Question

You are in charge of a combustion furnace. The furnace is fed an air stream and a methane stream which is combusted to produce heat that is used to boil water and produce steam for your plant. The combustion of fuels using an air stream which contains nitrogen generally produces significant amounts of NO, compounds which are an air pollutant, so the exhaust gases must generally be removed through various processes. In this case, your furnace exhaust is passed through a "wet scrubber" in which the gas is contacted with a water stream which absorbs the NO, compounds and that scrubber effluent stream is sent on for further treatment where the nitrogen compounds can be removed through conversion to harmless forms. stack exhaust air furnace exhaust Furnace Wet Scrubber methane scrubber effluent water You are given the following information on this process: 1. You are feeding 1000 mol/hr of methane to the furnace. 2. You are feeding air (79 mol% N2 and 21 mol% O2) at a flow rate such that there is an extra 25 mol% excess oxygen in the air stream relative to what would be needed stoichiometrically to combust the methane. This feed

Answer 1

CH₂ + 202 CO2 + 2H₂O Methane fed = 1000 mol/h. i. Oxygen stoichiometrically = 1.25 x/1000 x 2) At required d 2500 mol/h 1. Aill required to feed = 2500 x 100 = 11904.76 mollh I: Niterogen fed through air = 2500 x 79 - 9404 76 mol/h Out of this Na, only 1 1. is converted to No. 2 N2 + 202 - 2002 :: No converted = 94.0476 molha d e .. NO2 formed - 188.0952 molsh. : Whole amount of NO2 is discharged the cough through scumbber effluent as a molt so rest in the effluent will be water.

: Effluent water will be 188.095x98 -9069.655 molly This water will be 95% of that fed supplied to the scrubber. So water fed to the scembler = 90 69.655x100 95 = 95 47.005 mol/h. In the units of kg/h, water fed will be = 9547.005 X 18 kg/h TO00 = 171.846 kg/h. Cans). - 17.84 Hy is burnt at 1000 mol/ h. van alle So, coa is also produced at rate = 1000 mol. In the units of kg/h, coa emitted 1000 X 44 44 1000