Study On Dry Forming Technology Of High Sulfur Coal And Sulfur Fixation Characteristics During Combustion

In 2017,China's annual consumption of civil bulk coal is about 200 million tons,of which 91% is used for living energy and winter heating of rural and township residents in northern China.According to statistics,the particulate matter discharged from civil coal combustion which provides the heating and cooking functions for rural residents accounts for 44% of the total coal-fired emissions.The particulate matter pollution caused by dispersed coal combustion is one of the main causes of haze weather.Based on the concept of "coal stove matching",it is one of the important development directions to study the high efficiency modified clean briquette technology by using additives to improve the quality of Inferior Bituminous coal and high sulfur coal.In this paper,taking high sulfur coal as the research object,the briquette briquetting system was designed to carry out briquette briquetting experiments,and the briquette combustion equipment was designed and built to study the briquette briquetting and its combustion and sulfur retention characteristics.XRD,SEM-EDS and other testing methods were used to study the distribution of S element in ash and slag after combustion of high-sulfur coal.The combustion characteristics of high-sulfur briquette with different temperatures,sulfur fixing agents and biomass were investigated by comparing simulation calculation with combustion experimental results.The briquette briquetting experiments show that the drop strength of briquette increases with the increase of pressure when the pressure is less than 8 MPa with the same particle size composition.When the pressure is greater than 8 MPa,the drop strength of briquette decreases with the increase of pressure.The particle size distribution law of pulverized coal briquette is analyzed theoretically.The results show that briquette with higher strength can be obtained when two particle sizes are dominant in the process of pulverized coal briquetting.At 8 MPa,the optimum particle size distribution of pulverized coal is as follows: fine particle size(less than 0.2 mm)30%,intermediate particle size(0.2-0.5 mm)9% and coarse particle size(0.5-6 mm)61%.The experimental results show that the sulfur fixation efficiency of briquette can reach 51% when the combustion temperature in the furnace is 850 ? without any sulfur fixing agent.The sulfur retention rate of calcium oxide briquette reaches 73.97% at 850 ?,which is higher than that of sodium acetate briquette 67.21% and sodium carbonate briquette 66.54%.In addition,the sulfur retention capacity of high sulfur briquette with 15% corn straw and wheat straw was almost equal to 64%.Based on Gibbs minimum free energy principle,the combustion process of briquette was calculated and analyzed.The results show that sulfate content in briquette ash decreases when combustion temperature exceeds 850 ?,more sulfur dioxide will migrate to gas,sulfur fixation rate of briquette decreases,and sulfur fixation effect is best when the temperature of sulfur fixation reaction is about 850 ?.When the combustion temperature is lower than 850 ?,the sulfur dioxide content of high sulfur coal with three kinds of sulfur fixing agents increases with the increase of temperature,and the sulfur fixing rate of briquette decreases.The results also show that when the temperature exceeds 850 ?,the sulfur retention effect of high sulfur coal with wheat straw and biomass straw is almost the same.