A Numerical Simulation Study On The Two-stage Pusher Centrifuge Flow Field

The pusher centrifuge is a kind of continuous feeding and pulse dischargehorizontal filtration centrifuge. It has many outstanding advantages, for example,continuous pusher, low power consumption, large production capacity, low productmoisture content and less grain crushing, and has an excellent adaptability to goodfiltering performance grain particles and fibrous material, of which the two-stagepusher centrifuge is the most used model. With the increase of industrial productionscale, the two-stage pusher centrifuge will develop to high-yield, high efficiency, lowenergy consumption in the application, which requires studying the filtration processto guide the engineering application.This paper uses large commercial computational fluid dynamics software FLUENTsetting up a p-100-type two-stage pusher centrifuge three-dimensional computationalmodel. In order to simulate the liquid flow inside the drum and the movement of thefirst-stage drum, the calculation uses the sliding mesh model to simulate the flow intothe two-stage drums and the first-stage drum boundary is simulated used dynamicmesh, while the sieve is simplified as porous media model, through the sievepermeability experiments to get simplified parameters. The RNG k-εturbulencemodel is used in the calculation and liquid-solid two-phase movement simulationadopts Eulerian-Eulerian multiphase flow method. With the established model, thesimulation obtains the fluid flow velocity field, pressure field, turbulence structureand solid content distribution into the two-stage pusher centrifuge drum. Thenumerical simulation results agree well with the theoretical experience andexperimental values, which proves accuracy and feasibility of the model.This paper uses the establishment numerical simulation model to calculate andstudy the influence of the two-stage pusher centrifuge structure parameters (pusherfrequency and screen parameters) and operating conditions (rotate speed and feedingconcentration) on the separation. The results show that, as the pusher frequencyincreases, the cake solids content, the supernatant containing solid rate and initial timeof centrifuge separation to reach stable state become smaller and smaller, while therecovery rate of solid phase and the initial axial coordinate of cake reaching tomaximum solid content increase; with screen slot width increasing, the cake solidscontent and the supernatant containing solid rate become large, while the variation of the recovery rate of solid phase, initial time of centrifuge separation to reach stablestate and the initial axial coordinate of cake reaching to maximum solid content arecontrast; as rotate speed become large, the cake solids content, the supernatantcontaining solid rate and the initial axial coordinate of cake reaching to maximumsolid content will reduce, and the cake solids content increases, while initial time ofcentrifuge separation to reach stable state change has no law; as the inputconcentration become large, initial time of centrifuge separation to reach stable stateand the initial axial coordinate of cake reaching to maximum solid content will reduce,and the change law of the cake solids content, the supernatant containing solid rateand the recovery rate of solid phase is contrast. At the same time, this paper also getsthe minimum drum length in different parameters, when the cake reach the maximumsolid content.This study is the first attempt of numerical simulation of two-stage pushercentrifuge and even filter centrifuge filtration process, and the results provide areference for the filter centrifuge numerical simulation and the structural optimizationdesign, which has a great significance to guide the application of the two-stage pushercentrifuge.