Optimization of Combustion in Pulverised Coal fired Boiler

Abstract

The demand of electricity is increasing nowadays and has raised the necessity of improved power generation technologies, especially in developing countries like India. Reduction of emissions of greenhouse gases is the need of hour and it could be achieved considerably by improving the efficiency of existing coal fired plants. Operation of non-optimized boiler can lead to reduced boiler efficiency, increased excess air requirements, delayed combustion, increased heat rate, high CO and NOx emissions and many other. Optimization of combustion in pulverised coal fired boiler is very important today for every thermal power plant. The objective of this work is to optimize the combustion in pulverised coal fired boiler in order to improve the boiler efficiency and thereby to reduce the heat losses occurring in boiler such as dry flue gas loss etc. The combustion in pulverised coal fired boiler is affected by quality of coal, pulverised coal fineness, burner tilting angle, air fuel ratio, slagging and NOx formation. Clean air and dirty air test for bowl mill to balance coal supply at four corners of boiler furnace of unit 5 have been carried out. Then, optimization of combustion has been carried out with the help of secondary air dampers which resulted into improvement in boiler efficiency from 84.52% to 85.43% and reduction in heat losses from 15.47% to 14.56%. Also, optimum positions of burner tilting angle based upon economic analysis of reduction in reheat spray have been carried out. At last, the exergy analysis of combustion process has been carried out which resulted into rational efficiency of boiler as 40.5% and combustion efficiency as 86.3%.