[go: up one dir, main page]

WO1998036842A1 - Traitement de mineraux salins - Google Patents

Traitement de mineraux salins Download PDF

Info

Publication number
WO1998036842A1
WO1998036842A1 PCT/US1998/003349 US9803349W WO9836842A1 WO 1998036842 A1 WO1998036842 A1 WO 1998036842A1 US 9803349 W US9803349 W US 9803349W WO 9836842 A1 WO9836842 A1 WO 9836842A1
Authority
WO
WIPO (PCT)
Prior art keywords
ore
magnetic
impurities
trona
separation
Prior art date
Application number
PCT/US1998/003349
Other languages
English (en)
Inventor
Rudolph Pruszko
Roland Schmidt
Dale Lee Denham, Jr.
Original Assignee
Environmental Projects, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Environmental Projects, Inc. filed Critical Environmental Projects, Inc.
Priority to AU64373/98A priority Critical patent/AU6437398A/en
Publication of WO1998036842A1 publication Critical patent/WO1998036842A1/fr

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D7/00—Carbonates of sodium, potassium or alkali metals in general
    • C01D7/12—Preparation of carbonates from bicarbonates or bicarbonate-containing product
    • C01D7/126—Multi-step processes, e.g. from trona to soda ash
    • 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
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C1/00—Magnetic separation
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D7/00—Carbonates of sodium, potassium or alkali metals in general

