Claims:I/WE CLAIM:
1. A process for preparing calcium ferrite, comprising:
mixing an iron source, a calcium oxide source, a binder, a carbon containing material and water to prepare a mixture,
sintering the mixture to prepare the calcium ferrite,
wherein, particle size of the iron source is about 0.5 mm to 10 mm and particle size of the calcium oxide source is about 0.6 mm to 4 mm.

2. The process of claim 1, wherein the iron source is iron oxide selected from a group comprising iron ore, mill scale, steel making fume dust, iron oxide from acid regeneration plant and combinations thereof.

3. The process of claim 1, wherein the calcium oxide source is selected from a group comprising limestone, calcite, calcined lime, quick lime and combinations thereof.

4. The process of claim 1, wherein the binder is selected from a group comprising lime powder, bentonite, dextrin, starch, cellulose and combinations thereof.

5. The process of claim 1, wherein the carbon containing material is a fuel source, and said carbon containing material is selected from a group comprising anthracite coal, metallurgical coke, metallurgical coke breeze and combinations thereof.

6. The process of claim 1 or claim 2, wherein the particle size of the iron source is about 0.6 mm to 10 mm, preferably about 6 mm, 8 mm, or 10 mm.

7. The process of claim 1, wherein the particle size of the calcium oxide source is about 0.6 mm to 3.15 mm, preferably about 0.6 mm, 3.15 mm, or 3.15 mm.

8. The process of claim 1, wherein particle size of the binder is about 25 µm to 150 µm, preferably about 45 µm, 75 µm, or 150 µm.

9. The process of claim 1, wherein particle size of the carbon containing material is about 0.15 mm to 4 mm, preferably about 0.15 mm, 0.25 mm, or 3.15 mm.

10. The process of claim 1, wherein the water is added at about 6 wt% to 8 wt% of the total mixture, preferably about 6.5 wt% to 7.5 wt%.

11. The process of claim 1 or claim 2, wherein the iron source is added at a concentration of about 40 wt% to 50 wt% of the total mixture.

12. The process of claim 1, wherein the calcium oxide source is added at a concentration of about 40 wt% to 50 wt% of the total mixture.

13. The process of claim 1, wherein the binder is added at a concentration of about 2 wt% to 8 wt% of the total mixture.

14. The process of claim 1, the carbon containing material is added at a concentration of about 4 wt% to 8 wt% of the total mixture.

15. The process of any of the preceding claims, wherein the iron ore has a composition comprising Fe(t) at a wt% of about 63.76, silicon dioxide (SiO2) at a wt% of about 2.41, calcium oxide (CaO) at a wt% of about 0.41, magnesium oxide (MgO) at a wt% of about 0.061, aluminum oxide (Al2O3) at a wt% of about 2.71, titanium dioxide (TiO2) at a wt% of about 0.165, and sulphur (S) at a wt% of about 0.003.

16. The process of any of the preceding claims, wherein the mill scale has a composition comprising Fe(t) at a wt% of about 72.12, SiO2 at a wt% of about 0.55, CaO at a wt% of about 0.62, MgO at a wt% of about 0.022, TiO2 at a wt% of about 0.01, and S at a wt% of about 0.006.

17. The process of claim 1, wherein the mixture is a granulated mixture; and wherein the mixing of the iron source, the calcium oxide source, the binder, the carbon containing material and the water is carried out in a mixing drum or granulation drum to prepare the granulated mixture.

18. The process of claim 1 or claim 2, wherein the sintering step comprises charging, igniting and burning of the mixture in a sintering machine to react the calcium oxide and the iron oxide to form a hot sintered calcium ferrite cake.

19. The process of claim 18, wherein the sintering machine is selected from a group comprising Dwight-Lloyd sintering machine, stationary sinter pot, pan sintering setup, and combinations thereof.

20. The process of any of the preceding claims, wherein the sintering step to obtain the hot sintered calcium ferrite cake is carried out at a temperature of about 1100 oC to 1350 oC and for a time-period of about 20 minutes to 60 minutes.

