WO2015015250A1

WO2015015250A1 - Process for enhanced pre-reduction of chromite

Info

Publication number: WO2015015250A1
Application number: PCT/IB2013/056313
Authority: WO
Inventors: Johan Paul BEUKES; Pieter Gideon VAN ZYL; Bryson NEIZEL
Original assignee: North West University
Current assignee: North West University
Priority date: 2013-08-01
Filing date: 2013-08-01
Publication date: 2015-02-05
Anticipated expiration: 2016-02-01
Also published as: ZA201600611B; CA2919974C; CN105612264A; CA2919974A1

Abstract

The present invention relates to a process for the partial oxidation of unagglomerated chromite ore and to the use of the claimed process in currently applied ferrochromium production processes. According to a first aspect thereof, the present invention provides a process for the partial oxidation of chromite. The said process includes the steps consisting of: (i) providing a source of unagglomerated chromite ore; (ii) subjecting the source of unagglomerated chromite ore to pre-oxidation at a temperature of 700" C to 1 100°C, both values inclusive; (iii) controlling the above-mentioned pre-oxidation temperature such that maximum migration of iron (Fe) to the surface of the chromite ore particles takes place and minimum Cr203 formation takes place; and (iv) forming a pre-oxidized source of unagglomerated chromite ore wherein maximum migration of iron (Fe) to the surface of the chromite ore particles takes place, as well as minimum Cr203 formation takes place. The present invention further provides for the use of the product prepared in accordance with the foregoing process.

Description

PROCESS FOR ENHANCED PRE-REDUCTION OF CHROMITE

FIELD OF APPLICATION OF THE INVENTION

The present invention relates to a process for the partial oxidation of unagglomerated chromite ore and to the use of the claimed process in currently applied ferrochromium production processes.

BACKGROUND TO THE INVENTION

Stainless steel is a vital modern day alloy. Virgin chromium units used in the manufacturing of stainless steel are obtained from ferrochromium - an alloy consisting mostly of chromium and iron. Ferrochromium production is an energy intensive process, with specific electricity consumption (referred to herein as "SEC") varying from 2.4 to more than 4.0 MWh/ton ferrochrome produced, depending on the process applied. This makes electricity consumption the largest cost component in ferrochromium production.

The art teaches of a number of processes which are currently used for ferrochromium production. A flow diagram, proposed by Riekkoal-Vanhanen (1999) and updated by Beukes er al. (2010), indicating the most common process steps, utilized in these processes for ferrochromium production, is indicated in Figure 1. Whilst some variations may occur, four relatively well-defined process combinations are currently utilized as are discussed herein below with reference to the flow diagram. Conventional open or semi-closed submerged arc furnace (SAF) operations, with bag filter off-gas treatment. This is the oldest technology, but still accounts for a substantial fraction of overall production. In this type of operation, coarse ores

(lumpy and chips/pebble ores) are smelted together with fluxes and reductants. A limited fraction of fine ore (smaller than 6mm) can be fed with the lumpy ore, since excessive fines can cause dangerous blow-outs or bed turnovers. With reference to the process flow diagram indicated in Figure 1 , the process steps followed are 5, 7, 8,

9 and 10. Specific energy consumption (SEC), that is MWh/ton of ferrochrome produced, of conventional ore fed open/semi-closed SAF operations is typically greater than 3.5 MWh/ton ferrochrome (FeCr). Some open/semi-closed SAF operations do consume pelletised feed, in which case process steps 1 -4 would also be included. This could lead to some improvement in SEC, however the SEC is likely to remain greater than 3 MWh/ton FeCr. Most of the open/semi-closed SAF operations are operated on an acid slag, with a basicity factor (BF) smaller than 1.

Equation 1 defines the basicity factor (BF):

pp %CaO - % gO _m %SiO ₂ '

Some open/semi-closed SAF operations might operate on a BF of greater than 1 , but these are less common and such operations are sometimes only temporarily undertaken to compensate for refractory linings being in poor condition, or if enhanced sulphur removing capacity by the slag is required.

Closed SAF operations, utilising oxidative sintered pelletised feed (Outotec technology or, as was referred to in the older literature, Outokumpu technology http://www.outotec.com/pages/Page. aspx?id=7536&epslanquage=EN). This has been the technology most commonly employed in South Africa, with the majority of green and brown field expansions during the last decade utilizing the same. Process steps usually include steps 1 , 2, 3, 4, 5, 7, 8, 9 and 1 1 , with or without step 6. In all green field ferrochromium developments, the pelietising and sintering (steps 2 and 3) sections are combined with closed SAFs. SEC is typically greater than 3,1 MWh/ton FeCr. These SAF operations are usually operated on an acid slag (having a BF of less than 1 ). Prior to pelletisation, typically 1 - 1.5% clay binder and 1 - 2% reductant, serving as an energy source to achieve the required sintering temperature (typically higher than 1200X), are added.

Oxidative pelietising and sintering sections have also been constructed at plants where the pelletised feed is utilised by conventional open/semi-closed SAFs (Process (I)).

Closed SAF operations with pre-reduced pelletised feed (Botha, 2003; Naiker, 2007). This process is commonly referred to as the Premus process (applied by GlencoreXstrata Alloys) and is also known as the solid state reduction of chromite (SRC process) and was developed by Showa Denko in Japan in the ~1970's. The process steps include steps 1 , 2, 3, 4, 5, 7, 8, 9 and 1 1. The pelletised feed differs substantially from the oxidative sintered type due to the fact that the pellets are pre- reduced and mostly fed hot, directly after pre-reduction, into the SAF. Approximately 3.5 - 5% clay binder and 12 - 16% fixed carbon (from a reductant) are added to the mixture prior to pelletisation. The relatively high level of reductant in the agglomerates (pellets), if compared to the oxidative sintered process of Outotec (Process (II)), is required to achieve pre-reduction. The SAFs are closed and operate on a basic slag (having a BF of greater than 1 ).

At present, only two ferrochromium smelters (GlencoreXstrata Lydenburg operations and GlencoreXstrata/Merafe Lion Ferrochrome) use this process. SEC is usually 2.2 - 2.6 MWh/ton, depending on the level of chromite pre-reduction achieved. In all currently commercially operated plants, counter current rotary kilns are used to achieve pre-reduction. Other equipment could also be used to achieve pre-reduction. These include, but are not limited to, vertical shaft furnaces (Niayesh and Dippenaar, 1992) and multi hearth furnaces (http://www.paulwurth.com/en/Our- Activities/Recvclinq-technoloqies/Primus).

