Study On Density Separation Mechanism Of Particles In The Narrow Inclined Channels

The terminal velocity of particles mainly depends on their density and size,which makes it difficult for the particles to be completely separated according to their density in the hydraulic gravity equipment.It is characterized by misleading some low-density coarse particles in the underflow and misleading high-density fine particles in the overflow.In this paper,the motion behavior of different particles in inclined narrow channels is studied.It was found that in the high water gradient environment,the effects of particle size on motion is significantly reduced,resulting in a powerful separation on the basis of density.At the same time,the essence of density separation of particles in inclined narrow channels is illuminated in paper.The research results have important theoretical significance for the reduction of the lower limit of the particle size of the gravity separation and the design and operation of the inclined plate channel structure.Based on the equation of the water velocity profile in the inclined narrow channel and the force balance analysis of the particles in the high gradient water velocity environment,the equilibrium model of the single spherical particle in the inclined narrow channel is established.It is the quantitative relationship between particle size,density,channel spacing,tilt angle,and average liquid velocity in the channel.In the paper,the balance test of single spherical particles at different intervals,the batch-feeding test of coal slurry below 2 mm,and the continuous sorting test were carried out.In the balance test,six spherical glass spheres of different particle sizes were placed in four inclined channels with stable rising water flow.When the particle was balanced,the measured water velocity was compared with the equilibrium model to calculate the water velocity.The results show that the established equilibrium model has a relative deviation between the actual measured water velocity and the model calculated water velocity within 10%(R_e/R_et)<40.The established equilibrium model has strong use value.When(R_e/R_et)>40,the predicted water velocity is greater than the actual water velocity,and the water velocity calculated by the empirical model is more accurate.In the controlled feed test,the 0² mm slime was sorted into eight products at seven water speeds of 0.0192 m/s,0.0353 m/s,etc.,and the cumulative yield and ash of the product were calculated.The results show that the yield-ash curve obtained by the controlled feed test is very similar to the curve of the float-sink test,and the curve of the sieve test is very different,which indicates that the particles are mainly separated according to their density in the inclined narrow channels.The effect of channel spacing,throughput,and split fluidization on sorting were investigated in a continuous experiment.The results show that the channel spacing suitable for particle sorting is 3⁵ times of the maximum particle size.When the channel spacing is increased,the liquid velocity and the lower size of the particle will be increased.The split fluidization method can effectively reduce the loss of coarse density particles in the underflow;the ash content of1.8⁰.2mm coal particles in the overflow product is about 3.65%,that is,when the maximum particle size is 9 times of the minimum particle size,the product ash has little change with the particle size of the particles.It shows that the sorting densities of different particle size grades are the same.The particles are mainly separated according to their density,with the effects of particle size suppressed.In addition,when the throughput is 18.33 t/?m²h?,the inclined narrow channel still has a higher separation efficiency.There are 31 figures,16 tables and 96 references in this paper.