1、Magnetic field analysis of high gradient magnetic separator via finiteelement analysisS.K.Baik,D.W.Ha,R.K.Ko,J.M.KwonKorea Electrotechnology Research Institute,Seongju-dong 28-1,Changwon,Republic of Koreaa r t i c l ei n f oArticle history:Received 21 March 2011Received in revised form 24 April 2012
2、Accepted 26 April 2012Available online 7 May 2012Keywords:HGMSMatrixMagnetic particlesWastewaterFEMa b s t r a c tHigh Gradient Magnetic Separator(HGMS)uses matrix to make high magnetic field gradient so thatferro-or para-magnetic particles can be attracted to them by high magnetic force.The magneti
3、c forcegenerated by the field gradient is several thousand times larger than that by the magnetic flux densityalone.So the HGMS shows excellent performance compared with other magnetic separators.Thesematrices are usually composed of stainless wires having high magnetization characteristics.This pap
4、erdeals with superconducting HGMS which is aimed for purifying wastewater by using stainless steelmatrix.Background magnetic field up to 6 T is generated by a superconducting solenoid and the stainlesssteel matrices are arranged inside of the solenoid.In order to calculate magnetic forces exerting o
5、n mag-netic particles in wastewater,it is important to calculate magnetic field and magnetic field gradient thoseare proportional to the magnetic force acting on the particle.So we presents magnetic field distributionanalysis result and estimates how many times of magnetic force will act on a partic
6、le when the matrix arearranged or not.Magnetic field is calculated in 3 dimensions by using Finite Element Method(FEM)andalso compared with results obtained from 2 dimensional analysis.?2012 Elsevier B.V.All rights reserved.1.IntroductionPaper factories use a large amount of water and same amount of
7、wastewater is generated.Koreas paper industry is worlds 11thproduction;however,Korea is water shortage nation.So,it isimportant to save water resources and to purify the wastewater.The existing water treatment facilities like precipitation processneed large-scale equipment and wide space to purify t
8、he wastewa-ter of paper factory.High Gradient Magnetic Separation(HGMS)system has the merits to purify wastewater rapidly and to occupysmall space.The wastewater of paper factory contains many kindsof organic components such as pulp,fibroid materials,colorant,cohesion agent and other suspended solid
9、 in high concentration.Because organic components do not have magnetism,it is neces-sary to attach ferromagnetic particles to them,which is calledmagnetic seeding.The formation of magnetic flock with ferromag-netic particles and organic components can purify the wastewaterof paper factory by HGMS.If
10、 the wastewater can be utilized againfor paper manufacturing process after purified by HGMS,it is pos-sible to save energy and solve water shortage problem.The word,High Gradient,means that magnitude of magneticflux density varies so sharply in a space where magnetic separationhappens.The density of
11、 the magnetic energy wmin a linear isotro-pic medium is given by:wm12H!?B!1where H and B are,respectively,the magnitudes of the magneticfield and the magnetic flux density(magnetic induction).It transpires from Eq.(1)that the magnetic energy Umpof a mag-netisable particle of volume Vpplaced in the m
12、agnetic field is:Ump12lpVpH22while the magnetic energy of a fluid of the same volume is given byUmf12lfVpH23In Eqs.(2)and(3),lpandlfare magnetic permeabilities of theparticle and the fluid,respectively.The energy increment U of thesystem(particle+fluid)is given,to first order,as the difference be-tw
13、een the energies given by Eqs.(2)and(3).For weakly magneticparticles this is a good approximation 1.Thus:U 12lf?lpVpH24In general,a force can be expressed as F!m?rU,whereris theoperator of the gradient.Taking into account thatlj=l0(1+kj),where kjis the volume magnetic susceptibility of material j an
14、d0921-4534/$-see front matter?2012 Elsevier B.V.All rights reserved.http:/dx.doi.org/10.1016/j.physc.2012.04.036Corresponding author.E-mail address:skbaikkeri.re.kr(S.K.Baik).Physica C 480(2012)111117Contents lists available at SciVerse ScienceDirectPhysica Cjournal homepage: the magnetic permeabili
15、ty of vacuum,the magnetic force canbe written(in SI units):Fm!12l0kp?kfVprH25In practical situations the magnetic flux density B is frequentlyused,rather than the magnetic field strength H,and Eq.(5)canthen be expressed as:Fm!1l0kp?kfVpBrB6where kpis the volume susceptibility of the particle;kfis th
16、e vol-ume susceptibility of the fluid.As shown in Eq.(6)the magnetic force on a weakly magneticparticle is proportional to the magnitude of magnetic flux densityand the gradient.So we can get higher magnetic separation perfor-mance by increasing the magnetic field and the gradient.The mag-netic field can be increased by using a stronger magnet havingTable 1Typical values of BrB for selected magnetic separators.BB(T2/m)SuspendedmagnetNd drum magneticseparatorNd roll magneticseparatorHGMS with ste
