Research On Heat Transfer Properties Of Biomass Briquetting Based On Discrete Element Method

The reserve of fibrous biomass is abundant and the types of bio-based materials are various.However,many fibrous biomass resources are either burned or decomposed,whose energy is not used effectively.Improper handling of biomass resources will not only cause environmental pollution but also cause energy waste.Pulverized and extruded into a bulk fuel,biomass resources can be stored and transported in the form of high-density and small-volume.The energy crisis brought about by the depletion of fossil fuels can also be relieved.The viscosity of lignin at high temperatures makes the effect of temperature on biomass briquettes significant.The researches on heat transfer of briquetting are mostly about the macro analysis of the whole fuel.The heat transfer process is modeled and discussed based on the finite element theory.However,the finite element assumption cannot be applied to the loose state of the biomass at the beginning of briquetting.This article analyzes the heat transfer process of forming based on the discrete element theory from the grain angle.The main research work is as follows:Firstly,considering the plastic deformation during the molding process of the biomass,the contact force between the biomass particles is calculated,and the heat transfer between two biomass particles is modeled and analyzed.A single biomass particle is taken as the research object based on the relevant particle mechanics.The Verlet method is considered to iteratively calculate the heat transfer process.Secondly,the mechanics and heat transfer models are programmed in Visual Studio.The API interface program of the EDEM contact model is developed,and the discrete element numerical simulation of the heat transfer of biomass forming is performed in the EDEM.Hydraulic forming system is established.The temperatures of various parts of the biomass fuel are the measurement index.The discrete element particle model is verified.The ABAQUS FEM macroscopic heat transfer analysis and the EDEM discrete element simulation are compared with the experimental results.Orthogonal experiments are used to analyze the effect of molding process parameters on the temperature of biomass briquettes.Finally,the response surface method is used to design the experiment in Design-Expert.The experimental results are fitted with quadratic polynomials,and the display function expressions of the response variable and compression amount,molding diameter and heating temperature are obtained.Each of the process parameters is optimized so that the overall temperature of the biomass fuel is within the range of softening temperature of the lignin.