CN115427592A

CN115427592A - Recovery of vanadium from slag material

Info

Publication number: CN115427592A
Application number: CN202080088812.XA
Authority: CN
Inventors: D·鲁宾逊; M·D·乌尔巴尼
Original assignee: Avanti Materials Co ltd
Current assignee: Avanti Materials Co ltd
Priority date: 2019-12-19
Filing date: 2020-12-08
Publication date: 2022-12-02
Also published as: CL2022001643A1; AU2020408368A1; EP4077751A4; WO2021119728A1; EP4077751A1

Abstract

A process for recovering vanadium from a vanadium-containing feed stream, the process comprising: subjecting the vanadium-containing feed stream to an acid leaching step to form a slurry comprising a pregnant leach solution containing dissolved vanadium and a solid residue; passing the product of the leaching step to a solid/liquid separation step to produce a pregnant leach solution containing dissolved vanadium; contacting the pregnant leach solution with a reducing agent to reduce one or more species in the pregnant leach solution; passing the pregnant leach solution to a precipitation step where the solution pH is increased to precipitate a vanadium product; and recovering the vanadium product from the solution.

Description

Recovery of vanadium from slag material

Technical Field

The present invention relates to a method for recovering vanadium from slag material. In particular, the process of the invention is suitable for recovering vanadium from steel slag by hydrometallurgical processing.

Background

The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge as at the priority date of the application.

Vanadium is most notably found in the iron deposit of magnetite and is usually present in the slag produced by the iron recovery process. To recover vanadium, the slag is usually treated by the so-called "salt roasting process". In the salt roasting method, vanadium slag is mixed with an alkali metal salt and roasted to produce sodium metavanadate. These valuable vanadium are subsequently leached with water. Subsequently, the valuable vanadate is precipitated from the leaching solution with ammonium metavanadate or ammonium polyvanadate. The high temperature roasting step is highly energy intensive and therefore the vanadium content in the slag needs to be at a certain level to make the process economical.

Many different hydrometallurgical processes have been used to process slag to recover vanadium. Such processes typically include an acid leaching step to extract the vanadium into solution. The main problem faced with the recovery of vanadium by hydrometallurgical means is that other metal species such as iron and titanium are often co-extracted with vanadium in the acid leaching step. The separation of vanadium from leach solutions that also contain dissolved iron species presents significant challenges. Most methods to achieve this are uneconomical. Both vanadium and iron can exist in multiple oxidation states and there are multiple degrees of coordination with different leaching systems and mixtures of species containing only these elements are quite complex. In addition, many vanadium and iron containing leach solutions also contain a myriad of other impurities including manganese, chromium, calcium, sodium, silica and aluminum. These impurities need to be considered in the recovery process. Thus, many conventional separation techniques and established reagents cannot cleanly separate vanadium from iron. To solve this problem, most methods require first treating the leach solution to remove these impurities, particularly iron and titanium, before extracting the vanadium. This adds complexity and overall cost to the process.

Throughout this specification, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated entity (integer) or group of entities but not the exclusion of any other entity or group of entities.

Summary of The Invention

According to a first aspect of the present invention, there is provided a process for recovering vanadium from a vanadium-containing feed stream, the process comprising:

subjecting the vanadium-containing feed stream to an acid leaching step to form a slurry comprising a pregnant leach solution (pregnant leach solution) containing dissolved vanadium and a solid residue;

passing the product of the leaching step to a solid/liquid separation step to produce a pregnant leach solution containing dissolved vanadium;

contacting the pregnant leach solution with a reducing agent to reduce one or more species in the pregnant leach solution;

passing the pregnant leach solution to a precipitation step where the solution pH is increased to precipitate a vanadium product; and

vanadium product is recovered from the solution.

In one form of the invention, the method further comprises the steps of: the vanadium product is directed to a purification loop to produce a purified vanadium product.

The process of the present invention is preferably suitable for recovering vanadium products from slag material from the steel industry. In addition to vanadium, these materials also contain iron and other species, such as titanium. The process of the present invention enables direct precipitation of vanadium products from pregnant leach solutions without the need to first remove iron species from the pregnant leach solution. This is advantageous in case vanadium recovery is targeted, since no separate impurity removal step is required before recovering vanadium.

