Design And Simulation Of A Biomass Pellet Burner

Environment and energy have become the two major concerns of the world.Traditional fossil energy will be gradually eliminated due to its non-renewable and environmental pollution.People pay more and more attention to biomass energy,which is a new efficient and clean energy.In order to solve the resource waste and environmental pollution caused by on-site incineration of agricultural and forestry waste,a large amount of agricultural and forestry waste in China is processed into biomass pellets fuel which is convenient for transportation and storage every year,and supplied to various biomass combustion equipment.In order to meet the market demand of small-scale biomass boiler industry in China,a biomass particle burner with power of 50kW is designed in this paper.The combustion and structural characteristics of the burner are studied by numerical simulation technology,and technical reference is provided for late test and optimization process of the burner.1)Analysis of combustion characteristics of biomass pellet fuel.Firstly,taking two typical biomass pellet fuels as examples,the basic physical and chemical properties of biomass pellet fuels were analyzed.Secondly,a brief description was given of the combustion process and characteristics of original biomass fuels and biomass pellet fuels,which provided a reference and basis for the development of biomass pellet fuel dedicated burners.2)Structure design of biomass particle burner and analysis of key parameters.The main body of the biomass particle burner is a double-layer combustion cylinder structure,the feed roller and the combustion roller are combined,and the motor drives the two to rotate through the sprocket to meet the feed demand and turn the fuel at the same time to reduce the phenomenon of slagging and caking in the combustion process.The combustion cylinder adopts the secondary air intake mode to strengthen the airflow disturbance in the cylinder and improve the fuel combustion efficiency.Through theoretical analysis and simulation,it is determined that the rotation speed of the combustion cylinder to achieve the best flipping effect is 44r/min.Finally,according to the rotation speed range of the drum and fuel demand,the selection of the transmission system and fan is calculated.3)According to the structural characteristics of the biomass particle burner,in order to take into account the interaction between the fluid domain and the solid domain,the numerical simulation technology combined with the fluid-heat-solid coupling method was used to establish the simulation system of the combustion and structural characteristics of the burner,and the multi-field coupling analysis of the burner was realized.4)The simulation results of the combustion characteristics of the burner under different operating conditions indicate that a large excess air coefficient is not suitable for biological particle burners.When the excess air coefficient is 1.2,the average temperature and thermal efficiency of the outlet reach the highest,and the emission of flue gas pollutants is relatively small,resulting in better combustion effects;The simulation results of the structural characteristics of key structures under different working conditions show that the distribution of thermal stress and strain on the drum as a whole is highly consistent with the temperature load.Under different hightemperature loads under different working conditions,the maximum stress value is less than 3 times the allowable stress of the material at working temperature,meeting the strength evaluation conditions of relevant standards,indicating that the structural design is reasonable.However,in response to the phenomenon of flame sticking to the wall at the drum outlet,Necessary optimization processing needs to be carried out in the later stage for this part.