Understand the residence time of coal in different bed gasifiers.
Due to the different particle sizes of coal used for gasification and the different reaction temperatures in the furnace layers, the residence time of coal in pressurized moving bed coal gasifiers, fluidized bed gasifiers and entrained bed gasifiers is different. The residence time of coal in the three bed-type gasifiers is as follows:
Pressurized moving bed: 90 minutes; fluidized bed: 15 minutes; air flow bed: 1 second.
In a pressurized moving bed, coal is gasified in a countercurrent manner with the gasification agent from bottom to top. The coal goes through various processes such as drying, carbonization, oxidation, and reduction to slag from top to bottom in the hearth. Since the heating surface of the lump fuel is small, it takes a long time to complete the above processes. If the gasification intensity of the furnace is low during operation, the material layer moves slowly, and some take 4 or 5 hours.
In order to achieve a high carbon conversion rate in the fluidized bed, the coal is gasified in a fluidized state, the coal particle size is small, and the gas-solid contact surface is large during the reaction, so it takes about 15 minutes.
In the air-flow bed, because the coal particles are small, the contact surface between the coal and the gasification agent is relatively large. It can complete the entire gasification process of drying, carbonization, oxidation, reduction and other gasification processes in the same area in a short time. It can be gasified into ash in 1 second or less than 1 second. In the gas phase, the gasification agent reacts with the coal to generate gas.
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