PRODUCTION OF METAL PRODUCTS DIRECTLY FROM UNDERGROUND ORE DEPOSITS

Abstract

A process for producing metal compounds directly from underground mineral deposits including steps of forming a borehole at a site into a mineral deposit containing metal compounds, inserting a slurry-forming device having a nozzle into the borehole adapted to direct pressurized water through the nozzle into the mineral deposit, supplying pressured water through the nozzle into the mineral deposit forming a mineral slurry containing metal compounds, extracting the mineral slurry containing metal compounds through the borehole, leaching the mineral slurry converting the metal compounds to a soluble form in a leach solution, and removing metals and metal compounds by treating the leach solution with an extraction treatment removing the metal products. Steps of leaching the mineral slurry and removing metal products are performed at a location remote from the borehole site. In one alternative, the step of removing metal products from mineral slurry is accomplished by pyrometallurgical processes.

Description

This application is a continuation of U.S. patent application Ser. No. 12/695,045 filed Jan. 27, 2010, which claims the benefit of U.S. Patent Application 61/147,502, filed on Jan. 27, 2009, which is incorporated herein by reference.

BACKGROUND AND SUMMARY

Mineral deposits containing metal compounds from which metal products can be made are presently found in various geographic locations and in ore veins of quite varying depth. The mineral deposits in the past have been removed from such ore veins either by open pit mining or shaft mining. In locations where the mineral deposit is located close to the surface of the earth, the overburden is removed by excavation to reach the ore deposit and the ore removed by open pit mining. This type of mining typically involves using very large and expensive draglines or other excavating equipment to remove the overburden and the ore deposit. Where the ore vein is deeper in the earth so that it is not practical to remove the overburden to reach the mineral deposits, shaft mines are employed by digging tunnels and shafts so that miners and equipment can reach the ore deposit, and the ore deposit removed by the miners and equipment through the tunnels and/or shafts.

With either open pit or shaft mining, the mineral deposit must be of such depth to make it economical to either remove the overburden or dig the tunnel and shafts to reach the ore deposit. Additionally, ore veins underground vary in depth along their run, and as a result, the mining only continues to where the depth of the ore vein narrows to the point where the overburden can no longer be economically removed or the ore deposit can no longer be reached underground with miners and available equipment. These factors have greatly limited the ore deposits that can be commercially removed from the ground.

Furthermore, open pit mining and shaft mining have been criticized for both immediate and ongoing environmental concerns, including their impact on erosion, surface and underground water quality, and the aesthetic impact on mined and surrounding landscape and land values. Further, many mineral deposits exist beneath areas that are environmentally sensitive areas such as national or state parks, pristine lakes, recreational areas, urban areas, wetlands, and pristine and used surface areas where permits cannot presently be obtained to remove underground mineral deposits. These latter mineral deposits have been before now inaccessible because the prior methods available for removing the mineral deposits impacted the local environment and/or potentially damaged the natural or manmade resource above the mineral deposit. Increasing awareness of environmental concerns and desire to maintain various natural resources alone has caused fewer permits for removal of desired mineral deposits to be granted.

Additionally, whether open pit or shaft mining is employed, ore removed from underground mineral deposits had to be processed to remove desired metal or metal compounds at the mine site. In the past, transporting ores from the mine site was not possible for a commercially viable mining operation. Such processing of the ore from the mineral deposit exacerbated the environmental impact by the need to process the removed ore at the mine site. Processing of the ore at the mine site may involve separation of the useful metals and metal compounds from undesirable minerals also present in the mineral deposit with environmentally sensitive chemicals. Such processing also likely involved storage or disposal of various mine wastes at the mine site on an ongoing basis.

Accordingly, there remains a need for a method of producing metals and metal compounds from mineral deposits that were not previously commercial accessible because of the costs of reaching the ore vein, or that the nature of the land areas under which the ore vein lie made it environmental impermissible to remove the desired ore deposit.

Disclosed herein is a process for producing metal product directly from mineral deposits without open pit or shaft mining. This process is particularly useful in removing manganese-bearing deposits and other similar mineral deposits where the ore in the mineral deposit can be formed directly into a slurry by injection of water under pressure into the mineral deposit. In some cases, explosives or other means may be used in addition to the water pressure to break up the mineral deposit and facilitate removal to the mineral deposit in a water slurry through a borehole. The method also includes transporting to a remote location, as well as processing the formed and extracted water slurry at the remote location to form a product of metal compounds that can be further processed in a furnace or other facility.

