Study On Emission Characteristics Of Nitrogen Oxides During Blended Coals Combustion

China is the biggest country of coals production and consumption at peasent in the world, and also only a strong nation whose energy structure is mainly dependence on coals. This energy structure will not be changed in a long time.Most coals in our country are directly put into combustion, atmosphere pollutants during combustion are one of major pollution sources, in which emission and control of nitrogen oxides(NOx) are hot problems in resent twenty years.These pollutants heavely damage health and living environment of mankind, which have caused widespread attention. Environment and energy have confined development of mankind. How to raise efficiency of power plants fired by coals and simultaneously suppress release of pullutants is one of urgent-solve problems faced by every coutries in the world. Resently, scholars home and abroad have done a series of theory and experimental researches on formation and release of pollutants during pulverized coals combustion and also made considerable progress.However, researches on emission characteristics of nitrogen oxides during blended coals combustion are rather rare.Because of deficiency of transportion capacity and related policy of priority of using inferior coals, enterprises cannot combust single coals and have to use blends of two or more than two kinds of coals. Properly making use of blended coals can save resources and raise efficiency of boilers and economical benefits.Whereas, if blended coals are made up improperly, problems such as increasement of emission amount of pollutants will be arised. Therefore, discussing emission regularity of nitrogen oxides in order to control pollutants release, realize high efficiency and clean combustion of pulverized coals, is a meaningful job at present. Emission characteristics of nitrogen oxides during blended coals combustion are studied in this paper.To begin with, emission characteristics of nitrogen oxides during pulverized coals combustion were explored; Influence regularity for volatile to peak value, appearance time of peak value, total release time and formation amount of nitrogen oxides were discussed. Results showed that linear relationship between volatile matter contents and parameter discussed above was generally presented. With the increasement of volatile matter contents, peak value increased, appearance time of peak value advanced, total release time shortened, emission amount was smaller; Relationship between emission amount and peak value, appearance time of peak value, total release time of nitrogen oxides was studied. Results generally presented that greater and greater peak value was, less and less emission amount of nitrogen oxides was; later and later appearance time of peak value, more and more emission amount was;greater and greater total release time was, more and more emission amount was; Making use of grey relatedness theory, major characteristical indexes during pulverized coals combustion are collated based on emission amount of nitrogen oxides. Results showed that carbon, nitrogen and hydrogen contents were major influence factors; Based on grey relatedness analysis, regression predicting model for emission amount of nitrogen oxides was created. Ultimate simulation results were correspondence with experimental values. Therefore, mathematical model created in this paper can accuarately predict emission amount of nitrogen oxides during pulverized coals combustion.Next, emission characteristics of nitrogen oxides during blended coals combustion were stressly explored. Influence regularity caused by component coals, blending ratio, temperature and oxygen concentrate were emphasisly studied. Results showed that emission process of nitrogen oxides during blended coals combustion was extraordinary complex and existing interaction and interrelationship of every kinds of factors and also interaction and interconfinement of component coals. Blending ratio, temperature and oxygen concentrate were major influence factors during blended coals combustion.They affected emission characteristics distinctively due to difference of component coals.Finally, utilizing BP neural network, mathematical model for predicting emission amount of nitrogen oxides during binary blended coals combustion was created. In this model, eleven factors including component coals characteristic indexes, blending ratio, temperature and oxygen concentrate were input variables, emission amount of nitrogen oxides was output variable. Results showed that emulation values were in correspondence with measured values.This model could accurately predict emission amount of nitrogen oxides during blended coals combustion.Emission characteristics of nitrogen oxides during blended coals combustion were studied detailedly in order to accmulate valuable experimental data and theory research conclusion and provide refered laws for reasonable design manufacturature and safe economical and clean operation of large-scale power plants fired by blended coals.