WILMOT, John, C. (42817 North Ericson Lane, Anthem, AZ, 85086, US)
HAZEN, Wayne, W. (2655 Van Gordon Drive, Lakewood, CO, 80215, US)
AMELUNXEN, Peter (Av. Bolognesi 902A, Cayma, Arequipa, PE)
WILMOT, John, C. (42817 North Ericson Lane, Anthem, AZ, 85086, US)
HAZEN, Wayne, W. (2655 Van Gordon Drive, Lakewood, CO, 80215, US)
1 . A method of forming molybdenum oxide from material including molybdenum sulfide, the method comprising the steps of: providing material including molybdenum sulfide, pressure leaching the material including molybdenum sulfide to form a pressure leach discharge comprising pressure leach discharge solids and pressure leach discharge liquid; separating the pressure leach discharge solids and pressure leach discharge liquid to form a separated liquid and separated solids; extracting soluble metal from the sepaiated liquid to form a loaded stream, and stripping the loaded stieam using a basic solution to form a stripped solution
2. The method of forming molybdenum oxide from material including molybdenum sulfide of claim 1 , further comprising the step of deoiling the material including molybdenum sulfide.
3 The method of forming molybdenum oxide from material including molybdenum sulfide of claim 1 , further comprising the step of upgrading the material including molybdenum sulfide.
4 The method of forming molybdenum oxide from material including molybdenum sulfide of claim 1 , further comprising the step of recycling a stream of strip solution to a pressure leach vessel.
5. The method of forming molybdenum oxide from material including molybdenum sulfide of claim 1 , wherein the step of extracting soluble metal comprises extracting metal values using an organic stage.
6. The method of forming molybdenum oxide from material including molybdenum sulfide of claim 1 , wherein the step of extracting soluble metal, further comprises a sub-step of extracting additional materials.
7 The method of forming molybdenum oxide from material including molybdenum sulfide of claim 6, wherein the sub-step of extracting additional materials comprises extracting one or more of molybdenum, rhenium, and rare earth metals
8 The method of forming molybdenum oxide from material including molybdenum sulfide of claim 1 , wherein the step of extracting soluble metal comprises using a technique selected from the group consisting of solution extraction and ion exchange
9 The method of forming molybdenum oxide from material including molybdenum sulfide of claim 1 , wherein the step of extracting soluble metal comprises using solution extraction
10 The method of forming molybdenum oxide from material including molybdenum sulfide of claim 1 , further comprising the step of recycling at least a portion of the sepaiated liquid to a pressure leach vessel
1 1 The method of forming molybdenum oxide from material including molybdenum sulfide of claim 1 , further comprising the step of processing the separated solids to form additional pioducts
12 The method of forming molybdenum oxide from material including molybdenum sulfide of claim 1 1 , wherein the step of processing the separated solids to form additional products comprises forming ammonium dimolybdate
13 The method of foiming molybdenum oxide fiom material including molybdenum sulfide of claim 1 , further compiising the step of removing alkali metal ions from the stripped solution
14 The method of forming molybdenum oxide from material including molybdenum sulfide of claim 1 , fuithei compiising the step of lemoving additional matenals fiom a dischaige stieam of a solvent extiaction piocess
15 A system foi converting molybdenum sulfide to molybdenum oxide, the system compiising
a pressure leach vessel, a solid-liquid separation stage fluidly coupled to the pressure leach vessel, a solution-extraction stage fluidly coupled to the solid-liquid separation stage, and a basic solution stripping stage fluidly coupled to the solution-extraction stage
16 The system for converting molybdenum sulfide to molybdenum oxide of claim 15, further comprising an ion exchange stage opeiatively coupled to the solid-liquid separation stage
1 7 The system for converting molybdenum sulfide to molybdenum oxide of claim 15, further comprising a strip recycle stream that provides recycled solution from the basic solution stripping stage to the solution-extraction stage
1 8 The system tor converting molybdenum sulfide to molybdenum oxide of claim 15, further comprising a iecycle stream to recycle a portion of a liquid effluent from the sohd- hquid separation stage to the piessure leach vessel
19 The system for converting molybdenum sulfide to molybdenum oxide of claim 15, further comprising a filter interposed between the solid-liquid separation stage and the solvent-extiaction stage
20 A system for converting molybdenum sulfide to molybdenum oxide, the system comprising a pressure leach vessel, a solid-liquid separation stage fluidly coupled to the pressure leach vessel, wherein the solid-liquid separation stage produces a liquid stream and a solids stieam, d solution-extraction stage fluidly coupled to the solid-liquid sepaidtion stage, a basic solution shipping stage fluidly coupled to the solution-extiaction stage, a piessure leach iecycle stieam, which recycles a portion of the liquid stieam to the piessuie leach vessel, and a strip iecycle stream that provides recycled solution from the stiippmg stage to the solution-extiaction stage
SYSTEM AND METHOD FOR CONVERSION OF MOLYBDENITE TO ONE OR
MORE MOLYBDENUM OXIDES
Field of Invention
The present invention generally relates to the processing of molybdenum and more paiticLilaily to the production of molybdenum oxide materials (e g , molybdenum tπoxide, MoOi) from molybdenum sulfide (e g , M0S 2 )
Background of the Invention
Molybdenum is an increasingly important material and is used for various industrial and scientific purposes These purposes range from imparting strength in metal alloys to use as a chemical catalyst Likewise, molybdenum compositions are highly suitable for the production of a wide variety of products, including electrical contacts, electrical filaments, colloidal lubricant additives, and other diverse products
Molybdenum does not occur as a free element in nature In nature it can be found in various common forms, such as in ore in the form of molybdenite (MoSi) Molybdenite geneially forms a relatively small percentage of the ore in which it is found Typically, molybdenite ore consists of silicified granite compositions having deposits of soft, black, and hexagonal MoS? crystalline structuies widely dispeised therein These mateuals are found in an average concentiation of only about less than 1 % by weight of the entire oie body Accordingly, significant process steps are typically lequired in order to lecovei molybdenum from oie
