US3097160A - Method of separating differentially heated particles - Google Patents
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- US3097160A US3097160A US856232A US85623259A US3097160A US 3097160 A US3097160 A US 3097160A US 856232 A US856232 A US 856232A US 85623259 A US85623259 A US 85623259A US 3097160 A US3097160 A US 3097160A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03B—SEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
- B03B1/00—Conditioning for facilitating separation by altering physical properties of the matter to be treated
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- This invention relates to a process and apparatus for bushels per hour). cleaning granular materials, and more particularly to such Still another object is that of providing a system of the a process and apparatus for washing grains such as wheat. character described, wherein the apparatus because of Many granular materials much be cleaned as a step its structural simplicity and the minimization of relatively in the processing thereof, and this is especially true of moving components, requires but a small initial investgrain. For example, it was early discovered that a num- 15 ment, has a low maintenance cost and has a low power ber of advantages accrued from washing wheat prior to demand.
- the installation expenses are low and converting the same into flour.
- the equipment can be installed quite rapidly and, if deare the removal of smut and dirt, loosening of the outer sire an integral y beeswing, an improvement in the general sanitary condi-
- Yet another object is in the provision of an improved tion of the grain, and the production of a more uniform Washing process for wheat and the like and for apparatus flour having :a low ash content, improved color, better to carry forth the same, that materially decreases the milling qualities and an increase in the patent flour prodamage to the grain that is inherent in the scouring action cuted.
- Wash g n y g System may ri a large horizontally di d cylinder, Wh t and be noted that the term washer as used in the trade comwater are fed to a closed section of the cylinder where Pfehends y g Stage, Consequently the concepts the washing action takes place.
- a revolving spiral ribbon of washing and drying per se are not necessarily distinwithin the cylinder carries the wheat after washing through g the ehehaetef desefihed, wherein a much a perforated section thereof, wherein the wheat is rinsed.
- r Control Of the moisture Content of the end P is The rinsing action is accomplished and controlled through attained-so much better in fact that the control may be manual or mechanically operated valves that determine o s dercd substantially absolute. the quantity of water delivered to the cylinder.
- the disadvantages include an excessive increase in the moisture drawing is Provided With legends p ing to t content f the grain; the difiiculty of obtaining an adequate nomenclature and indicating the structural components water supply, which must comprehend three to five gallons omprising parts thereof. of water per bushel of grain; the additional power cost of The first stage comprises a mixer 10- of inverted, frustooperating the washer :appara us; and th dditi l majnconical configuration having a conduit 11 feeding into the tenance requirement cannot be overlooked as an economic hollow interior adjacent the upper end thereof, and which factor.
- Other disadvantages which have existed heretois adapted to supply liquid or wash water thereto.
- Nos. 2,835,984 and 2,835,985 are duit 12 through which granular material such as wheat or th l f grain n-i d fi b the wa h water, the di other grain is fed thereto.
- the conduit 12 may comprise posal of the wastes, and the high water costs resulting a portion of a screw conveyor, and if so will have a feed from the inability to reuse the wash water.
- screw 13 cooperatively arranged therewith.
- both of the conduits 11 and 12 have elongated (water washing being one step thereof) are evidenced openings that communicate with the mix'er 10 along an in the high initial cost of the equipment employed and the arc of the surface thereof whereby the infeed of the ma- Vast amount of space required, which may encompas terials, and particularly the wash water, results in a swirlseveral floors in a mill and incorporate as many as sevening motion thereof wherein the material tends to move teen separate cleaning steps. Additionally, the w he through convolutions following the surface contour of are difficult to operate and, as a consequence, are often the mixer.
- an object of the present invention is to charges into the casing 15 of a pump denoted in general provide a process and apparatus for accomplishing the with the numeral 16.
- the pump is preferably of a large same which will overcome a number of the important disadvantages inherent in the prior art systems.
- Another obvolume, low head type; and in the form shown, has multiple stages indicated with the numerals 17, 18;, and 19,
- This invention relates in general to the separation of particles of a given material from a mixture of particles of two or more materials, and more specifically to new methods and means for processing a mixture of particles in the dry state, without the use of water or any other liquid, to achieve such separation.
