[1]Patented Oct. 119 1938 2@132,404 UNITED STATES PATENT OFFICE 2,132,404 METHOD OF SEPARATING NAGNETI[C MATERIAL Reginald S. Dean, Washington, D. C., and Charles W. Davis, Pittsburgh, Pa. No Drawing. AppReation February 17, 1934, Serial No. 711,820 18 Claims. (Cl. 209-214) Our invention relates to material treatment and the material treated. It relates more In particular to the treatment of 9, material such as an ore or the like by a process involving magnetic separ,%tion to concentrate a portion of such material. For convenience, our Invention will be described In connection with the separation of dif ferent constituents of ores and the like, and lo modificationi and details of, the process and products involved will then be disclosed. In considering the Invention from the standpoint of mineral separation, It is to bp noted that substantially a]I magnetic separation employed fiere15 tofore has depended primarily upon the utilization of the characteristic of magnetizable materials known as permeability. Separations that depend for their results on permeability of materials or differences of permeability are neces20 sarily limited in their applications. The principal object of our present invention Is the utilization of a characteristic of material not heretofore employed in separation processes. Another object is the provision of means for 25 developing modifled magnetic characteristics of materials which will permit their ready separation by subsequent treatment. Another object is to utilize differences in coercive force of materials to effect a separation 3( of such materials. Another object is the provision of a method for mgdifying the coercive force of materials; Another object Js the production of material having high coercive force. 35 Another object is the provision of Improved means for employing magnetic properties In removing Impurities from materials such as ores or minerais. Heretofore all commercial methods for sepa4o rating minerals have employed direct current magnets or have employed magnets in such a way as to utilize the magnetic permeability of the material to be separated. This is a specific measurable magnetic property usually repre45 sented by the symbol u. For example, the attraction of the mineral particle In air for a magnet has been deterniined to be proportional to the quantity /A minus one. The complete magnetic nature of a substance, 50 however, is not expressed by its permeability. The degree and tenacity with @rhich its magnetism is retained after a magnetizing field is removed are also Important. These properties are proportional to characteristics of magnetiz55 able materials termed "remanencell and "coereive force". Our invention is directed to the development of a suitable remanence and coereive force in materials and the utilization of these factors In magnetic separation processes. For further explanation of the character of 5 remanence and coercive force as t a our invention, we wish to re'mind those skine in the art that the tenacity with which a material retains its magnetism Is often expressed by the socalled hysteresis loop which shows the magnetic 10 Induction resulting from increasing and decreasing a magnetizing fleld cyclically. For convenience, the general conflguration of the hysteresis loop is expressed In terms of intercepts on the axes. The induction remaining when the 15 fleld is reduced to zero Is called the remanence, and the fleld which would be necessary to neutrelize this induction Is termed the coercive force of a particular material. The tenacity with which magnetism is retained is according- 20 ly determined by the coercive force, and the strength of the remanent magnetism by the remanence. Since in small particles the demagnetizing factor is very great, we are in the present invention more concerned with the con- 25 trol of coercive force than with the remanence. An important aspect of our invention is the d-iscovery that the coercive force of minerals varies widely and is particularly susceptible to change by suitable heat treatment. We have also found that this coercive force may be utilized In a number of ways to effect separations of two or more materials which were not readily separable prior to our invention. In a Iarge class of substances, the coercive force deveioped or in- 35 creased therein in accordance with our Invention permits the formation of small permanent magnets and the iesulting permanent magnetism can be used to advantage in separation processes. We have found further that these properties are associated with activity in an alternating mag- 40 netic fleld In such a way that strongly active materials have a high C-oercive force and, as a rule, considerable remanence. This activity in an alternating current field manifests f by a behavior which may be termed "ju ". 45 The individual active particles, for example, if supporte d on a plane surface and nto the fleld of an alternating@ magnet will jump and vibrate on the plane surface gt a relatively Iiigh rate which in many cases is comparable tG the 50 rate of change of the polarity of the magnet. We conceive that this property which we term "activity" may be due to the alternate repelling and attracting action of the alternating mag- 66
[2]2,182,404 netic field. We have found, as wtH be shown further hereinafter, that if the alternatin$: magnetle fleld is too intense, activity will be cut down. This we ronceive to be due to a partial demagnetization: of the individual magnet particles. The first step in our process corisists in providing suitable coercive force and remanence In the niaterials to be treated. We have found that 10 we may divide most minerals, for example, into a number of classes and in general each class is su.gceptible to treatment by a uniform process to develop high coercive force. Although all of the members of a, single class may be capable of treat.15 ment by substantially the same process to develop high coercive force and remanence, the duration and control of the treatment and the nature of the mineral itself may be employed to produce a :ftnal result in which all of the members of a single 20 class may be made to differ In coercive force. The result is that we may treat a nAxture of minerals which may be minerals of different classes or minerals of the same class to develop a differential in coercive force and remanence and 26 make It possible to secure a separation. For purposes of explanatiori, minerals containing iron, nickel, manganese