In view of its incieasing industrial and scientific importance, substantial iesearch activity has been devoted to the development of improved methods for the beneficiation of MoS 2 -containing oie products Normally, MoS? derived from molybdenite ore is converted by oxidization to various oxides of molybdenum, followed by further processing in oider to obtain a purified molybdenum oxide pioduct consisting pπmaiily of molybdenum tπoxide (MoO 3 ) The molybdenite ore may be initially subjected to a physical grinding process in which the ore is reduced in size to a plurality of small particles The ore particles are then fuithei tieated to remove the desued M0S 2 This step may be accomplished using a variety of techniques, including oiganic flotation extiaction procedures As a result, the desired M0S 2 may be effectively separated fiom ore-based waste materials (conventionally known as "gangue") which consist primarily of silica-containing by-products Specifically, the
desired M0S 2 compositions will, by control of the surface chemistry within the flotation unit, be readily isolated in the flotation froth Many variations and alternatives exist in connection with the isolation of M0S 2 from the ore, with the selected procedure depending on the type and grade of ore to be processed Once isolated, M0S 2 may converted (oxidized) to form MOO 3 by forming a slurry or suspension of M0S 2 in water and thereafter heating the slurry in a pressure leach vessel During the heating process, an oxygen atmosphere is maintained within the vessel As a result, MoOi is generated in accordance with one or more variations of the following exothermic ieaction MoS 2 + 4 5 0 2 (g) + 2H 2 O → MoO 3 + 2H 2 SO 4
Several patents and other literature have taught numerous processes and systems for carrying out one or more variations on the above reaction to greater or lesser degrees of completion Some of the patents which discuss this type of process include U S Patent No 4,046,852 to Vertes, et al , entitled "Purification Process for Technical Grade Molybdenum Oxide", U S Patent No 4,165,362 to Reynolds, entitled "Hydrometallurgical Piocessing of Molybdenite Ore Concentrates", U S Patent No 4,379,127 to Bauer, et al , entitled "Method of Recovering Molybdenum Oxide", U S Patent No 4,444,733 to Laferty, et al , entitled "Process for Recovering Molybdenum and Copper From Sulfide Concentrates", U S Patent No 4,478,698 to Wilkomnsky, et al , entitled "Process For Recovering Copper and Molybdenum From Low Grade Coppei Concentrates", U S Patent No 4,512,958 to Bauei, et al , entitled "Method of Recoveiing Molybdenum Oxide", U S Patent No 5,804, 151 to Sweetsei, et al , entitled "Process For Autoclaving Molybdenum Disulfide", and U S Patent No 5,820,844 to Khan, et al , entitled "Method for the Production of A Purified MoO 3 Composition " Many of these patents and othei publications focus on the oxidation ieaction that converts some 01 all of the MoS 2 to MoO 3 or othei molybdenum oxides, which other oxides may be ieferred to as lessei molybdenum oxides While the oxidation reaction is an important step in the pieparation of molybdenum oxide fiom molybdenum-containing ore, the piocess foi obtaining usable molybdenum typically includes numeious post-oxidation reaction steps that are important to the overall efficiency of the process
U S Patent No 6,730,279, to Balliett et al , entitled "Pioduction of Pure Molybdenum Oxide horn Low Giade Molybdenite Concentrates," which issued on May 4, 2004, illustiates possible post-oxidation steps Foi example, a piocess illustrated in Balliett et al includes an oxidation step, followed by a sepaiation step to separate the molybdenum
oxide material from a centrate The centrate is sent to an optional amine solvent-extraction process operated to produce a two-phase mixture having a molybdenum-loaded organic phase and an aqueous phase The organic phase is stripped with concentrated sulfuric acid, at a pH less than about 3 and the recovered molybdenum values are recycled back to the oxidation step Although the inventors purport that this process works, some results indicate otherwise Furthermore, use of concentrated sulfuric acid to strip the organic material is detrimental to most piocessing equipment and thus increases operating costs of molybdenum recovery systems and processes Accordingly, improved methods and systems for efficiently obtaining molybdenum oxide from molybdenite concentrates that do not employ sulfuric acid stripping are desired
Summary of the Invention
The present invention provides a method and a system for converting molybdenite (M0S 2 ) to one or moie molybdenum oxides While the ways in which the present invention addresses the vanous drawbacks of the pπoi art will be discussed in gieater detail below, in general, the invention provides a system and method for recovering a high yield of molybdenum oxide using a relatively non-corrosive stripping process
In accordance with various embodiments of the invention, a method for converting molybdenite to molybdenum oxides includes optionally deoihng the molybdenite concentrate, optionally metallurgically upgiading the concentiate, pressure leachmg a slurry of molybdenite concentrate, sepaiating the pressure leach discharge solids from the pressure leach discharge liquid, optionally washing the resultant discharge solids, extracting soluble molybdenum and optionally othei materials from a resultant filtiate using organic anionic solvent extraction techniques and/01 ion exchange techniques, stripping the loaded 01 game material with a basic solution (e g , an alkali metal base solution, such as a solution including an alkali metal hydioxide, alkali metal caibonate or bicarbonate, or an alkaline earth metal base solution, such as a solution including an alkaline earth metal carbonate 01 bicarbonate) iecycling the strip solution or a portion thereof to the pressuie leach operation, feed slurry tank, and/or a quench solution system, optionally extracting sodium fiom the iecycle strip solution with a strong cationic ion-exchange resin prior to recycling the molybdenum solution to the pressure leach system, and removing a small stream of concentrated strip solution to recover othei mateiials
In accoidance with additional embodiments of the invention, a system for converting molybdenite to molybdenum oxides includes (optionally) a deoilei, (optionally) a
metallurgical upgrade stage, a pressure leach vessel, a solid-liquid separation stage or stages, a solvent-extraction stage and/or a an ion exchange stage, a stripping stage, and optionally a cation-exchange stage
