Claims:I/WE CLAIM:
1. A process for producing a low silicon ferrochrome comprising contacting ferrochrome with chrome ore to produce the low silicon ferrochrome.

2. The process of claim 1, wherein the ferrochrome is a hot metal produced in a furnace, and said hot metal is contacted with chrome ore to produce the low silicon ferrochrome.

3. The process of claim 1 or claim 2, wherein the hot metal is contacted with chrome ore outside the furnace to produce the low silicon ferrochrome.

4. The process of any of the preceding claims, wherein the hot metal is contacted with chrome ore in a ladle to produce the low silicon ferrochrome.

5. The process of any of the preceding claims, wherein the ladle is a hot metal tapping ladle.

6. The process of any of the preceding claims, wherein the chrome ore is chrome ore fines; and wherein the chrome ore fines are heated to a temperature of about 850? to 900? before contacting the chrome ore fines with the hot metal.

7. The process of any of the preceding claims, wherein the chrome ore is employed in an amount ranging from about 40 kg/thm (kilogram/ton-hot metal) to 60 kg/thm.

8. The process of any of the preceding claims, wherein the chrome ore fines are at a size of less than 6 mm.

9. The process of any of the preceding claims, wherein contacting the chrome ore with the hot metal creates a stirring reaction resulting in removal of silicon within a time-period of about 5 minutes.

10. The process of any of the preceding claims, wherein the low silicon ferrochrome is produced by reduction of chrome ore containing chromium(III) oxide (Cr2O3).

11. The process of any of the preceding claims, wherein the chrome ore (Cr2O3) acts as an oxidizing agent and removes silicon (Si) from the hot metal to produce the low silicon ferrochrome and a silicon dioxide (SiO2) rich slag.

12. The process of any of the preceding claims, wherein chromium (Cr) content of the hot metal is enhanced due to the reduction of the chrome ore, thereby leading to the production of high chromium containing low silicon ferrochrome.

13. The process of any of the preceding claims, wherein said process comprises:
adding chrome ore fines in a ladle;
tapping hot metal in the ladle wherein said hot metal falling in the ladle comes in contact with the chrome ore fines to produce low silicon ferrochrome and SiO2 rich slag.

14. The process of any of the preceding claims, wherein said process comprises:
screening chrome ore fines to a size less than 6 mm and heating the screened chrome ore fines to a temperature ranging from about 850? to 900?;
adding the chrome ore fines in a ladle; and
contacting the hot metal produced in a furnace with the chrome ore fines in the ladle to produce low silicon ferrochrome and SiO2 rich slag.

15. The process of any of the preceding claims, wherein the low silicon ferrochrome comprises silicon (Si) at about 1.9% to 2%, chromium (Cr) at about 63% to 63.5%, iron (Fe) at about 26% to 26.5%, carbon (C) at about 7.5.% to 8.5%, and phosphorous (P), sulphur (S) and manganese (Mn) each at about 0.5%.

16. A process of desiliconization of metal during production of ferrochrome, the process comprising contacting the metal with chrome ore to desiliconize the metal.

17. The process of claim 16, wherein the metal is a hot metal containing ferrochrome and the chrome ore is chrome ore fines.

18. The process of claim 16 or 17, wherein the process comprises reduction of chrome ore (Cr2O3); and wherein said chrome ore acts as an oxidizing agent and removes silicon (Si) from the hot metal to produce a low silicon ferrochrome and a SiO2 rich slag.

19. A low silicon ferrochrome, obtained by the process of any of the preceding claims, wherein the low silicon ferrochrome comprises silicon (Si) at about 1.9% to 2%, chromium (Cr) at about 63% to 63.5%, iron (Fe) at about 26% to 26.5%, carbon (C) at about 7.5.% to 8.5%, and phosphorous (P), sulphur (S) and manganese (Mn) each at about 0.5%.

20. Use of chrome ore as a desiliconizing agent during production of ferrochrome.
, Description:TECHNICAL FIELD
The present disclosure is in the field of metallurgy, more particularly towards ferrochrome production. The present disclosure provides a simple, single-step and economical method of producing premium grade low silicon ferrochrome through external desiliconization.

BACKGROUND OF THE DISCLOSURE
Ferrochrome is a ferroalloy which has significant applications including utilisation in the production of stainless steel. However, silicon (Si) content in ferrochrome is detrimental as it increases the Si input in steel making resulting in higher Si in steel, thereby degrading the mechanical properties of steel. Accordingly, various methods have been employed in the past to produce low Si ferrochrome by means such as controlling basicity inside the furnace, distribution of silica flux in the furnace, reducing silica input in raw material and refining the hot metal through oxygen.

