1. Tier 2
Use of computer as a
simulation tool

2. Use of computer as 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.
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. Table of content Contents 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. Solving Closed 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. Algorithm Closed problems Write out the problem statement.
Draw and label a sketch.
List assumptions and approximations involved in solving the problem.

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

9. Some advice when running a simulation
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. Some advice when running a simulation
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. Some Advice when running a simulation
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. Some Advice when running a simulation
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. Commercial Simulation Software Packages
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 resolution with spreadsheets

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

16. Solving problems with Advance mathematics software

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

18. Reaction profile of the pulp digester
Advance mathematic software
Reaction profile of the pulp digester

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

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

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

22. Using specialized software to simulate a process

23. What do more advanced simulation package offer?
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. Advantage of specialized software
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. Problem statement NH4 – H2O separation
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. Giving name, and selecting units to use
NH4 – H2O separation
Giving name, and selecting units to use

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

30. RK-Soave NH4 – H2O separation
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. Specify the assumption made, and the characteristics in the feed.
NH4 – H2O separation
Specify feed stream
Specify the assumption made, and the characteristics in the feed.

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

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

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

35. What can be done with simulation
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 of C2H5Cl manufacture

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

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

42. Peng – Robison Method Sensitivity analysis C2H5Cl
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. Input to run simulation
Sensitivity analysis C2H5Cl
Input to run simulation
For feed stream, give the input data specified.

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

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

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

47. Input to run simulation
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. Input to Sensitivity analysis
Sensitivity analysis C2H5Cl
Input to Sensitivity analysis
Chose model analysis tools from data menu, and then sensitivity.

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

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

51. Input to Sensitivity analysis
Sensitivity analysis C2H5Cl
Input to Sensitivity analysis
In the tabulate tab, select the way to tabulate the results.
Run the simulation.

52. Results in sensitivity analysis
Sensitivity analysis C2H5Cl
Results in sensitivity analysis
Flow rate of the “product” stream decreases linearly as “W” is increase.

53. Results in sensitivity analysis
Sensitivity analysis C2H5Cl
Results in sensitivity analysis
As a “W” flowrate increases, the recycle flow decreases exponentially. When “W” is 13 Kmol/hr, the flowrate at the recycle stream is less than 1.

54. “w” flow rate vs. N2 composition of the recycle stream
Sensitivity analysis C2H5Cl
“w” flow rate vs. N2 composition of the recycle stream
The nitrogen fraction of the “recycle” stream is 40% when the “W” is 5 kmol/h. As this is increased to 13 kmol/h the nitrogen mol percentage falls to less than 10%.

55. Conclusion from the simulation
Sensitivity analysis C2H5Cl
Conclusion from the simulation
With this kind of analysis, one can appreciate how sensitive is the process to the change in one variable, in this case “W” flowrate.
In which cases the process behaves with a benefit to the production.

56. Optimization

57. Optimization Optimization
Is a way to simulate the process, making some special consideration, just like, maximize or minimize a stream or a composition, with the corresponding constrains.
objective function.
set of m equations in n variables x.
Constraints
set of r inequality constraints. Bound the feasible region.

58. Problem statement Optimization
Maximize the venture profit of the ethyl chloride process by adjusting the purge “W” flow rate.
Subject to:
Recycle < 300 Kg/h
g(x)=0 (Mass balance)
100 kmol/hr
50% HCl
48% C2H4
2% N2
Pure C2H5Cl

59. Additional information supplied
Optimization
Additional information supplied
Installed cost of equipment.
FR reactor feed rate [Kg/h]
Cost of ethylene.
Cost of HCl.
Revenue for ethyl chloride.
Assuming a 10% return on investment ROI.
330 operating day/year.

60. Objective Function Optimization Maximize Venture Profit VP:
P – product stream.
F – feed stream.
S2 – stream 2.
xEt – mass fraction of ethylene in feed stream.
xHCl – mass fraction of chloride acid in feed stream.

61. State an Optimization problem
Once the flowsheet is created, and the simulation has been run, it is time to create an optimization case.
Creating an optimization case.

62. Optimization
Variable definition
All variables are defined in a similar way

63. Optimization
Defining the constrain
Recycle variable is
subject to:
R < 300 Kg/h

64. Introducing the objective function as the statement maximize.
Optimization
Introducing the objective function as the statement maximize.

65. Optimization
Defining the manipulate variable and the limits to adjust, so we can achieve the specify objective.

66. Check the results Optimization
We can now determine which recycle flow maximize the venture profit.
As seen here: “W” 0.49 and Recycle 0.509, is almost 50 – 50.

67. Mass flow rate Optimization
The recycle stream mass flow rate has set 300 kg/h, the upper limit of the specified stream.
We can also check the flow rate in the purge “W” 8.96 Kg/h calculated in the simulation.

68. End of Tier 2