For removal and processing of metal-bearing ore deposits from an environmentally sensitive location, the present method may comprise the steps of:

(a) forming a borehole from an accessible site into a mineral deposit containing metal compounds;

(b) inserting a slurry-forming device having a nozzle into the borehole adapted to direct pressurized water through the nozzle into the mineral deposit;

(c) supplying pressured water through the nozzle of the slurry-forming device into the mineral deposit forming a mineral slurry containing the metal compounds from the mineral deposit;

(d) extracting the mineral slurry containing the metal compounds through the borehole;

(e) transporting the mineral slurry away from the borehole to a location remote from the site;

(f) leaching the extracted mineral slurry at the remote location to convert the metal compounds to a soluble form in a leach solution; and

(g) removing metal compounds by treating the leach solution with an extraction treatment adapted to remove the metal compounds.

Additionally, in the transporting step the mineral slurry may be transported in removed form or after partial water removal. This transporting step is particularly useful in removing mineral deposits from environmental sensitive areas and, in any event, may be used in allowing the leaching and removal steps to be performed at one location on mineral slurries extracted through a number of boreholes in different parts of the same or different ore veins. The mineral slurry may be transported by at least one device selected from a group consisting of truck, rail, and pipeline to the remote location where the leaching and removal steps are performed.

The present process for producing metal compounds may be used for mining mineral deposit containing oxides of at least one metal selected from the group consisting of manganese, cobalt, copper, iron, chromium, lead, nickel, magnesium, platinum, palladium, gold, silver, aluminum, lithium, molybdenum, tungsten, uranium, vanadium, zinc, and zirconium.

The pressure of the injected water may be any desirable or useful pressure effective to form the mineral slurry of the manganese mineral deposit in a particular ore vein. The water pressure, for example, may be between 1000 and 2500 pounds per square inch (psi). The method is useful with ore veins from narrow depths up to several hundred feet in depth. Similarly, the method is commercially feasible with ore veins that vary widely in depth, thus permitting removing of ore from mineral deposits not previously possible and to an extent not previously possible.

The present method may be used for producing metal products directly from underground mineral deposits that are capable of being broken up by the slurry-forming device to create the mineral slurry. The method may involve, where desired and permissible, detonating explosives or using other auxiliary devices in the underground mineral deposit to assist in breaking-up the ore deposit and forming the water slurry.

In one alternative, the method may be used also by forming more than one borehole where the first borehole is generally vertical from the surface into the mineral deposit and the second borehole is slanted so as to intersect the first bore in the ore deposit. The slurry-forming device can be inserted through the second slant borehole to increase the range to which water can be injected under pressure into the ore body, and the formed mineral slurry can be removed from the ore deposit through the first bore hole. This embodiment may increase the range of the removal of ore from certain ore veins through a borehole site. Alternatively, the first borehole may be partially predrilled in a slant borehole to allow the range of removal of mineral deposits from the ore vein from a given borehole site.

The method may include, before leaching, and either before or after performance of the transporting step, a step of grinding particulate matter in the extracted mineral slurry to a particle size of about 80% smaller than 100 mesh, or about 80% smaller than 200 mesh.

The step of leaching the mineral slurry may include leaching the mineral slurry with acids to put desired metal compound into solution. For example, with extracted mineral slurry of the metal oxides of manganese, the acid may be sulfurous acid (H₂SO₃) formed by dissolving SO₂ in water. Additionally, the leach solution may include at least one reducing agent selected from a group consisting of SO₂, carbon, reducing sugar, molasses, and a combination of two or more thereof. The leach solution may have a pH of 3 or below.

After the step of leaching the mineral slurry placing desired metal compounds in solution, the process may include the step of chemically treating the leach solution with oxidizing agents to produce manganese oxide and/or other metal products. Alternatively or in addition, the process may include the step of chemically treating the leach solution with reducing agents producing metallic manganese.

After the step of leaching the extracted mineral slurry, the process may include the step of treating the leach solution with one or more treatments to remove selected metals or other metal compounds. Additionally, the step of removing metals and/or metal compounds of manganese may comprise electrochemically plating the manganese metal product out of solution or treating the leach solution to precipitate the manganese metal product from solution.

Alternatively, the extracted mineral slurry may be processed by pyrometallurgical processes to remove the metal compounds from the mineral slurry. In this alternative, the process for producing metal compounds directly from underground mineral deposits in an environmentally sensitive location may include the steps of:

(a) forming a borehole from an accessible site into a mineral deposit containing metal compounds;

(b) inserting a slurry-forming device having a nozzle into the borehole adapted to direct pressurized water through the nozzle into the mineral deposit;

(c) supplying pressured water through the nozzle of the slurry-forming device into the mineral deposit forming a mineral slurry containing the metal compounds from the mineral deposit;

(d) extracting the mineral slurry containing the metal compounds through the borehole;

(e) transporting the mineral slurry away from the borehole to a location remote from the site;

(f) physically separating the extracted mineral slurry at the remote location; and

(g) removing metal compounds by treating the mineral slurry by a pyrometallurgical extraction treatment adapted to remove the metal compounds.

