| The storage of biomass is very rich in China’s rural areas,but the effective utilization rate of biomass is too low.Most of the biomass is directly incinerated,piled up and corroded for nutrients,or even discarded directly,causing environmental pollution and energy waste.Although more and more industrial boilers use biomass as boiler fuel,most of the small and medium-sized industrial biomass boilers used in China have been converted from coal-fired boilers,just the coal fuel is changed to biomass fuel.In the overall design of the boiler,insufficient research on boiler structure and fuel adaptability has resulted in low boiler thermal efficiency,severe ash and corrosion in the furnace,excessive exhaust gas temperature,and excessive errussion of flue gas pollutants.In view of the defects of existing boilers,combined with the combustion characteristics of biomass forming fuels,research and design boilers suitable for biomass forming fuels,which have important effects and significance for efficient use of biomass,reduction of environmental pollution,and development and design of new biomass boilers.According to the physical,chemical and combustion characteristics of biomass feedstock and biomass forming fuel,the factors affecting the combustion of biomass fuel were analyzed;based on the biomass forming fuel,boiler capacity and design steam parameters,based on the combustion calculation,the boiler selection and structural design were carried out,and the overall layout of the boiler and the heating surface structure were determined;by optimizing the calculation and analysis of the design fuel and checking the thermal characteristics of the fuel,the boiler structure is further optimized to enhance the boiler’s adaptability to fuel;the calculation of the smoke and air duct resistance of the boiler was carried out;after the boiler is designed,processed,installed and after a normal operation for 3 months,the performance of the boiler is tested and verified under the condition that the boiler is designed with fuel and rated load to determine and verify whether the boilers various operating indicators can be achieved the design requirements.Research indicates:(1)The combustion characteristics of biomass forming fuel are obviously superior to biomass bulk materials,and the fuel and combustion characteristics are close to that of lignite,which is suitable for application in layer burning combustion equipment;(2)According to the fuel combustion characteristics,in the furnace design,the front wall is designed as an upright wall without arch;the rear arch is designed to be stepped for heat radiation and reflection;adding an appropriate amount of secondary air to the front wall can improve the airflow field in the furnace,improve the fuel combustion efficiency,and have good fuel adaptability;in the boiler design,after the furnace enters the convection tube bundle,a burnout chamber is arranged,and the three-chamber convection tube bundle is arranged,which can effectively ensure the burmout and improve the heat exchange capacity,and improve the boiler efficiency;(3)It is known from the boiler thermal calculation and optimization of boiler fuel and boiler test verification:the type of fuels with Car≥40%,Oar≥35%,Qnet.ar≥15000 kJ/kg are suitable for this type of boiler;the boiler output is 15t/h,the pressure is 1.25MPa,and the boiler combustion efficiency is up to 97.5%. |
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