and/or cobalt niay be considered to represent the minerals wliich can be,@,' separated or concentrated by our process. It may 30 be stated, however, that it is inunaterial whether the Iron, nickel, or cobalt are present as normal constituents of the minerals or as impurities. Mnerals of this class often contain iron, nickel or cobalt in combination with other metallic eles5 ments. We have found that when the other metallic element present has an atoniic weight greater than 40, the mineral may be treated to obtain a high coercive force, whjle minerals witb associated elements which have an atomic weight 40 below 40 do not become highly coercive by the same treatment. For our purpose, we may classify minerals as fonows: Class A 45 Materials naturally possessing high coercive force and remanence (and their artifleial analogues) Lodestone (roasted Iron oxides) Pyrrhotite (roasted iron or copper pyrites) 1;0 Class B Materials naturally possessing high coercive force but low remanence Hematite Chromite 55 Mica Class I Metals, alloys, sulphides, arsenides and antimonides Pyrite, FeS2 60 Mareasite, F'eS2 Sternbergite, A92SFt4S5 Mllerite, NiS NiecoUte, NiAs Breithauptite, NiSb 6.5 PY'lThotite, SesSs+l Troilite, F%S PolYdYmite, Ni4S5 Bomite, Cu3FeS3 Chaleopyrite, CUPeS2 70 Arsenoferrite, FeAS2 Marmatite, (Fe, Zn) S Molybdenite, (Fe present) r,eueopyrite, PeAS2 Arsenopyrite FeS2PeAS2 75 Safflorite, CoAS2 Rammelsbergite, NW2 MetalRe irori Heusler's alloys Powdered nickel-iron alloy (78% nickel) Cobalt nickel pyrite Smaltite, CoAs2 Cobaltite, CoAs2 Gersdorfftte, NiAsS Corynite, NiS2.Ni(AsSb)2 Ulhnannite, NiS2.NiSb2 10 Pentlandite, (PeNi) S Chalmersite, CU2SPe4S5 Mllingite, FeAS2 Glaucadot, (Co, Fe)AsS Stannite, SnS2.Cu2S.FeS 15 Ptankeite, Pb5Sn2Sb2SI2(Fe present) Class IX Oxides of the general formula R203 Hematite, Pe2o3 lamenite, (PETI) 203 20 Heterogenite, Coo.Co2o36H20 Psilomelane, H4MnO5(Fe2O3) Diaspore group Gothite, Fe2O3I-I20 umonite, 2Fe2o33H20 25 Turgite, 2Fe2O3H2O Martite, Fe2O3 (isometric) Pyrolusite, MnO2 (Pe2O3) Xanthosiderite, Pe2o3.2H20 30 Skemmatite, 3M-no2.2Pe2O3.6H20 Class 3][I Aluminates, ferrites, carbonates, tungstates, columbates and tantalates Hercynite, FeOA1203 35 Dysluite, (Zn, Fe, Mn)0. (Al, Fe) 203 Magnetite, Peo, Fe2O3 Ferrozincite, Zno.Pe2O3 Ferrozincite, (ZnO.Fe2O3) Franklinite, (Fe, Zn, Mn)O.(Fle, Mn)203 40 Copper ferrite, CuO.Fe2O3 Jacobsite, (Mn, Mg)o.(Fle, Mn)203 Chromite, PeOCr2O3 (FemG) 0. (Cr, Fe) 203 Pseudo Brookite, Fle4('nO4)3 45 Tantalate Niobate Tungstate group Colurnbite-Tantalite, FeO.(TaCb)205 Samarskite, 3FeOCe2(NbTa)60ia Wolframite, (FeMn)O.WO3 Ferberite, PeO.WO3 50 Molybdite, 3MoO3.F@e2O3.71/2H20 Hubnerite, MnO.WO3 Siderite, FeOC02 Oligonite, (F@eOAln) O.CO2 Phodochrosite, MnCO3 55 Class rv, Silicates Pyroxene group Bronzite, (MgFe) SiO3 Hypersthene, (FeMg) SiO3 60 Augite, (Ca, Mg, Fe) (SiO3) 2 Aegirite, NAPE (SiO3) 2 Rhodonite, (Mn, Zn, Fe, Cu) Sio3 Amphibole group AnthophylUte, (MgFe) sio3 Actinolite, Ca.(MgFe) 3 (SiO3) 4 Hornblende, Ca (MgFe) 3 (SiO3) 4 Glaueophane, NaAl (SiO3) 2. (Fe, Mg) SiO3 Iolite, H2(Mg, Fe) AI&SilOO37 Gamet group 7( Garn6t, FeW2 (8104) 3 Chrysolite group Chrysolite, (Mg, Fe)2SiO4 Mea group 1310tite, (HK)2(MgFe)2(AMe)2(SiO4)3 71
[3]2,132,404 3 Any of the materials set Gut hereinabgve may be treated by our process, as will appear'clear hereinafter. Other materials not specifically Hsted may also be treated, usually by means of a first step involving the introduction of a magnetizable material not normally present In the substance. In our process, as in all processes Involving separation, the materials are :ftrst treated to form relatively small particles. Usually io In the case of minerals, preliminary metallurgical treatment will have required the formation of small particles, and so our process does not, as a rule, involve additional grinding. , We may treat finely divided ores or minerals ground In any of 15 the usual ways. We flnd, however, that exceptionally good results are in most cases obtainable when the material has pre@iously been broken down by an explosion shattering process, as described In the co-pending application of Dean 2o and GrGss, Serial No. 612,524 flled May 20 1932. In developing high coercive force in m;ierials, we have proceeded on the conception that this high coercive force is associated with the dispersion in one substance of a second phase In a 25 very finely divided state. This second phase must be that state which exists at the grain boundaries in multierystalline solids or discontinuities in the crystal lattice or metallic structure. Either the matrix or the dispersed phase, or both, may 3o be magnetic. The treatments which we employ to control coercive force are essentially treatments to control the dispersion of constituents of the minerai or the like. For the purpose of description, our method may 35 be classifled according to two general steps of treatment. They are as follows: A. Formation at a temperature below that of substantial crystal growth of a solid. B. Treatment which Involves first forming a solid solution and then dispersion of one of the 40 constituents of the solid solution in flnely divided state in the other. This latter treatment may be considered as involving four steps as follows: 46 1. Heating to form a solid solution; 2. Quenching to- obtain a supersaturated solid solution; 3. Aging to allow the supersaturated solution to obtain a more stable state and resulting In 50 the separation of a finely dispersed phase; and 4. Annealing to agglomerate a dispersed phase. The point In this latter method where the process is stopped depends upon the result desired. 