Definitions

  • the present invention relates to the beneficiation of saline minerals and, more specifically, trona, by methods of magnetic separation.
  • trona Na 2 C0 3 .NaHC0 3 .2H 2 0
  • high-purity trona is commonly used to make soda ash, which is used in the production of glass, paper and other goods.
  • Naturally- occurring trona, or crude trona is found in large deposits in the western United States, such as in Wyoming and California, and also in Egypt, Kenya, Botswana, Cambodia, China, Venezuela and Turkey.
  • the largest deposit of trona in the world is located in the Green River Basin in Wyoming.
  • Crude trona ore from Wyoming is typically between about 80% and about 90% trona, with the remaining components including shortite, pyrite, quartz, dolomite, mudstone, oil shale, kerogen, mica, nahcolite and clay minerals.
  • U.S. Patent No. 4,341,744 discloses a dry beneficiation process which is less complex and less expensive than the above-described wet beneficiation process.
  • Such a dry beneficiation process generally includes crushing the crude trona, classifying the trona by particle size, electrostatically separating certain impurities, and optionally magnetically separating other impurities.
  • Such a process can yield trona or soda ash having up to 95% to 97% purity with a 60- 74% recovery, depending on the quantity and type of impurities present in the crude trona ore.
  • U.S. Patent No. 5,470,554 discloses a dry method for beneficiating trona or soda ash that generally comprises the step of density separation, and optionally includes electrostatic separation and/or magnetic separation.
  • U.S. Patent No. 5,470,554 is incorporated herein by reference in its entirety.
  • the resulting product can have trona or soda ash purities on the order of 97-98% or more.
  • One embodiment of the invention is a process for recovering a saline mineral from an ore which contains saline mineral and impurities.
  • the method includes separating a first portion of impurities from the ore by magnetic separation which includes subjecting the ore to a magnetic flux density of greater than about 20,000 Gauss.
  • the saline mineral selected from trona, borates, potash, sulfates, nitrates and chlorides, and most preferably is trona.
  • the process includes such a method of magnetic separation of impurities, wherein an impurity selected from shortite and pyrite are separated. In these embodiments, at least about 25% of the impurity and up to more than 75% of the impurity is removed.
  • a process for recovering saline mineral from an ore which includes saline mineral and impurities.
  • the method includes calcining the saline mineral in an inert atmosphere and the separating a portion of the impurities from the ore by magnetic separation.
  • the inert atmosphere is any nonoxygen- containing atmosphere and can be selected from carbon dioxide, nitrogen, and water vapor.
  • calcination is conducted in an oxygen- containing atmosphere at a temperature of greater than about 150°C and subsequently separating a portion of the impurities by magnetic separation.
  • a further embodiment of the present invention includes a process for the purification of saline minerals in an ore which includes saline mineral and impurities by magnetic separation in a first magnetic field, wherein the first magnetic field has positions of higher intensity and lower intensity.
  • the process includes pre-aligning the ore on a surface with respect to one or more of said positions of higher intensity of said first magnetic field before separation.
  • the process further includes separating a portion of the impurities from the ore by magnetic separation in the first magnetic field.
  • a process for removing magnetic impurities from an ore which contains a saline mineral and magnetic impurities and has a particle size of less than 100 mesh.
  • the process includes subjecting the ore to a magnetic flux density of greater than about 20,000 Gauss whereby magnetic impurities are separated from the saline mineral.
  • This process can include recovering greater than about 25 wt.% of the magnetic impurities and up to greater than about 75 wt.% of the magnetic impurities.
  • Fig. 1 is a graph of the magnetic properties of pyrite from trona calcined at low temperature.
  • Fig. 2 is a graph of the magnetic properties of pyrite from trona calcined at low temperature and washed with hydrochloric acid.
  • Fig. 3 is a graph of the magnetic properties of pyrite from uncalcined trona.
  • Fig. 4 is a graph of the magnetic properties of pyrite from an ore body other than trona from Climax, Colorado.
  • Fig. 5 is a graph of the magnetic properties of pyrite from an ore body other than trona from Vulcan, Colorado.
  • Fig. 6 is a graph of the magnetic properties of pyrite from an ore body other than trona in Argentina.
  • Fig. 7 is a graph of the magnetic properties of shortite from a non-magnetic fraction of uncalcined trona.
  • Fig. 8 is a graph of the magnetic properties of shortite from a magnetic fraction of uncalcined trona.
  • Fig. 9 is an illustration of a design for an open gradient magnetic separator.
  • the present invention is a dry beneficiation process for recovering saline minerals from an ore containing the saline mineral and impurities, and takes advantage of previously unrecognized characteristics of such ore.
  • saline mineral refers generally to any mineral which occurs in evaporite deposits.
  • Saline minerals that can be beneficiated by the present process include, without limitation, trona, borates, potash, sulfates, nitrates, chlorides, and preferably trona.
  • the purity of saline minerals within an ore depends on the deposit location, as well as on the area mined at a particular deposit.
  • the mining technique used can significantly affect the purity of the saline minerals. For example, by selective mining, higher purities of saline minerals can be achieved.
  • the saline mineral trona deposits are located at several locations throughout the world, including Wyoming (Green River Basin) , California (Searles Lake) , Egypt, Kenya, Venezuela, Botswana, Mongolia, China and Turkey (Beypazari Basin) .
  • a sample of trona ore from Searles Lake has been found to have from about 50% to about 90% by weight (wt.%) trona and a sample taken from the Green River Basin in Wyoming has been found to have from about 70 wt.% to about 92 wt.% trona.
  • the remaining 8 wt.% to 30 wt.% of the ore in the Green River Basin sample comprised impurities including shortite, pyrite, shale consisting predominantly of dolomite, clay, quartz and kerogen, and traces of other impurities.
  • Other samples of trona ore can include different percentages of trona and impurities, as well as include other impurities.
  • trona is often processed by calcination to produce soda ash (Na 2 C0 3 ) . It should be noted that, unless specifically indicated otherwise, use of the term trona herein can refer to both trona (i.e., Na 2 C0 3 .NaHC ⁇ 3 .2H 2 0) and trona which has been processed by calcination to form soda ash.
  • saline minerals such as trona
  • saline minerals do not have a constant distribution of impurities throughout the saline mineral particles. That is, crushed saline mineral ore particles have a variety of impurity contents ranging from no impurities in some particles to almost total impurities in other particles. It is believed that this characteristic of saline minerals was not previously recognized. Therefore, until the recognition of the present invention, there has been no suggestion or teaching to conduct aspects of the present process. It has been discovered that the impurities in saline mineral ores, such as trona containing ores, are typically concentrated in a relatively small percentage of the particles, while the rest of the saline mineral particles can be of relatively high purity.
  • the process of the present invention includes all methods for selectively separating high and low purity products whether manual or automated. That is, more commercially-viable processes for separating the high purity saline mineral from the low purity saline mineral also fall within the scope of this invention.
  • the process of the present invention includes a process for selectively separating a low purity fraction having more than about 3% impurity content from a high purity fraction having less than about 3% impurity content. Such separation is based upon differences in the properties of the particles at the level of impurities present in the particles.
  • the step of separating impurities from an ore containing saline mineral and impurities includes the step of ultra- high magnetic separation.
  • the ultra-high magnetic separation step subjects the ore to conditions such that materials of different magnetic susceptibilities (e.g., trona and shale) separate from each other into a recovered stream and an impurity stream.
  • the ultra-high intensity of the magnetic flux during the magnetic separation step is at least about 20,000 Gauss, preferably at least about 30,000 Gauss, and more preferably at least about 50,000 Gauss. It should be noted that 10,000 Gauss is equivalent to 1 tesla and these units can be used interchangeably.