In accordance with various aspects of the exemplary embodiments, molybdenum oxide is recovered from molybdenum sulfide by initially providing filtered, dried, and optionally deoiled and/or upgraded M0S 2 , which may be fed directly from a prior concentration/isolation piocess step, repulped after such process steps, and/or provided from some othei source ot M0S 2 concentrate The M0S 2 concentrate is fed into a pressure leach vessel operating at, e g , about 225°C and about 450 psi and about 100 oxygen psi overpiessuie The M0S 2 concentrate may be fed to the pressure leach vessel continuously An oxygenated environment may be maintained in the piessure leach vessel through any suitable method, such as sparging oxygen into the pulp zone at about 100 psi overpressure Additionally, quench water and/or 01 coolant may be added to the vessel to maintain tempeiature and pressure The pressure leach vessel may also leceive a recycle stream including at least a portion of a liquid stream from a solid-liquid separation stage In some implementations, the recycle stieam from the solid-liquid separation stage overflow may improve the oxidation kinetics in the vessel and thus improve the overall recovery percentage of molybdenum from the molybdenum sulfide
The discharge from the pressure leach vessel may be depressuπzed in a flash tank before proceeding to the sohd-hquid separation stage In some configurations of the sohd- liquid sepaiation stage, at least 2 thickeners aie opeiated in countei-cuπent mode A portion of the solid-liquid separation stage leach liquor fiom, e g , a fust thickenei may iepoit to a solution extraction (SX) and/or an ion exchange circuit while another portion of the leach liquor may be recirculated or recycled back to the feed stream of the pressure leach vessel The solid-liquid separation stage liquid fraction stream proceeding to the solution extraction circuit may be filtered in one 01 moie filtration stages before proceeding to the SX circuit In the SX cncuit, solubilized matenals, such as Mo and Re values are lemoved fiom the solid-liquid separation stage liquid fraction stream via an organic stage The loaded oiganic is then washed and materials (e g , the Mo and Re values) are stripped with a basic solution The aqueous solution including the, e g , Mo and Re, values may then be further processed for final upgiading of rhenium and molybdenum The SX circuit may also pioduce a coppei beaiing acid solution, which may be further processed for ieclamation or recycling of the acid and the coppei
In continuing discussion of some exemplary configurations of the solid-liquid separation stage, the solids residue from the solid-liquid separation stage (e g , the last thickener thereof) is filtered using a filtration unit. The filtration unit may include a rotating drum, belt, pressure filter, or other conventional filter The filtrate is returned to the solid- liquid separation stage, to the solution extraction stage, and/or fed to the pressure leach vessel feed stream. The filtei cake from the filtration step includes oxide pioduct, which may be utilized or sent to further processing.
As one example of additional processing of the oxide, the wet filter cake from the filtration step described above may be further processed to produce one or more of commercial products or chemical product precursors, such as, for example, an ammonium dimolybdate (ADM) product.
Many features of the present disclosure will become manifest upon making reference to the detailed description which follows and the accompanying sheets of diawmgs in which preferred embodiments incorporating the principles of this disclosure aie provided as illustrative examples only.
Brief Description of the Drawing Figures
FIG. 1 illustrates a system for converting M0S 2 concentrate to molybdenum oxide; FIG. 2 illustrates a process for converting M0S 2 concentrate to molybdenum oxide; and
FIG 3 illustrates a schematic block flow-chart of a system foi additional processing of molybdenum oxide
Detailed Description The present disclosure refers to and describes a method, a processing system, and accompanying components and equipment. A substantial portion of the disclosure herein is directed to a system for and a method of processing molybdenite concentrates to produce molybdenum oxide and other compositions It should be appreciated that the broader process steps desctibed herein may be accomplished by a vaiiety of equipment configurations and sub-process steps, each of which are within the scope of the present invention. For example, the following disclosure describes filter systems on a number of occasions. Particular equipment is generally described as being suitable for particular filter systems. However, other equipment may be implemented or combined with other equipment to accomplish the function of a filter system described herein. Additionally or
alternatively, the present system and method may be implemented or adapted to process other starting materials and/or to produce different final products
With reference to FIG 1 and FIG 2, a system 10 and a process 200 to generate molybdenuim oxide product (MOO 3 ) from M0S 2 starting materials are respectfully illustrated The system components and process steps are illustrated in block diagram foimat to re-emphasizc that the present invention is not limited to any specific hardware 01 processing equipment, with many different types of operating components being suitable for use in the disclosed system and process
As illustiated in FIG 1 and FIG 2, process 200 initially involves a step 202 of pioviding a supply of molybdenum sulfide (MoS?), designated as ieference number 12 in FIG 1 Many of the initial steps in process 200, such as obtaining a molybdenum sulfide supply 12, are somewhat conventional and taught by numerous patents, including U S Pat No 5,804,151 , which shares common ownership with the piesent application For the purposes of completeness, a brief description of these initial steps is piovided herein in substantially the same foim as provided in U S Pat No 5,804,1 51, which is incorporated herein by reference in its entirety for all purposes
To obtain initial M0S 2 starting material 12, molybdenum sulfide is derived from a supply of molybdenite (MoS 2 -contaming) ore (not shown), which is available from numerous mine sites throughout the world For example, a representative mine site from which large supplies of molybdenite ore may be obtained is the Henderson mine at Empire, Colo (USA) This mine site is geneially chaiacteπzed as a "primary" mine which is capable of pioducing large amounts of lelatively puie pioduct How evei, of incieasing inteiest is "by-pioduct' molybdenite, which involves a secondary product combined with copper- containing materials obtained from "nonpπmary" mine sites (e g , the Sierπta Mine at Tucson, Ariz (USA) and others) System 10 and process 200 are capable of effectively processing both "pπmaiy" and "secondary" ore materials and should not be regarded as limited to any one type
