Methane gas (CH4) at 25⁰C, 1 atm enters a steam generator operating at steady state and burns completely with 140% of theoretical air entering at 127⁰C, 1 atm. The products of combustion exit at 427⁰C, 1 atm. Kinetic energy and potential energy effects are negligible. If the rate of heat transfer from the furnace to the surroundings is 400 kW, determine the mass flow of methane, in kg/s

Write the complete combustion equation of with the theoretical amount of air,

CH4 + a ( O2 + 3.76N2) = b CO2 + yH2O + q

Where

a is alpha, b is beta, y is gamma and q is Delta.

Find the values of coefficients by applying conservation of mass principle to carbon, hydrogen, oxygen and nitrogen.

Carbon:

1 = b

Hydrogen

4 = 2y

y = 2

Oxygen,

a = b + y/2

a= 2

Nitrogen,

a(3.76) = q

q = 2 x 3.76

q = 7.52

Explanation:

Applying the First Law to Reacting Systems

Methane (CH4) at 25°C, 1 atm enters a furnace operating at steady state and burns completely with 140% of theoretical air entering at 400 K, 1 atm. The products of combustion exit at 700 K, 1 atm. Kinetic and potential energy effects are negligible. If the rate of heat transfer from the furnace to the surroundings is 400 kW, determine the mass flow rate of methane, in kg/s.

the answer is 75.0%.