The technological flow (bituminous): Pre-purifying gas produced by gasifier, whose temperature is 500~600c, gets into double-standpipe to be cooled and washed dust by hot circulating water, part of dust discharges with the hot circulating water from the bottom water seal of double-standpipe. The gas temperature cooled by double-standpipe is about 80~90c. Firstly, gas enters into electrical detarrer to remove dust and tar through insulating water seal, the gas temperature is lowered to about 70c. Then gas gets into washing tower for cooling and removing dust again, the temperature becomes to 30~45c, secondly, the gas is detared and removed dust by elelctric light oil arrestor through insulating water seal. Finally, the gas is pressured by gas pressure adder and removed water by trap water, then the gas send to the user.