Effect Mechanism Of Binder On Forming And Combustion Process Of Shendong Long Flame Coal

Under the"double carbon"target vision,the realization of clean utilization of coal resources is the key to promote the energy revolution and build a low-carbon and efficient modern energy system.Due to the characteristics of poor raw material quality,low combustion efficiency and wide distribution,bulk coal leads to serious energy waste and environmental pollution,which is the key and difficult point to promote the clean energy technology system.Clean coal technology as one of the most effective means of solving the problem of loose coal,subject to the lack of high quality coal resources in recent years,clean coal technologies such as well as the limited production and promotion,and the substitution of low rank coal for high quality coal preparation of environment-friendly coal is more conform to the national conditions.Based on the characteristics of raw coal adaptation compound binder is the development direction of producing high strength,low cost and low pollution briquette products,which also puts forward higher requirements for the optimization of coal-binder adaptation technology.In view of the above problems,this thesis selects Shendong long-flame coal,which is often used for steam coal,as raw material,and selects three organic binders of calcium lignonate,sodium humic acid and starch,and three inorganic binders of magnesium chloride,kaolin and bentonite.By exploring the influence of a single binder on the wetting behavior,mechanical mechanism,combustion characteristics and pollution emission characteristics of long-flame coal.The influence mechanism of binders on efficient molding and clean combustion of long-flame coal was studied,which provided technical support for screening,mixing and optimization of binders in the process of preparing environment-friendly briquette from long-flame coal.The main research contents are as follows:he wetting behavior of long flame coal will be affected by different amount of single binder.This thesis characterized the wetting behavior of coal surface by measuring dynamic contact Angle,adsorption saturation time and adsorption saturation rate.The addition of starch and bentonite can make the surface of long flame coal have a higher adsorption rate,which is conducive to the spread and wetting of binder molecules on the surface of long flame coal.Both sodium humate and magnesium chloride significantly reduced the adsorption capacity of long flame coal and helped to reduce the hydration layer thickness of coal surface.Kaolin inhibits the adsorption and wetting process of long flame coal,but the overall adsorption capacity is higher.The bonding effect of different binders on briquette is significantly different.The thesis measured the briquette forming strength of a single binder,and analyzed the surface structure and chemical structure characteristics of the samples with the highest forming strength.The results show that sodium humate,starch and bentonite have the best forming effect on long flame coal,while calcium lignonate,magnesium chloride and kaolin have poor forming effect.More hydroxyl and oxygen-containing functional groups are generated on the briquette surface after the formation of starch,sodium humic acid and long flame coal,which enhances the interaction between coal particles.Sodium humate and bentonite can be evenly dispersed among the coal particles to form a dense micellar structure and improve the molding strength of briquette.The combustion characteristics of briquette with the best forming effect by single binder were studied by thermogravimetric method.The results show that the three inorganic binders,kaolin,bentonite and magnesium chloride,can improve the volatilizing analysis and precipitation rate of long-flame coal,and inhibit the combustion and decomposition of coal.Starch can promote the ignition and combustion of long flame coal,but the thermal stability is poor,while sodium humate and calcium lignosulfonate have good thermal stability,can ensure the thermal strength of briquette.The effects of Al₂O₃,SiO₂and Na⁺in the binder on the transformation and release characteristics of typical polluting elements such as N,Cl and C during briquette combustion were studied.The results show that Al₂O₃,SiO₂and Na⁺can promote the conversion of N at lower temperature,and have a synergistic effect.NO is the main product of N conversion.Na⁺can inhibit the release of volatile NO,and the combination of Al₂O₃and SiO₂can promote the production and release of NO.Paraxylene（PX）is a volatile organic pollutant formed in the devolatilization stage of coal combustion.Al₂O₃,SiO₂and Na⁺can promote the release of PX at low temperature,Na⁺increases the total release of PX,while Al₂O₃and SiO₂reduce the release of PX through catalytic degradation or adsorption.In the combustion process,Cl mainly transforms into HCl.Na⁺significantly promotes the release of HCl in the early stage of combustion and increases the total emission,while the composite formed by Al₂O₃and SiO₂has an inhibitory effect on the formation and release of HCl.The addition of Na⁺and additives in raw coal can promote the rapid ignition and full combustion of coal and reduce the generation and release of CO.By exploring the influence of binder on the molding and combustion process of Shendong long-flame coal,the thesis draws the following conclusions:sodium humate and starch have the best molding effect on long-flame coal,and promote the combustion of high-ash and high-volatile long-flame coal.Sodium humate can reduce the production of NO and CO,but promote the conversion of HCl and PX.Al₂O₃,SiO₂and other components in kaolin can achieve a better inhibition effect on HCl and PX,and mixing with starch and sodium humate can play a role in emission reduction.Based on the comprehensive benefits of economy,high efficiency and environmental protection,three binders of sodium humate,starch and kaolin are selected,which have low raw material cost and significant economic benefits.The three binders have realized the reasonable combination of organic-inorganic,which not only improves the molding and combustion performance of long-flame coal,but also effectively reduces the formation and release of pollutants such as NO,paraxylene,HCl and CO in the combustion process,which has practical significance for the development of environment-friendly briquette products of long-flame coal.