COMBUSTION
EXAMPLES
1. The coal with a higher heating value of 4,750 kCal/kg is burned in a
pulverized coal fired boiler with 30% excess air at the rate of 22.56 metric
tons per hour when steam generated is 20 metric tons per hour. This boiler
served by two forced draft fans of equal capacity delivering the air at 300
mm water in furnace. Calculate the following:
a. Capacity of each fan. If fan capacity is to be 110% maximum requirement.
Ambient air is 14.7 psia and 86F.
b. BHp of each fan if fan efficiency is 55%.
2. A bituminous coal has the following composition: C = 71.5%, H = 5%, O = 7%,
N = 1.3%, S = 3.6%, Ash = 8.2%, Moist = 3.4%. Determine the following:
a. Theoretical air-fuel ratio.
b. Theoretical weight of oxygen
c. The actual air-fuel ratio with 27% excess air.
d. The capacity of fan where 5 metric tons of coal burned per hour delivering
the air at 4 kPa in the furnace.
Note: the ambient air is in STP.
3. A furnace burns natural gas with a volumetric analysis as follows: Methane =
80%, Ethane = 13% , Propane = 7%. The gas flow rate is 0.37 m^3/sec and 25%
and 1 atm pressure is supplied to the furnace by a forced draft fan through a
short duct of 0.25 m^2 in area against a static pressure of 50 mm of H2O. The
force draft fan has a efficiency of 65%. Find the:
a. The molal air-fuel ratio
b. The volume flow rate of the flue gas
c. The power output of the fan motor in kW.