燃煤锅炉炉膛自清渣机理

SELFCLEARING OF SLAG IN FURNACE FOR THE COALFIRED BOILERS

燃煤锅炉运行中 ,灰熔点、渣层重力和热应力都能起到抑制渣层增厚、自动除渣的作用。研究表明 ,当灰熔点 (流动温度 )小于炉内烟气温度 ,则灰熔点能起到控制渣层不断增厚的作用 ;重力能够引起厚渣大渣自发掉落 ,但易造成锅炉设备损坏 ;锅炉降负荷运行时热应力能使渣块因内应力过大而破裂掉落 ,有助于除去炉膛内小块灰渣和厚渣块的外部渣层 ,在炉膛自清洁中起着主要作用。

In operation of coalfired boilers, the ash fusion point, as well as gravity and thermal stress of the slag layer can act as restraining the slag layer to grow and selfclearing of slag in the furnace. Taking theoretic study and numeric calculation as main methods, the effect of three selfclearing mechanisms of slag, namely ash fusion point, gravity and thermal stress of slag crust, upon droppingoff of slag crust with different size has been studied. In the case of ash fusion point, i.e. fluidity temperature, is lower than the flue gas temperature in the furnace, the ash fusion point can restrain the slag infinitively to grow; and the gravity of slag can make huge and thick slag to dropoff, but this is easy to result in accident of boiler, and being not expected to happen during boiler operation; thermal stress occurred in loadreducing operation of the boiler can break slag layer with thickness from several milimeters to several centimiters, and make the slag layer to dropoff from the walltubes, being helpful to clear the small slag crust and the outer part of big slag crust, playing a main role of selfclearing of slag during safe operation of the boiler.