WO2008080209A1

WO2008080209A1 - Process for recovery of nickel and cobalt from an ion-exchange resin eluate and product

Info

Publication number: WO2008080209A1
Application number: PCT/BR2008/000002
Authority: WO
Inventors: Flávia Dutra MENDES; Tiago Valentin Berni
Original assignee: Companhia Vale Do Rio Doce
Priority date: 2006-12-29
Filing date: 2008-01-02
Publication date: 2008-07-10
Also published as: BRPI0605892B1; PE20081248A1; BRPI0605892A

Abstract

The present invention relates to a process for obtaining nickel, cobalt, and other metals from ores containing them, as well as from the product obtained at any of its stages, as follows: (a) preparation or pre-treatment of the ore for its enrichment by means of silica rejection; (b) acid leaching of the pre-treated ore; (c) treatment of the effluent solution from the leaching stage using ion-exchange resin applied to the pulp; (d) elution or desorption of the ion-exchange resin using regenerated hydrochloric acid from the pyrohydrolysis stage (e) removal of copper and other impurities by precipitation, using either a sulfide or hydrosulfuric acid; (f) the solution still containing nickel and cobalt is subjected to a solvent extraction process; (g) stripping, using regenerated hydrochloric acid from the pyrohydrolysis stage (h) precipitation of cobalt in the form of either carbonate or any other intermediate product, such as sulfate, oxide, or hydroxide (i) Pyrohydrolysis of the nickel-containing solution, thus obtaining nickel in the form of oxide, and hydrochloric acid.

Description

PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT

The present invention relates to a process for obtaining nickel, cobalt, and other metals from such laterite ores as saprolitic or limonitic laterites, as well as from products of the processing of this ore type.

The choice of the technological route and of the final product to be produced by an industrial nickel processing plant is directly dependent on the characteristics of the ore to be fed to the plant. There is no conventional process. In the middle of the past decade, the high nickel and cobalt prices led the nickel industry to seek less onerous process alternatives that could reduce operational costs and hence maintain profitability while offering lower price levels for nickel and cobalt.

The development of technologies having lower investment cost - such as atmospheric leaching in tanks, atmospheric heap leaching, and resin- in-pulp (RIP) technology -, together with the decline in sulfur price, gave some companies the opportunity to consider the development of reserves and processing of low-grade laterite ores which were not used in traditional production processes. Historically, innovations in the nickel production process have resulted mainly from using the technology that was used initially in uranium processing and later in the gold industry. The resin-in-pulp (RIP) process is a good example.

Flexibility, high metal recovery, and low capital and operating costs, in addition to energy savings, translate into the logistics that may indicate the technological process comprising acid leaching followed by resin-in-pulp and nickel and cobalt recovery as the preferred process for developing laterite deposits in the medium and long terms. Many analysts believe that resin-in-pulp technology-based operating costs could be from 15% to 25% lower than current operating costs incurred by the major production groups in the market. Lower investments (capital cost/year) are also expected, owing to the simplicity of the flowsheet (shown in Figures 2 and 3) proposed herein. Various hydrometallurgical routes are currently used for extraction of nickel and cobalt contained in laterite ores. The objective of such routes is to solubilize the metallic species by using inorganic acids, followed by solid-liquid separation and neutralization, prior to final metal recovery. Selective recovery of the metal present in the leach pulp is an important stage in drawing up the economic evaluation. The presence of many impurities, including but not limited to copper, iron, manganese, and magnesium, may be regarded as the main technological difficulty to be overcome in nickel processing. This results in complex flowsheets with a great number of unit operations, high investment and operating costs, and technological risks such as early termination of operations, long time to ramp up, and difficulty to achieve the projected production scale.

From the described above, it is apparent that various factors, such as high nickel and cobalt prices, under-exploited laterite deposits, increasing demand for nickel metal, and low sulfur and H2SO4 prices, have encouraged the development of new flowsheets for processing nickel laterites. It is expected that the development of these new flowsheets will bring about a number of advantages: cost reduction, operational simplicity, greater recoveries, and recovery of cobalt as a byproduct.

The conventional flow on a basic flowsheet for an extraction process in an aqueous medium comprises the following stages: preparation; leaching; solid-liquid separation; solution treatment; and metal recovery for production of either the metal or the metallic compound.

