a) A sample of fuel being used in a boiler is found to contain 40% carbon and 23% ash. The refuse obtained after combustion is analyzed and found to contain 7% carbon & the rest is ash. Compute the percentage of the original carbon in fuel which remains as unburnt in the refuse.
b) During an ESP performance evaluation study, the inlet gas stream to ESP is 2,89,920 Nm3/hr and the dust loading is 5,500 mg/ Nm3. The outlet gas stream from ESP is 3,01,100 Nm3/hr and the dust loading is 110 mg/Nm3. How much fly ash is collected in the system in kg/hr?
CALCULATION:-
a)
Let the quantity of Refuse sample = 100 kg
Amount of unburnt Carbon in Refuse = 7 kg
Amount of Ash in the Refuse = 93 kg
Total ash in the fuel that has come into the Refuse = 23% of fuel
93 kg of Ash corresponds to 23% ash in the fuel
Therefore, quantity of total raw fuel = 93 / 0.23
= 404.35 kg
Quantity of original Carbon in the fuel = 0.40 x 404.35
= 161.74 kg
Quantity of unburnt fuel in Refuse = 7 kg
%age of the original carbon unburnt in the refuse = (7 / 161.74) x 100
= 4.32%
b)
Based on Mass balance,
Inlet gas stream dust = Outlet Gas stream dust + Fly ash
i) Inlet gas stream flow = 289920 NM3/hr
Dust Concentration = 5500 mg/NM3
Inlet dust quantity = 289920 x 5500
-----------
1000000
= 1594.56 kg/hr
ii) Outlet dust quantity = 301100 (NM3/hr) x 110 (mg/NM3) x 1
----------
1000000
= 33.12 kg/hr
iii) Fly Ash = Inlet gas stream dust – Outlet gas stream dust
= 1594.56 – 33.12 = 1561.44 kg/hr
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