| This paper studies the influence of the process operation parameters on the filtration and back-washing performance of cylinder-type-filter by using the method of cold-state experiment imitating the filtration condition of slurry oil,it works out why the filtration efficiency is not high through the 3D simulation analysis of the filter's flow field with FLUENT,then the author optimizes the structure of cylinder-type-filter.This paper finds this facts through the cold experimental study.When the viscosity of the slurry is 1.11 cp,it will increase the filtration efficiency of cylinder-type-filter if we improve the flow rate and concentration of the slurry,when the flow rate is 1000L/h and the concentration is 7g/L,the efficiency is highest,but only 77.71%;while the viscosity of the slurry is increased to 1.58 cp,the filtration efficiency will drop to 56.36%,it says that slurry viscosity has significant effects on the filter performance;when the viscosity of the slurry is1.11 cp,the diatomite-3 can improve filtration efficiency of the cylinder-type-filter effectively,the filtration efficiency will be improved to 84.81% when the content of diatomite-3 is 7%,while increasing the slurry viscosity to 1.58 cp at this time,the effect of filter aid become worse,and filtration efficiency drops to 63.13%.This paper finds this facts by back-washing experimental research.If the cylinder's pressure is greater,it means the piston moves faster,the axial shearing action of the filter cake layer will be better,eventually it gets the better cleaning effect;the number of piston stroke is greater means the cleaning piston will shave the filter cake many times in certain back-washing week,and this can improve the washing effect;the short back-washing week will affect the filtration efficiency,conversely the effect time of viscous material on filter is too long,it results in being shoved more difficult,finally it reduces the back-washing effect,and this is not conducive to the regeneration of Johnson screen.Based on the experiment,this paper find this facts by numerical simulation of filter's inner flow field with FLUENT.the velocity and pressure field of cylinder-type-filter distribute symmetrically,the partial penetration will not be increased,and this is an advantage of the filter;the influence of cleaning piston on the flow field distribution has two sides,on the one hand,the rectifying action of this component is beneficial to filter,but when the continuous phase flows through the component,the wake vortex have an disadvantage on the adhesion and bridging of solid particles,this will reduces the effective filter area of John screen,it results that the overall filtration efficiency of cylinder-type-filter is not high;Under the working condition of self-cleaning,the movement of piston will disrupt the natural filtering flow field and generates a large number of vortex,it drives fluid to wash out filtration medium,and this will enhance back-washing effect,if the piston's speed is greater,this additional effect is more significant.It finds this kind of optimized structure-elliptical head+cylindrical baffle,improves more effect of flow field distribution through numerical simulation.In view of the above research,although the filtration efficiency of cylinder-type-filter is not high,it can be used as a primary filter in multistage purification process of slurry oil considering the advantage of self-cleaning online,in order to reduce the content of solids,colloid,and asphaltene in the next process,this will reduce the frequent replacement caused by blocked of the following filter and the production cost and improves production efficiency. |
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