Since 1991 he has been co-leader of the National Effective Teaching Institute under the auspices of the American Society for Engineering Education. He is a graduate of Louisiana State University and an elected member of the LSU Engineering Hall of Distinction.
2005 Edition
FEATURES
Industrial Process Case Studies
Preface to the Third Edition
Interactive Chemical Process Principles CD
Computational Software (E-Z Solve)
Website
ACKNOWLEDGMENTS
Teaching and promoting a systematic approach to process analysis
Homework problems and assignment schedules
Student Workbook
Notes to Instructors
Using the case studies
Resources for instructors
Instructional Tutorials
Interactive Chemical Process Principles
CD near front of text)
Physical Property Database
Visual Encyclopedia of Chemical Engineering Equipment
Z Solve
It would be a long and tedious task if done with a simple calculator and not too difficult for a spreadsheet. Once the equations are entered, a command for "Select" will be entered followed by a click on "OK" and the solution for all three variables will appear at once.
Nomenclature
The highest pressure at A process in which a gas or liquid that distinguishes vapor and liquid phases can mix, contact with a solid (the ) and a coexistence for a species. When applied to the heating of a centrifuge. mixture of liquids exposed to a gas at the given A device in which two liquid phases or pressure, the temperature at which the mixture liquid and solid phases separate by gravity.
Glossary of Chemical Process Terms
Heated the column gradually becomes richer is transferred from the stream at the higher in the more volatile components of the feed, temperature through the barrier to the other and the liquid that flows down becomes richer in the stream. The vapor product is rich in the more specific component; for ideal gases, the same volatile components of the feed and the rest as mole percent.
Contents
Preface to the Third Edition ix Notes to Instructors xii
Interactive Chemical Process Principles xiv Nomenclature xvii
Glossary xxi
Chapter What Some Chemical Engineers Do for a Living 3 Chapter Introduction to Engineering Calculations 7
Chapter Processes and Process Variables 42
PART ENGINEERING PROBLEM ANALYSIS 1
Chapter Fundamentals of Material Balances 83
Chapter Single-Phase Systems 187
Chapter Multiphase Systems 237
Chapter Energy and Energy Balances 313
PART MATERIAL BALANCES 81
PART ENERGY BALANCES 311
Chapter Balances on Nonreactive Processes 357
Chapter Balances on Reactive Processes 440
Chapter Computer-Aided Balance Calculations 504
Chapter Balances on Transient Processes 543
Chapter Production of Chlorinated Polyvinyl Chloride 579
Chapter Steam Reforming of Natural Gas
Chapter Scrubbing of Sulfur Dioxide from Power Plant Stack Gases 602
Appendix Computational Techniques 607
Appendix Physical Property Tables 627
Answers to Test Yourselves 655 Answers to Selected Problems 665
PART CASE STUDIES 577
Part One
Engineering Problem
Chapter
What Some Chemical
Engineers Do for a Living
INSTRUCTIONAL OBJECTIVES
Introduction to
Engineering Calculations
UNITS AND DIMENSIONS
Given tabular data for two variables ( and ), use linear interpolation between the two data points to estimate the value of one variable for a given value of the other. Given a two-parameter expression that relates two variables [such as sin(2) or 1 () and two adjustable parameters (in), state what you would draw versus creating a straight line.
CONVERSION OF UNITS
To convert a quantity expressed in terms of one unit to its equivalent in terms of another unit, multiply the i and quantity by the conversion factor.
TEST
YOURSELF (Answers, p. 655)
SYSTEMS OF UNITS
Two of the basic SI units—the ampere for electric current and the candela for light intensity—will not concern us in this book. The factors needed to convert from one force unit to another are summarized in the table on the inside front cover.
NUMERICAL CALCULATION AND ESTIMATION a Scientific Notation, Significant Figures, and Precision
The number of significant digits in the reported value of a measured or calculated quantity gives an indication of the precision with which the quantity is known: the more significant digits, the more accurate the value. The addition and subtraction rule concerns the position of the last significant digit in the sum, that is, the location of this digit relative to the decimal point.
The true value could also be defined as the value that would be calculated by taking an infinite number of measurements and averaging the results, but there is no practical way to do that either. However, even with a large number of measurements, the sample mean is at best an approximation of the true value and may in fact be quite far off (eg if there is something wrong with the instruments or procedures used for the measurement).
