CN111621637A

CN111621637A - Treatment of minerals

Info

Publication number: CN111621637A
Application number: CN202010461756.1A
Authority: CN
Inventors: 亚当·贝恩·罗纳根; T·J·伊万斯; 约翰·塔克斯
Original assignee: Technological Resources Pty Ltd
Current assignee: Technological Resources Pty Ltd
Priority date: 2013-07-17
Filing date: 2014-05-01
Publication date: 2020-09-04
Also published as: CN105593386A; JP2016529396A; JP6422037B2; AU2014292792A1; AU2014292792B2; WO2015006796A1

Abstract

The present application relates to the treatment of minerals. A method of processing a non-magnetic iron-bearing material to form an iron-rich component separable from a gangue-rich component is disclosed. The method includes treating the iron-bearing material by calcining the material under reducing conditions, which results in (a) formation of separate iron-rich and gangue-rich components and (b) the iron-rich component becoming magnetic. A method of preparing an iron-containing feed material for use in a metallurgical process is also disclosed. The method includes the above-described treatment method and further includes reducing the size of the treated iron-bearing material to a particle size that enables dry, magnetic separation of the iron-rich component from the gangue-rich component and magnetically separating the iron-rich component from the gangue-rich component.

Description

Treatment of minerals

The present application is a divisional application of an application having an application date of 2014, month 5 and 1, an application number of 201480048156.5, and an invention name of "treatment of minerals".

Technical Field

A method for the dry, physical separation of valuable iron components from iron-bearing materials is disclosed. Although not exclusively, the method is applicable to tailings, waste from metal processing and non-magnetic iron-containing materials (e.g. low grade ores such as hard cap (hard cap), goethite ore and pea ore). In particular, the method relates to the preparation of non-magnetic iron-containing material for the magnetic separation of valuable iron components from non-valuable components.

Background

Magnetic separation of the valuable iron component from the iron-containing material requires that the valuable iron component be in a magnetically susceptible state. Accordingly, efforts have been focused on recovering additional quantities of magnetic iron-containing materials, such as magnetite (Fe), from ore resources that are considered too low in iron content to be economically processed₃O₄) And hematite (Fe)₂O₃)。

An example of one such method has been developed by magnetization, Inc and involves the wet processing of iron ore containing magnetite, hematite and other weakly magnetic minerals. More specifically, the ore is refined to small size (typically less than 0.6mm) and transported in a water-based slurry through a series of magnetic stations so that magnetically susceptible particles are retained in the stations. The particles are then collected as an iron-containing concentrate.

To ensure that the process is economical in capturing as much magnetic and weakly magnetic material as possible, these magnetic stations are operated with a magnetic field of about 920 gauss. Furthermore, the collected material will have a relatively high water content due to the absorption of water during the separation process. Removing this water from the collected material adds further cost to the process of extracting iron from the collected material.

A considerable amount of iron ore has an iron content that is considered too low to be economically processed. These ores have an iron content falling below a threshold of 60 wt% Fe content, which is typically required for ores suitable as blast furnace raw material. To utilize iron ore having an iron content of less than 60 wt%, it is blended with ore having an iron content of greater than 60 wt% to provide a metallurgical process feedstock having a total iron content of about 60% or greater.

While this enables some goethite ores with nearly 60 wt% Fe (feo (oh)) to be utilized, the vast majority of goethite ores have a much lower iron content. Specifically, the largest amount of goethite ore contains oolitic rocks comprising between 20 to 50 wt% Fe. Another form of goethite comprises low grade bean-like ores having between 45 and 55 wt% Fe, but less abundant than oolitic rock. The lesser abundance is still a high grade of leguminous ore with even higher Fe content (between about 55 wt% to 60 wt%).

In particular, the lower iron content of goethite ore is accompanied by higher silica and alumina contents. It is preferred to reduce the silica and alumina content of the feedstock because they are expensive to heat and handle by a blast furnace or other iron or steel manufacturing process in view of their not generating a valuable output contribution.

In order to make goethite ore (including oolitic rock) a valuable resource, it is necessary to upgrade the ore by separating the iron-containing components from the non-iron-containing components. Goethite is not magnetically sensitive. Therefore, valuable iron-containing components in goethite cannot be recovered by magnetic separation techniques such as those proposed by magnetization companies.