Prior to the step of physically separating the mineral slurry, the process may include grinding particulate in the mineral slurry to a particle size of about 80% smaller than 100 mesh, and may include grinding to a particle size of about 80% smaller than 200 mesh. After the step of physically separating the mineral slurry, water may be removed from the mineral slurry and the resulting ore material then mixed with at least one reducing agent selected from a group consisting of coal, coke, coke-breeze, char, reducing sugar, molasses, and a combination of two or more thereof. Alternatively or in addition, water may be removed from the mineral slurry and the ore material may be mixed with at least one additive selected from a group consisting of calcium oxide, limestone, soda ash, Na₂CO₃, NaHCO₃, NaOH, borax, NaF, fluorspar, CaF₂, aluminum smelting industry slag and a combination of two or more thereof.

The step of removing metal compounds may be performed in a rotary hearth furnace. Alternatively, the step of removing metal compounds may be performed in an electric arc furnace, a blast furnace, or an induction furnace.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart showing steps of a method for producing metal from a mineral deposit; and

FIG. 2 is a diagrammatical partial section view of a borehole mining operation.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring now to FIG. 1, a method is disclosed for producing metals and metal compounds that may be used to extract metal products from environmentally sensitive areas. As shown in FIG. 1, the method may include steps of:

• • (a) forming a borehole at an accessible site into a mineral deposit, the mineral deposit containing metal oxides such as metal oxides of manganese;
  • (b) inserting a slurry-forming device having a nozzle into the borehole, the device adapted to directing pressurized water through the nozzle into the mineral deposit;
  • (c) supplying pressured water through the nozzle into the mineral deposit;
  • (d) forming a mineral slurry containing metal oxides, such as metal oxides of manganese;
  • (e) extracting the mineral slurry through the borehole to the surface;
  • (f) optionally, separating water from the extracted mineral slurry, which may be recycled to a water storage tank;
  • (g) optionally, forming a filter-cake of the mineral slurry having a water content of between about 8% and 10%;
  • (h) transporting or conveying the mineral slurry to a processing location;
  • (i) leaching the mineral slurry to convert the metal oxides to a soluble form in a leach solution; and
  • (j) removing metal compounds of manganese by treating the leach solution with an extraction treatment adapted to remove metal products, or other hydrometallurgical leaching techniques to extract metal products.

Alternatively, instead of removing metal compounds from a leach solution, desired metal compound may be removed from the mineral slurry using pyrometallurgical processes. After transporting, as shown in the alternative process in FIG. 1, the process may include steps of upgrading the mineral slurry by physical separation. After de-watering the mineral slurry, the resultant ore material may be processed using pyrometallurgical extraction as discussed below.

The present method involves first forming a bore hole into a mineral deposit with suitable drilling equipment at a select borehole site that is environmentally permitted, and lowering into the mineral deposit through the borehole a slurry-forming device having a nozzle through which pressurized water can be injected into the mineral deposit. For removal of manganese-bearing ore from such a mineral deposit, the water pressure may be between 1000 and 2500 psi. In any event the pressurized water should be sufficient to break up the ore in the mineral deposit and form a mineral slurry that can be pumped through the borehole to the surface at the borehole site. The range of extraction of ore from the mineral deposit will depend on the softness of the mineral deposit and the extent and direction of the water pressure. The slurry-forming device may permit the nozzle to be controlled and directed in any desired direction, and the nozzle may be rotated about the axis of the borehole to carve out an approximately circular work area in the ore vein around the borehole, and may be moved along the borehole to extend the work area and volume of ore removed from the borehole site.

The present method is effective where the mineral deposit is in friable form, granular form, or other form capable of being broken up by the pressurized water from the slurry-forming device to create the mineral slurry. Higher pressure water may be used for harder or denser mineral deposits, or where a larger work area of extraction may be desired from a borehole. In some cases, explosives or other supplemental means may be used where desired and permissible to assist the water pressure in forming the mineral slurry in the mineral deposit.

In one embodiment, the method could be performed with the mineral deposit of metal compounds of manganese formed in an mineral deposit about 200 feet to 400 feet beneath the surface of an overburden in the Emily District of Minnesota, where the mineral deposit contains manganese ore including pyrolusite (MnO₂) and magnanite (MnO(OH)). Such manganese deposits may contain “sand-like” particles in a granular form capable of being broken up by water at a pressure between about 1000 and 2500 psi. In alternative locations, the mineral deposit may contain oxides of manganese, cobalt, copper, iron, chromium, lead, nickel, magnesium, platinum, palladium, gold, silver, aluminum, lithium, molybdenum, tungsten, uranium, vanadium, zinc, and zirconium.

