OA21506A - Treatment of hydrous ore materials. - Google Patents

Abstract

A method of treating a hydrous ore material metal values includes a digestion step in which a solution of ferrous chloride (FeCI2) and a divalent chloride of the at least one other metal (M2+Cl2) is produced by contacting the hydrous ore material with gaseous hydrochloric acid. In a crystallisation step, crystallising a solid ferrous chloride hydrate (FeCI2-xH2O, wherein x>1) and a solid divalent chloride hydrate of the at least one other metal (M2+Cl2-zH2O, wherein z>1) from the solution. In a dehydration step, the FeCI2-xH2O and the M2+CI2-zH2O are subjected to temperature treatment to produce FeCI2-yH2O, wherein x>y>0, and M2+Cl2-aH20, wherein z>a>0. In a thermal decomposition step, the FeCI2-yH2O is 0 decomposed to produce anhydrous gaseous hydrochloric acid (HCI), which is used as the digestion reagent in the digestion step.

Description

TREATMENT OF HYDROUS ORE MATERIALS

FIELD OF THE INVENTION

THE INVENTION relates to the treatment of hydrous ore materials to liberate métal values contained therein. The invention provides a method of treating a hydrous ore material and extends to a process of treating a hydrous ore material.

SUMMARY OF THE INVENTION

IN THIS SPECIFICATION the provision of features in parenthesis contribute to the substantive content of the spécification and therefore to the characterisation of the invention. In particular, in cases in which generic Chemical formulae and numerical values for symbols of such generic formulae are provided in parenthesis, this should be interpreted as contributing substantively to the characterisation of the invention.

IN ACCORDANCE WITH THE INVENTION IS PROVIDED a method of treating a hydrous ore material that comprises iron (Fe), in metallic or compound form, and at least one other métal (M), in metallic or compound form, to recover the iron and the at least one other métal from the hydrous ore material separately of each other, in metallic or compound form, the method including . in a digestion step, producing a solution of ferrous chloride (FeCI₂) and a divalent chloride of the at least one other métal (M²⁺CI2) (FeCI2-M²⁺CI2 solution) by contacting the hydrous ore material with a digestion reagent in the form of gaseous hydrochloric acid (HCl), and reducing any ferrie iron (Fe³⁺) in solution, typically présent as FeCh, to ferrous iron (Fe²⁺) in solution, typically présent as FeCI₂, using a reducing agent;

in a crystallisation step, crystallising a solid ferrous chloride hydrate (FeCI₂-xH₂O, wherein x>1, more preferably x>1, x preferably being 4) and a solid divalent chloride hydrate of the at least one other métal (M²⁺CI2-zH2O, wherein z>1) from the FeCI2-M²⁺CI2 solution;

in a déhydration step, subjecting the FeCI₂-xH₂O and the M²⁺CI2-zH2O to température treatment to produce a solid partially dehydrated ferrous chloride hydrate (FeCI2-yH2O, wherein x>y>0, preferably being 1) and at least one of a solid partially dehydrated divalent chloride hydrate and a solid divalent chloride of the at least one other métal (M²⁺CI2-aH₂O, wherein z>a>0);

in a thermal décomposition step, subjecting the FeCI₂-yH₂O and the M²⁺CI₂-aH₂O to température treatment and thus decomposing the FeCI₂-yH₂O to produce solid ferrie oxide (FegOs), gaseous hydrochloric acid (HCl), and solid divalent chloride of the at least one other métal (M²⁺Cl2, i.e. wherein a=0); and using the gaseous hydrochloric acid thus produced as the digestion reagent in the digestion step.

In the sense used in this spécification, the term “hydrous ore material” means ore material that comprises chemically bound water (as opposed to “free water”, i.e. water in the form of H₂O that is not chemically bound), typically in a range of from about 5% to about 70% by weight, e.g. comprised in métal hydrates and/or métal hydroxides contained in the ore. For example, the hydrous ore material may be a clay-based ore material, such as, in particular, a latente ore material, e.g. limonite, saprolite etc.

Significantly, the method may be, and preferably is, subject to the proviso that the hydrous ore material is not subjected to a drying or déhydration operation prior to treatment thereof according to the method of the invention.

The hydrous ore material may comprise, in addition to chemically bound water, some free water.

For the purpose of performing the method, the hydrous ore material may include, for example, free water of up to 5% based on the weight of the hydrous ore material.

The method may therefore include a prior step of adding free water to the hydrous ore material, for the hydrous ore material used in the method to hâve a free water content of up to 5% based on the weight of the hydrous ore material.