However, the existing routes for low Si ferrochrome production as discussed above, have at least the following limitations:
- operating at high basicity is difficult in furnace such as AC Submerged Arc Furnace (SAF) due to change in slag conductivity which effects the furnace operation.
- distribution of silica flux outside the high temperature zone in the furnace could decrease metal Si theoretically. However, it is practically challenging to control the silica distribution due to burden profile inside the furnace.
- while silica input in raw material can be reduced through selection and beneficiation, it is naturally limited by the source.
- by external refining of hot metal ferrochrome through oxygen purging, it is difficult to obtain significant reduction in silicon without losing on metal yield. Also, said method is not economical and increases the overall production costs.

Thus, the existing state of the art techniques for low silicon ferrochrome production require certain prerequisites and have limitations. Hence, there is a need for a simple, economical and efficient method for low silicon ferrochrome production and a corresponding low silicon ferrochrome product thereof, especially which is independent of the parameters of ferrochrome production inside the furnace.

STATEMENT OF THE DISCLOSURE
The present disclosure relates to a process for producing a low silicon ferrochrome comprising contacting ferrochrome with chrome ore to produce the low silicon ferrochrome.

The present disclosure further relates to a process of desiliconization of metal during production of ferrochrome, the process comprising contacting the metal with chrome ore to desiliconize the metal.

The present disclosure also provides a low silicon ferrochrome, obtained by the process described above, wherein the low silicon ferrochrome comprises silicon (Si) at about 1.9% to 2%, chromium (Cr) at about 63% to 63.5%, iron (Fe) at about 26% to 26.5%, carbon (C) at about 7.5.% to 8.5%, and phosphorous (P), sulphur (S) and manganese (Mn) each at about 0.5%.

The present disclosure further relates to the use of chrome ore as a desiliconizing agent during production of ferrochrome.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1 depicts a pictorial representation of an exemplary embodiment of the present method of low silicon ferrochrome production.

DETAILED DESCRIPTION OF THE DISCLOSURE
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results. Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising” or “containing” or “has” or “having” wherever used, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

As used herein, the phrase ‘hot metal’, ‘hot metal ferrochrome’ or ‘hot metal containing ferrochrome’ refers to the ferrochrome alloy produced by conventional or existing means/methods. In an embodiment, ferrochrome is produced by carbothermic reduction at high temperatures wherein Cr Ore (an oxide of chromium and iron) is reduced by coal and coke to produce the hot metal ferrochrome. In another embodiment, the ferrochrome is produced in a Submerged Arc Furnace (SAF).

As used herein, the phrase ‘low silicon ferrochrome’, ‘low Si ferrochrome’, or ‘premium grade low Si ferrochrome’ refers to the product of the present disclosure containing lower levels/amounts of silicon and higher chromium content compared to the hot metal ferrochrome produced in a furnace.

The present disclosure is in relation to ferrochrome production, more particularly low silicon ferrochrome production.

An objective of the present disclosure is to develop a simple, economical and efficient process of producing a low silicon ferrochrome.

Another objective of the present disclosure is to provide a simple, economical and efficient process of removing or reducing silicon levels in ferrochrome, said process being independent of the parameters of ferrochrome production inside the furnace.

Yet another objective of the present disclosure is to provide a simple, economical and efficient process of removing or reducing silicon levels in ferrochrome externally i.e. outside the furnace.

Accordingly, the present disclosure provides a single-step process for producing low silicon ferrochrome comprising contacting ferrochrome with chrome ore to produce the low silicon ferrochrome.

In an embodiment of the present process, ferrochrome is the hot metal produced in a furnace, and said hot metal is contacted with chrome ore to produce the low silicon ferrochrome.

In another embodiment of the present process, the hot metal ferrochrome is contacted with chrome ore outside the furnace to produce the low silicon ferrochrome.

In yet another embodiment of the present process, the hot metal ferrochrome is contacted with chrome ore in a ladle to produce the low silicon ferrochrome.

In still embodiment of the present process, the ladle is a hot metal tapping ladle.

Thus, the present disclosure particularly provides a process for producing low silicon ferrochrome comprising contacting hot metal ferrochrome with chrome ore outside the furnace to produce a low silicon ferrochrome product. In a preferred embodiment of the present process, the hot metal ferrochrome produced in the furnace is contacted with chrome ore in a hot metal tapping ladle outside the furnace to produce the low silicon ferrochrome.

In an embodiment of the present process, the chrome ore is chrome ore fines (solid fines).

