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Tier

Tier. 2. Use of computer as a simulation tool. Statement of intent. Use of computer as simulation tool. It contain a series of closed problems with their solution. It is explained the assumption made, and the methods apply to solve them.

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Tier

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  1. Tier 2 Use of computer as a simulation tool

  2. Statement of intent Use of computer as simulation tool It contain a series of closed problems with their solution. It is explained the assumption made, and the methods apply to solve them. • To review the process to create a simulation flowsheet. • To give the student some tips to simulate. • To run some simulations in a computer.

  3. Contents Table of content • Solving closed problem. • Resolution of problems with a spreadsheet (excel). • Using advance mathematic software (matlab). • Separation NH4 – H20 using specialize software (aspen tech). • Using tools as sensitivity analysis and optimization.

  4. SolvingClosed problem

  5. Closed problems Closed Problems Closed problems are the type with only one right answer. These are the same types of problems that are usually found at the end of chapters in text books, and they reinforce concepts learned in the corresponding chapters.

  6. Closed problems Algorithm • Write out the problem statement. • Draw and label a sketch. • List assumptions and approximations involved in solving the problem.

  7. Closed problems Algorithm • Check to see if the problem is either under – specified or over – specified. • Relate problem to a similar problem or experience. • Develop, derive, integrate or manipulate an equation from which the desired variable can be determined.

  8. Closed problems Algorithm • Substitute numerical values and calculate the desired variable. • Examine and evaluate the answer to see it makes sense.

  9. Closed problems Some advice when running a simulation • Are you designing trays? Pressure drop is important and surface tension plays a key role in pressure drop calculation. • Do you have azeotropes? Do you suspect they may exist? Check them out before proposing a modification that will violate the second law of thermodynamics. • Trace components should not be brushed aside.

  10. Closed problems Some advice when running a simulation • Check your pure component and mixture densities. • Check your pure-component and mixture enthalpies and heat capacities if you are going to do any calculations related to energy balance. • Are you going to design heat exchangers? It is good idea to check your transport properties.

  11. Closed problems Some Advice when running a simulation • Talk with people.(chemist, vendor, other engineers doing the same). • Beware of using estimated parameters and interaction parameters when screening process alternatives. • Go see the plant. Plant personnel are usually helpful. Their insight and your knowledge of modeling can form a strong bond for problem solving.

  12. Closed problems Some Advice when running a simulation Simulation is a means, not an end, no matter how much effort you put into the model. Once, after finishing a large simulation model with several hundreds of unit operations, one of us had to spend many hours fixing the model, because air leakage into equipment was not taken into account.

  13. Closed problems Commercial Simulation Software Packages There are many of them, some of them are: • Excel (spreadsheet) • Matlab (matrix laboratory) • Fortran (programming language) • Aspen tech • WinGEMS • CADSIM plus PAPDYN • G2 (Gensym) • IDEAS (Simons)

  14. Problem resolutionwith spreadsheets

  15. Using spreadsheets Excel spreadsheet Used to calculate small mass or energy balances from the conservation equations Pinch Analysis Add new streams Add new streams

  16. Solving problems withAdvance mathematics software

  17. Advance mathematic software Matlab Is a mathematic specialized software, which allows one to make use of complicate equations, with rigorous iterative convergence methods in an easier way.

  18. Advance mathematic software Reaction profile of the pulp digester

  19. Advance mathematic software Mathematical Model • The main equations in the model: 0 0 0

  20. Advance mathematic software Source Code is a series of instructions with a specific sequence, to solve the mathematical equation.

  21. Advance mathematic software Behavior Expected Solving the model with the corresponding assumptions, and the mathematics calculation, the graphic output of the simulation is shown.

  22. Using specialized softwareto simulate a process

  23. Using specialized software What do more advanced simulation package offer? The use of specialized software, allows one to solve complicated problems, using relationships such as mass and energy balances, phase and chemical equilibrium, and reaction kinetics, with thermodynamic data, and rigorous equipment models.

  24. Using specialized software Advantage of specialized software • Interactive interface. • Different forms to enter data. • Verification of incoming data against ranges. • Check degrees of freedom. • Sensitivity analysis. • Optimization capabilities. • Easy way to display results.