Contacting the hydrous ore material with the digestion reagent may include, or may be preceded by, size réduction of the hydrous ore material. Size réduction of the hydrous ore material may be performed to increase the surface area of the hydrous ore material that is available to be contacted by the digestion reagent.

Thus, the method may include either subjecting the hydrous ore material to size réduction and, subsequently and separately, contacting the hydrous ore material with the digestion reagent, or it may include subjecting the hydrous ore material to size réduction while contacting the hydrous ore material with the digestion reagent.

Size réduction of the hydrous ore material may be effected through milling, e.g. using ceramic milling media, or through shredding, slicing, breaking, crushing, or any similar sizereducing action.

It is noted that, in treating hydrous ore materials of the type to which the invention relates, size reducing operations such as milling are atypical, particularly insofar these may be applied to such ore materials before they are subjected to déhydration which, as mentioned above, the présent invention seeks to avoid.

Réduction of ferrie iron in solution to ferrous iron in solution will only be performed if there is any ferrie iron in solution. In the case of latérite ore materials, it is expected that ferrie iron in solution would be produced by the digestion step.

The crystallisation step may, for example, be performed as an evaporative crystallisation step, i.e. by evaporating water from the FeCI₂-M²⁺Cl2 solution and thus cause crystallisation of the FeCI2-xH2O and the Μ²⁺Ο2·ζΗ₂0.

The at least one other métal may comprise one or more of copper (Cu), nickel (Ni), and cobalt (Co), in a metallic or compound form. Typically, the other métal would at least be nickel.

Preferably, the hydrous ore material may be ore from a lateritic nickel ore resource, e.g. a saprolitic nickel ore resource.

Depending on the composition of the hydrous ore material, the FeCI₂-M²⁺CI₂ solution may therefore contain, in addition to FeCI₂, NiCI₂ and, possibly, CuCI₂ and/or CoCI₂. Other metals may also be included.

The digestion step may be performed at a température of from 10°C to 120°C.

Metallic iron may be used as the reducing agent.

In using metallic iron as the reducing agent, in addition to réduction of Fe³⁺ to Fe²⁺, other metals may be reduced, possibly to solid metallic form, thus rendering such metals readily recoverable by solid-liquid séparation from the FeCI2-M²⁺CI2 solution.

The method may include, in a first séparation step performed after the digestion step, separating solids from the FeCl2-M²⁺CI₂ solution by means of solid-liquid séparation, thus recovering the FeCl2-M²⁺Cl2 solution substantially free of solids.

The FeCI₂.xH₂O may, in particular, be FeCl2.4H₂O (ferrous chloride tetrahydrate).

The method may include, . in a second séparation step, performed after the crystallisation step and before the déhydration step, recovering the solid FeCUxHkO and the solid M²⁺Cl2-zH₂O from the crystallisation step. Such séparation may be from residual liquid in the crystallisation step, if any.

The déhydration step may include subjecting the solid FeCk-xFfiO and the solid h/PCUzFEO to température treatment to produce the solid FeCl2-yH2O and the solid M²⁺Cl2-aH₂O.

The FeCI₂-yH₂O may, in particular, be FeCI₂-H₂O (ferrous chloride monohydrate), i.e. y=1.

The température treatment in the déhydration step may include subjecting the FeCk.xFEO and the M²⁺CI₂-zH₂O to a température in a range of from 70°C to 200°C, more preferably in a range of from 70°C to less than 200°C, i.e. at a température less than 200°C but not lower than 70°C. For example, the température may be a température in a range of from 70°C to 150°C

The déhydration step may be performed under non-oxidising conditions. This may include avoiding, or at least limiting, the presence of exogenous oxygen in the drying step. This may, in turn, include performing the déhydration step under positive pressure in a steam environment, which steam may be that which is produced as a resuit of the déhydration of the FeCl2-xH₂O and the Μ²⁺ΟΙ2·ζΗ2Ο to produce the FeCI2-yH2O and the M²⁺Cl2-aH2O.

In the thermal décomposition step, any M²⁺Cl2-aH2O (wherein a>1) produced in the déhydration step would be fully dehydrated, i.e. to form M²⁺CI2-aH2O (wherein a=0). Thus, solid product emanating from the décomposition step would, in addition to the ferrie oxide, include only M²⁺Cl2-aH2O (wherein a=0), i.e. M²⁺CI2, comprising any M²⁺Cl2-aH2O (wherein a=0) that was produced in the déhydration step and any M²⁺Cl2-aH₂O (wherein a=0) that was produced in the thermal décomposition step.

The thermal décomposition step may be performed at a température of from 200°C to 600°C, more preferably at a température above 200°C, up to 600°C.

