Study On CO₂ Adsorption Characteristics Of Coal Macerals And Its Control Methods

According to the current development trend of clean,low-carbon and efficient utilization of coal,the qualitative utilization of coal resources has been paid attention to.The research on the separation and enrichment of coal macerals is of great significance to realize the efficient transformation of coal.In this paper,the dense medium clean coal of Yuan zi gou coal preparation plant in Yong long mining area is taken as the research object.Based on the technology of separation and enrichment of coal macerals by liquid CO₂ hydrophobic agglomeration,the physical and chemical properties of coal macerals are analyzed,the CO₂ adsorption characteristics of different coal macerals are evaluated,and the method of enhancing liquid CO₂ adsorption difference is explored.The results are as follows:（1）The differences of chemical composition,micro morphology,pore structure,surface chemical structure and wettability between vitrinite and inertinite were analyzed.The results show that:the raw coal sample is low ash,low sulfur,high calorific value weakly sticky coal,the content of inertinite is 68.72%,compared with vitrinite,inertinite has higher content of ash,fixed carbon,carbon and sulfur,but lower content of volatile,hydrogen,oxygen and nitrogen;the surface roughness of inertinite is smaller than vitrinite;the micropores on the surface of coal macerals are mostly small The results show that the specific surface area,average pore diameter and single point pore volume of inertinite are larger than those of vitrinite;the types of surface groups of coal macerals are the same,but the number is different,among which the content of free hydroxyl,aliphatic hydrocarbon and amino group is more in vitrinite,while the content of associated hydroxyl,aromatic structure,carboxyl,carbonyl and minerals is more in inertinite;The contact angle of vitrinite is larger than that of inertinite,and the wetting heat of vitrinite is smaller than that of inertinite,indicating that vitrinite is more hydrophobic than inertinite.（2）The CO₂ adsorption characteristics of different macerals were evaluated.The results of isothermal adsorption experiment at 20℃show that the CO₂ adsorption capacity of coal macerals increases gradually with the increase of pressure,which is consistent with the characteristics of type I isotherm.Under the same pressure,the adsorption capacity of vitrinite is always greater than that of inertinite.The Langmuir model is better for describing the process of CO₂ adsorption of coal macerals.With the increase of equilibrium pressure,the surface free energy of coal macerals increases At the same equilibrium pressure,the surface free energy of vitrinite is larger than that of inertinite.（3）The effect of liquid CO₂-water system on the surface properties of coal macerals was investigated.The results show that with the increase of treatment time,the surface hydrophobicity and zeta potential of vitrinite and inertinite increase.This is due to the decrease of oxygen-containing functional groups,the increase of alkyl side chains and the decrease of aromaticity of coal macerals after liquid CO₂ treatment.（4）The effects of electrochemical control and surface modification on the surface properties of coal macerals were explored.The results show that:with the increase of pH value,the surface zeta potential of coal macerals moves from positive potential to negative potential;the contact angle of vitrinite first increases and then decreases;when pH value is equal to 3,the contact angle reaches the maximum,while the contact angle of inertinite always decreases;with the addition of Al Cl₃ solution,the hydrophobicity of vitrinite and inertinite decreases The adsorption capacity of inertinite is higher than that of vitrinite,and the contact angle of vitrinite and inertinite first increases and then decreases with the increase of CTAB concentration under acid condition,and the contact angle of vitrinite reaches the maximum at lower concentration With the increase of SDS concentration,the zeta potential of coal macerals decreases gradually.Under the condition of pH=3 and aluminum chloride concentration of 150mg/L,with the increase of SDS concentration,the contact angle of vitrinite and inertinite first increases and then decreases,and the vitrinite first reaches the maximum.There are 34 figures,21 tables and 101 references in this paper.