With regard to leaching, the two most commonly used process options are pressure acid leaching, and reduction followed by atmospheric ammoniacal leaching (Caron process). It is noted that, even with industrially proven, highly economically intensive conventional technologies, such as pressure sulfuric acid leaching and the Caron process, there is and endless search for less onerous technologies, as is the case of atmospheric acid leaching. With regard to solution treatment, the conventional solvent extraction and precipitation technologies can be mentioned.

Solvent extraction applied directly to the leach effluent, as in the Bulong plant, has the advantage of high nickel and cobalt recoveries, but the presence of impurities in high concentrations and the need to control them still requires intense optimization of this technology. One of the main impurities is chromium (Cr3+ and Cr6+), whose behavior in the presence of Cyanex 272 - solvent used for nickel and cobalt separation in a sulfuric medium - is little known. Some parameters still conflict with one another, such as oxidation state of metals, pH, and presence of such anions as nitrate, chloride, sulfate, and acetate. Other challenges can be mentioned, such as Mn separation from Co, Ca separation from Ni, and effects of products from degradation by such extractants as Cyanex 272, Versatic Acid, hydroxy oximes, and D2EHPA. Much as a result of these still little-understood restraints, mainly the high concentration of impurities contained in this effluent, the Bulong industrial operation was interrupted by operational problems.

Precipitation techniques, such as production of mixed nickel and cobalt hydroxide and sulfide precipitates, are very dependent on the quality of the feed solution. In this case, correct and efficient operation of previous purification units is of fundamental importance to prevent contamination of the "mixed nickel and cobalt hydroxide" product - precipitated by the addition of magnesia - by such elements as iron, aluminum, and silica, as is the case of the Cawse plant. In the case of chromium, it shall be reduced so as to be effectively precipitated in the previous operations. The presence of silica causes low nickel recovery in subsequent ammonia leaching operations. Manganese precipitation is influenced by the residence time. The same strict control of impurities shall be performed in the case of production of mixed nickel and cobalt sulfide precipitates. The addition of H2S shall be made so as to obtain selective nickel and cobalt precipitation. This precipitate is then re-leached under oxidizing conditions, and such impurities as iron, copper, and zinc are removed, as is the case of Moa Bay and Murrin Murrin plants. Mixed Hydroxide Precipitate (MHP) and Mixed Sulfide Precipitate (MSP) technologies are industrially proven and have similar performances. The choice between one or the other will depend on environmental, safety, and infrastructure factors, income statements, and strategies in the production of a sulfide or hydroxide product for commercialization.

With regard to metal recovery, conventional technologies in hydrometallurgical flowsheets present the recovery of nickel and cobalt in metallic form through such operations as electrolysis and reduction with hydrogen. There is also the option to produce intermediate products, such as nickel and cobalt carbonates, hydroxides, and oxides.

Conventional hydrometallurgical flowsheets differ significantly from one another, exactly because there is not a standard, optimized flowsheet available that meets the chemical and mineralogical requirements of nickel laterite ores. The various flowsheet options have technical and economic restraints and limitations that shall be minimized, or even eliminated, by optimizing the unit operations involved. Figure 2 shows a basic flowsheet for an extraction process in an aqueous medium.

One example is the solid-liquid separation stage, which causes great problems in conventional circuits. Owing to the poor sedimentation characteristics of the pulp in Counter-Current Decantation (CCD), approximately 10% soluble nickel and cobalt is lost in the waste. In order to minimize this significant loss, a series of at least six large thickeners, with each stage being more than 50 meters in diameter, is used in solid-liquid separation, so as to achieve the right solid sedimentation and produce a limpid overflow. In this way, the capital cost of a simple CCD stage with conventional thickeners may amount to 30% of the capital cost of a titanium autoclave used in High Pressure Acid Leaching (HPAL). If chlorides are present, as in the case of some laterite deposits in arid regions, even more expensive thickeners are required. In addition to capital costs, operating costs are also high, since they include not only energy consumption for each rake, but also flocculants required for the settling of fine material. Flocculant consumption varies from 200 to 800 grams per ton of solids, which increases the total operating cost of the plant by up to 10%.

One other difficulty to be overcome is in nickel and cobalt recovery from the resulting solution, or Pregnant Leach Solution (PLS), owing to the impurities present and low concentration of the target metals. Ion-exchange is an efficient method for overcoming such obstacles, since it is effective at low concentrations, and selectivity can be significantly enhanced by choosing the most suitable ion-exchange resin.

