WO2008101414A1 - A process for extracting metals from laterite - Google Patents

Abstract

A process for extracting metals from laterite containing Ni and Co comprises (1) mixing laterite with a sulphur-containing material selected from elemental sulphur and metallic sulphide, calcining the obtained mixture in an oxidizing atmosphere so as to convert the non-ferrous metals in the mixture into sulphates thereof and convert iron into oxide; (2) leaching the calcined materials with water so as to extract Ni and Co in the materials into the leaching liquor. A process for calcining laterite containing Ni and Co comprises mixing laterite with a sulphur-containing material selected from elemental sulphur and metallic sulphide, and calcining the obtained mixture in an oxidizing atmosphere.

Description

 Method for extracting metal from laterite ore

 The present invention generally relates to a method of extracting metals from ore. More specifically, the present invention relates to a method of extracting nickel, cobalt and other metals from laterites.

 Background of the invention

 Laterite ore is a mixture of hydrated iron oxide and hydrated magnesium silicate formed by long-term large-scale weathering leaching and alteration of basic rocks such as olivine or serpentine. It is a loose clay-like nickel oxide containing a large amount of water. Mineral resources, easy to mine, difficult to process. At present, the available parts of laterite ore are generally divided into three layers: the limonite layer, the saprolite layer and the transition layer between the two. The chemical composition of laterite ore varies not only from mineral deposit, but even the same deposit, its content of nickel, cobalt, iron, magnesium, etc. varies with the depth of the deposit, which increases the difficulty and cost of processing the laterite ore.

According to its chemical composition, laterite ore can be treated by pyrometallurgical or hydrometallurgical methods. The key link of laterite hydrometallurgy is leaching, which not only requires the full dissolution of valuable metals such as nickel and cobalt, but also avoids impurities, especially iron, and enters the solution in large quantities. The hydrometallurgical methods currently used in the industry to treat laterite ore are only the Caron method (reduction roasting-ammonia leaching method) and the HPAL method (high-pressure acid leaching method), which both better control the iron in the leaching of nickel and cobalt. Dissolved. The Caron method combines pyrometallurgy with hydrometallurgy to first calcine the ore in a reducing atmosphere to selectively reduce nickel in the ore to metallic nickel and iron to Fe ₃ 0 ₄ as much as possible. The baking is leached by ammonia medium. , to avoid the entry of iron and magnesium into the solution. However, the nickel and cobalt in the Caron leaching solution are greatly lost due to the adsorption of the leaching residue, and the metal recovery rate is not high. Generally, the nickel recovery rate is only 70% - 80%, and the cobalt recovery rate is even below 40%. Moreover, the Caron method needs to dry the ore before calcination. Since the laterite ore usually contains 30% - 50% of adsorbed water, the drying operation can be high. Therefore, although the Caron method is the earliest industrial application of the laterite hydrometallurgical method, it is now losing its competitiveness.

Sulfuric acid can effectively leaching nickel and cobalt directly from laterite ore, avoiding high-energy drying and reduction roasting operations, and the sulfuric acid is cheaper, but direct leaching with sulfuric acid under normal pressure Without selectivity, the iron in the ore is also almost all 3⁄4 V solution. In order to improve the selectivity of leaching, the dissolution of iron is controlled, and the high pressure acid leaching method is at 250. C - 270. The temperature of C (the vapor pressure is about 50 atmospheres) leaches the laterite ore with dilute sulfuric acid, and uses the hydrolysis reaction of iron at high temperature to precipitate iron into hematite and release sulfuric acid, which solves the problem of iron removal in solution and also reduces Acid consumption. The high-pressure acid leaching method was once the preferred technology for the treatment of laterite ore. However, the high investment and high energy consumption of the method requires that the material of the reactor can withstand corrosion, pressure and sealing at high temperatures, and the manufacturing process and operation technology requirements. High, expensive; leaching requires steam to heat all the pulp to above 270 °C, the process energy consumption is high; especially the reactor crust phenomenon is prominent, need to stop the cleaning frequently, seriously affecting the efficiency of high-pressure acid leaching, improve the operation cost. Therefore, the laterite mine project using this technology is difficult to achieve the expected effect, and even can not operate normally.