In an exemplary embodiment of the present process, the chrome ore fines at a size of less than 6 mm is employed in the process of producing the low silicon ferrochrome.

In another embodiment of the present process, the chrome ore fines are preheated to a temperature of about 850 ? to 900 ? before contacting said chrome ore fines with the hot metal.

In an exemplary embodiment of the present process, the chrome ore fines are preheated to a temperature of about 900? before reacting said chrome ore fines with the hot metal.

In an embodiment of the present process, the chrome ore is employed in an amount ranging from about 40 kg/thm (kilogram/ton-hot metal) to 60 kg/thm.

In preferred embodiments of the present process, the chrome ore is employed in an amount ranging from about 40 kg/thm (kilogram/ton-hot metal), 45 kg/thm, 50 kg/thm, 55 kg/thm, or 40 kg/thm.

In exemplary embodiments of the present process, the chrome ore is employed in an amount ranging from about 40 kg/thm (kilogram/ton-hot metal), 41 kg/thm, 42 kg/thm, 43 kg/thm, 44 kg/thm, 45 kg/thm, 46 kg/thm, 47 kg/thm, 48 kg/thm, 49 kg/thm, 50 kg/thm, 51 kg/thm, 52 kg/thm, 53 kg/thm, 54 kg/thm, 55 kg/thm, 56 kg/thm, 57 kg/thm, 58 kg/thm, 59 kg/thm, or 60 kg/thm.

In a more preferred embodiment of the present process, the chrome ore is employed in an amount of about 45 kg/thm.

In another embodiment of the present process, contacting the chrome ore with the hot metal creates a stirring reaction resulting in removal of silicon.

In yet another embodiment of the present process, contacting the chrome ore with the hot metal results in removal of silicon in about 5 minutes.

In still another embodiment of the present process, the low silicon ferrochrome is produced due to reduction of chrome ore containing chromium(III) oxide (Cr2O3).

In still another embodiment of the present process, the chrome ore (Cr2O3) acts as an oxidizing agent and removes silicon (Si) from the hot metal to produce the low silicon ferrochrome and a silicon dioxide (SiO2) rich slag.

In an exemplary embodiment of the present process, chromium (Cr) content of the hot metal is enhanced due to the reduction of the chrome ore, thereby leading to the production of high chromium containing low silicon ferrochrome product.

In an exemplary embodiment of the present disclosure, the process for producing low silicon ferrochrome comprises:
a) adding chrome ore fines in a ladle;
b) tapping hot metal in the ladle, wherein said hot metal falling in the ladle comes in contact with the chrome ore fines to produce low silicon ferrochrome and SiO2 rich slag.

In another exemplary embodiment of the present disclosure, the process for producing low silicon ferrochrome comprises:
a) screening chrome ore fines to a size less than 6 mm and heating the screened chrome ore fines to a temperature ranging from about 850? to 900?;
b) adding the chrome ore fines in a ladle; and
c) contacting the hot metal produced in a furnace with the chrome ore fines in the ladle to produce low silicon ferrochrome and SiO2 rich slag.

In yet another exemplary embodiment of the present disclosure, the process for producing low silicon ferrochrome comprises:
a) screening chrome ore fines to a size less than 6 mm and heating the screened chrome ore fines to a temperature of about 900?;
b) adding the chrome ore fines in an amount ranging from about 40 kg/thm to 60 kg/thm in a hot metal tapping ladle; and
c) contacting the hot metal ferrochrome produced in a furnace with the chrome ore fines in the ladle to produce low silicon ferrochrome and SiO2 rich slag.

In a preferred embodiment of the present disclosure, the process for producing low silicon ferrochrome comprises:
a) screening chrome ore fines to a size of < 6mm and heating the chrome ore fines to a temperature of about 900? to ensure removal of moisture and to compensate heat loss due to chrome ore fines melting;
b) weighing chrome ore fines in an amount ranging from about 40 kg/thm to 60 kg/thm and adding the chrome ore fines in the empty ladle;
c) taking the ladle containing chrome ore fines for tapping of the hot metal ferrochrome; and
d) tapping the hot metal in the ladle containing chrome ore fines wherein the Si removal/reduction reaction takes place in about 5 minutes resulting in the production of low silicon ferrochrome.

In an embodiment of the present process, chrome ore fines are added in an amount ranging from about 40 kg/thm to 60 kg/thm depending on the silicon (Si) level in the hot metal ferrochrome. In an exemplary embodiment, the Si level in the hot metal is estimated based on Si prediction model.

In another embodiment of the present process, the hot metal sample is taken before pouring in the ladle and during casting (i.e. post reduction reaction with chrome ore) for analysing the chemical composition.

