Study On Vegetable Oil Collector Enhanced Low-rank Coal Flotation

China has abundant low-rank coal reserves,but because of its low metamorphism and abundant oxygen-containing functional groups on the surface,the hydrophobicity of low-rank coal is poor.Conventional hydrocarbon collectors are difficult to adsorb to the surface of low-rank coal,and the cost of flotation is high.With the improvement of mechanization level of coal mining and coal preparation,the output of fine coal slime is increasing,and the requirement of environmental protection and energy utilization efficiency is becoming higher and higher.Therefore,it is urgent to promote the industrial production of low-rank coal flotation,and the development of high-efficiency flotation collector suitable for low-rank coal is one of the more feasible ways.The results show that vegetable oil contains a large number of saturated/unsaturated fatty acids and glycerol compounds.These oxygen-containing components can combine with the polar oxygen-containing sites on the surface of low-rank coal to form adsorption,thus improving the surface hydrophobicity of low-rank coal and improving the flotation effect.Based on the characteristics of low-rank coal,flotation intensification test of low-rank coal,composition analysis of collectors,and mechanism of action between collectors and low-rank coal,this paper selected low-rank coal from Shendong Coal Preparation Plant of Shenhua as experimental sample and four kinds of vegetable oils as collectors to systematically study the mechanism of vegetable oil collectors for strengthening low-rank coal flotation.The main conclusions are as follows:The characteristics and surface properties of low rank coal were studied.The low rank coal has a low ash content of 12.26% and a high volatile content of 34.29%,showing it has high separation value.The low rank coal is mainly of low density and intermediate density,with the content of 49.36% and 39.93% respectively.The low rank coal has rough surface and large pores,and many fine mineral particles adhere to the surface of coal particles.The minerals in the slime are mainly kaolinite and quartz.Oxygen functional groups C-O,C=O and O=C-O lead to weak surface hydrophobicity and poor floatability of coal samples.The effect of vegetable oils on flotation behavior of low-rank coal was investigated.Diesel oil has poor flotation effect on this low-rank coal,the highest concentrate yield is only 24.36%,and the ash content of the concentrate is high,and the selectivity to low-rank coal is poor.Olive oil,soybean oil,pine nut oil and peanutoil as collectors can improve the flotation effect of low-rank coal in varying degrees.Peanut oil has the best flotation effect,followed by pine oil and soybean oil,and olive oil has poor flotation effect.The flotation yield of compound reagents of vegetable oil and diesel is higher than that of vegetable oil single agent,and the ash content of clean coal is similar to that of single agent,which indicates that the flotation efficiency of low-rank coal can be obviously improved by the combination of vegetable oil and diesel oil.The functional groups and chemical composition of each collector were tested.Vegetable oil contains more oxygen-containing functional groups,while diesel oil contains almost no oxygen-containing functional groups.Vegetable oil contains more oxygen-containing polar substances(acids,esters,alcohols,etc.),while diesel oil mainly contains non-polar substances such as alkanes and aromatics.Peanut oil contains the most polar components,followed by soybean oil,pine oil and olive oil have less polar components.The content difference of polar components is an important reason for the difference of flotation behavior of low rank coal,and the more polar components,the better flotation effect.The flotation strengthening mechanism of vegetable oil and its compound reagents for low-rank coal was studied.In the flotation process,polar substances in vegetable oil can adsorb directionally with low-rank coal polar parts under the action of hydrogen bond,which makes the polar parts of coal surface hydrophobic,increasing the contact angle of low-rank coal,shortening the induction time,and makes the collector easier to spread on low-rank coal surface.When vegetable oil is mixed with diesel oil,the two collectors act on the polar and non-polar sites of low-rank coal respectively,making the surface polar and non-polar sites hydrophobic at the same time,increasing the hydrophobic area and improving the floatability of low-rank coal.