Many factors encourage not only the optimization of preexisting flowsheets, but also the proposal of new process flowsheets of highly innovative nature. For most companies and at most times, the basic focus is on the improvement of existing operations as a way of overcoming obstacles. Substantial gains are sometimes achieved by implementing new technologies in parts of the plant, rather than completely changing the whole operation. In this way, it is possible to gain proper understanding of the process basics, mainly by improving equipment, design, operational procedures, reagents, and mathematical modeling.

One of the main factors leading to proposing new flowsheets is the high nickel price resulting from the slow growth of primary nickel production and the massive increase in Chinese consumption, which encourage an intense race to develop new proposals for hydrometallurgical processes. Until then, many projects had failed to become economically feasible on the basis of projected long-term nickel prices. Existing acid leaching operations for laterite ore treatment have failed to reach the projected production levels, which even led to plant closures, as was the case of Bulong in 2003. This fact caused a huge impact on nickel offer, as well as on investment in the rest of the nickel industry. Owing to the ever-growing complexity of the deposits in chemical and mineralogical terms as well as in size, many companies aspire to find a large, high-grade deposit that can be easily mined and processed. Conventional technologies can be used with lower technical risk, mainly based on the experience from recent metallurgical operations. There is a perception that implementation of new technologies is challenging, which often leads to choosing what is conventional. Excessive reliance on the latter, however, often causes a number of even more encompassing problems which are common, such as inadequate, or lack of, pilot operation, start-up delays due to operational problems, lack of qualified employees, flaws in the project engineering and cost projection, problems due to operational complexity, low operational efficiency, operational simplifications to save costs and time within demanding timeframes, inadequate resources, and market underestimating. New technologies, on the other hand, pay off, but often after a long time spent in research and development until a state of excellence is achieved.

In order to achieve the objectives described above, a process was developed for obtaining nickel, cobalt, copper, and other metals from ores containing them, comprising the following stages:

(a) preparation or pre-treatment of the ore for its enrichment by means of silica rejection;

(b) acid leaching of the pre-treated ore;

(c) treatment of the effluent pulp from the leaching stage using ion-exchange resin;

(d) elution or desorption of the ion-exchange resin using regenerated hydrochloric acid from the pyrohydrolysis stage;

(e) removal of copper and other impurities by precipitation, using sulfide or hydrogensulfide;

(f) the solution still containing nickel is subjected to a solvent extraction process; (g) cobalt stripping and precipitation using regenerated hydrochloric acid from the pyrohydrolysis stage;

(h) pyrohydrolysis of the nickel-containing solution, thereby obtaining nickel in oxide form, and hydrochloric acid;

Knowing the limitations of conventional flowsheets and the expectation on the high potential of use of emerging technologies currently being developed, the solution proposed herein is for innovating flowsheets from the hydrometallurgical viewpoint, so as to obtain greater operational simplicity, higher process efficiencies, and lower investment and operating costs.

With regard to leaching of limonitic and saprolitic ores, the proposal is for the use of atmospheric acid leaching - be it sulfuric or hydrochloric -, high-pressure acid leaching, and combined atmospheric and high-pressure acid leaching.

With regard to treatment of the effluent solution, the proposal herein is for the use of ion-exchange resin, preferably the use of resin-in-pulp, with the particularity that elution or desorption shall be performed with hydrochloric acid. The nickel- and cobalt-containing product (eluate) from this stage also contains such impurities as copper, and shall be purified. The proposal is for the addition of either H2S or NaHS in low concentrations, for the precipitation of metallic sulfides - chiefly copper sulfide and small proportions of other metallic sulfides. A second option for copper removal is the use of fixed-bed resins for selective adsorption of copper and other impurities. The solution still containing nickel and cobalt is conveyed to a solvent extraction stage with Alamine 308, for separation of these metals. Efficiency shall be significantly increased as a result of the high purity of the feed solution, which was purified in a previous resin-in-pulp stage. It is known that the use of solvent extraction directly applied to the leach effluent involves a number of risks, mainly because the extractants currently available are not sufficiently selective to separate nickel from impurities. Obtaining a higher-purity intermediate product (eluate) is a reasonable way to overcome this non-selectivity of current commercial extractants. After being separated in the previous stage, nickel and cobalt follow distinct, independent flows for being recovered.

With regard to metal recovery, cobalt shall be recovered in either hydroxide or carbonate form, and nickel shall be recovered in oxide form by the pyrohydrolysis process with HCI regeneration.

