Patent ID: 7004089

Claim:
Combined fluidized bed and pulverized coal combustion method for use in the combustion chamber ( 3 ) of a fluidized bed boiler, the method comprising the steps of injecting fluidizing air ( 4 ) into a fluidized bed ( 2 ) situated in the bottom portion of the combustion chamber ( 3 ), feeding fuel from a first set of fuel feed means ( 5 ) into the fluidized bed ( 2 ) and combusting the fuel in the fluidized bed ( 2 ), feeding a mixture of pulverized coal and a carrier gas from a second set of fuel feed means ( 6 ) into the combustion chamber 3 , to above the fluidized bed ( 2 ), into the combustion chamber ( 3 ), to above the fluidized bed ( 2 ) is fed the mixture of the pulverized coal and the carrier gas from the second set of fuel feed means ( 6 ) at a mass flow rate ratio which is higher or at least substantially equal to the upper ignition limit of the mixture, and the mixture of the pulverized coal and the carrier gas fed from the second set of fuel feed means ( 6 ) is diluted at least by the fluidizing air ( 4 ), characterized in that at least a fraction of the fuel fed via the second set of fuel feed means ( 6 ) is combusted above the fluidized bed ( 2 ) at the temperature of 1300 to 1500° C.