Finite Element Simulation And Optimum Design Of Fluid-Solid Coupling Process In Pressure Filtration Of Filter Press

Filter press is a traditional solid-liquid separation equipment,which is widely used in industry.It is constantly optimized with the development of economy and the continuous improvement of environmental protection requirements.However,as the filtration process is airtight and the filter plates is opaque,the slurry flowing status and filter cake formation in filter chamber cannot be directly observed,and the squeezing effect from slurry and filter cake on filter plate are difficult to monitored.Therefore,the design of filter plate and technological parameters in pressure filtration process is mainly dependent on experience now.In this paper,the pressure filtration process of coal slurry in chamber filter press was taken as the research object.The theoretical model for describing press filtration process was built based on Eulerian multiphase theory and user defined function(UDF)technique.The precise geometric model of filter chamber with all features was established and the boundary conditions defined by UDF were coded according to the characteristics of slurry pump.At last,the computational fluid dynamics(CFD)analysis model consisting of reliable theoretical model,precise geometric model and reasonable boundary conditions was built.Then,the ANSYS FLUENT software was applied to simulate the whole pressure filtration process of chamber filter press,and the flowing status of slurry,sedimentary regularity of coal grain,indoor pressure distribution and the correlation among these three factors of the pressure filtration were analyzed.Where after,further analysis by changing the diameter of the coal particle was conducted combined with the Eulerian multiphase flow theory.The result showed that in the first stage of pressure filtration,the coal particles deposited from the bottom to the top and a downward pressure gradient was formed in filter chamber because of the gravity.As the feed pressure was insufficient to make water overcome the drag force to go through the filter cake formed on the inner surface of filter cloth yet,the resistance of the system at this stage mainly came from the resistance of filter cloth to water.In the second stage,the pressure gradient changed to upward as the rheological behavior of coal slurry changed.At this stage,the pressure inside the filter chamber increased continuously and became high enough to overcome the drag force in filter cake,and the filter cake started participating into the filtration process as filter medium.As a result,the feed pressure grew slower than before,and the resistance of the system mainly came from the resistance of filter cloth and cake to water.In the last stage of pressure filtration,the pressure in the filter room increased high enough to overcome the friction between coal particles and push the coal particles to move,and the filtration resistance of the filter cake and cloth decreases as the flow rate decreased.Therefore,flow resistance dominated by interparticle friction became the most important component of the system resistance.Finally,the finite model of filter plate with reasonable boundary conditions was established considering the actual conditions of working state,and the temporal-spatial distribution of pressure field obtained by CFD simulation was extracted and loaded on the filter plate by indirect coupling method.Finite analysis software ABAQUS was used to analyze the stress state of the filter plate under different working conditions and the geometric structure of the filter plate was optimized based on the stress state at the worst condition of filter plate suffering 30%difference of pressure between two sides.The stress became much more balance and the maximum value reduced by 22.85%after the optimization,and the weight reduced by 10.26%,which can bring the enterprise remarkable economic benefits.In conclusion,this paper had established a fluid-solid coupling numerical simulation scheme for the pressure filtration process of chamber filter press based on the reliable theory,accurate geometric model and reasonable boundary conditions.The pressure filtration process was analyzed from multiple angles and the filter plate was optimized reasonably,which provided a certain theoretical basis for the study of the pressure filtration process of the chamber filter press and further optimization design of filter plates.