PURPOSE: To realize good heat and material balances and to minimize the quantity of wastewater by controlling the water content of a solid organic carbonaceous raw material to be brought into direct contact with the pyrolysis gas thereof and thereby controlling the temp. of discharged gas.

CONSTITUTION: A solid organic carbonaceous raw material (e.g. sawdust) is pyrolyzed in a fluidized bed furnace. The formed pyrolysis gas entraining the steam generated from the raw material passes a second raw material tank 2 and reaches a wet type dust collector 9 composed of a pipe 16 fixed by upper and lower fixing parts 15. Along the inner wall of the pipe 16, circulating water 17 fed by pumps 10,11 descends while forming a water film. The collector 9 effectively lowers the temp. of the pyrolysis gas by bringing it into direct contact with cold water, transfers the deposited tar mist into the descending water film and recovers it into a water reservoir. At the same time, the collector 9 cools the circulating water 17 by blowing air from a fan 14 onto a pipe 16. The no. of ascent-descent cycles of the gas and the method of its introduction are arbitrarily decided depending on the nature of the gas and purpose of its use.