reactor design within excel enabled by rigorous physical properties … · 2006-02-13 · reactor...
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Reactor Design within Excel Enabled by Rigorous Physical Properties and an Advanced
Numerical Computation Package
Mordechai ShachamDepartment of Chemical Engineering Ben Gurion University of the Negev
Beer-Sheva, Israel
Michael B. CutlipDepartment of Chemical Engineering
University of ConnecticutStorrs, CT, USA
Problem Solving in Chemical Engineering
MathematicalModel
Physical Properties
Solution Algorithm
Documentation
Chemical Engineer’s Tools of Trade - 1965
CalculationDocumentation
Properties
Graphical Solution
Chemical Engineer’s Problem Solution Techniques - 1965
Analytical solutions, including
Model simplification by neglecting less important terms
Model manipulation to bring it into a solvable form
Short-cut solution techniques
Replacing the problem with a simpler one that can be solved
Graphical solutions
Trial and error solution techniques
Numerical solution, including
Computer language programming and debugging
Shortcomings of the Traditional Solution TechniquesManual and Graphical Solution Techniques
Tedious, time consuming error prone process
Oversimplification may lead to wrong results
Highest precision is two decimal digits
Time constraints prevent screening of large number of alternatives to find an optimal solution
Computer Language Programming
Requires experts in programming, numerical and optimization methods
Tedious, time consuming error prone process
Modern Problem Solving Techniques
MathematicalModel
Physical Properties
Solution Algorithm
Documentation
Mathematical Software Package
User Supplied
Using this approach the USER supplies the mathematical model and the physical properties and the package provides the numerical solution. Appropriate for small scale problems and when model flexibility is essential.
Modern Problem Solving Techniques
Fogler H. S., “An Appetizing Structure of Chemical Reaction Engineering for Undergraduates”, Chem. Eng. Ed., 27(2), 110(1993)
Modern Problem Solving Techniques
MathematicalModel
Physical Properties
Solution Algorithm
Process Simulator
Documentation
Using this approach the USER provides only the process data.
Appropriate for large scale problems.
Chemical Engineering Student’s Tools of Trade - 2004
Material and Energy Balances (Prentice-Hall textbook by Himmelblau, 2003)
Thermodynamics (Prentice-Hall textbook by Kyle, 1999)
Chemical Reaction Engineering (Prentice-Hall textbook by Fogler, 2004, Wiley-VCH textbook by Hagen, 2004)
Process Dynamics and Control, Process Modeling and Numerical Methods
Product and Process Design and Simulation
The use of POLYMATH throughout the ChE curriculumChapters
Basic Principles and Calculations, Thermodynamics, Fluid Mechanics, Heat transfer, Mass Transfer, Chemical Reaction Engineering
Regression and Correlation of Data, Advanced Techniques in Problem Solving.
Coming next year in the 2nd edition
Additional chapters: Separation Processes, Biotechnology, Process Dynamics and Control
Conversion of POLYMATH models to Excel and MATLAB
Need for Spreadsheet-Based Calculations
287 Responses
http://www.cache.org/This nonprofit Educational Corporation is headquartered at the University of Texas at Austin.
Process Simulation Programs (Flowsheeting) in Organizations
• None 58.2% (163)• Aspen+ 20% (56)• Hysys 14.3% (40)• SIMSCI Pro II 7.5% (21)• ChemCAD 1.8% (5)• gPROMS 1.4% (4)• WINSIM 0.7% (2)• Other 6.1% (17)
Extending the Use of Numerical Problem Solving By Practicing Engineers
100% of the engineers in the industry use spreadsheets (mainly Excel) while only a very small percentage use programs as Polymath, MATLAB and Aspen.
Excel is inappropriate for complex numerical problem solving because of the need to convert variable names to cell addresses, difficulties in program documentation and unavailability of an ODE solver.
Polymath 6.0, due to be released this fall, enables definition of the problem using the Polymath notation and syntax and conversion of the Polymath input into a well documented Excel worksheet. A new ODE solver for Excel is also provided.
The New Paradigm in Problem Solving
MathematicalModel
Physical Properties
Solution Algorithm
Documentation
Excel
Aspen Properties
Polymath 6.0
POLYMATH 6.0 – Allows Easy Entry and Solution of Mathematical Problems using
Numerical Analysis CapabilitiesLinear Equations - up to 264 simultaneous equations.
Nonlinear Equations - up to 300 simultaneous nonlinear and 300 explicit algebraic equations
Differential Equations - up to 300 simultaneous ordinary differential and 300 explicit algebraic equations
Data analysis and Regression - up to 1200 data points with capabilities for linear, multiple linear, and nonlinear regressions with extensive statistics plus polynomial and spline fitting with interpolation and graphing capabilities
NEW Automatic Migration of All Problems to Excel
POLYMATH – A Long History in Engineering Computations
Aspen Properties Excel Calculator
Pure component constants (MW, Normal boiling point).
Vapor pressure at a specified temperature
Pure component property at specified temperature and pressure
Mixture properties for a specified mixture at given temperature and pressure
Two and three phase flash, bubble and dew point calculations (enables solving simultaneous differential and algebraic equations, DAE)
Non-isothermal Reactor Design Problem
1Fogler, H. S., Example 8-7, “Elements of Chemical Reaction Engineering,” 3rd Edition, Prentice-Hall, Upper Saddle River, NJ (1999)
Adiabatic operation will be modeled.
