Research On Coordinated Optimization Of Low Nitrogen Combustion And SCR Denitrification For Coal-fired Boilers In Power Plant

Now,with the overall and rapid development of power of power industry,in 2016 the annual generating capacity reached 5.37 trillion kw?h,of which thermal power generation capacity reached 3.97 trillion kw?h,accounting for 73.93 percent of the total generating capacity,and our national coal-fired power generation is mainly based on coal-based raw materials,the 2016 national heating consumption of raw coal reached 192 million tons.The NO_x,SO₂,and dusts emissions resulted from coal combustion are the significant sources of environmental pollution,Among them,NO_x largely gived rise to the photochemical smog,acid rain and Fog and Haze,thus reducing the power plant emissions of NO_x and other pollutants appears to be without delay.With the increasingly stringent national environmental laws and regulations to be implemented,which induced thermal power plant NO_x emission indicators becoming more and more stringent,appropriate measures are also taken by thermal power plant to reduce NO_x emissions.At present,more than 80% of the power plants adopt four-corner tangential coal-fired boilers,and mostly adopt low nitrogen combustion combined with SCR denitrification technology to reduce NO_x emissions.On the premise to meet the NO_x emission standards,how to adjust the combustion of pulverized coal and spray ammonia,optimizing the relationship between boiler efficiency and SCR operation cost,and having strong realistic guiding significance to energy saving and efficiency increase in the environmental protection system of coal-fired power plant boiler.In this paper,by reading and analyzing the technology and methods of the current domestic and foreign on how to reduce thermal power plant NO_x emissions,especially for 300 MW unit,not only ensure the unit's boiler efficiency,but reduce NO_x emission and save ammonia injection when optimizing the oxygen,air volume of SOFA,the swing angle of SOFA.How to optimize the cost of low NO_x combustion and ammonia spray test program has been designed after through analysis and research,and the experimental study was carried out.The main contents and conclusions are as follows:1.The effects of oxygen,air volume of SOFA and swing angle of SOFA on boiler efficiency and NO_x emission of SCR inlet were studied.Based on the experimental data,the characteristic relationship between boiler combustion mode and boiler efficiency and NO_x emission was established,which obtained the low-nitrogen combustion characteristic curve so as to analyze and observe the effect of combustion mode on boiler efficiency and NO_x emission.2.The quantitative relationship between the NO_x concentration of SCR inlet and the operating cost of denitration reductant was studied.At the same time,the effects of NO_x concentration on ammonia injection and denitrification efficiency were analyzed,which obtained the cost performance curve of SCR denitrification device so as to analyze and observe the influence of SCR inlet NO_x concentration on the amount of ammonia injection.3.Integrated optimization of boiler Efficiency and NO_x Emission characteristic curve by combustion mode,establish the comprehensive cost model of low nitrogen combustion and SCR combined denitration operation,seek the optimal condition,and the economic analysis was carried out before and after the optimization of the operating mode.The results show that by optimizing adjustment the efficiency of boiler is increased by approximately 0.1%,the NO_x concentration of SCR inlet is decreased by about 20 mg / m3,and the amount of ammonia sprayed is reduced by 16.44%,which makes the coal-fired boiler run in the best economy.4.To establish the optimized control curve of oxygen and air volume of SOFA,which takes into account boiler efficiency and SCR denitrification cost optimization,so as to provide theoretical guidance for the adjustment of oxygen and air volume of SOFA in power plants.5.The numerical simulation is performed on the different operation modes of boiler combustion,and the results of numerical simulation accord with the measurements,which provides guidance for the later operation optimization.