the use of a single column isgenerally inefficient.

Large plants must produce both nitrogen and oxygen in order to be economic and a double column

configuration is generally used. The only large single column process in commercial use produces mainlyliquid products. This is economic because the energy required for the liquefaction masks any inefficienciesin the gas separation. Double column processes employ pressure difference to allow energy integrationbetween the columns.

Argon has a boiling point between those of nitrogen and oxygen and so it builds up within the distillationcolumns. It is removed as a side draw into another distillation column where it is removed overhead. Theremaining gases are returned to the nitrogen/oxygen separation column. Because of the increasing demandfor argon, more and more air separation plants now incorporate argon recovery.

Most air separation plants can produce only small amounts (0-10%) of the products as liquid. If more liquidproducts are required, then additional refrigeration must be supplied. If the plant is to produce predominantlyliquid products, a liquefier can be integrated into the process at the design stage. Alternatively, a separateliquefier may be built so that it can be used to liquefy oxygen or nitrogen products as market conditions

require.The size of separation plants can vary considerably. Small plants will produce less than 0.1x10

6 kg/day of

oxygen whereas large plants may produce up to 2.2x106 kg/day.

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PROCESS OVERVIEW

The separation process in this casebook produces gaseous nitrogen, oxygen and argon products. Part ofthe oxygen is also produced as liquid. The plant produces approximately 1.5x10

6 kg/day of oxygen. The

flowsheet is illustrated in Figure 1.

The separation of oxygen and nitrogen is carried out in a double distillation column. This consists of twoseparate columns which are physically placed one on top of the other. The bottom column (HP Column)operates at higher pressure and its condenser is the reboiler for the upper, lower pressure, column (LPColumn). The HP Column bottom product is fed to the LP Column as feed and the reflux to the LP Columnis provided by the liquid top product from the HP Column.

The Argon Column takes a vapor side draw from the LP Column and returns its bottom product to the traybelow the draw. The argon product is drawn overhead.

Feedstocks and Products

Feed

Ignoring the impurities and traces of rare gases, the composition of dry air is as follows:

Figure 1Air Separation Flowsheet

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Table 2Air Composition

Component Mole %

Nitrogen 78.11

Argon 0.93

Oxygen 20.96

Products

Because the main uses of nitrogen are to exclude oxygen, the nitrogen product must contain very little oxygen.This is 0.5 to 5000 ppm depending on the purpose of the nitrogen. In this study, the amount of oxygen inthe nitrogen product must not exceed 10ppm. Impurities in the oxygen product are not as tightly controlledbut the purity must be greater than 99.5%.

Argon is also used to exclude oxygen and may also contain only a very small amounts of oxygen as animpurity. However, the relative volatility of argon to oxygen is about 1.1 at the top of the Argon Column andso it is not practical to remove all the oxygen by distillation. If the columns are efficient, the argon productcontains 0.5-1% nitrogen with an oxygen content of 1-2%. The argon is then further treated by catalyticdeoxygenation where the remaining oxygen is burned with hydrogen.

The feed and product compositions and conditions are shown in Table 3 in the results section at the end ofthis casebook.

Feed Pretreatment

The air used in the separation process must first be dried and other impurities removed. The impurities willinclude carbon monoxide, methane, ethane, ethylene and acetylene. Other impurities may be presentdepending on the location of the plant. There are two basic methods for removing the impurities before theseparation process:

– chilling with Freon followed by molecular sieve adsorption; – using reversing exchangers to alternately freeze and sublime the impurities.

Molecular sieves are generally used in small plants while large plants (over 0.5x106 kg/day) generally usereversing exchangers as these have a lower pressure loss. However, molecular sieves are now becomingmore common in larger plants.

Air Refrigeration

The normal boiling points of nitrogen and oxygen are 77K and 90K respectively. This means that the airmust be cooled to very low temperatures for the separation. The air feed is cooled as much as possible byexchange with the gaseous product streams but additional refrigeration is required to compensate for heatloss and the production of liquid products.

Small plants provide the refrigeration by compressing the air to high pressure (typically 150 atmospheres)and using the Joule-Thomson effect to cool it as it expands through a valve. In large plants, the compressioncosts become too high for this to be economic. These plants only compress the feed air to about 6-8atmospheres. The feed is split and about 10% is compressed, cooled and passed through a turbo-expander.The work produced by the expander is used to drive the compressor.

High Pressure Column

The main air feed enters the HP Column which operates at a pressure of about 6 atmospheres. The columnseparates nitrogen from argon and oxygen, producing a pure liquid nitrogen product overhead. This product

6



contains a few ppm oxygen with less than 0.2% argon. If a liquid nitrogen product is required from theprocess, it is drawn from the top of the HP Column.

The flowrate of the bottom product from the HP Column is about 60% of the feed rate and it contains about35% oxygen, 1% argon with the remainder being nitrogen.

Low Pressure Column

The LP Column operates at about 1.5 atmospheres and separates the nitrogen and oxygen to give pureproducts of each. The lower pressure gives better separation as it increases the relative volatility betweenthe nitrogen and oxygen. The overhead product is gaseous nitrogen with the same purity as the liquidnitrogen product from the HP Column. Both liquid and gaseous oxygen are drawn from the bottom of thecolumn. Because argon is removed from the side draw, the oxygen will be better than 99.5% pure.

The main oxygen feed to the LP Column is the bottom product from the HP Column. It is subcooled byexchange with the low pressure nitrogen product and is used to provide the cooling in the Argon Columncondenser. It then enters the LP Column with a liquid fraction in the region of 50%. The air from theturbo-expander is fed a few trays below the main feed.

The reflux in the LP Column is supplied by the liquid nitrogen product from the HP Column. This stream is subcooledby exchange with the low pressure nitrogen product and flashed through a valve to give a 90% liquid reflux.

Argon ColumnThe Argon Column feed is a vapor side draw from the bottom section of the LP Column and the argon vapor isremoved overhead. Because nitrogen is more volatile than argon, any nitrogen in the feed will leave in the argonproduct. It is therefore essential that the feed contains very little nitrogen. In order to ensure this, the draw fromthe LP Column is taken a few trays below the maximum argon concentration. The draw rate is about 20% of theair feed rate to the plant and only about 4% of the draw stream is removed as argon product.

ENERGY INTEGRATION

The process has a high level of energy integration as all the cooling is supplied from the feed pressure. Thereis no other refrigeration in the process. The main air feed is cooled to its dew point by exchange with theproducts. These are also heated by the product from the compressor.

The compressor is driven by the expander and so its work also derives from the feed stream pressure.

The pressures in the LP and HP Columns are set to ensure that the HP Column condenser can provide heatfor the LP Column reboiler. This means that the pressure in the HP Column must be sufficient to raise theoverhead temperature 2-3K above that of the LP Column bottoms.

The cooling in the Argon Column condenser is provided by the HP Column bottom product. The pressureis let down to ensure that its temperature is below the Argon Column top temperature.

The HP Column products are both liquid and supply the reflux in the LP Column. As the pressures arereduced, they will vaporize and this reduces the available reflux. The LP Column overhead product is usedto subcool these products and this reduces the vaporization.

MATERIAL RECYCLE

This flowsheet contains only one material recycle - between the LP and Argon Columns. The flow in thesestreams is large compared to the product produced in the Argon Column. It consists of about 90% oxygenwith the remainder mostly argon. The draw from the LP Column contains in the region of 0.01% nitrogen.

PROCESS SIMULATION

The “Simulation Flowsheet” differs from the process flowsheet in Figure 1 in that it includes stream identifiersand shows the way the simulation is solved. Parts of the simulation flowsheet are shown within the followingtext. The complete simulation flowsheet may be found in Appendix A.

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The full input for the simulation may be found in Appendix B. Extracts from the input are shown here toillustrate points of interest. For detailed explanations of all the input data, please refer to thePRO/II Keyword Input Manual , which may be obtained from SimSci (Addresses on Page 2).

General Data

There is a recycle between the LP Column and the Argon Column. Because the nitrogen concentration in

the recycle is small, the threshold mole fraction limit for trace components is reduced. Otherwise, the nitrogenbalance would not be checked in the convergence test.

