Effects Of Grinding Process With Collector In Long Flame Coal Flotation

The low rank coal resources account for 30% of the total coal reserves in China,while the long flame coal accounts for about 53% of the low rank coal reserves.Long flame coal is mainly used for power plant fuel and raw materials in gasification plant.Long flame coal will produce serious pollution to the environment,if it not be processed reasonably and effectively.Coarse coal slimes in the coal preparation plant occupies a large proportion,at the same time,a large number of coarse coal gangue in contain gangue minerals,which is the reason of high sulfur and high ash in coarse coal slimes.This paper investigate the method that flotation combine grinding process to promote combustible recovery: grinding process can release more low ash coal by the liberation between coal and gangue minerals,reduce the slimes size coal to cater requirements of flotation test;at the same time grinding can promote the adsorption of collectors on slimes the surface,improve the utilization efficiency of collector.This paper studied the grinding and dissociation,flotation with collector and grinding with collector were carried out,and utilizing IR,XPS,SEM-EDS,contact angle measurement and laser particle size analyzer to test coal samples.The main research process and conclusions are as follows:(1)Analyzing the long flame coal characteristics used sieve and X-ray diffraction,XPS,infrared spectroscopy and scanning electron microscope equipment: coal gangue mineral is fragile;samples contains a large amount of-0.5mm fine slimes and large amount of middle and the high density coal,which is not suitable to the traditional separation ways of coarse slimes;the mineral mainly consists of quartz and kaolinite;surface oxygen functional groups of coal samples contain more carbon,which contains a large number of groups C-O,C=O,COOH groups,the total content of carbon groups accounted for 36%;coal has many ravines and rough surface with many pores,which further strengthen the adsorption of hydrophilic substances such as mineral particles.(2)Long flame coal grinding test results show that low ash coal and gangue minerals were liberated more with the increase of grinding time.The ash content of 10% is higher than that of the raw coal when the grinding time reaches 12 min,and the yield of that is higher than that of the raw coal by the time,and the grain size of-0.045 mm reaches to 73% after the grinding time reaches 12 min.the grinding time increased to 15 min,-0.045 mm grain yield increased only 4%,the grinding efficiency is low;with the increasing of grinding time,ash content of coarse slimes increased gradually,with the decreasing of particle size,long flame coal is fragile compared with other gangue minerals;low ash coal slimes mainly concentrated in the-0.045 mm fraction,-0.045 mm grain size is the important article size in flotation process.(3)The grinding time and collector dosage of grinding process effect on the flotation were investigated,flotation results show that the increasing of grinding time can boost the combustible recovery and reduce ash content;under the same dosage,the combustible recovery of grinding with collector flotation is about 30% higher than flotation with collector,while the ash content did not change significantly;kinetics of flotation test results show that the maximum combustible recovery of grinding with collector flotation is about 30% higher than flotation with collector in the same collector dosage,and the flotation speed rate significantly faster than flotation with collector,when the collector dosage is 10kg/t,flotation speed rate of grinding with collector was 0.870,that of flotation with collector was 0.696.(4)Flotation samples were analyzed by XPS,laser particle size analyzer,DSA100 and SEM-EDS,contact angle measuring instrument: As XPS results shown,it found that the carbon element content of grinding with collector samples surface is higher than that of the flotation with collector,and the oxygen group content of grinding with collector samples surface is lower than that of the flotation with collector;the SEM results showed that the surface of grinding with collector was more smooth compared with flotation with collector,the EDS results illustrate that the carbon element content of coal sample surface of grinding with collector is higher than that of flotation with collector,while slimes floc were found in grinding with collector coal samples;in the same amount of collector,grinding with collector contact angle were higher than that of flotation with collector about 10o;the result of particle size analysis showed that average particles size of flotation concentrate were decreased with the increasing of the amount of collector,the average particles size of flotation changed obviously compared with grinding with collector;under same collector dosage,average particle size of grinding with collector coal concentrate is lower than of the flotation with collector;as result of coal slurry screening shown that +0.045 mm size particles of the grinding products of grinding with collector gradually increased with the increasing amount of collector dosage.Based on the above analysis: grinding with collector can strengthen the adsorption of collectors on coarse slimes surface,because the collector bridging effect of the oil slurry and shearing force in stirring mill,there are a large number of fine slimes floating floc.Therefore,the flotation speed rate can be increased and the combustible recovery rate can be improved by grinding with collector.