- the primary object of this invention is to provide new and improved methods and means for separating individual specific types of particles from a mixture of various types of particles. It is a further object of the invention to separate metallic particles, including nonmagnetic particlcs, from nonmetallic particles in a mixture. It is another object of the invention to separate important, or valuable minerals from less important and less valuable minerals in such mixtures as are found in mining areas. Another object of the invention is more efficiently to separate individual components of a particle mixture so as to be able to recover even extremely minute or trace amounts of valuable minerals from collections of spent quantities of original mixtures which have passed through conventional and less efficient methods of separation. Such spent mixtures are sometimes referred to as railings.
- a further object of the present invention is to provide such methods and means which are useful to separate all forms of particles, whether metallic or nonmetallic, and all kinds of metals, whether magnetic or nonmagnetic, from a mixture of particles, and which are particularly useful to recover precious metals such as gold, platinum and rhodium from particle mixtures such as sand and ore tailings in which they are contained.
- a mixture of particles of two or more different types or materials is treated to separate particles of a first of said types or materials from the mixture by selectively heating particles of the first type or material to a temperature greater than the remainder of the mixture, and selectively capturing heated particles of the first type or material with a temperaturesensitive body in contact therewith.
- the invention makes use, for example, of radio-frequency induction fields, timevarying electrostatic fields, electromagnetic wave fields, and other forms of energy in order selectively to raise to ferences in their relative temperatures.
- the invention further contemplates the use of temperaturesensitive material such as paraffin wax, thermoplastic materials, and other materials which can be softened by a Warm or hot particle and thereby become adherent to, or capture, such particles selectively as compared with particles at lower temperatures. It is a further object of the invention to provide methods and means to selectively capture particles in a mixture in accordance with dif- A still further object of the invention is to provide methods and means for achieving such capture on a continuous basis.
- FIG. 1 is a side-sectional view of magnetic field particle separating apparatus according to the invention
- FIG. 2 is a section along line 22 in FIG. 1;
- FIG. 3 is a side-sectional view of a modification of FIG. 1;
- FIG. 4 is a section along line 44 in FIG. 3;
- FIG. 5 illustrates circuits useful to produce magnetic fields for the apparatus of FIGS. 1 and 3;
- FIG. 6 is a magnified sectional view of a particle collecting medium and collected particles
- FIG. 7 is a top view of apparatus like that of FIG. 1 modified to include stirring devices;
- FIG. 8 illustrates schematically the use in series of a plurality of apparatus arrangements according to FIG. 1;
- FIG. 9 is a partial top view of FIG. 8;
- FIG. 10 illustrates schematically the use in series of a plurality of apparatus arrangements according to FIG. 3;
- FIG. 11 is a side-sectional view of an electrostatic field producing arrangement
- FIG. 12 is a section along line 1212 of FIG. 11;
- FIG. 13 illustrates a circuit useful to produce electrostatic fields with devices according to FIGS. 11 and 12;
- FIG. 14 is a side-sectional view of particle fluidization apparatus employed with the invention.
- FIG. 15 is a side-sectional view of particle accelerating apparatus employed with the invention.
- FIG. 16 is a diagrammatic side view of an electromagnetic field producing arrangement
- FIG. 17 is a section along 1717 of FIG. 16;
- FIG. 18 is a modification of FIG. 16.
- FIG. 19 is a section along line 19-19 of FIG. 18;
- a magnetic field coil It is supported on inner coil form 11 and covered by an outer coil form 12., respectively, both made of electrically nonconductive material. These elements are hereinafter sometimes referred to as a magnetic field unit.
- the coil 10 may be made of wire or hollow tubing, for example, copper tubing, depending upon the frequency of operation for which the coil is intended.
- the inner coil form 11 and the outer coil cover 12 may be square in cross section, as shown in FIG. 2, or if desired, they may be round or take any other convenient form.
- a platform 13- made of electrically nonconductive material is disposed across the approximate center of the inner coil form 11, being, if desired, mounted in that form by means of cement or screws (not shown).
- a supply roll 16 of the particle receiving material 14 is disposed at one end- (the left hand end in FIG. 1) of the magnetic field unit and a take-up roll 17 is disposed at the other end to receive the web 14 as it comes through the magnetic field unit.
- the supply and take-up rolls rotate in the direction ated by the coil 19 when the latter is operated for induction heating of the metal particles 19.2, as will be described in greater detail below.
- the electrically conduc tive particles 19.2 become heated by this magnetic field, by the process of induction heating, and adhere to the web 14, being thereby captured by the web as will be described in detail in connection with FIG. 6.