(IV) Direct current (DC) arc furnace operations (Curr, 2009; Denton, 2004). For this type of operation, the feed can consist exclusively of fine ores. An agglomeration step is therefore not required. These DC furnaces typically utilize a basic slag regime. Process steps include 5, 7 (with a DC, instead of a SAF), 8, 9 and 1 1. SEC is relatively high, with a SEC of greater than 3.8MWh/ton being common.

Against the backdrop of the foregoing discussion, it can be seen that numerous ferrochrome production processes are applied and all of these processes are highly energy intensive. The process option with the lowest SEC is the pelletelised chromite pre-reduction process (solid state reduction of chromite), also known as the Premus process, currently applied by GlencoreXstrata Alloys (Process (III)). With this process, a SEC of approximately 2.4 MWh/ton ferrochrome is commonly achieved, if typical South African chromite ore is consumed. In the currently applied Premus process, fine chromite ore is milled with a carbon reducing agent and a clay binder and agglomerated (i.e. pelletised, although briquetting could also be used), followed by pre-reduction of the agglomerated chromite ore prior to smelting the pre-reduced ore in a SAF.

Currently applied ferrochrome production options not utilizing pre-reduction of chromite (solid state reduction of chromite) use more than 3 MWh/ton of ferrochrome produced. These process options include, but are not limited to, conventional smelting of chromite ore in open/semi-closed/closed furnaces (Process (I) as discussed herein above), smelting of sintered pellets with the Outotec process (Process (II) as discussed herein above), as well as smelting of chromite ore fines in the direct current arc (DC arc) furnaces (Process (IV) as discussed herein above).

Further examples of production processes not utilizing pre-reduction of chromite (solid state reduction of chromite) are exemplified in, inter alia, US Patent No. 546,681 to Marvin Udy and US Patent No. 6,001 ,148 to Okamoto er a/.

The former patent teaches of a process wherein chromite ore, which is provided in finely divided form, is subjected to an oxidizing treatment in the presence of lime to remove the carbon contained therein and to oxidize a portion of the chromium to hexavalent (VI) chromium (i.e. chromate or dichromate). Oxidation takes place at a temperature of 1000^'C and it is mentioned that the oxidation agent may function as a bonding agent to form agglomerates, whilst the increased temperature enhances fusion thereof.

This prior art document teaches that the oxidizing treatment takes place prior to treatment with a reducing agent (line 86). In this regard, it is important to take cognizance of the fact that, in the art, smelting is often also referred to as a reduction step, however in contrast to the pre-reduction process (solid state reduction of chromite), molten/liquid materials are formed during the smelting reduction process. No molten/liquid states are formed during pre-reduction (solid state reduction of chromite). Accordingly, the alterative name for prereduction, namely solid state reduction of chromite, illustrates this concept clearly. In the light of the aforesaid, it is clear that the reduction referred to and taught in this patent is reduction occurring during the smelting step and must not be read as or confused with being a prereduction step (solid state reduction step of chromite). Furthermore, in this patent, it is mentioned that any suitable non-carbonaceous reducing agent may be employed (lines 106- 107). It is mentioned that preferably silicon or a silicide may be employed. As will become apparent from reading of the Summary of the Invention, it is pertinent to note that a non- carbonaceous reducing agent of this nature will not be suitable for purposes of the instant invention. In view hereof, it is clear that this patent goes against the teachings of the present invention.

Turning to the latter patent, namely US Patent No. 6,001 ,148, this patent discloses a process wherein a pulverized metal oxide (such as iron oxide or chromium oxide) is brought into contact with a high temperature flame from a burner. It is mentioned that the burner can be an oxygen burner or an oxygen enriched burner. This patent further teaches that the metal oxide particles are melted by the flame and a reducing agent is supplied in order to initiate the reducing reaction. From a perusal of this prior art document, it is thus clear that a molten metal oxide is formed, which molten material is accordingly formed during a smelting reduction step and not during a pre-reduction (solid state reduction of chromite) step. From a reading of the disclosures set forth herein below, it will become evident that this patent neither discloses nor teaches the present invention.

In view hereof, processes employing smelting wherein no pre-reduction step prior thereto takes place should not be confused with those processes incorporating a pre-reduction step (solid state reduction step), irrespective of whether smelting is referred to as reduction.

Returning to currently applied processes employing a chromite pre-reduction (solid state reduction of chromite) step, various additives have been proposed in the art to enhance prereduction. These include CaC0₃, NaCI, CaF₂, NaF-CaF₂, Na₂B₄0₇, NaF, Na₂C0₃, CaB₄0₇, B₂0₃, CaCI, Si0₂, Al₂0₃, K₂C0₃, Na₂0₂, CaO, MgO, Fe ,Cr and K₂0 (e.g. Dawson and Edwards 1986; Katayama et al., 1986; Van Deventer, 1988, Nunnington and Barcza, 1989; Ding and Warner, 1997a; Ding and Warner, 1997b; Lekatou and Walker, 1997; Weber and Eric, 2006; Takano et al., 2007). However, the use of additives is not often practiced. This is primarily attributed to the fact that additives lead to degeneration of the chromite ore agglomerates (e.g. pellets) whilst, in some instances, these additives could contaminate the ferrochrome produced.

In the light of the above, it is clear that a means of successfully improving chromite prereduction by utilizing pre-oxidation has neither been disclosed nor taught in the art.

In view of the foregoing, it is therefore apparent that there is a clear need in the art for a process capable of achieving a reduction in SEC expended during ferrochromium production. In particular, there is a need for a process which enhances chromite prereduction, which process steps do not suffer from the disadvantages associated with those of the prior art.

It is thus an objective of the present invention to provide a process which is capable of achieving a significant reduction in SEC spent during ferrochromium production processes.

It is a further objective of the present invention to provide a process which improves/enhances chromite pre-reduction (solid state reduction of chromite).

It is a yet further objective of the invention to provide a process which is capable of affording either one or both of the two aforementioned objectives whilst being able to be used in conjunction with any suitable existing process that is currently used for ferrochromium production. SUMMARY OF THE INVENTION

According to a first aspect thereof, the present invention provides a process for the partial oxidation of chromite, said process including the steps consisting of:

(i) providing a source of unagglomerated chromite ore;

(ii) subjecting the source of unagglomerated chromite ore to pre-oxidation at a temperature of 700^' C to 1 100^°C, both values inclusive;

(iii) controlling the above-mentioned pre-oxidation temperature such that maximum migration of iron (Fe) to the surface of the chromite ore particles takes place and minimum Cr₂0₃ formation takes place; and

(iv) forming a pre-oxidized source of unagglomerated chromite ore wherein maximum migration of iron (Fe) to the surface of the chromite ore particles takes place, as well as minimum Cr₂0₃ formation takes place.

