The causes resulting in outfire of many times during period of trial operation for W-shaped flame boiler of 600 MW unit in one power plant have been analysed

it is believed that the main causes are as follows:the coal quality being seriously deviated from designed values

and abnormal operation of the coal pulverizing system.For these

many measures

such as taking load on the basis of coal quality condition

optimizing operation of the coal pulverizing system

offering functions of lockout and self-putting into operation to the oil gun etc.

have been put forward.After implementation

under condition of larger deviation of coal quality

outfire failure has never occurred again in long-term operation of the boiler

and combustion being stable.