Abstract: A method for reducing nitrogen oxide emissions of a bubbling fluidized bed boiler burning biofuel and an air distribution system for a bubbling fluidized bed boiler biofuel. A fluidized bed is arranged in a lower part of a furnace of the boiler. The bed is fluidized by fluidizing gas that includes primary air. Fuel is fed to the fluidized bed, which dries and pyrolizes into pyrolysis gas including volatile matter of the fuel. The gas rises upwards in the furnace and burns. Secondary air is supplied above the fluidized bed from secondary air nozzles, and tertiary air is supplied above the secondary air nozzles. A part of primary air is supplied in connection with fuel feeding such that the fuel is forced substantially on the surface of the fluidized bed, thus pyrolizing entirely, and at least a part of the pyrolysis gases formed in the pyrolysis is burned by primary air such that the air coefficient in relation to the volatile matter of fuel in the pyrolysis gases is in the substoichiometric area.

Abstract: The invention relates to a combined fluidized bed and pulverized coal combustion method and system. In the method, fluidizing air (4) is injected into a fluidized bed (2) situated in the bottom portion of the combustion chamber (3). Into the combustion chamber, to above the fluidized bed (2), is fed a mixture of pulverized coal and a carrier gas from a second set of fuel feed means (6) at a mass flow rate 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 at least by the fluidizing air (4), and at least a fraction of the fuel fed via the second set of fuel feed means (6) is combusted above the fluidized bed (2).

Abstract: The invention relates to a combined fluidized bed and pulverized coal combustion method and system. In the method, fluidizing air (4) is injected into a fluidized bed (2) situated in the bottom portion of the combustion chamber (3). Into the combustion chamber, to above the fluidized bed (2), is fed a mixture of pulverized coal and a carrier gas from a second set of fuel feed means (6) at a mass flow rate 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 at least by the fluidizing air (4), and at least a fraction of the fuel fed via the second set of fuel feed means (6) is combusted above the fluidized bed (2).

Abstract: A method for processing carbonaceous material in a reactor. Carbonaceous material, such as sawdust, plant residues from forestry or agricultural processes, municipal solid waste and refuse derived fuel, is fed into the riser section (10) of a reactor (10-15) in which it is contacted with inorganic particulate material and reactor walls at an elevated temperature essentially in the absence of oxygen in order to convert the carbonaceous material at least mainly into gaseous processed products, whereby a gas phase is obtained, containing fluidization gas and processed products. According to the invention a dense suspension is formed into the riser space (10) of the reactor, containing based on the particle number 7×108 to 3×1011 particles/m3 (about 2×107-1×1010 particles/ft3), and the mass ratio between the particulate matter bringing heat into the reactor and the carbonaceous material is in the range of 1:1 to 10:1.