Accordingly, there is a need for an economically viable process that enables the recovery of valuable iron components from low grade iron ores, including but not limited to goethite, as well as from other iron-containing materials, such as tailings, and metal processing waste.

Summary of the disclosure

According to one aspect of the present invention there is provided a method of treating a non-magnetic iron-bearing material to form an iron-rich component separable from a gangue-rich component, the method comprising treating the non-magnetic iron-bearing material by roasting the material under reducing conditions which result in (a) formation of separated iron-rich and gangue-rich components and (b) the iron-rich component becoming magnetic.

The reducing conditions may include exposing the iron-containing material to reducing conditions to increase metallization of the iron-containing constituent to at least 70%.

The method may further comprise the step of reducing the particle size of the iron-containing material. This may be achieved by crushing, grinding or pulverizing and may be done before and/or after the treatment. The treatment is followed by firing under reducing conditions and the material may be allowed to cool before reducing the particle size.

After treating and reducing the particle size, the method may further include dry, magnetically separating the iron-rich component from the gangue-rich component using a low-intensity magnetic field. The term "low strength magnetic field" refers to a magnetic field of less than 1000 gauss.

Through extensive laboratory experimental work on goethite ore, the applicant has observed that roasting the ore under reducing conditions to achieve a high degree of metallization (at least 60%) converts non-magnetic ore to magnetic form. This is significant because it enables the recovery of non-magnetic ferrous materials by magnetic separation techniques. More importantly, however, the applicant has also observed that the valuable iron and non-valuable components in the ore undergo phase separation resulting in discrete iron-rich phases in the gangue-rich phase matrix.

The applicant then found through experimental work that the roasted ore preferentially broke along the grain boundaries between the iron-rich phase and the gangue-rich matrix. Thus, crushing the roasted ore produces magnetic, partially metallized, iron-rich particles that can be dry separated from the gangue-rich particles at lower magnetic fields (i.e., less than 1000 gauss).

It is expected that the roasting and magnetic separation method can be applied to a large number of available non-magnetic iron-bearing materials, such as non-magnetic iron ore resources having an iron content of less than 60 wt% Fe (i.e. low grade ore), tailings and waste from metal processes. However, in terms of iron ore, it is contemplated that roasting and magnetic separation processes may be used to upgrade low grade ore into valuable resources.

The conditions for treating the iron-containing material may include roasting the iron-containing material to a temperature in the range of 800 ℃ to 1200 ℃. Optionally, the temperature may be in the range of 850 ℃ to 950 ℃.

The firing time may vary so long as it is sufficient to cause the formation of the separated iron-rich and gangue-rich components and cause the iron-rich component to become magnetic. The iron-containing material may be subjected to a treatment for a time in the range of 1 minute to 30 minutes. The treatment time may be in the range of 5 to 30 minutes. Longer firing times of up to about 60 minutes have also been found to be effective during the course of the test.

The reducing conditions may be strongly reducing. For example, these conditions may include inclusion of 50% to 100% H by volume₂Gas and 0 to 50% by volume N₂An oxygen deficient environment of gas. Alternatively, the various forms of fuel gas include CO, CH₄(natural gas) and other gaseous hydrocarbons may also be used to control the oxygen partial pressure to provide the required reduction conditions.

The iron-bearing material may be goethite and the iron-rich component may be hematite.

The step of reducing the particle size may involve reducing the particle size of the iron-containing material to a size suitable for treatment according to the method. Alternatively, this may involve reducing the particle size of the iron-bearing material after treatment to make the iron-rich component available for separation from the gangue-rich component. In another alternative, this may involve reducing the particle size before and further after the treatment by recycling the treated material to either the initial size reduction step or by passing the treated material to a separate size reduction step. Optionally, the treated material is allowed to cool prior to reducing the particle size. One or more particle size reduction steps may produce particles of iron-containing material having a powder-like form, such as less than 4mm and preferably less than 2 mm.