  • Such ultra-high magnetic fluxes are in contrast to the above-described standard intensity magnetic separation at less than about 20,000 Gauss because such standard intensities are not sufficient to separate particles having both magnetic
  • superconducting electromagnetic field generators can be utilized.
  • an open gradient superconducting magnet can be used.
  • other types of magnetic separators may be used, as long as the required ultra-high magnetic flux can be obtained.
  • some rare earth magnets can now achieve a magnetic flux of up to about 28,000 Gauss.
  • typical impurities that can be removed during the magnetic separation step include shale and impure trona with interstitial dolomite and paramagnetic clay-type materials, which have higher magnetic susceptibilities than pure trona.
  • other impurities may be separated by the present process due to their association with the magnetic impurities.
  • any type of high intensity magnetic separator is suitable for use in the present invention. More particularly, either dry or wet high intensity magnetic separators can be used. Dry separation refers to any process in which dry particles are subjected to a high intensity magnetic field for separation of magnetic impurities. Wet separation refers to any process in which magnetic impurities are separated from, e.g., crystals of a saline mineral in a saturated brine in a high intensity magnetic field. Alternatively, the wet medium can include other liquids, such as an alcohol. Suitable high intensity magnetic separators can be of any known design.
  • magnetic separators can be of a type wherein a feedstream is fed in free fall in proximity to a high intensity magnet so that magnetic particles tend to migrate toward the magnet and non- magnetic particles do not. In this manner, as the particles are collected on either side of a splitter, the magnetic particles will physically separate from the nonmagnetic particles.
  • Fig. 9 a particular apparatus is illustrated.
  • the feedstream 10 is fed to a dropoff point 12 in free fall. At the dropoff point 12, the feedstream is in close proximity to the magnet 14. As the feedstream 10 falls, the magnetic particles 16 migrate toward the magnet 14 and the nonmagnetic particles 18 do not migrate toward the magnet 14.
  • the magnetic particles 16 fall on one side of the splitter, while the non-magnetic particles 18 fall on the other side of the splitter 20.
  • the horizontal distance between the dropoff point 12 and the magnet 14 defines the gap width 22.
  • the horizontal distance between the splitter and a point on the magnet face which is closest to the arc of the feedstream defines the splitter gap width 24.
  • the magnet angle 26 is defined by the angle between the bottom surface of the magnet and the horizontal.
  • Such a matrix can be made of any metal, such that in the presence of a magnetic flux, the metal can act as a magnet.
  • the metal can be in any configuration having a high surface area such as a wool or screen.
  • the magnetic particles in the feed stream will become attached to the matrix, whereas non-magnetic particles will migrate through the matrix and be removed from the bottom of the matrix.
  • This apparatus design is particularly well suited for fine particles, such as feedstreams having a particle size of less than 100 mesh.
  • a matrix in a vessel filled with a liquid is provided.
  • the matrix is subjected to the magnetic field of a high intensity magnet.
  • the liquid can be, for example, a saturated brine solution of a saline mineral.
  • a saturated brine recrystallization process such as is described in PCT application PCT/US96/00700, which is incorporated herein by reference in its entirety.
  • Such a stream can include the entire size range of crystals generated by the process or can be generated by separating large crystals from insoluble impurities and smaller crystals on a size separation basis.
  • the resulting stream of a saturated brine solution with insoluble impurities and small crystals can be treated by wet high intensity separation as described herein.
  • water can be added to such a stream to dissolve the small crystals therein.
  • the liquid medium can be an alcohol or other suitable medium.
  • this process includes subjecting a saline mineral containing ore to high intensity magnetic separation, whereby the impurity shortite is separated from the saline mineral.
  • the impurity pyrite is separated.
  • at least about 25 wt. % of the impurity is separated, more preferably at least about 50 wt. %, and most preferably at least about 75 wt. %.
  • magnetic separation at under about 20,000 Gauss is known. It has been appreciated, however, that there are limits on the effectiveness of such processes.
  • high intensity magnetic separation processes are more effective at separating pyrite from trona ore having a wide size fraction (e.g., 6x20 mesh or 20x100 mesh) than, for example, density separations such as air tabling. Therefore, a dry separation process using only high intensity separation could be more useful than a dry separation process using density separation when the desired product must be low in pyrite so long as moderate amounts of shortite can be tolerated. For example, it is contemplated by the present inventors that some amount of shortite may be desirable in soda ash in certain applications, such as the production of glass.
  • high intensity magnetic separations can be conducted in combination processes which also include density separations, electrostatic separations or recrystallization processes.
  • saline mineral particles of - 100 mesh can be efficiently separated by high intensity magnetic separation, as described above. It is generally recognized that conventional magnetic separation for such small particles is not effective. It is believed that static charges on the particles prevent effective separation between magnetic and non-magnetic particles. In addition, it is believed that such small particles do not efficiently separate because of a weak magnetic force. However, such small particles can be effectively separated by high intensity magnetic separation. High intensity magnetic separators using a matrix, such as steel wool, are believed to be particularly effective for such small particles. Without intending to be bound by theory, it is believed that the metal matrix functions to physically break up associations between magnetic and non-magnetic particles.
  • the metal matrix is able to dissipate static charges which otherwise hold such particles together.
  • at least about 25 wt.% of magnetic impurities are separated from the -100 mesh particles, more preferably at least about 50 wt.%, and most preferably at least about 75 wt.%.
  • the process of selectively separating low purity saline mineral from high purity saline mineral comprise performing colorimetric separation. More specifically, for example in the separation of trona, the low purity particles may be separated based upon their darker color than the high purity particles utilizing an automated colorimetric sorting process. Such a process may utilize a video imager in conjunction with appropriately- timed blasts of pressurized gas to deflect the darker colored particles away from the high purity particles.
  • the impurity stream from the selective separation step such as ultra-high intensity magnetic separation, can go through one or more scavenger steps to improve the overall recovery.
  • the scavenger step recovers a portion of the impurity stream from the rougher pass through magnetic separation and combines it with the above-described recovered stream or recycles it to the process with or without further size reduction to increase the overall recovery of the magnetic separation step. Furthermore, the recovered stream from magnetic separation can go through one or more magnetic cleaning steps to further remove impurities from the recovered stream and improve the purity of the final product.
  • the present process may further include removing impurities from the ore containing saline minerals by a density separation method.
  • Density separation methods are based on subjecting an ore to conditions such that materials of different densities physically separate from each other. Thereby, certain impurities having a different density than the desired saline mineral can be separated.
  • the density separation step of the present invention is most preferably a dry process; however, wet density separation processes, such as heavy media separation, can be used as well. In dry density separation processes, the need for processing in a saturated brine solution, solid/brine separation, and drying of the product is eliminated. Consequently, dry processes according to the present invention tend to be cheaper and less complex than wet processes. T ⁇ ny known density separation technique could be used for this step of the present invention, including air tabling or dry jigging.