The resulting pre-oxidized source of unagglomerated chromite ore is envisaged to be used as a starting material for currently applied ferrochromium production processes used in the art.

The process of the present invention achives partial oxidation of chromite. It will be appreciated that this partial oxidation is distinct from complete oxidation of chromite. Furthermore, this partial oxidation precedes subsequent ferrochromium production processes known and used in the art and accordingly is referred to as "pre-oxidation" for purposes of the present spectifi cation.

In an embodiment of the invention, said currently applied ferrochromium production processes may involve pre-reduction of chromite (solid state reduction of chromite) as is carried out in closed SAF operations, as is currently utilized by GlencoreXstrata Alloys in their Premus process. In an alternative embodiment of the invention, said processes may involve DC arc furnace operations. These features are discussed in more detail herein below.

Source of unaqglomerated chromite ore

Chromite (iron chromium oxide) exists as a spinel structure and has the basic formula FeOCr₂0₃. For purposes of the present specification, chromite is also referred to herein as

FeCr₂0₄.

In terms of the present invention, the source of unagglomerated chromite ore may be in the form of fine chromite ore. In accordance with the present invention, fine chromite ore is understood to denote chromite ore particles smaller than 6mm. However, typical metallurgical grade chromite ore, as used in the present invention, is usually smaller than 1 mm in size.

It will be appreciated that the ratio of chromium to iron in the source of unagglomerated chromite ore may vary substantially depending on the chemical composition of the ore body from which the source of chromite ore is obtained or derived from. For instance, the Cr to Fe ratio of typical chromite ore mined for ferrochromium production in South Africa is approximately 1 .45: 1 - 1 .55: 1 (between 48% to 50% Cr₂0₃), whilst the Cr to Fe ratio of chromite ore mined, for example, in Zimbabwe have Cr to Fe ratios of 2.6: 1 to 3.5: 1 (between 43% to 54% Cr₂0₃) (Howat, 1994).

In an embodiment of the invention, the source of unagglomerated chromite ore may be selected from the group consisting of metallurgical grade chromite ore, chemical grade chromite ore, UG2 chromite ore, milled chromite ore or a combination of two or more thereof from any deposit.

Pre-oxidation

Pre-oxidation of the unagglomerated chromite ore takes place in air. Pre-oxidation is carried out at a temperature range of 700 C to 1100^°C, both values inclusive. In one embodiment of the invention, a temperature range of 800 C to 1000 C (both values inclusive) is employed. According to a preferred embodiment of the invention, pre-oxidation takes place at a temperature of 1000^'C.

It is important that the pre-oxidation temperate is controlled to ensure that maximum migration of iron (Fe) to the surface of the chromite ore particles takes place and minimum Cr₂0₃ formation takes place.

The Inventors have unexpectedly and surprisingly found that when pre-oxidation of the unagglomerated chromite ore is carried out at a temperature of from 800^°C up to and including 1000^*C and where the process, as set forth in the first aspect of the invention, is employed prior to current commercial processes involving the pre-reduction of chromite (solid state reduction of chromite), a significant enhancement in pre-reduction of chromite is achieved.

For the specific ore utilised for demonstration purposes in this invention, the Inventors have also found that at a pre-oxidation temperature of below 800 C and at a temperature of above 1000^°C, no significant improvement in subsequent pre-reduction was achieved. Enhancing pre-reduction is highly desirable and advantageous as the inventors believe that this would lead to a significant reduction in the SEC spent by currently applied ferrochromium production processes involving chromite pre-reduction. As has been discussed hereinbefore, such desired enhancement in pre-reduction has not been successfully achieved in the art, despite the use of additives and the like.

It will of course be appreciated that the preferred pre-oxidation temperature range may vary, depending on the chemical composition of the source of unagglomerated chromite ore employed in the process of the present invention.

In addition hereto, it is important that the temperature at which pre-oxidation is performed be controlled at a temperature of 800^°C up to and including 1000^'C to ensure that the oxidation state of Cr(lll) is not changed to hexavalent (Cr(VI)) chromium. Typical forms of Cr(VI) include chromate and dichromate.

In this regard, it is important that the pre-oxidation step of the present invention is not confused with alkaline roasting which takes place at a high temperature and in accordance with the following reaction:

Cr(lll) + 0₂ + 2Na₂C0₃→ Cr(VI) + 2Na₂0 + 2C0₂ + 0₂ (2)

In the case of alkaline roasting, hexavalent Cr is formed. As is discussed in detail further herein, chromium in its hexavalent state is undesirable owing to the toxicity/carcinogenicity associated with chromium in this oxidation state and accordingly the formation of hexavalent Cr during the process of the instant invention is to be minimized if not negated.

In addition hereto, it is important that pre-oxidation of the unagglomerated chromite ore prior to pre-reduction (solid state reduction of chromite), as disclosed and taught by the present invention, is not confused with oxidation prior to sme!ting. As mentioned herein before, the smelting step is often also referred to as a reduction step, however in contrast to the prereduction process (solid state reduction of chromite) where no molten/liquid material forms, molten/liquid materials are formed during the smelting reduction process. Ferrochrome production processes where oxidation is applied prior to the smelting step are common. The most commonly applied is the Outotec chromite sintering process (Process (II) discussed herein before) that utilizes oxidation as a means of forming strong agglomerates, i.e. pelletised chromite, prior to smelting this agglomerated ore in a SAF. However, it is important to note that this process does not include a pre-reduction (solid state reduction of chromite) step prior to smelting the agglomerated ore. Various researchers have indicated that oxidation prior to smelting (reduction in furnace to liquid states) results in reduced energy consumption during the smelting step (e.g. Zhao and Hayes, 2010). Recently Kapure et al. (2010) also presented a process that incorporates oxidation prior to smelting/direct reduction to form molten phases. However, these processes differ substantially from the pre-reduction process, since no molten/liquid state is formed in the pre-reduction process (solid state reduction of chromite). Accordingly, whilst the art teaches of oxidation prior to smelting, literature is completely silent about the use of pre-oxidation prior to pre-reduction.