One or more size reduction steps may include reducing the size of the iron-containing material to a size that causes the iron-containing material to fracture along grain boundaries between the iron-rich component and the gangue-rich component. This size reduction step may form particles having an iron-rich component and a gangue-rich component of a size less than 2 mm.

The method may involve treating the iron-containing mineral under reducing conditions in a fluidised bed.

The low intensity magnetic field is arranged to separate the iron-rich component from the gangue-rich component. The low strength magnetic field may have a field strength of less than 1000 gauss and optionally less than 500 gauss and may be in the range of 100 to 250 gauss. Furthermore, the separation step may be followed by one or more further dry, magnetic separation steps. For example, the worthless material from the dry, magnetic separation step may be recycled directly to the magnetic separation step and/or may be passed to the size reduction step or a separate size reduction step and then to the dry, magnetic separation step or to a separate dry, magnetic separation step. The conditions (e.g., magnetic field strength) of each dry, magnetic separation step may be different.

The method may further comprise controlling the reducing conditions and the separating step to recover at least 80% of the iron contained in the iron-bearing material.

Another aspect of the invention provides a method of preparing an iron-containing feed material for a metallurgical process, the method comprising:

(a) processing an iron-bearing material according to the above-described aspects to produce an iron-rich component and a gangue-rich component;

(b) reducing the size of the treated iron-bearing material to a particle size that enables magnetic separation of the iron-rich component from the gangue-rich component; and is

(c) Applying a magnetic field to the iron-containing material produced by step (b) to separate the iron-rich component from the gangue-rich component.

The method may further comprise consolidating the iron-rich constituent into a form suitable for metallurgical processing in a metallurgical vessel. The consolidation step may involve agglomerating, briquetting or pelletizing the iron-rich component.

The metallurgical processing may include a process that increases the metallization of the iron-rich component. The metallurgical processing may include a process of producing iron metal from the iron-rich component.

The present application provides the following:

1) a method of treating a non-magnetic iron-bearing material to form an iron-rich component separable from a gangue-rich component, the method comprising treating the iron-bearing material by roasting the material under reducing conditions which result in (a) formation of separated iron-rich and gangue-rich components and (b) the iron-rich component becoming magnetic.

2) The method defined in claim 1), wherein the treatment conditions comprise exposing the iron-bearing material to reducing conditions to increase metallization of the iron-bearing mineral to at least 60%.

3) The method as defined in 1) or 2), which method may further comprise the step of reducing the particle size of the iron-bearing material before and/or after the treatment.

4) The method as defined in 3), wherein after the processing of the iron-bearing material and the reduction of particle size, the method further comprises dry, magnetic separation of the iron-rich component from the gangue-rich component using a low intensity magnetic field.

5) The method defined in any one of the preceding claims, wherein the method further comprises separating the iron-rich component from the gangue-rich component by subjecting the iron-containing material to a magnetic field of less than 1000 gauss and the magnetic field is selected to separate the iron-rich component from the gangue-rich component.

6) The method as defined in any one of the preceding claims, wherein the conditions for treating the mined ore comprise roasting the iron ore at a temperature in the range of 800 ℃ to 1200 ℃.

7) The method as defined in 6), wherein the conditions for treating the mined ore comprise roasting the iron ore at a temperature in the range of 850 ℃ to 950 ℃.

8) The process as defined in 6) or 7), wherein the reducing conditions are strongly reducing.

9) As defined in any one of 6) to 8)The method of (1), wherein the conditions comprise an inclusion of 50% to 100% H by volume₂Gas and 0 to 50% by volume N₂An oxygen deficient environment for the gas.

10) The method as defined in any one of 6) to 8), wherein the conditions include the presence of a fuel gas, such as CO, CH₄An oxygen deficient environment of (natural gas) or other gaseous hydrocarbons is used to control the oxygen partial pressure to provide the required reducing conditions.

11) The method as defined in any one of the preceding claims, wherein the iron-containing material is subjected to a treatment for a time in the range of 1 minute to 60 minutes.

12) The method defined in any one of the preceding claims, wherein the iron-bearing material or ore is goethite or pisolite.

13) The method as defined in any one of claims 6) to 12), when dependent on 4), wherein the size reduction step comprises preparing particles of iron-containing material having a size of less than 4 mm.