  • the ratio of the largest particle within a fraction of the smallest particle within that fraction should be relatively small. Without such a small ratio of particle size distribution, the differences in particle sizes could tend to dominate the separation process, thereby reducing the density separation effect.
  • the particle size distribution ratio should be about 3.0 or less, preferably about 2.8 or less, and more preferably about 2.2 or less.
  • density separation is conducted by subjecting the ore to conditions such that materials of different densities separate from each other.
  • the mineral stream having materials of varying densities is separated by a rougher pass into a denser and a lighter stream, or into more than two streams of varying densities.
  • the separation is made at a specific gravity of about 2.3, and trona is recovered in the lighter stream.
  • the purity of a saline mineral recovered from density separation can be increased by reducing the weight recovery of the recovered stream from the feed stream. At lower weight recoveries, the recovered stream will have a higher purity, but the rougher pass will also have a reduced yield because more of the desired saline mineral will report to the impurity stream.
  • Such a "high purity" process may be beneficial in that it requires less subsequent processing (e.g., separation) of the ore and, in addition, may be of higher value because it can be used in other applications where high purity saline minerals are required.
  • the impurity stream from density separation can go through one or more scavenger density separation step(s) to recover additional saline mineral to improve the overall recovery.
  • the scavenger separation is similar to the above-described density separation step.
  • the scavenger step treats the impurity stream from the rougher pass and recovers a portion of the saline mineral therefrom.
  • the recovered scavenger portion is combined with the above-described recovered stream to increase the overall recovery from density separation, or recycles it to other steps in the process, with or without further size reduction.
  • the recovered stream from the rougher pass density separation can go through one or more cleaning density separation steps to further remove impurities from the recovered stream and improve the purity of the final product.
  • the cleaning step is similar to the above-described density separation process in that impurities are removed from the stream by density separation.
  • the feed stream into those passes can undergo further size reduction, if desired, for example, to achieve higher liberation.
  • impurities that are removed during the density separation step of the present invention include shortite, having a density of 2.6, dolomite, having a density of 2.8 - 2.9 and pyrite, having a density of 5.0. Each of these is separable from the trona ore because of differences in density from trona.
  • the density separation step can remove at least about 10 wt.% and more preferably, about 50 wt.%, and most preferably, about 90 wt.% of the heavy impurity.
  • impurities removed during the density separation process can be recovered as a product for commercial use.
  • the impurities removed during the air tabling step can comprise as much as 90% shortite.
  • Such shortite may be acceptable, for example, for certain applications where it can be used for neutralization of acids or removal of sulfur from flue gases.
  • potentially valuable heavy minerals may be present. Such minerals can be separated by the method and recovered.
  • process steps could be performed along with other process steps.
  • process steps can include low or standard intensity magnetic separation. electrostatic separation, or any other suitable separation technique.
  • process steps could be performed in any order.
  • calcination can be conducted at any point in the sequence of process steps and preferably is conducted prior to any magnetic or density separation steps.
  • the saline mineral-containing ore can be crushed to achieve liberation of impurities prior to the separation steps.
  • the crushing step of the present invention can be accomplished by any conventional technique, including impact crushing (e.g., cage or hammer mills), jaw crushing, roll crushing, cone crushing, autogenous crushing or semi- autogenous crushing. Autogenous and semi-autogenous crushing are particularly beneficial because the coarse particles of ore partially act as the crushing medium. Moreover, because saline minerals are typically soft, these methods are suitable for use in the present process. In addition, these two crushing methods allow for the continuous removal of crushed material and high grade potentially saleable dust.
  • acceptable liberation for the present process can be achieved by crushing the ore to at least about 6 mesh.
  • the particle size range after crushing is from about 6 to about 100 mesh and, more preferably, from about 6 to about 65 mesh.
  • the ore is sized into size fractions prior to the separation steps. Each size fraction is subsequently processed separately.
  • the narrower the range of particle size within a fraction the higher the efficiency of removal of impurities. This is particularly true if air tabling is used as a density separation step, wherein small particle size distribution ratios are desired.
  • a larger number of fractions will increase the efficiency, but may increase the cost of the overall process.
  • the use of from 1 to 10 fractions has been found to be acceptable.
  • the number of fractions is from 4 to 10 and, more preferably, the number of fractions is 8. Any conventional sizing technique can be used for the present process, including screening or air classification.
  • the fractions typically have the following particle size ranges: 6 to 8 mesh; 8 to 10 mesh; 10 to 14 mesh; 14 to 20 mesh; 20 to 28 mesh; 28 to 35 mesh; 35 to 48 mesh; 48 to 65 mesh (Tyler mesh) .
  • the particle size distribution ratio for each fraction is about 1.42. It should be noted that a smaller number of size fractions, including only one size fraction (such as 6 mesh x 100 mesh or 6 mesh x 0) or two size fractions (such as 6 mesh by 20 mesh and 20 mesh by 0) , can be used for high intensity magnetic separations. Without intending to be bound by theory, it is believed that the effects of particle size are reduced under high intensity magnetic separator apparatus designs.
  • high intensity magnetic separation can be conducted on a size fraction from 6 or 8 mesh by 20, 65 or 100 mesh.
  • the different size fractions can be treated with high intensity magnetic separations using different equipment.
  • the two larger size fractions are preferably treated using an apparatus in which particles free fall while subject to a high intensity magnet and are collected on either side of a splitter.
  • Such an apparatus is also known as an open gradient magnetic separator ("OGMS") .
  • OGMS open gradient magnetic separator
  • the smallest size fraction is preferably treated by a high intensity magnetic separator having a metal matrix.
  • the ore is dried prior to the separation processes set forth above.
  • the drying step removes surface moisture from the ore to better enable the ore to be separated. Drying can be accomplished by any conventional mineral drying technique, including rotary kiln, fluid bed or air drying.
  • the ore can be dried to less than about 2%, and preferably less than about 1% surface moisture content.
  • it is preferred that the saline mineral is not raised to such a temperature for such a period of time that it is calcined. In the case of trona, the drying temperature should remain below about 40 degrees centigrade to avoid calcination.
  • a de-dusting step is added to the basic beneficiation process to remove fines before the selective separation step (e.g., magnetic separation).
  • a de-dusting step can be conducted before, during or after one or more of the crushing and sizing steps, but preferably before the electrostatic separation, magnetic separation and density separation steps.
  • the fines produced during the processing of trona are relatively high purity trona and are useful in several industrial applications.
  • trona recovered by de-dusting can have a purity of greater than about 94%, preferably greater than about 96% and more preferably greater than about 98%. Fines can be collected in de-dusting steps by use of a baghouse, or other conventional filtering device, and sold as purified trona without further processing.
  • the magnetic separation achieved by any magnetic separation step of the present invention can be improved by subjecting the ore that is being processed to a preliminary magnetic field prior to separation and subsequently separating a portion of impurities from the ore by magnetic separation.
  • a preliminary magnetic field prior to separation
  • subsequently separating a portion of impurities from the ore by magnetic separation it is believed that by subjecting particles being processed to a preliminary magnetic field before physical separation of magnetic from non-magnetic particles, the magnetic tractive force on particles during magnetic separation is greater. In this manner, more efficient separations can be achieved during magnetic separation steps.