5r, After step 2, the coercive force is low; after step 3, the coercive force is high; and after step 4, again Iow. To apply the first mentioned method (designated A), a suitable heat treatment is most com60 monly used. In soine cases, the mineral or the like may be treated directly by heating In one or more steps and with suitable control of the furnace atmosphere where this is required. In other cases, a preliminary treatment Is required to form 65 a solid capable of decomposition at a temperature below that of substantially crystal growth. As an example of.the second mentioned method (designated B), a mixture of hematite and magnetite has been "homogenized" by heating for one To hour 1450' C. The mixture was then quenched In cold water thereby producing a solid solution In a metastable condition. Subsequent aging In vacuo for thirty minutes at any temperature between 5000 C. and 1000' C. produced a substan7o tiauy, four-fold increase in coercive force. Another example involved the treatment of basic open hearth slags which, in a quenched condition, have a low coercive force and apparently contain metastable soud solutions. Aging for one hour at 600' C. caused a substantial increase In coercive 5 force. In order to avoid an extremely long and detailed description of details of treatment, we give below a table showing the application of various heat treatments to different minerals and the 10 like. and the resultant activity In both a direct and alternating fleld, the latter being produced by a single phase, 60 cycle, alternating current and a laminated core electromagnet having a field strength of about 50 gauss. Activity may be considered@ as a direct Indication of coercive force and remanent magnetism. The data given In the table will be discussed hereinafter' Referring to the table, it Is at once evident that niinerals of Class A usually require no treatment- 20 They have been known to possess permanent magnetism and we claim no hee@t treatment or separating process as applied directly to these materials except as included in the appended claims. Insofar as we may separate these ma- 25 terials from other magnetic materials, or insofar as we may employ a different method of separation, my invention applies to them. In this connection we are fanifliar with British Patent No. 224,924 to Mordey, as well as other patents and 30 literature references relating to the Mordey development. In this connection, we wish to state that we employ an entirely different mechanism, as further details of this speeification will show. Minerals of Class B likewise reqwre no treat- 35 ment, but on account of their very low remanence, require high flelds to obtain the advantage of their high coercive force. By treating these minerals in accordance with our invention, however, the use of lower fleld strengths Is perniitted 40 Referring further to the table, it will be seen that in Classes I and II, heating pjroduces at once a high remanence and coercive force material, according to our method A. Control of temperature and atmosphere can be employed further to 45 modify coercive force In different minerals of the same class. In the case of minerals of Class M, it Is necessary first to produce a solid, capable of partial decomposition below the temperature of crystal 50 growth, e. g., by oxidizing the niineral or by drivIng Off C02. We then produce a dispersion and a resultant magnetic substance having high coercive force by partial reduction according to method A. This treatment likewise renders 5ra these minerals of higher permeability a'nd may be used to make possible their separation by wellknown direct current methods. Mn erals of Class IV are characterized by requiring repeated and drastic treatments to 60 secure high coercive force. In this class of niaterials, we may, for examp!e, employ the heating, quenching and aging steps. From the appended table and the disclosure - hereinabove, methods of treatment for separating 65 different minerais may be readily determined. We shall give hereinbelow a number of examples showing the application of my invention to different minerals and the like. Example 1 70 In the treatment of chromite to secure Mgh coercive force In accordance with the general treatmen t A previousl discussed, we heat the ore .Y or mixture of minerals which may have resulted 75
[4]4 2,132, 404 Mineral Heat treatment Test Notes No. Class Designation Stop Temper' Time Atmo sphere Method of ature, 10. cooling ------ Sponge iron ----------- Reduced ir, H2 ------------ Single --- 650 ---------- 5 min ------- Air -------------- Air. 2------------ Iroii-silicon fllings ----- Anne,,iled ----------------- --- do ----- 950 --------- - 10 min ------ ----- do ----------- Do. 3------------ Iro.n-cobalt (large Nothardened ------------- Three --- 850 ----- ----- -------------- ----- do ----------- Do. P"(!@ 4------------ P",.",floy d.@t ------- ---------------------------- Single --- 050 ---------- 10 min ------ ----- do ----------- Do. 6 Irozi ------------------- Nitrided ------------------ Two ---- - ------------ 4 hrs - ------- N113 -------- --- NHi. 6 Troilite --------------- FeS ----------------------- Single --- ;,90 ---------- 5 min ------- Air--. ----------- Air. 7------------ Pyrite ----------------- FeS2 ---------------------- --- do ----- 6,50 ---------- 5 min ------- ----- do ----------- Do. 8------------ Marc-,isite ------------- FeS ----------------------- --- do ----- 650 ---------- 5 rnin ------- ---- do ----------- Do. 9_@ ---------- Pyrrhotite ------------ Fe3S4 ---------------------- --- do --- 650 ------ ---- 5 min ------- ----- do ----------- Do. to------ Chaleopyrite ---------- CuFeS2 ------------------- --- do ----- 600 ---------- 1 min--. ---- ----- do@ ---------- Do. ------ ----- do --------- ------- - --------------------------- --- do ----- 600@ --------- 2 min ------- ----- ----------- Do. ------ ----- do ----------------- - --------------------------- --- do ----- 600 --------- - 5 min ------- ----- o ----------- Do. t3 ----------- ----- do ----------------- ---------------------------- --- do ----- 600 ---------- I hr --------- ----- do ----------- Do. 14 -------- -- ----- do ----------------- --------------------- ------ --- do ----- 950 ---------- 10 min ------ ----- do ----------- Do. 15 ---- T------ ----- do ----------------- --------------------------- --- do ----- 950 ------ ---- 1 hr --------- ----- do ----------- Do. 16 ----------- Bornite- .----- ------- Cu5FeS, ------------------- --- do ----- 600 --------- - 5 min- .----- ----- do ----------- Do. 17 ---------- Pentlandite --- ------- (FeNi)S ------------------- --- do ----- 600 --------- - 6 min ------- ----- do ----------- Do. 18 ----------- Arsenopyrite ---------- FeAsS -------------------- --- do ----- 600 ------ ---- 5 min ------- ----- do ----------- Do. I------ Molybdenite ---------- MoS2(some Fe) ----------- --- do ----- 600 ---------- 5-15 min ---- ----- do ----------- Do. 20 ----------- ----- do--. -------------- ---------------------------- --- do----- 750 ---------- 2 min ------- ----- do ----------- Do. 21 ----- 11 ----- Hematite ------------- FC203 --------------------- --- do ----- 5W ------ ---- 30 min ------ H2 -------------- Furnace. 