Fluidized bed combustor

Claim 1

A fluidised bed combustor comprising: a chamber containing a bed of fluidisible material, the chamber comprising an upper portion in thermal contact with a heat exchanger connected to an external load, and a lower portion having a lining for retarding heat transfer fron the bed to the heat exchanger, the lined lower portion having a volume capable of containing the greater part of the fluidisible bed material when the bed is slumped; and means for terminating and resuming fuel flow and fluidising gas flow to the bed, the terminating and resuming means terminating fuel flow and fluidising gas flow to the bed when a pre-determined bed temperature or a pre-determined load temperature is attained, and resuming fuel flow and fluidising gas flow to the bed when one or both of the temperatures falls below its said predetermined temperature; said means for terminating and resuming fuel flow and fluidising gas flow being at least one thermostat with ancillary control circuitry for opening and closing the fuel and fluidising gas flows; said at least one thermostat further including a load thermostat which is connected to the heat exchanger, and which terminates fuel flow and fluidising gas flow when the pre-determined load temperature is attained and which resumes fuel flow and fluidising gas flow when the load temperature falls below said pre-determined temperature, and where the bed thermostat in the lower portion of the chamber overrides the load thermostat if at the time the fuel and fluidising gas flows are due to be switching on by the load thermostat, the temperature of the bed material is below a desired pre-determined start-up bed temperature.