Research On Nitrogen Precipitation Effect Of Mixed Coal Pyrolysis And Combustion

Coal consumption is still dominant in China's energy structure,while thermal power stations will discharge a large amount of atmospheric pollutants into the environment due to burning a large amount of coal.One of the major pollutants is nitrogen oxides,which will cause major adverse effects such as haze,photochemical smog and acid rain.At the same time,in order to deal with the energy crisis,most of the coal-fired generating units in China use mixed coal combustion.Reasonable selection of coal powder type and appropriate mixing ratio can give full play to the advantages of single coal,and bring better influence to the safety and economy of boiler.In this paper,the nitrogen release effect of mixed coal during pyrolysis and combustion is systematically studied by combining theoretical analysis with experimental verification.According to the experimental characteristics,we set up the required experimental platform in the laboratory,three kinds of lignite,bituminous coal and anthracite with large difference in coal quality were selected for pyrolysis and combustion experiments respectively,the effects of different mixing ratio,temperature,particle size and excess air coefficient on nitrogen precipitation were studied.Based on the experimental results of pyrolysis and combustion,the effects of nitrogen precipitation characteristics on NO formation during coal pyrolysis were analyzed.The main conclusions in this paper were as follows:(1)With the increase of coal rank,the release amount of NH3 gradually decreases and the release amount of HCN gradually increases.(2)In the pyrolysis process of mixed coal,the production of HCN-N and NH3-N gradually decreases with the increase of coal particle size.Generation of HCN-N and NH3-N were gradually increased along with the rise of temperature,but after 1000?NH3-N generation began to decline.(3)The lower the coal rank,the lower the total NO release.In mixed coal combustion,with the increase of the mixing ratio of low-rank coal,the total NO release decreases gradually.(4)Under the condition that the ratio of each mixed coal is 1:1,with the increase of temperature and excess air coefficient,the NO precipitation rate of each mixed coal increases gradually in the combustion process.(5)During the pyrolysis and combustion of mixed coal,the release of NO increases with the precipitation rate of nitrogenous precursor.Meanwhile,the more HCN is precipitated by pyrolysis,the less NH3 is,and the higher NO is released by combustion.It has a great significance for China's energy strategy to form targeted nitrogen oxides removal method and control technology through experimental analysis and research,and realize high efficiency and low pollution combustion of coal-fired power stations.At the same time,it also has important theoretical guiding significance for the operation of coal-fired power plants.