22 ----- II ----- Hematite+SPOngG ---------------------------- --- do ----- 650 ---------- 5 min -------- Closederucible --- ------------ iron. 23 ----- II ----- Martite --------------- Fe2O3 (isomet.) ------------ --- do ----- 500 -- ---- --- 30 min ------ H2 -------------- Furnace. 24 ----- II ----- I,imonite -------------- 2Fe2O3.3H20 -------------- --- do ----- 500 ---------- 30 min ------ H2 -------------- Do. 25 ---- IT ----- Gothite --------------- Fe2O3.H20 ---------------- --- do ----- 500 ------- --- 30 min ------ E2 -------------- Do. 26----- II ----- Ttirgite ---------- ---- 2Fe2O3.H20 --------------- --- do ----- 500 ---------- 30 min-. ---- H2 -------------- Do. 27 ----- IT ----- Ilmenite -------------- (FeTi)203 ----------------- --- do ----- 600 --- ------- 15 min ------ Air -------------- Air. 11 ----- ----- do ----------------- --- ------------------------- --- do----- 500 ------ ---- 30 min ------ H2 -------------- Furnace. II ----- Psilomelftne ----------- R4MnOb ------------------ --- do ----- 500 ---------- 30 Min@ ----- H2 -------------- Do. 30 ----- Pyrolusite ------------- @'MnO2 --------------------- --- do ----- '@00 -- ---- --- 30 rrin ------ H2 -------------- Do. 31_____ III ---- Lodestoiie ------------- ---------------------------- ---------- @370 - --------- 5 hrs -------- Air -------------- Air. 32----- III ---- ----- do -- --------------- FeO.Fe2O3 ---------------- ---------- l@00 - -------- I hr --------- V.cu - -------- ------------ 33 ----- III ---- ----- do -- --------------- ---------------------------- ---------- - A+B 950 --- 5 hrs -------- Air ----- -------- Air. @50 0 - --- 30 min - ----- H2 ------ ------ -- Furn ace. 34 ----- III ---- Fe3Oi ----------------- Hayden artificial, high Single --- 950 --------- - I min ------- Air -------------- Air. purity, low coercive force. III ---- Fe3O4 ----------------- --- ------------------------- --- do ----- 950 ---------- 6 min ------- ----- do ----------- Air. 36 ----- III ---- Fe3O ------------------ ---------------------------- --- do ----- 950 ----- ----- 30 min ------ ----- do ----------- Do. 37 ----- III ---- Magnetite ------------- FeO.Fe2O3 (low coercive --- do----- 950 ---------- 10 min ------ ----- do ----------- Do. force). 38 ----- III ---- ----- do -- --------------- ---------------------------- --- do ----- 950 --- -------- 10 min ------ ----- do ----------- Water, 39 ----- III ---- ----- do -- --------------- ---------------------------- --- do ----- Oi 0---------- 2 hrs -------- ----- do ----------- Air. 40 ---- III ---- ----- do -- --------------- ------------------------- d 950 ---------- 2y2 hrs ------ ----- do ----------- Furnace. 41 ------ III ---- ----- do -- --------------- -------------------- ---- ::: :::doo--::: 500 --------- - IY4 hrs ------H --------------- Do. 42 ----- III ---- ----- do --------------- Ox.+red ------------ ------ ---------- A-i-B 950 ---- 10 min ----- . Air -------------- Air. 1500 ---- 30 min ------ Ili ------------ -- Furnace. 43 ----- III ---- Magnesio-ferrite ------- Y-gO.F6203 --------------- Single --- 950 ---------- ]Omin ------ Air ----------- Air. 44 ----- III@ --- Ferberite. ------------- ---------------------------- ---------- 050 ------ ---- 10 min ------ ----- do ----------- Do. 45 ----- III ---- ----- do -- --------------- ---------------------------- ---------- 9,50 ----- ----- 45 min ------ ----- do ----------- Do. 46 ----- I I---- d,) ----------------- F,,O,WO ------------------ ---------- fQ5O ------ ---- 45 miri. ----- -----d------------ DI). ' 500 ---------- 30 rnin. ----- H2 -------------- Furnac(3. 47 ----- III ---- ----- do ----------------- ---------------------------- ---------- 500 ---------- 45 min ------ H2 -------------- Do. 49 ----- III ---- ----- do -- --------------- ---------------------------- ---------- -100 - --------- 2 hrs -------- H2 -------------- Do. 49 ----- III ---- Chromite ------------- ------------------ 95C 10 min Air -------------- Air. 50 ----- III ---- do-@ ------ --------- FeO.Cr2O3 950 30 min-- : ----- do ----------- Do. 950 ----------- I hr --------- --- -- do ----------- Do. III ---- ----- do ----------------- ---------------------------- ---------- 1500 ------ 30 min ------ H2 -------------- Furnace. 52 ----- III ---- ----- do -- --------------- ---------------------------- ---------- 500 ------ ---- I hr --------- H2 -------------- Do. III ---- Franklinite--. -------- (Complex ferrite of Zn - ---------- 950 ---------- 10 min ------ Air -------------- Air. Fe and Mn.) 54 ----- III ---- ----- do -- --------------- ---------------------------- ----------W---- --- -- 30 min ------ ----- do ----------- Do. 950 ------- --- 30 min ------ ----- do -- --------- Do. 55 ----- III ---- ----- do -- --------------- --- ------------------------ ---------- 1500 --- ------- 30 min ------ H2 -------------- Furnace. 56 ----- III ---- ----- do -- --------------- ---------------------------- ---------- f950 ---------- 2 hrs -------- Air -------------- Air. 1600 --------- - 30 min ------ Hi -- ------------ Furnace. 67 ---- III ---- ----- do -- --------------- ---------------------------- ---------- 1910 ----- ---- I hr --------- H2 -------- ----- - ------------ 950 ---------- 4 rnin --- ---- Air --- ----------- ------------ 58 ----- III ---- ----- do -- --------------- Equal amount pyrite ------ ---------- 600 -- -------- 5 min ------- ----- do ------- --- Air. 69 ----- III ---- ----- do -- --------------- ------ do --------- ----------- ---------- 950 ---------- 5 min ------- ----- do ----------- Do. 6o.---- III ---- Siderite --------------- FeO.00 ------------------- ---------- 500 ---------- 30 min ------ Hi -------------- Furnace. 61 ----- III ---- Rhodochrosite -------- AlnO.CO2 ----------------- ---------- -500 ---------- 30 min ------ H2 -------------- Do. 62 ----- III ---- ------------------------ MnCO3 (chemically pure) - ---------- 500 ----- ----- -30 min ------ Hi -------------- Do. 63 ----- 111---- Tantnlite-Columbite-- FeO.(TaCb)206 f?50 ---------- 12 hrs@ ------ Air -------- ----- Air. 300 --------- - 30 min ------ H2 --------- -- Furnace. 64 ----- IV ---- Augite. --------------- (Ca, Mg, Fe) (SiO3) @15J5oO ------- 12 lirs. --- --- Air -------- ----- Air. 3 1 m i i i , : - - - - I - - - - - - - - - - - - - - F u r n a c e . 65 ----- IV ---- Rbodonite ------------ (Mn, Zn, Fe, Cu)Sio3 --- - 500:::::::::: 30 mi. Hi -------------- Do. 66 ----- -------- Olivine --------------- - --------------------------- g@10 1 hr --------- Air -------------- ------------ @500 1 hr --------- H2 ------- ------------