As shown in FIG. 2, a borehole drilling device 10 may include a hydraulic slurry-forming device 20 having a nozzle 22 inserted into a desired work area 24 in a mineral deposit through casing pipe 30. The borehole drilling device 10 may have a drill bit 40 at its lower end adapted to bore a borehole cavity 42 that is somewhat larger in diameter than the hydraulic slurry-forming device 20 and the casing pipe 30. As shown in FIG. 2, the drilling device 10 may drill through the cap rock 44, through the desired work area 24 in the mineral deposit, and into the bedrock 46 forming a sump 48. An eductor section 50 is positioned in the casing pipe 30 below the hydraulic slurry-forming device 20. An inner pipe 60 extends through the casing pipe 30 in connection with the eductor section 50 and forming annular conduit 70 between the inner pipe 60 and the casing 30, which is in connection with the nozzle 22 of the slurry-forming device. The casing pipe 30 and inner pipe 60 extend from an work area in a mineral deposit, to the surface, and may be formed by connecting a plurality of pipe sections end to end. The inner pipe 60 forms an outlet slurry passage for removing the mineral slurry from the mineral deposit, and the conduit 70 forms an inlet water passage for delivering water 72 to the nozzle 22 of the slurry-forming device 20 in the mineral deposit.

A pump 80 is provided in connection with the annular conduit 70 for delivering pressurized water into the conduit 70 to the hydraulic slurry-forming device 20. In operation, the pump may provide between about 400 and 1000 gallons per minute (gpm) water flow. In one alternative, the pump provides 750 gpm of water at 2500 psi to the nozzle 22 of the slurry-forming device. The pressurized water flow, which may be fitted with a suitable regulator, is directed through the nozzle 22 into the work area in the mineral deposit transverse to the borehole. As the water passes through the nozzle 22, the flow accelerates to a flow sufficiently powerful to break and scale away the ore from the mineral deposit in the work area 24 to form a mineral slurry 82. The water pressure through the nozzle 22 may be regulated between about 1500 and 2500 psi. Alternatively, the water pressure through the nozzle 22 may be regulated between about 800 and 1500 psi. The loosened material from the mineral deposit is fluidized through mixing with the injected water to form the mineral slurry 82 in the work area.

The upper end of the drilling device 10 may include a swivel joint 100 and turntable 102 capable of rotating at least a portion of the drilling device. The drilling device may be supported by a suspension 104 such as a crane, derrick, or other suspension. In operation, the drilling device may be rotated to turn the drill bit 40 for extending the borehole into the mineral deposit. Alternatively or in addition, the hydraulic slurry-forming device 20 may be rotated for rotating the nozzle 22 in an approximately circular cutting path around the borehole. By rotating the nozzle around the axis of the borehole, and by raising and lowering the nozzle in the borehole, an approximately cylindrical shaped work area cavity 110 may be formed around the borehole in the mineral deposit 24 by the pressurized water flow 72 fluidizing material from the deposit and forming the mineral slurry 82 for extraction.

Water pumped through the inlet water conduit 70 toward the work area that does not exit the nozzle is directed to the eductor 50 having a discharge into the inner pipe 60. The flow of water through the eductor 50 provides suction to draw mineral slurry from the work area into the inner pipe 60. The mineral slurry and water are sucked through an inlet into the inner pipe 60 and transported up to the surface at the borehole site through the inner pipe 60. The mineral slurry may be directed to a clarifier tank 90 or other suitable container at the borehole site where water may be removed and the slurry concentrated. As the mineral particulate settles to the bottom of the tank 90, water may be filtered from the tank and pumped back to the work area in the mineral deposit through the conduit 70. By re-using the water, make-up water may be reduced to a minimum and the method becomes even more environmental capable as essentially a closed loop system for removing the mineral slurry from the mineral deposit. In one example, additional water use in operation of the formation and removal of the mineral slurry was limited to 1000 gallons per day. Water may be supplied in a water storage tank, not shown, such as a 20,000 or 40,000 gallon storage tank.

In one embodiment, the flow rate of mineral slurry through the inner pipe 60 may be between about 400 and 800 gpm, which may be directed to the clarifier tank 90. The extracted mineral slurry may be between about 10% and 20% solids, and may be greater than 20%. For certain mineral deposits, the extracted mineral slurry may be less than 10% solids.

For larger mineral deposits or directional ore veins, a directional borehole may be formed slanted and/or extended generally horizontally through the ore vein. In certain directional boreholes, the slurry-forming device may be moved along the borehole without being rotated. Also, a plurality of deviated boreholes may be drilled from one “mother” bore, each deviated borehole extending the inclination and/or horizontal reach into the mineral deposit as desired to increase the volume of removed mineral ore.

The overall structure and operation of a borehole drilling apparatus and slurry-forming device may be as described in U.S. Pat. Nos. 4,059,166, 6,460,936, and 6,688,702, the disclosures of which are incorporated herein by reference for appropriate constructional and operational details for purpose of best mode of carrying out the method of the present disclosure.

