What is fludized coal?

Answer 1

In a fluidized bed power plant, coal is crushed (rather than pulverized) to a small particle size and injected into
a combustor, where combustion takes place in a strongly agitated bed of fine fluidized solid particles. The term
“fluidized bed’’ refers to the fact that coal (and typically a sorbent for sulfur capture) is held in suspension
(fluidized) by an upward flow of primary air blown into the bottom of the furnace through nozzles and strongly
agitated and mixed by secondary air injected through numerous ports on the furnace walls.

For more info see this National Coal Council report " Coal: America’s Energy Future - A Technology Overview"

Answer 2

It is coal that has been pulverised then loaded into the furnace to form a bed. Air is then introduced at the bottom and when sufficient pressure is applied the coal bed actually increases in height and displays the properties of a fluid: ie if there is a temperature differential across the height it will display convection currents, and a less dense substance will float on it.

Answer 3

coal is basically a solid material but is susceptible to catch fire. So in many a giant boilers, it is stored in smaller sized lumps. Before charging in boiler, it is crushed & fed into the boiler along with air with a force. It is similar to pneumatic conveying. The high velocity air takes with it the coal & hnece the name fluidized coal.