Study on the Performance and Separation Mechanism of Magnetic Swirl Clarifier

Author:Zhang Yu Long

Supervisor:xiao lin jing liu pei kun

Database:Doctor

Degree Year:2018

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Pages:175

Size:12363K

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Aiming at the problems of high suspended solids content,fine particle size,light weight,slow settling speed and large volume of treatment in mine water,this paper uses pipe mixer and magnetic swirl clarifier to deal with mine water.A magnetic swirl clarifier is developed.On the basis of centrifugal force field,gravity field and magnetic field intensification separation,high intensity magnetic floc is obtained,which accelerates settlement separation and improves the efficiency of mine water treatment.It can achieve direct treatment of mine water under mines,and create good economic and environmental benefits.In this paper,the growth,force and motion behavior of magnetic floc in magnetic cyclone clarifier are studied with three measures,which are theoretical analysis,numerical simulation and test test.The influence of the separation performance under the coupling of multi physical field is discussed,the optimum parameters are obtained,and the settlement mechanism of the magnetic cyclone clarifier is clarified,which is of great significance for enriching the theory of separation of rotating flow and the design of the engineering.Firstly,the fluid motion equation in the magnetic swirl clarifier is established by theoretical analysis.Considering the influence of magnetic field and magnetic field on the flocculation effect,the force analysis of the magnetic floc under the compound force field is carried out,and the distribution law of the particle size and velocity of the magnetic floc is obtained.On the basis of the traditional flocculation kinetic equation,the flocculation dynamics mathematical model of the magnetic floc in the magnetic cyclone clarifier is established,and the regular distribution of the particle space at the cone-disc is obtained by the settlement mechanism of the inclined plate,and the theory of flocculation growth and settlement separation of the magnetic floc is perfected.Secondly,according to the mathematical model of the flow field,the flow field is numerically simulated.The influence of inlet velocity,cone-disc parameter and barrel height on velocity,turbulent kinetic energy and turbulent energy dissipation rate in flow field is described.The influence of shear force,centrifugal force and fluid drag force on flocculation settlement under different parameters is analyzed.The settlement separation performance of the magnetic floc can be improved by increasing the inlet speed,increasing the depth and the height of the cylinder and reducing the spacing of the cone,but the effect of the mine water treatment will be reduced when the parameters are too large or too small.The final optimization parameters are:inlet speed 2.31m/s,cone-disc spacing 20mm,insertion depth 400mm,cylinder height 600mm.Thirdly,by establishing the mathematical model of magnetic field in the magnetic swirl clarifier,the distribution rule of magnetic induction intensity is obtained.Combined with the flow field mathematical model,through the flow field module,the magnetic field module and the fluid particle tracking module in the Comsol Multiphysics software,the multi physical field coupling analysis of the particle in the complex force field,such as the flow field,the magnetic field and the gravity field,is carried out.The distribution of particles in the flow field,the size of the force and the number of particles are obtained,and the effect of the cone disk,magnetic field and the magnetic field intensity on the separation efficiency of the particles is also discussed.The results show that when the cone and magnetic field are applied,the particles can be fully subsided with particle size greater than 60μm,which can reduce the number of particles and improve the separation performance.With the increase of magnetic field intensity,the magnetic force along the wall will increase.When the magnetization is up to 200000A/m,the particle sedimentation with grain size greater than 30μm.and the separation performance of magnetic swirl clarifier is further improved.Then,the magnetic flocculation mine water treatment test bed was built and the system test was carried out.The fractal dimension,shear breaking performance and settlement performance of the magnetic floc in different positions in different working conditions were analyzed.The effect of the cone-disc material on the flocculation and separation at the cone-disc was discussed.The influence of the discharge flow of the bottom current on the settlement performance of the overflow and the bottom flow magnetic floc was studied.When the inlet speed is 2.31m/s,the magnetic field size is 0.6A,the silicon cone-disc is used and the underflow flow rate are 300mL/min,the magnetic separator has the best sedimentation and separation performance.Finally,the effects of the operating parameters,such as the processing parameters of magnetic cyclone clarifier,magnetic field strength,inlet velocity and other structural parameters,such as insertion depth,cone-disc spacing and barrel height,have been studied,and the ss removal rate,turbidity removal rate and 8 different particle size variation laws of 3 different sampling points in the magnetic force are studied,and the magnetic swirl clarifier is optimized.The best structural parameters and operating parameters in the cleaner were achieved.When the treatment volume was 0.6m3/h,the ss removal rate was 96.33%,turbidity removal rate was 87.11%,and the particle number was 9908 grain/mL.On the basis of theoretical and experimental research,15m3/h mine water treatment system is designed and developed,and a pilot test of mine water is carried out.The effluent SS is less than 50mg/L,the removal rate of SS reached 90%,the underflow concentration is 80000mg/L.The results of industrial operation show that magnetic swirl clarifier can deal with mine water and achieve recovery of coal slurry.It has guiding significance for the design and simulation amplification of mine water efficient treatment system.