- the electrically nonconductive particles 19.1 do not simultaneously become heated. As the web 14 progresses toward the right in FIG. 1 (arrow 15), and is taken up on the takeup roll 17, the surface of the web becomes vertical and the electrically nonconductive particles 19.1 fall off the web. The electrically conductive particles 19.2 which have adhered to the web remain captured by the web as .the web is rolled onto the roll 17 (as is shown in FIG. 1),
- selective particle separating set A The combination of a hopper with feed 18 and a selective heating unit 11l11-12 is sometimes hereinafter referred to as selective particle separating set A.
- FIGS. 3 and 4 illustrate another manner of employing a magnetic field to separate electrically conductive and nonconductive particles from a mixture of the two.
- a coil 20 is supported on a coil form 21 and covered by an outer cover 22.
- the elements 20, 21 and 22 are a magnetic field unit which is functionally similar to the elements 10, 11 and 12, in FIG. 1.
- the mixture 19 is acted upon by the magnetic field on the way to the web 14, which is advanced continuously under the hopper feed 23 in the direction of the arrow 15, while resting upon a platform 24 which is similar to the platform 13 in FIG. 1.
- Take-up rolls similar to the rolls 16 and 17 in FIG. 1 may be present in the arrangement according to FIGS. 3 and 4, but are not shown in these figures to simplify the illustration of differences between the embodiment of FIGS. 1 and 2 and this embodiment.
- the heated particles of electrically conductive material will again adhere to the web 14 and be captured by it, while the particles of electrically nonconductive material, being for all practical purposes unheated, will not adhere to it. Separation of adhering and nonadhering particles may be accomplished as in FIG. 1.
- the combination of a hopper with feed 23 and a selective heating unit 202122 is sometimes hereinafter referred to as selective particle separating set B.
- FIG. illustrates circuits for providing electric energy for driving magnetic field coils, such as the coil in FIG. 1 or the coil 29 in FIG. 3, for induction heating of metal particles.
- a coil 31) is indicated schematically as wound on a coil form 31 and driven by an electronic oscillator, for example, a Hartley oscillator 32 comprised of the usual components and coupled to the coil by means of a transformer 33.
- a radio frequency choke 34 (useful for the purpose to be described immediately below) is provided in the connection between the transformer 33 and the coil 30.
- the Hartley oscillator 32 includes a vacuum tube 32.1 and terminals 32.2 and 32.3 (labeled B-+ and B respectively) for the operating high voltage.
- An operating frequency in the range of 4QQ kc./sec is suitable for inductively heating particles of electrically conductive material which are above approximately microns in cross-sectional size.
- a frequency in the range of about 40 megacycles per second it is preferable to use a frequency in the range of about 40 megacycles per second. If desired, the coil 30 can be driven at a frequency in one of these ranges, and a second coil 40 can be provided and driven at a frequency in the other of these ranges.
- FIG. 5 illustrates such an arrangement, in which the above-described Hartley oscillator circuit 32 and coil 31 ⁇ are arranged for operation at about 400 kc./sec., and a second Hartley oscillator circuit 42 and the second coil 49, interwound with the firstnamed coil 30, are provided and arranged for operation at approximately 40 megacycles per second.
- the second oscillator circuit 42 includes an electron tube 32.1 and B]- and B terminals 4-2.2 and 42.3, respectively.
- This oscillator circuit is connected to its coil 41? via blocking condensers 43.1 and 4-3.2. These blocking condensers serve the function of preventing 400 kc./sec. signals from the first coil 30 from entering the second oscillator circuit 42.
- the RF choke 34 which is connected in series between the transformer 33 and the first coil 39, prevents the 40 megacycle per second signal from the second oscillator circuit 42 from entering the first oscillator circuit 32.
- Each of the -B+ terminals is connected to the anode of the respective electron tube via a radio frequency choke 35, 35, respectively.
- the apparatus of FIG. 1 or FIG. 3 may be operated in the range of either of the frequencies 400 kc./sec. or 40 megacycles per second or some other frequency range, and that if desired two sets of coils may be wound on the coil form 11 or 21 and two frequency ranges may be used.
- particles of an identical or similar metal can be separated on the basis of their relative sizes by choosing an operating frequency suitable for heating particles in a desired size range to a higher temperature than particles of other sizes.
