Question

Question 5 A fuel gas containing methane (CH) and ethane (CH) is burned with dry air in a furnace, producing a stack gas at 300 °C and 105 kPa (absolute). You analyze the stack gas and find that it contains no unburned hydrocarbons, oxygen, or carbon monoxide. You also determine the dew-point temperature. ICO concion a) If the fuel gas contains exclusively methane, what is the stack gas composition? What if the fuel gas is exclusively ethane? b) Estimate the range of possible dew-point temperatures by determining the dew points when the feed is either pure methane or pure ethane.co pet bord for c) Estimate the fraction of the feed that is methane if the measured dew-point temperature is 59.5 °C.

Answer 1

air a) The fuel gas in les il entuny CHg. co + 2H2O gas in boned in dry CHA +20, Since dry ex is used for combustions. Cs is sucopened by Nr. Assume air composition to be 26%0. 80% N2 7 2 miles. G 8 males of Na for I mole of CHq the exit gusis I mole 2 mole 8 mole CO2 42o. % Cor I too 1+2+8 1x100 - Il 4.09% % Ho=2 1d2t8 - 0781 = 18.189. 7 Nas = - 72-7 %. 0.72 Il here the total partial pressure of 420 x molefvatics preswex cs S stange with Cambier Peu, = 105 x 0.181 q koa

lare -2 when fuel ethane complety 2 26 Go to +3.502 0 +3lH2O 3.5 torresponds to N Ne 3.5 ㅈ 20 80 n=3.5x go 14 20 14 moles of Na 2 moles of CO2 3 holes of Hea at the exit Few Lomplete combus hien of one mole of Catto compontina 7. NE 14 x 100 = 73.6% 19+2 +3 ... Cara xoo 19 10.51 %. Ho= 38/00 a 19 15.7. Scavith

6.7 lose it when fuel Dew methane sempletly Partial pressure of H₂O= Total presne x mole freets =/05x 0.181 219 kpa. At Dewpoint for Saturated gason the gas mix mix is lool Saturated parting press me = Vapour pressure - from the steam table Ligurine find the temperature at which the I Saturation pressure 19 kpa Tg = 332.15k Deva point in len(1) = 332.15k. = 59.15°C And gas completty ethane. Pic 105* mole fration of H2o are - 2 کا 0 گو /2 16.485 kpn. a 329.1k 56. Loc cs Scanned with CamScanner

= 59.5 °C c.) if dew point Partial press me, should be should be equal to Vapon puersue at 59.5% b = 19.02. 19.07- ASSE +41 561) petes 19.02 a 19 +(1-1) 16.485 + 2-515 = 2-5 m n = 0.998 7 The mix is 99.8% methane o 2% ether Scanned with CamScanner ਜscanner ut

if the fuel gas was completly mathane then the dew pont was found to be 59.15 C, if it was completly ethane then dew point is 56.1 C

IF dew point is 59.5 then fuel is 99% methane.