  • preliminary magnetic field refers to a magnetic field to which a feed stream being processed is subjected prior to physical separation of magnetic from non-magnetic particles.
  • a feed stream being processed can be subjected to a preliminary magnetic field using conventional apparatus known to those in the art. For example, a feed stream can be transported along a conveyor belt and subjected to a magnetic field during linear transport on the conveyor belt. Subsequently, particles will reach the end of the conveyor belt and drop off of the conveyor belt while being subjected to the primary magnetic field for separation.
  • the preliminary magnetic field typically has a magnetic flux density of greater than about 2000 Gauss, more preferably greater than about 5000 Gauss, and most preferably greater than about 20,000 Gauss.
  • the step of subjecting particles to a preliminary magnetic field is conducted for at least about 1 second, more preferably at least about 30 seconds, and most preferably at least about 60 seconds.
  • the positive effect of a preliminary magnetic field can be further enhanced by increased temperatures. More particularly, the process is conducted at temperatures of at least about 100°C, more preferably 150°C, and most preferably 200°C.
  • a saline mineral can be calcined prior to magnetic separation. More particularly, in one aspect of this embodiment, the saline mineral is calcined in an inert atmosphere prior to separating impurities from the ore. In a second aspect of this embodiment, the saline mineral is calcined in an oxidizing atmosphere at a temperature of greater than about 150°C prior to separating impurities from the ore. In this embodiment of the present invention, it has been surprisingly found that by calcination under the conditions identified above (i.e., an inert atmosphere or an oxidizing atmosphere at high temperature) , the subsequent magnetic separation is more efficient than in the absence of such calcining conditions.
  • an inert atmosphere refers to a non-oxidizing atmosphere (i.e., an atmosphere substantially free of oxygen) .
  • an inert atmosphere is any non-oxygen containing atmosphere and in particular, can comprise carbon dioxide, nitrogen, or water vapor.
  • carbon dioxide used for providing an inert atmosphere for calcination purposes can be carbon dioxide which is recycled from an exhaust stream from the calcination process.
  • the byproducts of calcination include carbon dioxide and water.
  • the water can be condensed from the exhaust stream and the carbon dioxide recycled for use as the calcination gas, for example, in a fluidizing bed.
  • the calcination temperatures typically range between about 43°C and about 400°C, more preferably between about 100°C and about 350°C, and most preferably between about 150°C and about 260°C.
  • the atmosphere most typically includes air but can include other oxygen containing gases as well.
  • the calcination temperature in this aspect of the invention is at least about 150°C, more preferably at least about 250°C, and most preferably at least about 500°C.
  • the saline mineral containing ore is then subjected to magnetic separation.
  • magnetic separation can include high intensity magnetic separation as generally described herein, or conventional intensity magnetic separation as described herein and otherwise described in the art.
  • the process of calcining saline mineral in an inert atmosphere or in an oxidizing atmosphere at a high temperature followed by magnetic separation can also include the step of subjecting the calcined ore to a preliminary magnetic field prior to magnetic separation, as generally described above.
  • a further embodiment of the present invention includes a process for the purification of saline mineral by magnetic separation in an ore comprising saline mineral and impurities.
  • the magnetic separation is conducted in a first magnetic field having positions of higher intensity and lower intensity.
  • the process includes pre-aligning the ore on a surface with respect to one or more of the positions of higher intensity of the first magnetic field before separation of impurities and separating a first portion of impurities from the ore by magnetic separation in the first magnetic field.
  • higher efficiency of magnetic separation is achieved because the ore is conducted through the first magnetic field at the positions of highest magnetic intensity. Therefore, magnetically susceptible particles are subject to a higher magnetic tractive force and thereby are more readily separated.
  • the magnetic separation is conducted by feeding ore onto a conveyor belt which then transports the ore toward one end of the conveyor belt.
  • the magnet creating the first magnetic field is positioned in the rollers at the end of the belt towards which the ore is transported. In this manner, there will be one or more positions along the length of the roller which have higher or maximum intensity of magnetic force compared to other portions of the roller.
  • the step of pre-aligning can be accomplished by a variety of means.
  • pre-alignment can be accomplished by subjecting the ore, for alignment purposes only, to a second magnetic field in the vicinity of the portion of the belt at which the ore is fed onto the belt.
  • alignment can be accomplished by simple mechanical means of feeding the ore onto the belt at one or more discrete locations across the width of the belt such that as the belt is advanced, a line of ore is laid down on the belt.
  • alignment is accomplished by aligning the discrete feed discharge point with the one or more positions of higher intensity of the first magnetic field.
  • the original 20x35 fraction comprised 94.01% soluble matter (i.e., trona) and 5.99% insoluble matter (i.e., impurities).
  • the 20x35 fraction was subjected to standard magnetic separation utilizing a rare earth separator at its maximum intensity of less than about 20,000 Gauss. The standard magnetic separation step resulted in removal of 3.0% of the weight of the original sample in a magnetic fraction, and the remaining non-magnetic fraction comprised 95.7% trona.
  • the non-magnetic fraction from the previous step was then divided into seven (7) samples to be used in eight (8) tests (test 8 was performed on the output from test 7) .
  • Each of the eight (8) tests included a two-step separation process: (1) magnetic separation at 28,000 Gauss; and (2) density separation at 2.3 specific gravity on the nonmagnetic fraction from the previous step.
  • the density separation was performed with a heavy liquid which simulates density separation with commercial air tables.
  • the heavy liquid used was a mixture of acetylene tetrabromide and kerosene.
  • Each of the first seven tests had essentially identical feed compositions, and the input to the eighth test was the output from the seventh test.
  • the major difference between the tests was the depth of the impurity cut. In general, the deeper the cut, the higher the purity and the lower the recovery.
  • Table 3 A summary of the tests results is provided in Table 3.
  • the Table gives the weight recovery of the overall process using the original sample as 100% (Weight, %), the amount of impurities in the final product (% H 2 0 Insol) , the amount of iron as Fe 2 0 3 in the final product (Fe 2 0 3 , %) , and the amount of the original trona remaining in the final product (Trona Dist., %) .
  • test #4 resulted in excellent purity (98.17%), which is uncharacteristic of most dry separation processes, while achieving moderate recovery (67.1%).
  • Test #1 resulted in outstanding recovery (95.0%) while still achieving a purity (97.2%) in excess of 97%.
  • Test #8 exceeds 98% purity, while still having a recovery greater than 80%. This was accomplished by performing a two-stage ultra-high intensity magnetic separation. More specifically, the non-magnetic fraction from test #7 was run through the ultra-high intensity magnetic separation process a second time. The result is a process which gives a purity almost as good as the best results (test #4), with a satisfactory recovery.
  • the samples were all less than 1 mm in diameter.
  • the testing was done on a vibrating sample magnetometer having a maximum field of 12 tesla. All data were gathered at room temperature, with a time constant of 0.3 seconds and ramping the magnetic field at 20 Oersted/sec. (to 0.4 tesla) or 150 Oersted/sec. (to 2 tesla) . Other than for strongly magnetic samples (such as P-5) , an appropriate background subtraction was performed.
  • the materials were weighed and wrapped with PTFE tape which was then formed into an approximately spherical ball before packing into the sample holder. The resulting ball of material was approximately 5 mm in diameter.
  • This example illustrates the effect of calcination temperature on subsequent magnetic separation of impurities from trona ore.
  • Trona ore was treated, in both air and in C0 2 , by calcination at 150° C, 300° C, 450° C, or 600° C.
  • the trona ore was treated by magnetic separation.
