Coal Gasifier is a production equipment that converts coal into combustible gas - coal gas (mainly composed of CO, H2, CH4, etc.). According to different gas production processes and the quality of the produced coal gas, gasifiers are divided into single-stage coal gasifiers, double-stage coal gasifiers and dry distillation coal gasifiers. It consists of a mechanical feeding system, a coal gas generation system, a steam generation system, and a slag breaking and unloading system. It has a simple structure, strong safety, and convenient operation. The coal gas produced is mixed semi-water gas with high calorific value. It is integrated with various industrial kilns and furnaces to make full use of the waste heat of coal gas and save energy and reduce consumption.
Gasifiers are divided into single-stage gasifiers, double-stage gasifiers and dry distillation gasifiers according to different gas production processes and the quality of the gas produced.
The product of the single-stage gasifier belongs to a thermal processing process of solid fuel (coal or coke) through gas, that is, oxygen or oxygen compounds (steam, carbon dioxide) pass through a high-temperature solid fuel (coal, coke) layer, and the organic matter (air, water vapor) that plays an oxidizing role is called a gasifier, and the mixed gas containing hydrogen, carbon monoxide and methane is called coal gas.
Furnace structure: full water jacket structure, self-produced steam pressure is 294KPa, which can be directly introduced into the gasifier for use as a gasifier.
Coal feeding mechanism: mechanical coal feeding structure is adopted, which is simple to operate, easy to maintain and has good air tightness.
Ash cleaning mechanism: hydraulic transmission device is used for wet single-side ash removal. The furnace is evenly charged, slag removed and air distributed, easy to operate, easy to adjust and reliable in operation.
Atmospheric pressure fixed bed gasifier generally uses lump anthracite or bituminous coal and coke as raw materials, steam or a mixture of steam and air as gasification agent, and produces gasified gas with carbon monoxide and hydrogen as the main combustible components. The fuel layer in the gasifier is divided into 1-drying layer 2-pyrolysis layer 3-reduction layer 4-oxidation layer 5-ash layer.
The gas produced by the two-stage gasifier is divided into upper gas and lower gas. The upper gas first passes through the I-stage electric tar collector to remove heavy tar and dust. Its working temperature is between 90-150 degrees Celsius. Before entering the indirect cooler, the gas is cooled to about 35-45 degrees Celsius in the indirect cooler. The lower gas is dedusted by the cyclone dust collector, and the temperature after dedusting is about 450-550 degrees Celsius. Then it enters the waste heat exchanger, where it cools the gas and recovers the sensible heat of the gas, and the gas temperature drops to about 200-230 degrees Celsius; then it enters the air cooler for cooling, and the temperature drops to 35-45 degrees Celsius. The upper and lower gas that have been indirectly cooled enter the secondary electrostatic precipitator for deoiling and dust removal again. The cooled and purified gas is pressurized and transported through the gas pipeline for use.
The top gas that makes up the two-stage furnace accounts for about 40% of the total gas volume. It has a high calorific value (6700kJ/nm3), a low temperature (about 120ºC), and contains a large amount of tar. This tar is a low-temperature dry distillation product with good fluidity. It can be captured by an electrostatic precipitator as a chemical raw material and fuel. In the gasification stage, the hot semi-coke and the vaporizer undergo a series of chemical reactions such as reduction and oxidation to generate gas, which is called gasified gas.
The bottom gas that makes up the two-stage furnace accounts for about 60% of the total gas volume. Its calorific value is relatively low (6400kJ/nm3) and its temperature is relatively high (about 450ºC). Because the coal has sufficient low-temperature retorting time in the retorting section, the coal entering the gasification section has become semi-coke, so the generated gasified gas does not contain tar. Because it is close to the ash layer of the grate, it contains a small amount of fly ash. The bottom gas can be treated by cyclone dust collectors and air coolers. In this way, users who use cold purified gas can use cold purified gas without using water washing, thus avoiding the defect that a large amount of phenol water cannot be treated.
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