Experimental Study On Semi-gasification And Low NO_x Combustion Process Of Biomass Pellet Fuel

Because of traditional fossil fuel resources are increasingly depleted and environmental pollution problems are becoming increasingly serious today, abundant biomass energy is getting more and more attention.The existing biomass shaped fuel combustion technology has the problems of low efficiency and excessive nitrogen oxide emissions, so it is urgent to study and develop the combustion technology of biomass shaped fuel with low nitrogen oxide emissions.Taking granular wood fuel as an example, the influence of the component and ash properties of biomass shaped fuel on combustion process is analyzed. Take this as the basis, combined with combustion mechanism of biomass shaped fuel, the author completed the design of biomass semi gasification and combustion system with low nitrogen oxide emissions, which is a kind of combustion mode between "gasification combustion" and "direct combustion":Biomass fuel pyrolysis in the positive pressure gasification chamber, the combustible gas complete combustion process in the burn-out chamber, positive pressure gasification chamber and the burn-out chamber is directly connected. The system uses three graded wind, and adding cyclic cold smoke to control the combustion temperature, the air flow of each duct is controlled independently. The performance index of biomass semi gasification and combustion system is also discussed.According to the design parameters, the thermal calculation of biomass semi gasification and combustion system is accomplished. A corresponding combustion model was established to analyze the flame temperature distribution of the combustion process of granular wood fuel, and to accomplish the calculation of the three graded air flow and the calculation of the circulating cooling smoke flow.Using numerical simulation software to establish the model of the combustor was used to simulate the flow field, choose different structures of secondary air nozzle and burn-out air nozzle, to optimize the structure of the burner. The structure of biomass semi gasification burner has the following characteristics:secondary air and secondary cold smoke rotating inject to the furnace after mixed by the annular nozzle, and burn-out air divided into two strands adherent inject into the burn-out chamber.The combustion test rigs of the biomass semi gasification and combustion system with low nitrogen oxide emissions was designed. And the experimental results show that the performance and environmental protection index of the combustion system can stability standard for a long time, and the nitrogen oxide emitted concentration is less than 140 mg/m3 under the rated load.