The flowsheet of the invention, shown in Figure 3, offers a number of advantages as follows:

Ore leaching shall preferably be acid, with either sulfuric acid or hydrochloric acid being used. High-pressure sulfuric leaching has the advantage of being a conventional technology widely established in various industrial applications. Acid leaching technologies under atmospheric pressure and at temperatures around 105⁰C, below the pulp boiling point, deserve highlighting. This option has the disadvantages of lower nickel recovery efficiency and greater operating cost due to higher acid consumption. Lower investment cost, however, renders it a highly attractive technical alternative. Another option with high potential success involves the combination of atmospheric and high- pressure leaching types, which can provide big savings in process acid consumption.

Some of the various advantages of the resin-in-pulp process discussed above deserve highlighting, namely, elimination of the onerous solid- liquid separation stage, flowsheet simplification, elimination of a number of unit operations, potential reduction of investment and operating costs, and high recovery and separation efficiencies for the target metals (nickel and cobalt). In this stage, resin elution - i.e. desorption of the metals on the resin - shall necessarily be made with hydrochloric acid, since all the other operations at the flowsheet back-end are dependent on this condition. The hydrochloric acid used in this stage is the regenerated hydrochloric acid from the final stage (pyrohydrolysis) of the flowsheet. The solvent extraction stage at this point on the flowsheet has a huge potential success and minimal technical risk. A previous stage is suggested for removal of copper by precipitation as copper sulfides. Contrary to the other direct applications of solvent extraction on leach effluents on various process flowsheets for nickel ores, in the present invention the feed to this stage is regarded as a high-purity solution, since it comes from a previous high- efficiency ion-exchange stage. The low level of impurities and high concentrations of the target metals (nickel and cobalt) favor the high performance of this technique. The extractant used is Alamine 308, which is a reagent specific for nickel and cobalt separation in hydrochloric medium, as is the case. The stripping stage - i.e. re-extraction of cobalt from the organic extractant - shall likewise be made with hydrochloric acid from the pyrohydrolysis stage where the acid is regenerated. The use of regenerated hydrochloric acid in the resin elution and stripping stages of the flowsheet proposed herein provides savings in acid consumption, and consequently, reduction of operating costs.

Pyrohydrolysis could be regarded as a crucial stage in the proposed flowsheet. It is exactly in this stage that the final nickel product in nickel oxide form is obtained, and the hydrochloric acid used in the process is regenerated so as to be reused in the ion-exchange and solvent extraction stages. The option presented by this flowsheet is the generation of nickel and cobalt intermediate products, thereby avoiding the increase in capital costs that would result from the insertion of such stages as electrolysis and reduction with hydrogen.

Briefly stated, the invention achieved the following objectives:

(1 ) lower environmental impact - lower water consumption, as well as opportunity for water recycling

(2) lower capital and operating costs

(3) larger amount of metallic products - high selectivity to target metals, high separation capacity, and high-efficiency metal recovery; (4) operational simplicity, with elimination of unit operations;

(5) lower technical risk, as a result of optimization of unit operations with regard to operational conditions, reagents, and feed solution purity;

Stated in detail, the invention contemplates:

Pre-treatment: the objective of this stage is ore enrichment by means of silica rejection. Operations include both primary and secondary crushing, scrubbing for release of fine particles, classification for rejection of coarse, low-grade siliceous material, and attrition to maximize recovery of the nickel contained in fine particles.

Figure 1 illustrates the enrichment potential of the nickel content, with the cut-off size in the classification stage.

Leaching: The exploitation of nickel laterite reserves has been increasing over the years as exploitable reserves of sulfide ores become exhausted. Therefore, new processes are being developed for extraction of nickel and cobalt from these weathered ores. Each process involves dissolution of target metals with an acid, followed by a solid-liquid separation stage and a purification stage prior to the recovery stage. Of these processes, Pressure Acid Leaching (PAL) has become the most used option for treating laterites. It is performed in pressurized vessels or autoclaves made of carbon steel and lined with an 8-mm layer of grade 17 titanium. The percentage of solids is approximately between 30% and 34%, and residence time is between 60 and 120 minutes, at a temperature of between 25O⁰C and 27O⁰C. Acid consumption is dependent on the presence of acid-consuming elements, but can be minimized by acid regeneration by hydrolysis that occurs in these conditions. Another new form of leaching is performed under atmospheric pressure and at pulp temperature below the boiling point. Under such conditions, it is possible to use acid leaching with such reagents as hydrochloric acid and sulfuric acid, in rubber- lined carbon steel tanks. Under these conditions, residence time is significantly greater, of up to 24 hours, and the percentage of solids is around 33%. Under these conditions, it is possible to treat ores of either limonitic or saprolitic type having the most varying chemical and mineralogical compositions. Acid consumption tends to be greater under such conditions, but is offset by lower investment cost. The combination of these two types of leaching is likewise attractive, due to their lower acid consumption.

