Study On Influence Of Coal Quality And Surfactant On Coal Slurry Dewatering

In recent years,with the improvement of the degree of mechanization of coal mining,the mining of thin coal seams,and the strengthening of crushing operations,the output of fine coal has continued to rise,leading to the increasingly acute problem of dewatering for selection products.The low solid-liquid separation effect of the the coal slurry water would worse the sorting effect of the coal selection plant,which lead to the quality of the coal products and the processing capacity of the filtering equipment will be reduced.Meanwhile,the low rank coal surface is rich in oxygen-containing groups and complex pore structure,which makes especially difficult to dewatering.Based on the above issues,this work analyzes the characteristics of coal samples,and studys the effects of coal rank,particle size,oxidation levels,and ash on coal slurry dewatering;then the effect of ion type and molecular structure of surfactant and its mixed recipe on dewatering was studied,combined with mechanism analysis by FTIR,surface tension,Zeta potential,adsorption capacity,wetting heat.The main content and conclusions of the test are as follows:(1)Coal samples with moderate coal rank have the best dewatering effect,and coal rank that is too low or too high is not easy to dewatering.The finer the coal particle size,the more difficult it is to remove water,and the dewatering of-0.125 mm coal slurry is more difficult.The higher the degree of oxidation and the higher the content of oxygen-containing functional groups,the more difficult the dewatering will be.The higher the ash content,the less conducive to coal dewatering.(2)Using cationic duolinel trisopine(DTAB),sodium-sodium phenylzide(SDBS),non-ionic dulate polyoxyethylene ether(AEO9)and zwitterionic cocamide propyl betaine(CAB)four different types of ion types were used to aid in the dewatering filtration.Non-ion surfactants AEO9 filtering effect is the best.For different structures of polyoxyethylene nonionic AEO9,LAE9,OP9 and AEO series of AEO4,AEO7,AEO9,AEO15,AEO20 surfactants to help filter,it was found that polyoxyethylene nonionic surfactants of different structures AEO9 and the AEO series surfactant AEO7 showed better filter-aid performance.(3)The mechanism of filter aid and dewatering of fine coal was studied for AEO7,and it was found that when the dosage of the agent was 120 mg/L,the filter aid effect was the best,and the moisture of the filter cake was reduced by 4.66%.Compared with before the action of surfactant,the vibration absorption peak of the oxygen-containing functional group on the coal surface is the most weakened,the wetting heat is the lowest,the hydrophobicity of the coal surface is most significantly enhanced,the surface tension of the filtrate tends to be stable.When the dosage of AEO7 exceeds 120 mg/L,the surface tension of the filtrate almost no longer decreases,and double-layer adsorption may occur on the coal surface to enhance its hydrophilicity,thereby reducing the filtration and dewatering performance.(4)Using three cationic Gemini surfactants with different structures,propylene bis(dodecyl dimethyl ammonium chloride),propylene bis(dodecyl dimethyl ammonium chloride)and propylene bis(dodecyl polyoxyethylene dimethyl ammonium bromide),respectively denoted as Gemini1,Gemini2 and Gemini3,among which Gemini1 with an amide structure has the best dewatering effect.Three different compound types of surfactants,Gemini1-AEO7,Gemini1-SDBS and Gemini1-ethanol,and Gemini1-SDBS have the best filtration and dewatering effect.Gemini1-SDS and Gemini1-SDBS are two complex systems with structural differences.Gemini1-SDS has better dewatering effect.Gemini1-SDS has the best filtration performance at molar ratio of 6:7.The filter-aid mechanism of the compound surfactant was studied.It was found that when the molar ratio of Gemini1-SDS compound surfactant was 6:7and the dosage was 80 mg/L,the filter-aid effect was better.At this time,the moisture of the filter cake was reduced by 8.32%.Continue to increase the dosage of the surfactant,the effect of filtering aid is not obvious.Compared with a single surfactant,after the compound surfactant is used for filtration and dewatering,the infrared absorption vibration peak of the oxygen-containing functional group on the coal surface is weaker,the calorific value of wetting is lower,and the hydrophobicity of the coal surface is enhanced more significantly.The adsorption test results showed that the adsorption rate and adsorption amount of the surfactants were increased compared with that of the single surfactant.At the same time,the surface tension,cmc value and intermolecular interaction coefficient β value of the compound solution verified the synergistic effect of the compound solution.