Research On The Screening Mechanism Of Negative Pressure Vibrating Screen

Drilling fluid vibrating screen as the most critical first-stage drilling fluid purification equipment,the main function is to conduct solid-liquid separation,recovery as much as possible drilling fluid and screening cuttings.Therefore,the handling capacity under different screen mesh is one of the main criteria to measure the quality of the vibrating screen.With the development of the petroleum industry,the higher and higher requirements are requested in variety,specification and quality of vibrating screen.Drilling fluid vibrating screen began to develop to high mesh,large handling capacity,intelligent,composite separation and other directions.The negative pressure vibrating screen studied in this paper is a kind of solid-liquid separation equipment based on vibration separation and vacuum filtration composite separation.For the new type of drilling fluid vibrating screen,there is no theory and experimental study on the mechanism of composite separation.So this paper made a series of researches on theoretical analysis,computer simulation and experimental verification.The main works were as follows:(1)Solid-phase conveyance on drilling fluid vibrating screen surface having a significant impact on its handling capacity.According to the basic principle of vibration sieve kinetics,the dynamics of solid particles on the screen in submerged and non-submerged state were analyzed,the conveyance rule of solid particles on the screen was studied,and the motion equations of solid particles were established.Through it,the conditions of throwing movement and sliding about solid particles on negative pressure vibration screen can be got.Besides,Under the same conditions,the transport speed of solid particles on the negative pressure shaker and the conventional drilling fluid shaker was compared.(2)Considering the influence of relative parameters on the conveyance of solid particles,the motion model of solid particles on the negative pressure vibrating screen was established.Through EDEM-FLUENT coupling simulation,the conveyance velocity of solid particles with different diameter was obtained and compared with the theoretical calculation results to verify the correctness of the simulation results.Then the influence of different kinetic parameters of vibrating screen on the conveyance of solid particles was analyzed by using coupled simulation.And when design negative pressure vibrating screen,the result can provide the basis for the determination of dynamic parameters.(3)Based on the fundamentals of Fluid Mechanics,the movement of drilling fluid on the surface of the negative pressure vibrating screen was analyzed.So the equations of motion and continuity of the drilling fluid along the screen surface were established.Then the mathematical model was numerically solved.(4)Fluid simulation calculation model was established.Then by using the finite element software FLUENT,the handling capacity about negative pressure vibrating screen and traditional vibrating screen can be carried out.Comparing the result showed the advance of negative pressure vibrating screen.Using the simulation model,the flow velocity and the sieve speed of the drilling fluid were obtained.and the rheological parameters(viscosity and density)of the drilling fluid and the dynamic parameters of the negative pressure vibrating screen have effect on handling capacity and the movement of drilling fluid.Analyzing the effect can provide a theoretical basis for the field work of negative pressure vibrating screen.(5)According to the simulation model,a negative pressure vibrating screen prototype was designed.Firstly,the reliability test was performed to determine the operability of the prototype.And then made industrial test to verify the accuracy of the simulation results.