In one form of the invention, the vanadium-containing feed stream comprises steel slag. Throughout this specification, unless the context requires otherwise, the term "steel slag" will be understood to refer to the slag by-product of a steel making process. As will be appreciated by those skilled in the art, when the iron-bearing material is exposed to high temperatures, the impurities or gangue material separate from the molten metal and are withdrawn as slag. This slag is subsequently cooled and forms a solid material.

In one form of the invention, the leach liquor (leach) used in the acid leach step is sulphuric acid, hydrochloric acid or carbonic acid.

In one embodiment of the present invention, the method further comprises the steps of:

the feed stream is subjected to a pretreatment process prior to the step of subjecting the feed stream to the leaching step.

In one form of the invention, the pre-treatment process includes a sieving step to remove oversize particles.

Preferably, the pre-treatment process comprises one or more size reduction steps. More preferably, the one or more size reduction steps comprise one or more of a crushing step, a grinding step and a milling step.

In one form of the invention, the pretreatment process includes one or more beneficiation steps. Preferably, the one or more beneficiation steps comprise one or more of a gravity classification step, a magnetic classification step and a flotation step.

In one form of the invention, the feed stream is subjected to a preleaching step prior to the leaching step. Preferably, the pre-leaching step comprises contacting the feed stream with water to produce a pre-leach slurry. More preferably, the pre-leach slurry is subjected to a thickening step to increase the solids concentration.

In one form of the invention, the step of subjecting the feed stream to a leaching step to form a slurry comprising a pregnant leach solution containing dissolved vanadium and a solid residue more particularly comprises subjecting the feed stream to a leaching step in one or more leaching reactors. Preferably, this step comprises subjecting the feed stream to a leaching step in two or more leaching reactors. More preferably, this step comprises subjecting the feed stream to a leaching step in three or more leaching reactors. More preferably, this step comprises subjecting the feed stream to a leaching step in four or more leaching reactors. More preferably, this step comprises subjecting the feed stream to a leaching step in five or more.

In one form of the invention, the step of subjecting the feed stream to a leaching step is carried out at atmospheric pressure.

In one form of the invention, the step of subjecting the feed stream to a leaching step is carried out at an elevated temperature.

In one form of the invention, the solid/liquid separation step comprises slurry treatment in a Counter Current Decantation (CCD) loop. In one embodiment, the CCD circuit comprises two or more thickeners arranged in series. In one embodiment, the CCD circuit comprises three or more thickeners arranged in series. In one embodiment, the CCD circuit comprises four or more thickeners arranged in series. In one embodiment, the CCD circuit comprises five or more thickeners arranged in series. In one embodiment, the CCD circuit comprises six or more thickeners arranged in series. In one embodiment, the CCD circuit comprises seven or more thickeners arranged in series.

In an alternative form of the invention, the solid/liquid separation step comprises slurry treatment in a filtration unit. Preferably, the filter device is a belt filter.

Preferably, the step of contacting the pregnant leach solution with a reducing agent reduces a substantial proportion of ferric ions present in the pregnant leach solution to ferrous ions. In one embodiment, at least 95% of the ferric ions present in the solution are reduced to ferrous ions. In one embodiment, at least 96% of the ferric ions present in the solution are reduced to ferrous ions. In one embodiment, at least 97% of the ferric ions present in the solution are reduced to ferrous ions. In one embodiment, at least 98% of the ferric ions present in the solution are reduced to ferrous ions. In one embodiment, at least 99% of the ferric ions present in the solution are reduced to ferrous ions.

In one form of the invention, the step of contacting the pregnant leach solution with a reducing agent targets a solution Eh of <250mV relative to an Ag/AgCl reference electrode.

In one form of the invention, the precipitation step comprises contacting the pregnant leach solution with a pH adjusting agent to increase the pH of the solution. Preferably, the pH adjuster is an alkaline substance. More preferably, the pH adjusting agent is selected from one or more of magnesium carbonate, sodium bicarbonate and sodium carbonate.