14) The method as defined in any one of claims 4) to 13), when dependent on 3), wherein reducing the particle size of the iron-bearing material after the treatment makes the iron-rich component available for separation from the gangue-rich component.

15) The method defined in claim 13), wherein the size reducing step comprises crushing the ore to a size that causes the treated ore to fracture along grain boundaries between the iron-rich component and the gangue-rich component.

16) The method as defined in 14) or 15), wherein the size reduction step forms particles of the iron-rich component and the gangue-rich component having a size of less than 2 mm.

17) The method defined in any one of the preceding claims, wherein the method further comprises controlling the reducing conditions and the separating step to recover at least 80% of the iron contained in the iron-bearing material.

18) A method of preparing an iron-containing feed material for a metallurgical process, the method comprising the steps of:

(a) treating the iron-bearing material according to any one of the preceding claims to produce an iron-rich component and a gangue-rich component;

(b) reducing the size of the treated iron-bearing material to a particle size that enables dry, magnetic separation of the iron-rich component from the gangue-rich component; and is

19) The method as defined in 18), wherein the method further comprises the step of consolidating the iron-rich component into a form suitable for metallurgical processing in a metallurgical vessel.

20) The method as defined in 19), wherein the consolidating step comprises agglomerating, briquetting, or pelletizing the iron-rich component.

21) The method as defined in any one of 18) to 20), wherein the metallurgical processing comprises a process that increases metallization of the iron-rich component.

22) The method as defined in any one of 18) to 20), wherein the metallurgical processing comprises a process of producing iron metal from the iron-rich component.

Brief description of the drawings

Although there may be any other form which may fall within the scope of the method as outlined in the summary, specific embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

fig. 1 shows a flow chart of a method as described above for processing iron ores.

Fig. 2 is a high temperature SEM micrograph of goethite prior to treatment according to the method described above.

Fig. 3 is another high temperature SEM micrograph of goethite after treatment according to the method described above and shows a discrete phase (light) of the iron-rich component in the matrix phase (dark) of the gangue-rich component.

Description of the embodiments

The following description of the embodiments of the process described above is in the context of processing goethite iron ore. However, it will be appreciated that the method may be applied to alternative ore types and other forms of iron-bearing material, with appropriate adjustment of the processing conditions to achieve the same result. Therefore, the following description should not be construed as limiting the scope of application of the method to goethite.

With respect to fig. 1, goethite 2 is provided as mined ore to a crusher 10 to reduce the size of goethite 2 particles to a size of less than 4mm so that it is suitable for use in downstream stages of processing.

This downstream processing stage involves treating goethite 2 under reducing conditions, which results in the separation of the iron-containing component into an iron-rich component and a gangue-rich component and which causes the iron-rich component to become magnetic.

In particular, goethite 2, having passed through the crusher 10, is fed to a reactor 20, which may be, but is not limited to, a fluidized bed reactor, to which a reducing gas is fed from a gas source 30.

The conditions in reactor 20 are selected so that goethite is reduced to a degree of metallization of at least 60%. Those conditions include exposing goethite to low oxygen partial pressure environments using strong reducing conditions consisting of containing 50 to 100% by volume of H₂The atmosphere of gas is provided at a temperature greater than 800 ℃ and up to 1200 ℃. Alternatively, the various forms of fuel gas include CO, CH₄(natural gas) and other gaseous hydrocarbons may also be used to control the oxygen partial pressure to provide the required reduction conditions. The residence time of these goethite particles in the reactor 20 is controlled according to the size of the particles. Specifically, goethite 2 particles are retained in the reactor 20 for a period of time sufficient for the iron-containing material to be reduced to at least a 60% degree of metallization and phase separated into an iron-rich component and a gangue-rich component. This time may be in the range of 1 minute to 30 minutes. The treatment time may be in the range of 5 to 30 minutes, although longer treatment times of up to 60 minutes have also been found to be effective. Electron microscope images of goethite "before" and "after" the treatment are shown in fig. 2 and 3. Before treatment, goethite appeared as a single phase of nano-sized crystals. However, after treatment, a relatively pure iron-rich phase (light colored phase in fig. 3) forms as discrete particles in a gangue-rich matrix (shown as a darker phase in fig. 3). The Applicant understands that this phenomenon of phase separation is caused by selectionThe particular conditions selected for the process result.

