Based on coal quality variation and combustion performance change after retrofit of boiler equipment in one power plant

through numerical calculation and theoritical analysis

the problems existing on the boiler

such as high temperature of exhaust flue gas

large quantity of desuperheating water needed for the superheater and reheater

have been analysed

and the influence of coal quality variation upon combustion performance in the boiler being summarized up.Though the ignition temperature of bituminous pulverized coal and air flow(800 ℃) is about 100 ℃ lower than that of lean coal(900 ℃)

but because of operation parameters' change in the coal-pulverizing system and the burners' system

the initial temperature of bituminou coal and primary air flow(75 ℃) is more lower than that of lean coal(160 ℃)

and the flow rate of promary air increases by a big margin(from 113 t/h to 231 t/h)

the heat quantity needed for igition of bituminous coal is about 30% greater than that for lean coal

thereby

making the combustion in the furnace to be postponed

and the flame centre to shift upward

the quantity of desuperheating water needed for superheated steam to be increased.At the same time

the result of thermodynamic calculation in furnace after reducing elevation of burners by 200 mm and 500 mm

and the result of thermodynamic calculation for the entire unit after increasing the row of tubes for economizer have been given.