21. The process of claim 1 or claim 18, wherein the process further comprises cooling the hot sintered calcium ferrite cake, crushing the cake and screening the crushed cake to obtain a calcium ferrite sinter in a size ranging from about 10 mm to 40 mm.

22. The process of any of the preceding claims, wherein the prepared calcium ferrite comprises calcium oxide at a concentration of about 25 wt% to 45 wt% and iron oxide at a concentration of about 40 wt% to 60 wt%; and wherein said calcium ferrite comprises a calcium ferrite phase of about 50% to 65%, a hematite phase of about 15% to 20%, a magnetite phase of about 1% to 3%, a slag melt phase of about 3% to 5%, and pores of about 15% to 30%.

23. The process of any of the preceding claims, wherein the calcium ferrite has an acicular needle like microstructure, possesses enhanced strength and quickly reacts with hot metal during steel making process.

24. The process of any of the preceding claims, wherein the calcium ferrite possesses a handling strength, expressed as Tumbler Index, of about 65% to 80% (+6.3mm); and Abrasion Index (-0.5mm) of about 3 % to 7.5 %.

25. The process of any of the preceding claims, wherein the calcium ferrite exhibits a low temperature melting behavior, expressed as flow temperature, in a temperature range of about 1200 oC to 1250 oC.

26. The process of any of the preceding claims, wherein the process comprises:
(d) mixing iron source having a particle size of about 0.5 mm to 10 mm at a concentration of about 40 wt% to 50 wt%, calcium oxide source having a particle size of about 0.6 mm to 3.15 mm at a concentration of about 40 wt% to 50 wt%, lime powder at a concentration of about 2 wt% to 4 wt%, coke breeze at a concentration of about 4 wt% to 8 wt% and water at about 6 wt% to 8 wt% to prepare a granulated mixture;
(e) charging, igniting and burning the granulated mixture in a sintering machine at a temperature of about 1100 oC to 1350 oC for a time-period of about 20 minutes to 60 minutes to produce the hot sintered calcium ferrite cake; and
(f) cooling the hot sintered calcium ferrite cake, crushing the cake and screening the crushed cake to obtain calcium ferrite sinter in the size of about 10 mm to 40 mm.

27. Calcium ferrite, obtained by the process of any of the preceding claims, wherein the calcium ferrite comprises a calcium ferrite phase of about 50% to 65%, a hematite phase of about 15% to 20%, a magnetite phase of about 1% to 3%, a slag melt phase of about 3% to 5%, and pores of about 15% to 30%, and wherein the calcium ferrite possesses an acicular needle like microstructure structure.

28. The calcium ferrite of claim 27, wherein the calcium ferrite comprises calcium oxide at a concentration of about 25 wt% to 45 wt% and iron oxide at a concentration of about 40 wt% to 60 wt%.

29. The calcium ferrite of claim 27, wherein said calcium ferrite comprises Fe(t) at a concentration of about 35 wt% to 45 wt%, FeO at a concentration of about 8 wt% to 11 wt%, CaO at a concentration of about 25 wt% to 45 wt%, SiO2 at a concentration of about 2 wt% to 7 wt%, MgO at a concentration of about 1 wt% to 3 wt%, Al2O3 at a concentration of about 1 wt% to 3 wt%, and phosphorous (P) at a concentration of about 0.05 wt% to 0.4 wt%.

30. The calcium ferrite of claim 27, wherein said calcium ferrite possesses a handling strength, expressed as Tumbler Index, of about 65% to 80% (+6.3mm), an Abrasion Index (-0.5mm) of about 3 % to 7.5 %, and exhibits a low temperature melting behavior, expressed as flow temperature, in the temperature range of about 1200oC to 1250oC.

31. A process of dephosphorization of metal during production of steel, the process comprising reacting the calcium ferrite defined in any of the preceding claims with the metal to obtain dephosphorized metal and phosphorous rich slag.

