| Since micronized mineral particles have the characteristics of light weight,large specific surface area,high surface energy and complex composition,it is more difficult to be separated than large mineral particle in the separation process.Coal slime is solid waste generated from coal preparation plants and is mainly composed of combustible coal particles and inorganic minerals.The inorganic mineral content is generally higher than 30%.It is hard to move the inorganic mineral particles apart due to the sludging effect of micronized clay and the small particle size of coal slime.With the continuous increase of the washing rate of raw coal in China,the coal washing volume reached 2.87 billion tons,which produced 431 million tons of coal slime.The production of coal slime is continuing to increase till now.However,the low efficiency and low capacity of the process of coal slime separation leave massive of coal slime wasted and stacked all around coal preparation plants,which causes serious environmental pollution.Besides,the combustible component in the coal slime could be wasted due to the low efficiency of recovery methods.Therefore,the development of high-efficiency separation process of micronized coal slime has important academic significance and industry significance.In this paper,the bituminous coal slime with an average particle size of 10-30?m and ash content higher than 50% is taken as the research object,and the separation process is studied.The main research includes:1)A high-shear pre-mineralization flotation process based on high-shear slurry mixing and column flotation process was proposed.The process uses strong shearing equipment to efficiently transfer energy to the micronized particles in the slurry,so that it is fully mixed with the reagents and bubbles under strong shear conditions.After mineralization,it enters the flotation column for separation.According to the new process flow,the test platform was built,and a 60 mm flotation column device with a capacity of 4-18kg/h was established to study the pre-mineralization-flotation process.The 200 mm flotation column unit with a capacity of 40-140kg/h was established for scale-up verification.The scale-up test of the 200 mm flotation column shows that the ash content of the overflow can be reduced from 51.03% to 8.29% and the ash content of tailing is 71.55% under the conditions of feed strength of 1.33mm/s and spray water strength of 0.8mm/s.The combustibles recovery is 60.75%.2)In this paper,the pre-mineralization-column flotation process intensification study shows that the clean coal product grade and the combustible recovery show a contradiction.Through single-column flotation,the clean coal ash is as low as 9.3%,and the combustible recovery rate is up to 74%.According to the separation behavior of Jinda slime in pre-mineralization-flotation process,a three-column separation process based on pre-mineralization was proposed.The open circuit test results show that the combustible recovery can be increased by about 11% through the threecolumn process when the ash content of the clean coal product is about 9.5%.3)In this paper,MLA(Mineral Liberation Analysis)and scanning electron microscopy are used to analyze the mineral composition and inlay relationship of Jinda coal slime and its sorted clean coal.The results show that the minerals in Jinda coal slime are mainly kaolinite,quartz,illite and calcite,and the kaolinite content accounts for 66% of the total ash content.In Jinda clean coal,the removal rate of the four inorganic minerals is above 80%,and the liberation degree decreases,indicating that the fine coal pollution caused by entrainment is well controlled.In addition,the cleaning effect of strong shear on the surface of the particles was found by electron microscopy images.This effect is beneficial to remove the fine mud cover,enhance the contact between the flotation agent and the combustible components in the slime,and enhance the flotation effect. |
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