Fluidization characteristics and separation and quality improvement of low-quality fine coal in a magnetically stabilized gas-solid fluidized bed

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.