Sulfation roasting or selective oxidative roasting is an effective method for pretreating refractory ore in hydrometallurgy by controlling the temperature of roasting ore in an oxidizing atmosphere to bury copper, cobalt and nickel in the ore. The non-ferrous metal compound is converted into a water-soluble sulfate, and the iron is converted into iron-insoluble iron oxide, so that it is easy to dissolve the nickel, cobalt, copper and the like sulfate by water in the subsequent leaching operation. To the leachate, iron remains in the leach residue. This method has been successfully used to treat sulfide ore, but oxidized ore cannot be directly subjected to sulphation roasting due to the lack of sulfur in its composition. There are also attempts in the literature to introduce sulphation roasting into treated laterite ore. For example, N. Zubryckyj et al. (N. Zubryckyj, DJI Evans and VN Mackiw, Preferential sulphation of nickel and cobalt in lateritic ores, Journal of Metals, 17(5): 478-486 (1965)) and Υ·V. Swamy Etc. (Υ·V. Swamy, BB Kar and JK Mohanty, Physico-chemical characterization and sulphatization roasting of low-grade nickeliferous laterites, Hydrometallurgy 69: 89-98 (2003)) has been reported to mix laterite ore with concentrated sulfuric acid. Sulfation roasting. JH Canterford (JH Canterford, The sulphation of oxidized nickel ores, Paper presented at the International Laterite Symposium, New Orleans, Louisiana, Feb. 19 - 21, 1979) reported the mixing of laterite ore with acid and a sulfur dioxide-air mixture Sulfation roasting of laterite ore. The sulphuric acid roasting or the sulphur dioxide-air roasting laterite ore can achieve sulphation roasting, achieving the purpose of selectively leaching nickel, cobalt and controlling iron dissolution. However, both methods require external fueling to heat the entire material, typically to 600. Above C, energy consumption is high, which is in energy shortage. The period of rising fuel prices is particularly undesirable. Moreover, the sulfuric acid needs to be supplied with sulfuric acid on-site or self-built sulfuric acid plant. The use of sulfur dioxide needs to be close to the sulfide ore fire smelter produced by sulfur dioxide flue gas, which is inconvenient to operate and difficult to implement. At the same time, both roasting methods require a flue gas collection and absorption device to treat the sulfur oxides emitted from the flue gas of the roaster.

 Summary of the invention

 The present invention provides a method for extracting metals from a laterite ore containing nickel and cobalt, comprising:

(1) mixing laterite ore with a sulfur-containing substance selected from the group consisting of elemental sulfur and metal sulfide, and the resulting mixture is calcined in an oxidizing atmosphere to convert non-ferrous metals therein into respective sulfates, and iron is converted into Oxide

 (2) The above calcined material is leached with water, and nickel and cobalt are extracted into the leachate.

 The invention further relates to a method of calcining a laterite ore containing nickel and cobalt comprising mixing a laterite ore with a sulfur-containing material selected from the group consisting of elemental sulfur and a metal sulfide, and the resulting mixture is calcined in an oxidizing atmosphere.

 detailed description

 In the method for extracting a metal from a nickel or cobalt-containing laterite ore according to the present invention, the laterite ore is first mixed with a sulfur-containing substance selected from the group consisting of elemental sulfur and a metal sulfide, and the resulting mixture is calcined in an oxidizing atmosphere to obtain a result. The metal in the calcine is converted to the respective sulfate and the iron is converted to an oxide.

 In a preferred embodiment of the invention, the laterite ore may be limonite, sulphate or a mixture of the two.

