Combustion Characteristics And Kinetic Analysis On Biomass And Coal Blends

Biomass and coal co-combustion is a kind of new combustion technology toreduce pollutant emissions and synthetically utilize biomass and coal resources. Theco-combustion of biomass and coal is an extremely complex physical and chemicalprocess. During the co-combustion process, biomass and coal affect and restrict eachother, so the co-combustion characteristic of their blends is different from the singlefuel.In this paper, Pyris1thermobalance analyzer was firstly used to research thecombustion characteristics of three kinds of biomass(haulm, corn straw and saw dust)and two kinds of coal(Qitaihe bituminous coal and Qilianta brown coal) and theirblends. The experiment results show that the co-combustion process can be roughlydivided into four phases: dehydration and drying, biomass volatile evolution andcombustion, transition combustion and coal coke combustion. Biomass and coal hasits concentrated combustion zone. With the increase of heating rate, the ignition andburnout temperature of biomass, coal and their blends delays, while the combustioncharacteristic index has increased.Secondly, the Coats-Redfern method was used to analyze the combustionkinetics parameters of biomass, coal and their blends. The results show that theactivation energy of haulm and corn straw’s later combustion period is larger andtheir frequency factor is smaller, which is opposite to the sawdust combustion. Theoverall reaction activity of bituminous coal is lower than lignite.Then, the differential isoconversional non-linear method was used for the furtheranalysis on the combustion activation energy distribution of corn straw, bituminouscoal and their blends. It is found that the initial reaction activation energy of cornstraw, bituminous coal and their blends is respectively75,152,107kJ/mol. The latercombustion reaction activation energy of the mixture is smaller than that of coal. The combustion mechanism of corn straw and bituminous coal is determined byPopescu method. It is found that the combustion of corn straw is controlled by thefollow random nucleation and subsequent growth model, and the combustion ofbituminous coal is according to the three dimensional diffusion model.Finally, the Weibull distribution model was used to simulate the combustionprocess of haulm, lignite and their blends. The simulation results of different fuelcombustion process are better in various heating rate.