[5]D o n g t r c o o r e i " WA= of Induction Test Untmted Aftor trmtment (M (me&wro d powder NO. in in pusm) per cablo oontiD. C. samp.t. A. C. activitt D. 0. au3oopt. A. 0. ootivity Motor) ------ Strong ------------- ----- None -------- ------------- ------------ ------------ ----------- ::do ------------- :: ----- ----- do o- I" 00 3:: V- --------- ------------ ------------ --- do --- ----------------- ----- diL - -- ------ ----- do --------- 1004 -------------------- ------------ ------------ - 4 ------ ----- do --------------------- - ---- do ------------- - --- do --------------- - - ------------ ------------ - -------- ---- do --------------- --------- ------------ - -------- --------------------- -----d-------------- - 6 None ---------------------- ----- do ------------- Modemto -------- w - -------- ----- -- 7 ------ ----- do --------------------- ----- do ------------- ----- do ---------------I -@-do -------------------- ----- do- ----- do ------- -wwi ---------------------- Modaii;@;.--::::::: ----- do ------ None ---------------------- None -------------- -- -- do 16 75 ------ 11 ----- ----- do --------------------- ----- do ------------- Strong --------------9 I ---- do ------------- ----- do --------------- 350 100 I.SL do ------------- ----- do ---------------- 13 do-::::::: 14-- do -------- do ------------- strong --------- ----------------- ---- 15 ::: ::--:do - ------------------- ------ do ------------- - @"7do --------------- N6iia ----------------- -------- ---- ------------- ----16::___ __:--_do -------------- ------ ----- do ------------- Moderate ----------- 7 ---- --------- --------- --------------- ----- ----- ----- do - ---------- do do ------ -- 13:: ----- --- do -------------- :-: i; do ---- 11 - -------- ---- Boo 240 &11 19 do --------------------- -:--- ---- sligei:: - -------- ---- ------------ ------------ 20--:-: --:::do -------------------- ----- do ---- Modomto ModamiiiWiiii@ii: - ------------ ------------ ------------ 21--. - :----do--- do ---- ---- - ----- do ------- I lp 22 ---------- ------ 7 ----------------- ----- .::: ------------ 370 1,100 &oi ----------- -------------------- -------------- ------------ -- ---------- ------------ 7 23 ----- None ---------------------- None -------------- Modmto-. 21 ----- ----- do --------------------- ----- do ------------- ----- do ------ -!'@0:09---:::::::@ ---- -- ---------- ----------- 25d--------------------- ----- do ------------- ----- do --------------- ----- do ------- --- -------- ---- ------------ ------------ 26-:--: --- ::do do ----------- - ----- do --------------- ----- do -------------- : ------------ ------- ----- -----------27:---. -;W-@@k particles ----- ---------------------- 28---: - ----- do --------------------- ----- do ------------- ---------------------:1, 20--:-. None ---------------------- None ------------- Moderate -----------1 --------------- ------ --- ------ - ------- 30 ----- ----- do --------------------- ----- do ------------- ----- do --------------- 19 -------- -------- ---------:-- ----- ::. ng Strong ------------ ----- do --------------- moaiiiii --- ---------- ------------ ------------- ----- 31 "!!do ------- ------- 32- --ven st g r ---- do ------------- - ------ None ---------------- 100 400 & 0 - do D. 07anctievaatfitZ ---- do 2 1. 5m & 0 1 :::dol - -.-do ----- : ------ - ---------------------- ---------------------- 34 ----- - do --------------------- 85 do ------------------ do --- do ------- 100 1,200 LO 36-:::: ::::--do ------------------ ::::-do --- --------do --------- --------------- ------------ - ----------- ----------- 37 ----- ----- do --------------------- ----- do ------------- ----- do --------------- - IOFO@10, ---------------- - ----------- ------------ -------- --- 38 do --------------------- ----- do ------------- ---- do --------------- W-:::: :::---do --- -do ------------- Moderate Mwosi@ii;: 40: ---- ----- do ::----do -------- -do--------------- ----- do ------ 41 ----- ----- do --------------------- ----- do -------- -iti;Wi --------------- Weak-.-.-: --------- -------- ---- ------------ ------------ 42 ----- ----- do --------------------- ----- do ------------- ----- do -------I-------- 100% ----------- ----- ------------ ------------ --- -------- 43 ----- ----- do --------------------- ----- do ------------- ----- do --------------- Moderate ------ ----- ------------ ------------ ----- do -------------------- ----- do ------------- Weak None ---------------- ----------- - ------------ ----- 45::::: ----:::do --------------------- ----- do ------------- ----- do --------------- Few particles ---- ------- ------------ ------------ (weak). 46 ----- ----- do --------------------- ----- do ------------- Modamts ----------- 10017* ----------- - --- ------------ ------------ ------------ 47 do --------------------- ----- do ------------- ------------------ 49::-: do --------------------- ----- do ----------- 49 Veryweak ---------------- ----- do ----------- ----- None ------ So ----- ----- do --------------------- ----- do ------------- Modamte (so was ----- do ----- : : : - : - - - - - - - - - - - - - - - - - - g a n g u e ) . 51 ----- ----- do --------------------- ----- do ------------- Moderate ----------- loop/0 ---------- ------ ------------ ------------ ------------ 52 ----- ----- do --------- do ------------- ----- do -------------- : VOry, little-@ --------- -------- ---- ------------ -----------53----- Weak --------- ------------- Weak -------------- one 54 ----- ----- do --------------------- - ---- do ------------ - ----- do --------------- FOW PUtICIS3 ------- ------------ ------------ ------------ W ----- ----- do --------------------- -- --- do ------------ - ----- do --------------- 25% 56 ----- ----- do --------------------- ----- do ------------- ----- do --------------- 26% ------------- --- 57 ----- ---------------------------- -------------------- ---------------------- iowo Wak None -------------- Weak None ag do --------------------- ----- do ------------- ----- do oo::::-- ---------------------- do'moZ;t7;:::::::::-- Strong ------------- 61- Week -- ------------------ ----- do ------------- :: SmaHamt.--strong-: 62-:-:- None ---------------------- ---- do ------------- SmaU amounl ------ SmaU amount 63 ----- ----- do --------------------- ----- do ------------- ----- do do 64 ----- ----- do --------------------- ----- do ------------- ----- do do Weak ------------------ -- ----- do ------------- Wk SmaU.t---dWng -- ------------ - ----------- ------------ ----- ------------------------ Modamto None ------------ The isted show the proportions of A. 0. active materw present. The rl=tq".g:., in the foregoing table indicate inomp@ete dot&
