Abstract: Disclosed is a process for improving the solids distribution in a circulating fluidized bed system. In the invention, hot ash from the system and fresh carbonaceous fuel are mixed in a chamber which is fluidized so as to form a fluidization zone wherein the heavier material is concentrated and a second fluidization zone which consists predominantly of fines at least a portion of which is separated from the heavier material. This zone separation is facilitated in part by maintaining different gas-mass flow rates so as to form a plug of heavier material. At least a portion of the fine material is then transferred into the reactor while the coarse material is further processed.

Abstract: Disclosed is an apparatus and process for an energy producing plant utilizing a circulating fluidized bed system having an integral fluidized bed heat exchanger, the fluidized bed reactor and integral heat exchanger having a common wall with at least one perforation for fluid communication therebetween. In the system, solids are separated from the reactor flue gas, and in dependence upon a process variable, are directed in varying amounts either directly back into the reactor or into the integral heat exchanger, the latter being operated as a classical and/or bubbling bed at a higher pressure than the reactor. A heat exchange medium passes through tube bundles immersed in the exchanger fluid bed and the bed solids and fluidizing gas in the heat exchanger are passed through the perforation to control the reactor operation.