Influence Of Arch Effect On The Salix Biomass Forming Process

Biomass physical conversion technology,namely solid fuel molding technology,is the focus of current research due to the strong adaptability of raw materials and the convenience of product storage.The solidified biomass fuel is not only convenient for transportation and storage,but also conforms to the clean and sustainable scientific development concept.It will also have an important position in the future energy system,with good development space and high commercial value.According to the constitutive model of Salix granules,the relationship between meso-parameters and macro-parameters is established,the influence of meso-level on macro-factors is studied,and the feasibility of micro-parameters of granular materials to characterize macro-mechanical behavior is explored.Using the average contact force criterion of strong and weak force chains,the distinction between strong and weak force chains is refined,and the influence of the force chain network on the macroscopic level of the entire granular medium system is studied.Through the fish language programming of PFC software,the characteristics of particle flow when the arched structure is formed and collapsed are judged by the connection shape of the force chain,and analyzed by the software.PFC was used to establish a mold with a length-to-diameter ratio of 5:1 and the upper and lower loaded walls.Through the research on the theory of particle arch effect,and with the help of the visual characteristics of load transfer in PFC,the formation of stress arch and its shape change were directly observed.The influence of biomass molding speed and molding particle size on the formation,evolution and shape of the arch structure was qualitatively analyzed,and the influencing factors of stress arch formation were explored.At compression speeds of 0.075 mm·s-1,0.1 mm·s-1,and 0.125 mm·s-1,respectively,the number of particles in the arched structure was 55,60,and 75,respectively.The conversion efficiencies of boundary energy to bonding energy at each compression speed are 87.2%,73.8% and 89.9%,respectively.The strain required to bring the particles into intimate contact differs due to the difference in molding particle size.It can be seen from the stress-strain curves of different molding particle sizes that when the particle size of the raw material is larger,the number of arched structures formed is less,the uniformity of the contact force is worse,and the influence of the arched structure is larger.This result verifies the process of arch formation,collapse and reformation,and obtains the particle flow velocity and energy characteristics due to the arch effect during the process.The particle replacement method is used to simulate the particle breakage during the molding process,and the maximum stress required for molding under different particle breakage degrees is compared.Observing the change of the kinetic energy of the particles during the molding process,each sudden change in kinetic energy indicates that the arched structure has been damaged.The higher the degree of particle fragmentation,the less the arched structure is broken.The characteristics of the force chain network in the uniaxial compression of the granular medium under different crushing conditions are studied,and then compared with the unbroken condition of the particles,and the differences in the results of the strong and weak force chain and stress distribution of the particles are analyzed.