In order to check the overall material balance, the PRINT MBAL option instructs PRO/II to print out an overallbalance over the flowsheet.

DIME METRIC,TEMP=K,PRES=ATM

PRINT MBAL,STREAM=PART,RATE=M,FRAC=M

TOLERANCE STREAM=,,1.0E-5

Component Data

All the components in the simulation are in the PRO/II databank.

Thermodynamic Data

The importance of accurate thermodynamic calculations for this simulation cannot be overemphasized. Theproduct purities are specified in terms of parts per million and temperature differences are only a few degrees.Any inaccuracies in the thermodynamic calculations must, therefore, have a significant effect on the results.

The Soave-Redlich-Kwong equation of state is suitable for the equilibrium, enthalpy and vapor densitycalculations for light gases such as those in this simulation. Ideal liquid densities are used as they give betterresults for these components than the default API method.

However, the boiling points of nitrogen and oxygen are only 13K apart and those of nitrogen and argon areonly separated by 3K. It is therefore essential to use binary interaction parameters obtained near those

conditions used in the process for each pair of components in order to obtain an accurate simulation model.The SIMSCI databank provides interaction parameters which cover a wide range of temperatures andpressures. For more accurate results, parameters should be derived for the specific temperature andpressure ranges in the simulation.

The best source of these parameters is always in-house data if these are available. Most companies whowork with these plants will have derived interaction parameters in the past. If not available in-house,parameters may be obtained from the literature or by regressing experimental vapor-liquid equilibrium data.The SimSci program, REGRESSTM, should be used for any regression as this ensures that the data arefitted to the same form of the equation of state used in the PRO/II program.

This simulation uses separate interaction data for the high and low pressure sections of the process. Thenitrogen/oxygen and the argon/oxygen interactions were obtained by regressing data for the specific pressurerange from Gmehling & Onken

1 using the REGRESS program. The low pressure nitrogen/argon parameter

is the Gmehling & Onken regressed value. For the high pressure column, the nitrogen/argon interaction isassumed ideal and is set to zero.

The input and part of the output for one of the REGRESS runs is shown in Appendix C.

1 Recommended Data of Selected Compounds and Binary Mixtures, Parts 1 and 2, 1987, DECHEMA

Chemistry Data Series, Vol, IV, Stephan, K., ed., DECHEMA, Germany.

8



The thermodynamic data input for the PRO/II simulation is shown below.

THERMODYNAMIC DATA

$ Low pressure data

METHOD SYSTEM=SRK,DENS(L)=IDEAL,SET=1,DEFAULT

KVAL(VLE)

SRK 1,3,-0.00694/& 1,2,0.0056/&

2,3,0.01574

$ High pressure data

METHOD SYSTEM=SRK,DENS(L)=IDEAL,SET=2

KVAL(VLE)

SRK 1,3,-0.01089/&

1,2,0.0/&

2,3,0.01697

The individual thermodynamic sets are specified in each unit operation by METHOD statements such as:

METHOD SET=2

which selects the high pressure data.

Stream Data

There is only one feed stream to the process which is the air feed. It comes from the purification stage wherethe water and carbon dioxide are removed. The temperature is, typically, 278K.

There is a recycle between the Argon Column and the LP Column and an initial estimate must be suppliedfor the return stream to the LP Column. This is necessary because the argon product flowrate is lowcompared to the return stream - about 4% of the feed.

If the return stream is not known, then its flowrate can be estimated as 20% of the feed air flowrate and it isabout 90% oxygen with the rest consisting of argon.

The stream data input is shown below. The important streams are given names to enable them to be easilyidentified on the output.

STREAM DATA

PROP STRM=1,TEMP=278,PRES=6,RATE=9386,COMP=78.11/0.93/20.96

$ RECYCLE FROM ARGON COLUMN - INITIAL ESTIMATE

PROP STRM=16,PHASE=L,PRES=1.32,COMP=0.0/10/90,RATE=1800

NAME 1,AIR FEED/8,HP BTMS/12,HP OVHD/15,ARG FEED/&

16,ARG BTMS/17,AR PRODUCT/20,N2 PRODUCT/23,O2 GAS/&

21,O2 LIQUID

Calculation Sequence

The best strategy for solving this flowsheet is to start with the distillation columns rather than following theair feed stream through the process because the cold stream temperatures into the exchanger are unknown.

9



The feed to the HP Column is set at its dew point and the air feed to the LP Column is 5K above its dewpoint.

The calculation then starts at the HP Column. After it is solved, the products are set to the correct pressuresand liquid fractions for the LP Column feeds and the LP and Argon Columns are solved along with the recycle.After the recycle, the E1E2 exchanger is solved to calculate the temperature of the nitrogen product enteringthe heat recovery exchanger. The HP Column condenser, LP Column reboiler and the Argon Column

condenser are now calculated in order to ensure that there are no temperature crossovers.

The feed exchanger can now be solved, along with the compressor and expander, in order to obtain theknown column feed conditions.

The flowsheet will be discussed in three separate sections:

– the column section

– the inter-column heat exchangers

– the heat recovery section

Column Section

The column section includes the feed splitter and the exchangers to set the feed conditions for both the HP

and LP Columns as well as the three distillation columns. The flowsheet is shown in Figure 2.

Figure 2Column Section Simulation Flowsheet

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Feed Temperatures

Ten percent of the pretreated air feed goes to the LP Column via the the compressor and expander. Theremainder goes to the HP Column. The splitter divides the air feed and the products are set to the columninlet conditions.

The feed to the HP Column is set to its dew point at the inlet pressure in a flash. An HX unit is used to set

the air to the LP Column to 5K above its dew point at a pressure of 1.4 atmospheres.

SPLITTER UID=SPL1,NAME=FEED SPLIT

FEED 1

PROD M=2,M=3

SPEC STRM=3,RATE,RATIO,STRM=1,VALUE=0.1

METHOD SET=2

FLASH UID=DEW

FEED 2

PROD V=5

DEW DP=0

HX UID=DTAD

HOT FEED=3,M=7,DP=4.6

OPER HDTAD=5

High Pressure Column

The HP Column has a total condenser and no reboiler. The air is fed to the base of the column and acts asthe reboil. The only variable is the condenser duty and this is varied to meet the 10 ppm oxygen specificationin the overhead product. The input is shown below.

COLUMN UID=HP,NAME=HP COLUMN PARA TRAY=44

FEED 5,44

PROD OVHD=12,4000,BTMS=8

TFLOW NET(V)=HPV,2

PSPEC TOP=5.8,DPCOL=.16

COND TYPE=BUBBLE

HEAT 1,1

ESTI REFLUX=5500,MODEL=CONV

SPEC STREAM=12,COMP=3,PPM,VALUE=10

VARI HEAT=1

METHOD SET=2,44

If the overhead product rate is not known, it can be estimated as 40-50% of the feed. The thermodynamicmethod for this column uses set 2 which is the high pressure data.

Low Pressure Column

The products from the HP Column are cooled by exchange with the overhead product before being fed tothe LP Column. The bottom product from the HP Column also provides the condenser duty in the ArgonColumn. When the LP Column is calculated, the overhead product and the argon condenser duty are notknown and so the exchangers cannot be modeled at this time. Instead, the column feeds are simply set to

11



the desired pressure and liquid fraction in heat exchanger models. The detailed exchangers are modeledlater when the distillation columns have been solved.