 In a preferred embodiment of the invention, the sulfur-containing material selected from the group consisting of elemental sulfur and metal sulfide is selected from the group consisting of sulfur and ores, concentrates or the like containing nickel, cobalt or other iron and non-ferrous metal sulfide minerals. Materials such as nickel, cobalt sulfide precipitated from ore processing, antimony, etc. Sulfide minerals containing nickel, cobalt or other metals such as chalcopyrite, chalcopyrite, copper blue, pyrrhotite, cobalt pyrite, pentlandite, pyrite and sphalerite. The elemental sulfur and the metal sulfide may be used in combination or may be used singly.

In a particularly preferred embodiment, the mixture of laterite ore and a sulfur-containing substance selected from the group consisting of elemental sulfur and metal sulfide is further added with a substance selected from the group consisting of alkali metal and alkaline earth metal sulfates, in particular sodium sulfate and One of magnesium sulfate, especially sodium sulfate. In a preferred embodiment of the invention, the laterite ore is further added with sulfuric acid in a mixture of sulfur-containing materials selected from the group consisting of elemental sulfur and metal sulfides.

 In a preferred embodiment of the invention, the total amount of sulfur contained in the sulfur-containing material selected from the group consisting of elemental sulfur and metal sulfide is the dry basis of all the to-be-calcined mixture (including laterite ore, selected from elemental sulfur and metal sulfide). 5 to 35 wt%, preferably less than 30 wt%, particularly preferably between 10 and 20 wt%, of the sulfur-containing material of the substance, and possibly the alkali metal and alkaline earth metal sulfates and sulfuric acid, etc. . The specific percent by weight of the total sulfur is determined by the amount of acid-consuming materials such as magnesium and non-ferrous metals in the material to be calcined, and the skilled artisan will readily determine the total amount of sulfur added, inspired by the present disclosure. In a preferred embodiment of the invention, the calcination temperature is from 400 Torr to 850, preferably from 450 to 750*, especially from 600 C to 700* Torr.

 In the process of the present invention, a sulfur-containing substance selected from the group consisting of elemental sulfur and metal sulfide is mixed into the laterite ore, and when calcined, they are both a sulfating agent and a fuel. In one aspect, as a sulfating agent, the sulfur-containing material provides sulfur required to convert nickel and cobalt oxides in the laterite ore to sulfate, and excess sulfur can also be formed in situ from the flue gas. On the other hand, the sulfur-containing substance can be used as a fuel, and a large amount of heat energy generated by oxidation of sulfur or sulfide is supplied to the ore for roasting without additional fuel. For example, the heat of oxidation of pyrite can be up to 12884 kJ/kg. It can not only realize the self-heating of the roasting operation, but also use the waste heat boiler to generate waste heat. Therefore, a method of separately calcining a sulfur-containing substance selected from elemental sulfur and metal sulfide to produce sulfur dioxide or sulfuric acid, and then calcining the laterite ore to convert nickel and cobalt therein to sulfate and iron to oxide In comparison, the method of the invention is clearly more economical and simple.

 The calcination of the laterite ore and a mixture of sulfur-containing substances selected from elemental sulfur and metal sulfides is carried out in an oxidizing atmosphere. The oxidizing atmosphere may be a mixed gas containing oxygen, particularly air, or an oxygen-enriched air mixture. Preferably, the proportion of oxygen is 20 - 35 vol%, preferably 20 - 30 vol%, particularly preferably 20 - 25 vol%, especially 20 vol% (i.e., directly using air) of the gas mixture.

The calcination time is from 0.5 to 5 hours, preferably from 1 to 3 hours. However, the specific time varies depending on the specific conditions of the mixture of laterite ore and a sulfur-containing substance selected from the group consisting of elemental sulfur and metal sulfide, and it is easy for a person of ordinary skill to determine the time required by the present disclosure. In the method of the present invention, the laterite ore and the baking auxiliary can be uniformly mixed and directly fed into the baking furnace without prior drying. In view of the fact that laterite ore usually contains 30% to 50% of water, this feature of the present invention is greatly reduced compared to methods requiring pre-drying, such as various pyrometallurgical methods for laterite ore and Caron for hydrometallurgy. Energy consumption.

