By taking an industrial scale circulating fluidized bed(CFB) boiler with coal slime fed from the top as the test object

the in-furnace flow

heat transfer

combustion and SO_2 emission instabilities were investigated. The mechanism causing thermal explosion of the industrial coal slime and its effects on combustion and SO_2 emission instabilities were explored. The experimental results indicated that

the top feeding CFB boiler features a "C" type(higher in both top and bottom and lower in the middle) temperature profile. In furnace

the coal slime undergone three stages: non-constant speed drying

constant speed drying and combustion. The fluctuation in SO_2 emission mass concentration was confirmed to be primarily caused by the thermal steam explosion

which further led to an uncontrollable and variable combustion occurring alternatively in the upper dilute and lower dense bed regions. On this basis

the approaches to eliminate or reduce the combustion and SO_2 emission instabilities were proposed

which include controlling coal lump size

changing feeding location

and increasing the effective desulfurizing sorbent inventory in the boiler.