| At present,biomass boiler systems for large-scale heat supply or steam supply need to gasify the biomass modeling fuel first,then convert it into flammable gas and then burn it.Therefore,the structure and gasification performance of the pyrolysis gasification device matched with the boiler are required.It is of great significance to conduct research on the treatment of boiler combustion flue gas.In this paper,a boiler system with a steam volume of 8t/h and a matching biomass fuel pyrolysis gasification device are studied.The device adopts a three-chamber partitioning of the mixed region of feed,pyrolysis gasification and combustible gas and air.The designed structure avoids the local high temperature during the gasification process compared to the conventional fixed-bed gasifier,and realizes automatic feeding and ash discharging.The output power of the device for the maximum and minimum feeding conditions was tested,and the utilization rate of the calorific value contained in the fuel in the pyrolysis gasification device was about 90%,the carbon conversion rate of the biomass molding fuel can reach 88%.The pyrolysis and gasification of the combustible gas components were tested,and the pyrolysis gasification process was conducted using air-water vapor as the gasification agent,in this way the content of hydrogen in the combustible gas produced by pyrolysis and gasification reached 15.27%~ 17.43%.The grate in the gasification zone has an arc-shaped air flow channel structure,so that when the air flow passes through,there are left,middle,and right three-way air outlet modes,and the air flows are mutually disturbed to avoid fuel accumulated on the grate,that is beneficial to the gasification reaction of biomass fuel.The simulation of the flow of gasification agent in this area shows that when the gasification agent enters the gasification area in a three-way air outlet mode,the velocity is higher and the pressure drop of the gas flow is higher than when the traditional vertical air flow enters the gasification area.Subsequently,the pyrolysis and gasification process of the fuel was numerically simulated,and the combustible gas composition,calorific value,and carbon conversion rate under different gasification parameters were obtained.It was found that the air equivalent ratio was 0.25 in the gasification device.The gasification effect works well when the mass ratio of water vapor to biomass is 0.2.In operating conditions,the combustion of gasified gas produced in the boiler is simulated and the effect of the addition of a swirler at the outlet of the gasification unit on the combustible gas combustion reaction fed into the boiler system is analyzed.The swirling sheet has the effect of promoting the combustion of combustible gas in the hearth,but the flue gas still needs to be treated.Finally,the selective catalytic non-catalytic reduction(SNCR)method was used to remove the nitrogen oxides from the flue gas of the boiler system,and the in-situ experiments were conducted under conditions of different mass concentrations,different reductant injection point temperatures and ammonia to nitrogen ratios.It is concluded that in the denitration process,the urea solution with a mass concentration of 15% has an ammonia-nitrogen ratio of about 2 and is injected into the furnace at a temperature of about 900° C,in this way the denitration efficiency reaches about 84%,which can satisfy the national standards for boiler smoke emission requirements. |
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