[6]2,182,404 from an intermediate metallurgical process to a temperature c@f 9501 C. for one hour in an atmosphere oi air and then in a reducing atmosphere at 500' C. for thirty niinutes. 5 The :ftrst operation is Teadily conducted by placing the material, which has previously been crushed and pulverized so that it will all pass through a screen of 48 meshes to the linear inch ' in a refractory container and then by exposing 10 the ore to the air by an occasional stirring or rabbling while heating at 9501 C. during a period of ohe hour. The heating is easily performed with an open muffle furnace but any available source of heat that produces the specified tem!5 perature with adequbte exposure to air is satisfactory. The reducing roast may be performed by placing the product in a refractory boat or- Iron container and inserting in a heat resistant, gastight tube such as an iron pipe. A flow of hy20 drogen producing two or three bubbles per second at the exit end is maintained during the heating and cooling of the charge. The portion of the tube containing the material fiom the roast is heated so that a temperature of 500, C. is main25 tained for thirty minutes in the environment of the charge. Easiest control of -heat is obtaine(i by using an electric resistance heating unit, but the saine result is accomplished in other ways. After cooling in the reducing atmosphere, the 30 chromite is rendered of high coercive force and after exposing to a strong direct magnetic fleld is active in a 60-cycle alternating magnetic field of 50 gauss field strength. The chi-oniite is then in condition to be sepa35 rated by the alternating magnetic field while associated minerals, as, for example, olivine, are unaffected by such a fleld. In some cases we have obtained better results by using a plurality of such oxidation and reduction steps. 40 Example 2 Chaleopyrite is separated from ferberite by a comparatively simple treatment. The material is 45 roasted in air at 6001 C. while stirring for a period of five minutes. The cooled product is exposed to a strong direct magnetic field and then treated on an alternating fleld magnetic separator of 60 cycles. Thechalcopyrite is active In an alter50 nating magnetic field of 50 gauss field strength and jumps while the ferberite under these conditions of treatinent is non-active. Example 3 55 We have also found that by treatrnent of a substantially homogeneous ore to render part of it active in an alternating magnetic field, the impurities may be segregated in the active or nonactive portion. Por instance, an ore may be par60 tially activated and Impurities segregated into either the activated or unactivated portion. We may consider an iron ore from Negaunee, Mehigan, which contains 1.6% sulphur. By giving this material a reducing roast at 4001 C., 93% of 65 the sample became active in a 60-cycle alternating magnetic field of 50 gauss field strength and contained only 1.18% sulphur. 'Me residual 7% analyzed 4.58% sulphur. 70 Example 4 In another case, pyritic gold ore was subjected to roasting and subsequently separated Into an active portion and a non-active portion. The non-active portion contained 1.29 oz. gold per ton 76 and the other only .29 oz. E=,mple 5 We have also found that our method of producing high coercive force in minerals and the like may be applied to metallic iron by dispersing it In mercury. This may be accomplished by any of several ways known in the art. The mercury content of the mixture may be removed or reduced to any amount 'distillation. desired by Iron pfoduced In this way has a coerdive force 10 above 250 and may be compacted into strong permanent magnets. Methods for preparing iron amalganis are described in H. 0. Hofman's "General Metallurgy", McGraw I-lill Book Company, New York '1913 page 510; in United States Patent No. 1,@02,40i issued October 12, i926 to Joseph C. W. Ftazier; and In Kolloid Zeitschrift, vol. 52, page 31, 1930. Example 6 20 The liquid iron amalgams we have also used to extract gold from ores and for this purpose they have the advantage that any finely divided mercury formed durin@ the amalgamation may be separated from the ore by rnagnetic means. 25 Example 7 Untreated hematite is separated from silica gangue by subjecting to ari alternating magnetic field of 500 gauss and a frequency of 25 cycles. 30 It is clear from the above that the broad conception of our invention is in the formation of a high coercive force in certain materials and converting the saine into permanent magnets by exposing the small particles to a direct current 35 magnet. Materials so prepared have a we in the arts as, for example, in forming permanent magnets by molding discrete particles, all of which are permanent magnets, Into a larger magnet structure, thus securing certain obvious advantages in go the manufacture of commercial permanent magnets. The magnetized particles have other uses in the arts. @ According to features of our complete process, these small permanent magnets are employed in 4,5 a separation process. The separation processes involved may be modifled in many respects. In general, however, they involve three types of treatments resulting from three characteristics at once adparent. These are as follows: 50 (a) The attraction of the magnets for each other; (b) The attraction of the magnets for a highly magnetic material such as soft iron; and (c) The activity 6f the magnets in an alternating 55 magnetic field. We shall now consider the general types of processes utilizing these characteristics: Examl)le I 60 We separate roasted hematite from ordinary magnetite by magnetizing the mixture and then sifting it through a screen of a mesh so that all of the material will just pass through in an unmagnetized condition. Since the hematite particles 65 agglomerate, they form composite particles of a size to be retained on the screen, while the nonmagnetized magnetite will remain in the form of small particles which will pass the screen. 0 Example 2 We may utilize the principle involved in Example 1 in a froth flotation process to separate permanently magnetized material from niaterial whicli Is not magnetized. We thus separate 75
