course contents - bangladesh university of engineering and...

March 28, 2008ChE 201/[email protected]

Course Contents

Basic process calculations and process system variables (Chapter 4)Material balances on non-reactive and reactive processes – single unit and multiple unit (Chapter 4)Multiphase systems (Chapter 6)Material and energy balances on non-reactive processes (chapter 8)Material and energy balances on reactive processes (chapter 9)Computer Aided Calculation - Degrees of freedom analysis for a whole system (chapter 10)Material balances for transient or unsteady state systems (chapter 11)


Only true for steady-state process


Lesson learnt from ChE 111

Introduction to chemical engineering + Chapter 1Chapter 2

Introduction to engineering calculationsChapter 3

Process and process variablesChapter 4

General balance equation, steady state processFlowchart scaling, problem book keeping, etc.Multiple unit processesReactive systemsCombustion reactions

Chapter 5Single phase systemsReal gases

Chapter 7Energy and energy balances

Chapter 8Balances on non-reactive processes


Course Teacher and Textbooks

Felder, Richard M. and Rousseau Ronald W., Elementary Principles of Chemical Processes, 3rd Ed., John Wiley & Sons, INC, New York.

Dr. M. A. A. Shoukat Choudhury

Email: [email protected]

Website: http://teacher.buet.ac.bd/shoukat/

Textbook:

Himmelblau David M., Basic Principles and Calculations in Chemical Engineering, 6th Ed., Prentice Hall of India Private Limited, New Delhi, 1997Reklaitis, G. V., Material and Energy Balances, John Wiley & Sons, New York.

Reference Books:

mailto:[email protected]


Syllabus

Lecture No

Topic Chapter/Section

1 INTRODUCTION2-7 REVIEW OF MATERIAL BALANCES2 Procedure for material balance calculations

Balances on multiple-unit processes4.3e4.4

3 Balances on reactive processes 4.3

4 - 6 Recycle and bypass-Reactive processesPurging

4.54.6d4.74.7g

7 Combustion Reactions 4.8


Syllabus (contd.)

Lecture No


8 - 14 MULTIPHASE SYSTEMS8 Separation of components from a single

phase using different unit operations

9-10 Single component phase equilibriumGibbs Phase Rule

6.16.2

11-12 Gas-liquid systems with one condensable component

6.3

13-14 Multi-component gas-liquid systems 6.4


Syllabus (contd.)

Lecture No


15-23 ENERGY BALANCES ON NON-REACTIVE PROCESSES

15 State properties and process pathsChanges in pressure at const. temperatureChanges in T, sensible heat & heat capacities

8.1-8.3

16-17 Phase change operations 8.4a-8.4c

18-20 Psychrometric charts 8.4d-8.4e

21 Mixing & solution 8.5a-8.5b

22 Enthalpy-Concentration diagrams 8.5c

23 Flash vaporization 8.5d


Syllabus (contd.)

Lecture No


24-30 BALANCES ON REACTIVE PROCESSES24-26 Energy balances on reactive processes 9.1-9.5a

27-28 Adiabatic reactors 9.5b

29-30 Fuels and combustion 9.6

31-33 COMPUTER-AIDED BALANCE CALCULATIONS

Chapter 10

34-35 BALANCES ON TRANSIENT PROCESS Chapter 11

CLASS TESTREVIEW


What to do in the class room!!!!!!!

o Knowledge Sharingo Interactive Classo Ask questions without taking any permissiono Welcome to leave the class if you think you are not

learning anything.o Teacher would like to modify teaching methodology

in accordance to your demand

Zero Tolerance for gossiping in the Class. Zero Tolerance for gossiping in the Class.

Always come and meet if you have any questionAlways come and meet if you have any question--You are welcome!!You are welcome!!

Material Balance-Part 1

Chapter 4Fundamentals of Material Balances


Process Classification

3 type of chemical processes:1. Batch process

Feed is charge to the process and product is removed when the process is completedNo mass is fed or removed from the process during the operationUsed for small scale productionOperate in unsteady state


Process Classification

2. Continuous processInput and output is continuously fed and remove from the processOperate in steady stateUsed for large scale production

3. Semibatch processNeither batch nor continuousDuring the process a part of reactant can be fed or a part of product can be removed.