32. The process of claim 31, wherein the calcium ferrite comprises a calcium ferrite phase of about 50% to 65%, a hematite phase of about 15% to 20%, a magnetite phase of about 1% to 3%, a slag melt phase of about 3% to 5%, and pores of about 15% to 30%; and wherein the calcium ferrite comprises calcium oxide at a concentration of about 25 wt% to 45 wt% and iron oxide at a concentration of about 40 wt% to 60 wt%.

33. The process of claim 31, wherein the metal is hot metal; and wherein the calcium oxide from the calcium ferrite increases the dephosphorization rate.

34. The process of any of claims 31 to 33, wherein the calcium ferrite possesses high handling strength to withstand handling loads and exhibits a low temperature melting behavior, expressed as flow temperature, in a temperature range of about 1200 oC to 1250 oC enabling quick reaction with the metal to remove phosphorous during the production of steel.

35. Use of the calcium ferrite defined in any of the preceding claims as a dephosphorization agent during production of steel.

36. The use of claim 35, wherein the calcium ferrite removes phosphorous from metal during the production of steel resulting in manufacture of low phosphorous steel.
, Description:TECHNICAL FIELD
The present disclosure is in the field of metallurgy, more particularly towards calcium ferrite production. The present disclosure provides a simple, economical and efficient method of producing calcium ferrite from iron and calcium oxide containing materials.

BACKGROUND OF THE DISCLOSURE
During steel making in basic oxygen furnace converter process, lime (CaO) is used as the basic oxide that serves as a flux to remove unwanted impurities such as silica, sulphur and phosphorous. The lime is often added as calcined lime because it quickly reacts with the impurities during the oxygen blowing period. In particular, to remove phosphorous from the hot metal during steel making (i.e. dephosphorisation), reaction of the lime with phosphorous should be very fast and must occur in the initial stages of blowing process where the temperature of the hot metal is not very high in order to enable more phosphorous retention in the CaO rich slag. Thus, if the reaction rate between CaO and phosphorous could be increased, then dephosphorisation rate is also increased and the overall steel making process time is decreased.

From earlier studies, it was found that addition of CaO in the form of calcium ferrite increases the dephosphorisation rate as compared to calcined lime. There have been several studies in the past to produce calcium ferrite using different raw materials and different heating methods.

As per US patent US3649248A - “Process for producing a calcium ferrite for making steels”, iron ore powder and limestone powder are mixed to prepare pellets which are fired in rotary kiln at a temperature range of 1200 oC to 1250oC in the presence of limestone or lime powder sprinkled on the surface of the pellets to eliminate sticking together. However, this process needs both iron ore and limestone in the finer size fractions that needs huge amount of energy to fine grind them in grinding mills. The strength of calcium ferrite pellets produced through this process was also not mentioned in this document, which is one of the very important parameter while storing, handling and charging calcium ferrite into a steel making furnace.

As per US patent US3313617A - “Iron-containing flux material for steel-making process”, iron ore powder, limestone powder and carbon bearing material powder pellet are fired into traveling grate indurating machine at a temperature up to 1200oC. However, this process also needs all the ingredients used in the pellet making process to be in the finer size fractions which needs huge amount of energy to fine grind them in grinding mills.

Calcium ferrite prepared through above mentioned techniques therefore suffers from the following major disadvantages:
• all the raw materials used in the above techniques need to be in a very finer size fractions, for example, between 5 micron to 100-micron (about 0.005 mm to 0.1 mm) size range, which means that more energy is required for grinding and also more dust pollution occurs during grinding;
• large quantity of water needs to be added, for example, about 10% to 14% water, to the raw materials to prepare pellets of 5 mm to 13 mm size, which means that more energy is required to remove the water during drying and firing operations.

Therefore, there is an immense need to develop a simple, economical, energy-efficient and pollution free method to produce calcium ferrite, particularly for applications such as its use as a phosphorous removing agent during steel making process.