Resin-in-pulp: The ion-exchange resin technique is regarded as an emerging option without large-scale application, among the options for treatment of solutions on nickel process flowsheets. Studies are being intensified, with various very promising approaches and results. This technique was initially developed for gold, and evolved from the carbon-in-pulp (CIP) process, with activated carbon being replaced with ion-exchange resin. The first commercial plant to utilize RIP for gold recovery was Gold Jubilee Mine, in South Africa (Fleming, C.A., 1988). The industrial operation at this mine served as the basis for assessing the advantages of RIP over CIP (Fleming, C.A., 1988). Recently, the development of this technique for nickel has been greatly stimulated by the fact that, because of its operational simplicity, smaller number of equipment units, and lower costs involved, it can compete with such conventional technologies as solvent extraction and precipitation-releaching. The main advantages are as follows: efficient recovery and selective removal of low concentrations of some metallic ions over an excess of other metals; high metal loads; high mechanical strength, which reduces losses by attrition; rapid elution; and low losses from contamination by organic matter. Industrial plants that utilize acid leaching for laterite ores include a multi-stage counter-current decantation circuit for solid- liquid separation, which involves high capital and operating costs, occupies a large area, and requires a significant amount of washing water. Capitalizing on the great advantages of the ion-exchange technology, the use of a resin-in-pulp system is one alternative for nickel and cobalt recovery from the leach pulp without the use of thickeners. Usually, between the leaching and resin-in-pulp stages, there is a neutralization stage, the objective of which is to neutralize the acid excess in the leach effluent, as well as precipitate iron and some impurities. The temperature in this stage may be within the range 70-95 ⁰C, and limestone addition and air injection are provided to oxidize the iron. The pH in this stage is within the range from 4 to 5.

The resin-in-pulp operation comprises three distinct stages: 1 ) Adsorption: Nickel and cobalt are selectively recovered in this stage, which can be performed in either air-agitated pachuca tanks or mechanically agitated tanks. The resins suggested for this type of application are those containing an iminodiacetic acid or picolylamine functional group. Contact between resin and pulp is made in counter-current flow, with intermediate screens between tanks for phase separation. The loaded resin from the first tank is retrieved from the circuit, washed for removal of aggregated solids, and transferred to the elution circuit. 2) Elution: Elution shall be performed with regenerated hydrochloric acid from the pyrohydrolysis stage, in a concentration of between approximately 50g/L and 150 g/L. 3) Regeneration: The eluted resin is then put into contact with a reagent, such as soda or limestone, so as to be regenerated and returned to its calcium or sodium form.

Solvent extraction: Various extractants, such as carboxylic acids (Versatic 10) and phosphoric acid derivatives (D2EHPA), can be used for nickel recovery in a sulfate medium. There are also phosphinic acid-based selective extractants for cobalt (Cyanex 301 and Cyanex 272). These extractants do not have high selectivity for nickel, when compared with other elements such as manganese, iron, cobalt, magnesium, and calcium. These reactants require strict pH control and multiple-stage washing to improve their selectivity for nickel. The development of nickel-selective extractants has always been challenging, since nickel electrolysis is very sensitive to pH, and there is an optimum pH window ranging from 3.5 to 4.0, which is significantly higher than the typical pH values of leach effluent solutions. Therefore, an extractant to be used for nickel recovery from effluent solutions with pH between 1 and 2 shall be regenerated to pH=4. To increase solvent extraction efficiency, a stage is proposed herein for copper removal either by precipitation of the metal in copper sulfide form, or by its recovery using fixed-bed ion-exchange resin.

In the case of the flowsheet proposed herein, hydrochloric acid is the solvent medium, and the metallic species are in the form of chlorides. In this case, the only organic extractant available in this case is Alamine 308 (tri-iso- octylamine), which has a high selectivity for cobalt over other metals. The extraction process comprises three stages: extraction, washing, and stripping. Cobalt stripping from the organic extractant shall be made with hydrochloric acid regenerated in the pyrohydrolysis stage. The final cobalt product shall be obtained in precipitate form, with the addition of soda and consequent formation of cobalt carbonate.

