Research On Mechanical Properties And Technologic Parameters Of Enclosed Biomass Briquetting

The rational use of biomass not only can alleviate the increasingly serious energy crisis,but also can solve the serious environmental pollution problems due to the burning of agricultural and forestry waste in the current rural China.But untreated biomass feedstock is often loose and low in energy density,which limits the transport and storage of biomass energy.The compression of biomass raw materials,not only can solve the above problems,but also can greatly improve the combustion characteristics of biomass raw materials and expand the use of biomass.However,nowadays the biomass compression technology is faced with serious problems including the wear and tear of biomass devices,difficulty in predicting the molding pressure,high energy consumption and poor quality of forming blocks and so on.In view of these problems existing in biomass technology,this paper plans to solve these problems by studying mechanical properties and compression process parameters of biomass.Through the analysis of the mechanical properties of biomass compression,it can provide the theoretical basis for the study of the wear mechanism and the design check of the equipment.By doing research on compression process parameters,we can reduce the energy consumption required in the compression process and improve the molding quality of the molding block contemporarily.The research work done in this paper is as follows:Firstly,due to the existence of viscoelasticity in the process of biomass compression,the compression of biomass is modeled as a simulation model,which is composed of the spring and newton damper.Using the experimental data point fitting method,the viscoelasticity constitutive equation and the relationship between the constitutive model and the actual degree of fitting is proved by the correlation coefficient,which means that the prediction of strain and stress will be reliable.Through the viscoelastic model,we can have a reasonable explanation of how the compression parameters affect the compression process.Secondly,according to the actual situation of the biomass particles in the compression process,the discrete element method is chosen to replace the finite element method to improve the accuracy of the analysis.The contact model and parameters in the discrete element method is derivated and determined.The simulation results of forces shown in the discrete element is mapped to the external devices by the joint simulation of the discrete element software EDEM and the finite element ANSYS,which can turn simulation data into stress distribution on the devices.Finally,the five kinds of forming parameters,such as maximum compression,humidity,mold size,loading speed and maintenance time,which have an impact on the forming progress,are selected as the parameters of the single factor experiment and the orthogonal experiment,respectively.The influence of the compression parameters on the molding was analyzed by the single factor experiment.The most influential molding parameters was found by the variance analysis of the orthogonal experiment.By comparing the maximum compression,forming size and water content,the multi-level orthogonal experiment is carried out,and the least squares support vector machine based on genetic algorithm is used to predict the specific energy consumption and forming density of the molding.The genetic algorithm is used to obtain the most favorable production combination of process parameters.