The Occurrence,Release Of Chlorine And The Mercury Removal Performance Of Chlorine-rich Coke In Xinjiang High-chlorine Coal

High-alkali and high-chlorine elements in Xinjiang coals are the main causes of fouling and slagging corrosion of boilers and heat exchange surfaces.The occurrence,migration,and heterogeneous reaction of alkali metal element such as Na/K/Ca/Mg/Fe are the main focuses in existing research,however the occurrence form and release characteristics of chlorine have not yet attracted much attention.In this work,the occurrence form and thermochemical migration behavior of chlorine in typical Xinjiang high-alkali and high-chlorine coal were investigated combining with a variety of advanced test and analysis methods,and a new idea for directly preparing chlorine-rich coke and mercury removal adsorbent by pyrolysis and activation of high-chlorine coal was proposed,which provided scientific basis for the development of a new efficient and comprehensive utilization method of pyrolysis polygeneration of high-chlorine coal.The total content of chlorine in five typical high-alkaline coals in Xinjiang was determined by Ischka mixture connecting with melt-ion chromatography.The occurrence form of chlorine in raw coal was explored combining with the means of correlation analysis method,fractional extraction,density separation,low-temperature ashing experiments and the source of chlorine.The results show that the chlorine content in the five raw coals named WX,SEH,XHS,WCW,and HSQ is between 1.170?0.075%,which varies widely.The chlorine content in the coal is positive with the Na and Ca content Correlation,and inversely correlated with S content.The chlorine in coal is mainly uniformly distributed in the pore structure of the coal matrix in the form of inorganic water-soluble ionic state,and the inorganic chlorine proportion is more than 90% in the five raw coals.The on-line analysis and static equilibrium method were used to analyze the heat release characteristics and the products distribution of WX coal under different atmospheres.The results show that the organic form of chlorine in the raw coal is mainly released by the form of HCl,Cl₂ and organic chlorine in the low temperature stage,and in the high temperature stage,the remaining chlorine is released in the form of Na Cl under the atmosphere of Air and CO₂,but 61.70%of chlorine is still not released under the N₂ atmosphere at 1000?.Part of the inorganic chloride ions in coal would combine with sodium to generate Na Cl,and the other part would convert into organic form by the C-Cl bonds adsorbed on the microporous surface of coal during pyrolysis.The mercury removal performance and mechanism of chlorine-rich coke were analyzed with the methods of mercury adsorption and desorption experiments combining with four kinetic adsorption models.The results indicate that the chlorine content appears to be enricher,and the C-Cl bond formation on the surface is stronger in the chlorine-rich coke with the increase of coking temperature.In the process of mercury removal with chlorine-rich coke,the Hg⁰ is first captured to the surface and inner pore wall of coke by physical action,and then combined with the C-Cl site to be oxidized to Hg Cl₂,thereby forming a stable chemisorption.402.23?g/g of Hg⁰ equilibrium adsorption amount is achieved for the activated char obtained by pyrolyzing coal at 600°C combining with CO₂ activation at 900°C,which shows a good mercury adsorption performance.