Determine the concentration of the exhaust gas and

Question

Question 1. A mixture of 65 mol% methane, 30 mol% hydrogen, and 5 mol% nitrogen is burned to heat a boiler used to produce hot steam. Unfortunately, the burner has corroded, leading to poor performance and the production of carbon monoxide. 

The ratio of CO₂ to CO in the exhaust gas is 10:1. If 30% excess air is supplied, determine the concentration of the exhaust gas. Note, all of the methane and hydrogen is consumed.

Question 2. Natural gas composed of 60.mol% methane, 30.mol% ethane, and 10.mol% propane at 25 °C and 500.psia is fed at a rate of 50.m³/hr into a boiler. In the boiler it is blended with enough air to provide 20% excess oxygen and combusted. The exhaust gas is passed through several air pollution control unit operations before being released through a smokestack into the atmosphere at a temperature of 400 °C. Determine the flow rate (in m³/hr) of exhaust gas through the smokestack.

Answer should be (v = 79400 m³/hr)

Question 3. Hydrogen cyanide (HCN) is an important precursor in the production of organic polymers, e.g. methyl methacrylate (used to produce Plexiglas). One method of producing hydrogen cyanide is via the catalytic reaction of nitrogen and acetylene. The reaction is given by:

N₂ (g) + C₂H₂(g) -> 2 HCN(g)

Due to thermodynamic constraints the single pass conversion is low (15%), and therefore a recycle stream is required. The gas stream exiting the reactor is cooled in a condenser to produce a product stream and a recycle stream. A schematic of the reactor is shown below.

If it is desired to produce 15,000 kg/hr of HCN, determine: (answers in brackets)

a) The number of moles per hour and the percentage composition of the material leaving the reactor (point X). (nN₂ = nC₂H₂ = 1572 n_HCN = 554.9)

b) The recycle to fresh feed ratio. (n_recycle/n_fresh = 5.7)