Question

A fuel gas containing 85.0 mole% methane and the balance ethane is burned completely with 15.0 % excess air. The stack gas leaves the furnace at 900.0 °C and is cooled to 450.0 °C in a waste-heat boiler, a heat exchanger in which heat lost by cooling gases is used to produce steam from liquid water for heating, power generation, or process applications. Physical Property Tables Combustion Gases Correct. Take as a basis 100.0 mol of the fuel gas fed to the furnace. Calculate the amounts of each of the following gases leaving the furnace at 900.0 °C. O2 33.75 mol 962 mol 115 mol mol

Answer 1

* Mole percent of methane - 85% Mole percent of ethane = 15% Basis: 100 mol of fuel gas. Molar flow of methane = 0.85 x 100 - 85 mol. Molar flow of ethane - 0.15x100 - 15 mol #11798888ILIISISSIT!!!!!!!!! Reaction Envoles are : + chy & 202. 85 mol 85x2 mol CO2 85 mol. 0 85*2 mol. ② C₂ H + 702 15 mol. 7 x 15 mol. 2202 + 3H₂O 2x15 mol. 3x15 mol. For reaction 0, An 85 mol of methane requires (85x2) mol of oxygen for complete combustion and forms 85 mol of CO2 and (85x2) mol of H₂O. -For Bell reaction 2, As 15 mol of ethane requires (1/2 x 15 mol of oxygen for complete combustion and forms (2x15) mol of coa and (3x15 mol of H₂0. a

in Total oxygen required = (85x2) mol + 17 x 15) mal - 22205 moles. A 1 mol of air will have 0.72 mol of Nitrogen & and 0.21 mol of oxygen. Amount of air required - 222.5 moles 0.21 – 1059.52 moles air is supplied for the As 15% of excess combustion. Air supplied = 1218.45 moles Amout of oxygen in air = 2009 O-21X1218:45 = 255.87 moles. Piggest usest Hoy teaction (200R-220 S oxygen issed by reaction - 222.5 moles Excess oxygen which go along the flue gas/ = (255-87 - 222.5) moles - 33.37 moles,

Amount of flue gas Nitrogen in air which will go with a = (0.79 x 12 18.45) moles = 962058 moles. a Amount of coa in flue gas = coa formed in reaction 0 + co2 formed in reaction - 85 moles + 2x 15 moles = 115 moles. Annount of H₂O in flue gas = H2O formed in reaction + H2O formed in reaction ® = (8582) moles +(3x15) moles = 215 moles. ases are: - Molar flow rates of flue gases O2 = 33.37 moles. Ny - 962 58 moles. Co2 = 115 moles H₂O = 215 moles ::886060666......!! us

* of Specific heat capacity (Cp) of O2 = 34.841 5 1 cp values molk are N₂= 33.606 I taken from molk NIST Webbook CO2- 55.35 J H2O = 43.456 5 molk molk The amount of heat supplied from free gas to waste heat boiler to get cooled from 9000 to 450°c is i = components = Imi (p: (AT) mi-molar flow = 2 micpi (900+273 - rate of components (Pi = specific heat 450 +273) capacity of components. = (mo, x CPO2 + MM2 x CPN2 + m coa xe con te MHBOX CPH2O) + (900-450) - (33.3734.841 +962.58% 33.606 + 115X 55.35 + 215 X 43. - 22148728.94 5 22.1487 MJ ins