Once obtained, the molybdenite ore may be theieafter processed in a conventional mannei to sepaiate the desued M0S 2 fiom the sunounding waste mateiial which is normally comprised of silicified granite and is commonly referred to as "gangue " A basic procedure for isolating the M0S 2 from other components of the molybdenite ore is described in U S Pat No 4,046,852 to Veites et al , which is hereby incorporated by reference for all that it discloses Essentially, the molybdenite oie, which may contain only about less than 1% by weight M0S 2 in the form of black, hexagonal ciystals, is first subjected to a size reduction
stage using a conventional size reduction (e g , grinding and crushing) apparatus known in the mining industry for this purpose A representative size reduction apparatus suitable for use with the system and process of the invention includes a standard impact milling system or ioll ciusher unit However, other grinding and crushing systems may also be used, with the present invention not being exclusively restricted to any particular type of si7e reduction apparatus
As a result of the grinding and crushing step described above, the molybdenite ore is converted into a giound oie product which is typically in particulate form having an average paiticle size of about 50 to about 300 miciometeis Theieaftei, the ground ore product may be tieated in many different ways to separate the desired M0S 2 therefrom F01 example, the ground ore product may be introduced into a conventional flotation extraction system which employs numerous ieagents including various hydrocarbon compositions, as well as selected wetting agents Flotation extraction systems are known in the mining industry, with specific information involving a lepresentative flotation-based extraction system tor processing molybdenite ore being described in U S Pat No 4,046,852, discussed above, and U S Pat No 3,834,894 to Spedden, et al , which is also incorpoiated heiein by refeience for all that it discloses A wide variety of different flotation chemicals may be used in connection with conventional flotation systems of the type described above including, but not limited to, butyl carbitol, allyl esters, and potassium xanthates Typically, the "float" product associated with a representative flotation extraction system will contain the desired isolated molybdenum sulfide that can be used as starting material 12 The "sink" product is piimaπly of the waste gangue, which may be discarded or further piocessed if desired Of course, it is common that such flotation extraction processes often utilize multiple, sequential flotation stages and may include intervening grinding steps, depending on the particular type of ore being piocessed and other extiinsic considerations Consequently, the present invention should not be regarded as limited to any particular flotation extraction procedures or other processes for obtaining molybdenum sulfide 12, with many othei conventional techniques being applicable as discussed above
At this stage, initial supply of molybdenum sulfide 12 is ready foi further processing, and will typically have a particle size of about 10 to about 100 micrometers Initial supply of molybdenum sulfide 12 will likely have a number of residual compositions associated therewith, which originated within the ore product Specifically, these materials are carried over into initial supply of molybdenum sulfide 12 fiom the ground ore product, with initial supply of molybdenum sulfide 12 normally containing about 0 2-35% by weight non-MoS?
materials These non-MoS 2 materials will typically include small amounts of residual gangue as well as various gangue-deπved metals and metal compounds (e g , metal oxides, chlorides, sulfides, and the like) which include, but are not limited to, the following metals potassium, manganese, sodium, lead, tin, magnesium, calcium, non, copper, bismuth, and aluminum The exact amount and concentration of these materials within molybdenum sulfide starting material 12 (with such materials collectively being referred to herein as "contaminants") will, of course, vary depending on the particular ore body from which the initial ore was obtained, as well as the level and/or type of preliminary treatment used to pioduce molybdenum sulfide starting material 12 As discussed furthei below, these natuially-deπved contaminants may be removed at some point during the molybdenum puiification process in order to prevent undesned contamination of the final molybdenum products (e g , products generated from molybdenum tπoxide (MOO 3 ) produced in accordance with process 200 described herein)
Depending on the level and type of contaminants present in molybdenum sulfide supply 12 and the filtiation steps desired aftei the oxidation of the M0S 2 in a pressure leach vessel 20, M0S 2 supply 12 may be subjected to one 01 moie additional piiiification steps prior to entering pressure leach vessel 20 For example, initial molybdenum sulfide supply 12 may by subjected to an optional deoiling step 204 and system 10 may include optional deoihng apparatus 14 Deoiling can be used to strip hydrocarbon material from the feed to produce an upgraded feed 16, which increases the effective kinetics of a pressure leach step 210, described in moie detail below Thus, incorporation of a deoiling stage facilitates maintenance of equipment of system 10 by icducing an amount of hydiocarbon material that is exposed to the equipment and incieases efficiency of process 200
Deoiling step 204 may be pei formed using eithei thermal or solvent deoiling techniques and apparatus An exemplaiy thermal deoiling piocess includes, e g , exposing the feed to an indirect fired rotary kiln Exemplary solvent deoiling processes include exposing the feed to an acetone or other solvent wash stage(s)
The feed may also be exposed to an optional hydrometallurgical upgrade apparatus 19 (step 206) Optional hydiometalliiigical upgiade step 206 may include vaπous purification sub-steps that may be implemented pnor to the pressuie leach vessel and may include one or more sub-steps and apparatus 19 may include one or more hardware components to accomplish the step(s) Optional upgrade step 206 may involve leaching of molybdenum sulfide supply 12 with a selected reagent or reagents (e g , HCl) to "upgrade" supply 12 or 16 to matenal 21, i e , preliminaiily remove, vaπous contaminant materials
from the molybdenum sulfide, such as extraneous lead. A representative hydrometallurgical upgrade step 206 may include the step of combining initial supply of molybdenum sulfide 12 or 16 with the selected reagent (e g , HCl) in a vessel to form a slurry The vessel may be provided with a stirrer to ensure a thorough dispersal of the solids in the slurry The slurry may then be filtered by a suitable filter to produce upgraded molybdenum sulfide-containing feed material 21 and a filtrate 18 containing contaminants (e.g., lead) solublizcd by the reagent. Filtrate 18 may then be disposed of or treated in any suitable manner. Again, it should be emphasized that hydrometallurgical upgrade step 206 is optional.
