Experimental Study On Co-combustion Of Sawdust And Soft Coal In Circulating Fluidized Bed And Numerical Simulation

With the rapid economic development, energy consumption is more and more, thesupply of coal resources is becoming increasingly tense, countries around the world inthe efforts for the development and application of new energy. Biomass energy isconsidered to be the most potential applications of new energy. How its developmentand application to become an important research topic in the worldwide. The wastewood is considered as typical biomass fuel, widespread in many countries research andapplication. As the efficiency of direct combustion is low and poor economy, mixingfiring is consider as effective way to use the waste wood. The mixed firing technologyis currently a way of using renewable energy with low cost and low risks. In addition tocompensate for the shortage of supply of fossil fuels, reduce pollution gas emissions,but also provide employment opportunities, thereby contributing to regional economicdevelopment. Co-combustion technology has entered the application phase ofindustrialization in foreign countries, but in our country the research of the technologyof co-combustion was relatively late, related to application performance is not much.In this paper，the impact of the coal combustion by co-combustion and thecombustion characteristics of soft coal, biomass and their mixtures at different ratioswere studied at first，and then，co-combustion of sawdust and coal in a self-developedsmall scale circulating fluidized bed has been carried out to investigate thecharacteristics of combustion and pollutant emission. The size of the furnace is150mm×150mm. Finally, cold numerical calculation of the characteristics of sawdustand coal particles in the furnace fluidized. The aim is to provide a reference for the rural,urban waste wood combustion applications. The results showed that：①Coal combustion is mainly concentrated in the later stages of sawdust burningis concentrated in the early stages. With sawdust mixing ratio increases, the combustionis divided into two distinct phases.②Volatile in the wood can be precipitated at a lower temperature, mixed withcoal ignition advance to improve the ignition characteristics of fuels.③The maximum rate of sawdust burning is in the early stage. However, themaximum rate of sawdust burning occurs at a later stage, when burning the mixture ofcoal and sawdust, the maximum burning rate is moved forward and improved the burncharacteristics of the fuel. Due to the increase of the heat of combustion of pre-improved sawdust utilization.④The mixture of sawdust and coal can combustion stably in the circulatingfluidized bed.⑤With increasing the proportion of sawdust，the region with highest temperaturemoves up and the temperature variation along the furnace is represented as a convexparabola curve.⑥The volume fraction of NOXincreases with the temperature of the dense phaseincreased. The results also showed that under the same fluidized air velocity, withincreasing the proportion of sawdust, the volume fraction of CO increases, the volumefraction of SO2and NOXdecrease.⑦Through numerical simulation, the fluid structure of sawdust and bed materialparticles is represented as core-annulus. In terms of the sawdust particles，because of itslow density，it is easy to fluidized and blown into the furnace the upper space. With thesame of the amount of circulating solids and the different of the fluidized air velocity,the bed pressure drop decreases with the increase of the fluidized air velocity. With thesame of the fluidized air velocity and the different of the amount of circulating solids,the bed pressure drop increases with the increase of the amount of circulating solids.