A sample of medium grade bituminous coal on analysis gave the following result: Sulphur
2%, nitrogen 1%, Oxygen 6%, ash 11% and water 3%. The residue of carbon and hydrogen is in
the mole ratio C:H=9:1. Calculate the weight fraction composition of coal with ash and moisture
omitted
Answers
Explanation:
Publisher Summary
This chapter discusses some of the fundamental aspects of lignite combustion, small-scale combustion applications, burning lignites in electric power stations and the attendant ash fouling problem, and an important emerging technology, fluidized bed combustion. Combustion of a lignite particle proceeds in four stages: Removal of surface moisture at low temperatures, evolution of water from organic functional groups or minerals, evolution and combustion of the volatiles, and finally burnout of the char. CO and CO2 production is similar for lignite and its char. These similarities suggest that lignite burns through heterogeneous combustion—that is, without releasing a cloud of volatiles, which ignite first and burn homogeneously, followed by a separate, heterogeneous char burnout step. The flame temperatures in lignite combustion are relatively low; hence, the formation of thermal NOx is also low. Fuel nitrogen is released, initially as HCN, or is retained in char. In a reducing atmosphere HCN will be converted to N2; consequently, a proper staging of the combustion air may allow control of NO formation from this fraction of the fuel nitrogen. As an oxidizing atmosphere is required for char combustion, formation of NO from the fraction of fuel nitrogen initially retained in the char would be very difficult to control.