Question

Biogas from a digester containing 52.8% CH4, 16.4% H2, 13.5% CO, and the rest Nis used as a fuel in a makeshift stove that allows for the inclusion of 18.5% excess air. Determine the complete molar composition of the flue gas and its absolute humidity, assuming complete combustion and that the flue gas exits at normal atmospheric pressure.

Answer 1

Date Page No. Basis- solu, 100 mol of Biogas Chy H₂ → 52.8% 16.4% 13.51 52.8 mole 16. 4 mole 13.5 mole 82.7 mol Total 201 moita udho i moles of N₂ in Biogas = 100 - 82.7 - 17.3 mole Combustion Reaction - tus slo Chyt 20₂ CO₂ + 2H2O - dor H₂ + I O2 그 H20 co + 1₂ lan CO₂ 3 2 a. from reaction 1, & mole Cry requires requires 2 moles O₂ 58 52.8 mole Chy requires 52.8x2 = 105.6 mole 02 for complete combustion. from reaction 2, 1 mole H2 requires I mole O₂ U foney . 16.4 mole H₂ requires 16.4_ 8.2 molete Il glom &osa 2 2

Date Page No. From reaction ) on 1 mole co requires mole Oz. 13:5 mole to requires 13.5 26.75 mole 2 2 02 - Total Total oxygen required for complete combustion 105.6+8.2+ 6.75 001 0185 120.55 moles 02 slow= But O₂ is passed in excess = 18.5% o moles of O₂ supplied = 'moles of a required X (100+ % exces) too . moles of O₂ supplied = /20:55*11185 142.85 moles O2 Now, Air contains 21% O2 & 79% N2. . Amount of Na paned through air al slom d.204 *9.2 Editalama -tea142.85 79= 537,4 moles N2 21 money YYOR slon Again from rxn. O, 1 mole Chy produces 1 molecos & 2 mole H₂O 52.8 mole Cry will produce 52.8 x 1 mole co, & 52.8x2 mole H₂O

Date Page No. 2 52.8 mole con + 105.6 mole H2O from Reaction 2, 1 mole He gives 1 mole H₂O to to 2 16.4 mole H₂ gives 16.4 more H₂o, from Reaction 3, 1 mor co. produces I mole co2 2) 13.5 mole co produces 13.5 mole co2. al Also, oxygen w consumed 2 120.55 2. Oxygen unreacted = 142.85-120-55 22.3 moles O2 holow Also, N2 in product gas a Na in Biogas + N2 from Air - 17.3t 537.4 = 554. I mole 1. . Product Gaster Total & Co, 52.8+ 13.5=66.3 mole Total H₂O - 105.6+16.4 = 122 mole 02 22. 3 mole Total N2 554. f mole Thus Outlet air has composition, 554.7 mole N₂ + 22.3 mole O₂ 577 mole of Air Now, of N2 in air mole fraction 554-7 577 96

Map Page No Osta mole fraction of O2 in outlet flue gas (Air) 1962-04.on OSH bo to vie stom Average Molecular weight of air t.04 Moz 2.96 x 28 4.04832 slovoz bo 28.16 g/mol 96X MN2 a) Haz zzo. Absolute Hu Humidity a kg of H₂O 01 - 1129.- betoner Opp kg of Air moles of H₂0 x 18 moles of Air x 28116 Cop Lowaram xha Ha a 122 A an.2a Nite 577 28.16 copaffet Hiu Ha = .135 kg of H2O 2.ET +9:52 MED kg dry Air slun totul