Pulverized coal purification-combustion for the target of carbon peaking and carbon neutrality:Nitrogen transformation of purification reaction

ZHANG Chi; REN Qiangqiang; HAN Shaobo; HU Yujie; CUI Ruifang; LI Linxuan

doi:10.13226/j.issn.1006-6772.24010803

Abstract：Under the background of"carbon peaking and carbon neutrality",the innovation of efficient and clean coal utilization technologies has become a significant research direction in the energy sector.The coal purification-combustion coupling technology,as a novel thermal conversion process,focuses on the efficient removal of fuel nitrogen through a pre-purification process,offering a new pathway for the source control of NOx in subsequent combustion stages.To investigate the influence of reaction temperature on the nitrogen release and transformation characteristics during coal purification,experiments were conducted at varying temperatures on a self-constructed 1 700℃ four-temperature zone drop-tube furnace,based on high-temperature thermochemical conversion mechanisms.The results indicate that as the reaction temperature increased from 900 ℃ to 1 300 ℃,the proportions of H2 and CO in the coal gas significantly increased,along with the gas yield and composition.The conversion rates of various components also increased,with the conversion rate of nitrogen to the gas phase jumping from 48.26％to 83.14％.A considerable portion of coke nitrogen was transformed at high temperatures,leaving only 16.86％of fuel nitrogen in the solid phase coke,which would be the primary source of NOx in subsequent combustion processes.When the temperature reached 1 000 ℃,the conversion rate of fuel nitrogen to N2 exceeded 50％,and higher temperatures further increased the proportion reduced to N2,while also increasing the proportions converted to NH3 and HCN.Promoting the release and reduction of fuel nitrogen to N2 before combustion is crucial for NOx emission reduction in coal combustion.On the other hand,after the purification reaction,the specific surface area and pore volume of Shenmu bituminous coal significantly increased,up to 66.3 times and 10.5 times that of the raw coal,respectively,with a decrease in average pore diameter.The stability of the fuel carbon framework decreased,and the number of reactive sites increased,improving the combustion characteristics of the fuel.This improvement was further enhanced with increasing temperature,demonstrating that the purification reaction is beneficial for the subsequent clean and efficient combustion of the fuel.