Numerical Simulation Of The Internal Pulp Flow Field In Forward Cleaner And The Mechanism Of Structure Optimization

In recent years, with the developing of world economy, the concepts of low-carboneconomy, energy-saving and ejection-decreasing have become the mainstream trend. Recyclingwaste paper not only saves lots of energy, but also lights the environmental pollution. However,as the kinds and contents of impurities in the waste paper pulp become more and more, thequality of pulp and paper is easily affected, along with damaging the devices. So, how toimprove the separation efficiency, and reduce the energy consumption of cleaner is one of themost important problems to be solved in the pulp and paper equipment industry of China, and itwill also promote the paper industry in our country marching toward to a low carbon economicindustry. In the early time, cleaner was researched by the method combining experiments withtheories; however, due to the limitations of experimental conditions, this research methodpresent high cost, and long experimental period.Based on the theory of solid liquid two phase flow, the internal flow field of forwardcleaner was simulated and analyzed by the FLUENT software of CFD technology, and theseparation between fiber and impurities was achieved. After that, the flow characteristics andcollection efficiencies of fiber particles in pulp suspension were in-depth researched. Finally,based on the above research, the different optimization schemes were proposed, and thesimulation results of the different improvement schemes were contrasted and analyzed.The results were as follows:(1) The internal flow field of forward cleaner has complex turbulence; strong vortex;closed cycle flow. And, the turbulence of the internal flow field in forward cleaner isanisotropic. RSM is considered as the most suitable turbulence model for the simulation of theinternal flow field in forward cleaner.(2) According to the distribution characteristic of pressure and velocity in the internal flowfield of forward cleaner, the flow field of forward cleaner has a slightly asymmetric; meanwhile,the internal flow field is mainly composed of two regions: an internal vortex in the centralregion and an external vortex in the outer region.(3) The flow of groups of16impurities with different properties was obtained by thediscrete phase model in FLUENT software. The results show that the separation efficiencies forheavy and light impurities with the particles diameter of0.02mm are all maintained at about50%; and when the particles diameter is close to1mm, the separation efficiencies of theimpurities which the relative densities are greater than or equal to the stone has reached100%.(4) Based on the swelling performance of fiber between dry fiber and wet fiber, andcombined with the concept of spherical fiber particle, the motions of the two kinds of dry fibers with the densities of250kg/m~3and600kg/m~3respectively in pulp are numerical simulated byFLUENT software. The results showed that the collection efficiencies of the two kinds of dryfiber in the internal pulp flow field of forward cleaner were58%and55%respectively.(5) Through comparison and analysis of the internal flow field; wall wear condition; theseparation efficiencies of impurities between the three optimization schemes and the initialmodel. Ultimately make sure the scheme3was the best optimization scheme. Its separationefficiency was higher than the initial model, and the separation efficiencies of some particleswere higher about8%. The average wear rate of scheme3was reduced by1.22e-09than theinitial model.