Study On Force And Heat Transfer Characteristics Of Hot Pressed Particles Of Begonia Wood Waste

In recent years,the development of new energy to replace fossil fuels has been a concern of the state.Fossil fuel combustion will produce polluting gases,which is non-renewable resources.Biomass energy sources are wide and low-cost.It is a high-quality resource without pollution and renewable.The annual capacity of forestry biomass is about 300 million tons.Among them,Begonia have been planted all over the country because of their wide adaptability to the environment,diverse propagation methods and high survival rate.If the pruning materials of Begonia Garden are collected,treated and processed into high quality biomass solid fuel,the harmless and comprehensive utilization of its waste can be enriched.However,how to find the best parameter ratio and the best molding effect of biomass solid fuel that can be achieved under the lowest energy consumption is a problem that must be solved.This paper studied the hot press forming technology,the principle of transmission and heat transfer characteristics of Begonia material,and carried out the discrete element simulation analysis,which provided the basis for the design of the biomass solid fuel processing technology and equipment.Firstly,the influence of the physical characteristics of solid fuel was analyzed by using Begonia as the research object,and the process parameters were optimized based on satisfaction function algorithm.The principle of force transfer and heat transfer characteristics was studied.The discrete element software EDEM was selected to perfect the relevant heat transfer model theory,the corresponding API was written,the parameters required for simulation were calibrated,the simulation results were studied,and the general rules of the micro particle change in biomass block forming were obtained.Finally,the necessity of optimization of process parameters and the reliability of simulation results were verified by deformation,temperature and electron microscope.The main research contents and results are as follows:（1）The parameters of the hot press molding technology of Begonia forest waste were optimized.The results show that the particle size,moisture content,temperature and pressure all have significant influence on the density,durability and physical properties of the crushing resistance of the block.When the particle size is less than 0.16 mm,the durability and density of the molding material are the highest,and the molding effect of other particle sizes has little difference;the moisture content increases,and the density of the material block is generally decreasing,the durability and the crashworthiness increase gradually and then stabilize;the physical properties of solid fuel increase with the increase of temperature,and finally tend to be stable;the higher the pressure,the better the quality of the molding block.According to the test data,the optimum range of factors was determined.The response surface test with three factors（water content,temperature and pressure）was designed.The variance analysis results are significant.The response surface data was optimized according to satisfaction function method,and the optimal parameter combination was obtained.The temperature,water content and pressure of Begonia are 127.6 ℃,5%,128.32 MPa,under the combination of parameters,the corresponding density,durability and crashworthiness of the test are 1.056g/cm^-3,99.95% and 99.98%.（2）The characteristics of the transfer of force and heat transfer between the particles in biomass forming were studied.The soft ball model and the crystal spring contact model were selected by using the EDEM discrete element software.The heat transfer mechanism between particles was studied,the relevant heat transfer model theory was improved,and the corresponding API was written through the secondary development interface.The model of EDEM particles of Begonia biomass was constructed.The contact parameters of the particles and the mold needed for the simulation operation were calibrated by the method of experiment and simulation.Finally,the recovery coefficient,static friction coefficient and dynamic friction coefficient between the particles of the raw materials and the mold were finally calibrated as 0.613,0.588 and 0.091.The recovery coefficient,static friction coefficient and dynamic friction coefficient between the biomass particles were calibrated.The coefficients are 0.467,0.515 and 0.118 to reduce unnecessary errors and make the simulation results more realistic.（3）The simulation results of the simulation of the thermal pressing of EDEM biomass were carried out.The results show that the displacement of particles in the mold is gradually consistent,and the whole is disordered without the particles in the upper and lower layers,and the contact force suddenly increases in the range of 0.4-0.6.The heat transfer of the block forming is closely related to the compression degree.The heat transfer rate of the raw material is very slow.Under the pressure of 90 MPa,the internal pressure of the two minutes multi pressing block can reach the specified temperature.The heat transfer time of different temperature is the same,the larger the particle size is,the faster the heat transfer is,the less the heat transfer time of the raw material block is than the heating time.Therefore,it is very reasonable to keep pressure for3 minutes under 90 MPa pressure.After demolding,it can be placed in plastic bag with good sealing property after 2 minutes.（4）The hot pressing and simulation tests of solid fuel of Begonia were tested and verified.The results of the simulation show that the stress-strain and temperature change are basically the same,which proves the rationality of the discrete element software EDEM and the compilation API.The micro electron microscope test of forming block explains the rationality of the selection of four factors（particle size,moisture content,temperature and pressure）from the micro point of view,verifies the reasons for the macro physical properties produced at different levels,and further verifies the rationality of the design of the simulation parameters of EDEM.The above research is based on the research on the forming process parameters,the inter particle transmission and heat transfer characteristics of the solid fuel of Begonia.The hot press forming mechanism of biomass solid fuel is studied from the micro point of view,which provides a reference for the production process and equipment design of biomass solid fuel.