5 790 t 1000c air 1000 079 021 t 100c furnace ch4 h2o

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Unformatted text preview: s that there are 2 moles O2 required per mole of CH4 for complete combustion. Thus the feed rate of oxygen for complete combustion is 200 mol/min. The actual feed rate is 0.21 (1000) = 210 mol/min. Thus there are 210 – 200 = 10 mol/min excess oxygen being fed to the system. Thus the percent excess oxygen (air) is 2 5.00% 2 100% 10 100% 200 A hydrogen balance gives 2 4 4 100 2 200 / To determine how much heat is transferred construct an enthalpy input/output table. Compound CH4 CO CO2 H2O O2 N2 (mol/min) 100 210 790 (kJ/mol) (mol/min) 5 95 200 12.5 790 (kJ/mol) We need to select a reference state for the enthalpies. Let’s select the elements at 25°C as our reference. Since the methane feed is at 25°C this entry will be the heat of formation of methane at 25°C which is -74.85 kJ/mol from Table B.1. The enthalpies for oxygen and nitrogen can be looked up in Table B.8. For CO, CO2, and H2O take the heat of formation from Table B.1 and add the enthalpy from Table B.8. This gives 110.52 393.5 241.83 30.91 48.60 37.69 Thus the input/output enthalpy table looks like 79.61 / 344.9 / 204.14 / Compound CH4 CO CO2 H2O O2 N2 (mol/min) 100 210 790 (mol/min) 5 95 200 12.5 790 (kJ/mol) -74.85 2.24 2.19 (kJ/mol) -79.61 -344.9 -204.14 32.47 30.56 The energy balance then gives ∆ 5 79.61 95 100 344.9 74.85 200 204.14 12.5 32.47 210 2.24 790 2.19 44,200 / min 736 736 790 30.56...
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