Study On Process Of Flow And Combustion In Biomass Gasifier

Biomass energy is a kind of ideal renewable energy, and its development and utilization technology is an effective method for energy conservation and emission reduction. Using the biomass to alternative fossil energy can improve the atmospheric environment and reduce acid rain. It can also reduce the content of carbon dioxide in the atmosphere and improve the "greenhouse effect". The study on the biomass gasification process can improve biomass gasification technology level of China and promote the development and utilization of the biomass energy, which can improve our atmosphere and the ecological environment. Based on the above goal, the numerical simulations have been carried out to investigate the physical characteristics of the gasification, the flow in small biomass gasifier, and the gasification in fluidized bed in the present paper.First, the simulations of the internal flow field for the existing wind device were conducted by using the CFD software, through the analysis of the flow field, found that single pipe type and ring plane air feed device can’t realize balanced ventilation. Gas distributor was developed in this paper. The internal flow field of gas distributor was simulated. We found that gas distributor can realize balanced ventilation.Secondly, distribution plate of gas-solid fluidized bed opening rate was optimized using CFD software, and then the best opening rate distribution board was used to measure the parameters such as local solid concentration and pressure drop of gas-solid fluidized bed. According to the parameters of the comprehensive research, determined the best opening rate is6.47%. And the results of the study show that, with the increase of the opening rate, the pressure drop of distribution board and the size of bubble near the distribution board decreases, and the quality particle flow decreases. We researched gas and solid speed under the three drag force model of Syamlal-O Brien, Gidaspow and Wen&Yu.Thirdly, the gas composition was predicted by using the dynamic model based on the experimental results of the literature. The influence caused by the outside conditions in gasification process was analyzed, and found that the ratio of air and water vapor is the important parameters which influence the temperature and gas components. The score of H2and CH4increased, and the score of CO decreased with the ratio of air and water vapor increasing. The results were consistent with experiments.Finally, the investigation of the smoldering process was carried out by using the theoretical analysis and the simplified dynamic model, and the energy balance calculations of the sawdust particles and sawdust packed bed were carried out, combined with the continuity equation and momentum equations established the mathematical model of the smoldering process, which will develop the theoretical foundation for the study on the smoldering process.