Although process 200 is illustrated with optional deoiling step 204 followed by optional hydrometallurgical upgrade step 206, when a process includes both steps 204, 206, the steps may be performed in any order. Aftei either step, feed material 21 is optionally repulped with a liquid 25 (step 208) to form a feed material 23, which is fed to pressure leach vessel 20.
As noted above, steps 204, 206, and 208 are optional, and thus feed material 23, 21, 19, and starting material 12 may be the same or altered by the optional processing steps and apparatus as described above. In any event, MoS 2 -containing feed material (e g., feed 23) is fed to pressure leach vessel 20, whether directly from the MoS? supply 12 or from the optional upgrade steps 204, 206. Feed material 23 may comprise an aqueous slurry comprising water and M0S 2 . Feed material 23 may assay at about 36-40% S, but may vary depending on the purity of the initial supply of molybdenum sulfide, the amount of contaminants, and treatment prior to entry of vessel 20. For example, it has been found that exposing feed material 12 to a deoiling process reduces an amount of total sulfur. Additionally or alternatively, the MoS^-containing feed material 23 may be provided in other suitable forms depending on the preceding process steps. For example, MoS?- containing feed material 23 may comprise a filter cake having less water than a slurry. As noted below, other streams may be fed to pressure leach vessel 20 to provide a suitable leach slurry 22 during an oxidation step in the pressure leach vessel (step 210).
By way of particular example, leach slurry 22 includes sulfuric acid to facilitate the oxidation reaction. And, in accordance with various aspects of the invention, a desired acid concentration is maintained by recirculating an acid discharge stream from step 212, as described below.
Pressure leach vessel 20 may be operated in either a batch mode or a continuous mode Pressure leach vessel 20 may include a heater and one or more mixing motors having corresponding blades or agitators. Pressure leach vessel 20 may also include one or more
sparger-type agitators through which a free oxygen-containing gas 24 from a supply 26 is admitted under pressure into pressure leach vessel 20 in the form of a stream of bubbles Since mechanical and spaiger-type agitators are well-known, the particular mechanical and sparger-type agitatois utilized in one piefeπed embodiment of the piessure leach vessel 20 are not desci ibed in further detail Pressure leach vessel 20 may include additional oi alternative components configured to facilitate effective mixing of the materials in leach slurry 22 within vessel 20, together with the proper temperatures and pressures for the desired oxidation reaction
As one example of a suitable combination of equipment for pressure leach vessel 20, the combination of mechanical and spaiger-type agitators has been found to provide a batisfactoiy degree of agitation to effect the continued dispersion of the molybdenum sulfide particles and also to effect an entramment of minute bubbles containing free oxygen (O 2 ) to effect oxygen mass transfer to the aqueous slurry The agitation of leach slurry 22 also promotes a mechanical scrubbing ol the particle surfaces for removing any film of molybdenum oxide formed thereon, thereby exposing fresh molybdenum sulfide for further ieaction with fiee oxygen
As intioduced above, the piovision of fiee oxygen into piessure leach vessel 20 may be accomplished in any suitable manner As one example, oxygen-containing gas 24 may be delivered from oxygen-containing gas supply 26 Exemplary oxygen-containing gases include puie oxygen gas, air/oxygen mixtures, and air, such as naturally occurring air Oxygen-containing gas 24 may be sparged into pressure leach vessel 20 directly into leach shiny 22 Additionally 01 alternatively, oxygen-containing gas 24 may be fed to pressure leach vessel 20 into a gaseous portion of the piessure leach vessel and allowed to mix with leach slurry 22 through the action of the mechanical agitators Spaiging oxygen-containmg gas 24 into leach sluiry 22 may be preferred due to the additional mixing and agitation effected thereby Other suitable methods of introducing oxygen into pressuie leach vessel 20 may alternatively be implemented Oxygen-containing gas 24 may be provided at any suitable piessure, such as a pressure gieater than the pressure in pressure leach vessel 20 In some implementations, oxygen-containing gas 24 may be sparged into leach sluπy 22 at about 100 psi overpressure
FIG 1 also illustiates that water 28 may be delivered to piessure leach vessel 20 from a suitable supply 30 Watei 28 is an example of an acceptable coolant 32 that may be added to pressure leach vessel 20 to maintain the oxidation reaction at a desned temperature and/or pressuie Other suitable coolants may be used as well, including coolants that
include water mixed with other components that may be selected to provide additional cooling and/or pressure control effects Water may be a suitable coolant due to its role in the oxidation reaction that converts MoS ? to MOO 3 Coolant stream 32 may be delivered from tresh supply 30 as illustrated and, additionally 01 alternatively, may be dehveied in whole 01 in part horn recycle streams onginating in other parts of the process, whethei upstream or downstream
A discharge 34 from pressure leach vessel 20 may be depressuπzed in a flash tank 36 before proceeding as a leach product stream 38 to a solid-liquid separation stage 40 (step 212) Stage 40 may comprise various apparatus, such as equipment suitable for counter- current decantation, thickening, filtration, and centπfugation