  • a control was run on trona with no calcining.
  • Magnetic separation was conducted on a rare earth roll magnet at about 20,000 Gauss.
  • the magnetic and nonmagnetic fractions were then assayed for water insoluble content (i.e., impurities) and for water soluble content (i.e., sodium carbonate values) .
  • the magnetic and non-magnetic fractions were also assayed for total iron.
  • Table 6 Calcination in Air
  • Table 7 Calcination in C0 2
  • This example illustrates magnetic separation with high intensity magnetic separation of impurities from calcined trona which had previously been treated by two passes of over a rare earth magnetic separator.
  • the initial product was prepared by calcining trona and passing the calcined product over a rare earth magnetic separator to yield a magnetic fraction and a non-magnetic fraction.
  • the non-magnetic fraction was again passed over a rare earth magnetic separator to yield a magnetic fraction and a non-magnetic fraction.
  • the non-magnetic fraction from the second pass was used as the initial feed for this experiment.
  • the feed was tested using an OGMS superconducting magnet set at 2 tesla. Four runs were conducted, varying the feed rate, magnet angle and feed gap. The parameters for each run are listed below in Table 8.
  • an OGMS superconducting magnetic separator improved the purification of a non-magnetic fraction from a rare earth magnetic separator with a high recovery. Moreover, the mineralogical evaluation of the sample showed that even at 2 tesla, some pyrite and shortite showed up in the magnetic fraction.
  • the use of high intensity magnetic separation provided improved separation of impurities compared to the use of rare earth magnetic separation with the same size fraction and magnetic strength.
  • the use of an OGMS superconducting magnetic separator has the advantage of eliminating centrifugal forces found with conventional roll type magnetic separators. Centrifugal forces can cause particles to report to the far side of the splitter due to mass considerations rather than magnetic susceptibility.
  • This example illustrates the magnetic separation of impurities from either trona or calcined trona using an OGMS.
  • the experimental setup varied the gap width and the splitter gap width.
  • the gap width is the horizontal distance between the drop-off point of the feed and the magnet.
  • the splitter gap width is the horizontal distance between the splitter and a point on the magnet face which is closest to the arc of the feedstream.
  • the separations were conducted at a magnetic field strength of 4 tesla, with a magnet angle of 11°.
  • the percentage of pyrite in the feed was calculated and, for some runs, determined by analysis.
  • the percent pyrite in the non-magnetic fraction was analyzed.
  • the weight-percent recovery in the non-magnetic fraction was calculated, as was the weight-percent recovery of soluble material in the non-magnetic fraction.
  • This example illustrates the use of magnetic separation of impurities from soda ash or trona using a superconducting magnet with a metal matrix to remove impurities from a dry feedstream.
  • the feedstream was introduced at a feed rate of 25 cmVs.
  • the magnetic field was set at 5 tesla.
  • the matrix material in this test was an expanded metal matrix having a matrix size of 1/4 inch. Non-magnetic material exited the bottom of the unit while the magnetic fraction was held in the matrix.
  • Run 1 was conducted to determine the effect of vibration on the flow of material through the magnetic separator.
  • the frequency of a vibrator of the matrix was varied from 40 HZ to 25 HZ, and then 10 HZ. Approximately 100 g of feed was fed through at each frequency setting. The non-magnetic fraction from each run was collected and the final magnetic fraction from the total of the three settings was also collected.
  • Run 2 was conducted to evaluate the capacity of the matrix and how the purity of the non-magnetic fraction was affected as the matrix was loaded up with a magnetic fraction.
  • the magnetic separator was fed 100 g of feedstream at a time until 1000 g had been run through the matrix without removing any magnetic fraction from the matrix. After the last 100 g had been run through the matrix, the magnetic fraction was removed from the matrix by ramping down the magnetic coil in tesla increments. The first sample was produced by reducing the field from 5 tesla to 3 tesla. The next three samples were recovered by reducing the magnetic field from 3 to 2 tesla, from 2 to 1 tesla, and from 1 to 0 tesla. A final magnetic sample was recovered by shaking the unit at 0 tesla.
  • Run 3 was conducted to determine whether a second pass through the magnetic separator would improve the purity of the non-magnetic fraction. A feedstream of about 150 g was used.
  • Run 4 was similar to Run 2, except that calcined trona was used instead of trona. In addition, instead of ten portions of 100 g, Run 4 included five samples of 160 g. Further, the magnetic samples included a division of the 5-3 tesla sample into a 5-4 tesla and a 4-3 tesla sample.
  • Run 5 was conducted to confirm the results obtained from Run 4 and determine repeatability of the test method.
  • Run 6 used the heavy portion of a density separation of calcined trona.
  • the heavy portion of such a density separation included a large percentage of shortite, shale and pyrite.
  • the feed material is enriched in these impurities.
  • a feedstream of 200 g of this material was used.
  • the matrix became blocked as a result of the coarse nature of the feed material.
  • Run 7 repeated Run 6 except that a higher frequency on the vibrator was used to allow all of the feed material to pass through the matrix.
  • Run 8 repeated Run 7 but less feed material (i.e., 100 g of feed material) was used. After the first pass, the magnetic fraction was removed from the matrix before running the nonmagnetic fraction through for a second pass.
  • Run 9 was conducted to evaluate the effect of magnetic separation on very fine material. Due to the poor flow characteristics of this feed material, the matrix became blocked.
  • the samples from each of the runs were weighed and analyzed for insoluble material.
  • the insoluble material was analyzed by microscopic examination and by chemical analysis .
  • the analytical results for this example are shown in Tables 13 and 14. These test results show that using high intensity magnetic separation with a metal matrix makes separations of finer size fractions possible.
  • Conventional technology only permits narrow size ranges to be separated to a level of purity that was achieved with use of high intensity magnetic separation in a matrix material using a large size range (20X100 mesh) .
  • the separation of material of less than 150 mesh is now possible when conventional rare earth and induced roll magnetic separation cannot process those size fractions.
  • This example illustrates the use of magnetic separation using a superconducting magnetic separator process having a metal matrix for capture of particles wherein the feedstream is a wet slurry.
  • the feed material for four test runs of this example was produced by dissolving about 6, 000 g of soda ash prepared by calcining trona in 4 gallons of warm water. This slurry was screened at 100 mesh to remove the +100 mesh insolubles. A fifth test run slurry was made by dissolving filter cake from a sodium carbonate recrystallization process to make a saturated -100 mesh insolubles slurry.
  • the feed materials for this example are shown in Table 15.
  • test parameters in terms of feed rate, magnetic field and matrix material are shown in Table 16.
  • test material was fed into the unit and flowed through the matrix in a 5 tesla magnetic field. No vibrator of the apparatus was used. The non-magnetic material exited the bottom of the unit while the magnetic fraction was held in the matrix. The current was ramped down to 0, reducing the magnetic field to 0. When the magnetic field was at 0, the matrix was flushed with water to remove any magnetic material that was still adhering to the matrix and internal ledges. It was necessary to preheat the magnetic separator unit and matrix material to prevent crystals from forming in the matrix. The recovered samples were diluted with water to remove any crystals that formed during the run and then filtered on 1 micron filter paper to remove insolubles.
  • Run 1 a 2.5 mm square wire matrix was used.
  • Run 2 a matrix composed of alternating pieces of 1.7 mm and 1.0 mm square wire material was used.
  • Run 3 the non-magnetic product from Run 2 was used as the feed.
  • the matrix was changed to a 110 micron steel wool.
  • Run 4 a 2.5 mm square wire material was used as a matrix.
  • the feed material included the +100 mesh insolubles, that had previously been screened out of the slurry in Runs 1, 2 and 3. The matrix plugged at the beginning of the run.
  • Run 5 included alternating pieces of a 1.7 mm and a 1.0 mm square wire material as the matrix.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Abstract

