Mechanism Of Collector Prepared By Plasma On Low-rank Coal And Its Application

The preparation methods of high-efficiency collectors for low-rank coal are mostly physical mixing,evaporation and condensation,catalytic reaction,etc.The raw materials are mainly fine chemical products,and the preparation conditions are harsh and the cost of raw materials is high.Therefore,it is necessary to develop simple and effective methods for preparation and raw materials.A method of preparing mixed-polar collectors by plasma is presented in this paper.Taking the representative components of hydrocarbon oil as the research object,dodecane was treated by air plasma to prepare collectors containing polar and hydrophilic functional groups.Taking Shendong Bu Ertai coal slime as flotation feed,the collector’s collecting ability was explored.The preparation of plasma was studied by means of infrared spectroscopy,gas chromatography-mass spectrometry,interfacial tension and contact angle.The mechanism of action between collector and low rank coal was studied,and its application in flotation of high rank coal was explored.The flotation test of low-rank coal with collector prepared by plasma was carried out.The collection effect of dodecane on low-rank coal slime is unsatisfactory.When the dosage is 15 kg/t,the concentrate yield and the combustible matter recovery reach the maximum,which was 39.19% and 49.26% respectively.With the increase of plasma preparation time,the ability of reagent to collect low-rank coal is greatly improved,the concentrate yield and the combustible matter recovery sharply increased,and the growth trend is obviously slowed down after more than 9 minutes.At 9 min,the concentrate yield and the combustible matter recovery reached 79.88% and 93.30% respectively.With the increase of collector dosage in plasma preparation for 9 minutes(D-9),the concentrate yield and the combustible matter recovery increased sharply.When the dosage exceeded 7.5 kg/t,the concentrate yield and the combustible matter recovery slowed down and tended to be stable.When the dosage was 7.5 kg/t,concentrate yield and the combustible matter recovery reached 80.14% and 90.17% respectively.Comparing the flotation results of two collectors at the same dosage,the concentrate yield of D-9 increased by 25 percentage points more than that of dodecane.D-9 can effectively improve the floatability of low-rank coal and enhance the flotation effect of low-rank coal.On the basis of flotation test,the group composition of collector D-9 was studied.D-9 contains polar groups such as C-O,-C=O,-OH,which belong to polar substances such as aldehydes,ketones,furanones,olefins and alcohols.The interfacial tension of collector aqueous solution is lower than that of dodecane,and the longer the preparation time,the lower the interfacial tension.This indicates that during plasma treatment,oxygen molecules and oxygen atoms in the air are intensified and react with dodecane.Non-polar groups such as methyl are converted into polar groups such as C-O,-C=O,-OH,polar substances are produced.With the increase of time,the degree of reaction is deepening.The reagent is changed from non-polar hydrocarbon collector to heteropolar collector.The adsorption mechanism of D-9 and low rank coal was studied.Microscopically,the hydrophobic groups vibration peaks of different densities low-rank coal increased after interacted with dodecane,but,the enhancement of hydrophobic group peaks was stronger after interacted with D-9 than that of dodecane,while the vibration peaks of hydrophilic groups became weaker.Macroscopically,the contact angle of different densities low-rank coals increased after interacted with dodecane,while,the enhancement degree was greater with D-9 than that of dodecane.The increase range of low density grade slime is larger than that of high density grade.This indicates that D-9 can increase the number of hydrophobic sites on coal surface and cover the hydrophilic sites of low-rank coal by chemical adsorption,expand the hydrophobic difference between organic matter and gangue minerals,enhance the flotation of low-rank coal.D-9 was used as collector to regrind and reflotat Zhangshuanglou flotation tailings.When the dosage is 7.5 kg/t,the concentrate yield of D-9 increases by about 30 percentage points than that of dodecane,and the combustible matter recovery increases by about 46 percentage points.This shows that the collector prepared by plasma can also be used in high-rank coal flotation.In this study,a method of preparation of collector was developed.The polar functional groups were directly introduced into the non-polar reagent by plasma,and the non-polar reagent was transformed into heteropolar reagent by chemical reaction.The hydrophobicity of coal slime could be effectively improved with the collector,which provided technical support for strengthening the flotation of low-rank coal.There are 39 figures,12 tables and 94 references in this thesis.