About the pyrolysis process of coal

2024-09-29

Coal pyrolysis, also known as coal distillation, refers to a complex process of a series of physical and chemical changes that occur when coal is continuously heated to a high temperature under air isolation or inert atmosphere. As a result, products such as gas (coal gas), liquid (tar), and solid (semi-coke or coke) are generated.

Coal pyrolysis can be generally divided into three stages

The first stage (room temperature to 300°C) is the drying and desorption stage from room temperature to 300°C. The appearance of coal does not change much in this stage. Before 120°C, it is dehydration and drying. 120-200°C is the release of gases adsorbed in the pores, such as CH4, CO2, N2, etc., which is the degassing process.

The second stage (300-550 or 600°C) is mainly depolymerization and decomposition reactions. Coal forms a colloid and solidifies into semi-coke. Coal begins to soften at around 300°C, decomposes strongly, and precipitates coal gas and tar. The amount of tar in coal is the largest around 450°C, and the amount of gas precipitation is the largest at 450-600°C. In addition to pyrolysis water, carbon monoxide and carbon dioxide, the main components of coal gas are CH4 and unsaturated gaseous hydrocarbons. In this stage, due to the production of colloids with coexistence of gas, liquid and solid phases (especially medium metamorphic bituminous coal), the process of melting, flowing and expanding to resolidification occurs.

The third stage (600-1000℃) is mainly based on polycondensation reaction. This is the stage where semi-coke turns into coke, which is mainly based on polycondensation reaction. The amount of tar is very small. At 550-750℃, semi-coke decomposes and precipitates a large amount of gas, mainly hydrogen, and a small amount of CH4, which becomes secondary analysis. The amount of hydrogen is the largest at 700℃. Basically no tar is produced in this stage. At 750-1000℃, semi-coke further decomposes and continues to precipitate a small amount of gas (mainly hydrogen). At the same time, the residue further condenses and semi-coke turns into coke.

The differences in various types of coal will also lead to different pyrolysis products. It is necessary to determine the production plan through more specific research. If you have any equipment needs, please feel free to contact us. Zhengzhou Dingli New Energy Equipment Co., Ltd. will serve you wholeheartedly!

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