The LP Column input data are shown below together with the exchangers which set the feed conditions:

HX UID=E1

HOT FEED=12,M=14,DP=4.6 OPER HLFR=.9

HX UID=E2


OPER HLFR=.45

COLUMN UID=LP,NAME=LP COLUMN

PARA TRAY=69

FEED 14,1/11,28/7,32/16,45

TFLOW NET(L)=LPL,68

PROD OVHD=18,7800,BTMS=21,VDRAW=22,69,1800/15,44,1875

HEAT 1,69,8

PSPEC TOP=1.17,DPCOL=0.404 ESTI REFLUX=3500 MODEL=CONV

SPEC DUTY(1) RATIO COLUMN=HP DUTY(1) VALUE=-1


VARIABLES HEAT=1,DRAW=22

PLOT PROFILE,XCOMP=1,1/2,2/3,3,YCOMP=1,1/2,2/3,3

METHOD SET=1,69

The pure nitrogen product from the HP Column acts as the reflux and there is no condenser. This streamshould be the same purity as the required product from the LP Column. The HP Column bottom (oxygen)product enters in the top section of the column with the air feed from the turbo-expander a few trays lowerdown. The Argon Column draw and return are in the bottom section of the column.

The products are nitrogen overhead and oxygen from the base. The oxygen is mainly gaseous but a smallamount of liquid oxygen is also produced.

The reboiler for the LP Column is the condenser for the HP Column and its duty has already been calculatedin the HP Column to meet the nitrogen purity specification. It is, therefore, specified as equal to the LPcondenser duty but with a different sign to indicate that it is heating rather than cooling.

The most important specification on the LP Column is the nitrogen product purity which is set at 10 ppmoxygen. There are two side draws which could be varied in order to meet performance specifications - thefeed to the Argon Column and the gaseous oxygen product. This means that either one of these productrates is fixed or another parameter, such as the oxygen purity, must be specified.

In practice, it is not a good idea to specify the oxygen purity as this constrains the material balance verytightly. There is then a very high probability that the specifications will conflict. The best procedure is to

allow the oxygen purity to vary and fix the Argon Column draw stream. The gaseous oxygen product is thenvaried in order to reach solution.

Argon Column

The Argon Column is modeled with a bubble point condenser and no reboiler. The vapor draw from the LPColumn enters the base of the column and acts as the reboil. Because the argon product purity is controlledby the operation of the LP Column, a recovery specification is used on the Argon Column. A third of theargon in the feed is typically recovered overhead and the condenser duty can be varied in order to meet this.The expected argon product purity is in the region of 98%.

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The Argon Column input is shown below.

COLUMN UID=ARG,NAME=ARGON COLUMN

PARA TRAY=55

FEED 15,55

PROD OVHD=17,100,BTMS=16 TFLOW NET(V)=AV1,2

HEAT 1,1,-3

PSPEC TOP=1.15,DPCOL=0.17

PRINT PROP=BRIEF


COND TYPE=PARTIAL

SPEC STRE=17,COMP=2,RATE,RATIO,STRE=15,VALUE=0.3333

VARI HEAT=1

METHOD SET=1,55

Inter-column Heat Exchangers

Once the distillation columns have been solved, the exchangers between the HP and LP Columns can becalculated. The simulation flowsheet is shown in Figure 3. The exchangers E1 and E2 in the Column Sectionof the flowsheet are combined into the LNGHX unit E1E2. The valves are modeled separately. Steam 18is the nitrogen product from the LP Column and 12 and 8 are the HP Column products.

Exchangers E3 and E4 are the Argon and HP Column condensers. The streams AV1 and HPV are created

from the vapor flow into the condensers using the TFLOW statement. LPL is created from the liquid flow intothe LP Column reboiler which is the other side of the HP Column condenser. These exchangers are modeledin order to enable PRO/II to check that the temperature levels are correct - i.e. there are no crossovers.

The duty on the first stream in exchanger E1E2 is set equal to that calculated in E1 when setting the LPColumn feed condition. The duty on the second stream in E1E2 is defined as the duty of E2 minus the dutyof the Argon Column condenser. The condenser duty is actually negative so it is added to the E2 duty onthe DEFINE statement to give the cooling duty in E1E2.

Figure 3Inter-column Heat Exchangers

13



The duties of E3 and E4 are simply defined as the same as that of the corresponding column condenser. Iftemperature crossovers occur, PRO/II will automatically print an error message.

The input for these heat exchangers is shown below.

LNGHX UID=E1E2

HOT FEED=12,M=13 HOT FEED=8,M=9

COLD FEED=18,M=19

DEFINE DUTY(1) AS 1.0000 MULTIPLY HX=E1 DUTY

DEFINE DUTY(2) AS HX=E2 DUTY PLUS COLU=ARG DUTY(1)

VALVE UID=V2

FEED 9

PROD M=10

OPER DP=4.55

HX UID=E3,NAME=AR CONDENSER

COLD FEED=10,M=11A

HOT FEED=AV1,L=AL1 DEFINE DUTY AS -1.0000 MULTIPLY COLU=ARG DUTY(1)

HX UID=E4,NAME=HP CONDENSER $ .. AND LP REBOILER

COLD FEED=LPL,M=LPL1

HOT FEED=HPV,L=HPV1

DEFINE DUTY AS -1.0000 MULTIPLY COLU=HP DUTY(1)

Heat Recovery Section

The heat recovery section consists of the LNGHX exchanger and the compressor and turbo-expander. Thesimulation flowsheet is shown in Figure 4.

Figure 4Heat Recovery Simulation Flowsheet

14



Streams 2 and 3 are the air feeds. 5A and 7A correspond to the column feed streams 5 and 7 in the columnsection of the flowsheet. Streams 19 and 22 are the cold gaseous nitrogen and oxygen products which coolthe air feed.

There is an energy recycle round the three units in this section of the flowsheet and a controller is used tocalculate the temperature of stream 6 leaving the LNGHX exchanger. The input data are shown below.

COMPRESSOR UID=COM

FEED 3

PROD V=4

OPER EFF=82

DEFINE WORK AS EXPANDER=EXP,WORK,MULTIPLY 0.9

METHOD SET=2

LNGHX UID=LNG

HOT FEED=2,M=5A

HOT FEED=4,M=6,TEMP=160

COLD FEED=19,V=20

COLD FEED=22,V=23

DEFINE TEMP(1) AS STREAM=5,TEMP METHOD SET=2

EXPANDER UID=EXP

FEED 6

PROD V=7A

OPER PRES=1.4,EFF=85

CONTROLLER UID=CON

SPEC STREAM=7A,TEMP,RATIO,STREAM=7,VALUE=1,ATOL=0.01

VARI LNGHX=LNG,TEMP(2)

The compressor work is defined as 90% of that produced in the expander. However, when the compressoris first calculated, the expander work has not been determined. It is not possible to calculate the expanderfirst because the inlet pressure is determined by the compressor. This means that an iterative procedure isrequired and it is automatically converged by PRO/II.

The temperature of stream 5A leaving the LNGHX is defined as the same as the column feed stream 5. Thetemperature of stream 6 is not known. What is known is the temperature of stream 7A leaving the expander.The controller is therefore used to vary the temperature of stream 6 in order to set stream 7A at the sametemperature as stream 7.

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RESULTS

Column Section

The HP Column solves with a condenser duty of 10.46GCal/hr. The overhead product is 99.83% nitrogenwith the remainder mostly argon. The LP Column reboiler duty is the same as that of the HP Columncondenser. The nitrogen product contains slightly more argon than the HP Column product and is 99.72%

pure. The oxygen content is the same in both column products at the 10ppm which was specified .

7.6% of the oxygen is produced as liquid. The purity of the liquid and gas products are 99.7% and 99.6%respectively. These are both above the desired value of 99.5%.

The argon product is 97.5% pure with 1.9% oxygen and 0.6% nitrogen. The product rate is 3.2% of the feedfrom the LP Column. The condenser duty is 2.96GCal/hr.

Inter-Column Exchangers

All the exchangers solve correctly which confirms that there are no temperature crossovers. The nitrogeninto the HP Column condenser is at a temperature of 96.2K and the oxygen into the LP Column reboiler isat 94.8K. Because the streams are changing phase, there is very little temperature change through theexchanger.

The argon entering the Argon Column condenser is at 88.9K and is exchanging with the LP Column oxygenproduct. This oxygen stream is heated from 84.0K to 85.5K within the condenser.

The LP Column nitrogen product is heated from 79.1K to 96.3K in the LNGHX unit E1E2.