[7]2,182,404 hematite which can be made to agglomerate In the mannir indicatdd from silica. Example 3 5 By employing the characterjstic (b) set out hereinabove, we may obtain a direct separation of perman6nt magnetic particles by passing them over a rotating soft Iron puiley. The permanent, magne@s adhere to the surface and are removed I 0 by a scraper while the other material falls off the pwley. By such methods, we have separated spongq Iron from Its associated gangue obtaintng products containing 9.32% Insoluble and 1.25% Insoluble, respectively, for the particles which will i..3. fall offthe(pulley or drum and those, which will -- stick. These figures, of course, are merely illustrative and do not represent the,maximum separation possible. Example 4 20 According to Example 4, we separate t,@vo materials, both of which may be magnetic, but only one of which Is In the form of permanent magnets, by subjecting them to the influence of an altemating magnetic fleld. For example, roasted 25 hematite Is separated, from magnetite by depositing the same onto a moving nonmetallic belt in which the axes of the pulleys are tilted horizontally to make the belt slope laterally. The slope Is such that gravity is not quite sufficient to cause 30 downward movement of the material ]laterally of the belt. If now the particles are subjected to an altemating magnetic field, as, for example, by placing the magnets Immediately under the belt, the roasted hematite becomes active and moves 35 down the slope laterally of the, belt, while the magnetite wfll adhere to the belt and bie deposited after passing over the pulley. This example will be further understood by a more complete reference to the use of the activity of the permanent 40 magnets as described hereinabove. In making use of the activity in an altemating magnetic field to separate permanently magnetic particles, we do not attempt to make the particles traverse any appreciable distance by means of 45 this activity but superpose this activity on a system of forces in balance acting on all the particles of the mixture to be separated. Thus the particles may be held on a surface with the force 6f friction just greater than that of gravity. By 5o applying an alternating fleld, the permanently magnetic particles are activated and their friction is decreased, hence they move away from the others under force of gravity. A balance may be struck In this way bc-tween 55 any two forces acting in opposite directions one of which Is affected by the activity In an A. M. field. Examples of the forces affected by the A. M. fleld are friction, magnetic and electrical forces. These may be opposed with gravity, centrifugal 60 force, or the force of moving water or air. A detailed explanation of one preferr,ed form of our invention to the separation of minerals will make the above points clear. In this preferred method of application of our 65 Invention to the separating of minerals, the ore or n)ineral treated by the methods Indicated is subjected to the action of a direct magnetic fleld and then to an alternating fleld of less intensity than the coercive force of the mineral so arranged 70 that the particles which are active in that fleld may be separated from the nonactive particles. in some cases the use of preliminary treatment with the direct magnetic field may be dispensed with and higher intensities of alternating field 75 may be used. 7 In one preferi-ed forin.of our invention, the minerals and the like to be separated are fed onto a non-magnetic supporting surface, the latter being inclined to the horizontal and capable of movement relative to an alternating magnetic 5 field In such a way that the niaterial is,caused to separate into two or more frgctions by virtue of the jumping motion of some of the particles under the@ action of analtemating magnetic fleld, combined with the force of gravity actin on these 1( 9 moving particles resulting in their jiunping down the slope and across the supporting surface and thus becoming separated from the particles which are less mobile, the latter remaining substantially in their original portion on the supporting surface. 1,5 With regard to the frequency and field strength of the alternating durrent to be employed, we have found that In general the higher the frequency, the more rapid is the motion of the partieles but the more limited Is the field sttength 20 which can be used. We have found that the fleld strength Is limited by two factors. It must be high enough to prevent the particles sticking together and still below that at which activity ceases. 'Mese limits we have called the lower 25 and u er sticky limits. We have found that In . @ pp general the lower limit increases with frequency and the upper limit decreases, so that with some minerals, no satisfactory range exists at frequencles higher than 15. Other minerals show a satis- 30 factory field range at the highest fre4uencies tried (1000 cycles).. The practical carrying out of the process of our invention can be made clear from a reference to specific. methods employed, all utilizing the same 35 general principles but each requiring more or less modifled apparatus. According to one method, we utilize an endl6ss belt passing over two pulleys whose axes are parallel to each other but indlined to the hori- 40 zontal wheieby the top of the belt slants laterally, but longitudinally Is in substantially a horizontal plane. Associated with the surface of the belt, that Is, immediately under the same or otherwise suitably positioned, we place one or 45 more, preferably a plurality, of alternating current magnets suitably designed in accordance with the character of equipment and specifte details of the process involved. A comminuted ore material, the niineral bearing portion of 50 which Is to be concentrated, is now delivered to the top of the belt so as to be conveyed substantially the full length thereof, it being assumed, of course, that the mater@al has previoiisly been prepared in acc@)rdance with the procez;ses de- 55 scribed hereinabove. If the material has not previously been magnetized, It is usualiy necessary to subject it to a charge of direct current magnetism as it is being delivered to the belt. In the simplest forin of process, the belt constitutes a 60 non-magnetic conveyor and is continuously operated to move the material from one end thereof to the other. As the conveyor and the material start to pass through the alternating fields created by the magnets, the portion of the mate- 65 rial capable of accepting a permanent magnetism becomes active and jumps more or less violently, depending upon the frequency of the current, as previously set out. 'Me active materia . I thereby is freed from the force of friction resulting from 70 its contact with the belt at each jumping movement and accordingly moves with considerable rapidity down the slope of the belt where it is delivered into a trough or bin. The remaining portion of the material moves along the belt and 75
