Research On Ultra-fine Coal Deashing Technology With CO₂ Phase Changing

This research combine hydrophobic flocculation with two liquid separation,and put forward use liquid CO₂ as agglomeration solution to research the feasibility of ultra-fine coal deashing technology.Samples were provided by the Moxin Po coal preparation plant in Tianfu,Chongqing Province,China,utilized the CDO experiment system to study the influence of liquid CO₂ on ultra-fine coal surface properties,discuss the influences of liberation degree,concentration,stirring system on preparation,further,discuss the influences of pH,dispersant,collector on separation.Fourier Transform Infrared Spectroscopy,X-ray Photoelectron Spectroscopy and micro-calorimeter were used to analyze the variation of surface functional groups and wetting heat.The results show that liquid carbon dioxide could change the percentage of hydrophilic and hydrophobic functional groups.With the increase of reaction time,the content of hydrophilic functional groups increased.Through single factor optimization experiments to liberation degree,concentration,stirring system,found that the grinding time is 15 min,concentration is 33.33g/L,stirring speed are 1000r/min,stirring time is 15 min got the best separation performance.And the ash content decreased from 23.30%to 5.72%,the sulfur content decreased from 2.16%to 1.44%,the ratio of ash reduction is 84.46%,the combustible material recovery is 77.79%.The effect mechanism of all factors as follows.This process based on the hydrophobic flocculation and two liquid separation,so the operating parameters and additives influenced the flocculation and floccules.The liberation degree influenced the maximum flocculation intensity(E_max)and the floccules maximum size(d_max),and the concentration influenced the floccules structure,the function of stirring are make the liquid CO₂ disperse and provide the mechanical energy make the ultra-fine coal and liquid CO₂ to contact,and the stirring time influenced the surface properties of coal.Based on the research of operating factors,have study the influences of pH,dispersant,collector on separation.The pH by influence the electronegativity of coal,the dispersant by influence the distance of coal and the collector by form the adsorbed layer to influence the interaction potential,and change the performance at last.