- an operating frequency suitable for heating particles in a desired size range to a higher temperature can be chosen.
- gold particles of sizes 25 to 75 microns in diameter can be selectively separated not only from sand, but also from other metals of larger sizes, by using a frequency in the range from 10 to 50 megacycles per second.
- FIG. 6 which shows an enlarged partial cross-sectional view of the web 14, the web is made of a base strip 51, which may be paper, on which there is coated or otherwise adhered a surface coat 52 of material which can be melted by hot particles 53'.
- a base strip 51 which may be paper
- a surface coat 52 of material which can be melted by hot particles 53'.
- the heated electrically conductive particles on the web 14 whether heated prior to arriving at the web (FIG. 3) or after arriving at the web (FIG. 1) come in contact with the surface coat 52, they melt the coat and penetrate varying distances into it. The coat then flows over the particles for a short time until it again freeze and partially covers the particles as is shown in FIG. 6.
- the web 14 may be conveniently made of waxed paper in which case the base 5-1 is paper and the coat 52 is wax (e.g., paraffin wax).
- the particles 53 shown in FIG. 6 are the same as the particles 19.2 shown in FIG. 1.
- electrically conductive particles selectively heated in a mixture of electrically conductive and electrically nonconductive particles can be continuously captured on a web 14 which then may be rolled on a take-up roller 17 (FIG. 1), if desired, for convenience in storing and shipping.
- the process of the present invention is operable with the particles which are to be heated separated from each other so that they are individually heated; there is no need to pass a current from one particle to the next, and in this respect the use of induction heating according to the present invention to heat individual metal particles of sizes in ranges of the order of microns, for example, is unlike any use for induction heating apparatus heretofore known to the art.
- FIG. 7 illustrates one method of stirring these particles, in which nozzles '55 are disposed above the web 14.
- FIG. 7 is a top view of an apparatus according to FIG. 1 and like par-ts have the same reference characters in these figures.
- the nozzles 55 are located in close proximity to the top surface of the web 14, as is schematically illustrated by one nozzle 55 in FIG. 1. It will be appreciated that the nozzles 55 are in practice connected to a source (not shown) of pressurized air or other gas which upon being fed at a proper velocity toward the surface of the web 14 will stir the particles of the mixture 19 which are present on the surface.
- stirring means can be employed in apparatus according to FIG. 3.
- other forms of stirring mechanism such as mechanical or electromechanical vibrators, may be employed, in place of gaseous-stirring, if desired.
- Such vibrators could, for example, be attached to the platform 13 (FIG. 1) or 24 (FIG. 3).
- FIGS. 8 and 9 illustrate 'a plurality of selective particle separating sets A1 and A2 according to FIG. 1 employed in series with a single particle collecting web 14 to increase the concentration of electrically conductive particles captured on a given web.
- the web 14 is arranged to be advanced in the direction of the arrow 15 sequentially through two such sets A-1 and A2, but it will be appreciated that any number of selective particle separating sets -up to An (not shown) may be employed.
- a gaseous particle stirring arrangement 56 comprising a plenum chamber 56.1 and a series of nozzles 56.2 arranged across the web 14 as shown more clearly in FIG. 9.
- Another similar particle-stirring arrangement 56 follows the heating coil assembly 10.2 of the second set A2. The purpose of the particle-stirring assemblies 56 is to blow away the loose particles of electrically nonconductive material not adhering to the web 14 after passage of the web '14 through each of the heating coil assemblies 10.1, 10.2 10.n.
- each plenum chamber 56.1 will be connected to a source (not shown) of air or other gas under suitable pressure for this purpose. It will be appreciated that if the web 14 is taken up on a take-up roll like the 'roll 17 in FIG. 1 after passage through a number n of selective particle separating sets A-1, A2 A-n, there will be no need'for a particle-stirring arrangement 56 following the last such set in the series.
- a single web 14 can be used to collect electrically conductive particles captured from a series of hoppers 18 .1, 18.2 18.11 so that the web 14 will collect a greater density of electrically conductive particles than would be the case if it were .passed through only one selective particle separating set A as in .FIG. 1, all other factors being equal.
- FIG. 10 illustrates an arrangement similar to FIG. 8 employing a plurality of selective particle separating sets B of FIG. 3, in series.