As mentioned herein before, it is envisaged that the process described in steps (i) to (iv) in accordance with the first aspect of the invention may take place prior to currently applied ferrochromium production process involving the pre-reduction of chromite (solid state reduction of chromite). These include, but are not limited to, processes employing counter current rotary kilns (as used in the Premus process employed by GlencoreXstrata Alloys), vertical shaft furnaces (Niayesh and Dippenaar, 1992) and multi hearth furnaces (http://www.paulwurth.com/en/Our-Activities/Recvclinq-technoloqies/Primus). Thus, according to a second aspect thereof, the present invention provides a process for enhancing the pre-reduction (solid state reduction) of chromite, said process including the steps consisting of:

(i) providing a source of unagglomerated chromite ore;

(ii) subjecting the source of unagglomerated chromite ore to pre-oxidation at a temperature of 700 C to 1 100^'C, both values inclusive;

(iii) controlling the temperature such that maximum migration of iron (Fe) to the surface of the chromite ore particles takes place and minimum Cr₂0₃ formation takes place;

(iv) forming a pre-oxidized source of unagglomerated chromite ore wherein maximum migration of iron (Fe) to the surface of the chromite ore particles takes place and minimum Cr₂0₃ formation takes place;

(v) contacting the pre-oxidized source of unagglomerated chromite ore with a suitable binder and/or a suitable reductant;

(vi) subjecting the chromite product of step (v) to milling or grinding;

(vii) agglomerating the milled or ground chromite product of step (vi);

(viii) subjecting the agglomerated chromite product of step (vii) to pre-reduction (solid state reduction); and

(ix) smelting the pre-reduced chromite product of step (viii) to form a molten chromite product.

Reductants

In terms of the present invention, any suitable carbonaceous source may be used as the reductant (reducing agent). In an embodiment of the invention, the reductant may be selected from the group consisting of coke, coal, anthracite and char. Binders

In terms of the present invention, any suitable binder, such as clay, may be used. Agglomeration

Agglomeration may be achieved by either pelletizing or briquetting the milled or ground chromite product of step (vi).

Pre-reduction (solid state reduction)

Suitable reductants, as described herein before, in desired concentrations may be added to the agglomerated chromite product of step (vii) and thereafter subjecting the resulting product to pre-reduction.

In an embodiment of the invention, pre-reduction may take place according to the temperature profile suggested by Kleyhans et al. (2012), which simulates the currently applied chromite pre-reduction industrial process conditions (solid state reduction of chromite). This profile consists of three segments, namely i) heating up from room temperature to 900°C over a period of 30 minutes, ii) heating up to 1300°C over 50 minutes, iii) and finally cooling to room temperature, said three steps taking place in an inert atmosphere.

In terms of the present invention, various types of equipment may be employed in order to achieve pre-reduction. Non-limiting examples of the type of equipment that may be used include a counter current rotary kiln, vertical shaft furnaces and multi hearth furnaces. During the pre-reduction step, Fe(i!) and/or Fe(lll) present in the chromite is partially reduced to metallic iron and/or iron carbides, while Cr(lil) in the chromite is partially reduced to metallic chromium and/or chromium carbides.

Smelting

Smelting, as indicated in step (ix) may occur in any suitable open, semi-open or closed SAF and/or DC arc furnace, with the addition of suitable fluxes (including, but not limited to, quartz, limestone, magnesite and dolomite), additional lumpy (coarse) reductants and additional chromite ores, as required.

According to a third aspect thereof, the present invention provides a process for enhancing the pre-reduction (solid state reduction) of chromite in the currently applied Premus (solid state reduction of chromite) operation applied by GlencoreXstrata Alloys, said process including the steps consisting of:

(i) providing a source of unagglomerated chromite ore;

(ii) subjecting the source of unagglomerated chromite ore to pre-oxidation at a temperature of 700 C to 1 100 C, both values inclusive;

(iii) controlling the pre-oxidation temperature such that maximum migration of iron (Fe) to the surface of the chromite ore particles takes place and minimum Cr₂0₃ formation takes place;

(iv) forming a pre-oxidized source of unagglomerated chromite ore wherein maximum migration of iron (Fe) to the surface of the chromite ore particles takes place and minimum Cr₂0₃ formation takes place; and

(v) introducing the pre-oxidized source of unagglomerated chromite ore as a feed material to said currently applied Premus operation. In terms of the present invention, it is estimated that when the process described according to the third aspect of the invention is carried out, an additional SEC reduction of approximately 9% is achieved.

It will be appreciated that this value of 9% is dependent on the maximum temperature achieved in the counter current rotary kiln where pre-reduction is obtained, as well as the retention time of the agglomerates in the counter current rotary kiln. Additionally, it will be appreciated that the afore-mentioned value (9%) will also vary depending on the composition of the source of unagglomerated chromite ore. Accordingly, where the source of unagglomerated chromite ore contains a low Fe content, the SEC will be reduced by a value that will be less than 9%. Thus, where the starting ore is obtained from South Africa, the reduction in SEC that is achieved by the process of the instant invention will differ to the reduction in SEC that is achieved where the starting ore is obtained from, inter alia, India, Zimbabwe or Kazakhstan.

As was mentioned herein before, the resulting pre-oxidized source of unagglomerated chromite formed during the process recited in terms of the first aspect of the present invention is envisaged to be used as a starting material for any suitable currently applied ferrochromium production process used in the art.

Thus according to a fourth aspect thereof, the present invention provides a process for significantly improving specific electricity consumption (SEC) in currently applied ferrochromium production operations, said process including the steps consisting of:

(i) providing a source of unagglomerated chromite ore;

(ii) subjecting the source of unagglomerated chromite ore to pre-oxidation at a temperature of 700^'C to 1 100 C, both values inclusive; (iii) controlling the temperature such that maximum migration of iron (Fe) to the surface of the chromite ore particles takes place and minimum Cr₂0₃ formation takes place;

(v) introducing the pre-oxidized source of unagglomerated chromite ore to any suitable currently applied ferrochromium production process used in the art.

In accordance with a fifth aspect of the present invention, the present invention provides a process for significantly improving specific electricity consumption (SEC) in DC arc furnace operations, said process including the steps consisting of:

(i) providing a source of unagglomerated chromite ore;

(v) introducing the pre-oxidized source of unagglomerated chromite ore to any suitable DC arc furnace operation.

As mentioned herein before, whilst the addition of additives has been documented in the art in an attempt to enhance pre-reduction, the Inventors have now found that by pre-oxidizing the unagglomerated chromite ore in the presence of an additive, a significant improvement in SEC can be achieved, particularly when employed in combination DC arc furnace smelting. Thus, in accordance with a sixth aspect of the present invention, the present invention provides a process for significantly improving specific electricity consumption (SEC), said process including the steps consisting of:

(i) providing a source of unagglomerated chromite ore;

(ii) providing an additive selected from the group consisting of, but not limited to, CaC0₃, CaO, and Ca(OH)₂;

(iii) subjecting the source of unagglomerated chromite ore to pre-oxidation in the presence of the additive at a temperature of 700^"C to 1 100 C, both values inclusive;

(iv) controlling the temperature such that maximum migration of iron (Fe) to the surface of the chromite ore particles takes place and minimum Cr₂0₃ formation takes place; and

(v) forming a pre-oxidized source of unagglomerated chromite ore wherein maximum migration of iron (Fe) to the surface of the chromite ore particles takes place and minimum Cr₂0₃ formation takes place.