D Alamine 308 (tri-iso-octylamine)

This tertiary amine is used as ion-exchange extractant for extracting CoCI42- from solutions leached by hydrochloric acid. Nickel does not form chloro complexes and is not extracted, whereas copper and zinc are, with the latter being extracted in lower chlorine concentrations that cobalt.

As it contains a basic nitrogen atom, it reacts easily with a variety of organic and inorganic acids, forming amine salts which are capable of undergoing ion exchange reactions, as shown by the equations below.

Protonation

[R3N]org + [HA]aq*→[R3NH+A-]org

Ion exchange

[R3NH+A-]org + [B-]aq <→ [R3NH+B-]org + [A-]aq

The ion-exchange efficiency between A and B anions depends on the relative affinity of both with the organic cation and their respective solvatation energies. The regeneration stage of the target species can be performed by a wide range of inorganic salt solutions, such as NaCI, Na2CO3, and (NH4)2SO4 solutions. The reagent for the stripping stage depends on the total process recovery, but generally, basic reagents for the reverse reaction (deprotonation) give better results in a smaller number of steps. The equation below gives the recovery by Na2CO3.

2[R3NH+B-]org + [2Na+ + CO32-]aq <→ 2[R3N]org + H2O + CO2 + 2Na+aq + 2B-aq

In some cases, formation of anionic complexes and their subsequent extraction will depend on the concentration of this anion, an example being the extraction of cobalt as a chloro complex.

Pyrohydrolysis: conventional fluidized-bed pyrohydrolysis provides hydrochloric acid regeneration. The use of this process has two major advantages, the first being that hydrochloric acid regeneration is an environmental necessity. In many hydrometallurgical processes, it is absolutely essential to recover the leaching agent (HCI, CI2, FeCI3), since its disposal together with the metals contained therein is economically and ecologically unacceptable. The second advantage is the savings from acid regeneration, as the operating cost with reagents is minimized. High-purity recovery of more than 99% is commonly achieved, which is important for the case of HCI intended for sale. Spent hydrochloric acid is regenerated during pyrohydrolysis, and reused in resin elution and organic solvent re-extraction.

In some hydrometallurgical processes, the metal oxide is the desired product, and regenerated HCI is the byproduct. In some cases, a concentrated NiCI2 solution can also be produced. Such solution can be processed either by pyrohydrolysis, generating NiO and HCI, or by electrolysis, generating metallic nickel and chlorine gas. For obtaining the metal from NiO, the oxide shall be reduced with H2, at 75O⁰C.

Electrolysis has the advantage that metallic nickel is produced in a single stage. However, there are some drawbacks: the chlorine required to produce HCI for leaching is generated in small amounts at thousands of anodes, which shall be carefully collected and treated; and the high cost of generation of electric energy, whose efficiency is of only 35%.

Pyrohydrolysis also produces nickel oxide in a single stage, but simultaneously produces HCI in off-gas form, which is absorbed into water. Primary fuels such as gas or oil may be used. Metal reduction can be performed in a separate furnace, with stoichiometric addition of H2. In such case, nickel oxide in granular form is preferred, since the fine form may agglomerate in the reduction furnace. Nickel pyrohydrolysis occurs at relatively high temperatures, above 1000K (727⁰C). Thermodynamic data show that, if the temperature of the off-gas system decreases to 700⁰C, then the reverse NiO reaction occurs, generating NiCI2. The exact temperature will depend on the HCI/H2O ratio in the off-gas. At high HCI partial pressure, the reverse reaction for NiCI2 formation occurs at temperatures above 700⁰C.

The only experimental nickel chloride pyrohydrolysis operation occurred at Falcon Bridge Matte Leach Plant from 1968 to 1984. In this process, high temperatures are required for the reaction to occur, as well as for preventing the reverse reaction (NiCI2 formation). On the other hand, NiCI2 sublimates at 95O⁰C, when its vapor pressure reaches 1 atm.

The following examples serve to better illustrate the scope of the invention described herein, and should not be taken as limiting the invention.