- the web 14 passes in the direction of the arrow 15 under a firstsuch set B-1, and
- FIGS. 11 and 12 illustra-te an electrostatic field heating unit which may be used in place of the magnetic field units 1tl.11--12 and 20-2122 which are shown in FIGS. 1 and 3, respectively.
- a mounting form 61 of electrically nonconductive material has electrically conductive plates 62 and 63 on two opposite inner surfaces.
- a platform 64 identical in structure and purpose to the platform 13 of FIG. 1 is supported within the form 61 for use in the arrangement according to FIG. 1.
- the form 61 is shown square in cross-sectional shape, as in FIG.
- FIGS. 11 and 12 omit the showing of any hopper, particle feed, or take-up rolls, since as it is stated above, the electrostatic field unit '616263 can be substituted for the magnetic field units of FIG. 1 or ,3. Material comprising ing a mixture of particles some of which can be heated to a higher temperature than others by a time-varying electrostatic field, is in either case passed between the plates 62 and 63 of the electrostatic field heating unit,
- the plates 61 and 6 2 can be supplied with a suitable time-varying potential to create a time-varying electro static field by means of a Colpitts oscillator circuit as shown in FIG. 13.
- This circuit comprises the plates 61 and 62 as a large capacitor, an induction coil 65 and an electron tube 66', having 13+ and B- terminals 67 and 68, respectively, and a radio frequency choke 69 between the B+ terminal 67 and the anode of the electron tube 66. 'Other components of this circuit are well known and will not be described.
- electrostatic field heating units may be employed sequentially, in the manner illustrated in FIG. .8 or FIG. 10, if desired. Further, if it is desired to employ electrostatic fields of two or more different frequencies, successive heating units may have different frequencies applied to them, as is described above with refthrough a bottom input nozzle 71 and with raw particle input namely, a mixture like the mixture 19, at the top
- the arrow 15.1 shows the direction of.
- the particle mixture is converted by the air into a fluidized mixture 73 which then flows through a horizontal output pipe 74 and thence in the direction of the arrow 15.2 through a heating chamber 75, which is representative of any suitable selective particle heating means, such as the magnetic field unit .1tl-1112 of FIG. 1 or -2122 of FIG. 3, or the respectively.
- a heating chamber 75 which is representative of any suitable selective particle heating means, such as the magnetic field unit .1tl-1112 of FIG. 1 or -2122 of FIG. 3, or the respectively.
- the organization of parts is like that of FIG. 3, in that the particle mixture is treated before reaching the collecting web 14.1; however, in the particular embodiment shown in FIG. 14, the particles are propelled through the heating chamber 75 by means of the fluidizing mechanism, instead of being dropped through the chamber under the force of gravity as in FIG. 3.
- the fluidized mixture 74 could be propelled or dropped vertically onto the web 14.1, if desired, or even propelled vertically upward to a collecting surface on the underside of the web; in either of these cases the collecting assembly 76 would be horizontally disposed (with reference to FIG. 14).
- FIG. 15 shows an alternative particle propelling mechanism in the form of a sand blasting apparatus.
- a chamber 80 in which a particle mixture 19 reposes, is used as a supply of the particle mixture, anld air under high pressure is fed into a blast pipe 81 connected with a vertical take-up pipe 82 which reaches into the particle mixture.
- Particles of the mixture 19 are carried up through the take-up pipe 82 and mixed with the air under high pressure in the nozzle 83, whence they are propelled at relatively high speed through the heating chamber 75 in a stream 19.4 toward the collecting web 14.1.
- FIG. 15 may be employed with a single collecting web 14.1, in the same manner of FIG. 10 for example, and that in such cases the particle collecting surface of the web may be so disposed (e.g., vertically) that the. nonadhering and hence uncaptured particles can fall away from the web under the force of gravity, so that stirring devices, like the stirring arrangements 56' in FIG. 10, may be omitted.
- FIGS. 16 and 17 illustrate one such embodiment of the invention, in which a waveguide 90 is supplied with ultrahigh or very high frequency energy by means of a generator 91., which may, for example, be a magnetron or a klystron or other form of oscillator circuit.
- the waveguide has a rectangular cross section, and is intended for operation in the fundamental or TE mode.
- the fundamental mode of high frequency electromagnetic wave energy in rectangular wave guides is well known. See, for example, Department of the Army Technical Manual TM 11-673, Generation and Transmission of Microwave Energy, June 1953, Section 55 (a).