In one form of the invention, the precipitation step comprises raising the pH of the solution to at least 4. In one form of the invention, the precipitation step comprises raising the pH of the solution to at least 4.1. In one form of the invention, the precipitation step comprises raising the pH of the solution to at least 4.2. In one form of the invention, the precipitation step comprises raising the pH of the solution to at least 4.3. In one form of the invention, the precipitation step comprises raising the pH of the solution to at least 4.4. In one form of the invention, the precipitation step comprises raising the pH of the solution to at least 4.5.

In one form of the invention, the precipitation step comprises raising the pH of the solution to between 4 and 5.

In one form of the invention, the precipitation step comprises raising the pH of the solution to between 4.1 and 5.

In one form of the invention, the precipitation step comprises raising the pH of the solution to between 4.2 and 5.

In one form of the invention, the precipitation step comprises raising the pH of the solution to between 4.3 and 5.

In one form of the invention, the precipitation step comprises raising the pH of the solution to between 4.4 and 5.

In one form of the invention, the precipitation step comprises raising the pH of the solution to between 4.5 and 5.

In one form of the invention, the precipitation step is carried out prior to recovery of valuable iron from the pregnant leach solution.

In one form of the invention, a precipitation step is carried out prior to recovery of the valuable titanium from the pregnant leach solution.

In one form of the invention, the step of recovering the vanadium product includes passing the slurry formed in the precipitation step to a solid-liquid separation step to produce a solid vanadium product and a barren liquor. Preferably, the solid vanadium product is washed prior to further processing.

In one form of the invention, the purification loop more particularly includes a salt roasting step, a leaching step and an ammonium metavanadate precipitation step. Preferably, the purification loop further comprises V ₂ O ₅ And (4) a production step.

In an alternative form of the invention, the purification circuit more particularly comprises an acid leaching step and a vanadium solvent extraction step. Preferably, the vanadium solvent extraction step recovers vanadium as a vanadyl sulfate solution.

In an alternative form of the invention, the purification circuit more particularly comprises an ammonia leaching step, a vanadyl product precipitation step and a calcination step.

According to a further aspect of the invention there is provided a vanadium product obtainable by the above process.

According to a further aspect of the present invention there is provided a purified vanadium product obtained by the above process.

Brief Description of Drawings

Further features of the invention are described more fully in the following description of several non-limiting embodiments of the invention. The description is only intended to illustrate the invention. It is not to be understood as a limitation on the broad overview, disclosure or description of the invention as described above. The description is made with reference to the accompanying drawings, in which:

FIG. 1 is a flow diagram of a process for recovering a vanadium product; and

FIG. 2 is a flow diagram of various purification routes that may be used to purify the vanadium product produced in FIG. 1.

Description of the embodiments

The process of the present invention relates to the recovery of vanadium from vanadium-containing feed streams. In a very broad sense, the method comprises the steps of:

subjecting a vanadium-containing feed stream to a leaching step to form a slurry comprising a pregnant leach solution containing dissolved vanadium and a solid residue;

passing the pregnant leach solution to a precipitation step where the solution pH is raised to precipitate a vanadium product; and

recovering the vanadium product from the solution.

The recovered vanadium product contains a relatively high V among other precipitated solids ₂ O ₅ And (4) preparing the components. In one embodiment, the recovered vanadium product comprises at least 10% vanadium.

The method is suitable for recovering vanadium from steel slag. As will be appreciated by those skilled in the art, steel slag contains a large proportion of iron species. These iron species, along with other metal impurities, are co-extracted into the leach solution during the leaching step. These impurities need to be considered in the recovery process. The process of the present invention provides a process by which vanadium products can be selectively precipitated relative to the iron species present in the pregnant leach solution, thus enabling the direct recovery of vanadium from the pregnant leach solution without the need to first remove/recover iron.

In fig. 1, a method 10 for recovering vanadium in accordance with one embodiment of the present invention is shown. In this embodiment, the feed stream 12 is subjected to a pretreatment process 14 to render the feed stream suitable for further processing.

