Study On Kinetic Characteristics And NO_x Release Characteristics Of Torrefied Biomass And Their Blends With Coal During Isothermal Co-Firing

Reasonable multiple development,efficient use of biomass has become an important means for countries to seek energy,economy and environment harmonious development.The biochar blended coal combustion technology can improve the combustion efficiency and reduce the release of pollutants such as CO₂ and NO_X without retrofitting the existing combustion equipment.It is efficient,clean,low-cost and can be widely promoted.In this paper,the combustion behavior and pollutant release characteristics of torrefied corncob and their blends with coal was investigated.It helps to explore the feasibility of biomass coke as a power fuel,and provides a new type of energy utilization for industrial fields such as electric power production and steel smelting.In this study,the combustion behavior of torrefied corncob and their blends with coal was investigated by using a modified fixed bed thermogravimetric apparatus.The effects of coal ranks,biochar blending ratio,pyrolysis temperature and temperature on the co-firing characteristics were studied.Kinetic parameters of combustion were calculated by random pore model.The results showed that the kinetic activation energy of the combustion can be reduced and the combustion process can be accelerated when torrefied corncob is blended with coal of different coal ranks.As the ash content of the selected coal increases or the volatile content decreases,and the improvement of the biochar on the combustion process of the blended sample becomes more obvious.With the increase of biochar blending ratio,the activation energy of the combustion reaction decreases,the weight loss process of the blended sample is accelerated,and the burning rate increases.As the pyrolysis temperature of corncob increases,the improvement of the combustion process of the blended sample increases first and then decreases.The kinetic calculation results at different experimental temperatures showed that the activation energy of the combustion reaction in the low temperature section?800-950°C?is significantly larger than that in the high temperature section?950-1100°C?.Besides,this work also monitored and recorded the instantaneous concentration of NO and NO₂ during the combustion process of torrefied corncob and their blends with Qingshuigou anthracite.The effects of pyrolysis temperature,biochar blending ratio and temperature on the co-firing characteristics were studied.The results showed that the NO release of co-firing is higher than that of coal combustion,while the NO₂ release is lower.With the increase of pyrolysis temperature,the release process of NO and NO₂ accelerated,and the peak of NO₂ release decreased.With the increase of biochar blending ratio,the NO and NO₂ release curves changed from single peak to bimodal distribution,and the peak of NO₂ release formed in the devolatilization stage gradually increased,and the NO release peak formed in the char-combustion stage gradually decreased.This is caused by the difference in the relative content of volatile-nitrogen and char-nitrogen in biochar and coal.At low temperature?800⁹00°C?,the amount of NO₂ released is higher than that of NO,while at high temperature?900¹100°C?is opposite during the combustion process of torrefied corncob and their blends with coal.And with the increase of temperature,the amount of NO released gradually increased,the amount of NO₂ released gradually decreased.