Reactor Design Problem – Model Equations
Let A = acetone, B = ketene and C = methane, thus
A → B + C
AC
AB
AA r
dVdFr
dVdFr
dVdF
−=−== and;Mole Balances
AA kCr −=Rate Law
CBA
AA
AA FFF
FyRT
PyC++
== ;Stoichiometry
Energy Balance (Adiabatic Operation)
pCCpBBpAA
AR
CFCFCFrH
dVdT
++−∆−
=))((
Reactor Design - Polymath Model Entry
Note – notation and syntax as in problem definition
No need to reorder equations
Model serves as documentation
Physical properties are needed
Physical Properties – The Traditional Approach
Physical Properties – The Traditional Approach (2)
Data and part of the calculations
Creation of a Physical Property Data File in Aspen Properties
Physical Properties – The New Approach
Specification of Components in Aspen Properties
Physical Properties – The New Approach
Specification of Property Method inAspen Properties
Physical Properties – The New Approach
Saving Data File within Aspen Properties for Use in Excel
Provision of Physical Property Data in Excel by Aspen Properties Add-In
Feed temperature and mole fractions
CPA CPB CPC
Copy to Polymath
Connection of Property Data to Polymath Program within Excel
The variables T, P, yA (mole fraction of A) , yB, and yC must be sent to the corresponding variable locations with the Aspen Properties area of the Excel worksheet.
Additionally, the variables deltaH (heat of reaction calculated from the enthalpies), CpA(heat capacity of A), CpB, and CpC must be made available in the Polymath coding for the solution of the differential equations.
Polymath Model With Aspen Properties Data
Export of Polymath Program to Excel(A single key press automatically migrates the problem.)
Excel Formulas
Documentation
Documentation
Excel Formulas for the Reactor Problem
Initial model set-up with Excel is a tedious and error prone process because of the need to convert variable names to cell addresses.
This is practically impossible for a complex problem.
Connecting Data Information between Polymath and Aspen Properties
Constant values are replaced by cell addresses from Aspen Properties
The Polymath ODE_Solver can then be used to solve the system of differential and explicit algebraic equations.
Note that as the temperature changes in the reactor, this new temperature is used in Aspen Properties to update the heat of reaction and the heat capacities within the equations used to solve the differential and algebraic equations. During the integration of the differential equations, the property values change with the temperature as the independent variable goes from 0 to 4.
The Polymath ODE_Solver automatically presents the results in a new sheet in the Excel workbook.
Columns of intermediate data can be
identified for plotting in Excel.
These data columns can then be plotted with Excel.Fogler Example Problem 8-7
0
5
10
15
20
25
30
35
40
0 0.5 1 1.5 2 2.5 3 3.5 4
Reactor Volume, m3
Mol
ar F
low
Rat
es, m
ol/s
FAFBFC
FB and FC coincide in this graph.
Figure E8-7.1 from the Fogler textbook can also be generated from the intermediate data by using Excel.
Fogler Example 8-7
890
910
930
950
970
990
1010
1030
1050
0 0.5 1 1.5 2 2.5 3 3.5 4
Volume, m3
Tem
pera
ture
, K
0
0.05
0.1
0.15
0.2
0.25
0.3
Con
vers
ion
Excel Plot
Fogler Text Plot
Additional Typical Examples that Have Been Solved Utilizing the New Approach
1. Reactor Design• Conversion of Nitrobenzene to Aniline in a Tubular Reactor• Oxidation of O-Xylene to Phthalic Anhydride in a Tubular
Reactor• Batch Decomposition of Acetylated Castor Oil• Semi-Batch Manufacture of Hexamethylenetriamine
2. Batch Distillation• Separation of Methanol from Water in a Four Stage Column• Multicomponent, Semi-Batch Steam Distillation
3. Steady State Absorption Column Design
4. Rigorous Heat Exchanger Design
SUMMARYThis paper highlights the highlights the concepts necessary for advanced problem solving with Excel as enabled by Polymath and Aspen Properties. These are:• Entry of basic problem in Polymath 6 with constant
physical properties followed by export to Excel.• Creation of a physical property data base within
Aspen Properties followed by export to Excel via Aspen Properties Excel Add-In.
• Formulation of the problem within Excel that links the physical properties from Aspen Properties to the equations from Polymath.
• Use of the Polymath ODE_Solver Add-In to solve the problem within Excel.
• Generation of tabular and graphical outputs within Excel.
CONCLUSIONS
Polymath and Aspen Properties now allow the solution of real-life, process design and related problems in a short time and with high precision, using Excel.
Chemical engineering professionals can start using the combined Polymath -> Excel <-Aspen Properties capability immediately in solving real problems on the personal computer desktop.
CONCLUSIONS (Cont.)
Chemical engineering students can begin using the combined Polymath -> Excel <-Aspen Properties capability for problem solving in their first engineering course of “Material and Energy Balances. Students can continue to use the same approach throughout their CHEG curriculum and will carry this capability into their industrial practice.
Software References
• Aspen Properties is a product of AspenTechhttp://www.aspentech.com/
• Excel is a product of Microsoft Corporationhttp://www.microsoft.com/
• Polymath is a product of Polymath Softwarehttp:// www.polymath-software.com/