- the generator will be connected to one end of the Waveguide 90 and a nonreflecting termination 92 will be connected to the other end, for the purpose of preventing the setting up of a standing wave field in the waveguide.
- a standing wave field might have hot and cold regions, whereas a travelling wave field would avoid having such regions and is therefore preferred.
- Slots 93 and 94 are cut longitudinally in the narrow side walls of the waveguide 90 and a platform 95 of dielectric material is mounted transversely in the Waveguide immediately to one side of these slots.
- the platform 95 is similar in purpose to the platform 13 in FIG. 1.
- the waveguide 90, generator 91 and termination 92 forman electromagnetic field unit 91-92, which can be substituted for the magnetic field unit 10-1112 in arrangements according to FIG. 1.
- the web 14, hearing particles (not shown) previously deposited in an arrangement according to FIG. 1, is passed transversely through the waveguide through the slots 93 and 94 in the direction of the arrow 15.3.
- the web 14 is preferably disposed for maximum coupling of metal particles with the magnetic wave field.
- a tube 96 is supported transversely in the waveguide 90, as is shown in FIGS. 18 and 19.
- the tube 96 is made of dielectric material and may if desired be of the same cross-sectional shape and dimensions as the output pipe 74 of the fiuidization mechanism according to FIG. 14, in which case the tube and pipe are connected together at their ends as is shown in FIG. 19, and a fluidized stream (not shown) of particles is propelled through the tube '96 toward a collecting web (not shown) in the direction of the arrow 15.4.
- This arrangement is of the general type represented by FIG. 3, in which the particle mixture is treated for selective heating before coming in cont-act with the collecting web.
- a plurality of tubes 96 may be used spaced along the axis of the waveguide 90' as desired so that a single wave guide may be employed to treat a plurality of streams of particles simultaneously.
- the mixture 19 can be propelled through it, according to FIG. 14 or FIG. 15, or dropped through it according to FIG. 3.
- a plurality of electromagnetic field units may be employed, according to FIG. 8 or FIG. 10, and, further, these may be driven at different frequencies or at a single frequency as in thecases of the other embodiments of the invention described above.
- An important feature of this invention is the small amount of power required to elfect separation of metallic from nonmetallic particles. This is best appreciated by consideration of the fundamental physical principles that apply. The amount of power required for separation per unit weight of metallic particles is calculated by the use of the mathematical expressions below, in accordance with actual conditions that pertain in a preferred embodiment of the invention.
- a paraffin wax as a heat-sensitive body 14.
- This wax may be utilized as .a coating on a paper base according to FIG. 6 (wax paper).
- the melting temperature of this material is typically 55 centigrade (Handbook of Chemistry and Physics, 29th edition). Consequently, the metallic particles need only be heated selectively to a temperature slightly above 55 C. in order to be captured by the paraffin wax.
- the gold particles need be heated only to 6 0 C. or higher in order that they will locally melt paraifin wax on contact. It is clear that the praffin wax that is melted by the heated metal particles will then cool the small metal particles almost instantly, capturing them during the resolidification of the wax. This capture will be either on or near the surface of the'wax or in the body of the wax beneath the surface after penetration by the heated metal panticles.
- the energy required to accomplish this rise in temperature is expressed by the equation where a Q is energy in gram calories;
- m is the mass in grams of the metal involved
- c is specific heat (over the given temperature range); T is the final temperature; and g T is the initial temperature.
- the presently preferred form of energy for selectively heating metallic particles through such a temperature range without simultaneously heating the nonmetallic particles to any significant degree is a radio frequency time-varying magnetic field.
- This is of the type known as induction heating.
- this invention employs induction heating in a novel manner in -that the particles being heated need not be, and preferably are not, in contact with each other, but are individually heated.
- an induction heating generator or generators e.g., according to FIG.
- the metallic particles are heated rapidly and efliciently, while the nonmetallics are substantially unaffected and remain cold (i.e., at their original temperature).
- the considerations that govern the choice of frequency of the radio frequency induction heating generator are based upon considerations that include skin effect and particle size. Skin effect, or depth of penetration of a time-varying magnetic field is expressed by for a nonmagnetic material, where s is the depth of penetration (that is the depth at which the energy level has dropped to 1/ e or 0.37 approx. times the magnitude at the surface);
- p volume resistivity of the metal being heated
- f frequency of the induction field
- e is the Naperian logarithm base.