2 type of process operations:1. Steady state

All the variables (i.e. temperatures, pressure, volume, flow rate, etc) do not change with time

2. Unsteady state or transientProcess variable change with time


Define type and operation of processes given:A balloon is filled with air at steady rate of 2 g/minSemibatch and unsteady stateA bottle of milk is taken from the refrigerator and left on the kitchenBatch and unsteady stateWater is boiled in open flaskSemibatch and unsteady state

Try This…


Balances on Continuous Steady-State Process

Steady state; accumulation = 0

INPUT + GENERATION = OUTPUT + CONSUMPTION

If balance on steady-state non-reactive processes; generation = 0, consumption = 0

INPUT = OUTPUT

General Balance Equation:

INPUT + GENERATION – OUTPUT – CONSUMPTION = ACCUMULATION


1. Learn how to organize information about process variables

- Flow Chart drawing and Labeling2. Choose a Basis3. Set up material balance equations4. solve the equations for unknown variables.

Steps for Material Balance Calculations:


Flowcharts

When you are given process information and asked to determine something about the process, it is essential to organize the information in a way that is convenient for subsequent calculations.The best way to do this is to draw a flowchart

using boxes or other symbols to represent process units (reactors, mixers, separation units, etc.)lines with arrows to represent inputs and outputs.


The flowchart of a process can help get material balance calculations started and keep them moving.Flowchart must be fully labeled when it is first drawn, with values of known process variables and symbols for unknown variables being written for each input and output stream. Flowchart will functions as a scoreboard for the problem solution: as each unknown variable is determined its value is filled in, so that the flowchart provides a continuous record of where the solution stands and what must still be done.

Flowcharts……


Step 1.2: Labeling a flowchart

2 suggestions for labeling flowchart:1. Write the values and units of all known

stream variables at the locations of the streams on the flowchart. For example, a stream containing 21 mole% O2 and 79% N2 at 320˚C and 1.4 atm flowing at a rate of 400 mol/h might be labeled as:

400 mol/h

0.21 mol O2 /mol0.79 mol N2 /molT = 320˚C, P = 1.4 atm


Process stream can be given in two ways:a) As the total amount or flow rate of the stream

and the fractions of each componentb) Or directly as the amount or flow rate of each

component.

60 kmol N2 /min40 kmol O2 /min

0.6 kmol N2 /kmol 0.4 kmol O2 /kmol

100 kmol/min

3.0 lbm CH44.0 lbm C2 H43.0 lbm C2 H6

0.3 lbm CH4 /lbm0.4 lbm C2 H4 /lbm0.3 lbm C2 H6 /lbm

10 lbm

Labeling a flowchart-continue


2. Assign algebraic symbols to unknown stream variables [such as m (kg solution/min), x (lbm N2 /lbm), and n (kmol C3 H8 )] and write these variable names and their unitson the flowchart.

mol/h

0.21 mol O2 /mol0.79 mol N2 /molT = 320˚C, P = 1.4 atm

n& 400 mol/h

y mol O2 /mol(1-y) mol N2 /molT = 320˚C, P = 1.4 atm

Labeling a flowchart(continued)


If that the mass of stream 1 is half that of stream 2, label the masses of these streams as m and 2m rather than m1 and m2.If you know that mass fraction of nitrogen is 3 times than oxygen, label mass fractions as y g O2 /g and 3y g N2 /g rather than y1 and y2 . When labeling component mass fraction or mole fraction, the last one must be 1 minus the sum of the others.If volumetric flow rate of a stream is given, it is generally useful to label the mass or molar flow rate of this stream or to calculate it directly, since balance are not written on volumetric qualities.

Labeling a flowchart-continue


Consistent on Notation

gas in fraction moles yliquid in moles)or (mass fraction component x

rate flow volume V

volumeVrate flowmolar n

moles nrate flow mass m

mass m

===

=====

&

&

&


Try This..

Two methanol-water mixture are contained in separate flask. The first mixture contains 40wt% methanol and the second flask contains 70wt% methanol. If 20 Kg of the first mixture are going to be mixed with 15000 g of the second in a mixing unit, what are the mass and composition of the product of the mixing unit?


An experiment on the growth rate of certain organism requires an environment of humid air enriched in oxygen. Three input streams are fed into an evaporation chamber to produce an output stream with the desired composition.A: Liquid water fed at rate of 20 cm3/minB: Air (21% O2 and 79% N2 )C: Pure O2 with a molar flow rate one-fifth of the molar flow rate of stream BThe output gas is analyzed and is found to contain 1.5 mole% water. Draw and label the flowchart of the process, and calculate all unknown stream variables.

Try This..


Flowchart Scaling & Basis of Calculation

Flowchart scaling – procedure of changing the values of all stream amounts or flow rates by a proportional amount while leaving the stream compositions unchanged. The process would still be balance.

Scaling-up – if final stream quantities are larger than the original quantities.

Scaling down – if final stream quantities are smaller than the original quantities.


Questions

course contents - bangladesh university of engineering and...

Documents