The air from the primary air fan enters the furnace hearth in two ways: firstly, the hot air heated by the primary air preheater enters into the water -cooled air chamber at the bottom of the furnace hearth from both sides of the wall to fluidize the bed materials through the air caps on the air distributor and to form two-phase flow of gas- solid upward through the furnace hearth. Secondly, the hot air is used for boiler-front pneumatic coal spreading after it pressurizes the coal booster fan.
The air supply  from the secondary air fan is also divided into two ways: in the first way the secondary air heated by the air preheater directly goes into the furnace hearth in two layers through the secondary air boxes at front and back wall under the furnace; in the second way, part of cold secondary air not  preheated serves as the air for sealing the belt conveyer of coal supply.
The flue gas leaves the furnace with the solid particles it carries and goes into the cyclone separator through the separator inlet flue on the backwall of water cooling wall, most material particles are separated from the flue gas flow in the separator. The other part of the flue gas flow is led out to tail-end shaft flue from the central cylinder of the cyclone separator via the separator outlet flue and goes into the front and the back flue and flow downward through the smokestack at the upper part of the front enclosure wall and the middle enclosure wall to wash the nest of tubes of horizontal advection heating surface arranged inside the flue and passes the heat to the heating surface and then the flue gas flow enters the filter again through the tubular air preheater and eventually it is drawn into the chimney by induced draft fan and goes into the atmosphere.