Of the 37 measured values of , 27 fall within one standard deviation of the mean, 33 within two standard deviations, and 36 within three standard deviations. There is a high probability (over 90%) that a measured value of will fall within two standard deviations of the mean.
DIMENSIONAL HOMOGENEITY AND DIMENSIONLESS QUANTITIES
Each equation must be dimensionally homogeneous: that is, all addition terms on both sides of the equation must have the same dimensions. For the equation to be valid, it must be dimensionally homogeneous, so that each term must have the dimension of length.
PROCESS DATA REPRESENTATION AND ANALYSIS
Exponents like the in transcendental functions like and ar uments of transcendental functions like the X in must be dimensionless quantities.
If the formula is correct, a plot of versus should be linear, with slope and intercept. How would you plot ( , ) data to get a straight line, and how would you determine and for each of the following functions.
When you plot numbers of an arithmetic y on a logarithmic scale, you are actually plotting the . Don't plot on a logarithmic scale and expect something useful to come out.
SUMMARY
If is a measured process variable, the of a set of measured values, , is the mean of the set (the sum of the values divided by the number of values). Calculate the weight of the pond contents in lb, using a one-dimensional equation for your calculation.
Prandtl number,
It is defined as , where is the heat capacity of the liquid, is the viscosity of the liquid, and is the thermal conductivity. When the value of the Reynolds number is less than about 2100, there is a flow - that is, the fluid flows in smooth streams.
Reynolds number
Since this coefficient is difficult to determine directly, the values of the other variables are measured or estimated and calculated from the given correlation. Use two-point linear interpolation or extrapolation to estimate ( 0 6 min) and ( 0 10 mol/L) from the measured values, and compare these results with the actual values of these quantities.
The following data are taken for the concentration of A, (g/L), as a function of time, (min), from the start of the reaction: Using the results in part (b), estimate the initial concentration of the waste in the tank and the time required to reach the discharge level.
Processes and
Process Variables
- INSTRUCTIONAL OBJECTIVES
- MASS AND VOLUME
- FLOW RATE
- a Mass and Volumetric Flow Rate
- b Flow Rate Measurement
If the mass flow rate of the fluid is (kg/s), then every second kilogram of fluid passes through the cross section. How do inlet and outlet gas mass flow rates compare?
CREATIVITY EXERCISE
CHEMICAL COMPOSITION
A (g-mol or in SI units) of a species is the amount of that species whose mass in grams is numerically equal to its molecular weight. Other types of moles (eg kg-mole or kmol, lb-mole, ton-mole) are similarly defined. kg/kmol, g/mol, lb /lb-mol Molecular mass can also be used as a conversion factor that relates mass to the number of moles of a substance.
YOURSELF (Answers, p. 656)
- b Mass and Mole Fractions and Average Molecular Weight
- c Concentration
- d Parts per Million and Parts per Billion
- PRESSURE
- a Fluid Pressure and Hydrostatic Head
- b Atmospheric Pressure, Absolute Pressure, and Gauge Pressure
- c Fluid Pressure Measurement
- TEMPERATURE
Is the pressure at the plug dependent on the height of the opening in the tank. The open end of the tube is exposed to the liquid whose pressure is to be measured.
CREATIVITY EXERCISES
SUMMARY
What is the flow rate of the gas stream leaving the condenser in mol/min. How high above the bottom of the manometer would the mercury be in the arm connected to the tube.
When the gas is not flowing, the pressure is the same everywhere in the pipe. For each of the given readings, calculate the pressure drop across the orifice, (mm Hg).
Suppose you set the thermostat to the value calculated in part (b) and the reading from a thermocouple mounted in the bath equilibrates at 295 F instead of 320 F. Calculate the total mass flow rate and the mass fraction of the methane at point 3.
Part Two
Material Balances
INSTRUCTIONAL OBJECTIVES
Fundamentals of Material Balances
PROCESS CLASSIFICATION
The feed is filled (fed) into a container at the beginning of the process, and the contents of the container are removed somewhat later. The temperature of the reactor is constant, and the composition and flow rate of the incoming reactant stream is also independent of time.
BALANCES
MATERIAL BALANCE CALCULATIONS
One thousand kilo rams per hour of pure propane is preheated to a temperature of 670 C before it goes into the reactor. The reactor effluent ash, which includes propane, propylene, methane and hydro-ene, is cooled from 800 C to 110 C and fed to an absorption tower, where the propane and propylene are dissolved in oil.
