Non condensable gas refers to the vacuum anaerobic pyrolysis process of medical waste and other organic waste. Before entering the combustion chamber, the non condensable gas needs to be purified by a two-stage water sealed tank, which contains 40% liquid alkali. The water sealed tank not only reduces the impurities of the non condensable gas, but also plays a buffering role. Some gases have a certain calorific value. We purify and cool them through a first stage water seal, and finally return t