As indicated above, shiny 22 in the piessuie leach vessel 20 may be dt pressures gieatei than about 400 psi and at tempeiatuies gi eater than about 200 0 C (e g , about 200 0 C to about 250 0 C, preferably about 215 0 C to about 235 0 C) Depending on the configuration of the solid-liquid separation stage 40, it may be desirable to reduce the temperature and/or pressure of leach product stream 38 prior to entering stage 40 Flash tank 36 is one example of equipment that may be used to accomplish such temperature and/or pressure reductions, other equipment or combinations of components may be similarly implemented
In accordance with one embodiment of the invention, stage 40 is a countei-cui rent decantation circuit Suitable countei -current decantation circuits include at least 2 thickeners operated in counter-current mode The general principles of counter-current decantation are well-known and will not be fully explicated herein It is sufficient herein to summarize such circuits as including any number of thickeners, generally operated in series and in counter-cuπent mode
End product streams, or outputs, from stage 40 geneially include an overflow liquids fiaction 46 (e g , fiom a first thickenei 42) and a undeiflow solids pioduct 48 (e g , fiom the last thickener 44 in the series), consisting principally of solids In the context of the present disclosuie, stage 40 is implemented to accomplish solid/liquid separation of leach product stream 38 Depending on the condition of leach product stream 38 and other design and implementation options in the picscnt method and system, a CCD circuit may include gi eater 01 tewer thickeners as needed to accomplished the desπed separation at this stage of the piocess
As illustrated in FIG 1, a portion of liquids fiaction 46 from stage 40 may be diiected to a solution extraction (SX) circuit 50 while another portion of solid-liquid sepaiation stage liquids fiaction 46 may be recirciilated or recycled back to pressure leach
vessel 20 For purposes of clarity, the portion recycled to pressure leach vessel 20 is referred to herein as a leach recycle stream 52, while the portion directed to solution extraction circuit 50 is referred to herein as an SX feed stream 54
Relative amounts of liquids fraction 46 that become feed stream 54 and leach recycle stream 52 may vary accoiding to the oveiall design of the equipment providing the functions of the present invention Additionally or alternatively, the composition and/or flow rate or leach recycle stream 52 may be adjusted based on the reaction conditions of pressure leach vessel 20, such as to assist in creating the optimal reaction conditions In some implementations of the present invention, leach recycle stream 52 from overflow 46 may be adapted to impiove the reaction kinetics in pressure leach vessel 20 For example, leach iecycle stream 52 may improve the reaction kinetics by assisting in maintaining a desired temperature, acid concentration, and/or pressure Additionally oi alternatively, leach recycle stream 52 may improve the reaction kinetics by providing seed material to acceleiate the production of precipitates trom leach slurry 22 Leach recycle stream 52 may provide a variety of other benefits to the overall methods of the present disclosure A portion of overflow 46 may additionally oi alternatively be fed to feed stream 23 (prior to entering pressuie leach vessel 20)
As illustrated in Fig 1 , system 10 may optionally include an ion exchange stage 53 Stage 53 is generally designed to remove metals such as ihenium In the illustrated embodiment, ion exchange stage 53 is interposed between solid-liquid separation stage 40 and pressure-leach vessel 20, in a recycle loop However, stage 53 may additionally and/or alternatively be located elsewhere to capture metal values from solid-liquid stage 40 By way of one example, stage 53 is a sulfuiic acid ion exchange stage designed to remove rhenium fiom oveiflow 46 and/or leach recycle stream 52 With ieference again to FIG 1, SX feed stream 54 may be filteied in one or moie optional filtration stages 56 before pioceeding to SX circuit 50 SX circuit 50 may be adapted to extract molybdenum (Mo), rhenium (Re), and/or other metal values (e g , rare earth metals) from the SX feed stieam 54 Overflow 46 may include additional metal values oi othei compositions that aie commeicially valuable oi otheiwise useful in an opeiator's facility Foi example, oveiflow 46 that becomes SX feed stream 54 may include copper, iron, oi other metal values that wcie contained in the oπginal ore and/or gangue Depending on the composition of overflow 46, optional filtration stages 56 may be adapted to lemove one or moie of such metal values or other compositions Additionally oi alternatively, optional filtration stages 56 may be adapted to remove some or all of the relatively
invaluable contaminants from overflow 46, such as contaminants that may be remaining from the initial M0S 2 supply. In some implementations of the optional filtration stages, the filtrate will continue to SX circuit 50 as SX feed stream 54' with a filter cake 58 being directed to additional process steps, to disposal, or to other uses depending on the composition of the filter cake As can be understood from the foregoing discussion, a variety of filters and other equipment may be implemented as optional filtration stages 56 As filtration equipment and its opeiation is well understood, additional description of the various configurations will not be provided herein in the interest of brevity and clarity.
In accordance with one embodiment of the invention, in SX circuit 50, solubilized Mo and Re values are removed from SX feed stream 54 or 54', filter or unfiltered, via tiaditional solution extraction principles (step 214). Here again, general solution extraction techniques are well known and will not be described in detail; however, specific implementations and sub-steps in utilizing solution extraction at this point in the process to accomplish the results and functions described herein are believed to be not well known. Accordingly, components of SX circuit 50 are described along with at least one example of a method of using solution extraction to accomplish the desired extraction.