  25. Solution of some problems using specialized software • NH4 – H2O separation. • Sensitivity analysis of C2H5Cl manufacture. • Optimization of C2H5Cl manufacture.

  26. NH4 – H2O separation Problem statement Determine what will be the liquid composition and the vapor composition after the separation.

  27. NH4 – H2O separation Drawing the diagram • Crating a process flowsheet.

  28. NH4 – H2O separation Giving name, and selecting units to use

  29. NH4 – H2O separation Components and Method • Insert the components to use. • Chose the base method to solve the equations.

  30. NH4 – H2O separation RK-Soave Use this method for non-polar, mildly polar mixtures. This property method is particularly suitable in the high temperature and high pressure regions. It is recommended for gas – processing, refinery, and petrochemical applications.

  31. NH4 – H2O separation Specify feed stream • Specify the assumption made, and the characteristics in the feed.

  32. NH4 – H2O separation Specifying the process • Give the specification to the condenser. • Specify the valve assumptions.

  33. NH4 – H2O separation Specifying the process • Specify the separator conditions. • Run the simulation.

  34. NH4 – H2O separation Checking results • The flow in “vap” stream is mainly ammonia, so we can appreciate the separation.

  35. NH4 – H2O separation What can be done with simulation • Steady state simulation is useful to predict the behave of a process in the plant. • What if, situations can be check with simulation. • Sensitivity analysis and optimization problems.

  36. Sensitivity analysis ofC2H5Cl manufacture

  37. Sensitivity analysis C2H5Cl Sensitivity Analysis Is a useful tool to know the respond of the output variable when the input is varied in a range. With this information one can appreciate which variable cause the biggest change in the process. Is easier to make a decision in the parameter we obtain best results.

  38. Sensitivity analysis C2H5Cl Ethyl chloride manufacture One of the routes to produce ethyl chloride is by the gas phase reaction of HCl with ethylene over a copper chloride catalyst: Objective: Observe the effect in “recycle” stream, “recycle” composition and “product” stream when the flow in “w” stream vary from 5 to 13 kmol/h.

  39. P=1 Atm. 10 kmol/h 90% conversion C2H4 DP=0 T=25 C P=1 Atm. P=1 Atm. T=25 C 50% mol HCl 48% mol C2H4 2% mol N2 P=1 Atm. C2H5Cl Pure Sensitivity analysis C2H5Cl Diagram

  40. Sensitivity analysis C2H5Cl Input to run Simulation • Give a name, and select the specific units to the process. • Select the compounds in the process.

  41. Sensitivity analysis C2H5Cl Input to run Simulation • Select the base method used to calculate the thermodynamic and transport properties.

  42. Sensitivity analysis C2H5Cl Peng – Robison Method It is recommended for hydrocarbon processing application such as gas processing, refinery, and petrochemical process. D.-Y. Peng and D. B. Robinson, "A New Two-Constant Equation-of-state," Ind. Eng. Chem. Fundam., Vol. 15, (1976), pp. 59–64.

  43. Sensitivity analysis C2H5Cl Input to run simulation • For feed stream, give the input data specified.

  44. Sensitivity analysis C2H5Cl Input to run simulation • For the mixer block give the next specifications.

  45. Sensitivity analysis C2H5Cl Input to run simulation • For the reaction block: Specifications Reaction

  46. Sensitivity analysis C2H5Cl Input to run simulation • For the “sep” block, enter the next input data

  47. Sensitivity analysis C2H5Cl Input to run simulation • For the “split” block, enter the next input data Now, it is possible to run the simulation. In order to create a sensitivity analysis, the next steps need to be added.

  48. Sensitivity analysis C2H5Cl Input to Sensitivity analysis • Chose model analysis tools from data menu, and then sensitivity.

  49. Sensitivity analysis C2H5Cl Input to Sensitivity analysis • Create a new sensitivity analysis case “weffect” Create the next three variables in the case.

  50. Sensitivity analysis C2H5Cl Input to Sensitivity analysis • In the vary tab, input the next data which is the variable range.

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