Ammonia is produced in a process consisting of two distinct sections. The first,

Question

Ammonia is produced in a process consisting of two distinct sections. The first, the "Synthesis Gas Section", (not shown) is where methane is converted to CO, H2, and other species. Pure N2 is added in a mixer unit, and a separation train is used to remove CO, CO2, and H20. The second section shown below, the "Ammonia Synthesis Section", is where N2 and H2 are reacted to form NH3. To increase conversion, a recycle stream is used. To reduce the accumulation of inerts, a purge stream is also used. Reaction in Ammonia Reactor: N2+ 3 H2 2 NHy Assume B 200 moVs with 4 mol% CH4, 24 mol% N2, and 72 mol% H2. The purge stream P is set such that the CH composition is 20 mol% and Recycle flowrate/Purge flowrate- RUF-3. The product stream N is pure ammonia and all of the ammonium is recovered in this stream. Ammonia Synthesis Section Purge P) le (R) Ammonia Condenser 2 Reactor Ammonia Product (N) l. (80 points total) (a) (0 points) Perform a -of-freedom analysis on the overall ammonia synthesis degrees section. Write your unknowns and equations.

Explanation / Answer

a)unknowns

purge flowrate-P

recycle flowrate-R

product flowrate-N

b)on 1 second basis

Amount of CH4 entering the reactor=200*4/100=8 mol

purge=P

amount of CH4 removing with purge=P*20/100=8 mol

therefore P=40 mol/s

R/P=3

therefore R=120 mol/s

d)overall conversion of N2=(mols of ammonia produced*stoichiometric factor/mols of reagent fed)*100

   mols of N2 fed=200*24/100=48 mols

mols of ammonia produced=48*2 mols because 1 mol of N2 produce 2 mol of NH3

stoichiometric factor=2

mols of reagent fed =200 mols

overall conversion=(96*2/200)*100=(192/200)*100=0.96*100=96%

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