In yet another embodiment of the present process, slag sample is also taken from the ladle during tapping of the hot metal to interpret the efficiency of Si reduction.

In an exemplary embodiment of the present process, the reaction efficiency of the present process of producing low silicon ferrochrome ranges from about 30% to 80%.

In another embodiment of the present process, the low silicon ferrochrome produced by the present method comprises silicon (Si) at about 1.9% to 2%, chromium (Cr) at about 63% to 63.5%, iron (Fe) at about 26% to 26.5%, carbon (C) at about 7.5.% to 8.5%, and phosphorous (P), sulphur (S) and manganese (Mn) each at about 0.5%. Said low silicon ferrochrome may further comprise one or more additional elements/components to make up the final composition of the low silicon ferrochrome to 100 wt%.

The present disclosure further describes a process of desiliconization of hot metal ferrochrome, said process comprising contacting the hot metal ferrochrome with chrome ore to desiliconize the hot metal ferrochrome.

In an embodiment, the chrome ore employed in the process of desiliconization is chrome ore fines.

In another embodiment, the above described process of desiliconization comprises reduction of chrome ore (Cr2O3). In an embodiment, said chrome ore acts as an oxidizing agent and removes silicon (Si) from the hot metal ferrochrome to produce low silicon ferrochrome and a SiO2 rich slag.

In yet another embodiment, the above described process of desiliconization comprises tapping the hot metal in a ladle containing chrome ore fines, wherein the desiliconization reaction (i.e. Si removal/reduction) takes place in about 5 minutes resulting in the production of low silicon ferrochrome.

The present disclosure also relates to a low silicon ferrochrome product obtained by the processes described above, wherein the low silicon ferrochrome comprises silicon (Si) at about 1.9% to 2%, chromium (Cr) at about 63% to 63.5%, iron (Fe) at about 26% to 26.5%, carbon (C) at about 7.5.% to 8.5%, and phosphorous (P), sulphur (S) and manganese (Mn) each at about 0.5%. Said low silicon ferrochrome may further comprise one or more additional elements/components to make up the final composition of the low silicon ferrochrome to 100 wt%.

The present disclosure also describes the use of chrome ore as a desiliconizing agent during production of ferrochrome to produce a low silicon ferrochrome product.

Thus, the present disclosure relates to a simple single-step process of employing chrome ore/chrome ore fines as an oxidizing agent to remove Si from the hot metal ferrochrome. In particular, the chrome ore fines are comparatively a cheaper source of oxygen, and therefore there is not much increase in cost of production, thereby making the overall process economical. Also, the chromium content of the hot metal ferrochrome increases due to the reduction of chrome ore fines. Therefore, premium of the final product increases due to decrease in its silicon content as well as an increase in its chromium content.

In particular, the present process comprises adding chrome ore fines in the hot metal tapping ladle before the ladle is introduced for tapping. Hot metal falling in the ladle encounters the chrome ore fines and creates a stirring action enabling the desiliconization reaction. Si having greater affinity towards oxygen compared to Cr, extracts oxygen from Cr2O3 forming SiO2 and gets separated from metal phase as slag. This slag (SiO2) being lighter, rises and floats over the metal surface which can be separated before the liquid metal is subjected to casting.

In an exemplary embodiment, the present process of producing low silicon ferrochrome is carried out between the steps of collecting hot metal ferrochrome from furnace and pouring the same into casting pits. In particular, the chrome ore fines after screening are preheated and kept in the hot ladle before the ladle is introduced for tapping. Hot metal falling in the ladle encounters the ore fines and creates stirring action enabling the desiliconization reaction to produce a low silicon and high chromium ferrochrome alloy product.

The present invention primarily comprising the process of desiliconization and production of low silicon ferrochrome, and the corresponding product possesses at least the following advantages:
a) the process is carried outside the furnace,
b) the process employs chrome ore/chrome ore fines as the lone oxidizing agent,
c) the process is a simple single-step process comprising chrome ore/chrome ore fines addition for silicon removal in ferrochrome, and
d) employing chrome ore/chrome ore fines for reducing Si content in ferrochrome makes the overall process more economical when compared to the existing methods which primarily focus on controlling conditions/parameters inside the furnace.

In an embodiment, the foregoing descriptive matter is illustrative of the disclosure and not a limitation. While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. Those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

EXAMPLES

EXAMPLE 1: Production of low silicon ferrochrome Si reduction by employing chrome ore fines at about 45 kg/thm
Screened (< 6mm) chrome ore fines were preheated at about 900? to ensure removal of moisture and to compensate heat loss due to ore fines melting. In particular, preheating of chrome ore fines provide extra energy to molten bath to make reaction kinetics faster.