[8]2,132,404 may be discharged off the end thereof as It passes over the pulley and thence be delivered to a second bin or trough. When two or more active components are present, they may be successively subjected to stronger :ftelds or :ftelds modifled in respects other than intensity, thereby attaining more than two constituents comprising at least two active constituents and a non-active constituent which may be a non-metallic material. io It is, of course, obvious that even a very active material may be separated from a slightly active material by making only one separation, the slightly active material being allowed to pass continuously along the belt conveyor and delivered to ]5 a trbugh or bin in the same way that entirely inactive materiai would be handled. Following a proc-ess of this kind, we have been able to heat treat a chromite ore and produce a concentrate containing approximately 65% of 20 Cr2O3,.a very high grade product, while previous a,@tempts at concentrating the same ore by usual conceiitration methods did not produce concerttrates appreciably better than 50% CT203. Various modifications of this method may be em2.5 ployed and the same method may be employed with modified apparatus. The apparatus may also be modified to operate on wet material. With regard to the alternating field system@ strength and frequency of the alternating cur-, 30 rent, distances between the magnet poles and the surface supporting the material being treated, and distance from pole to pole, we have found that the most effective arrangement of the alternating field magnetic system is obtaiiied when 3r) single phase current is used and when the magnets are wound in such a direction that adjacent poles have unlikb polarity at any given time. The magnet cores should be laminated and may consist of individual cores which may be placed 40 with their lower poles on a single iron plate, or the magnet system may be constructed from a single laminated core having multiple poles on a common base. The slope of the conveyor surface and the speed 45 of belt travel should be adjustable to suit the material being treated. A demagnetizing coil may be placed between the direct current magnetizing field and the alternating cuxrent separator so that materials 50 below any given coercive force may be demagnetized and thus rendered inactive in the A. C. field. According to another method, a drum is employed formed of ma.-netic material, and the 55 material to be separated is delivered to the drum through a suitable delivery chute. The material which has accepted a permanent magnetism will adhere to the drum, while the particles which do not constitute small individual magnets will fall 60 off the surface of the drum and be deposited into a bin provided for the purpose. Those particles which adhere to the drum are removed therefrom by a scraper or some other suitable means in such a way as to be deposited in a separate bin. 65 According to another process, the material to be separated is in more or less of a pulp condition with a considerable portion of water. A metal disc revolving in an alternating magnetic fleld on a vertical axis is provided and the material fed to 70 the disc near the center thereof. That portion of the material which is magnetic but of low coercive force will resist movement toward the outside of the disc, but the active and non-magnetized material, moved partly by centrifugal force and 75 partly washed by water with which the material Is associated or added water, will be moved off the periphery of the disc. At another location, the material which has adhered to the disc can be removed by subjecting it to the action of a stream of water moving at a comparatively high rate of 5 speed. In still other separations, the comminuted material to be separated Is suspended in water whereby the active material will agglomerate and can readily be separated from the non-agglomerated material, according to many different 10 principles. With regard to the phase relationships of . the alternating cuxrent employed in connection with our invention we prefer to use a single phase current and when we have specifled alternating cur- 15 rent in the foregoing description a single phase current has been in mind. However, it is possible to employ currents having any type of phase relationship In carrying out our invention. We are familiar with apparatus described in earlier 20 patents for the separation of magnetic materials by making use of their motion in a polyphase, moving magnetic field. We do not claim processes based on this motion except where such motion is greatly aided and augmented by the 25 superposition of activity which is due to high coercive force and remanence of the material being treated, in i,;hich case our invention is applicable to polyphase fields and limited only by the appended claims. 30 '%)Vith regard to the field strength to be used it will be clear that this depends upon the separation which it is desired to make and upon the previous direct current activation, if any, of the material to be treated as well as on the properties 35 of the Individual material. In this connection we have found that. the relative coercive force of minera]8 either treated or untreated Is not necessarily the same. at all fleld strengths. Accordingly inider some conditions one mineral may be 40 active In an alternating current fleld and the other mineral unactive while under other conditions the reverse may be true. As an example we have found that magnetite has a higher coercive force than reduced hematite in v4@ry weak flelds. 45 Accordingly if a mixture of magnetite and reduced hematite be activated in a weak direct current fleld and subsequently subjected to the action of a we@Lk alternating current fleld the magnetite and not th6 hematite will be active. In this case 50 the fields to be employed are of the order of flve gauss. Apparatiis utilizable for separating materials by the methods described hereinabove is shown in Transactions A. I. M. E., volume li2, page 534 r)5 et seq. What we claim as new and desire to protect by
