Numerical Simulation And Improvement Of The Axial Classifier

The classifier as the major equipment of the intermediate storehouse type coal powder preparation system in the power plant, its structural design and working performance have great influence on the performances of the total power plant, such as the life-span of coal mill, the consumed electric power, and the burning of the coal powder in the boiler furnace, etc. Therefore, the quality of the classifier directly affects the security and economy of the power plant operation. An ideal classifier should have two unique characteristics as follows: on the one hand, the acceptable fine coal powder can be exported fully with the air flow; on the other hand, the over-sized coal powder can be returned fully to the coal mill to mill again. In the condition of the over-signed coal powder is not allowed to supply into the boiler furnace with the acceptable fine coal powder, the burning efficiency and stability in the furnace will be assured.A mathematical model for the gas-solid two phase flow in axial classifier is developed in this paper. The standard k -εturbulent model and SIMPLE model for gas phase and the Discrete Phase Model(DPM)for particle motion are used to describe the two phase flow.Through simulating and analyzing the original mold, found that the inner space's air at bottom of baffle has a higher velocity, the separating effect by primary gravity is poor. So the paper provides some means to improve the original mold, and numerical simulation is done on improved ones. From the simulation results we can know that because increased the effective separation space, the air of the inner space at the bottom of the baffle has a lower velocity than before, the separating effect is better than the original mold for the primary gravity separation is improved, the barrel's wear degree is reduced, and the flow resistance of air current at the inner separator is also decreased.