In the embodiment shown in the figures, the feed stream 12 is first directed to a primary crusher 16 to break up large pieces of the feed stream 12 for further processing. The resulting material from the primary crusher is directed to a primary mill to reduce the particle size of the feed stream 12. The resulting material is directed to screen 20 and all oversize 22 is directed to a tertiary crusher 24 and then to primary mill 18.

In one embodiment, the screen has a mesh size between 75 μm and 500 μm.

The ground material 26 is directed to a secondary grinding stage 28 to further reduce the particle size. The resulting material is directed to a cyclone separator 30 and any oversize particles 32 are recycled back to the secondary grinding stage 28. As will be appreciated by those skilled in the art, the cyclone separator 30 may be replaced by other particle size separating means, such as a screen.

In one embodiment, the secondary grinding stage reduces the particle size of the feed stream to below 150 μm. In one embodiment, the secondary grinding stage reduces the particle size of the feed stream to below 140 μm. In one embodiment, the secondary grinding stage reduces the particle size of the feed stream to below 130 μm. In one embodiment, the secondary grinding stage reduces the particle size of the feed stream to below 120 μm. In one embodiment, the secondary grinding stage reduces the particle size of the feed stream to below 110 μm. In one embodiment, the secondary grinding stage reduces the particle size of the feed stream to below 100 μm. In one embodiment, the secondary grinding stage reduces the particle size of the feed stream to below 90 μm. In one embodiment, the secondary grinding stage reduces the particle size of the feed stream to below 80 μm.

The processed feed stream is directed to a preleaching step (not shown) where it is contacted with water to produce a preleaching slurry 34. The slurry 34 is then directed to a thickening step 36 to remove excess water and produce a concentrated leach feed stream 38. The inventors have found that the pre-leaching step helps to remove excess lime and other water soluble materials from the feed stream and thus reduces the consumption of leach liquor in the subsequent leaching step. The solids content of the leach feed stream is controlled to a target solids content. The target solids content depends on the grade of the feed and the solids content is controlled so that there is sufficient water in the leach discharge to keep all soluble salts dissolved.

Preferably, the target solids content in the leach feed stream is between 5 wt% and 40 wt%. More preferably, the target solids content in the leach feed stream is between 20 wt% and 30 wt%. The inventors have found that the preferred target solids content in the leach feed stream depends on the grade of the feedstock. Generally, the higher the feed grade, the lower the target solids content.

The concentrated leach feed stream is directed to a leach circuit 40 where it is contacted with a leach liquor to leach vanadium and other metals into solution. In the embodiment shown in fig. 1, the leaching step is an acid leaching step and the leach liquor is sulfuric acid 42. The leaching loop 40 includes a plurality of leaching reactors arranged in series. Sulfuric acid 42 is added to the leaching reactor in sufficient excess to maintain the free acid concentration.

Although a tank leach process is described above, it is contemplated that one skilled in the art may select from any leach circuit available in the art to achieve the same effect.

In one embodiment, the concentration of sulfuric acid is in the range of 10% to 60% (w/w). In one embodiment, the concentration of sulfuric acid is in the range of 20% to 50% (w/w).

The leach can be exothermic and is typically run at elevated temperatures of 45-105 ℃ with or without the addition of heat.

The leaching step will produce a leach slurry 44 comprising a pregnant leach solution containing dissolved vanadium and other soluble metals and an undissolved material residue. The leaching step 40 also results in the precipitation of calcium sulfate with varying degrees of hydration and this will form part of the slurry 44. The amount of calcium in the feed stream 12 will determine the amount of calcium sulfate produced.

The leach slurry 44 is directed to a solid-liquid separation step to separate all solids from the pregnant leach solution. In the embodiment shown in fig. 1, the slurry 44 is directed to a Counter Current Decantation (CCD) loop 46. In the CCD circuit 46, the slurry 44 is washed in a series of thickeners until most of the dissolved metals are removed. To maximize recovery, the slurry 44 is directed to the first thickener and the wash is directed to the final thickener. The underflow (underflow) and overflow (overflow) flows in opposite directions to each other. Flocculant 48 may be added to one or more thickeners to aid in the separation process. The overflow 49 from the first thickener is directed to further processing for metal recovery. The final thickener underflow 50 contains a high level of calcium sulfate, which can be recycled for sale. The inventors have found that the use of a CCD loop 46 is advantageous because it includes multiple solids washing stages. This will ensure that a significant amount of soluble metals are separated from the solids produced during the leaching step. As discussed above, calcium sulfate is produced during the leaching reaction. The use of the CCD circuit 46 cleans this solid sufficiently to enable subsequent use.