The pre-oxidized source of unagglomerated chromite ore prepared according to the process detailed according to the sixth aspect of the present invention may be employed in DC arc furnace operations.

In terms of the present invention, a further feature thereof provides for the use of the process as set forth in the first aspect of the invention.

A yet further feature of the present invention provides for the use of the process as set forth in the second aspect of the invention.

A still further feature of the present invention provides for the use of the process as set forth in the third aspect of the invention. Another feature of the present invention provides for the use of the process as set forth in the fourth aspect of the invention.

An additional feature of the present invention provides for the use of the process as set forth in the fifth aspect of the invention.

A yet further additional feature of the present invention provides for the use of the process as set forth in the sixth aspect of the invention.

The invention also provides for the product prepared in accordance with the first aspect of the instant invention.

Further, in accordance with another feature of the present invention, there is provided the product prepared in accordance with the second aspect of the instant invention.

The invention further provides for the product prepared in accordance with the third aspect of the instant invention.

Still further, the invention provides for the product prepared in accordance with the fourth aspect of the instant invention.

Still yet further, the invention provides for the product prepared in accordance with the fifth aspect of the instant invention.

The invention provides for the product prepared in accordance with the sixth aspect of the instant invention. These and other objects, features and advantages of the invention will become apparent to those skilled in the art following the detailed description of the invention read with reference to the appended Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1: is a flow diagram indicating the most common process steps utilized by currently applied processes for ferrochromium production;

Figure 2: is a graph depicting the effect of pre-oxidizing chromite ore in accordance with the process of the present invention prior to agglomeration and pre-reduction and depicting the extent of chromite pre-reduction (y-axis) at the different pre- oxidation temperatures (x-axis);

Figure 3: is a Scanning Electron Microscope (SEM) micrograph showing the migration of iron (Fe) from the chromite ore spinel to the surface of the chromite ore particle as a result of pre-oxidation of the chromite ore;

Figure 4A: depicts an X-ray diffraction (XRD) spectrum for un-oxidized chromite ore, indicating no free Cr₂0₃;

Figure 4B: depicts an XRD spectrum for chromite ore pre-oxidized at a temperature of

1000°C indicating no free Cr₂0₃;

Figure 4C: depicts an XRD spectrum for chromite ore pre-oxidized at a temperature of

1400°C indicating the presence of free Cr₂0₃ formed during pre-oxidation of chromite ore;

Figure 4D: is an XRD peak list which Figures 4A, 4B and 4C are to be referenced against; Figure 5: is a graph indicating the thermodynamic calculations conducted for determining the ease with which Fe oxides, chromite ore (FeCr₂0₄) and Cr₂0₃ are reduced with a solid carbonaceous material and/or CO(gas). From this Figure, it is evident that Cr₂0₃ reduction requires more extreme conditions in comparison to Fe oxide reduction and chromite ore reduction. This accordingly illustrates why Cr₂0₃ formation during pre-oxidation has to be minimized, while Fe migration to the outside of the particles has to be maximized;

Figure 6: is a graph showing the effect of introducing CaC0₃ additives during pre- oxidation (CaC0₃ additive concentration (x-axis)) on the extent of chromite pre-reduction (y-axis) whereby the pre-oxidation temperature of the ore was at

1000X;

Figure 7: is a graph indicating the effect of CaC0₃ additives (CaC0₃ additive concentration (x-axis)) on the cured breaking strength of pre-reduced pellets (y-axis). In this case, the additive was added only prior to pre-reduction and un-oxidised ore was used during pre-reduction;

Figure 8: is a graph depicting the effect of chromite pre-oxidation in the presence of

CaC0₃ additives (CaC0₃ additive concentration (x-axis)) on the extent of chromite pre-reduction (y-axis) whereby the pre-oxidation temperature of the ore was at 1000°C;

Figure 9: is a graph indicating the effect of CaC0₃ additives in combination with pre- oxidation (CaC0₃ additive concentration in conjunction with pre-oxidation (x- axis)) on the cured breaking strength of pre-reduced pellets (y-axis) whereby the pre-oxidation temperature was at 1000°C; and

Figure 10: is a graph representing the specific electricity consumption (SEC) as a function of chromite pre-reduction level and feed material temperature (Niayesh and Fletcher, 1986).

The presently disclosed subject matter will now be described more fully hereinafter with reference to the accompanying Examples, in which representative embodiments are shown.

The presently disclosed subject matter can, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the embodiments to those skilled in the art.

DESCRIPTION OF THE INVENTION

Example 1 : Experimental data indicating enhanced (improved) chromite prereduction by employing the process of the instant invention

Base Case

A mixture consisting of 20.0 wt.% anthracite (fixed carbon content of 75%), 3.5 wt.% attapulgite clay and the remainder South African metallurgical grade chromite ore (Cr₂0₃ content of 45%) was milled such that the mixture comprised particles wherein 90% of such particles were smaller than 75pm (process step 1 , Figure 1 ). The milled mixture was thereafter pelletised (process step 2, Figure 1 ) according to a similar method as is described by Kleyhans et al. (2012). This pelletisation method ensures that the density, form and size of the agglomerates remain consistent thereby allowing mono- variance investigation of other process parameters.

Pre-reduction (solid state reduction of chromite) on the resulting uncured pellets (process step 3, Figure 1 ) was conducted in a tube furnace. Similarly to Kleyhans et al. (2012), a temperature profile simulating industrial process conditions was used. The temperature profile consisted of three segments, i.e. i) heating up from room temperature to 900°C over a period of 30 minutes, ii) heating up to 1300°C over 50 minutes, iii) and finally cooling to room temperature. This entire procedure was conducted in an inert atmosphere (N₂ gas) to ensure that pre-reduction (solid state reduction of chromite) was achieved by means of the reductant present in the mixture and not by means of external gaseous conditions. After being exposed to the foregoing conditions, the pre-reduction level of the chromite pellets was determined with a procedure described by Kleyhans et al. (2012).

Present Invention

Batches of as-received South African metallurgical grade chromite ore (45% Cr₂0₃) was pre- oxidised at temperatures ranging from 800 to 1 100°C in a camber furnace under normal atmospheric conditions, i.e. in air. This pre-oxidised ore was then used as feed material instead of as-recieved ore in a similar fasion as described above (Base Case) to formulate a mixture consisting of pre-oxidised ore, carbonaceous reducing agent and binder. Thereafter this mixture was milled, pelletised and pre-reduced as described above (Base Case). The effect of pre-oxidizlng unagglomerated chromite ore, in accordance with the process set forth in terms of the first aspect of the invention, prior to agglomeration and pre-reduction can be seen in Figure 2. As can be observed by the graph depicted in this Figure, prereduction is significantly improved when unagglomerated chromite ore is pre-oxidized prior to agglomeration and pre-reduction when compared to utilizing ore which had been subjected to pre-reduction as is described herein above (referred to as the "Base Case" in Figure 2).

