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045330 – Simulation Laboratory © D. R. Lewin 2004 Lessons 12 - 13: Project – Part 3 Now that you have mastered all of the building blocks in HYSYS.Plant, and you have developed the reaction and separation sections of the process for the manufacture of benzene from toluene, you will now integrate both parts of the process into a single flowsheet, while applying some engineering judgement. Here is what you have to do: 1. Complete a simulation of the entire process for the hydrodealkylation of toluene. The process must satistfy ALL of the following specifications (simultaneously): a. Benzene product flow rate must be at least 20,000 lb/hr b. Benzene product must have a benzene mole fraction of 0.99 c. Feed stream to the heat exchanger (after the quench) must be at 1150 o F. d. Molar ratio of hydrogen/toluene entering the reactor must be 1.5. e. Fuel gas product (methane and hydrogen) – which is the combination of the purge after the separator and the overhead product of the first distillation column – must have no more than 1% (molar) pollutants. 2. Bonus sections: To qualify for bonuses, you need to do at least one of the following modifications: a) Suggest an alternative plant structure (additional separation between toluene and biphenyl or a side draw in the second column). Discuss the differences and relative advantages of the different structures (heat requirements, equipment sizes, etc.) b) Suppose the reboiler of the benzene column develops a fault, and only 70% of its design duty is available. Discuss the effect of this fault on the five specifications you were able to satisfy in Part 1. What requirements can still be met in light of this problem c) Replace the reactor with a PFR, referring to the Appendix of this document, and discuss the results. How does the dependence on concentrations influence the solution. Are the assumptions for the conversions (75% and 2%) accurate? d) Setting the hydrogen feed flowrate to 450 lbmoles/hr, perform a case study changing the two purge ratios (between 0.05 and 0.95 each) to find the range of feasibility such that the following sepecifications are met: a. Gas recycle mass flow of no more than 2,000 lb/hr. b. Liquid recycle mass flow (rich in toluene) no larger than 5,000 lb/hr. c. Benzene product mass flow rate no less than 16,500 lb/hr. d. Molar ratio between hydrogen and toluene entering the reactor no less than 1.5. e. Benzene product contains no less than 99% benzene by moles. The project will be completed by students working in pairs. The project will be submitted as a report in WORD, completed according to a report format as given (see the website for more
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045330 Simulation Laboratory
D. R. Lewin 2004
Lessons 12 - 13: Project Part 3
Now that you have mastered all of the building blocks in HYSYS.Plant, and you have developed the reaction and separation sections of the process for the manufacture of benzene from toluene, you will now integrate both parts of the process into a single flowsheet, while applying some engineering judgement. Here is what you have to do:
1. Complete a simulation of the entire process for the hydrodealkylation of toluene. The process must satistfy ALL of the following specifications (simultaneously):
a. Benzene product flow rate must be at least 20,000 lb/hr b. Benzene product must have a benzene mole fraction of 0.99 c. Feed stream to the heat exchanger (after the quench) must be at 1150 oF. d. Molar ratio of hydrogen/toluene entering the reactor must be 1.5. e. Fuel gas product (methane and hydrogen) which is the combination of the purge after
the separator and the overhead product of the first distillation column must have no more than 1% (molar) pollutants.
2. Bonus sections: To qualify for bonuses, you need to do at least one of the following modifications: a) Suggest an alternative plant structure (additional separation between toluene and biphenyl or
a side draw in the second column). Discuss the differences and relative advantages of the different structures (heat requirements, equipment sizes, etc.)
b) Suppose the reboiler of the benzene column develops a fault, and only 70% of its design duty is available. Discuss the effect of this fault on the five specifications you were able to satisfy in Part 1. What requirements can still be met in light of this problem
c) Replace the reactor with a PFR, referring to the Appendix of this document, and discuss the results. How does the dependence on concentrations influence the solution. Are the assumptions for the conversions (75% and 2%) accurate?
d) Setting the hydrogen feed flowrate to 450 lbmoles/hr, perform a case study changing the two purge ratios (between 0.05 and 0.95 each) to find the range of feasibility such that the following sepecifications are met:
a. Gas recycle mass flow of no more than 2,000 lb/hr. b. Liquid recycle mass flow (rich in toluene) no larger than 5,000 lb/hr. c. Benzene product mass flow rate no less than 16,500 lb/hr. d. Molar ratio between hydrogen and toluene entering the reactor no less than 1.5. e. Benzene product contains no less than 99% benzene by moles.
The project will be completed by students working in pairs. The project will be submitted as a
report in WORD, completed according to a report format as given (see the website for more
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045330 Simulation Laboratory
D. R. Lewin 2004
information, and please follow the instruction carefully). The following items need to be submitted to the webct site as a zipped file, named group_xy.zip (where xy is your group number) to to course website:
1. Report in WORD. A template for the report is provided on the website. 2. A separate HYSYS case file for each part of your solution.
The report should include the following items: a. Cover page, including the names and i.d. numbers of the group members and the group
number. b. Contents page. c. Detailed list of HYSYS file names and a brief description of their contents. d. Executive summary of up to 1,000 words, which summarize the work accomplished and
describe the main results. This summary should be sufficient to judge the quality of your work, so make it good!
e. Main body of the report (refererred to in the execuitive summary), containing: i. Description of work-steps, namely, the reactor and separation sections and
their combination in the overall flowsheet. ii. Description on the completion each of the bonus sections attempted, and the
conclusions obtained. iii. Presentation of graphs and tables as needed.
Note: we are looking for evidence of the correct use of engineering judgement in all steps of the project. Show us that you know what you are doing!
You must request a group number by sending a list of two names to Alex by email to: [email protected]
The deadline for submission of your project to the website is 15th JULY, 12:00. Note that the site not be available for project submissions after that time.
Grading: As you know, the project is worth 80% of the course grade. The maximum project grade depends on whether or not a group attempts at least one of the bonus sections, as per the table below.
Maximum Project Grade Possible No bonus questions attempted 60 One bonus question attempted 80
At least two bonus questions attempted 100
Warning: Copied work is unacceptable. In the event that copies of the same work, or variations of the same piece of work, is submitted by two or more groups, all groups will receive a grade of zero for the project.
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045330 Simulation Laboratory
D. R. Lewin 2004
Appendix: Kinetic Data for Reactions for Hydrodealkylation of Toluene. Source: http://www.che.ttu.edu/classes/che5000/EmetsThesis.pdf
Gas Constant: R= 3.57458 [BTU/lbmole-K] -------------------------------------------------------- E1=2.56161043.57458 = 91,566 [BTU/lbmole] E2=1.53621043.57458 = 54,913 [BTU/lbmole] E3=1.22371043.57458 = 43,742 [BTU/lbmole]
