Based On The Dense Granular Flow Model The Research About The Gas-Liquid-Solid Three Phases Movement In The Decanter Centrifuge

The decanter centrifuge is applied to separate the liquid-solid phase in the industry, whose working principle is that the solid phase is detached from the mixture by the centrifugal force and thrust. With high degree of automation and unattended operation continuous production, this machinery has wide application for the separation process of multiphase flow. However, there is the theoretical demerit of the study on the movement gas-liquid-solid phase movement in the bowl of decanter centrifuge, the theory and knowledge about two phase flow movement in the complex flow field cannot be employed to attack the optimizing operation conditions for the industrial production. Therefore based on the Euler-Euler model’s theory, this manuscript was used to introduce the appropriate the numerical simulation about the decanter centrifuge, which was established in the helical coordinate system, to simulate the movement behavior of three phase system. Under the various operating conditions,the law on the movement for the dense granular flow was studied to build the prediction equation of the moisture content for the product. And then the theoretical foundation that was obtained from the numerical simulation has been employed to be the argument to support the optimizing operating conditions.Based on the granular flow movement theory, this manuscript was used to perfect the kinetics of dense granular flow movement to describe the movement behavior in the decanter centrifuge for solid phase. And it was introduced the new constant into the granular pressure equation; and the collision friction viscosity equation and the equation of motion lag has been added into the granular friction model; while the production due to fluid turbulence or due to collision with molecules was used to close the granular temperature equation. And then the perfect kinetics equation for dense granular flow movement was verified by the accumulation and shear stress movement experiment. And the study of particle mechanics was researched on the base of this theory for the experiments.To solve the problem about that the continuous phase and disperse phase model cannot be employed to simulate the three phase movement in the decanter centrifuge, this manuscript was used to establish the three phase drag force model to simulate the movement on the gas-liquid-solid phase system. On the character of decanter centrifuge’s working principle, the gas and liquid phase can be merged into the theoretical continuous phase. And then, the system of multiphase flow can be simplified to compute the drag force for three phase system: one is the drag force model between the theoretical continuous phase and dispersion phase; and other is the interaction among the continuous phases. Compared with the gas-liquid-solid phase bubbling bed experiment results, this modal can be affirmed to simulate the drag force among the three phase system and achieved a smooth transition with the volume fraction in the simulation. And the study was conducted to analyze the movement relationship for three phases in the simulation.Built on the model of dense granular flow and drag force equation, this manuscript was used to establish the numerical model of the decanter centrifuge in the spiral relative reference frame to study the motion of the bowl and screw when the machine has been working. And then the numerical model was inspected by the experiment of dewatered sewage sludge. This article analyzed the solid phase and liquid phase’s movement mechanism in this machine: because there is the larger friction between the solid phase and centrifuges wall, the shearing action by centrifuge is stronger to push the solid phase; in contrast, the shearing action by the centrifuge was weak for liquid phase. On the base of the numerical simulation’s results, the flow behavior of granular flow and water was studied to obtain relationship between the multiphase flow movement and the centrifugal force in the bowl. The moisture content equation of discharge mass was built to compute the change of moisture content by the various operating conditions.