STATEMENT OF THE DISCLOSURE
The present disclosure relates to a process for preparing calcium ferrite, comprising:
mixing an iron source, a calcium oxide source, a binder, a carbon containing material and water to prepare a mixture,
sintering the mixture to prepare the calcium ferrite,
wherein, particle size of the iron source is about 0.5 mm to 10 mm and particle size of the calcium oxide source is about 0.6 mm to 4 mm.

The present disclosure further relates to a process of dephosphorization of metal during production of steel, said process comprising reacting the calcium ferrite prepared above, with the metal to obtain dephosphorized metal and phosphorous rich slag.

The present disclosure further relates to use of the calcium ferrite described above as a dephosphorization agent during production of steel.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1 depicts optical microstructure of calcium ferrite sinter produced by the present method (Example 2).
Figure 2 depicts scanning electron microstructure of calcium ferrite sinter produced by the present method (Example 2).
Figure 3 depicts the optical dilatometry image of calcium ferrite sinter produced by the present method (Example 2).
Figure 4 depicts optical microstructure of calcium ferrite sinter produced by the present method (Example 1).
Figure 5 depicts scanning electron microstructure of calcium ferrite sinter produced by the present method (Example 1).
Figure 6 depicts the optical dilatometry image of calcium ferrite sinter produced by the present method (Example 1).

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 phrases ‘calcium ferrite’ or ‘calcium ferrite sinter’ or ‘hot sintered calcium ferrite cake’ refer to calcium ferrite particles comprising sintered calcium ferrite phase with needle like morphology, hematite phase, magnetite phase, slag melt phase and pores.

As used herein, the phrase ‘sintering’ refers to a process of compacting and forming a solid mass of constituents/mixture as described herein by burning/applying heat below the melting point of said constituents.

As used herein, the phrase ‘particle size’ refers to the size of single particles, either spheres, spheroids or irregular in shape. The particle size can be determined by any of the techniques known to a person skilled in the art, such as, but not limiting to microscopic measurement, sieves, laser diffraction and so on.

As used herein, the phrase ‘grain size’ or ‘granular size’ or ‘granularity’ refers to a precise, standardized measurement of the size of the crystals inside a metallic, crystalline solid.

As used herein, the phrase ‘flow temperature’ refers to complete melting temperature of a material/product.

As used herein, the phrase ‘Tumbler Index’ refers to a relative measure of the resistance of a material to breakage or degradation by impact. In an embodiment of the present disclosure, the Tumbler Index is employed to measure handling strength of the prepared calcium ferrite.

As used herein, the phrase ‘Abrasion Index’ refers to a relative measure of the degradation of a material by abrasion. In an embodiment of the present disclosure, the Abrasion Index is employed to measure the abrasive resistance of the prepared calcium ferrite.

The present disclosure is in relation to calcium ferrite production. An objective of the present disclosure is to develop a simple, economical and energy-efficient process of preparing calcium ferrite having high strength and that melts at lower temperatures (i.e. possesses low temperature melting behaviour).

Another objective of the present disclosure is to achieve calcium ferrite having increased reactivity with hot metal during production of steel.

Yet another objective of the present disclosure is to achieve calcium ferrite having highly efficient/improved dephosphorization of hot metal during production of steel.

Still another objective of the present disclosure is to prepare calcium ferrite that has high handling strength, expressed in terms of Tumbler Index. More particularly, an objective of the present disclosure is to prepare calcium ferrite possessing a Tumbler Index (+6.3mm) of greater than 65%.

Still another objective of the present disclosure is to prepare calcium ferrite that has lower melting point, expressed in terms of flow temperature (complete melting temperature). More particularly, an objective of the present disclosure is to prepare calcium ferrite possessing a flow temperature of less than 1250 oC.

Still another objective of the present disclosure is to prepare calcium ferrite comprising more pores, but yet strong enough to increase reactivity of said calcium ferrite with hot metal during production of steel. More particularly, an objective of the present disclosure is to prepare calcium ferrite possessing porosity greater than 15%.

