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The classification and working principle of gas producer


I. Classification and Principle of Gas producer
Gas producers can be classified into two categories, namely, single-stage ones and two-stage ones; the former can be sub-classified into hot ones and cool ones.
II. Operating principle
The qualified feed coal is transmitted by electric hoist into the main storage barn and sent into the furnace by the double-drum hydraulic stoker. The coal is distilled and heated by the gas from the gasification stage, from which the gas in the semi-coke state reacts with the gasifying agent, air and vapour. The gas in this stage consists of two parts: the first part leaves the two-stage gas producer with the help of the cyclone dust collector through the gas exit of the lower stage of the furnace and the second part leaves the furnace through the gas exit after rising through the central pipe to mix with the distilled gas. The gas from the lower-stage exit enters the forced air cooling device after dedusted and cooled by the cyclone dust collector for further dedusting and cooling before going into the middle cooler. The gas from the upper-stage exit enters the electric tar collector to decoke before entering directly into the middle cooler to mix with the gas from the lower stage, through which process the cooling is down, Then the mixed gas will enter the electric light oil collector to collect light oil. After forced by the booster fan and dehydrated by the vapor collector, it is sent to the final users. The two-stage gas producer consists of two stages, dry distillation stage on the top and gasifying stage at the bottom. Coal travels from the double coal feeding valve on the top into the furnace. After complete dehydration and long-time low-temperature distillation in the carbonization stage, the gas gradually becomes semi-coke before entering the gasifying stage, where the hot semi-coke reacts fully with the gasifying agent blown into the furnace from the bottom. Then it goes through the reduction zone and oxidation zone to form cinder which is automatically removed out by the grate drive. During the low-temperature dry-distillation process, the gas generated therefrom, called the distilled gas, is the top gas comprising the two-stage gas producer, accounting for around 40% of the total gas, with relatively high calorie values(6700KJ/nm3) but low temperature(about 120℃) and a lot of tar. This kind of tar is the product of low-temperature distillation, with good fluidness, which can be collected by the cottrell precipitator as chemo-industrial raw materials or fuels. During the gasifying stage, the hot semi-coke and carburetor forms the gas after a series of chemical reaction of reduction and oxidation. It is the gasified gas. The bottom gas of the two-stage gas producer accounts for 60% of the total gas, low in calorie value(6400KJ/nm3) but high in temperature(about 450℃). As the coal has enough time for low-temperature distillation in the distillation stage, it becomes semi-coke when entering the gasifying stage. Therefore, the gas does not contain tar. As it is close to the grate bars, it contains little flying ash. The bottom gas can be treated by the cyclone dust extractor and wind-cooler. In this way, users of the cooled purified gas can use the it without water-wash method hence avoid the failure to treat the large amount of carbolisata aqua. The two-stage gas producer has an upper and a low gas outlets that can export gases of different thermal values; its gasification efficiency and comprehensive thermal efficiency are all higher than single-stage ones; coal is completely carbonized in the upper stage of furnace; gas in the lower stage hardly contains tar and that in the upper stage contains a small amount of light tar which makes it difficult to clog the pipeline. With high thermal value and stability, the two-stage gas producer has higher operating flexibility and degree of automation as well as lower labor intensity. With significant water saving result and a small floor space, the two-stage gas producer does not pollute the environment and can be low-costing in long-term operation. The furnace grate rotation and coal adding part of the furnace type can adopt machine or hydraulic pressure based on different requirements of users. The furnace grate is heat-resisting iron with better gas permeability and applicable for bituminous coal gasification technology; the common specifications used by two-stage gas producer include Φ2.0M,Φ2.6M,Φ3.0M,Φ3.2M,Φ3.4M,Φ3.6M,Φ3.8MΦand 4.0M. 1. Gas at the bottom can be extracted through 36 refractory channels; there are 6 gas control valves at the bottom to reach balanced combustion of the whole furnace surface. (The different refractory channels of a furnace type will also increase correspondingly.) 2. There is another central pipe established for collecting the bottom gas. Its function includes: a, constitute the dry distillation space with the surrounding 36 fire-resistance channels and forms that inner and outer double-tier circular radiant heat source. b, it constitutes the combustion balance system of the cross-stage furnace chamber together with the 36 fire-resistance channels. This can avoid the central black hole of the combustion in the two-stage oven and facilitate the combustion regulation of the furnace. 3. Such techniques as the high ash basin water sealing and high evaporation pressure are used to improve the gasification and produce more gas. 4. The grate drive dedusting and download of coal is completed by the hydraulic system and controlled automatically. 5. The water leg is a pressure vessel with a very long service life and it can self-produce steam for the production requirement. The application scope of two-stage gas producer includes steel rolling mill furnace, glass tank furnace, shuttle kiln made of refractory materials, steel plate gunpowder, ceramic rolling kiln, chemical reduction kiln and pellet shaft kiln that can be used for supplying fuel as long as the kiln can reach 400℃ to 1500℃