Study on fluidization and separation characteristics of dry heavy medium fluidized bed under different gas distributors

As an important method in the field of fine-grained coal dry separation, the stability of bed density of gas-solid fluidized bed is a key factor to achieve stable separation. The gas distributor characteristics of gas-solid fluidized bed have direct influence on the uniform distribution of airflow and the critical fluidization characteristics of the bed. A systematic investigation was conducted to evaluate the effects of the pressure drop and the arrangement of the gas distributor on the fluidization characteristics of the fluidized bed. The changing rules of critical fluidization characteristics, density stability and separation characteristics of the bed under different gas distributor are compared. Under the influence of different factors on the pressure drop of the gas distributor, a deep exploration of the change rule of critical fluidization gas velocity and bed density stability was carried out. The results show that with the gradual increase of gas distributor pressure drop, the critical fluidization gas velocity and bed density stability increase at the same time, while the bed expansion rate increases and then decreases. The increase in the number of filter cloth layers leads to an increase in the pressure drop across the gas distributor. By the effect of filter cloth dispersion, the energy of the gas flow into the bed is lower, the bubble size is reduced, the bubble distribution is more uniform, and the chance of merger is reduced, thus the bed stability is strengthened. Under the condition of 3#, the expansion rate is 19.3%, and the appropriate gas distributor arrangement can make the airflow dispersed uniformly and improve the bed stability. At the airflow velocity of 0.15 m/s, the standard deviation of bed density fluctuation was 0.049 kg/cm3 under the condition of 3 layers of filter cloth (3#3) above the distribution plate. Similarly, under the condition of 3#3, the ash content of the clean coal product was 13.47% from 6～13 mm coal separation, and the possibility deviation of E value was 0.087 g/cm3.