Examples:

SAMPLE #1 (SJP-FM08 46.95 to 49.25m)

The grain-size fraction (-32/+200) of nickel laterite ore sample #1 contained 0.5% Ni, 0.02% Co, 44.23% Fe, and 0.28% Mg. Said fraction, together with a 96% sulfuric acid solution, was the feed to Atmospheric Leaching (AL) at a temperature of 950C, with 385 rpm agitation and 33% solids, for 6 hours. In AL, extraction of 73.3% Ni and 59.0% Fe was achieved, generating an effluent with concentrations of 2.9 g/L Ni, 229.1 g/L Fe and 138.1 g/L residual free acidity, and a residue containing 0.23% Ni and 31.20% Fe. A portion of this liquor, together with a 96% sulfuric acid solution and another fraction (-200) of sample #1 containing 0.62% Ni₁ 0.03% Co, 43.10% Fe and 0.31 Mg, was the feed to an autoclave wherein High-Pressure Acid Leaching (HPAL) was performed at a temperature of 2500C, with 500 rpm agitation, at 600 psi, and with 30% solids, for 75 minutes. On feeding the HPAL, the liquor was diluted, after which it presented concentrations of 0.02 g/L Ni and 1.37 g/L Fe. After HPAL, the effluent from the autoclave contained 4.7 g/L Ni and 56.6 g/L Fe, indicating that 41.0% Fe from the AL liquor had been precipitated, and the residue contained 0.02% Ni and 44.1% Fe. The ferric sulfate hydrolysis reaction caused precipitation of Fe in hematite form, and acid regeneration of approximately 128.5 kg/t, which corresponds to 30% of gross consumption. Other 93.9 kg/t (22% of overall consumption) were recovered from the residual free acidity present in the AL effluent, so that an addition of only 48% (206.6 kg/t) of acid was necessary. The Ni extraction (AL followed by HPAL) value was 96.7%, and it can be highlighted that in HPAL an extraction of 94.3% Ni was achieved for a gross acid consumption of 429.0 kg/t.

Table 1 - Sample com osition and AL roduct data

TABLE 1

Table 2: Sample composition and HPAL product data

TABLE 2

Table 3: Comparison between results from HPAL and from AL followed by HPAL

TABLE 3

SAMPLE #2 (SJP-FM09 27.00 to 28.00m)

The feed to AL was the fraction (-32/+200) containing 1.11% Ni, 0.21% Co, 37.76% Fe and 0.79% Mg, and a 96% sulfuric acid solution. The operational variables used were temperature 950C, 385 rpm agitation, and 33% solids for 6 hours. Atmospheric Leaching produced a liquor with concentrations of 7.0 g/L Ni, 107.6 g/L Fe, and 39.5 g/L residual free acidity. The residue contained 0.34% Ni and 32.90% Fe, and extraction values were 76.5% Ni and 33.3% Fe. The subsequent stage (HPAL) was fed with a portion of this liquor, a 96% sulfuric acid solution, and an amount of ore corresponding to the fraction passing #200 mesh (1.49% Ni, 0.13% Co, 26.30% Fe and 1.07% Mg). Addition of the solution to the liquor caused dilution, after which the feed presented concentrations of 0.04 g/L Ni and 0.58 g/L Fe. HPAL was performed at 2500C and 650 psi, with 500 rpm agitation and 30% solids, for 75 minutes. The resulting liquor contained 8.8 g/L Ni and 12.5% Fe, and the residue contained 0.15% Ni and 30.60% Fe. It can be noted that the HPAL liquor contained less Fe than the AL effluent, such reduction corresponding to 61.1% Fe that was precipitated. Sulfuric acid regeneration of 108.3 kg/t, which occurred in the autoclave, corresponded to 30% of the gross consumption. For this reason, the amount of acid added into the autoclave corresponded to 63%, that is, 226.0 kg/t were fed and 26.6 kg/t from AL (corresponding to 7% of the gross consumption) were used. Ni extraction values were 94.1% for a single HPAL stage, and 91.0% for AL followed by HPAL. Table 4: Sam le com osition and AL roduct data

