Patent ID: 8500959

Claim:
A method for performing pyrolysis in connection with a bubbling fluidized bed boiler comprising a furnace, which contains solid fluidized bed material, said method comprising: maintaining pyrolysis conditions in a pyrolyzer which include pyrolysis temperature, circulating the solid fluidized bed material of the furnace via the pyrolyzer, fluidizing the solid fluidized bed material in the pyrolyzer with fluidizing gas by feeding the fluidizing, gas to the solid fluidized bed material in a flow direction, bringing the pyrolysis temperature required by the pyrolysis conditions at least partly with the solid fluidized bed material of the furnace, feeding the solid fluidized bed material in a flow direction horizontally through the pyrolyzer and supplying the fluidizing gas below the fluidized bed material so that the solid fluidized bed material flows through the pyrolyzer in the flow direction transversely to the flow direction of the fluidizing gas, forming a bubbling fluidized bed of the solid fluidized bed material in the pyrolyzer by means of the fluidizing gas, said bubbling fluidized bed having an upper surface in the pyrolyzer, supplying solid fuel in particle form to the solid fluidized bed material in the pyrolyzer in several sequential points along the flow direction of the solid fluidized bed material to provide a flow of fuel carried with the solid fluidized bed material in the flow direction of the solid fluidized bed material, separating condensible gaseous substances from the solid fuel under the pyrolysis conditions and collecting the condensible gaseous substances with the fluidizing gas above the solid fluidized bed material, directing the condensible gaseous substances separated from the solid fuel from the pyrolyzer to a condenser, and separating the condensible gaseous substances in the condenser in liquid form as so-called pyrolysis oil, and wherein the method further comprises: dividing the pyrolyzer by means of intermediate walls directed downward from a ceiling to an inlet section, a pyrolysis section and an outlet section, forming a gas lock in the pyrolyzer by means of the solid fluidized bed material by feeding the solid fluidized bed material into the pvrolyzer to the inlet region through a feed inlet below the upper surface of the solid fluidized bed material in the inlet section and the pyrolysis section and discharging the solid fluidized bed material from the pyrolyzer in the outlet section through a discharge outlet located higher than the feed inlet and higher than the upper surface of the solid fluidized bed material in the inlet section and the pyrolysis section, the method further comprising: supplying fluidizing gas at a fluidizing rate to the solid fluidized bed material in the outlet section comprising the discharge outlet, and adjusting flow-through of the solid fluidized bed material through the pyrolyzer by the fluidizing in the outlet section.