Although the embodiment shown in the figures includes a CCD circuit 46, it is contemplated that other solid-liquid separation methods may be used. For example, the slurry may be directed to a filtration step using a belt filter or other filtration device. The filtration step preferably also comprises a washing step.

The pregnant leach solution 49 is directed to a reduction step 52 where it is contacted with a reducing agent 54. The step of contacting the pregnant leach solution 49 with the reducing agent 54 reduces a substantial proportion of the ferric ions present in the pregnant leach solution to ferrous ions.

Any reducing agent that helps to reduce a significant proportion of the ferric ions present in the pregnant leach solution to ferrous ions is suitable. In one embodiment, the reducing agent is a metal powder. Preferably, the metal powder is iron. In one embodiment, the reducing agent is selected from sodium sulfite, sodium metabisulfite, and sulfur dioxide.

Preferably, sufficient reducing agent is added to make the solution Eh <250mV versus an Ag/AgCl reference electrode.

After the reduction step 52, the rich leach solution is directed to a precipitation step 56 where the pH of the solution is raised to precipitate the vanadium product. As the reduction step 52 reduces the ferric species to ferrous ions, the increase in pH will precipitate the vanadium product with a high degree of selectivity relative to the iron and other impurity metal ions in solution.

In one embodiment, the pH of the solution is increased by the addition of a pH adjusting agent 58. Preferably, the pH adjuster 58 is an alkaline substance. In one embodiment, the pH adjusting agent 58 is selected from one or more of sodium bicarbonate and sodium carbonate.

In one embodiment of the invention, the pH is raised above 3. In one embodiment of the invention, the pH is raised above 3.5. In one embodiment of the invention, the pH is raised above 4.

In one embodiment of the invention, the pH is raised to between 3 and 4.5. In one embodiment of the invention, the pH is raised to between 3.5 and 4.5. In one embodiment of the invention, the pH is increased to between 4 and 4.5.

The resulting slurry 60 is directed to a solid liquid separation step 62 to recover a precipitated vanadium product 64. In one embodiment, the solid-liquid separation 62 step includes a filtration step to recover the vanadium product 64. Preferably, the recovered vanadium product 64 is washed to remove entrained iron and other impurities.

The filtrate 66 from the solid-liquid separation step 62 is a ferrous sulfate solution containing dissolved impurity metals. The filtrate 66 is directed to a neutralization circuit 68 where it is contacted with a neutralizing agent, such as lime 70, to increase the solution pH and precipitate the iron-rich calcium sulfate residue and the aqueous effluent. The residue 72 is recovered in a solid liquid separation step 74 and sent to disposal.

The vanadium product 64 contains a mixture of vanadium oxides and hydroxides having different degrees of hydration. In one embodiment, the vanadium product 64 contains about 10% to 40% V ₂ O ₅ And (3) equivalent weight. The vanadium product 64 may be dried and sold as a final product. Alternatively, the vanadium product 64 can be directed to a purification loop to increase vanadium purity.

In fig. 2, three alternative purification loops are shown.

In the first embodiment, the purification loop more specifically includes a salt roasting step 78, a leaching step 80, and a precipitation step 82. In the salt roasting step 78, the vanadium product 64 is roasted at an elevated temperature in the presence of a salt 84. In one embodiment, the salt is an alkali or alkaline earth metal salt, preferably sodium carbonate. The amount of salt in the calcination step depends on the vanadium content. In one embodiment, at least 5% w/w salt is added to the vanadium product 64. If the vanadium product 64 contains about 18% vanadium, about 7-8% w/w salt is added to the vanadium product 64.