Heat Recovery Section

The work recycle between the expander and compressor is solved automatically within the controller loop.The controller solves in three iterations. The compressor increases the air pressure from 6 to 9 atmosphereswith an exit temperature of 320K. This is cooled in the LNGHX unit to 143K before entering the expander.It is then let down to the defined feed condition of 90K and 1.4 atmospheres.

Table 3

Process Feed and Products

Air Feed N2 Product O2 Liquid O2 Vapor Ar Product

Identifier 1 18 21 22 17

Phase Vapor Vapor Liquid Vapor Vapor

Mole Fractions

Nitrogen 0.7811 0.9972 6.2509-16 2.4174e-15 5.8832E-03

Argon 9.3000e-03 2.8307e-03 2.8807e-03 4.3811e-03 0.9754

Oxygen 0.2096 9.9998e-06 0.9971 0.9956 0.0187

Stream Conditions

Rate (Kmol/hr) 9386.0 7351.93 150.24 1824.19 59.59

Temperature (K) 278.0 79.1 94.8 94.8 88.9

Pressure (Atm) 6.00 1.17 1.57 1.57 1.15

16



APPENDIX AComplete Simulation Flowsheet

17



18



APPENDIX BPRO/II Input File

This file is available on floppy disk.

TITLE PROBLEM=AIR PLANT,PROJECT=CASEBOOK,USER=SIMSCI

DIME METRIC,TEMP=K,PRES=ATM PRINT MBAL,STREAM=PART,RATE=M,FRAC=M

TOLERANCE STREAM=,,1.0E-5

COMPONENT DATA

LIBID 1,NITROGEN/2,ARGON/3,OXYGEN

THERMODYNAMIC DATA

$ Low pressure data

METHOD SYSTEM=SRK,DENS(L)=IDEAL,SET=1,DEFAULT

KVAL(VLE)

SRK 1,3,-0.00694/*

1,2,0.0056/*

2,3,0.01574$ High pressure data

METHOD SYSTEM=SRK,DENS(L)=IDEAL,SET=2

KVAL(VLE)

SRK 1,3,-0.01089/*

1,2,0.0/*

2,3,0.01697

STREAM DATA

PROP STRM=1,TEMP=278,PRES=6,RATE=9386,COMP=78.11/0.93/20.96

$ RECYCLE FROM ARGON COLUMN - INITIAL ESTIMATE

PROP STRM=16,PHASE=L,PRES=1.32,COMP=0.0/10/90,RATE=1800

NAME 1,AIR FEED/8,HP BTMS/12,HP OVHD/15,ARG FEED/*

16,ARG BTMS/17,AR PRODUCT/20,N2 PRODUCT/23,O2 GAS/*

21,O2 LIQUID

UNIT OPERATIONS

$ ************** Column Section **************

SPLITTER UID=SPL1,NAME=FEED SPLIT

FEED 1

PROD M=2,M=3

SPEC STRM=3,RATE,RATIO,STRM=1,VALUE=0.1

METHOD SET=2

FLASH UID=DEW

FEED 2

PROD V=5

DEW DP=0

HX UID=DTAD


OPER HDTAD=5

19



COLUMN UID=HP,NAME=HP COLUMN

PARA TRAY=44

FEED 5,44


TFLOW NET(V)=HPV,2

PSPEC TOP=5.8,DPCOL=.16

COND TYPE=BUBBLE

HEAT 1,1



VARI HEAT=1

METHOD SET=2,44

HX UID=E1


OPER HLFR=.9

HX UID=E2


OPER HLFR=.45

COLUMN UID=LP,NAME=LP COLUMN

PARA TRAY=69

FEED 14,1/11,28/7,32/16,45

TFLOW NET(L)=LPL,68

PROD OVHD=18,7800,BTMS=21,VDRAW=22,69,1800/15,44,1875

HEAT 1,69,8


ESTI REFLUX=3500 MODEL=CONV

SPEC DUTY(1) RATIO COLUMN=HP DUTY(1) VALUE=-1


VARIABLES HEAT=1,DRAW=22 PLOT PROFILE,XCOMP=1,1/2,2/3,3,YCOMP=1,1/2,2/3,3

METHOD SET=1,69

COLUMN UID=ARG,NAME=ARGON COLUMN

PARA TRAY=55

FEED 15,55


TFLOW NET(V)=AV1,2

HEAT 1,1,-3


PRINT PROP=BRIEF


COND TYPE=PARTIAL SPEC STRE=17,COMP=2,RATE,RATIO,STRE=15,VALUE=0.3333

VARI HEAT=1

METHOD SET=1,55

20



$ ************** Inter-column Heat Exchangers **************

LNGHX UID=E1E2

HOT FEED=12,M=13

HOT FEED=8,M=9

COLD FEED=18,M=19

DEFINE DUTY(1) AS 1.0000 MULTIPLY HX=E1 DUTY

DEFINE DUTY(2) AS HX=E2 DUTY PLUS COLU=ARG DUTY(1)

VALVE UID=V2

FEED 9

PROD M=10

OPER DP=4.55

HX UID=E3,NAME=AR CONDENSER

COLD FEED=10,M=11A

HOT FEED=AV1,L=AL1

DEFINE DUTY AS -1.0000 MULTIPLY COLU=ARG DUTY(1)

HX UID=E4,NAME=HP CONDENSER $ .. AND LP REBOILER

COLD FEED=LPL,M=LPL1

HOT FEED=HPV,L=HPV1

DEFINE DUTY AS -1.0000 MULTIPLY COLU=HP DUTY(1)

$ ************** Heat Recovery Section **************

COMPRESSOR UID=COM

FEED 3

PROD V=4

OPER EFF=82

DEFINE WORK AS EXPANDER=EXP,WORK,MULTIPLY 0.9

METHOD SET=2

LNGHX UID=LNG

HOT FEED=2,M=5A

HOT FEED=4,M=6,TEMP=160

COLD FEED=19,V=20

COLD FEED=22,V=23

DEFINE TEMP(1) AS STREAM=5,TEMP

METHOD SET=2

EXPANDER UID=EXP

FEED 6

PROD V=7A

OPER PRES=1.4,EFF=85

CONTROLLER UID=CON

SPEC STREAM=7A,TEMP,RATIO,STREAM=7,VALUE=1,ATOL=0.01

VARI LNGHX=LNG,TEMP(2)

END

21



22



APPENDIX CRegression of Interaction Parameters

The REGRESS program input for the low pressure nitrogen/oxygen regression is shown below.

TITLE PROB=AIR PLANT,USER=SIMSCI

DIME SI,TEMP=K,PRES=ATM

COMPONENT DATA

LIBID 1,NITROGEN/2,ARGON/3,OXYGEN

DATA

SETN=1, COMP=1,3 $ N2-O2

FORMAT PTXY, DESC=LOW PRESSURE

0.540 75.0 0.6 0.8766

0.599 75.0 0.7 0.9130

0.654 75.0 0.8 0.9448

0.709 75.0 0.9 0.9735

0.767 75.0 1.0 1.0

0.540 80.0 0.2 0.5530

0.669 80.0 0.3 0.6686

0.765 80.0 0.4 0.7493

0.874 80.0 0.5 0.8107

0.977 80.0 0.6 0.8600

1.078 80.0 0.7 0.9017

1.176 80.0 0.8 0.9379

1.271 80.0 0.9 0.9703

1.367 80.0 1.0 1.0

1.132 85.0 0.3 0.6323

1.309 85.0 0.4 0.7198

1.482 85.0 0.5 0.7872

1.649 85.0 0.6 0.8425

REGRESS

DATA SETN=1

MODEL TYPE=SRK

FIX PARAM=2,VALUE=0.0

FIX PARAM=3,VALUE=0.0

END

The calculated interaction parameter is shown in the output below.

CALCULATION RESULTS - REGRESSION BLOCK 1:

1. MODEL PARAMETERS - FIXED AND REGRESSED:

I J KA(I,J) KB(I,J) KC(I,J) —— —— ————— ————— ————— 1 3 -0.006936 0.0000* 0.000*

TOTAL NUMBER OF REGRESSED PARAMETERS = 1

NOTE: * PARAMETER WAS HELD AS FIXED DURING THE REGRESSION.

