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Ethylene oxide (C2H4O) is a high-volume chemical intermediate that is used to produce glycol and polyethylene glycol. Ethylene oxide is produced by the partial oxidation of ethylene (C2H4) on a solid catalyst in a fixed bed reactor: C2H4 + 1/2O2 ? C2H4O. A portion of the ethylene reacts in an undesired reaction to form carbon dioxide and water: C2H4 + 3O2 ? 2CO2 + 2H2O. The product gas leaving the reactor has the following water-free composition: 20.5% C2H4O, 72.7% N2, 2.3% O2 and 4.5 % CO2. Determine the % excess air (based on the desired reaction) and the lb/hr of ethylene feed required to produce 100,000 ton/yr of ethylene oxide.

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Related questions

Ethylene oxide is produced by the catalytic oxidation of ethylene:

2C2H4 + O2 → 2C2H4O

An undesired competing reaction is the combustion of ethylene:

C2H4 + 3O2 → 2CO2 + 2H2O

The feed to the reactor (not the fresh feed to the process) consists of 3.00 moles of ethylene per mole of oxygen.

The single-pass conversion of ethylene to either ethylene oxide or carbon dioxide is 15.0%, and for every 100.0 moles of ethylene consumed in the reactor, 90.0 moles of ethylene oxide emerges in the reactor products.

A multiple-unit process is used to separate the products: ethylene and oxygen are recycled to the reactor, ethylene oxide is sold as a product, and carbon dioxide and water are discarded.

Assume a quantity (100.0 mol/h) of the reactor feed stream as a basis of calculation, draw and label the flowchart, perform a degree-of-freedom analysis, and write the equations you would use to calculate (i) the molar flow rates of ethylene and oxygen in the fresh feed, (ii) the production rate of ethylene oxide, and (iii) the overall conversion of ethylene.

a. Calculate the following quantities.

Molar flow rate of ethylene in the fresh feed: mol/h C2H4
Molar flow rate of oxygen in the fresh feed: mol/h O2
Production rate of ethylene oxide: mol/h C2H4O
Overall conversion of ethylene: %

b. Calculate the molar flow rates of ethylene and oxygen in the fresh feed needed to produce 1 ton per hour of ethylene oxide.

Molar flow rate of ethylene:

lb-mol/h C2H4
Molar flow rate of oxygen: lb-mol/h O2

Nitric acid may be produced by oxidizing ammonia to nitric oxide over a platinum-rhodium catalyst, then oxidizing the nitric oxide to nitrogen dioxide in a separate unit where it is absorbed in water to form an aqueous solution of nitric acid. The three key reactions in the synthesis are the oxidation of the ammonia to nitric oxide and of nitric oxide to nitrogen dioxide, followed by dissolution of the NO2 in water:

4NH3(g)+ 5O2(g)→ 4NO(g)+ 6H2O(g)

2NO(g) + O2(g) → 2NO2(g)

4NO2 (g)+ 2H2O(l) + O2(g) → 4HNO3(aq)

In this problem, you may neglect side reactions that would lower the product yield. This would include the side reaction in which ammonia is oxidized to form nitrogen and water which can lower product yield.

4NH3 + 3O2 → 2N2 + 6H2O

Thus, for this project the overall reaction may be represented from the three key reactions above as:

NH3 + 2O2 → H2O + HNO3

Ammonia vapor at 275oC and 8 atm is mixed with air, also at 275oC and 8 atm, and the combined stream is fed to a converter. Fresh air entering the system at 30oC and 1 atm with a relative humidity of 50% is compressed to 100oC and 8 atm, and the compressed air then exchanges heat with the product gas leaving the converter. The quantity of oxygen in the feed to the converter is 20% in excess of the amount theoretically required to convert all the ammonia to HNO3. The entire process after the compressor may be taken to operate at a constant pressure of 8 atm.

In the converter, the ammonia is completely oxidized, with a negligible amount of NO2 formed. The product gas leaves the converter at 850oC and exchanges heat with the air leaving the system as described earlier. The product gas is then fed to a waste-heat boiler that produces superheated steam at 200oC and 10 bar from liquid water at 35oC. The product gas leaving the waste-heat boiler is cooled further to 35oC and fed to an absorption column in which the NO is completely oxidized to NO2 which in turn combines with water (some of which is present in the product gas). Water is fed to the absorber at 25oC, at a rate sufficient to form a 55 wt% aqueous nitric acid solution. Any NO formed in the reaction of NO2 to produce HNO3 is oxidized and the NO2 produced is hydrated to form still more HNO3. The off-gas from the process may be taken to contain only N2 and O2 and at 25oC and 1 atm.

b). Taking a basis of 100 kmol of ammonia fed to the process

(i) kmol of water fed to the absorber

(ii). Temperature of the product gas after it has exchanged heat with the air, assuming no heat is transferred between the heat exchanger and the surroundings

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