From these results, it is clear that pre-oxidation, prior to agglomeration and pre-reduction, as carried out in terms of the present invention, improves the level of achievable chromite prereduction in the temperature range of from 800°C - 1 100°C.

It can further be seen that pre-oxidation, prior to agglomeration and pre-reduction, carried out at pre-oxidation temperatures above 1 100°C resulted in a decreased level of prereduction, if compared to the Base Case.

As indicated in Figure 2, the optimum pre-oxidation temperature for pre-oxidizing the unagglomerated chromite ore, prior to agglomeration and pre-reduction, for this specific ore is 1000°C. However, it will be appreciated that this temperature might vary, depending on the chemical composition of the ore body, which can vary substantially.

Explanation of the observed improved pre-reduction levels as a result of the process of the instant invention resides in the importance of controlling the pre-oxidation temperate in order to ensure that maximum migration of iron (Fe) to the surface of the chromite ore particles takes place whist minimum Cr₂0₃ formation takes place. This migration of iron can be clearly seen in Figure 3, where Fe has migrated to the surface of the chromite ore particles as a result of pre-oxidation. Figures 4A, 4B and 4C represent XRD spectra for un-oxidized chromite ore, chromite ore pre-oxidized at a temperature of 1000°C and chromite ore pre-oxidized at a temperature of 1400°C, respectively. Figure 4D represents the XRD peak list which Figures 4A, 4B and 4C are to be referenced against.

From these XRD spectra, it is to be observed that the additional peak in Figure 4C corresponds to Cr₂0₃. It can thus be seen that whilst un-oxidized chromite ore (as shown in Figure 4A) comprise no free Cr₂0₃ and chromite ore pre-oxidized at a temperature of 1000°C (Figure 4B) contains no free Cr₂0₃, chromite ore pre-oxidized at a temperature of 1400X (Figure 4C) contains free Cr₂0₃.

It is important to note that it is difficult to detect Fe oxides with XRD techniques since these oxides are relatively uncrystalline and accordingly Fe oxides are not represented in the XRD spectra in these Figures. According to thermodynamic calculations conducted (as shown in Figure 5), Fe oxides reduce significantly easier than chromite ore (FeCr₂0₄), whilst Cr₂0₃ reduces less easily than chromite ore (FeCr₂0₄). Accordingly, pre-oxidation of the unagglomerated chromite ore must therefore take place at a temperature sufficient to maximize Fe migration to the surface of the chromite ore particle (as is shown in Figure 3), but to limit Cr₂0₃ formation (as is seen in Figures 4A to 4D). Maximizing the migration of Fe to the surface of the chromite ore particles during pre-oxidation, prior to agglomeration and pre-reduction, leads to a substantial improvement in chromite pre-reduction of the agglomerated chromite pellets (as depicted in Figure 2).

Accordingly, at a temperature of from 800^'C to 1000^'C, a significant enhancement in chromite pre-reduction is achieved due to the finding that at this temperature range, Fe oxides are formed whilst at a temperature of above 1000^'C, a decreased improvement in pre-reduction is achieved owing to the finding that at temperatures above 1000 C Cr₂0₃ is also formed.

Example 2: Use of additives in conjunction with pre-oxidation to enhance prereduction

As discussed previously, the use of additives has been proposed to enhance chromite prereduction (solid state reduction of chromite) including, but not limited to, CaC0₃, NaCI, CaF₂, NaF-CaF₂, Na₂B₄0₇, NaF, Na₂C0₃, CaB₄0_7> B₂0₃, CaCI, Si0₂, Al₂0_3l K₂C0₃, Na₂0₂, CaO, MgO, Fe ,Cr and K₂0.

In this regard, the Inventors investigated the use of CaC0₃ as an additive during prereduction. CaC0₃ was selected because CaC0₃ is typically added as a flux into the currently applied smelting processes that operate on a basic slag (process step 7, Figure 1 ). In this way, CaC0₃ does not constitute a foreign material which is added to the smelting step (process step 7, Figure 1 ).

To test the effect of CaC0₃ as an additive on chromite pre-reduction, experiments similar to those described for the Base Case in Example 1 were conducted. The only difference was that CaC0₃ was added as an additive to the chromite ore during pre-reduction.

The experimental results are indicated in Figure 6. The "base case^'' once again represents the chromite pre-reduction level that could be achieved utilising ore whereby no additives have been used. The "avg pre-reduction utilising CaC0₃" data represents the chromite prereduction achieved with the use of CaC0₃ as an additive, added in different wt.% to the mixture in process step 1 (Figure 1 ). As can be seen from Figure 6, the addition of CaC0₃ has a positive effect on the extent of chromite pre-reduction, with higher addition levels resulting in improved/enhanced prereduction. Notwithstanding the fact that CaO/CaC0₃ addition is known to influence chromite pre-reduction positively, the industrial use of it and other additives have not yet been implemented on an industrial scale. Experimentally it was found that the addition of CaC0₃ adversely affected the breaking strength of the cured pellets, as is illustrated in Figure 7.

Sufficient breaking strength of the cured agglomerates is required to survive the feed systems used at industrial smelting furnaces. Excessive fines formation is detrimental to all the smelting processes, save for the DC arc furnace operations (process combination (IV) of Figure 1 ). The low breaking strength of these pellets could however be mitigated by the selection of an optimum clay binder (Kleynhans ef a/., 2012), however it is unlikely that this negative aspect can be totally mitigated. It is therefore unlikely that CaC0₃ addition, to enhance chromite pre-reduction, will be applied industrially to smelting operations that are sensitive to fines formation.

Example 3: Pre-oxidation of chromite ore in the presence of additives and the effects thereof on pre-reduction

In order to test the effect of pre-oxidation of chromite ore in the presence of CaC0₃ prior to pre-reduction (solid state reduction of chromite), experiments similar to those described in Example 1 were conducted. The only difference was that pre-oxidation of the ore took place in the presence of the CaC0₃ additive. As mentioned herein before, since a temperature of 1000°C has been established to be the optimum pre-oxidation temperature (Figure 2) for the specific ore utilised for purposes of the present invention, pre-oxidation of the chromite ore was carried out at this temperature, in the presence of different wt.% additions of CaC0₃. it will be appreciated that this experimental procedure is in contrast to that of the prior art's use of additives to improve chromite pre-reduction (Example 2), wherein the additives are typically added during process step 1 (Figure 1 ) or prior to process step 2 (Figure 1 ).

