Experimental Study On Reverse Flotation Purification Of Kaolin From Comprehensive Coal Gangue In Zhungeer Area

Zhungeer Banner is a key coal producing area in northern China.For a long time,coal gangue has been abandoned as coal seam debris during coal mining,which not only occupies a large amount of farmland,causes environmental pollution and damage,but also causes serious waste of mineral resources.This article takes the comprehensive coal gangue from a representative coal preparation plant in the Zhungeer area of Inner Mongolia as the research object,discusses the feasibility of using flotation methods to recover low-quality coal and purify kaolin from the comprehensive coal gangue,as well as the impact of weathering（freeze-thaw,low-temperature oxidation）caused by the open-air placement of the comprehensive coal gangue on the flotation effect.The main research content and conclusions are as follows:Analyze the mineral composition,chemical composition,and other aspects of the comprehensive coal gangue and hand selected kaolin collected by representative coal preparation plants in the Jungar region.The analysis results indicate that the ash content of the comprehensive coal gangue in the region is relatively close,with data concentrated in 67%-72%.The comprehensive coal gangue collected by the Power Coal Preparation Plant and the Suancigou Coal Preparation Plant were selected for flotation tests.The comprehensive coal gangue concentrate yield of the Power Coal Preparation Plant was 22.85%,and the Suancigou comprehensive coal gangue concentrate yield was 11.67%,indicating that the comprehensive coal gangue in the region contains some low-quality coal.From the chemical analysis results,it can be seen that the raw materials of comprehensive coal gangue collected by four different coal preparation plants in Zhungeer area are mainly composed of Si O2 and Al2O3oxides,with relatively low content of other oxides.The aluminum oxide content of the four kinds of comprehensive coal gangue is high and the impurities are small.The content of impurities Fe₂O₃in the comprehensive coal gangue raw materials collected by Power Coal,Heidaigou,Suancigou and Longwanggou Coal Preparation Plant is1.78%,0%,0.351%and 3.015%.The experiment of flotation recovery of low-quality coal from comprehensive coal gangue was carried out to further explore the influence and mechanism of outdoor natural weathering on the flotation recovery of low-quality coal and purification of kaolin from comprehensive coal gangue.The experimental results of comprehensive coal gangue flotation recovery of low-quality coal show that as the outdoor natural weathering time continues,the ash content of the feed clean coal increases from 20.46%to 31.52%,indicating that outdoor natural weathering will cause the quality of the Suancigou clean coal to deteriorate.The yield of concentrate products decreased from 24.36%to 6.70%,while the yield of tailings products increased from 75.64%to 93.30%,indicating that outdoor natural weathering can lead to a decrease in the floatability of clean coal.The test results of comprehensive gangue flotation impurity removal pyrite show that outdoor natural weathering will not have a significant impact on comprehensive gangue pyrite impurity removal.The test results show that outdoor natural Weathering will not significantly affect the properties of kaolin in comprehensive coal gangue.Further tests such as scanning electron microscopy（SEM）,Zeta potential,and Fourier transform infrared spectroscopy（FTIR）were conducted on the naturally weathered Suancigou clean coal outdoors.The test results indicate that the continuous outdoor natural weathering time will change the microscopic appearance of the coal particle surface;The molecules or dispersed particles of clean coal in water become smaller and smaller,and the system shows a gradually stable trend;The surface hydrophobicity of clean coal decreases and its hydrophilicity increases.Natural weathering will reduce the floatability of coal particles,leading to a decline in the yield of low-quality coal concentrate products recovered from comprehensive gangue.Conduct flotation recovery experiments on low quality coal from comprehensive coal gangue to further explore the impact and mechanism of freeze-thaw oxidation on the flotation recovery of low quality coal from comprehensive coal gangue.The experimental results indicate that as the freeze-thaw oxidation time continues,there is no significant change in the ash content of the Suancigou clean coal.Within 60 days of freeze-thaw oxidation,there is no significant impact on the yield of concentrate and tailings products for comprehensive coal gangue flotation recovery of low-quality coal.Further tests such as scanning electron microscopy（SEM）,Zeta potential,and Fourier transform infrared spectroscopy（FTIR）were conducted on the freeze-thaw oxidized Suancigou clean coal,As freeze-thaw oxidation continues,the microstructure of the coal particle surface remains unchanged;In water,the changes in its molecules or dispersed particles are not significant,and there is no significant change in the stability trend of the system;The surface hydrophobicity of coal has not changed significantly.The freeze-thaw oxidation effect does not change the floatability of clean coal,and does not have a significant impact on the yield of concentrate products from comprehensive coal gangue recovery of low-quality coal.Conduct flotation recovery experiments on low quality coal from comprehensive coal gangue to further explore the impact and mechanism of ultra-low temperature oxidation on the flotation recovery of low quality coal from comprehensive coal gangue.The experimental results show that as the low-temperature oxidation time continues,the ash content of the feed clean coal increases from 20.46%to 26.28%,the yield of concentrate products decreases from 24.36%to 13.66%,and the yield of tailings products increases from 75.64%to 86.34%.This indicates that the continuous low-temperature oxidation time will lead to a decrease in the quality of the Suancigou clean coal and lower the concentrate yield of the simulated comprehensive coal gangue sample recovery of low-quality coal.Further tests such as scanning electron microscopy（SEM）,Zeta potential,and Fourier transform infrared spectroscopy（FTIR）were conducted on the low-temperature oxidized Suancigou clean coal,and it was found that as the low-temperature oxidation continued,the micro morphology of the coal particle surface would be changed;The molecules or dispersed particles of Suancigou clean coal in water become smaller and smaller,and the system shows a gradually stable trend;The surface hydrophobicity of coal decreases.Low temperature oxidation can lead to a decrease in the floatability of coal,resulting in a decrease in the yield of concentrate products for comprehensive coal gangue flotation recovery of low-quality coal.