23



The REGRESS program output also lists the experimental versus calculated values for temperature, pressureand vapor composition using the calculated interaction parameter. The table for the nitrogen vaporcomposition is shown below.

VAPOR COMPOSITION

COMPONENT : 1

EXPERIMENTAL CALCULATED DIFFERENCES PERCENT

0.876600 0.876592 -8.225441E-06 -0.000938

0.913000 0.912937 -0.000063 -0.006881 0.944800 0.944755 -0.000045 -0.004713

0.973500 0.973467 -0.000033 -0.003429 1.000000 1.000000 3.576279E-07 0.000036

0.553000 0.561165 0.008165 1.476460

0.668600 0.673396 0.004796 0.717360 0.749300 0.751643 0.002343 0.312628

0.810700 0.811204 0.000504 0.062149

0.860000 0.859490 -0.000510 -0.059327 0.901700 0.900532 -0.001168 -0.129541 0.937900 0.936712 -0.001188 -0.126638

0.970300 0.969534 -0.000766 -0.078961

1.000000 1.000000 1.192093E-07 0.000012 0.632300 0.641539 0.009239 1.461167

0.719800 0.724836 0.005036 0.699638 0.787200 0.789443 0.002243 0.284894

0.842500 0.842517 0.000017 0.002045

MAXIMUM DEVIATION : 0.009239 1.476460 AVERAGE ABSOLUTE DEVIATION : 0.002007 0.301490

24



APPENDIX DPRO/II Output

The following pages show selected parts of the output file from the air separation plant simulation. A completecopy of the output can be obtained from SimSci on floppy disk.

The order of the output is shown below:

Component Data ReprintThermodynamic Data ReprintPlant material balanceExpander EXPCompressor COMArgon Column condenser E3LNGHX unit LNGColumn summaries for:HP Column summaryLP Column summaryLP Column vapor compositions

Argon Column summaryMolar component fractions for all streams in the simulation

25



SIMULATION SCIENCES INC. R PAGE R-1

PROJECT CASEBOOK PRO/II VERSION 3.30 19-JAN VAX VMS PROBLEM AIR PLANT INPUT SIMSCI

COMPONENT DATA 02/01/93

==============================================================================

NO. COMPONENT NAME COMP. TYPE PHASE MOL. WEIGHT DENSITY

KG/M3 —- ———————- —————- ————— —————- —————- 1 NITROGEN LIBRARY VAP/LIQ 28.013 807.313

2 ARGON LIBRARY VAP/LIQ 39.948 679.329 3 OXYGEN LIBRARY VAP/LIQ 31.999 1126.378

NO. COMPONENT NAME NBP CRIT. TEMP. CRIT. PRES. CRIT. VOLM. K K ATM M3/KG-MOL

—- ——————— —————- ————— —————- —————- 1 NITROGEN 77.350 126.250 33.500 0.0901

2 ARGON 87.290 150.860 48.000 0.0745 3 OXYGEN 90.170 154.750 50.100 0.0764

NO. COMPONENT NAME ACEN. FACT. HEAT FORM. G FORM.

KCAL/KG-MOL KCAL/KG-MOL —- ——————— —————- —————- —————- 1 NITROGEN 0.04500 0.00 0.00

2 ARGON -0.00200 0.00 0.00 3 OXYGEN 0.01900 0.00 0.00

26



SIMULATION SCIENCES INC. R PAGE R-2

PROJECT CASEBOOK PRO/II VERSION 3.30 19-JAN VAX VMSPROBLEM AIR PLANT INPUT SIMSCI

THERMODYNAMIC DATA 02/01/93

==============================================================================

VLE K-VALUE DATA FOR SET ’1’

SRK PURE COMPONENT DATA

COMP CRITICAL CRITICAL ALPHA C1 C2 C3

TEMPERATURE PRESSURE TYPE DEG K ATM

—- ————— ————- —— ———— ————— ————- 1 126.25 33.50 1 0.5505 N/A N/A

2 150.86 48.00 1 0.4769 N/A N/A 3 154.75 50.10 1 0.5098 N/A N/A

SRK INTERACTION PARAMETERS

KIJ = A(I,J) + B(I,J)/T + C(I,J)/T**2

I J KA(I,J) KB(I,J) KC(I,J) UNITS FROM —- —- ————— ————- ————- ——— ———

1 2 5.600E-03 0.00 0.00 DEG K INPUT 1 3 -6.940E-03 0.00 0.00 DEG K INPUT

2 3 0.0157 0.00 0.00 DEG K INPUT

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

VLE K-VALUE DATA FOR SET ’2’

SRK PURE COMPONENT DATA

COMP CRITICAL CRITICAL ALPHA C1 C2 C3 TEMPERATURE PRESSURE TYPE

DEG K ATM —- —————- ————- ——- ————- ————- ————-

1 126.25 33.50 1 0.5505 N/A N/A 2 150.86 48.00 1 0.4769 N/A N/A

3 154.75 50.10 1 0.5098 N/A N/A

SRK INTERACTION PARAMETERS

KIJ = A(I,J) + B(I,J)/T + C(I,J)/T**2

I J KA(I,J) KB(I,J) KC(I,J) UNITS FROM

—- —- ————- ————- ————- ——- ——- 1 2 0.0000 0.00 0.00 DEG K INPUT

1 3 -0.0109 0.00 0.00 DEG K INPUT 2 3 0.0170 0.00 0.00 DEG K INPUT

27



SIMULATION SCIENCES INC. R PAGE P-1

PROJECT CASEBOOK PRO/II VERSION 3.30 19-JAN VAX VMSPROBLEM AIR PLANT OUTPUT SIMSCI

PLANT MATERIAL BALANCE 02/01/93

==============================================================================

FEED STREAMS: 1 8 12

3 2 HPV LPL AV1

PRODUCT STREAMS: 17 20 23 21 13 AL1

11A HPV1 LPL1

5A 7A

OVERALL PLANT MOLAR BALANCE

———————- KG-MOL/HR ——————— PERCENT

COMPONENT FEED +REACTION -PRODUCT =DEVIATION DEV ——————————- ————- ————— ————- ————— ———-

1 NITROGEN 30278.104 0.000 30278.094 0.000 0.00 2 ARGON 2212.035 0.000 2212.102 -0.067 0.00 3 OXYGEN 12334.989 0.000 12334.878 0.111 0.00

TOTAL 44825.129 0.000 44825.074 0.055 0.00

OVERALL PLANT MASS BALANCE

———————- KG-MOL/HR ——————— PERCENT

COMPONENT FEED +REACTION -PRODUCT =DEVIATION DEV ——————————- ————- ————— ————- ————— ———-

1 NITROGEN 848180.56 0.00 848180.25 0.00 0.00 2 ARGON 88366.38 0.00 88369.06 -2.68 0.00

3 OXYGEN 394707.31 0.00 394703.75 3.56 0.00

TOTAL 1.331E+06 0.00 1.331E+06 1.13 0.00

28





EXPANDER SUMMARY 02/01/93

==============================================================================

UNIT 14, ’EXP’

FEEDS 6

PRODUCTS VAPOR 7A

OPERATING CONDITIONS

INLET ISENTROPIC OUTLET —————- —————- —————-

TEMPERATURE, K 142.68 84.72 89.80 PRESSURE, ATM 9.09 1.40 1.40

ENTHALPY, M*KCAL/HR -2.0920 -2.4504 -2.3966 ENTROPY, KCAL/KG-MOL-K 35.0770 35.0760 35.7395

MOLE PERCENT VAPOR 100.0000 98.6354 100.0000 MOLE PERCENT LIQUID 0.0000 1.3646 0.0000 ACT VAP RATE, M3/SEC 0.3125

ADIABATIC EFF, PERCENT 85.00 WORK, KW

THEORETICAL 416.86 ACTUAL 354.33

29





COMPRESSOR SUMMARY 02/01/93

==============================================================================

UNIT 13, ’COM’

