Simulation Study On Structure And Operation Effect Of Filter On Discharge Line Of Crude Oil Tank

The basket filter is still the dominated filter which is used on export pump in petroleum storage depot.However,the automation of basket filter is low,leading to the increase of labor cost.The scraper self-cleaning filter,a new type of filter,has the advantages of continuous operation during cleaning process and high degree of automation.In this study,the structural design and flow field simulation of a scraper self-cleaning filter are carried out.According to the design specification of the filter for pipeline and pressure vessel,the size of the filter body is designed combining with the oil field data.In order to ensure the continuous contact between the scraper and the mesh,a spring is installed on the scraper.The micro-unit mesh is selected for numerical simulation according to the characteristics of different mesh types.The mesh type is selected according to flow field characteristics.Because of the small thickness of the mesh,the porous medium jump model is used to define the mesh boundary during numerical simulation of filter.The dispersed phase model is used to simulate sludge particles in crude oil due to the small volume fraction of the particles.In order to enable the filter to filter out sludge particles larger than a certain diameter,the mesh boundary of discrete phase is defined.The pressure drop obtained by numerical simulation of the punching mesh and the wedge mesh is compared.The pressure drop of the punching mesh is nearly twice times than that of the wedge mesh,so the wedge mesh is chosen.The residual curve,the inlet and outlet mass flow difference and the outlet pressure monitoring are used as the convergence criterion for the numerical simulation of the filter.Then the rationality of the flow field characteristics in the filter is verified.On this basis,the effects of outlet pipe position,inlet flow rate,mesh number and crude oil viscosity on filter pressure drop are studied.The research results show that the outlet pipe of the filter should be installed at the lowest position,which can avoid excessive sludge particles depositing on the bottom of the casing and blocking the filter mesh from the outside.The inlet mass flow at the condition of the maximum pressure drop is calculated through the relationship between pressure drop and inlet mass flow.The increase of filter mesh has an obvious influence on the increase of pressure loss,which conforms to the exponential law of index 2.4,and should reduce the demand of the mesh size as much as possible.The relationship between the viscosity of crude oil and pressure loss is a power exponential law with an index of 0.8918.This study helps to provide scientific basis for the operation of petroleum storage and transportation,as well as offering practical engineering guidance for separation of sludge particles carried in crude oil.