The method may be used also by forming a first borehole substantially vertically from the surface into the mineral deposit and a second borehole slanted so as to intersect the first bore in the mineral deposit, not shown. The slurry-forming device may be inserted through the second slant borehole to increase the range to which water can be injected under pressure into the mineral deposit, and the formed mineral slurry can be removed from the mineral deposit through the first bore hole. For certain mineral deposits, this embodiment may increase the range of the removal of metal compounds from the ore deposit.

In another alternative, a plurality of boreholes may be provided for water injection and at least one borehole provided for mineral slurry extraction. In one embodiment, not shown, four boreholes are provided for water injection, arranged approximately in quadrants of a work area. An extraction borehole is provided in approximately centrally located in the work area, as desired, for extraction of slurry. The extraction borehole may not be as deep as, or may be deeper than the boreholes through which water is injected into the mineral deposit.

In any case, after the mineral slurry is extracted from the mineral deposit through one of the boreholes or the inner pipe 60 of a given borehole, the mineral slurry is processed to remove the desired metal products. In clarifier tank 90, for example, water from the mineral slurry may be filtered, removed and recycled. The mineral slurry may pass through a screen such as a screen having 1/16 inch openings to screen out larger ore pieces. Then additional water may be removed using a cyclone, settling tank, and/or a thickener tank which increases the solids in the slurry from about 10% solids to between about 45% and 75% solids. The mineral slurry may be further dewatered in a filter press to form a filter cake of mineral slurry having a moisture content between about 8% and 10%. Alternatively, the moisture content of the filtered mineral slurry may be less than 8% or more than 10% as desired in the particular embodiment. The water removed from the mineral slurry may be pumped into the water storage tank, or may be pumped back to the work area of the mineral deposit through annular conduit 70.

During the mining process, slightly more water may be extracted with the mineral slurry from the mineral deposit than is injected through the nozzle. A net withdrawal of water from the work area produces a “cone of depression” in the work area. The depression may enable an inflow or migration of pre-existing underground water towards the borehole area that enables mineral slurry to flow toward the work area. The cone of depression may slow the outflow of mineral slurry away from the work area.

For extracting minerals from environmentally sensitive and other areas, the extracted mineral slurry is transported away from the mine site to be processed at a remote location as discussed below. The mineral slurry, either as extracted from the mineral deposit or after concentration, may be transported by truck, rail, pipeline, or a combination thereof to the remote location to remove the desired compounds.

To remove the desired compounds, the mineral slurry may be processed to form a leaching solution from which the desired metal compounds and other metal products may be removed. Alternatively, the desired compounds may be removed from the mineral slurry by a pyrometallurgical process. The process of removing desired compounds from the mineral slurry may be performed at the borehole site as desired and permitted, or may be performed at the remote location.

Optionally, prior to leaching, or pyrometallurgical processing discussed below, the process may include grinding or otherwise reducing the particle size of the ore in the mineral slurry to a particle size of about 80% less than 100 Tyler mesh, or a particle size of 80% less than 200 Tyler mesh.

In one embodiment, the manganese mineral forms include pyrolusite (MnO₂) and magnanite (MnO(OH)) having the consistency of “sand-like” particles having a particle size in the range of about 10 mesh to about 500 mesh. In this deposit, the particles are porous, fine particles that may not require further grinding, and may need little preparation before the step of leaching of the ore to form a leaching solution from which manganese metal may be extracted.

The mineral slurry may be leached to convert the metal oxides to a soluble form in a leach solution. The leach solution may be formed in a suitable leaching tank such as a tank having stifling blades, or other stirred tank. The stirred tank may be adapted to a continuous leaching process, or may be adapted to a batch process.

The leach solution may be formed with approximately 10% manganese in an acidic solution. For leaching some mineral ores, the leach solution may include between about 10% and 80% manganese. Alternatively, the leach solution may include between about 5% and 10% manganese.

Leaching may be conducted using SO₂ gas, which acts with water to form sulfurous acid (H₂SO₃) to render the metal compounds in the minerals soluble in solution. SO₂ gas may be introduced into the stirred mineral slurry through diffusers or spargers placed below the tank stirring blades. The SO₂ gas is passed through the manganese leach solution to a pH of about 1. The leach solution may have between about 5% and 8% SO₂ at a pH of about 1. The SO₂ addition is controlled to maintain the pH of about 1 for a processing period of about 10 minutes, after which time about 95% or more of the manganese is in solution. Alternatively, sulfuric acid (H₂SO₄) may be used to form the acidic leach solution with similar pH and percent manganese in solution. In any case, the manganese leaching process is conducted at ambient temperature and atmospheric pressure in the leaching tank.

A reducing agent may be provided in the leach solution. The reducing agent may be SO₂, carbon, reducing sugar, molasses, or other reducing agents. The reducing agents reduce the oxidation state of the metal oxides in solution, such as from Mn(4+) to Mn(2+).

