Wow right up my alley. I currently work at a powerplant where we operate 2 CFB,s.
Like ralph had said. The floor of the boiler is lined with many gird nozzled, which are fed from Primary FD air. the air suspends the "bed". With stoker type coal boilers the anthracite coal is pulverized and blown in to the combustor. Well the CFB is alittle different. We burn bituminous soft coal. The coal is fed through a rotary valve type feeder, down a chute then onto the boilers suspended bed. The soft coal is first crushed to walnut sized pieces so they will have lag time in the furnace. The bed is made up of sand. upon start up beach sand is purchased and injected, then when the coal diplaces it it become the Coal- sand- grit bed. Only enough air is used to the grid to keep the bed suspended. it burns at around 1400* to 1600* F and pulverized limestone is added to capture the sulfur in the coal. sorry to be continued duty calls. Doug