In one embodiment, the calcination step 78 is performed at a temperature of at least 1,000 ℃.

In one embodiment, the residence time of the calcining step 78 is at least 1 hour.

The calcine is directed to a leaching step 80 to dissolve the vanadium species. Preferably, the leaching step comprises contacting the calcine with water.

In one embodiment, the leaching step is carried out at a temperature of at least 70 ℃.

In one embodiment, the leaching step is carried out for a residence time of at least 1 hour.

The vanadium-containing aqueous solution can be treated by known methods to recover vanadium. In one embodiment, aluminum sulfate is first added to the warm vanadium solution to facilitate silica (and alumina) removal. After filtration, the purified vanadium solution is treated with ammonium sulfate in a precipitation step 82 to precipitate ammonium metavanadate 86. The ammonium metavanadate can then be isolated and subjected to a calcination step to produce a solid V ₂ O ₅ 。

In a second embodiment 88, the purification loop includes an acid leaching step 90 to leach vanadium into solution. The pregnant leach solution is directed to a solvent extraction step 92 for recovery of vanadium. For most efficient separation of vanadium from iron, vanadium and iron in higher oxidation states are preferred in the solution. The acid strength and addition of oxidizing agents need to be optimized to economically achieve this oxidation, phosphine oxides (e.g., cyanex 923) or amine reagents (e.g., alamine 336) can be used to selectively extract vanadium. Preferably, the vanadium solvent extraction step will recover the vanadium as vanadyl sulfate solution 94.

In the third embodiment 96, the purification loop includes an ammonia leach step 98 in which it is contacted with an alkaline lixiviant to leach vanadium into solution. Preferably, the alkaline leaching agent is selected from NaHCO ₃ Or NH ₄ And (5) OH. The pregnant leach solution is directed to a precipitation step 100 where it is contacted with an ammonium species to precipitate NH ₄ VO ₃ . The resulting precipitate may be recovered and directed to calcination step 102 to produce V ₂ O ₅ And (6) a product 104.

Example 1

The steel slag sample is from a steel production plant. Chemical analysis of the material was performed and showed that the material contained 2.46% V, 17.9% Fe and 0.72% Ti.

The material was subjected to a sulphuric acid leach step using 50% sulphuric acid and 22% solids (1800 kg/t acid addition). The leaching is carried out at a temperature of 100 ℃. The leaching curve is provided in figure 3. It will be noted that the leaching kinetics are fast and the extraction yield is high (> 99% v). The resulting leach solution was separated from the solids and each was chemically analyzed. The leachate contained 10.4g/L V, 78g/L Fe and 2.8g/L Ti. The final residue contained 25.8% Ca, 4.0% Si, 100ppmV, 1000ppmFe and 200ppmTi.

Example 2

A composite steel slag sample (400 grams) was added to 400gpl of sodium carbonate (formulated in Perth scheme water) at a slurry density of 15 wt% solids and stirred in a glass reactor. Hydrogen peroxide was added periodically to keep the Eh near zero. The test was held at 90 ℃ for 12 hours. No kinetic samples were taken. The test was terminated after 12 hours, and the slurry was filtered, analyzed and stored. The results are shown in table 1:

TABLE 1

The leaching was successful, achieving moderately high vanadium extraction rates. The addition of peroxide is hindered due to the flashing off of oxygen caused by the addition at high temperature. As expected, the mass increase was significant (50%) due to carbonate formation.

Example 3

The steel slag sample was subjected to sulfuric acid leaching and the filtrate was separated. Adding iron powder into the leaching solution. The target is Eh <250mV Ag/AgCl. The solution pH was raised to 4 by the addition of lime to precipitate the vanadium product. Achieving essentially complete vanadium precipitation (99.6%), formation of high grade precipitate (18.3%.

Example 4

A study of possible purification routes was carried out on the precipitated product of example 3. The sample was extracted with 150gpl of sodium carbonate at 90 ℃ for 6 hours. Leaching caused about 20% mass loss. Vanadium was leached but the extraction rate was significantly lower than expected (19.8%). There are no impurities (iron and titanium) in the leach solution.