The thermal décomposition step may be performed under oxidising conditions, i.e. in the presence of oxygen which may be supplied, for example, by air.

The gaseous HCl that is produced in the thermal décomposition step may be substantially dry, i.e. devoid of moisture (i.e. anhydrous).

Reactions that occur in the drying (déhydration) and thermal décomposition steps therefore comprise (i) Drying (déhydration) at températures described above, under non-oxidising conditions

FeCI₂.4H₂O (s) A FeCI₂.H₂O (s) + 3H₂O (g) (ii) Thermal décomposition under oxidising conditions, in the presence of oxygen (¹ΑΟ₂) supplied by air, at températures described above

2FeCI₂.H₂O (s) -» Fe₂O₃ (s) + 4HCI (g)

As alluded to above, the température at which température treatment is performed in the thermal décomposition step may be selected such that thermal décomposition of FeCI₂-yH₂O occurs and thermal décomposition of the M²⁺CI2-aH2O does not occur, i.e. such that thermal décomposition FeCI2-yH2O occurs to the exclusion of the M²⁺CI2-aH₂O, while any M²⁺CI2-aH2O (wherein a>1) becomes fully dehydrated to produce solid M²⁺CI2.

Therefore, in such a case, the thermal décomposition step would produce a mixture of solid Fe₂O₃ and solid M²⁺CI₂, in addition to the HCl gas.

The method may then include, in a third séparation step, dissolving the M²⁺CI₂ in water, and performing a solid-liquid séparation to recover the Fe₂O₃ from the resulting solution, thus recovering the at least one other métal and the iron separately of each other.

From the resulting M²⁺CI₂ solution, such other metals may then be recovered by conventional methods, e.g. hydrometallurgical methods.

The method thus also produces saleable Fe₂O₂ and products suitable for recycle to earlier method steps. Most notably in this regard, it is noted that the thermal décomposition of FeCI₂-yH₂O by means of température treatment releases anhydrous HCl gas. The method therefore includes recycling this HCl gas to and using this HCl gas in the digestion step as the digestion reagent.

It is regarded as a particular advantage, and inventive feature, of the invention as described, that the production of FeCI₂.xH₂O and subséquent déhydration thereof to FeCI₂.yH₂O enables, through subséquent décomposition of the partially dehydrated FeCI₂.yH₂O, the production of HCl in gaseous form which is, as will be appreciated, concentrated, undiluted, and anhydrous HCl. This is in stark contrast to conventional methods exploiting HCl, which unavoidably form dilute solutions of HCl due to water balances that are unfavourable to the production of concentrated HCl, and even to the production of desired concentrations of diluted HCl. For example, while the maximum concentration of HCl at room température is around 33% v/v, existing methods exploiting HCl rarely achieve a régénération of diluted HCl above 18% v/v. The présent invention addresses this elegantly, by taking a route of iron précipitation as FeCI₂.xH₂O, partial déhydration thereof to produce FeCI₂.yH₂O, and • décomposition thereof in turn to produce undiluted gaseous HCl for use in earlier method steps.

THE INVENTION EXTENDS TO a process for performing the method of the method of the invention, which process includes process stages and process operations corresponding to and for performing the respective method steps.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT

THE INVENTION WILL NOW BE DESCRIBED IN MORE DETAIL with reference to the accompanying diagrammatic drawing which shows a process according tb the invention.

Referring to the drawing, reference numéral 10 generally indicates a process according to the invention, for performing a method of the invention.

The process 10 includes the following process stages:

- an oxidative/reductive digestion stage 1,2;

- a réduction stage 14;

- a first séparation stage 16;

- a crystallisation stage 18;

- a second séparation stage 20;

- a drying stage 22;

- a thermal décomposition stage 24;

- a third séparation stage 26;

- a metals recovery stage 30.

In the process 10, the following feed, transfer, withdrawal, and recycle lines are identified:

- feed line 32;

- transfer line 38;

- feed line 40;

- transfer line 42;

- withdrawal line 44;

- transfer line 46;

- heating line 48;

- recycle line 50;

- transfer line 52;

- recycle line 56;

- transfer line 58;

- transfer line 60;

- transfer line 62;

- transfer line 64;

- transfer line 66;

- recycle line 70;

- withdrawal line 72; and

- feed line 74.

In using the process 10 to perform the method of the invention, a hydrous ore material is fed to the digestion stage along feed line 32 and is, in the digestion stage 18, subjected to milling in a mill and, in doing so, is upgraded to a water content of 5% w/w free water by the addition of water. The hydrous ore material is then contacted with anhydrous gaseous hydrochloric acid in the mill, while being subjected to milling, along recycle line 50, such gaseous hydrochloric acid being produced as hereinafter described.