A similar mechanism as has been proposed herein before for enhanced pre-reduction by means of pre-oxidizing the chromite ore prior to agglomeration and pre-reduction, i.e. Fe migration to the surface of the chromite ore particles concomitant with little or no Cr₂0₃ formation (Example 1 ), is also proposed for the present Example demonstrating chromite pre-oxidation, in the presence of CaC0₃, prior to pre-reduction. However, it is believed that more pronounced Fe migration to the surface of the chromite ore particles is achieved due to the presence of the alkaline additive compound present during pre-oxidation.

Similar to the prior art presented in Example 2, which Example demonstrated the addition of CaCOj as an additive during pre-reduction, the breaking strength of the pre-reduced agglomerates formed from pre-oxidised ore in the presence of CaC0₃ was substantially weaker than the Base Case (i.e. where no additives and no pre-oxidation was carried out). These breaking strength results are shown in Figure 9. Due to the weak breaking strength of pre-reduced agglomerates formed with this process option, it can be expected that substantial fine material will form from these agglomerates. This process option would therefore not be suited to SAF operations, where fines would lead to the subsequent trapping of evolving process gasses. However, it is to be noted that this process option would be suited to DC arc furnace operations, since the breakdown of agglomerates is irrelevant in these operations, since an unlimited fraction of fines can be fed into DC arc furnaces. Example 4: Calculation of specific electricity consumption (SEC)

The Inventors have estimated that the SEC of SAF processes that will utilize pre-reduced pellets which are formed from pre-oxidized ore prior to agglomeration and pre-reduction, as set forth in accordance with the process of the instant invention (Example 1 ) will be approximately 9% lower than the currently applied processes.

This improvement is based on the assumption that a pre-reduction level of 45% is representative of the currently achieved industry pre-reduction level. Further, the predicted improved SEC calculation is based on data published by Niayesh and Fletcher (1986), as shown in Figure 10, which indicates how the SEC will vary as a function of chromite prereduction level and material feed temperature. In order to utilise the latent energy from the pre-reduction process, industrially produced pre-reduced pellets are fed immediately after exiting the pre-reduction process into SAFs. This relates to feed temperatures of approximately 1273K (1000°C). During the calculation applied for the prediction of improved SEC, the data reported at 300K by Niayesh and Fletcher (1986) has been used. The improved SEC envisaged to be achieved by the present invention is therefore a conservative estimate.

Using a similar approach as described above, it was calculated that a SEC improvement of at least 18% can be achieved if pre-reduced agglomerates prepared from chromite ore pre- oxidized in the presence of CaC0₃ are utilized (Example 3). Whilst this would not be particularly beneficial to SAF operations, owing to the reasons discussed herein above, this would be particularly advantageous with respect to DC arc furnace operations. Example 5: Possible Cr(VI) Formation

Albeit completely unintended, it is impossible to completely exclude oxygen from all high temperature ferrochromium production process steps (Figure 1 ), with the corresponding possibility arising for the generation of small amounts of Cr(VI) species (Beukes et al., 2010).

Certain Cr(VI) species are regarded as a carcinogenic, with specifically airborne exposure to these Cr(VI) species being associated with cancer of the respiratory system. It is therefore important to quantify the amount of Cr(VI) that could be formed by the application of the present invention.

To quantify Cr(VI) formation during pre-oxidation of chromite ore (as demonstrated in Example 1 ), several samples of South African metallurgical grade chromite ore were pre- oxidised in accordance with the process of the present invention in the temperature range from 800°C to 1400°C. These samples were leached with an alkaline buffer to extract all Cr(VI) species (Ashley et al., 2003; Petti ne et al., 2005) and analyzed with dedicated ion chromatography instrumentation (IC) (Thomas et al., 2002). The liquid concentrations were then converted to solid concentrations. The results indicated that 0.4 to 1 pg Cr(VI) per gram (pg/g or g/metric ton) of pre-oxidized chromite ore is formed during pre-oxidation in accordance with the process of the present invention. These Cr(VI) levels are substantially lower than the Cr(VI) content reported for typical ferrochrome furnace off-gas dust particles, i.e. 5 to 7000pg/g (g/metric ton) (Gericke, 1995).

One explanation for why the Cr(VI) levels in accordance with this Example are substantially lower than that reported in furnace off -gas is attributed to the fact that the metallurgical grade chromite ore is not milled prior to pre-oxidation, which thereby limits the surface area exposed to pre-oxidation. In addition hereto, milling prior to pre-oxidation would increase the risk of the Cr(VI) becoming airborne, which increases the risk of inhalation. As stated earlier, airborne exposure to Cr(VI) is associated with cancer of the respiratory system.

Utilizing a similar analytical procedure, Cr(VI) formation during chromite pre-oxidation in the presence of CaC0₃ as an additive was quantified. The results indicate that 30 to 36.5pg Cr(VI) per gram (pg/g or g/metric ton) could form if this process option is used.

Having described the invention in detail and by reference to the aspects and embodiments thereof, the scope of the present invention is not limited only to those described characteristics, aspects or embodiments. As will be apparent to persons skilled in the art, modifications, analogies, variations, derivatives and adaptations to the above-described invention can be made on the base of art-known knowledge and/or on the base of the disclosure (e.g. the explicit, implicit or inherent disclosure) of the present invention without departing from the spirit and scope of this invention.

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Claims

1. A process for the partial oxidation of chromite, said process including the steps consisting of:

(i) providing a source of unagglomerated chromite ore;

(ii) subjecting the source of unagglomerated chromite ore to pre-oxidation at a temperature of 700 C to 1 100^*C, both values inclusive;

(iv) forming a pre-oxidized source of unagglomerated chromite ore wherein maximum migration of iron (Fe) to the surface of the chromite ore particles takes place as well as minimum Cr₂0₃ formation takes place.

2. The process according to claim 1 , wherein the source of unagglomerated chromite ore is in the form of fine chromite ore.

3. The process according to claim 2, wherein the source of unagglomerated chromite ore is selected from the group consisting of metallurgical grade chromite ore, chemical grade chromite ore, UG2 chromite ore, milled chromite ore or a combination of two or more thereof from any deposit.

4. The process according to claim 1 , wherein pre-oxidation of the unagglomerated chromite ore takes place in air.

5. The process according to claim 1 or claim 4, wherein pre-oxidation is carried out at a temperature range of 800 C to 1000 (both values inclusive).

