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Material and Energy BalancesEthylene Glycol Production

Lecture Team:Prof. Dr. Turmuzi Lubis, MS

Dr. Iriany, MSiIr. Barnbang Trisakti, MSi

Design Praject

Ethylene glycol is a rnajor component in some antifreeze formulations. Your boss has

recently become interested in exploring the feasibility of producing ethylene glycol. She has

requested that you answer some questions, run some calculations and suggest some design

altematives associated with the production of ethylene glycol. In order to do that she has

supplied you with the following information:

Ethylene glycol is produced using reactors that catalyze two different reactions. In the firstreactor, ethylene is mixed with air and oxidized to etlrylene oxide in the gas phase. The

unbalanced reaction is

CzFI++Oz*CzHtOz

Complete combustion of the ethylene can also occur as a side reaction. In the reactor assume

all of the oxygen is consumed, This gas effluent is fed to an absorption column, where wateris added and used to separate unreacted ethylene from the remaining mixture. The waterstream enters a distillation column which separates water from the remaining components andanother absorytion column uses triethanolamine to pull carbon dioxide out of the ethyleneoxide. This ethylene oxide feed is send to a second reactor with a water feed to generate

ethylene glycol:

C2H4O *HzO- C2FI4(OH)2

However, there is a side reaction

C:FIaO + C2H4(OH)z - (CzFIqOH)rO

producing diglycol. Ethylene oxide is highly reactive and consequent$ there is completeconversion. After the sticond reactor there is one distillation column to separate water and asecond distillation colwnn to separate diglycol and ethylene glycol.

Open-ended questions:

1. What is the yearly world production rate of ethylene glycol?2. Are there any uses for dirylcol?

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3. How is etlrylene produced?

4. Draw a process flow diagram that does not include process variables, but does include thestrearn components.

5. Identify every sepa.ration unit and describe how it separates the materials.6. Are there alternative separation units that night be used for this process?

7 . Wlrat are the envirorunental concerns associated with this process?

8. What are the safety concerns associated with this process?

Process calculations:

t. Calculate the heat transfer rates of the first reactor if the reaction.is conductedisothermally at 200 oC. Assume the ethylene feed is 1500 lbm/hr and the selectivity ofethylene oxide to the combustion of ethylene is 20:1 and the conversion of ethylene is60%. Calculate the heat transfer rate as a firnction of selectivity.

2. In the absorber, assume that you have access to water at 20 oC and treat the absorber as anequilibrium device. What are the concentrations of components in the outgoing streams?How much enerry do you need to remove or add to the absorber in order to have exitsfteams at 2A "C? Hint: Assume carbon dioxide, water and ethylene glycol can exit viaboth the liquid and vapor streams. How does the answer differ as a function ofternperature?

3. Calculate the exit temperature of the second reactor if the input streams are at 20.C.Assume that the conversion of ethylene oxide is complete, the inlet feed of ethylene oxideis equal to the molar flow rate of ethylene oxide exiting reactor one and only 10 vtf/o ofthe exit sffeam is diglycol. How does the temperaturo change as a function of diglycolwtoA?

4. Why is a distillation column used rather than a flash tank to separate water from atryleneoxide? In order to answer this, make some equilibrium calculations based on anequimolar flow of water and ethylene oxide into a flash tank to show how pure the"water" and "ethylene oxids" streams are. You may nm the flash tank at any temperaturethatyou want.

Design:

1. Assume that the price for 20 "C ethylene is $1,400/metric ton, ak at Z0 oC is free andwater is $1.S/metric ton. Ethylene oxide is $1,800/metric ton and diglycol is l,300lmetricton. Energy to heat and cool processes is $0.06/kW-hr with i dernand charge of$9/kWimonth. Ignore energy input into the final two distillation columns and assumepure streams exit the distillation colururs (both poor assumptions). Use the informationabove to calculate how much profitlhr this process will generate.

2. Suggest improvements to the process (rerycle, bypass, utilizing waste heat streams) tomake the process more cost effective. Recalculate process variables in the processcalculation section and recalculate the profit/hr this proclss will generate.

Project teams:Teams of three or four students will work together on the design project. All team membersmust be actively involved in arriving at the final design. A single grad" will be given to eachteam based on the project design report due Thursdayn Janua 10th, 201i. Teams areencouraged to explore/utilize aLl available resources (e.g., computing facilities, books,manufacturer/organization web pages and other library resources) to cornplete the project.

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However, collaboration between teams is not permitted. If your team should have specificquestions concerning the questions, calculations or design strategies, contact the class lectme.

Each team must have at least two meeting with the lecture over the course of the project

development. This must occur before I)ecember 31th,2012.

Design report to be submitted:The final design report should be prepared in a professional marmer, and should be presented

as a formal report to yow boss. The repbrt should contain the following:1) A cover letter (l page max) describing your design recommendations, calculation results

and a brief summary of the answers to the open-ended questions.

2) An innoduction with a brief overview of the process which include answers to the open-

ended questions. This section ofthe report should include a process flow diagram.3. Process calculations made on engineering paper. Include figures and tables to present key

data (computer programs, spreadsheets, list of source materials can be placed in an

Appendix).4. Economic calculations on engineering paper and a description of the final design. This

section should include the new process flow diagram and should fully explain whychanges in the process were made.

5. A citation list of all references. ALL SOURCES MUST BE CITED.6. Parts 2 and 4 should be no more than 3 pages single spaced. Calculations do not have a

page limit.

Timeline:o Open-ended questions (report pmt#2) week Io Process calculations (report part #3) week 1-2o Desigr (report part #4)) week 2-3. Cover letter (report part #l) and asse,mbly, revision and proofing of document (report part

#5 and #6) week 4

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