The Study On The Distribution Properties And Movement Of Particles In The Process Of Gas Passing Through Solid-Liquid Two-Phase

The process of bubble passing through the solid-liquid two-phase are widely existed in the chemical,environmental,energy,industrial,petroleum and other fields.In the process,the solid-liquid separation efficiency and equipment parameters are largely determind by the paticle movement and distribution(settlement,suspension,entrainment)under the action of bubble.But the process is an unstable,multi-scale complex multi-phase flow process,the research is very limited about its flow mechanism and particle distribution,so the article takes process of bubble passing through the solid-liquid two-phase as the research object,using numerical simulation to study the movement of bubble passing through the solid-liquid two-phase and the particle distribution.It reveals the flow process and the distribution of particles.By analyzing the movement of single/double bubble and bubble cluster at different particle sizes and their effects on particle movement and distribution,it can deepen the understanding to the distribution characteristics of the gas-liquid-solid three-phase process,and improve and optimize the existing multi-phase flow equipment,and providing a theoretical foundation for the development of new multi-phase flow equipment.In the paper,the CFD-DPTM-VOF three-phase flow model is established.The model combines the Euler and Lagrange method and treats the fluid as a continuous phase.The VOF model is used to track the gas-liquid interface.The dispersed phase particles are regarded as discrete phase.The tracking calculation of paticle uses the discrete particle tracing method(DPTM)to simulate numerically the particle-liquid-gas three-phase flow process of bubble passing through the solid-liquid pool on the platform of Fluent15.0 and Visual Studio2013.In the simulation process,the independence of the grid was verified firstly,and the selected grid size was used to minimize the calculation cost without affecting the calculation accuracy.Then the paper demonstrated the the rationality and correctness of the model.The simulation results are compared with the relevant experimental results of the research group and the experimental results in the literature,and the results and the laws are consistent.The three-phase flow model that has been established and verified is used to study the process of bubble passing through the solid-liquid two-phase,it contains bubble motion and the distribution of particle motion.Firstly,the paper simulated the three-phase flow and particle entrainment process under the action of single/double bubble.The effects of single bubble and double bubble on particle movement distribution and entrainment were compared and analyzed,and the microcosmic motion and distribution law of 5 typical particle sizes such as 5?m,10?m,50?m,100?m and 500?m in the three-phase system were obtained.The results indicate that the vortex zone formed by the rising bubbles produces a suction effect on the four particles of 5?m,10?m,50?m and 100?m,with obvious entrainment phenomenon.With the increase of particle size,the height of entrainment and the number of entrainment particles will decrease.The particle size of 500?m in diameter was more difficult to follow gas,and was not affected by bubble entrainment.Its distribution was mainly concentrated at the bottom of the liquid pool.The particle size of 5?m and 10?m in diameter were basically suspended in the liquid pool,and the concentration distribution along the height of the liquid pool were relatively uniform.Compared with single bubble,double bubble has two entrainment processes with more entrainment particles,and particles can be entrained to a higher height at the same time.The larger the initial diameter of the single/double bubbles,the greater the number of particles.The entrainment of diagonally double bubble is less than the coaxial double bubble.Based on the study of particle entrainment with the action of single/double bubble,the article studies the particle entrainment with the action of bubble cluster further.At different gas velocity,the bubble cluster affect the paticle motion distribution and entrainment in the solid-liquid two-phase liquid pool.By comparing and analyzing the effect of the bottom blowing experiment,the microscopic movement and distribution law of five typical particles of 5?m,10?m,50?m,100?m and 500?m were obtained in the three-phase system.The result of the reseach indicates that,on the condition of bottom-blowing situation,the "dead zone" is the area where the flow does not work almost,it is located at the bottom of the solid-liquid pool,and the area of "dead zone" decteases over time.The more vigorously the solid-liquid pool is stirred.Compared with single/double bubble,the bubble cluster has a stronger entrainment capacity,which has stranger entrainment effect on diameter of 500 ?m particles.As the gas velocity increases,the greater the range of gas-liquid stirring area,the more vigorous the stirring,the more the number of particles entrained by the bubbles,the higher the height of the particles entrained.When the gas velocity is 0.1m/s,most of the entrained particles are near the gas-liquid interface.The spray of droplets also carry out some particles,and the droplets have stronger carrying capacity for 5?m and 10?m,and weaker carrying capacity for 50?m,100?m,and 500?m.Finally,the paper studied the motion distribution of the particles in the solid-liquid suspension with the disturbance of the bubble cluster.By comparing and analyzing the effect of the bottom blowing experiment,the microscopic movement and distribution law of five typical particles of 5?m,10?m,50?m,100?m and 500?m were obtained in the three-phase system.The result of the reseach indicates that,the bubble cluster in the solid-liquid suspension does not affect the distribution of particles with a particle size of 5?m,10?m and 50?m in the height range of 0.02 ~ 0.4m in the liquid pool,but it will affect the movement of the particles.The diameter of 100?m and 500?m particles in the recirculation zone is less than the other three size of particles,and there will be uneven distribution of particle concentration,which is especially obvious for 500?m diameter particle.In addition,the three gas velocity has little effect for the distribution of 50?m diameter particles in the solid-liquid suspension.But it will affect its movement,the greater the gas velocity,the more intense the particle movement.The discovery of the distribution of particles in the suspension under the disturbance of the bubble cluster plays a very important role for guiding the process that requires particles and fluid to contact and react fully in the reactor.