Research And Application Of Particle High-speed Rotating In Hydrocyclone

Physical separation has a prominent advantage in the source management and recycling of pollutants for requiring no chemical addictives and microbial agents.Hydrocyclone is a universally used traditional environmental protection equipment of more than 100 years'history.with technique advantages of compact structure,simple operation and high efficiency.However,the hydrocyclones fail to remove pollutants of ions and molecular state,subjected to the turbulence diffusion.In this paper,the detection systems for high-speed rotating microsphere in the three-dimensional swirling flow field were developed.It has been found that the particles rotate rapidly when they migrate along the helical trajectories in the hydrocyclone,their rotation speed and direction are not consistent with their revolution,their trajectory length is more than an order of magnitude of the normal radius of hydrocyclone.According to the above findings,the separation mechanisms of the oil in porous particles of waste catalysts,the oil-sludge in wastewater of oil shale retorting,and the amine in C4 were revealed.The major achievements are shown as the following:(1)The theoretical prediction model of self-rotation speed and distribution for microspheres in hydrocyclone was established.Firstly,the streamline of flow field of Bloor&Ingham model was modified by considering the influence of the thickness of vortex finder and the cone angle,which makes the modified model suitable for mini-hydrocyclone.Then,a self-rotation prediction model of non-inertial microsphere in hydrocyclone was established based on the velocity field.With this prediction model,the regulation of axial self-rotation for the non-inertial microsphere in a HL/S25 mini-hydrocyclone was studied.The results show thatin the column coordinate system,the self-rotation speed is zero in the forced vortex;The self-rotation speed decreases as the radius of revolution increases in the free vortex,and the self-rotation direction is opposite to the revolution direction;When the microsphere migrates to the boundary layer,its self-rotation speed increases dramatically as it closes to the wall,and the self-rotation direction is also opposite to the revolution direction.When the microsphere is located on the inner side of the locus of zero vertical velocity(LZVV,r/R<0.6),the ratio of self-rotation speed to revolution speed is 0.95 ?z/?a<1,and the ratio increases with the axial height decreases;in contrast,when out of LZVV(r/R>0.6),the ratio is ?z/?a>1,and the ratio increases with the axial height increases.The self-rotation speed in the boundary layer is more than ten times of the revolution speed.In addition,the self-rotation speed is linearly related to the inlet flow rate,and is proportional to the cone angle.(2)The method and device for detecting high-speed self-rotation of microsphere were constructed.The highly monodisperse tracer micro spheres were self-fabricated by the microfluidic technology,which have a transparent shell of 470 ?m and double symmetric spherical cores of 200 ?m.Using two high-speed cameras with orthogonal distribution,a three-dimensional synchronous high-speed motion analyzer(S-HSMA)was constructed to detect the self-rotation of microspheres along their spiral trajectories near the wall of a HL/S25 mini-hydrocyclone.The results show that the microspheres rotate at a high speed near the wall.The speed decreases rapidly as the radius of revolution decreases,and the self-rotation direction is opposite to that of revolution,which is consistent with the theoretical analysis.The conical structure of hydrocyclone helps the microspheres to maintain high-speed self-rotation,the maximum self-rotation speed reaches up to 3000 rad/s at the experiment conditions,which is about half of the theoretical prediction value.In order to investigate the self-rotation of microspheres in the whole swirling flow field,a two-dimensional high-speed motion analyzer(HSMA)was constructed with a single high-speed camera.Combined with particle imaging velocimetry(PIV),the self-rotation of microspheres spirally translating in a cylindrical hydrocyclone of 25 mm in diameter was detected.The results show that the central region of the swirling flow is quasi-forced vortex on the basis of radial distribution of fluid revolution speed,and the self-rotation speed decreases with the increase of radius of revolution.When close to the wall,the self-rotation speed increases rapidly for the strong shear flow in the boundary layer.The self-rotation direction is opposite to that of revolution in the whole field.In addition,the detecting value of self-rotation speed is consistent with the theoretical prediction results in the quasi-free vortex,but the maximum value is also half of the predictedresults near the wall.(3)A numerical simulation method for self-rotation of microspheres translating along spiral trajectories in the hydrocyclone was established.Firstly,this method uses Reynolds stress model(RSM)and discrete phase model(DPM)to simulate the three-dimensional swirling turbulent flow field and the spiral trajectories of microspheres in the mini-hydrocyclone.Then,the self-rotation speed of microspheres along the spiral trajectories is obtained by numerical fitting.The spiral trajectories and self-rotation speed of 470 ?m spherical particles in a solid-liquid mini-hydrocyclone and 10-50 ?m droplets in a HL/L35 liquid-liquid mini-hydrocyclone were predicted and analyzed.The results show that the microsphere with a diameter of 470 ?m rotates at high speed along a spiral trajectory,the residence time is less than 0.3 s,and the trajectory length is 37 times of the normal radius of the mini-hydrocyclone.The self-rotation speed shows fluctuation and decreasing trend along the spiral trajectories.Compared to the experiment results,the error of self-rotation speed is 7.7%-16.1%in the cylindrical section and 16.4%-37.1%in conical section.The droplets with diameters of 30 ?m and 50 ?m also rotate at high speed of more than 10000 rad/s along the spiral trajectories,and the trajectory lengths are over 1000 mm,which is 60 times of the normal radius of the mini-hydrocyclone,helpful to the improvement of the probability of extracting the pollutant particles to the micro-droplets.(4)The mechanism of intensifying separation process by particle high-speed self-rotation in hydrocyclone was revealed.When the particles rotate at high speed near the wall of hydrocyclone,the surface oil is separated by the intensified shear stress,and the pore oil is separated by the intensified fluctuating resultant centrifugal force.The experimental results show that:on the basis of stirring at speed of 300 r/min in the hot water of 95 ? for 30 min,the total oil separation efficiency was raised from 52.44%to 73.44%in less than 1 s by the hydrocyclone with the water of 65 ?.Due to high-speed self-rotation of oil-sludge in the hydrocyclone,the bubbles are isolated from the sludge.The hydrocyclone groups were applied to an 800,000 t/a Fushun oil shale retouch unit for the circulating water purification,the content of oil-sludge was reduced from 416 mg/L to 47.4 mg/L,which ensured the stable operation of the unit.The oil recovery rate increased 5.3%,which is equivalent to a reduction of 230 tons per month of sewage discharge.Based on intensification of mass transfer between the two sides of micro-interface of extractant droplets by their high-speed self-rotation in the hydrocyclone,the hydrocyclone extractor were applied to separate amine in the C4 raw material of a 20,000 t/a methyl tert-butyl ether(MTBE)plant.The extraction water dosage could be decreased from 1800-2000 kg-h-1 to less than 30 kg·h-1,corresponding to a phase ratio reduced from 0.17 to less than 0.01.Furthermore,the operating period could be prolonged by 3 times,and the catalyst consumption could be reduced from 0.94 kg/t to 0.64 kg/t,which is equivalent to a reduction of 32%of solid waste emissions from the source.