 In the method of the present invention, after the mixture of laterite ore and a sulfur-containing substance selected from elemental sulfur and metal sulfide is calcined, non-ferrous metals such as nickel, cobalt, copper and the like are mainly present in the form of sulfate, iron. It mainly exists in the form of oxide, which is beneficial to the dissolution of nickel, cobalt and copper in the subsequent leaching operation and the control of iron in the leaching solution. The extraction rate of nickel and cobalt can exceed 90%, and the dissolution of iron can be controlled below 3%.

 In the method of the present invention, when a sulfide of nickel, cobalt, copper or iron is used as the sulfur-containing substance, nickel, cobalt and copper contained in the sulfur-containing substance are also converted into respective sulfates, and the sand is leached. The nickel and cobalt contained in the laterite ore are leached together and subsequently recovered from the leachate.

 The calcination obtained by the calcination step of the process of the present invention is leached with water, and nickel and cobalt and other non-ferrous metals such as copper are extracted into the leachate. In a preferred embodiment of the present invention, when the calcined calcined water is leached with water, the leaching temperature is from 30 ° C to 95 ° C for 0.5 - 3 h. The leaching water is added with or without an acid such as sulfuric acid, hydrochloric acid or the like, but sulfuric acid is preferably added. When sulfuric acid is added, it is preferred that the free sulfuric acid remaining in the leachate is less than 30 g/L.

 After the calcination obtained by the calcination step of the process of the present invention is leached with water, nickel and cobalt, and other non-ferrous metals such as copper, are recovered from the leaching solution which is separated from the obtained leached ore slurry. The recovery of nickel, cobalt and copper from the leachate is carried out by a method selected from the group consisting of a precipitation method, a solvent extraction method or an ion exchange method, which are themselves well known to those skilled in the art.

 The present invention also provides a method of calcining a laterite ore containing nickel and cobalt, comprising mixing a laterite ore with a sulfur-containing substance selected from the group consisting of elemental sulfur and a metal sulfide, and the resulting mixture is calcined in an oxidizing atmosphere. Among them, the sulfur-containing substance, the calcination conditions and the like are described in the calcination step in the above-described method of the present invention, and will not be described herein. It goes without saying that the product of the baking method of the present invention, i.e., calcine, can be used for further processing, extraction of metal materials therefrom, etc. or for other uses.

The invention is further illustrated by the following examples, but the invention is not limited to the following examples, and various modifications and alterations can be made thereto without departing from the spirit of the invention. Example

 Example 1

 The laterite ore containing (dry basis) 1.43% Ni, 0.041% Co, 21.43% Fe, 9.06% Mg and 35.43% moisture is finely ground to 90% over 74 μm sieve and divided into two parts, one part by weight with sulfur: 1 After mixing evenly, directly into the roaster (Test I); the other is mixed with 5 wt% (on a mineral weight basis) of concentrated sulfuric acid while mixing with sulfur at a weight ratio of 4:1, and then fed to the roaster. (Test 11). Both Test I and Test II were fired at 500 ° C for 1 h in an air atmosphere. The calcine was directly discharged from the furnace into the stirring leaching tank and leached for 2 hours. Water in the leaching tank; without additional heating, the leaching temperature in the tank can reach 80. Above C. The leached slurry was separated into solid and liquid. According to the metal content in the leaching slag and the leaching solution, the leaching rates of the two tests of nickel and cobalt were respectively calculated as Ni 90.32%, Co 93.33%, Fe 3.13% (test I); Ni 90.48% Co 93.60%, Fe 2.99% (Test 11). It can be seen that the present invention can effectively extract nickel and cobalt in laterite ore and control the dissolution of iron, and also reflects whether or not sulfuric acid is mixed in the laterite ore, and has no significant effect on the leaching result.