The manganese (Mn(2+)) in the acidic leach solution may be MnSO₄. The leach solution may be chemically treated with oxidizing agents to produce metal compounds, such as metal oxides. The manganese leach solution may be treated with an oxidizing agent, such as H₂O₂, NaOCl, KMnO₄, or Na₂S₂O₈ or other oxidizing agent to form chemical manganese dioxide (MnO₂), or CMD in solution. Alternatively, the MnSO₄ may be electrochemically oxidized to form electrolytic manganese dioxide, or EMD in solution. In yet another alternative, the MnSO₄, may be dried and crystallized to form chemical grade MnSO₄ or fertilizer grade MnSO₄.

In yet another alternative, the process may include the step of chemically treating the leach solution with reducing agents producing metallic manganese. Then, electrochemically treating the leach solution to plate out metallic manganese. The extraction treatment may be an electrochemical treatment, such as electroplating the desired metal onto a cathode.

After the desired metal compounds or other metal products are extracted from the leach solution, the leach solution may be reconditioned to the desired pH and reused to process subsequent batches of mineral slurry. Mineral solids and solutions left over from the leaching process may be neutralized, if necessary with lime or limestone, for use or disposition. Alternatively, the leach solution may be further used for secondary processes. For example, the use of SO₂ gas dissolved in water produces a sulfate, which can be used to make ammonium sulfate fertilizer. After the desired metal products are removed from the leach solution, ammonia may be added to form the ammonium sulfate.

As discussed above, the present methods may be used to make metal products directly from underground mineral deposits other than manganese where the ore vein can be broken up to form a mineral slurry. This method may be suitable for use in making oxides of cobalt, copper, iron, chromium, lead, nickel, magnesium, platinum, palladium, gold, silver, aluminum, lithium, molybdenum, tungsten, uranium, vanadium, zinc, and zirconium directly from underground mineral deposits.

For ore from some mineral deposits, the leach solution may have a pH of about 3 or lower, and in certain alternatives may have a pH of about 5 or lower. Additionally, certain ores from mineral deposits may be in the leach solution at temperatures and pressures higher than ambient to render the minerals soluble.

Some ores form mineral deposits containing a plurality of metals, each having certain extraction techniques the present method may be used to make two or more metal products of different metals from the mineral slurry. The mineral slurry may require multiple treatments each adapted to removing specific metal products from the mineral slurry depending upon the composition of the extracted ore. In some cases, certain leach solution treatments may be used to remove undesired or other metals and metal compounds that would contaminate the desired metal compound or other desired metal products. In other cases certain leach solution treatments may recover metal products for sale or use depending in part on market prices. For example, certain manganese ore deposits contain various amounts of other metals and compounds such as iron, silica, and alumina which may be recovered if present in sufficient quantities to make recovery commercially viable.

For example, iron may be removed from the leach solution by raising the pH of the solution to about 5 or greater by the addition of lime or other base, then adding an oxidizing agent, such as manganese oxide or other oxidizer to form an iron precipitate. The iron precipitate may then be filtered from the solution as a metal product.

In another example, where a leach solution is formed containing nickel and manganese, it may be desired that nickel remain in solution and manganese be removed. The manganese may be precipitated from the leach solution by an addition such as ammonia and carbon dioxide, which forms MnCO₂. The manganese precipitate may be filtered from the solution to form the metal product.

Amounts of heavy metals such as nickel, arsenic, lead, cobalt, and other heavy metals found in the ores may be removed from a leaching solution form from the mineral slurry by adding sulfide to the leach solution to form precipitates that may be filtered from the solution to form the metal product.

Other impurities and undesired metals and compounds may be found in the mineral ore which may be from a leaching solution form from the mineral slurry. Various chemical treatments may be applied as desired to remove the metal products from the leach solution. It is contemplated that the leach solution may be heated to a desired temperature and pressure according to the chemical treatment applied to form the desired metal products.

In some embodiments, after impurities and undesired compounds and metals are precipitated from the solution, the leach solution may be treated with chemical or electrochemical techniques to plate out the desired metal compounds or other metal products from solution. Also, to produce a metallic state, reducing agents may be provided in the leach solution. The reducing agents may be SO₂, carbon, reducing sugar, molasses, or other reducing agents. Alternatively, the leach solution may be chemically treated with oxidizing agents to produce metal products, such as metal oxides.

In an alternative process, the mineral slurry may be processed using pyrometallurgical extraction methods to remove the certain metal compounds from the mineral slurry. The process may include grinding or otherwise reducing the particle size of the ore in the mineral slurry to a particle size of about 80% less than 100 Tyler mesh, or to a particle size of 80% less than 200 Tyler mesh. To increase the concentration of desired metal compounds in the mineral slurry, the mineral slurry may be upgraded using physical separation processes to separate tailings such as rock and other separable products from the slurry. The mineral slurry may be upgraded using physical separation such as high intensity magnetic separation, gravity separation, floatation, or other separators as desired. In some applications for processing at a location remote from the borehole site, the mineral slurry may be de-watered for transportation. For grinding and physical separation processes the mineral slurry may be reslurrified as desired.