FEEDS 3

PRODUCTS VAPOR 4


INLET ISENTROPIC OUTLET ————- —————- —————-

TEMPERATURE, K 278.00 312.84 320.31 PRESSURE, ATM 6.00 9.03 9.03

ENTHALPY, M*KCAL/HR -1.1684 -0.9436 -0.8943 ENTROPY, KCAL/KG-MOL-K 40.7637 40.7637 40.9298

CP, KCAL/KG-MOL-K 6.9999 7.0338 CV, KCAL/KG-MOL-K 4.9412 4.9717 CP/(CP-R) 1.3961 1.3934

CP/CV 1.4166 1.4148 MOLE PERCENT VAPOR 100.0000 100.0000 100.0000

MOLE PERCENT LIQUID 0.0000 0.0000 0.0000 ACT VAP RATE, M3/SEC 0.9891

ADIABATIC EFF, PERCENT 82.0000 POLYTROPIC EFF, PERCENT 83.0418

ISENTROPIC COEFFICIENT, K 1.4053

POLYTROPIC COEFFICIENT, N 1.5320 HEAD, M

ADIABATIC 3529.75 POLYTROPIC 3574.60

ACTUAL 4304.57 WORK, KW

THEORETICAL 261.45 POLYTROPIC 264.77

ACTUAL 318.84

NOTE: POLYTROPIC AND ISENTROPIC COEFFICIENTS

CALCULATED FROM HEAD EQUATION

30





HEAT EXCHANGER SUMMARY 02/01/93

==============================================================================

UNIT 11, ’E3’, ’AR CONDENSER’


DUTY, M*KCAL/HR 2.958 LMTD, K 4.115

F FACTOR (FT) 1.000

MTD, K 4.115U*A, KCAL/HR-C 718916.313

HOT SIDE CONDITIONS INLET OUTLET ————— —————

FEED AV1MIXED PRODUCT AL1

VAPOR, KG-MOL/HR 1957.944 59.595 K*KG/HR 77.856 2.368 CP, KCAL/KG-K 0.132 0.132

LIQUID, KG-MOL/HR 1898.349 K*KG/HR 75.489

CP, KCAL/KG-K 0.276 TOTAL, KG-MOL/HR 1957.944 1957.944

K*KG/HR 77.856 77.856 CONDENSATION, KG-MOL/HR 1898.349

TEMPERATURE, K 88.951 88.920

PRESSURE, ATM 1.150 1.150

COLD SIDE CONDITIONS INLET OUTLET

————— ————— FEED 10

MIXED PRODUCT 11A VAPOR, KG-MOL/HR 469.560 2519.926

K*KG/HR 13.513 73.499

CP, KCAL/KG-K 0.255 0.250 LIQUID, KG-MOL/HR 4112.319 2061.953

K*KG/HR 122.754 62.768 CP, KCAL/KG-K 0.460 0.447

TOTAL, KG-MOL/HR 4581.878 4581.878 K*KG/HR 136.267 136.267

VAPORIZATION, KG-MOL/HR 2050.365 TEMPERATURE, K 84.036 85.520

PRESSURE, ATM 1.406 1.406

31





LNG HEAT EXCHANGER SUMMARY 02/01/93

==============================================================================

UNIT 15, ’LNG’

OPERATING CONDITIONS OVERALL

————DUTY, M*KCAL/HR 12.4445

HOT SIDE CONDITIONS

FEEDS 2 4 PRODUCTS VAPOR 6

MIXED 5A

TOTAL, KG-MOL/HR 8447.400 938.600KG/HR 244632.156 27181.350

INLET CONDITIONS TEMP, K 278.000 320.312

PRESS, ATM 6.000 9.034

L/F 0.0000 0.0000OUTLET CONDITIONS

QUANTITY SPECIFIED TEMP TEMP TEMP, K 100.788 142.697

PRESS, ATM 6.000 9.034L/F 0.0357 0.0000

CONDENSATION,KG-MOL/HR 301.159 0.000DUTY, M*KCAL/HR -11.2472 -1.1973

COLD SIDE CONDITIONS

FEEDS 19 22

PRODUCTS VAPOR 20 23

TOTAL, KG-MOL/HR 7351.928 1824.189

KG/HR 206198.250 58435.750INLET CONDITIONS

TEMP, K 96.297 94.819PRESS, ATM 1.170 1.574

L/F 0.0000 0.0000

OUTLET CONDITIONS

QUANTITY SPECIFIED N/A N/A TEMP, K 289.986 289.986

PRESS, ATM 1.170 1.574L/F 0.0000 0.0000

VAPORIZATION,KG-MOL/HR 0.000 0.000

DUTY, M*KCAL/HR 9.9445 2.5001

32





COLUMN SUMMARY 02/01/93

==============================================================================

UNIT 4, ’HP’, ’HP COLUMN’ (CONT)

————— NET FLOW RATES —————- HEATER

TRAY TEMP PRESSURE LIQUID VAPOR FEED PRODUCT DUTIES

DEG K ATM KG-MOL/HR M*KCAL/HR ———- ———- ———— ————- ———— ———— ———— —————-

40 100.2 5.94 4638.1 8526.4

41 100.3 5.95 4618.6 8503.7 42 100.5 5.95 4602.2 8484.1

43 100.6 5.95 4588.6 8467.7 44 100.7 5.96 8454.1 8447.4V 4581.9L

FEED AND PRODUCT STREAMS

TYPE STREAM PHASE FROM TO LIQUID FLOW RATES HEAT RATES TRAY TRAY FRAC KG-MOL/HR M*KCAL/HR —— —————— ———- ——- —- ———- ————— —————

FEED 5 VAPOR 44 0.0000 8447.40 -21.3781 PROD 12 LIQUID 1 3865.51 -14.9326

PROD 8 LIQUID 44 4581.88 -16.9096

PSEUDO PRODUCT STREAMS

TYPE STREAM PHASE FROM TO LIQUID FLOW RATES HEAT RATES TRAY TRAY FRAC KG-MOL/HR M*KCAL/HR

—— —————— ———- ——- —- ———- ————— ————— NET HPV VAPOR 2 9029.25 -24.4163

OVERALL MOLE BALANCE, (FEEDS - PRODUCTS) 8.1539E-03

OVERALL HEAT BALANCE, (H(IN) - H(OUT) ) 1.4107E-04

SPECIFICATIONS

PARAMETER TRAY COMP SPECIFICATION SPECIFIED CALCULATED TYPE NO NO TYPE VALUE VALUE

————————- —— ——- ——————— ————— ————— STRM 12 1 3 MOL PPM 1.000E+01 1.000E+01

REFLUX RATIOS

———— REFLUX RATIOS ————

MOLAR WEIGHT STD L VOL ———— ————— ————-

REFLUX / FEED STREAM 5 0.6113 0.5917 0.6319 REFLUX / LIQUID DISTILLATE 1.3358 1.3358 1.3358

34






==============================================================================

UNIT 7, ’LP’, ’LP COLUMN’

