Study On NO Emission Characteristics Of Co-Firing Coal And Biomass In O₂/CO₂ Atmosphere And Melting Characteristics Of Ash

Combusting coal and biomass by using circulating fluidized bed boiler in oxygenenriched environment is a sample and feasible combustion mode,which has great significance in adjusting energy structure and reducing emissions of pollutants.Although the blending of biomass can reduce the effect of pollutant emissions but also affect the melting characteristics of ash.The melting sintered characteristics of the ash are related to the design and safe operation of the boiler.Therefore,it is necessary to study the emission characteristics of coal mixed biomass and the melting characteristics of mixed ash.Only a comprehensive consideration of these two aspects of the pros and cons will have a practical significance to the production.In this paper,the anthracite and pine powder in Shandong area were selected as the experimental samples for further complete study.The experiments were carried out with the small bubbling bed combustion system for the experiment.At the same time,the mixed furnace was prepared by horizontal resistance furnace.The experiment explores the effects of different oxygen concentration(21%-40%),temperature(850?-950?)and mixing ratio(0%-30%)on the formation of NO.The ash samples which were made in the above conditions were measured by ash melting point,X-ray diffraction phase analysis and SEM-EDS analysis respectively.The influence of the above conditions on the sintered properties of the ash sample was analyzed from the perspective of mineral change.The experimental results of nitrogen oxides show that increasing oxygen concentration in the environment may produce more NO during the combustion process,regardless of whether the biomass was blended or not.The increase of temperature promoted the conversion of nitrogen in the anthracite and accelerated the release of the volatiles from the pine powder.The volatile diluted oxygen concentration in the environment,leading to a suppression of NO emission with rising temperature during the mixed combustion.In addition,increasing blending ratio may result in a decrease of NO emission,because the large amount of intermediates releasing by burning pine powder have a reduction effect on NO.The experimental results of mixing ash show that with the oxidation of the ash environment to enhance the promotion of anthracite ash in the melting process,while a large number of trivalent iron ions in the minerals will reduce the melting characteristics of ash temperature.The increase of ash temperature promotes the formation of feldspar minerals in ash,and the increase of temperature has the effect of reducing the melting characteristic temperature of ash.After blending pine powder with anthracite,the increase of alkali metal and alkaline earth metal content and the decrease of silicaalumina mineral element.So that the melting characteristic temperature of the mixedash sample is negatively correlated with the blending amount.