After the step of physically separating the mineral slurry, the upgraded mineral slurry is de-watered, and the resulting ore material may be mixed with one or more reductants. The reducing agents may be selected from a group consisting of coal, coke, coke-breeze, char, reducing sugar, molasses, and a combination of two or more thereof. Alternatively or in addition, the mineral slurry is de-watered, and the resulting ore material mixed with at least one additive selected from a group consisting of calcium oxide, limestone, soda ash, Na₂CO₃, NaHCO₃, NaOH, borax, NaF, fluorspar, CaF₂, aluminum smelting industry slag and a combination of two or more thereof. The ore material mixture may then be fed into a furnace for extracting the desired metal compound. The furnace may be an electric arc furnace, blast furnace, induction furnace, or rotary hearth furnace at a temperature selected for the desired metal compound.

In one application, a mineral slurry containing manganese ore may be processed in a rotary hearth furnace between approximately 1100 and 1300° C. The de-watered manganese ore material may be mixed with a reductant such as coal and a fluxing agent such as limestone. Optionally, the manganese ore material may be formed into briquettes. The manganese slurry may be processed in the furnace to produce ferromanganese and/or silicomanganese, with other compounds and tailings separating as slag.

As discussed above, the mineral slurry may be processed at the borehole site or transported away from the borehole site to be processed at a remote location. The mineral slurry may be transported by truck, rail, pipeline, or a combination thereof as extracted from the mineral deposit or after removing part of the water from the slurry. By transporting the mineral slurry to a location remote from the borehole site, the use chemicals, such as sulfurous acid and sulfuric acid in the leaching step may be managed in a location more environmentally suited to chemical processing. Further, by including the transportation step in the method, one leaching and metal product recovery facility can service multiple borehole sites and a large volume of mineral slurry, vastly increasing the productivity of the method in making metal products directly from underground mineral deposits.

In one embodiment, the mineral slurry is transported to the processing location in water tight dump trucks such as a 20 ton covered side dump trucks. Prior to transporting, the concentrated mineral slurry may be formed into filter cakes, the filter cakes being loaded directly into trucks or onto railcars. Alternately, the filter cakes may be loaded into ore bags such as 2000 lb water tight sacks, which may be transported by truck or rail. In one alternative, the mineral slurry is not formed into a filter cake and is transported by pipeline, the mineral slurry having a solids content about 50% or greater.

The presently disclosed process may be used to recover metal products directly from mineral deposits under environmentally sensitive geographic areas. The process may include the steps of forming a borehole into a mineral deposit of ore containing metal compounds, inserting a slurry-forming device having a nozzle into the borehole adapted to direct pressurized water through the nozzle into the mineral deposit, supplying pressured water through the nozzle into the mineral deposit forming a mineral slurry from an ore vein, and extracting the mineral slurry through the borehole. Then, transporting the mineral ore containing metal oxides away from the borehole to a location remote from the borehole site, leaching the metal oxides at the remote location to convert the metal oxides to a water soluble form in a leach solution, and removing metal compounds and other metal products by treating the leach solution with an extraction treatment adapted to remove the metals and/or metal compounds.

By transporting the mineral ore away from the mine site, chemicals used at the borehole site and needed facilities may be substantially reduced. The slurry formation step may use water without chemical or other additions. The water may be taken from groundwater or surface sources. Additionally, it is contemplated that the water may be returned to the environment with little cleaning or water treatment required. By using the disclosed process and transporting the mineral slurry away from the mine site, valuable mineral deposits may be extracted in environmentally sensitive areas with insignificant impact on the overlying surface area.

While the invention has been illustrated and described in detail with reference to the figures and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that one skilled in the art will recognize, and that it is the applicants' desire to protect, all aspects, changes and modifications that come within the spirit of the invention.

Claims

1. A process for producing metal compounds directly from underground mineral deposits in an environmentally sensitive area comprising the steps of:

(a) forming a borehole from an accessible site into an underground mineral deposit containing metal compounds including oxides of manganese beneath the environmentally sensitive area;

(b) inserting a slurry-forming device having a nozzle into the borehole adapted to direct pressurized water through the nozzle into the mineral deposit under the environmentally sensitive area;

(c) supplying pressured water through the nozzle of the slurry-forming device into the mineral deposit forming a mineral slurry containing the metal compounds from the mineral deposit under the environmentally sensitive area;

(d) extracting and dewatering the mineral slurry containing the metal compounds through the borehole in the environmentally sensitive area;

(e) transporting the dewatered mineral slurry as extracted from the mineral deposit away from the borehole to a location remote from the environmentally sensitive area;

(f) leaching the extracted mineral slurry at the remote location to convert the metal compound to a soluble form in a leach solution; and

(g) removing metal compounds by treating the leach solution with an extraction treatment adapted to remove the metal compounds.