With continuing reference to FIG. 1 , SX circuit 50 may be implemented and adapted to extract Mo values and/or Re values from an aqueous stage into an organic stage. Additionally, SX circuit 50 may be adapted to leave copper values and/or other metal values in an acidic aqueous stage. As one example of a suitable solution extraction implementation, SX circuit 50 may utilize Alamine® 336, a tertiary amine having the chemical name of tricaprylyl amine, as the organic stage into which the Mo values and/or Re values are extracted. As shown in FIG. 1 , an organic feed 60 to SX circuit 50 may be delivered from an organic supply source 62. Additionally 01 alternatively, organic feed 60 may be delivered from other sources within the facility, such as via a recycle stream from other process steps, such as shown in FIG. 1 as an optional recycle stream 64. Alamine© 336 is one example of a suitable organic feed 60; other suitable organics may be similarly utilized in accordance with this illustrative embodiment, provided they are selected to extract at least one of the Mo and Re values from the aqueous stage. As introduced above, solution extraction circuit 50 may be adapted to leave certain metal values in an aqueous stieam 66. As illustrated in FIG. 1 , aqueous stream 66 may exit SX circuit 50 and proceed to additional processing apparatus 68 to recover those metal values. As one example, some implementations of the present invention may produce aqueous stage 66 including copper values in an acidic aqueous solution. In such circumstances, aqueous stream 66 may be
directed to additional processing facilities 68, such as additional leaching or solution extraction equipment and processes to recover and/or recycle copper and/or acid, each of which may have commercial or methodological advantages to implementers of the present invention Continuing with the discussion of the outputs from SX circuit 50, an organic stream loaded with, for example, Mo values and/oi Re values may be washed under appiopπate circumstances following an initial extiaction step A washed organic stage 70 may be directed to a stripping stage 72, where the loaded organic is stripped with basic solution (e g , an alkali metal base solution, such as a solution including an alkali metal (e g , sodium) hydroxide, alkali metal (e g , sodium or potassium) carbonate or bicarbonate, or an alkaline eaith metal base solution, such as a solution including an alkaline earth metal (e g , calcium) carbonate or bicarbonate) 74 to sti ip the Mo and/or Re values into the basic solution (step 216) By way of one example, a NaOH solution (about 15% NaOH in aqueous solution) is used as agent 76 for stripping step 216 However, other suitable stripping agents 76 may be used to put the Mo, Re, and/oi other values back into an aqueous solution for futther processing
A paiticular stripping agent 76 used may be selected based on the organic used in the SX ciicuit 50, on any subsequent piocessing stages 78 to which a snipped aqueous solution 80 will be subjected, and/or on other factors, such as cost and efficiency However, alkali metal and alkaline earth metal basic solutions are thought to be particularly advantageous, because they enable relatively lower acid concentrations, and hence less corrosive conditions, to be maintained in the piessure leach vessel 210 and subsequent processing stages Thus, equipment used for steps 210, 212, 214, and 216 may last longer, and theretoie an overall pioduction costs of molybdenum oxide may also be reduced Subsequent processing stages 78 may include a variety of suitable apparatus adapted to upgiade the ihenium and/or the molybdenum values according to the desπed end product As illustrated in FIG 1 , stripping agent 76 may be provided from a supply tank 82 Additionally or alternatively, stripping agent 76 may be supplied from other sources, such as iecycle stieams fiom one or more othei piocess steps opeiated by the implementers of the present invention In addition to stπpping the desired Mo and/or Re values into the aqueous stage, stπpping agent 76 may free the organic stage for other uses, such as optional iecycle stream 64 discussed above for use in SX circuit 50 Aqueous alkali metal base including the Mo and Re values may then be further processed for final upgrading of rhenium and molybdenum
As illustrated, a portion of stripped aqueous stream 80 may be recycled back to pressure leach vessel 20 and/or feed stream 23 Recycling a portion of stream 80 is advantageous because it increases the effective yield recovery of the molybdenum tπoxide to the solid phase from system 10 and process 200 System 10 and piocess 200 optionally respectfully include an alkali metal (e g , a sodium) removal apparatus and step 218 An exemplary removal step 218 employs an ion- exchange on a strong cation resin system 83 to remove at least some of the alkali metal ions before recycling a portion stripping discharge 80 to pressure leach vessel 20 or feed stream 23 Returning now to solid-liquid sepaiation stage 40 described above, underflow 48 and its subsequent processing will be described Underflow 48 may include a substantial portion of the solids from leach pioduct stream 38 As described above, underflow 48 generally comes from the solids product of the last thickener 44 in the series of thickeneis in the stage 40 Additionally or alternatively underflow 48 may include some or all of the solids product of the last thickener 44 together with one or more other components, such as portions of the solids pioduct from upstream thickeneis
Undeiflow 48 may be diiected to a filtiation unit 84 (e g , a CCD filtration unit), which may comprise any suitable combination of components to accomplish the desired filtration Exemplary configurations of filtration unit 84 include one or more rotating drums, belts, pressure filters, or other conventional filters A filtrate 86 from unit 84 may be returned to stage 40 as recycle stream 88 and/or may be directed to solution extraction circuit 50 as an SX feed stream 90 Relative pioportions of filtiate 86 that are utilized as recycle stieam 88 and SX feed stieam 90 may be customized by an implementer of the present invention to optimize the use of filtrate 86 A filter cake 92 from filtration unit 84 may include molybdenum oxide (e g , a primarily chemical grade oxide (CGO)) product 94 Product 94 may be directly utilized, such as in products, processes, or other uses, may be directly commercialized, such as sold to othei entities as a finished product for their use, and/oi may be furthei processed in systems toi fuithei iefinement to Mo chemicals, such as ammonium dimolybdate (ADM) The vaiious possible uses of pioduct 94 aie iepiesented collectively and schematically as additional pioducts 96
