| Moisture is an important index for coal products.With the development of mining mechanization and the deepening of coal processing and utilization rate,the content of fine coal slime in coal preparation plant is increasing daily.Because of the high water content of fine coal slime,the moisture of clean coal is high,which affects the economic benefits of coal preparation plants.Adding chemical dewatering agents can reduce the moisture of the fine coal filter cake without changing the existing technological process.There are many kinds of dewatering agents,and the effect of filter aid is different.In this paper,various different types of agents are used to investigate the effect of their filter aid on coal slime,and the mechanism of the filter aid is preliminarily analyzed,and an industrial test is carried out on this basis.In this study,two kinds of weakly caking coal(Jinhuagong and Baidong raw coal)and a kind of coking coal(Liuwan floatation coal)were selected as the research object.Through the selection and optimization of filter aid,the effect of different types of filter aid was systematically studied,the suitable type of surfactant was selected,and the mechanism of action was discussed by means of contact angle and surface tension measurement.The dewatering effect of SDBS on Majialiang coal slimes was verified by industrial tests.The effect of esters on three kinds of coal samples is remarkable,in which ethyl oleate has the best filter aid effect.When the dosage is 300-500g/t,the water content of two kinds of weakly caking coal can be reduced by about 5%.When the dosage is 750g/t,the moisture of the cake is reduced by 2.7% for the Liuwan coal sample.Through the test of the contact angle of Baidong coal sample after the action of ethyl oleate,it is considered that the esters agents can effectively reduce the moisture of the filter cake by increasing the surface hydrophobicity of the coal particles.In surfactants,when the anionic AEC-Na is used as a dewatering agent,under the suitable dosage,the moisture of the filter cake of two kinds of weakly caking coal can be reduced by about 5%,and the reforcing draining effect on the Liuwan coal is slightly weaker.When the dosage of SDBS at 500g/t,the moisture content of the Liuwan coal cake can be lowered at 3.1%.In the nonionic surfactants,the filtration effect of AEO and OP is also ideal.When AEO-3 and AEO-7 are used as dewatering agents,at the dosage is 500g/t-750g/t,the moisture of the filter cake of three kinds of coal can be reduced by 3-4%.After the action of OP-4,the water content of three kinds of coal can be reduced by about 3-5% under the appropriate dosage.Combined with the influence of AEO series surfactants on the contact angle and surface tension of the Liuwan coal sample,it is preliminarily believed that its filter effect is achieved by increasing the surface hydrophobicity of the coal particles and reducing the surface tension of the filtrate.The results of filtration test of polyacrylamide(PAM)on Liuwan flotation concentrate showed that,the volume of the filter cake after the action of PAM was significantly larger than the blank test or after action other agents,it shows that PAM has the function of fluffy filter cake's structure,so it has the effect of improving the filtration speed,but has little effect on the water content of the filter cake.When PAM combination with surfactants are used in filtering,the moisture can be reduced and the filtration speed can be accelerated,besides,the total consumption of agents is also greatly reduced.Aiming at the problem of high moisture of fine coal slime in Majialiang coal preparation plant,based on the laboratory results of dewatering agents selection,SDBS as industrial test dewatering agent.When the dosage was 750g/t and 1200g/t respectively,the moisture of filter cake of plate frame filter press and pressure filter press could be reduced by 1.30% and 1.83%.The research results in this paper can guide the coal preparation plant to reduce the moisture of fine coal slimes. |
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