2. The process for producing metal compounds directly from underground mineral deposits according to claim 1, where the mineral slurry is transported by a device selected from a group consisting of truck, rail, pipeline, and a combination of two or more thereof.

3. The process for producing metal compounds directly from underground mineral deposits according to claim 1 further comprising the step of:

prior to the step of leaching the mineral slurry, grinding particulate in the mineral slurry to a particle size of about 80% smaller than 100 mesh.

4. The process for producing metal compounds directly from underground mineral deposits according to claim 1 further comprising the step of:

prior to the step of leaching the mineral slurry, grinding particulate in the mineral slurry to a particle size of about 80% smaller than 200 mesh.

5. The process for producing metal compounds directly from underground mineral deposits according to claim 1, further comprising the step of:

after the step of leaching the mineral slurry, treating the leach solution with one or more treatments to remove selected metals and metal compounds.

6. The process for producing metal compounds directly from underground mineral deposits according to claim 1 where the step of leaching the mineral slurry comprises leaching the mineral slurry to put desired metal compounds into solution.

7. The process for producing metal compounds directly from underground mineral deposits according to claim 1 where the step of leaching the mineral slurry comprises leaching the mineral slurry with sulfurous acid.

8. The process for producing metal compounds directly from underground mineral deposits according to claim 1 where the leach solution comprises at least one reducing agent selected from a group consisting of SO2, carbon, reducing sugar, molasses, and a combination of two or more thereof.

9. The process for producing metal compounds directly from underground mineral deposits according to claim 1 where the leach solution has a pH of 3 or lower.

10. The process for producing metal compounds directly from underground mineral deposits according to claim 1 further comprising the step of:

prior to the step of removing metal compounds, chemically treating the leach solution with oxidizing agents producing metal compounds.

11. The process for producing metal compounds directly from underground mineral deposits according to claim 1 further comprising the step of:

prior to the step of removing metal compounds, chemically treating the leach solution with reducing agents producing selected metal products.

12. The process for producing metal compounds directly from underground mineral deposits according to claim 1 where the step of removing metal compounds comprises electrochemically treating the leach solution removing selected metals or metal compounds.

13. The process for producing metal compounds directly from underground mineral deposits according to claim 1 further comprising

forming a second slanted borehole in the environmentally sensitive area intersecting the first borehole in the mineral deposit containing metal compounds including oxides of manganese;

where the step of inserting a slurry-forming device is into the second borehole, and where the step of extracting is through the first borehole.

14. A process for producing metal compounds directly from underground mineral deposits in an environmentally sensitive area comprising the steps of:

(a) forming a borehole from an accessible site into an underground mineral deposit containing metal compounds including oxides of manganese beneath the environmentally sensitive area;

(b) inserting a slurry-forming device having a nozzle into the borehole adapted to direct pressurized water through the nozzle into the mineral deposit under the environmentally sensitive area;

(c) supplying pressured water through the nozzle of the slurry-forming device into the mineral deposit forming a mineral slurry containing the metal compounds from the mineral deposit under the environmentally sensitive area;

(d) extracting and dewatering the mineral slurry containing the metal compounds through the borehole in the environmentally sensitive area;

(e) transporting the dewatered mineral slurry as extracted from the mineral deposit away from the borehole to a location remote from the environmentally sensitive area;

(f) physically separating the extracted mineral slurry at the remote location; and

(g) removing metal compounds by treating the mineral slurry by a pyrometallurgical extraction treatment adapted to remove the metal compounds.

15. The process for producing metal compounds directly from underground mineral deposits according to claim 14, where the mineral slurry is transported by a device selected from a group consisting of truck, rail, pipeline, and a combination of two or more thereof.

16. The process for producing metal compounds directly from underground mineral deposits according to claim 14 further comprising the step of:

prior to the step of physically separating the mineral slurry, grinding particulate in the mineral slurry to a particle size of about 80% smaller than 100 mesh.

17. The process for producing metal compounds directly from underground mineral deposits according to claim 14, further comprising the step of:

after the step of physically separating the mineral slurry, mixing the mineral slurry with at least one reducing agent selected from a group consisting of coal, coke, coke-breeze, char, reducing sugar, molasses, and a combination of two or more thereof.

18. The process for producing metal compounds directly from underground mineral deposits according to claim 14, further comprising the step of:

after the step of physically separating the mineral slurry, mixing the mineral slurry with at least one additive selected from a group consisting of calcium oxide, limestone, soda ash, Na2CO3, NaHCO3, NaOH, borax, NaF, fluorspar, CaF2, aluminum smelting industry slag and a combination of two or more thereof.

19. The process for producing metal compounds directly from underground mineral deposits according to claim 14, where the step of removing metal compounds is performed in a rotary hearth furnace in a reducing atmosphere.