Digestion of the hydrous ore material proceeds in the digestion stage 12 to produce a FeChM²⁺Cl2 solution, wherein M comprises Ni and possibly one or more of Co and Cu. If the hydrous ore material is a latérite ore material, the digestion stage 12 may first typically produce ferrie iron as FeCIs, requiring réduction thereof to FeCL.

The solution produced by the digestion stage 12 is thus transferred from the digestion stage 12 to the réduction stage 14 along transfer line 38, where it is contacted with a reducing agent that is fed to the réduction stage 14 along feed line 40, preferably being in the form of elemental iron or a source of ferrie iron (e.g. FeaOa), to produce the FeCl2-M²⁺Cl2 solution.

The FeCl2-M²⁺Cl2 solution is then transferred from the réduction stage 14 to the first séparation stage 16 along transfer line 42, where solids contained in the FeCl2-M²⁺Cl2 solution are sepârated from the FeCI2-M²⁺CI2 solution and are withdrawn along withdrawal line 44.

The recovered FeCl2-M²⁺CI₂ solution is then passed from the first séparation stage 16 to the crystallisation stage 18 along transfer line 46. Here, solid FeCfe-xfW (x>1, more preferably x>1) and solid IVPCh-zhbO (z>1) are crystallised from the FeCl2-M²⁺Cl2 solution through evaporative crystallisation by the addition of heat, as represented by heating line 48.

Typically, the value of x would be 4, and therefore the solid FeCUxFEO would be FeCI₂-4H₂O (i.e. ferrous chloride tetrahydrate).

The solid FeCI₂-xH₂O and the solid M²⁺CI2-zH2O, in aqueous suspension, are then transferred to the second séparation stage 20, along transfer line 52, where the solid FeCk-xFEO and solid M²⁺CI2-zH₂O are recovered from residual liquid and are withdrawn along transfer line 58. The solid FeCI₂-xH₂O and the solid M²⁺CI₂-zH₂O are then transferred to the déhydration stage 22 along transfer line 58. Of course, if there is no residual liquid from which to recover the solid FeCla-xbfeO and solid IVPCEzhW, then the second séparation stage 20 may be omitted.

In the déhydration stage 22, the solid FeCfe-xFhO and solid M²⁺Cl2-zH2O are subjected to déhydration in a non-oxidising environment, using température treatment at a température below 200°C but not less than 70°C, more preferably a température in a range of 70°C to 150°C, thus producing solid FeCI2-yH2O and solid M²⁺CI2-aH₂O (x>y>0; z>a>0, wherein y is preferably 1).

More specifically, the solid FeCI₂-xH₂O and solid M²⁺CI₂-zH₂O are fed into, and through once converted, a non-vented vessel in which the température treatment is carried out, thus producing a positive pressure inside the vessel resulting from steam that is formed inside the vessel due to the température treatment and the resulting déhydration of the FeCI₂-xH₂O at least, which steam serves to displace oxygen that may be présent in the vessel, e.g. in the form of air, thus avoiding oxidisation of the ferrous chloride.

The solid FeCI₂yH₂O and the solid M²⁺CI2-aH2O are transferred, along transfer line 60, to the thermal décomposition stage 24, in which the solid FeCI2-yH2O and the solid M²⁺CI2-aH₂O are subjected to température treatment to décomposé the solid FeCI₂-yH₂O to produce solid Fe₂O₃ and anhydrous HCl gas, to the exclusion of the solid M²⁺CI2-aH2O which is not decomposed but is fully dehydrated, to the extent that it was not fully dehydrated already, to M²⁺CI2 (i.e. a=0). The température treatment is therefore effected under conditions that favour the thermal décomposition of FeCI₂-yH₂O over that of M²⁺CI₂-aH₂O. The température treatment in the thermal décomposition stage 24 is performed at a température above 200°C, but not higher than 600°C, under oxidising conditions, i.e. in the presence of oxygen, e.g. being supplied by air.

The HCl gas produced in the thermal décomposition stage 24 is recovered and is recycled along recycle line 50 to the digestion stage 18, to be used as digestion reagent.

Thus, the process as described enables the achievement of a favourable water balance that, in turn, enables the production of concentrated substantially dry (anhydrous) HCl in gaseous form, for use upstream in the process. This is in contrast to existing processes that exploit HCl in métal recovery operations, which produce diluted HCl solutions, rarely at concentrations higher than 18% v/v.

