Question

Coal containing 40% C, 30% H and 30% ash at 1000 kg / h flow is burned with dry air fed at 6 kmol / second. Chimney from the oven
In addition to gas, there is a solid waste, 95% of this waste is all of the ash in coal, back
the rest is unburned carbon. While all the hydrogen in the fuel is oxidized to water;
carbon burns so that the selectivity of carbon dioxide in carbon monoxide is 10.
a. Percentage of excess air used,
b. Calculate what percentage of oxygen increases.

Answer 1

Feed analysis

Component	wt%	Kg/h	M.W(Kg/Kmol)	Kmol/h
C	40	400	12	33.33
H	30	300	1	300
Ash	30	300	-
Total	100	1000

The solid waste is 95% ash and remaining unburned carbon

Ash = 300 Kg

Solid particles = 300/(0.95) =315.789 Kg/h

Unreacted C = 315.789-300= 15.7894 Kg/h

Moles of C unreacted = 15.7894/12 =

1.3157 Kmol/h

The reactions occuring are

Selectivity of CO2: CO = 10:1

Reacted C = 33.33-1.3157 = 32.0143 Kmol/h

Reacted H = 300 Kmol/h

O₂ required according to stiochiometry =

(32.0143) (10/11) (1) + (32.0143×(1/11) ×0.5) +(300×0.25) = 105.559 Kmol/h

Air supplied = 6 kmol/s = 21600 Kmol/h

O2 in air = 21 mol%

O2 supplied = 21600(0.21) = 4536 Kmol/h

% excess O2 = ((4536-105.559) /(105.559)) (100) = 4197.122%

% excess air = % excess O2 = 4197.122%

B)

% increase in O2 = (4536-105.559) /(105.559) (100) = 4197.122%

Please upvote if helpful