细粒煤在普通气固流化床中无法实现有效分选，为强化细粒煤按密度分层离析趋势，将外加磁场引入气固分选流化床形成磁稳定分选流化床，采用0.074~0.045 mm粒级的磁铁矿粉作为加重质，通过对流化床内床层磁场分布及轴向压力梯度的测量，研究了磁稳定分选流化床内的磁场分布特征及床层流化特性，并利用磁稳定分选流化床对细粒煤进行了分选试验。试验结果表明，在磁稳定分选流化床内，线圈中心位置磁场呈圆柱状均匀分布，且随着线圈间距的增加，磁场强度与磁场梯度逐渐减小，且床层磁场强度与线圈外加电压呈线性关系。磁稳定分选流化床的压力波动幅度随着气速与磁场强度的增加，均呈现先降后升的趋势，并在流化气速v=19.2 cm/s，磁场强度H=9 200 A/m时达到最低，此时床层压力波动最小，流化效果最稳定。随着磁场强度的增加，床层膨胀率减小，起始鼓泡流化气速及颗粒带出气速增大，床层密度增大但适合煤炭分选的调控范围减小，床层表面弧度增大;随着气速的增加，床层稳定性逐渐提升。此外，由分选试验结果表明，在一定范围内，磁稳定流化床的分选效果随着磁场强度的增高而增高，在磁场强度为9 200 A/m，流化气速v=15.4 cm/s 条件下，磁稳定分选流化床对细粒煤具有最佳分选效果，其两段分选的可能性偏差E分别为 0.136 g/cm³和0.156 g/cm³。

Low-quality fine-grained coal cannot be effectively separated in ordinary gas-solid fluidized beds.In order to strengthen the tendency of low-quality fine-grained coals to be separated according to density,an external magnetic field is applied to the gas-solid separation fluidized bed to form a magnetically stable separation.In the fluidized bed,the electromagnetic ore powder with a particle size of 0.074-0.045 mm is used as the weighting material.The magnetic field distribution in the magnetically stable separation fluidized bed and the bed fluidization characteristics are studied by measuring the magnetic field distribution and axial pressure gradient in the fluidized bed.The magnetically stabilized separation fluidized bed is used to carry out a sorting test of low-quality fine-grained coal.The test results show that in the magnetically stabilized separation fluidized bed,the magnetic field at the center of the coil is uniformly distributed in a cylindrical shape,and with the increase of the coil spacing,the magnetic field intensity and magnetic field gradient gradually decrease,and the magnetic field intensity of the bed layer and the applied voltage of the coil show a linear relationship.With the increase of gas velocity and magnetic field intensity,the pressure fluctuation range of the magnetically stabilized separation fluidized bed shows a trend of first decreasing and then increasing,and reaches the lowest when v=19.2 cm/s and H=9 200 A/m.When the bed pressure fluctuates the least,the fluidization effect is the most stable.With the increase of the magnetic field intensity,the bed expansion rate decreases,the initial bubbling fluidization gas velocity and the particle carrying out gas velocity increase,the bed density increases,but the adjustment range suitable for coal sorting decreases,and the radian of bed surface increases.As the gas velocity increases,the bed stability gradually improves.In addition,the sorting test results show that within a certain range,the sorting effect of the magnetically stabilized fluidized bed increases with the increase of the magnetic field intensity.When the magnetic field intensity is 9 200 A/m,the fluidizing gas velocity v=15.4 cm/s,the magnetically stabilized separation fluidized bed has the best separation effect on low-quality fine-grained coal,and the two-stage separation accuracy E values are 0.136 g/cm³ and 0.156 g/cm³ respectively.

1 试验系统与材料

   1.1 试验系统

   1.2 试验材料

2 试验结果与分析

   2.1 磁稳定流化床磁场分布特性

   2.2 磁稳定分选流化床流化特性

   2.3 磁稳定分选流化床表观黏度

   2.4 磁稳定分选流化床分选试验

3 结论