TOTAL NUMBER OF ITERATIONS

IN/OUT METHOD 20

COLUMN SUMMARY

————— NET FLOW RATES —————- HEATER TRAY TEMP PRESSURE LIQUID VAPOR FEED PRODUCT DUTIES


1 79.1 1.17 3466.7 3865.5M 7351.9V 2 79.2 1.18 3463.8 6953.1

3 79.3 1.18 3460.4 6950.2 4 79.3 1.19 3456.5 6946.8 5 79.4 1.19 3451.9 6942.9

6 79.5 1.20 3446.5 6938.3 7 79.6 1.21 3440.3 6932.9

8 79.7 1.21 3433.2 6926.7 9 79.9 1.22 3424.9 6919.6

10 80.0 1.22 3415.3 6911.3 11 80.2 1.23 3404.2 6901.7

12 80.3 1.24 3391.3 6890.6

13 80.5 1.24 3376.2 6877.7 14 80.7 1.25 3358.5 6862.6

15 80.9 1.25 3338.1 6845.0 16 81.2 1.26 3314.4 6824.5

17 81.5 1.27 3287.5 6800.8 18 81.8 1.27 3257.6 6773.9

19 82.2 1.28 3225.1 6744.0 20 82.6 1.28 3191.2 6711.6

21 83.0 1.29 3157.1 6677.6

22 83.4 1.29 3124.4 6643.5 23 83.7 1.30 3095.0 6610.9

24 84.1 1.31 3069.7 6581.4 25 84.4 1.31 3049.4 6556.2

26 84.6 1.32 3033.7 6535.8 27 84.8 1.32 3022.2 6520.1

28 85.0 1.33 5062.4 6508.6 4581.9M 29 85.2 1.34 5054.0 3966.9

30 85.4 1.34 5041.1 3958.5

31 85.6 1.35 5022.6 3945.7 32 86.0 1.35 4976.2 3927.1 938.6V

33 87.1 1.36 4916.0 2942.1 34 88.5 1.37 4854.2 2881.9

35 90.1 1.37 4810.8 2820.2 36 91.4 1.38 4789.1 2776.7

37 92.2 1.38 4780.6 2755.1 38 92.7 1.39 4777.8 2746.6

39 93.0 1.40 4777.2 2743.7

40 93.1 1.40 4777.3 2743.1

35






==============================================================================

UNIT 7, ’LP’, ’LP COLUMN’ (CONT)




41 93.2 1.41 4777.8 2743.3

42 93.3 1.41 4778.2 2743.7 43 93.4 1.42 4778.5 2744.1

44 93.5 1.43 4778.4 2744.4 1875.0V 45 93.5 1.43 6606.2 4619.3 1815.4L

46 93.6 1.44 6606.6 4631.8 47 93.6 1.44 6607.0 4632.2

48 93.7 1.45 6607.3 4632.5 49 93.7 1.46 6607.7 4632.9

50 93.8 1.46 6608.1 4633.3 51 93.9 1.47 6608.4 4633.6 52 93.9 1.47 6608.8 4634.0

53 94.0 1.48 6609.1 4634.3 54 94.0 1.48 6609.5 4634.7

55 94.1 1.49 6610.0 4635.1 56 94.1 1.50 6610.4 4635.5

57 94.2 1.50 6610.9 4636.0 58 94.3 1.51 6611.4 4636.4

59 94.3 1.51 6611.9 4636.9

60 94.4 1.52 6612.5 4637.5 61 94.4 1.53 6613.1 4638.0

62 94.5 1.53 6613.7 4638.7 63 94.5 1.54 6614.4 4639.3

64 94.6 1.54 6615.2 4640.0 65 94.6 1.55 6616.0 4640.7

66 94.7 1.56 6616.8 4641.5 67 94.7 1.56 6617.6 4642.3

68 94.8 1.57 6618.5 4643.2

69R 94.8 1.57 4644.1 1824.2V 10.4640 150.2L



—— —————- ———- ——- —- ——— ————— —————-

FEED 14 MIXED 1 0.8978 3865.51 -15.3966 FEED 11 MIXED 28 0.4467 4581.88 -14.4043

FEED 7 VAPOR 32 0.0000 938.60 -2.3967 FEED 16 LIQUID 45 1.0000 1815.38 -6.6104

PROD 18 VAPOR 1 7351.93 -20.3422 PROD 15 VAPOR 44 1875.00 -3.7499

PROD 22 VAPOR 69 1824.19 -3.7039 PROD 21 LIQUID 69 150.24 -0.5481

36






==============================================================================




—— —————- ———- ——- —- ——— ————— —————-

NET LPL LIQUID 68 6618.54 -24.1454

OVERALL MOLE BALANCE, (FEEDS - PRODUCTS) 1.0300E-02 OVERALL HEAT BALANCE, (H(IN) - H(OUT) ) 1.3540E-05

SPECIFICATIONS

PARAMETER TRAY COMP SPECIFICATION SPECIFIED CALCULATED TYPE NO NO TYPE VALUE VALUE ————————- —— ——— ——————— ————— —————

UNIT LP 69 DUTY -1.000E+00 -1.000E+00 STRM 18 1 3 MOL PPM 1.000E+01 1.000E+01

STRM 15 44 1- 3 MOL RATE 1.875E+03 1.875E+03

37






==============================================================================


COLUMN COMPOSITION PROFILE - VAPOR CUTS

1.0 +1111——-+————-+————-+————-+————-+————+———3333+

| 11111| | | | | 33333333 | | 111 | | | | 333333 | |

| | 11 | | | 333333 | |

0.9 +————-+—-11——+————-+————-+33333——+————-+————-+ | | 11 | | 33 | | |

| | 1| | 3 | | | | | | 11 | . | | | |

0.8 +————-+————-+-1———-+3————+————-+————-+————-+ | | | 11 | . | | | |

| | | 111 | . | | | | | | | 111 3 | | | |

V 0.7 +————-+————-+————-+1————+————-+————-+————-+ A | | | | 1 . | | | | P | | | | . . | | | |

O | | | | . . | | | | R 0.6 +————-+————-+————-+—1-3——+————-+————-+————-+

| | | | . . | | | | C | | | | . . | | | |

O | | | | . | | | | M 0.5 +————-+————-+————-+————-+————-+————-+————-+

P | | | | * | | | |

O | | | | . | | | | S | | | | .. | | | |

I 0.4 +————-+————-+————-+————-+————-+————-+————-+ T | | | | 3 . | | | |

I | | | | . . | | | | O | | | | . 1 | | | |

N 0.3 +————-+————-+————-+-3———-+————-+————-+————-+ | | | 33 . | | | |

| | | 33| . | | | |

| | | 33 | . | | | | 0.2 +————-+————-+——3——+——-1—-+————-+————-+————-+

| | | 3 | . | | | | | | | 3 | . | | | |

| | | 3 | . | | | | 0.1 +————-+———222+3————+——-2*22222222——+————-+————-+

| | 2222 3*22 | 2 . | 222222 | | | 222 3 | 222 | 2 1 | | 222222 | |

| 22222| 333 | 22222222 1| | 22222222 |

0.0 +****3333333333——-+————-+————-11111111111111111111111111****+ 0 10 20 30 40 50 60 70

TRAY NUMBER KEY... 1 - COMPONENT 1 2 - COMPONENT 2 3 - COMPONENT 3




==============================================================================

38



UNIT 8, ’ARG’, ’ARGON COLUMN’

TOTAL NUMBER OF ITERATIONS

IN/OUT METHOD 46

COLUMN SUMMARY


TRAY TEMP PRESSURE LIQUID VAPOR FEED PRODUCT DUTIES DEG K ATM KG-MOL/HR M*KCAL/HR

——— ———- ———— ———— ———— ————- ————- ——————

1C 88.9 1.15 1898.4 59.6V -2.9585 2 89.0 1.15 1898.0 1957.9

3 89.0 1.15 1898.1 1957.6 4 89.0 1.16 1898.2 1957.7

5 89.0 1.16 1898.4 1957.8 6 89.1 1.16 1898.5 1957.9

7 89.1 1.17 1898.6 1958.1 8 89.1 1.17 1898.7 1958.2

9 89.2 1.17 1898.8 1958.3 10 89.2 1.18 1898.8 1958.4 11 89.2 1.18 1898.9 1958.4

12 89.2 1.18 1899.0 1958.5 13 89.3 1.18 1899.0 1958.5

14 89.3 1.19 1899.0 1958.6 15 89.3 1.19 1899.0 1958.6

16 89.4 1.19 1899.0 1958.6 17 89.4 1.20 1898.9 1958.5

18 89.4 1.20 1898.8 1958.5

19 89.5 1.20 1898.7 1958.4 20 89.5 1.21 1898.5 1958.3

21 89.5 1.21 1898.3 1958.1 22 89.6 1.21 1898.1 1957.9

23 89.6 1.22 1897.8 1957.7 24 89.6 1.22 1897.4 1957.4

25 89.7 1.22 1896.9 1957.0 26 89.7 1.23 1896.4 1956.5

27 89.8 1.23 1895.7 1956.0

28 89.8 1.23 1894.9 1955.3 29 89.8 1.23 1893.9 1954.5

30 89.9 1.24 1892.7 1953.5 31 90.0 1.24 1891.3 1952.3

32 90.0 1.24 1889.5 1950.8 33 90.1 1.25 1887.4 1949.1

34 90.2 1.25 1884.8 1947.0 35 90.3 1.25 1881.6 1944.4

36 90.4 1.26 1877.9 1941.2

37 90.5 1.26 1873.4 1937.4 38 90.7 1.26 1868.2 1933.0

39 90.8 1.27 1862.3 1927.8 40 91.0 1.27 1856.0 1921.9

SIMULATION SCIENCES INC. R PAGE P-28PROJECT CASEBOOK PRO/II VERSION 3.30 19-JAN VAX VMS

PROBLEM AIR PLANT OUTPUT SIMSCI COLUMN SUMMARY 02/01/93

==============================================================================

39



UNIT 8, ’ARG’, ’ARGON COLUMN’ (CONT)