As a result of the sodium carbonate leaching of the vanadium precipitate, the leaching is repeated in the presence of an oxidizing agent to facilitate the extraction. The addition of peroxide is done in stages. The initial Eh was-390 mV and increased to >0.Eh continues to decrease and is highest after 2 hours (pinned up). The vanadium extraction rate is significantly improved (70.1%) and the mass loss is also the same (39%). Very few impurities are also present in the leachate.

The experiment was repeated with 400gpl of sodium carbonate. This test achieved an improvement over the previous results, showing an extraction of 83.5%. The results are shown in table 2.

TABLE 2

Example 5

The vanadium product from example 3 was subjected to a salt roasting method to determine the effectiveness of this method in purifying the vanadium product.

Head sample (head sample) 16% V (details see below) and in the first SRL, 10% w/w Na was used ₂ CO ₃ As salt addition, the test was carried out as follows:

calcination temperature 1200 ℃ and residence time 2 hours

Aqueous leaching at 90 ℃ and 2 h residence time

Further adding 10% w/w Na ₂ CO ₃ A second SRL test was performed under the same operating conditions.

The results are shown in table 3. Overall, the vanadium extraction was about 97% and the total salt addition corresponded to 11.5% w/w (which is much higher than normal SRL operation due to the very high V content in the feed).

TABLE 3 analysis of solids

The water leachates from the previous operations are combined and AMV is then made into V using standard methods and chemistry ₂ O ₅ . Product V from SRL process performed on this high V intermediate ₂ O ₅ Analysis of composition ofShown 54.8% v, the main impurity is silica, which is likely an artifact (artemi fact) from product milling prior to analysis.

Example 6

The vanadium product was subjected to an alkaline leaching process to determine the effectiveness of this process in purifying the vanadium product.

While 112 g of h2o2 (30%) was added, 84% V of a 400g high V intermediate sample was dissolved in 1 l sodium carbonate solution (made by dissolving 400g sodium carbonate in 1 l water) and held at 90 ℃ for 12 hours. The equivalent weight of iron and titanium entering the PLS is less than 1% of the amount in the high V intermediate feed.

This V PLS can be precipitated by ammonium metavanadate using standard methods and V ₂ O ₅ Producing and processing.

Throughout this specification, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated entity (integer) or group of entities but not the exclusion of any other integer or group of integers.

Claims

1. A process for recovering vanadium from a vanadium-containing feed stream, the process comprising:

subjecting the vanadium-containing feed stream to an acid leaching step to form a slurry comprising a pregnant leach solution containing dissolved vanadium and a solid residue;

recovering the vanadium product from the solution.

2. The method according to claim 1, wherein the method further comprises the steps of:

the vanadium product is directed to a purification loop to produce a purified vanadium product.

3. A method according to claim 2, wherein the purification loop comprises a salt roasting step, a leaching step and an ammonium metavanadate precipitation step.

4. The process of claim 2, wherein the purification loop comprises an acid leach step and a vanadium solvent extraction step.

5. The method of claim 2 wherein the purification loop includes an ammonia leach step, a vanadyl product precipitation step, and a calcination step.

6. The method according to any of the preceding claims, wherein the method further comprises the step of:

7. A process according to any one of the preceding claims wherein the feed stream is subjected to a preleaching step prior to the leaching step.

8. A method according to any one of the preceding claims, wherein the step of contacting the pregnant leach solution with a reducing agent reduces a substantial proportion of ferric ions present in the pregnant leach solution to ferrous ions.

9. A method according to any one of the preceding claims, wherein the step of contacting the pregnant leach solution with a reducing agent targets a solution Eh of <250mV relative to an Ag/AgCl reference electrode.

10. A process according to any one of the preceding claims, wherein the reducing agent is selected from metal powders, sodium sulphite, sodium metabisulphite and sulphur dioxide.

11. A method according to any one of the preceding claims, wherein the precipitation step comprises contacting the pregnant leach solution with a pH adjusting agent to increase the pH of the solution.

12. The method according to any one of the preceding claims, wherein the precipitation step comprises raising the solution pH to at least 3.