No_x Emission Law Of Pressurized Oxy- Coal Combustion

Pressurized oxy-coal combustion is a promising new combustion technology in the CCS field,which can reduce the cost of CO₂ capture and compression,avoid air leakage and reduce the volume of boilers,so this technology can improve the overall system efficiency.Pressurized oxy-coal combustion has more technical advantages than atmospheric conditions.However,there are few studies on the pollutants of pressurized oxy-coal combustion.This paper explores the NO_x emission through experiments and numerical simulations,which has guiding significance for the development of pressurized oxy-coal combustion.This paper uses a pressurized tube furnace experimental system to study the NO_x emission law of three different coal types in an O₂/CO₂ atmosphere,considering four factors such as pressure（0.1³MPa）,temperature（900℃¹100℃）,coal characteristics and oxygen concentration（21%⁴0%）.The study found that pressure is an important factor affecting NO_x.Under the condition of 1000℃and 30%O₂,from 0.1MPa to3MPa,the amount of NO_x first increases and then decreases,reaching a peak at 1MPa.Under the condition of 1000℃and 2MPa,when oxygen concentration increases,NO_x increases.Under the condition of 2MPa and 30%O₂,higher temperature increases the heating rate of particles,so NO_x increases.Under the condition of 1000℃,2MPa and30%O₂,the lignite has the highest NO_x conversion rate,when the anthracite has the lowest.As the volatile percentage increases,the NO_x conversion rate increases.Then the paper designs a new pressurized oxy-coal combustion furnace,studying the effects of different classification conditions,oxygen concentrations and pressure by numerical simulation methods.The study found that the regions where the mid product（HCN and NH₃）is generated are similar with the volatile regions,representing the precipitation of volatile nitrogen.Under the condition of 1MPa and30%O₂,with the increase of the classification levels,the NO outlet concentration decreases.The NO outlet concentration in 3 levels is about 1/4 of the non-gradation.The 2-3 opening method in 2 levels has a similar NO reduction effect with 3 levels.For NO reduction effect and economy,it is more appropriate to choose openings of 1/4 and3/8 away from the furnace top.The oxygen concentration has much influence on furnace temperature,velocity and composition.Under the condition of 1MPa and 2levels,the higher the oxygen concentration,the higher the NO outlet concentration.Under the condition of 30%O₂ and 2 levels,as the pressure increases,the NO outlet concentration decreases.To achieve a better NO_x reduction effect,a higher pressure of the experiment is more suitable.