Study On NO_x Emission Characteristics Of Biomass Gasification Gas Combustion With Nitrogenous Compounds

The direct combustion of biomass gasification gas application is more common in biomass based medium and small scale boilers heating as well as biomass gas-coal co-firing power generation.The problem of NOx emission pollution caused by the combustion of gasified gas with nitrogen content is worth studying in depth.In this paper,through building biomass gasification gas with nitrogen content combustion test bench,the NOx emission characteristics of biomass gasification gas with nitrogen content are studied under different combustion conditions,providing guidance for controlling NOx emissions during combustion of biomass gasification gas.The influence of various combustible components on NOx emission characteristics in biomass gasification gas was studied separately.Under without NH3 condition,the results showed that the NOx emissions of the each combustible component combustion were related to its heat value.The higher heat value,the higher NOx emissions.When the gas containing NH3,n CO and CH4 combustion can promote NH3 oxidation to NO,while,the water vapor from the burning of H2 can inhibit the generation of NO.Because of the steam produced during the combustion of CH4,the NOx emissions of CH4 combustion were lower than that for CO,under the same Concentration of combustible components.Finally,the NOx emission rules can be predicted by by calculating the NOx emission from combustion of various combustible components.The NOx emission characteristics of biomass gasification gas with nitrogen content in combustion chamber were investigated.The changes of the NOx emission in the premixed combustion and the forced convective diffusion combustion are compared under different combustion conditions.The study found that the NOx emissions from pre-mixed combustion were always higher than that of the forced convective diffusion combustion.The increase of excessive air coefficient will increase the NOx emission of diffusion combustion,but have no effect on the pre-mixing combustion.With the temperature increasing,the premixed combustion NOx emissions were increased,while the forced convection diffusion combustion NOx emissions will be increased in 800-900 ?,but reduced in 900-1100 ?;by staged combustion and air distribution,under the condition of 800 ? combustion temperature,NH3 concentration 460 mg/m3 and total excess air coefficient 1.15,the NOx emissions from biomass gasification gas with nitrogen content combustion can be optimized to 126mg/m3,which was about the 24 percent NOx emissions of pre-mixed combustion and 50 percent NOx emissions of forced convective diffusion combustion.The NOx emission characteristics of biomass gasification gas with nitrogen content in natural convection combustion conditions were investigated.The influence of NH3 concentration,gas preheating temperature,gas flow velocity and gas export diameter on NOx emission was studied experimentally.The results show that NOx is mainly from fuel-NOx,and mainly NO,while NO2 is the product of NO reaction with excess oxygen in flue gas.When preheating temperature to 400 ? above,due to the oxidation of ammonia in reductive atmosphere,the NOx emissions under the condition of the natural convection will be reduced.Under stable combustion conditions,because of the flow rate increasing will increase the contact area of gas and air,the increase of gas flow velocity will increase the NOx emissions,while the change of the gas outlet diameter have less influence on NOx emissions.