As one example of additional processing of oxide pioduct 94, wet filter cake 92 from filtiation unit 84 described above may be further processed to produce one oi more metallurgical products, an ammonium dimolybdate (ADM) pioduct, and the like A
schematic block diagram of a system 100 for producing ADM is illustrated in FIG 3 System 100 is merely illustrative of the various additional products 96 that may be implemented As illustrated in FIG 3, product 94 is delivered to system 100 from a supply 98 When system 100 is in close geographic and temporal proximity to system 10 described above, system 100 may be fluidly coupled to system 10, such that product 94 is delivered to system 100 directly from filtration unit 84 However, system 100 may be offset from system 10 for a number reasons that may lead to storing filter cake 92 from filtration unit 84 for a period of time before supplying cake 92 to system 100 In such circumstances, filter cake 92 may be stored, and in some circumstances shipped, before being utilized as supply 98 shown in FIG 3 Additionally oi alternatively, pioduct 94 illusliated as entering system 100 may be provided fiom a variety of other souices not limited to pioduction system 10 or process 200 described above
Regardless of the source of product 94 to system 100, product 94 will commonly be supplied in the form of a wet filtei cake, however, product 94 may be in other forms, such as dried and palletized product Product 94, whether in the form of a wet filter cake or otheiwise, is supplied to a dissolvei tank 102 Suitable conditions in the dissolver tank 102 will typically include elevated temperatuies with some agitation Such ieaction conditions may be maintained through a variety of suitable equipment and component configurations In dissolver tank 102, product 94 may be batch leached with, e g , an aqueous solution of ammonium hydroxide (NH 4 OH) 104 from a source 106 to produce ammonium dimolybdate (ADM), (NH 4 ) 2 Mθ 2 θ7, in solution Pioduct 94 may also be continuously leached in a similai mannei depending on the opeiating conditions In some implementations of the piesent embodiment, system 100 may be adapted to selectively leach product 94 in batch 01 continuous mode depending on othei process conditions As suggested by the foregoing discussion, product 94 and ammonium hydroxide 104 ieact in dissolver tank 102 to produce a leached slurry 1 10 that is directed from dissolver tank 102 to an ADM filtiation system 112 Product 94 may include contaminants and lmpiuities, some of which may not ieact in dissolvei tank 102 Exemplary solid impurities that may be piesent in product 94 include sulfide minerals and non-hexavalent molybdenum, which may not react in dissolvei tank 102 ADM filtiation system 1 12 may be adapted to sepaiate the ADM in an aqueous solution filtiate 1 14 fiom contaminants and other materials in a filter cake 116 Various components and subcomponents may be incorporated in filtration system 1 12 to accomplish the desired separation One exemplary ADM filtration system 1 12 includes a continuous belt pressure filter Filter cake 1 16 from ADM filtration
system 1 12 may be directed to a downgrade circuit 1 18, which may consist of two dryers operated in parallel Other suitable equipment may be included in downgrade circuit 1 18 to convert filter cake 1 16 into a downgraded oxide 120 Downgraded oxide 120 may be packaged and sold to customers as a low-grade metallurgical oxide 122 or the like ADM filtrate 1 14 from ADM filtration system 1 12 may proceed to an adjustment tank system 124, which includes a pH adjustment tank A discharge 126 fiom adjustment tank system 124 is dπected to a crystallizer system 128
Returning to crystallizer system 128, crystallizing may be peiformed in one oi more paiallel crystallizers operating at an elevated temperature Additional or fewer crystallizers may be used depending on the configuration of the overall system and the intended feeds and outputs from crystallizer system 128 Similarly, the temperature and other conditions in crystallizer system 128 may be varied to suit the other process configuration variables and the variables that may be present in the feed stream to crystallizer system 128 As illustrated in HG 3, ciystalhzei system 128 may also produce a iecycled ammonium hydroxide stream 108, which may be lecovered from the vapors leaving crystallizer system 128 Recycled ammonium hydroxide stream 108 from crystallizer system 128 is merely one example of the various efficiencies that may be obtained through recycle streams and other techniques to optimize the system 100
In addition to the vapor stream/recycled ammonium hydroxide stream 108 produced by ciystalhzei system 128, a crystallizer output stream 132 may be produced by crystallizer system 128, which output stream 132 may comprise crystals in solution Crystallizer output stieam 132 may be directed to a centrifugal sepaiation system 134 The crystals in solution may be sepaiated from the solution in any suitable manner, with centiifugal separation being a non-limiting example of suitable separation systems Accoidingly, centrifugal separation system 134 may include two or more types of centrifuges and/or two oi moie groups of centrifuges dedicated to diffeient separation objectives With continued reference to FIG 3, centiifugal sepaiation system 134 may be adapted to produce an ADM product stream 138 After exiting centrifugal separation system 134, ADM product 138 proceeds to an ADM drying stage 140, which may consist of two rotary kiln diyers operated in paiallel configuration at a temperature of between about 160 0 F and about 170 0 F Other suitable equipment and/or conditions may be utilized in ADM diying stage 140 Foi example, in some systems, it may be desirable to limit the tempeiatuie to less than about 175 0 F
It is believed that the disclosure set forth above encompasses at least one distinct invention with independent utility While the invention has been disclosed in the exemplary forms, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible The subject matter of the inventions includes all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/or properties disclosed herein
The method and system described herein may be implemented to convert molybdenum sulfide into molybdenum oxide Additionally, the present method and system may be utilized to further refine the oxide to produce low-grade metallurgical oxide and/or ammonium dimolybdate Additionally, the present method and system may be implemented to isolate copper and/or other metal values from the initial molybdenum sulfide concentrate materials Other advantages and features of the present systems and methods may be appieciated from the disclosure herein and the implementation of the method and system