TABLE 5

Table 6: Comparison between results from HPAL and from AL followed by HPAL

TABLE 6

SAMPLE #3 (SJP-FM09 51.45 to 53.00m) The composition of the fraction (-32/+200) used as feed to AL was 0.71% Ni, 0.06% Co, 13.89% Fe and 1.67% Mg. Said fraction was added to a 96% sulfuric acid solution and leached at 950C, with 385 rpm agitation and 33% solids, for 6 hours. The effluent from AL presented extraction values of 75.6% Ni and 53.0% Fe, with concentrations of 3.3 g/L Ni, 45.0 g/L Fe and 110.9 g/L free acidity. The residue contained 0.20% Ni and 7.54% Fe. A portion of this liquor, together with a 96% sulfuric acid solution and the fine fraction (-200) of this sample, was used to feed the autoclave for HPAL. The fine fraction composition was 4.53% Ni, 0.11% Co, 27.80% Fe and 3.31% Mg. After dilution caused by the sulfuric acid solution, the concentration values for the liquor that fed the HPAL were 0.02 g/L Ni and 0.30 g/L Fe. The operational parameters used for HPAL were as follows: temperature 2500C; 500 rpm agitation; pressure 650 psi; and 30% solids, for 75 minutes. The HPAL liquor contained 24.1 g/L Ni and 5.6 g/L Fe, and the residue contained 0.20% Ni and 34.60% Fe. During HPAL, there was sulfuric acid regeneration of 40% (174.4 kg/t), and 76.1 kg/t (17%) from free acidity were used, so that only 42% new acid, corresponding to 185.4 kg/t, had to be added. This HPAL liquor presented an extraction value of 96.2% Ni, which is 2% higher than HPAL not preceded by AL. It was also noted that 61.1% Fe was precipitated.

Table 7: Sam le com osition and AL roduct data

TABLE 7

Table 8: Sample composition and HPAL product data

High Pressure Acid Leachin - HPAL

TABLE 8

Table 9: Comparison between results from HPAL and from AL followed b HPAL.

TABLE 9

Claims

1. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", characterized by comprising the following stages:

(a) preparation or pre-treatment of the ore, for its enrichment by means of silica rejection;

(b) acid leaching of the pre-treated ore;

(c) treatment of the effluent solution from the leaching stage using ion-exchange resin applied to the pulp;

(e) removal of copper and other impurities by precipitation, using either a sulfide or hydrosulfuric acid;

(f) the solution still containing nickel and cobalt is subjected to a solvent extraction process;

(g) stripping, using regenerated hydrochloric acid from the pyrohydrolysis stage;

(h) precipitation of cobalt in the form of either carbonate or any other intermediate product, such as sulfate, oxide, or hydroxide;

(i) Pyrohydrolysis of the nickel-containing solution, thereby obtaining nickel in the form of nickel oxide, and hydrochloric acid.

2. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that ore pre-treatment includes crushing (both primary and secondary), scrubbing for release of fine particles, classification for removal of coarse, low-grade siliceous material, and attrition to maximize nickel recovery.

3. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that leaching occurs in the presence of either sulfuric acid or hydrochloric acid.

4. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that the ore can be subjected to pressure and/or atmospheric leaching, or combinations of these.

5. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that, optionally, the leach effluent can be subjected to neutralization prior to ion-exchange resin treatment.

6. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that ion-exchange resin in pulp is used.

7. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 or 6, characterized by the fact that, in the ion-exchange resin stage, elution or desorption occurs in the presence of regenerated hydrochloric acid from the pyrohydrolysis stage.

8. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that resins containing an iminodiacetic acid or picolylamine functional group can be used.

9. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that the hydrochloric acid concentration in the elution stage may vary between approximately 50 g/L and approximately 150 g/L.

10. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that a fixed-bed resin system is used for selective absorption of copper and impurities.

11. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that either sodium acid sulfide or hydrosulfuric acid is used for removal of copper and impurities.

12. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that the selective extractant for cobalt removal in the solvent extraction stage can be a tertiary amine in hydrochloric medium.

13. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1, characterized by the fact that cobalt removal can be performed in three stages: extraction, washing, and stripping.

14. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that cobalt is recovered in the form of cobalt hydroxide, oxide, sulfate, or carbonate.

15. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that the cobalt-selective re- extractant can be regenerated hydrochloric acid from the pyrohydrolysis stage.

16. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 15, characterized by the fact that the cobalt-selective extractants can be phosphinic acid-based.

17. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that the nickel-selective extractants in sulfate medium can be carboxylic acids and/or phosphoric-acid derivatives.

18. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1, characterized by the fact that cobalt is recovered in precipitate form, with addition of soda and consequent formation of cobalt carbonate.

19. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that pyrohydrolysis can occur on fluidized bed.

20. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that pyrohydrolysis regenerates hydrochloric acid, which is used in resin elution and organic solvent re-extraction;

21. "PROCESS FOR RECOVERY OF NICKEL AND COBALT FROM AN ION-EXCHANGE RESIN ELUATE AND PRODUCT", according to claim 1 , characterized by the fact that the obtained nickel oxide is in granular form.

22. "PRODUCT", characterized by the fact of being obtained from any of the stages described in claims 1 to 21.