In the absence of déhydration, the gaseous HCl produced from the thermal décomposition stage 24 would be moist/dilute (i.e. contain water vapour), which would not be effective to be exploited in the digestion stage 12 in the manner described above.

The solid Fe₂O₃ and solid M²⁺CI2-aH2O are transferred to the third séparation stage 26, along transfer line 62, in which the solid M²⁺CI2 (i.e. a=0) is dissolved in water to produce a M²⁺CI2 solution, and solid-liquid séparation is carried out to recover the M²⁺CI2 solution and solid Fe₂O₃.

The M²⁺CI₂ solution is transferred to the metals recovery stage 30 along transfer line 64, for recovery of the metals contained therein.

The Fe₂Oa is withdrawn, as a saleable product, along withdrawal line 72.

DISCUSSION

The applicant has surprisingly found that the chemically bound water comprised in hydrous ore materials may, possibly with the addition of a small amount of free water to wet the 10 hydrous ore material, in the quantifies described, be exploited to facilitate Processing of such ore materials with gaseous hydrochloric acid that may then be regenerated as described, thereby to recover, separately, iron and other métal values from the hydrous ore material.

Claims (10)

1. A method of treating a hydrous ore material that comprises iron (Fe), in metallic or compound form, and at least one other métal (M), in metallic or compound form, to recover the iron and the at least one other métal from the hydrous ore material separately of each other, in metallic or compound form, the method including in a digestion step, producing a solution of ferrous chloride (FeCI₂) and a divalent chloride of the at least one other métal (M²⁺CI2) (FeCI2-M²⁺CI2 solution) by contacting the hydrous ore material with a digestion reagent in the form of gaseous hydrochloric acid (HCl), and reducing any ferrie iron (Fe³⁺) in solution, présent as FeCI3, to ferrous iron (Fe²⁺), présent as FeCI2 in solution, using a reducing agent;

in a crystallisation step, crystallising a solid ferrous chloride hydrate (FeCI₂-xH₂O, wherein x>1) and a solid divalent chloride hydrate of the at least one other métal (M²⁺CI2-zH2O, wherein z>1) from the FeCI2-M²⁺CI2 solution;

in a déhydration step, subjecting the FeCI₂-xH₂O and the M²⁺CI2-zH2O to température treatment to produce a solid partially dehydrated ferrous chloride hydrate (FeCI2yH2O, wherein x>y>0) and at least one of a solid partially dehydrated divalent chloride hydrate and a solid divalent chloride of the at least one other métal (M²⁺CI2-aH₂O, wherein z>a^0);

in a thermal décomposition step, subjecting the FeCI₂-yH₂O and the M²⁺CI2-aH2O to température treatment and thus decomposing the FeCI2-yH2O to produce solid ferrie oxide (Fe2O3), anhydrous gaseous hydrochloric acid (HCl), and solid divalent chloride of the at least one other métal (M²⁺CI2, i.e. wherein a=0); and using the anhydrous gaseous hydrochloric acid thus produced as the digestion reagent in the digestion step.

2. The method according to çlaim 1, wherein contacting the hydrous ore material with the digestion reagent includes, or is preceded by, size réduction of the hydrous ore material, which size réduction is performed to increase the surface area of the hydrous ore material that is available to be contacted by the digestion reagent.

3. The method according to claim 2, wherein contacting the hydrous ore material with the digestion reagent is performed simultaneously with performing size réduction of the hydrous ore material.

4. The method according to any of daims 1 to 3, wherein the at least one other métal is selected from one or more of copper (Cu), nickel (Ni), and cobalt (Co), in a metallic or compound form.

5

5. The method according to any of daims 1 to 4, wherein the hydrous ore material is a lateritic ore material.

6. The method according to any of daims 1 to 5, wherein the crystallisation step is an evaporative crystallisation step.

7. The method according to any or daims 1 to 6, which includes, in a first séparation step performed after the digestion step, separating solids from the FeCI₂-M²⁺CI2 solution by means of solid-liquid séparation, thus recovering the FeCI2-M²⁺CI2 solution substantially free of solids.

8. The method according to any of daims 1 to 7, which includes, in a second séparation step, performed after the crystallisation step and before the déhydration step, recovering the solid FeCI₂-xH₂O and the solid M²⁺CI₂-zH₂O from the crystallisation step.

20

9. The method according to any of daims 1 to 8, wherein the déhydration step is performed under non-oxidising conditions at a température in a range of from 70°C to 150°C.

10. The method according to any of daims 1 to 9, wherein the thermal

25 décomposition step is performed under oxidising conditions at a température of from 200°C to 600°C.