Study On Co-combustion Kinetics And Ash Fusion Kinetics Of Biomass With Bituminous Coal

Four biomasses (beet, corncob, hardwood and switchgrass) and the mixtures of biomasses and bituminous coal were studied by experiment carried out in the air atmosphere and oxygen-enriched atmosphere, respectively. TG-DTG curves of samples in combustion process were obtained, and some analyses on the influence of heating rates, oxygen concentration, blend ratios and samples of biomasses on combustion characteristics and kinetic characteristics, and the combustion characteristics of biomasses were compared with those of bituminous coal. TG-DTG-DSC curves of ash fusion process for some samples, then ash fusion kinetics of these samples were determined.In the air atmosphere, with the heating rate increased, so did the comprehensive characteristic index of biomasses and bituminous coal. At certain heating rate, the greater blend ratios of biomasses, the volatile matter release index and comprehensive characteristic index was higher. In the oxygen-enriched atmosphere, as the oxygen concentration increased, so did the comprehensive characteristic index of biomasses and bituminous coal, and the volatile matter release index and comprehensive characteristic index of most of the mixtures increased.In the air atmosphere, the reaction mechanisms of biomasses at pre-peak were random nuclear producing and growing process or three-dimensional diffusion, while the reaction mechanism of biomasses at post-peak was random nuclear producing and growing process. The reaction mechanism of bituminous coal was chemical reaction around the peak. The apparent activation energy of four biomasses was in the range of102.27kJ/mol to223.64kJ/mol at pre-peak, while38.06kJ/mol to167.37kJ/mol at post-peak. And the mechanisms for mixture of biomasses and bituminous coal at pre-peak were random nuclear producing and growing process and three-dimensional diffusion, the reaction mechanism at post-peak was in conformity with random nuclear producing and growing process. The apparent activation energy of mixtures were in the range of100.53kJ/mol to252.11kJ/mol at pre-peak, and43.64kJ/mol to239.42kJ/mol at post-peak.In the oxygen-enriched atmosphere, the reaction mechanisms of biomasses at pre-peak were random nuclear producing and growing process or three-dimensional diffusion, while at post-peak, the reaction mechanism of biomasses was random nuclear producing and growing process or chemical reaction. The reaction mechanisms of bituminous coal at pre-peak were chemical reaction, three-dimensional diffusion and random nuclear producing and growing process, while the reaction mechanisms at post-peak were chemical reaction and three-dimensional diffusion. The apparent activation energy of four biomasses were in the range of84.26kJ/mol to196.94kJ/mol at pre-peak, at post-peak, the apparent activation energy of four biomasses were in the range of19.70kJ/mol to183.26kJ/mol. The mechanisms for mixture of biomasses and bituminous coal at pre-peak were random nuclear producing and growing process or three-dimensional diffusion, the reaction mechanisms at post-peak were in conformity with random nuclear producing and growing process and three-dimensional diffusion. The apparent activation energy of mixtures were in the range of58.39kJ/mol to208.47kJ/mol at pre-peak, at post-peak, the apparent activation energy of mixture were in the range of7.05kJ/mol kJ/mol to185.40kJ/mol.The ash fusion reaction of biomasses happened in the range of1036～1289℃, while the ash fusion reaction of bituminous coal happened in the range of1260～1290℃, and the ash fusion reaction of the mixture with bituminous coal happened in the range of1096～1289℃. In ash fusion process, the reaction mechanisms of biomasses, bituminous coal at pre-peak were random nuclear producing and growing process and chemical reaction while at post-peak, the reaction mechanisms were in conformity with random nuclear producing and growing process and three-dimensional diffusion. The reaction mechanisms of mixtures of corncob and bituminous coal at pre-peak were random nuclear producing and growing process and chemical reaction, while at post-peak, the reaction mechanisms were in conformity with random nuclear producing and growing process.