For example, if you did not know the flow rate of the stream described in the first illustration of step 1, you could label the stream. Once the variable name ( ) for the air flow rate is chosen, the given information about the ratio of the air and flow rate can be used to name the flow rate 0.200.
Suppose you have balanced a process and the amount or flow rate of one of the process streams is . Calculate the ratios (liter H2O/kg feed solution) and (kg product solution/kg feed solution). an amount or flow rate of one of the feed or product streams.
The flow rate of the condensate (the liquid leaving the condenser) is measured and found to be 225 L/h. Select a quantity or flow rate for one of the process streams as the calculation basis.
Its value will be determined from the known volumetric flow rate and density of the feed stream. 1 density ratio (relates the mass flow rate to the given volumetric flow rate of the feed).
BALANCES ON MULTIPLE-UNIT PROCESSES
ⲆBenzene balance
CHEMICAL REACTION STOICHIOMETRY
Fractional Conversion, and Extent of Reaction
If the reactants are fed to a chemical reactor in stoichiometric proportion and the reaction proceeds to completion, all the reactants are consumed. Then ( ) ( ) is the amount by which A in the food exceeds the amount needed to react completely if the reaction goes to completion.
YOURSELF (Answers, p. 657)
Some reactions are essentially; that is, the reaction proceeds in only one direction (from reactants to products) and the concentration of the limiting reactant eventually approaches zero (although "eventually" could mean seconds for some reactions and years for others). The equilibrium composition for such a reaction is therefore the composition corresponding to the complete consumption of the limiting reactant.
Calculate the molar composition of the product gas and the selectivity of ethylene to methane production. If values of any two outlet amounts are given, the values of and can be determined from the corresponding two equations, and the remaining amounts can again be calculated from the remaining three equations.
BALANCES ON REACTIVE PROCESSES a Balances on Molecular and Atomic Species
Similarly, if two atomic species occur in the same ratio in which they appear in a process, balances on these species will not be independent equations. Since nitrogen and oxygen are shown as being in the same ratio wherever they appear on the flow diagram (3.76 mol N/mol O ), you cannot count them as two independent species, and therefore you can only count two independent molecular species balances in a degree-of-freedom analysis—. one for either O or N and one for CCl.
Then calculate the molar composition of the product stream using molecular species balances, atomic species balances and degree of reaction. For example, the formation of water in reaction 1 can be expressed in terms of the oxygen consumption in that reaction as.
Calculate the composition of the product, the ratio (moles recycled)/(moles fresh feed) and the single-pass conversion. The lower single-pass conversion therefore results in a decrease in the reactor's costs.
To avoid build-up of the inert in the system, a purge stream is withdrawn from the recycle. In this analysis, we assumed that we knew , , , and from the reactor analysis, and since we used the methanol and water balances when labeling the bottom product stream, we counted only three available balances in the degrees of freedom analysis.
COMBUSTION REACTIONS
You must therefore be able to convert a dry basis composition to its equivalent wet basis composition before writing material balances on the combustion reactor. 0 930 lb-mol dry gas/lb-mol wet gas lb-mol dry gas Therefore, the assumed basis contains the gas.
The theoretical air required to burn an amount of fuel does not depend on the amount actually burned.
Since the fuel's molecular composition is unknown, we feel its atomic species composition. We must first determine the theoretical oxygen required to consume the carbon and hydrogen in the fuel.
SOME ADDITIONAL CONSIDERATIONS ABOUT CHEMICAL PROCESSES
The feed stream flow rate is set at 500 litres/s and sufficient time is allowed to elapse for the rotameter readings of the product stream to reach stable levels. State possible reasons for the differences between the design predictions and the experimental values of the output stream variables and for the failure to close the experimental system balance.
SUMMARY
If two or more flow rates or quantities are specified in the problem statement, they form the basis of the calculation. The volume of the tank contents is (m ) and the volumetric flow rate of the inlet and outlet streams is (m/s).
Ⲇ PROBLEMS
Based on 100 mol/h of gas fed to the absorber, draw and label the process flow diagram. Calculate the fractional removal of CO in the absorber (absorbed mol/mol in the gas feed) and the molar flow rate and composition of the liquid feed to the stripping tower.
The entrained liquid mass is 15% of the liquid mass supplied to the second mixer. As before, the mass of the entrained liquid in the solid cake is 15% of the mass of liquid fed to the mixer.