The off-gas 32 from the reactor 20 is passed to a gas (G) -solids (S) separator, such as a cyclone separator 34, to remove dust and fine particles from the off-gas 32. A solids-free gas stream 38 is released from the cyclone 34. This can be processed and released into the atmosphere.

The treated goethite particles from the reactor 20 are sent to a crushing or grinding stage 40, which further reduces the size of these particles. The applicant has found that the treated particles when crushed or ground have a tendency to fracture along the grain boundaries between the iron-rich phase and the gangue-rich phase. The effect of the crushing stage 40 is therefore to make the iron-rich phase available for separation from the gangue-rich phase.

The treated ore leaving the crushing stage 40 is passed to a magnetic separation stage 50. However, the solid particles and dust removed from the off-gas 32 in the cyclone 34 are sent via line 36 to be combined with the treated and crushed goethite so that it also passes through the magnetic separation station 50.

The magnetic separation stage 50 is configured for exposing the treated and crushed particles to a magnetic field that separates an iron-rich phase from a gangue-rich phase. The iron-rich phase is magnetic and it reacts to the magnetic field by, for example, being attracted to the surface of the magnet. The iron-rich particles are then collected from the magnet. Experimental work carried out by the applicant revealed that exposing the treated and crushed particles to a magnetic field of less than 1000 gauss was sufficient to separate the iron-rich phase from the gangue-rich phase when the magnet was placed in proper proximity to the treated and crushed goethite. However, the magnetic iron-rich particles may be separated under a magnetic field in the range of 100 to 250 gauss. It has been found that a wound roll magnet is particularly suitable for separating the iron-rich phase from the gangue-rich phase. As the iron-rich phase is attracted to the drum, it is believed that the drum magnet functions by separating the gangue-rich phase from the iron-rich phase.

The ability to separate the iron-rich phase from the gangue-rich phase with a low strength magnetic field is a significant improvement over previous magnetic separation processes that required significantly larger magnetic fields. The above described treatment process therefore contributes to a reduction in the overall economic investment for recovering iron from goethite, including a reduction in the costs associated with this magnetic separation stage.

The iron-rich phase 54 is recovered from the magnetic separation stage 50 as a reduced ore product containing 90% to 95% of the iron contained in the mined goethite.

The laboratory test work carried out by the applicant involves subjecting low grade (stringy) goethite to the process described above. In particular, the processing conditions include crushing the ore to a size of less than 2mm, exposing the ore to primarily H in a fluidized bed reactor at a temperature of greater than 800 ℃₂Gas or other reducing gas and balance N₂A reducing atmosphere of gas. The ore is retained in the reactor for a period of time to achieve greater than 60% metallization of the iron-containing mineral. The treated ore is then subjected to magnetic separation by exposure to a magnetic field of less than 1000 gauss and as low as 100 gauss.

The following table shows an example of some of the results of the above experimental work carried out on iron ore waste from Mesa a wells in the Pilbara (Pilbara) region of Western Australia (Western Australia). In particular, the table shows the iron, silica and alumina content of mined ore, treated ore, reduced ore products obtained from the magnetic separation step and non-magnetic waste products.

The reduced ore product obtained from this process has an iron content of almost 79%. This is a significant upgrade of mined ore that contains iron content slightly greater than 50%, i.e. well below the 60% threshold for use in metallurgical processes. Thus, the above described process enables upgrading of ores to reduced ores with significantly higher iron content. This means that low grade ore can be upgraded to form an economically valuable resource. It is contemplated that the process may be used to upgrade tailings, hard cap and ore waste streams, such as low grade ores, including both pisolites and goethite. This experimental work shows that ores with as low as 45% iron content can be upgraded to form products containing more than 60% iron on an ore equivalent basis.