L'invention concerne des procédés servant à purifier des minéraux salins au moyen d'une séparation magnétique. Ces minéraux salins peuvent comprendre, en particulier, du sesquicarbonate de sodium, des borates, de la potasse, des sulfates, des nitrates et des chlorures. Cette séparation magnétique peut consister en une séparation magnétique à intensité élevée qu'on peut effectuer à une induction magnétique supérieure à 2 tesla et jusqu'à une induction magnétique supérieure à 5 tesla. D'autres modes de réalisation de l'invention consistent à calciner le minerai salin dans une atmosphère inerte ou dans une atmosphère contenant de l'oxygène à température élevée préalablement à la séparation magnétique. Un autre mode de réalisation consiste à pré-aligner des particules sur une surface servant à aligner les particules présentant une force magnétique élevée pendant une étape de séparation magnétique. L'invention concerne également différents modes de réalisation de séparation magnétique, dont l'un consiste à soumettre un minerai à un champ magnétique préliminaire avant la séparation magnétique.
PCT/US1998/003349 1997-02-21 1998-02-20 Traitement de mineraux salins WO1998036842A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU64373/98A AU6437398A (en) 1997-02-21 1998-02-20 Beneficiation of saline minerals

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US3875997P 1997-02-21 1997-02-21
US60/038,759 1997-02-21