DEG K ATM KG-MOL/HR M*KCAL/HR ——— ———- ———— ———— ———— ————- ————- ——————

41 91.2 1.27 1849.5 1915.6

42 91.4 1.28 1843.3 1909.1 43 91.6 1.28 1837.7 1902.9 44 91.8 1.28 1833.0 1897.3

45 92.0 1.29 1829.1 1892.5 46 92.1 1.29 1826.2 1888.7

47 92.2 1.29 1824.1 1885.8

48 92.3 1.29 1822.5 1883.6 49 92.4 1.30 1821.5 1882.1

50 92.5 1.30 1820.8 1881.1 51 92.5 1.30 1820.4 1880.4

52 92.5 1.31 1820.2 1880.0 53 92.6 1.31 1820.1 1879.8

54 92.6 1.31 1820.1 1879.7 55 92.6 1.32 1879.7 1875.0V 1815.4L


TYPE STREAM PHASE FROM TO LIQUID FLOW RATES HEAT RATES

TRAY TRAY FRAC KG-MOL/HR M*KCAL/HR ——- —————— ——— —— —— ——— —————— ——————

FEED 15 VAPOR 55 0.0000 1875.00 -3.7499 PROD 17 VAPOR 1 59.59 -0.0977

PROD 16 LIQUID 55 1815.41 -6.6106



——- —————— ——— —— —— ——— —————— —————— NET AV1 VAPOR 2 1957.94 -3.2044

OVERALL MOLE BALANCE, (FEEDS - PRODUCTS) 4.9688E-03 OVERALL HEAT BALANCE, (H(IN) - H(OUT) ) -1.3665E-05

SPECIFICATIONS

PARAMETER TRAY COMP SPECIFICATION SPECIFIED CALCULATED TYPE NO NO TYPE VALUE VALUE

————————- —— ——— ——————- ————— —————

STRM 17 1 2 MOL RATIO 3.333E-01 3.333E-01

40





STREAM MOLAR COMPONENT FRACTIONS 02/01/93

==============================================================================

STREAM ID AL1 AV1 HPV HPV1

NAME PHASE MIXED VAPOR VAPOR LIQ-UID

FLUID MOLAR FRACTIONS

1 NITROGEN 1.8006E-03 1.8006E-03 0.9983 0.9983

2 ARGON 0.9778 0.9778 1.7327E-03 1.7327E-03 3 OXYGEN 0.0204 0.0204 1.0000E-05 1.0000E-05

TOTAL RATE, KG-MOL/HR 1957.9441 1957.9441 9029.2461 9029.2461

TEMPERATURE, K 88.9203 88.9514 96.2609 96.2463

PRESSURE, ATM 1.1500 1.1500 5.8000 5.8000ENTHALPY, M*KCAL/HR -6.1628 -3.2044 -24.4163 -34.8803

MOLECULAR WEIGHT 39.7644 39.7644 28.0337 28.0337MOLE FRAC VAPOR 0.0304 1.0000 1.0000 0.0000MOLE FRAC LIQUID 0.9696 0.0000 0.0000 1.0000

STREAM ID LPL LPL1 1 2 NAME AIR FEED

PHASE LIQUID MIXED VAPOR VAPOR

FLUID MOLAR FRACTIONS

1 NITROGEN 2.3767E-15 2.3767E-15 0.7811 0.7811 2 ARGON 4.3470E-03 4.3470E-03 9.3000E-03 9.3000E-03

3 OXYGEN 0.9957 0.9957 0.2096 0.2096


TEMPERATURE, K 94.7706 94.7791 278.0000 278.0000PRESSURE, ATM 1.5681 1.5681 6.0000 6.0000

ENTHALPY, M*KCAL/HR -24.1454 -13.6814 -11.6841 -10.5157

MOLECULAR WEIGHT 32.0336 32.0336 28.9595 28.9595MOLE FRAC VAPOR 0.0000 0.9774 1.0000 1.0000

MOLE FRAC LIQUID 1.0000 0.0226 0.0000 0.0000

41






==============================================================================

STREAM ID 3 4 5 5A

NAME PHASE VAPOR VAPOR VAPOR MIXED

FLUID MOLAR FRACTIONS 1 NITROGEN 0.7811 0.7811 0.7811 0.7811

2 ARGON 9.3000E-03 9.3000E-03 9.3000E-03 9.3000E-03

3 OXYGEN 0.2096 0.2096 0.2096 0.2096




MOLECULAR WEIGHT 28.9595 28.9595 28.9595 28.9595

MOLE FRAC VAPOR 1.0000 1.0000 1.0000 0.9643MOLE FRAC LIQUID 0.0000 0.0000 0.0000 0.0357

STREAM ID 6 7 7A 8

NAME HP BTMS

PHASE VAPOR VAPOR VAPOR LIQUID


2 ARGON 9.3000E-03 9.3000E-03 9.3000E-03 0.0157 3 OXYGEN 0.2096 0.2096 0.2096 0.3864



ENTHALPY, M*KCAL/HR -2.0916 -2.3967 -2.3966 -16.9096MOLECULAR WEIGHT 28.9595 28.9595 28.9595 29.7405


42






==============================================================================

STREAM ID 9 10 11 11A

NAME PHASE LIQUID MIXED MIXED MIXED


2 ARGON 0.0157 0.0157 0.0157 0.0157

3 OXYGEN 0.3864 0.3864 0.3864 0.3864






STREAM ID 12 13 14 15

NAME HP OVHD ARG FEED PHASE LIQUID LIQUID MIXED VAPOR

FLUID MOLAR FRACTIONS 1 NITROGEN 0.9983 0.9983 0.9983 2.4847E-04

2 ARGON 1.7327E-03 1.7327E-03 1.7327E-03 0.0930 3 OXYGEN 1.0000E-05 1.0000E-05 1.0000E-05 0.9067





43






==============================================================================

STREAM ID 16 17 18 19

NAME ARG BTMS AR PRODUCT PHASE LIQUID VAPOR VAPOR VAPOR

FLUID MOLAR FRACTIONS 1 NITROGEN 6.3523E-05 5.8832E-03 0.9972 0.9972

2 ARGON 0.0640 0.9754 2.8307E-03 2.8307E-03

3 OXYGEN 0.9359 0.0187 9.9998E-06 9.9998E-06


TEMPERATURE, K 92.6455 88.9204 79.1066 96.2968

PRESSURE, ATM 1.3169 1.1500 1.1700 1.1700ENTHALPY, M*KCAL/HR -6.6106 -0.0977 -20.3422 -19.4253



STREAM ID 20 21 22 23 NAME N2 PRODUCT O2 LIQUID O2 GAS

PHASE VAPOR LIQUID VAPOR VAPOR

FLUID MOLAR FRACTIONS 1 NITROGEN 0.9972 6.2509E-16 2.4174E-15 2.4174E-15

2 ARGON 2.8307E-03 2.8807E-03 4.3811E-03 4.3811E-03 3 OXYGEN 9.9998E-06 0.9971 0.9956 0.9956




MOLE FRAC VAPOR 1.0000 0.0000 1.0000 1.0000

MOLE FRAC LIQUID 0.0000 1.0000 0.0000 0.0000

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