The product obtained from the magnetic separation is used as a feedstock for a metallurgical process to obtain iron metal (i.e. by increasing the metallisation to 100%). Although the product may be used as a feedstock for a molten bath-based metallurgical process, the relatively fine particle size of the product means that it cannot conventionally be added directly to a metallurgical process that relies on exposing the iron-bearing material to a reducing gas, such as a blast furnace or rotary hearth furnace, as the product will impede the flow path of the reducing gas through the charge. Thus, the product can be formed into suitably sized lumps by agglomeration, briquetting or pelletizing processes, so that it can be used in blast or rotary hearth furnaces. A series of methods are known for forming a raw material briquette of an iron-containing material. Any of those methods may be used to form the agglomerated feedstock. Alternatively, the product may be injected into the blast furnace via tuyeres, such as with pulverized coal.

Although one method embodiment has been described, it should be understood that the method can be implemented in many other forms.

It will be understood that, if any prior art publication or existing or typical method is referred to herein, this reference does not constitute an admission that the publication or method forms a part of the common general knowledge in the art, in australia or any other country.

In the claims which follow, and in the preceding description, except where the context requires otherwise, due to express language or necessary implication, the terms "comprises" and "comprising" in various embodiments of the devices and methods as disclosed herein are used in an inclusive sense, e.g. to specify the presence of the stated features but not to preclude the presence or addition of further features.

Claims

1. A method of processing goethite to form an iron-rich constituent separable from a gangue-rich constituent, wherein the goethite exhibits a single phase of nano-sized crystals, the method comprising:

(a) treating the goethite by roasting the goethite under reducing conditions at a roasting temperature of greater than 800 ℃ and less than 1200 ℃ for up to 60 minutes and forming (i) an iron-rich component having a magnetic character of at least 60% metallization and (ii) a separated gangue-rich component,

(b) the particle size of the goethite is reduced,

(c) dry, magnetic separation of the iron-rich component from the gangue-rich component is performed using a low intensity magnetic field of less than 1000 gauss.

2. The method defined in claim 1, wherein the conditions for treating the goethite include a roasting temperature in the range of 850 ℃ to 950 ℃.

3. The method defined in claim 1, wherein the reducing conditions are strongly reducing.

4. The method defined in claim 1, wherein the conditions comprise 50% to 100% H by volume₂Gas and 0 to 50% by volume N₂An oxygen deficient environment for the gas.

5. The method defined in claim 1 wherein the conditions include an oxygen deficient environment containing fuel gas for controlling the oxygen partial pressure to provide the required reducing conditions.

6. The method defined in claim 5 wherein the fuel gas is CO, CH₄Or other gaseous hydrocarbons.

7. The method defined in claim 1, wherein the goethite is subjected to treatment for a time in the range of 1 minute to 60 minutes.

8. The method defined in claim 1, wherein the size reduction step includes preparing particles of the treated goethite having a size of less than 4 mm.

9. The method defined in claim 1, wherein reducing the particle size of the treated goethite after the treatment comprises making the iron-rich component available for separation from the gangue-rich component.

10. The method defined in claim 8, wherein the size-reducing step comprises crushing the treated goethite to a size that causes the treated goethite to fracture along grain boundaries between the iron-rich component and the gangue-rich component.

11. The method as defined in claim 9 wherein the size reducing step forms particles of the iron-rich component and the gangue-rich component having a size of less than 2 mm.

12. The method defined in claim 1, wherein the method further comprises controlling the reduction conditions and the separation step to recover at least 80% of the iron contained in the goethite.

13. A method of preparing an iron-containing feedstock for a metallurgical process, the method comprising the steps of:

(a) treating goethite according to any one of claims 1 to 12 to produce an iron-rich component and a gangue-rich component;

(b) reducing the size of the treated goethite to a particle size that enables dry, magnetic separation of the iron-rich component from the gangue-rich component; and is

(c) Applying a magnetic field to the treated goethite produced by step (b) to separate the iron-rich component from the gangue-rich component.

14. The method defined in claim 13 wherein the method further comprises the step of consolidating the iron-rich constituent into a form suitable for metallurgical processing in a metallurgical vessel.

15. The method defined in claim 14 wherein the consolidating step includes agglomerating, briquetting or pelletizing the iron-rich component.

16. The method defined in claim 14 wherein the metallurgical process increases metallisation of the iron-rich component.

17. The method defined in claim 14 wherein the metallurgical process produces iron metal from the iron-rich component.