6. The process according to claim 5, wherein pre-oxidation takes place at a temperature of 1000^'C.

7. The process according to any one of the preceding claims, characterised in that when pre-oxidation of the unagglomerated chromite ore is carried out at a temperature of from 800^'C up to and including 1000^'C and where said process is employed prior to current commercial processes involving the pre-reduction of chromite (solid state reduction of chromite), a significant enhancement in pre-reduction of chromite is achieved.

8. The process according to claim 1 , wherein the resulting pre-oxidized source of unagglomerated chromite ore is used as a starting material for currently applied ferrochromium production processes used in the art.

9. The process according to claim 8, wherein said currently applied ferrochromium production processes involve pre-reduction of chromite (solid state reduction of chromite).

10. The process according to claim 8 or claim 9, wherein said ferrochromium production processes involve pre-reduction of chromite (solid state reduction of chromite) as is carried out in closed SAF operations, as is currently utilized by GlencoreXstrata Alloys in their Premus process.

1 1. The process according to any one of claims 8 to 10, wherein said processes involve DC arc furnace operations.

12. A process for enhancing the pre-reduction (solid state reduction) of chromite, said process including the steps consisting of:

(i) providing a source of unagglomerated chromite ore;

(vi) subjecting the chromite product of step (v) to milling or grinding;

(vii) agglomerating the milled or ground chromite product of step (vi);

13. The process according to claim 12, wherein the source of unagglomerated chromite ore is in the form of fine chromite ore.

14. The process according to claim 13, wherein the source of unagglomerated chromite ore is selected from the group consisting of metallurgical grade chromite ore, chemical grade chromite ore, UG2 chromite ore, milled chromite ore or a combination of two or more thereof from any deposit.

15. The process according to claim 12, wherein pre-oxidation of the unagglomerated chromite ore takes place in air.

16. The process according to claim 12 or claim 15, wherein pre-oxidation is carried out at a temperature range of 800^"C to 1000^'C (both values inclusive).

17. The process according to claim 16, wherein pre-oxidation takes place at a temperature of 1000^' C.

18. The process according to claim 12, wherein the reductant is selected from the group consisting of coke, coal, anthracite and char.

19. The process according to claim 12, wherein a clay binder is used.

20. The process according to claim 12, wherein agglomeration is achieved by either pelletizing or briquetting the milled or ground chromite product of step (vi).

21 . A process for enhancing the pre-reduction (solid state reduction) of chromite in the currently applied Premus (solid state reduction of chromite) operation applied by GlencoreXstrata Alloys, said process including the steps consisting of:

(i) providing a source of unagglomerated chromite ore;

(iii) controlling the pre-oxidation temperature such that maximum migration of iron (Fe) to the surface of the chromite ore particles takes place and minimum Cr₂0₃ formation takes place; (ίν) forming a pre-oxidized source of unagglomerated chromite ore wherein maximum migration of iron (Fe) to the surface of the chromite ore particles takes place and minimum Cr₂0₃ formation takes place; and

(v) introducing the pre-oxidized source of unagglomerated chromite ore as a feed material to said currently applied Premus operation.

22. The process according to claim 21 , wherein the source of unagglomerated chromite ore is in the form of fine chromite ore.

23. The process according to claim 22, wherein the source of unagglomerated chromite ore is selected from the group consisting of metallurgical grade chromite ore, chemical grade chromite ore, UG2 chromite ore, milled chromite ore or a combination of two or more thereof from any deposit.

24. The process according to claim 21 , wherein pre-oxidation of the unagglomerated chromite ore takes place in air.

25. The process according to claim 21 or claim 24, wherein pre-oxidation is carried out at a temperature range of 800 C to 1000 C (both values inclusive).

26. The process according to claim 25, wherein pre-oxidation takes place at a temperature of 1000^' C.

27. The process according to any one of claims 21 to 26, wherein a specific electricity consumption (SEC) reduction of approximately 9% is achieved.

28. A process for significantly improving specific electricity consumption (SEC) in currently applied ferrochromium production operations, said process including the steps consisting of:

(i) providing a source of unagglomerated chromite ore;

29. A process for significantly improving specific electricity consumption (SEC) in DC arc furnace operations, said process including the steps consisting of:

(i) providing a source of unagglomerated chromite ore;

(iv) forming a pre-oxidized source of unagglomerated chromite ore wherein maximum migration of iron (Fe) to the surface of the chromite ore particles takes place and minimum Cr₂0₃ formation takes place; and (v) introducing the pre-oxidized source of unagglomerated chromite ore to any suitable DC arc furnace operation.

30. A process for significantly improving specific electricity consumption (SEC), said process including the steps consisting of:

(i) providing a source of unagglomerated chromite ore;

(ii) providing an additive selected from the group consisting of, but not limited to, CaC0_3l CaO, and Ca(OH)₂;

(iii) subjecting the source of unagglomerated chromite ore to pre-oxidation in the presence of the additive at a temperature of 700 C to 1 100^*C, both values inclusive;

31 . The process according to any one of claims 28 to 30, wherein the source of unagglomerated chromite ore is in the form of fine chromite ore.

32. The process according to any one of claims 31 , wherein the source of unagglomerated chromite ore is selected from the group consisting of metallurgical grade chromite ore, chemical grade chromite ore, UG2 chromite ore, milled chromite ore or a combination of two or more thereof from any deposit.

33. The process according to any one of claims 28 to 30, wherein pre-oxidation of the unagglomerated chromite ore takes place in air.

34. The process according to any one of claims 28 to 30, wherein pre-oxidation is carried out at a temperature range of 800^" C to 1000^' C (both values inclusive).

35. The process according to any one of claims 34, wherein pre-oxidation takes place at a temperature of 1000^'C.

36. Use of the process according to claim 1.

37. Use of the process according to claim 12.

38. Use of the process according to claim 21.

39. Use of the process according to claim 28.

40. Use of the process according to claim 29.

41. Use of the process according to claim 30.

42. A product prepared in accordance with the process of claim 1 .

43. A product prepared in accordance with the process of claim 12.

44. A product prepared in accordance with the process of claim 21.

45. A product prepared in accordance with the process of claim 28.

46. A product prepared in accordance with the process of claim 29.

47. A product prepared in accordance with the process of claim 30.

48. The process according to any one of claims 1 , 12, 21 , 28, 29 or 30, substantially as herein described and exemplified, and/or described with reference to the accompanying figures.

49. The use according to any one of claims 36 to 41 , substantially as herein described and exemplified, and/or described with reference to the accompanying figures.

50. The product according to any one of claims 42 to 47, substantially as herein described and exemplified, and/or described with reference to the accompanying figures.