Investigation On Combustion Characteristic And Nitrogen Oxides Conversion In Co-Combustion Of Coal And Straw

Co-firing of biomass and coal is an effective way, which can decrease the emission of pollution, to improve the utilization of biomass energy and save energy. At present, countries throughout the world are faced with the problems of energy shortages and environmental pollution. So it is imperative to develop the technology of the mixed fuel and improve the theory of co-firing.In the paper, the combustion characteristics and combustion characteristics of mixtures of deashed straw and coal are explored by using of thermal analysis technology. The effect of the proportion of mixed, the combustion atmosphere, the kind of adding minerals and the quantity of adding minerals on the combustion characteristics for deashed sample is explored. The results show that: the different proportion of straw mixed have a greater impact on combustion characteristics of co-firing. With increasing of the proportion of straw, the largest weight losing, the heat released peak value of volatile and the index of combustion characteristics all have trend of increasing. In addition, when the proportion of mixed straw is up to 20%, the ignition temperature is the minimum; it is in favor of burning of sample so that make firing point schedule, improve the rate of burning and improve the combustion characteristics, when the content of oxygen increased. The effects of addition of mineral composition, including K, Na, Ca and Mg, on the burning characteristics of the sample is related with the ratio of mixed of straw and coal and the addition content of mineral. The K and Na can catalytic combustion and the catalytic role of K stronger than Na, while the Ca and Mg inhibition burning. At the same time, the combustion kinetic model is making according to the results of the tests.While release properties of NO was studied by static combustion system during the deashed straw and coal burning alone and mixed. This paper analyzes the effect of proportion of mixed straw and temperature on the emission of NO. The study focused on the inhibition role of the mineral additives on the released process of NO. Research shows that: it can effectively reduce NO release by mixed a certain percentage of straw, but the decreased range was also affected by the inherent ratio of nitrogen of fuel and mixed ratio of straw. NO generation in middle temperature. The conversion rate of NO increases with temperature increasing and make the ending time of release of NO ahead. Alkaline mineral K, Na, Ca, Mg play a certain catalytic role in the reduction of NO. The effect is related with the catalytic activity, addition content and properties of fuel, such as mixed ratio. In the most appropriate amount of addition for the four kinds of minerals, the comparison result of a single case of catalytic effect was that Na> K> Ca> Mg. At the same time, the generation kinetic model of NO in determinated in co-firing.Based on grey theory, different impact factors of NO conversion from co-combustion of coal and straw were analyzed. By the gray unite analysis of the influence factors, we found the greatest influence factor and subordination ones for NO conversion. According to the results, the grey theory model of NO conversion from co-combustion is established.