Numerical Simulation Of SNCR Denitrification Process In Circulating Fluidized Bed Boiler

The emission of nitrogen oxides is a serious hazard to the environment in which human beings live.The formation of acid rain and destruction of terrestrial vegetation,crop production,and even the formation of photochemical smog damage the human respiratory system and reduce nitrogen oxides emissions is imperati ve.Industrial emissions are the main source of nitrogen oxides,the power industry emissions of nitrogen oxides accounted for about 70% of industrial emissions,starting from the power industry to reduce emissions of nitrogen oxides is inevitable.The measures to control the emission of nitrogen oxides are flue gas combustion technology and low nitrogen combustion technology.The selective non-catalytic reduction technology(SNCR)in flue gas denitrification technology is widely used in Circulating fluidized bed boiler cyclone separator for the SNCR reaction occurs within the temperature window,the residence time conditions.In this paper,the cyclone separator as the research object,the impact of a variety of factors on the SNCR denitrification efficiency.Firstly,the material balance calculation and heat loss calculation of SNCR denitrification system are carried out on the CFB boiler.The key parameters of numerical simulation are obtained,such as the dosage of reducing agent and the dosage of dilution water in denitration process.The change of thermal efficiency of the boiler after denitrification by SNCR shows the feasibility of installing SNCR denitrification system in circulating fluidized bed boiler.At the same time,three kinds of flue gas denitrification systems are introduced,the components of each system are given,the requirements of reducing agent storage tank are analyzed,and the advantages and disadvantages of denitrification system are analyzed.Based on the results of the material balance calculation,the velocity field and pressure field of the cyclone were analyzed by means of Fluent platform.The arrangement of nine kinds of reducer nozzles was set up,and the concentration distribution of the reducing agent was compared with the ni ne kinds of arrangement And the molar ratio of ammonia to nitrogen.The arrangement of the six nozzles on the inside of the inlet was selected to carry out the subsequent calculation.The effects of temperature,ammonia mole ratio,oxygen content,injection parameters and circulating ash on the denitrification efficiency were analyzed by means of Fluent software,and a reasonable SNCR reaction mechanism was selected,combined with the arrangement of selected reducer nozzles.The results show that the denitrification efficiency increases first and then decreases with the increase of temperature,and the ammonia escape gradually decreases.At about 915 ?,the denitrification efficiency reaches the maximum.Ammonia nitrogen ratio increased,the reaction temperature window widened,but the optimal denitration temperature did not change,the amount of ammonia escape increased.The effect of injection parameters on denitrification efficiency and ammonia escape was small.Considering the effect of recycle ash,the denitration efficiency is improved,the reaction temperature window is widened and the ammonia escape is reduced.Adding H2,CH4,CO and other gases,will promote the reaction temperature window towards the low temperature direction of movement,but the highest denitrification efficiency will be a little decline.