- Bm is maximum flux density
- the heat developed is proportional to the square of the frequency of the induction heating field.
- the depth of penetration is inversely proportional to the square root of this same frequency, and therefore, while the frequency should be as high as possible to develop heat, an upper limit is imposed on the frequency by the skin effect. Above this upper limit, the particle is no longer uniformly heated, and only the skin is heated. Below this frequency the heat developed falls off. The optimum frequency, then, is the highest frequency which produces uniform heating of particles of a given size.
- a frequency, f such that the depth of penetration, s, is substantially equal to the radius of the particle that is to be heated. In a practical case, this is an average radius of a group of particles, and it may be desirable in some cases to use two or more frequencies (as in FIG. 5). For example, in the case of gold particles which are 25 to 75 microns in diameter, the optimum frequency range is to 50 megacycles per second. For larger particles, up to 1 0 1 millimeter in diameter, frequencies in the range to 1000 kilocycles per second are desirable.
- first materia and second material as used in the claims are intended to include particles of different sizes of the same element or compound, as well as particles of the same or different sizes of different elements or compounds.
- Method of treating a mixture of particles of at least two different materials to separate particles of a first of said materials from said mixture comprising the steps of propelling .a gas through said mixture and thereby fluidizing said mixture in a gaseous medium, propelling the fluidized mixture past a source of energy for applying to the fluidized mixture energy which selectively heats particles of said first material to a higher temperature than particles of the remainder of said mixture, thereafter propelling said fluidized mixture with said selectively heated particles toward a temperature sensitive body and selectively capturing heated particles of said first material with said temperature-sensitive body in contact therewith, the same gas being employed under pressure for fluidizing said mixture and for propelling the same successively past said source and toward said body.
- Method of treating a mixture of particles of at least two different materials to separate particles of a first of said materials from said mixture comprising propelling a gas through said mixture and thereby fluidizing said mixture in a gaseous medium, propelling the fluidized mixture through a field of energy which selectively heats particles of said first material in a given time to a higher temperature than particles of the remainder of said mixture, and employing said fluidizing gas for propelling said fluidized mixture containing said selectively heated particles into contact with a body which is adherent substantially only to particles at the temperature achieved by said heated particles of said first material, whereby selectively to capture said heated particles of said first material with said body.
- Method of separating metallic particles from nonmetallic particles in a particle mixture comprising the steps of propelling a gas through said mixture and thereby fluidizing said mixture in a gaseous medium, propelling the fluidized mixture through an induction heating mag- .netic field to heat the metallic particles to a given tempera :ture higher than the temperature of the nonmetallic par- .said particles as a fluidized mixture past a source of energy for selectively heating particles of said first material to a higher temperature than particles of the remainder of said mixture, and then employing the same gas to propel said fluidized mixture with said selectively heated particles toward a temperature sensitive body for selectively capturing the higher temperature particles, said gas being in continuous motion throughout said steps.
- Method of treating a mixture of particles of at least two ditferent materials to separate particles of a first of said materials from said mixture comprising the steps of propelling a gas in motion under pressure through said mixture to fluidize the mixture whereby substantially to separate the particles from each other, then employing the same gas to propel said particles as a fluidized mixture past a source of energy for selectively heating particles of said first material to a higher temperature than particles of the remainder of said mixture, and then employing the same gas to propel said fluidized mixture with said selectively heated particles toward a temperature sensitive body for selectively capturing the higher temperature particles, said gas being in continuous motion throughout said steps.
- Method of treating a mixture containing metallic particles of different sizes to separate said metallic particles from said mixture comprising the steps of employing a gas in motion under pressure to fiuidize said mixture whereby substantially to separate the particles of said mixture from each other, then employing the same gas to propel said particles as a fluidized mixture through an electromagnetic field of at least two different frequencies selected for their ability selectively to heat said metallic particles to a higher temperature than the remainder of said mixture, and then employing the same gas to propel said fluidized mixture with said selectively heated particles toward a temperature sensitive body for selectively capturing the higher temperature particles, said gas being in continuous motion throughout said steps.