Chrome ore fines were weighed at 45kg/thm and added in the empty ladle based on about 2.6% Si level in hot metal ferrochrome (estimated from Si prediction model). This ladle with chrome ore fines was taken for tapping of hot metal. Metal was tapped in the ladle containing chrome ore fines and Si reduction reaction took place. The hot metal sample was taken before pouring in the ladle and during casting (i.e. after chrome ore reduction reaction) for chemical analysis of the composition. Si level in the final product (low silicon ferrochrome) was reported as 2.06%. Also, Cr % of the final product improved from 60 to 61.9%.

EXAMPLE 2: Production of low silicon ferrochrome Si reduction by employing chrome ore fines at about 50 kg/thm
Screened (< 6mm) chrome ore fines were preheated at about 900? to ensure removal of moisture and to compensate heat loss due to ore fines melting. Chrome ore fines were weighed at 50 kg/thm and added in the empty ladle based on about 2.43% Si level in hot metal ferrochrome (estimated from Si prediction model). This ladle with chrome ore fines was taken for tapping of hot metal. Metal was tapped in the ladle containing chrome ore fines and Si reduction reaction took place. The hot metal sample was taken before pouring in the ladle and during casting (i.e. after chrome ore reduction reaction) for chemical analysis of the composition. Si level in the final product (low silicon ferrochrome) was reported as 1.98%. Also, Cr % of the final product improved from 60.7 to 61.1%.

EXAMPLE 3: Production of low silicon ferrochrome Si reduction by employing chrome ore fines at about 55 kg/thm
Screened (< 6mm) chrome ore fines were preheated at about 900? to ensure removal of moisture and to compensate heat loss due to ore fines melting. Chrome ore fines were weighed at 50 kg/thm and added in the empty ladle based on about 2.52% Si level in hot metal ferrochrome (estimated from Si prediction model). This ladle with chrome ore fines was taken for tapping of hot metal. Metal was tapped in the ladle containing chrome ore fines and Si reduction reaction took place. The hot metal sample was taken before pouring in the ladle and during casting (i.e. after chrome ore reduction reaction) for chemical analysis of the composition. Si level in the final product (low silicon ferrochrome) was reported as 2.23%. Also, Cr % of the final product improved from 60.3 to 60.7%.

The results of employing chrome ore fines on reduction of Si level and reaction efficiency are provided in Table 1 below.

Table 1: Results of silicon (Si) drop by employing chrome ore fines
Wt. of fines added (kg/thm) Grade of chrome ore fines (%Cr2O3) Cr2O3 input (kg/thm) Reaction Efficiency Metal %Si Metal %Cr
Initial %Si Final %Si ?%Si actual ?%Si theoretical Initial %Cr Final %Cr ?%Cr actual ?%Cr theoretical
45 53 23.8 80 2.6 2.06 0.54 0.66 60 61.9 1.9 1.64
50 52 26.0 50 2.43 1.98 0.45 0.84 60.7 61.1 0.38 1.76
55 52 28.6 30 2.52 2.23 0.29 0.93 60.3 60.7 0.36 1.94

The above results confirm the production of low silicon ferrochrome by employing chrome ore fines as the sole silicon removal agent. These experimental results demonstrate that with external addition of chrome ore fines (solid fines), there is a drop in silicon levels (varying between 0.29 % to 0.54 %) in the final ferrochrome product.

The final Si % in ferrochrome will depend on input Si % of the hot metal and was estimated based on average data of last 3 tappings of the same day. Further, the quantity of chrome ore fines may vary from about 40 to 60 kg/thm, preferably 45 to 55 kg/thm leading to reaction efficiency between 30 to 80%. More particularly, the highest reaction efficiency of about 80% was observed for 45 kg/thm. Further, the final Cr % in the ferrochrome also depends on quantity of chrome ore addition wherein the quantum increase in Cr % varied from 0.36 % to 1.9 %.

The aforesaid results indicating Si removal/reduction and simultaneous increase in Cr content is significant in terms of achieving premium grade low silicon ferrochrome product, and has immense positive impact/advantages on the employment of said product in steel making process.

The present disclosure is thus successful in providing a simple, economical and efficient process of producing premium grade low silicon ferrochrome through external desiliconization by employing chrome ore fines as the lone silica removal agent. preparing effective calcium ferrite from iron and calcium oxide containing materials. The produced ferrochrome product is immensely advantageous, especially in applications related to steel making.