 Example 2

 The laterite ore of Example 1 was uniformly mixed with a cobalt-copper concentrate containing 1.62% Cu, 0.58% Co > 0.36% Ni and 28.55% S, and a weight ratio of 4:1:1. The main useful minerals of the cobalt-copper concentrate are chalcopyrite, pyrite and cobalt pyrite. The obtained mixture was calcined at 650 ° C for 2 h in an air atmosphere, and the calcination was carried out in the same manner as in Example 1 to obtain nickel, cobalt and copper leaching rates of Ni 89.95%, Co 94.02% and Cu 95.67%, respectively.

 Example 3

 The laterite ore containing 1.85% Ni, 0.053% Co and 48.2% moisture is finely ground to 90% over 74μηι sieve and divided into two parts, each containing 1.26% Ni, 0.50% Cu, 0.033% Co, 22.76% S and 46.68%. The pyrrhotite concentrate of Fe is uniformly mixed in a weight ratio of 1:1, one part is directly fed into the roaster (test I); the other part is further added with 5 wt% (based on the weight of the aforementioned mixture) of sodium sulfate and then fed to the roasting Furnace (test 11). The minerals contained in the pyrrhotite concentrate include pyrrhotite, pentlandite, chalcopyrite and pyrite. Both tests were calcined and leached as in Example 1. The leaching rates of nickel, cobalt and copper in the two tests were Ni 89.73%, Co 91.27%, Cu 93.16% (Test I); Ni 90.34%, Co 93.18%, Cu. 93.99% (Test II). Tests have shown that the leaching results of the addition of sodium sulfate are higher than the results without the addition of sodium sulfate.

Claims

Claim  A method of extracting metal from a laterite ore containing nickel and cobalt, comprising:  (1) mixing laterite ore with at least one sulfur-containing substance selected from the group consisting of elemental sulfur and metal sulfide, and the resulting mixture is calcined in an oxidizing atmosphere to convert the non-ferrous metal therein into respective sulfates, and the iron is converted into Oxide  (2) Leaching the above calcined material with water, and extracting non-ferrous metals, particularly nickel and cobalt, into the leachate.  2. The method of claim 1 wherein said laterite ore is a mixture of limonite, saprolite or both.  3. The method of claim 1 wherein said sulfur-containing material selected from the group consisting of elemental sulfur and metal sulfide is selected from the group consisting of sulfur and ores, concentrates or various similar materials of sulfide minerals containing nickel, cobalt or other metals, such as Nickel, cobalt sulfide precipitated from ore processing, niobium, etc., including sulfide minerals such as chalcopyrite, chalcopyrite, copper blue, pyrrhotite, cobalt pyrite, nickel yellow iron containing nickel, cobalt or other metals Mine, pyrite and sphalerite.  The method of claim 1, wherein a mixture of laterite ore and a sulfur-containing substance selected from the group consisting of elemental sulfur and metal sulfide is further added with a substance selected from the group consisting of alkali metal and alkaline earth metal sulfates, particularly sodium sulfate.  The method of claim 1, wherein the laterite ore is further added with sulfuric acid in a mixture of sulfur-containing substances selected from the group consisting of elemental sulfur and metal sulfide.  The method of claim 1, wherein the sulfur-containing substance selected from the group consisting of elemental sulfur and metal sulfide contains a total amount of sulfur of from 5 to 35 % by weight based on the total dry matter of the mixture to be calcined.  7. The method of claim 1 wherein said calcining temperature is from 400 °C to 850. (:.  8. The method of claim 1 wherein said oxidizing atmosphere is a mixed gas containing free oxygen, particularly air, or an oxygen-enriched air mixture.  9. Process according to claim 8, wherein the proportion of oxygen in the oxidizing atmosphere is from 20 to 35 volume%, preferably from 20 to 30% by volume, particularly preferably from 20 to 25% by volume, particularly 20% by volume, of the gas mixture.  10. A method of calcining a laterite ore containing nickel and cobalt comprising mixing a laterite ore with a sulfur-containing material selected from the group consisting of elemental sulfur and a metal sulfide, and the resulting mixture is calcined in an oxidizing atmosphere.