Analysis On Dewatering Principle Of The Vacuum Belt Micro-vibration Mud Screen

The development of the oil industry have caused increasingly serious environmental problems.The drilling fluid brought out from the bottom needs to be dealt with in time,or it will pollute the environment and harm the health of the human and the animals.At present,there are many ways to dispose the drilling waste worldwide,which is accompanied by various treatment equipments.In the view of the shortage of the present equipments,we have brought forward a new treatment device—vacuum belt micro-vibration mud screen,which aimed to replace the existing drilling fluid shale shaker,and achieve the integration of the cutting processing and drilling solid control.The new device will improve the processing efficiency and reduce the cost,and meet the requirement of the reduction,stabilization and harmlessness.The working process of the vacuum belt micro-vibration mud screen can be divided into two stages.During the first stage,the drilling fluid and cuttings enter the device through a distribution box and are distributed evenly on the screen,and then the drilling waste is transported by a rotating drive belt which is driven by a rotating wheel.At the same time,the fluid is vacuumed through the entire area of the screen by a vacuum system.With the influence of the vacuum,the solid is trapped on the screen and form a filter cake layer,the liquid flow into vacuum box through the pore of solid and screen.During the second stage,a small amount of liquid remains in the filter cake.With the suction of the vacuum pump,air will flow through the filter cake and take away a portion of liquid.Finally,the cuttings are separated from the fluid and the cuttings are dried at the same time.This paper have analyzed the structure and the working principle of the vacuum belt micro-vibration mud screen.Besides,the dewatering mechanism under the condition of vacuum is studied with the method of experiment and simulation.The main contents and conclusions are as follows:1、To describe the formation of porous media.Porosity,permeability and tortuosity are the basic parameters of porous media,among which the permeability is the main parameter.2、To discuss the forms of water containing in the porous media and study the effect of vacuum suction on dewatering.Vacuum dewatering mechanism include differential pressure dewatering and air replacement dewatering.The differential pressure dewatering can be regarded as single phase flow in porous media,and air replacement dewatering can be seen as two-phase flow in porous media.Mathematical equations of the mechanism are discussed in the paper.3、Vacuum dewatering experiments are established in laboratory,and the effects of vacuum degrees,particle sizes and thickness of filter cake are analyzed in the differential pressure dewatering experiment.And the effects of sucking rate,particle sizes and filter cake thickness are analyzed in the air replacement dewatering experiment.4、According to experiments,the physical models of vacuum dewatering are established in Fluent.Differential pressure dewatering and air replacement dewatering processes are simulated.Comparing simulation results and experiment results,it is found that the two results are close to each other,and have the same tendency.It turns out that Fluent simulation is feasible,which provides an effective method to analyze vacuum dewatering,and lays the foundation for further research.5、The dewatering model of vacuum belt micro-vibration mud screen is established in Fluent,and processing capacity of the device predicted is 11.9m3/h and the final moisture content of filter cake predicted is 18%.