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Problem Set 9

# Problem Set 9 - procedure along with the spreadsheet and...

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Chemical Engineering 140 October 21, 2009 Problem Set #9 42. Consider the example done in class of ammonia production with recycle and complete separation of ammonia by condensation. The synthesis gas composition and reactor conditions are the same as that in the class example, 900 ° F and 300 atm. However, the inert gas composition at the reactor entrance is no longer set, but rather the recycle ratio. a. Calculate the overall conversion and the gas composition at the inlet to the reactor for a recycle ratio of 4 and a single-pass conversion of 20 %. Be careful about round-off error in this calculation. b. Prepare an Excel spreadsheet to give the overall conversion for a range of single-pass reactor conversions. Also, prepare a graph of overall conversion versus single-pass conversion. What do you conclude? Please explain. You are to hand in your solution
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Unformatted text preview: procedure along with the spreadsheet and the graph. 43. The reaction rate for the production of ammonia on a promoted iron catalyst is written at 300 atm as 2 2 3 2 3 2 2 3 2 2 2 1 1 2 2 3 2 N H NH N / / NH H H k [ y y y /( K P )] r [ y y y ] β--= + where at 900 ° F, β = 0.00140, k 1 = 1.20 lbmol/ft 3 hr, and K = 4.67(10-3 ). For the ammonia plant described in problem 42 above and producing 40,000 ton/yr of ammonia, you are to find the volume of the plug-flow reactor at 900 ° F and 300 atm with a recycle ratio of 4 and a single-pass conversion of 20 %. a. Obtain the rate expression for the reactor in terms of single-pass conversion. Do not neglect the inerts in your expression. b. Using the result in part a above find the reactor volume numerically. Page 1...
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