Research On The Separation Characteristics Of -6mm Fine Coal In A Compound Dry Separator

Coal is the basic energy and high-carbon energy in China.It is the only way to rea lize the high-efficiency and clean utilization of coal resources for national coal energy development strategy in the future.Nowadays,wet processing dominates in the coal pr eparation technology.However,with the aggravation of the water shortage and environ mental pollution and the increase of haze weather,the application of wet coal preparati on technology is limited.Therefore,the current situation highlights the important role a nd status of dry coal beneficiation technology.The compound dry process technology f or +6mm coal has been applied in industry,however,for the increasing fine coal(-6m m),the proven technique is still absent.In this paper,the compound dry separating technology for the first time applied to the separating of fine coal,the formation of fine coal compound dry separator.Improve the sorting effect of the compound dry separator on the fine coal by changing the pore size and vibration energy and the air velocity,Reinforcement of fine coal in the compound dry separating bed by density stratification process,And then realize the compound dry high performance separating of fine coalThe movements of particles in the compound dry separator affect the stratification and separation of fine particles directly.By the tests of the bed density,the contours of bed density distribution were established.The density is mainly affected by vibration amplitude,frequency,air flow and back plate angle.The bed had the lowest density oscillation and the optimal stability and the optimum separation when the vibration amplitude,frequency,air flow and back plate angle were 3.6mm,53 Hz,0.66m/s,45° respectively.The vibration energy has great influences on the fine coal separation by the compound dry cleaner.The vibration energy distribution on the bed during the fine coal separation was tested and the effects of the vibration energy on the materials were determined.The accelerations of the clean coal area,middling area and gangue area in the X direction are 6.5m/s2,5.5m/s2,5 m/s2 respectively and in the Y direction the three areas are 30.5 m/s2,22.5 m/s2 and 15 m/s2.The acceleration of clean coal area in the Z direction is equal to acceleration value of concentrate area in the Y direction.The acceleration of middling area in the Z direction increases by 15.38% compared with the acceleration value of middling in the Y direction.However,the acceleration of gangue area in the Z direction decreases by 50% compared with the acceleration value of gangue area in the Y direction.The above results show that the particles move from the feeding end to the gangue end in a vertical throw movement,which is favorable to particles stratification and separation.Through the analysis of the energy distribution on the bed,the clean coal area obtains the maximum energy and it is the main separation section.Also,low density materials are mainly separated in this section.The middling section obtains less vibration energy and it is the transition section of the concentrate and the gangue.The gangue section obtains the least vibration energy and it is actually used for the transmitting of gangue with minor separation effect.The separation of fine coal by the compound dry cleaning is actually the interaction results among particles and the separation bed body.Through the analysis of the forces on the particles in the X,Y and Z directions,the mathematical models of the forces on the particles in the X,Y and Z directions were established,which can improve the density distribution theory of the particles separation in the compound dry separator.The vibration energy transformation among particles on the bed determines the activity and density stability of the separation bed in the fine coal separation by the compound dry cleaner.The collision forces among particles on the bed were tested,which was used to analyze the energy transformation among particles.The vibration amplitude and frequency have great effects on the forces.The maximum forces on the particles in the clean coal area and gangue area were 21.2mN and 59.6mN respectively.The forces on the middling were extremely uneven and the stratification and separation of the middling had the optimal results.The vibration energy is transferred to the particles on the separation bed,so the activity of the particles is intensified.Then the stratification and separation of the particles on the bed are realized.There exists dissipation during the transformation of the vibration energy.Through the study on the energy transformation during the fine coal separation on the bed,the mathematical model of energy transformation and dissipation of the compound dry cleaning process were established.Based on the above beneficiation theory and tests,the separation of <6mm fine coal was investigated using compound dry cleaner in the laboratory and industrial scale.The evaluation of the effects of air flow and vibration intensity on the stratification of the fine coal on the separation bed was proposed by using ash content segregation intensity.The results are as the following.The probable errors E of the separation for 6-3mm and 3-1mm fine coal in laboratory were 0.145 and 0.14 respectively.The yield,ash content and sulfur content of the clean coal prepared by the beneficiation of 0-6mm fine coal using industrial apparatus were 69.98%,10.28% and 0.41% respectively,with a satisfactory separation.