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US856232A US3097160A (en) | 1959-11-30 | 1959-11-30 | Method of separating differentially heated particles |
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US856232A US3097160A (en) | 1959-11-30 | 1959-11-30 | Method of separating differentially heated particles |
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Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3463310A (en) * | 1968-02-27 | 1969-08-26 | Us Interior | Separation method |
US3969225A (en) * | 1974-04-04 | 1976-07-13 | I. Jordan Kunik | Differential separation of particulates by combined electro-static and radio frequency means |
US4049544A (en) * | 1975-01-07 | 1977-09-20 | Henry Neil Turner | Method and device for separating particles |
US4077871A (en) * | 1975-04-14 | 1978-03-07 | Occidental Petroleum Corporation | Separation of colored particulate glass |
US4332700A (en) * | 1979-10-22 | 1982-06-01 | Sava Kranj Industrija Gumijevih, Usnjenih In Kemicnih Izdelkov N.O.Sol.O. | Method for separating rubber from metal |
US4469573A (en) * | 1979-10-22 | 1984-09-04 | Sava Kranj Industrija Gumijevih, Usnjenih In Kemicnih Izdelkov N.L.Sol.O. | Method and arrangement for separating rubber from metal |
US4526679A (en) * | 1983-09-02 | 1985-07-02 | Texaco Inc. | Removal of low melting particles from unground coal liquefaction residue |
US5161695A (en) * | 1989-12-07 | 1992-11-10 | Roos Edwin H | Method and apparatus for separating particulate material according to conductivity |
US20160279674A1 (en) * | 2013-03-20 | 2016-09-29 | Technological Resources Pty. Limited | Processing mined material |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
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US1614611A (en) * | 1925-01-14 | 1927-01-18 | Westfield River Paper Company | Paper and process of coating the same |
US1617945A (en) * | 1925-01-14 | 1927-02-15 | Westfield River Paper Company | Coated paper and process of making the same |
US2468472A (en) * | 1946-04-01 | 1949-04-26 | Charles P Townsend | Process and apparatus for separation of electrically conducting material from nonconducting material |
US2873219A (en) * | 1954-12-20 | 1959-02-10 | Joseph B Brennan | Metal-coated batt and method and apparatus for producing same |
US2899055A (en) * | 1956-09-26 | 1959-08-11 | Electrostatic method and apparatus | |
US2907456A (en) * | 1957-05-21 | 1959-10-06 | Int Salt Co | Separation of materials |
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Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
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US1614611A (en) * | 1925-01-14 | 1927-01-18 | Westfield River Paper Company | Paper and process of coating the same |
US1617945A (en) * | 1925-01-14 | 1927-02-15 | Westfield River Paper Company | Coated paper and process of making the same |
US2468472A (en) * | 1946-04-01 | 1949-04-26 | Charles P Townsend | Process and apparatus for separation of electrically conducting material from nonconducting material |
US2873219A (en) * | 1954-12-20 | 1959-02-10 | Joseph B Brennan | Metal-coated batt and method and apparatus for producing same |
US2899055A (en) * | 1956-09-26 | 1959-08-11 | Electrostatic method and apparatus | |
US2907456A (en) * | 1957-05-21 | 1959-10-06 | Int Salt Co | Separation of materials |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3463310A (en) * | 1968-02-27 | 1969-08-26 | Us Interior | Separation method |
US3969225A (en) * | 1974-04-04 | 1976-07-13 | I. Jordan Kunik | Differential separation of particulates by combined electro-static and radio frequency means |
US4049544A (en) * | 1975-01-07 | 1977-09-20 | Henry Neil Turner | Method and device for separating particles |
US4077871A (en) * | 1975-04-14 | 1978-03-07 | Occidental Petroleum Corporation | Separation of colored particulate glass |
US4332700A (en) * | 1979-10-22 | 1982-06-01 | Sava Kranj Industrija Gumijevih, Usnjenih In Kemicnih Izdelkov N.O.Sol.O. | Method for separating rubber from metal |
US4469573A (en) * | 1979-10-22 | 1984-09-04 | Sava Kranj Industrija Gumijevih, Usnjenih In Kemicnih Izdelkov N.L.Sol.O. | Method and arrangement for separating rubber from metal |
US4526679A (en) * | 1983-09-02 | 1985-07-02 | Texaco Inc. | Removal of low melting particles from unground coal liquefaction residue |
US5161695A (en) * | 1989-12-07 | 1992-11-10 | Roos Edwin H | Method and apparatus for separating particulate material according to conductivity |
US20160279674A1 (en) * | 2013-03-20 | 2016-09-29 | Technological Resources Pty. Limited | Processing mined material |
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