Question

6.Coke can be converted into CO according to following reaction CO2(g) + CO 2 CO A H, = 74210 Btu/lb-mole A coke that contains 84 % carbon by mass and the balance noncombustible ash is fed to a reactor with a stoichiometric amount of CO2. The coke is fed at 77°F, and the CO, enters at 400°F. the percentage conversion of the carbon in the coke is 80%. The gaseous products and the solid reactor effluent (the ash and unburned carbon) leave the reactor at 1830°F. The heat capacity of both solid carbon and ash is 0.24 Btu/(Ibn.°F). Calculate the heat transferred to the reactor in Btu/lbn of coke fed.

Answer 1

given,

Heat of reaction = 74210 Btu / lb-mole

Coke contain 84% carbon and 16 % ash

Entering and exit temperature = 77 ⁰ F & 1830 ⁰ F

Heat capacity of carbon and ash = 0.24 Btu / lbm ⁰F

CO₂ + C === 2 CO

Suppose 100 lbm coke so carbon = 84 lbm & 16 lbm ash

84 lbm of carbon = 84 / 12 = 7 lb mole of carbon and stoichiometric CO₂ = 7 lb mole

Conversion is 80 % carbon unreacted = 20 %

0.2 * 7 lbmol = 1.4 lbmol = 1.4 * 12 = 16.8 lbm and ash = 16 lbm

total coke ( carbon + ash) = 16 + 16.8 = 32.8 lbm

from stoichiometric every mole of coke 2 mole of CO produced

For 7 mole of coke 0.8 * 7 = 5.6 mole CO produced

heat transfer = Heat of reaction for 100 lbm Coke + Heat produced due to temperature rise

heat transfer = 5.6 * 74210 + 32.8 * 0.24 *(1830-77)

heat transfer = 429375.61 per 100 lbm of coke

Ans heat transfer = 4293.75 btu / lbm of coke