Publications (1)

Publication Number Publication Date
WO1998036842A1 true WO1998036842A1 (fr) 1998-08-27

Family

ID=21901733

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1998/003349 WO1998036842A1 (fr) 1997-02-21 1998-02-20 Traitement de mineraux salins

Country Status (2)

Country Link
AU (1) AU6437398A (fr)
WO (1) WO1998036842A1 (fr)

Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1371825A (en) * 1920-03-16 1921-03-15 Uhlig Franz Magnetic separator
US2708034A (en) * 1953-05-05 1955-05-10 Pettibone Mulliken Corp Magnetic separator for use in connection with an endless conveyor
US2990124A (en) * 1957-08-16 1961-06-27 Cottrell Res Inc System for separating magnetic susceptible particles
US3022956A (en) * 1958-04-14 1962-02-27 Int Minerals & Chem Corp Beneficiation of ores
US3276581A (en) * 1963-11-22 1966-10-04 Eriez Mfg Co In line belt type magnetic separator
US3860514A (en) * 1970-09-21 1975-01-14 Ethyl Corp Method of beneficiating alumina-silica ores
US3936372A (en) * 1971-11-24 1976-02-03 Financial Mining-Industrial And Shipping Corporation Method for beneficiation of magnesite ore
US3966590A (en) * 1974-09-20 1976-06-29 The United States Of America As Represented By The Secretary Of The Interior Magnetic ore separator
US4236640A (en) * 1978-12-21 1980-12-02 The Superior Oil Company Separation of nahcolite from oil shale by infrared sorting
US4324577A (en) * 1980-02-25 1982-04-13 Beker Industries, Inc. Method and apparatus for beneficiating phosphate ores
US4341744A (en) * 1979-01-22 1982-07-27 Stauffer Chemical Company Soda ash production
US4375454A (en) * 1980-12-12 1983-03-01 Intermountain Research And Development Corporation Electrostatic enrichment of trona and nahcolite ores
US4388179A (en) * 1980-11-24 1983-06-14 Chevron Research Company Magnetic separation of mineral particles from shale oil
US4874508A (en) * 1988-01-19 1989-10-17 Magnetics North, Inc. Magnetic separator

Patent Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1371825A (en) * 1920-03-16 1921-03-15 Uhlig Franz Magnetic separator
US2708034A (en) * 1953-05-05 1955-05-10 Pettibone Mulliken Corp Magnetic separator for use in connection with an endless conveyor
US2990124A (en) * 1957-08-16 1961-06-27 Cottrell Res Inc System for separating magnetic susceptible particles
US3022956A (en) * 1958-04-14 1962-02-27 Int Minerals & Chem Corp Beneficiation of ores
US3276581A (en) * 1963-11-22 1966-10-04 Eriez Mfg Co In line belt type magnetic separator
US3860514A (en) * 1970-09-21 1975-01-14 Ethyl Corp Method of beneficiating alumina-silica ores
US3936372A (en) * 1971-11-24 1976-02-03 Financial Mining-Industrial And Shipping Corporation Method for beneficiation of magnesite ore
US3966590A (en) * 1974-09-20 1976-06-29 The United States Of America As Represented By The Secretary Of The Interior Magnetic ore separator
US4236640A (en) * 1978-12-21 1980-12-02 The Superior Oil Company Separation of nahcolite from oil shale by infrared sorting
US4341744A (en) * 1979-01-22 1982-07-27 Stauffer Chemical Company Soda ash production
US4324577A (en) * 1980-02-25 1982-04-13 Beker Industries, Inc. Method and apparatus for beneficiating phosphate ores
US4388179A (en) * 1980-11-24 1983-06-14 Chevron Research Company Magnetic separation of mineral particles from shale oil
US4375454A (en) * 1980-12-12 1983-03-01 Intermountain Research And Development Corporation Electrostatic enrichment of trona and nahcolite ores
US4874508A (en) * 1988-01-19 1989-10-17 Magnetics North, Inc. Magnetic separator

Also Published As

Publication number Publication date
AU6437398A (en) 1998-09-09

Similar Documents

Publication Publication Date Title
CA2309611C (fr) Procede de valorisation d'un minerai de fer au moyen de plusieurs separateurs magnetiques
US5470554A (en) Benefication of saline minerals
US5911959A (en) Method for purification and production of saline minerals from trona
CN108514949B (zh) 一种细粒钛铁矿的回收方法
US20240376563A1 (en) Process for dry beneficiation of bauxite minerals by electrostatic segregation
CN120457225A (zh) 用于锂回收的锂辉石富集
US6173840B1 (en) Beneficiation of saline minerals
RU2296624C2 (ru) Способ переработки золошлаковых отходов тепловых электростанций
US5736113A (en) Method for beneficiation of trona
US20110272503A1 (en) Systems and processes for producing high purity trona
WO1997025448A9 (fr) Methode d'enrichissement du trona
WO2006053873A1 (fr) Procede de separation magnetique de trona
KR20230162658A (ko) 스포듀민으로부터의 리튬 회수
Yehia et al. Recovery and utilization of iron and carbon values from blast furnace flue dust
JPS60135533A (ja) ステンレススラグの処理方法
US7770735B2 (en) Magnetic separation process for trona
FI93974C (fi) Menetelmä sulfidisten, vaikeasti sulatettavien nikkelirikasteiden tai vastaavien seosten hyödyntämiseksi
WO1998036842A1 (fr) Traitement de mineraux salins
Ozdemir et al. Production of trona concentrates using high-intensity dry magnetic separation followed by flotation
Atasoy The wet high intensity magnetic separation of magnesite ore waste
Durgut et al. Effect of blunging process on purification of halloysite ore from ferrous impurities by dry magnetic separation
Bondarenko et al. The process of beneficiation of fine chrome sludges on concentration tables
CN107470012A (zh) 一种磷灰石纯矿物的提取方法
RU2283183C1 (ru) Способ обогащения сидеритовых руд
WO1996022398A1 (fr) Procede de purification de mineraux salins

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AL AM AT AU AZ BA BB BG BR BY CA CH CN CU CZ DE DK EE ES FI GB GE GH GM GW HU ID IL IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MD MG MK MN MW MX NO NZ PL PT RO RU SD SE SG SI SK SL TJ TM TR TT UA UG UZ VN YU ZW

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): GH GM KE LS MW SD SZ UG ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH DE DK ES FI FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase

Ref country code: CA