Accordingly, the present disclosure provides a process for preparing calcium ferrite, comprising:
mixing an iron source, a calcium oxide source, a binder, a carbon containing material and water to prepare a mixture,
sintering the mixture to prepare the calcium ferrite,
wherein, particle size of the iron source is about 0.5 mm to 10 mm and particle size of the calcium oxide source is about 0.6 mm to 4 mm.

In an embodiment of the present process, the iron source is iron oxide. In an embodiment of the present process, the iron oxide is selected from a group comprising iron ore, mill scale, steel making fume dust, iron oxide from acid regeneration plant and combinations thereof.

In a preferred embodiment of the present process, the iron oxide is iron ore, mill scale, or a combination thereof.

In another embodiment of the present process, the calcium oxide source is selected from a group comprising limestone, calcite, calcined lime, quick lime and combinations thereof.

In a preferred embodiment of the present process, the calcium oxide source is limestone.

In yet another embodiment of the present process, the binder is selected from a group comprising lime powder, bentonite, dextrin, starch, cellulose and combinations thereof.

In a preferred embodiment of the present process, the binder is lime powder.

In still another embodiment of the present process, the carbon containing material is a fuel source. In an embodiment, said carbon containing material is selected from a group comprising anthracite coal, metallurgical coke, metallurgical coke breeze and combinations thereof.

In a preferred embodiment of the present process, the carbon containing material is metallurgical coke breeze.

In another preferred embodiment of the present process, the particle size of the iron source described above is about 0.5 mm to 10 mm. In yet another preferred embodiment of the present process, the particle size of the iron source described above is about 0.6 mm to 10 mm. In most preferred embodiments, the particle size of the iron source is about 6 mm, 8 mm, or 10 mm.

In exemplary embodiments of the present process, the particle size of the iron source described above is 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, 4 mm, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm, 4.5 mm, 4.6 mm, 4.7 mm, 4.8 mm, 4.9 mm, 5 mm, 5.1 mm, 5.2 mm, 5.3 mm, 5.4 mm, 5.5 mm, 5.6 mm, 5.7 mm, 5.8 mm, 5.9 mm, 6 mm, 6.1 mm, 6.2 mm, 6.3 mm, 6.4 mm, 6.5 mm, 6.6 mm, 6.7 mm, 6.8 mm, 6.9 mm, 7 mm, 7.1 mm, 7.2 mm, 7.3 mm, 7.4 mm, 7.5 mm, 7.6 mm, 7.7 mm, 7.8 mm, 7.9 mm, 8 mm, 8.1 mm, 8.2 mm, 8.3 mm, 8.4 mm, 8.5 mm, 8.6 mm, 8.7 mm, 8.8 mm, 8.9 mm, 9 mm, 9.1 mm, 9.2 mm, 9.3 mm, 9.4 mm, 9.5 mm, 9.6 mm, 9.7 mm, 9.8 mm, 9.9 mm, or 10 mm.

In an embodiment of the present process, the particle size of the iron ore described above is about 0.5 mm to 10 mm. In another embodiment of the present process, the particle size of the iron ore described above is about 0.6 mm to 10 mm. In preferred embodiments of the present process, the particle size of the iron ore is about 6 mm, 8 mm, or 10 mm.

In another preferred embodiment of the present process, the particle size of the calcium oxide source is about 0.6 mm to 3.15 mm. In a more preferred embodiment, the particle size of the calcium oxide source is about 1.5 mm, 2 mm, or 3.15 mm.

In exemplary embodiments of the present process, the particle size of the calcium oxide source described above is 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3 mm, 3.1 mm, or 3.15 mm.

In an embodiment of the present process, particle size of the binder is about 25 µm to 150 µm. In a preferred embodiment, the particle size of the binder is about 45 µm, 75 µm or 150 µm.

In another embodiment of the present process, particle size of the carbon containing material is about 0.15 mm to 4 mm. In a preferred embodiment, the particle size of the carbon containing material is about 0.15 mm, 0.25 mm, or 3.15 mm.

In an embodiment of the above described process, the water is added at about 6 wt% to 8 wt% of the total mixture.

In a preferred embodiment, the water is added at about 6.5 wt% to 7.5 wt% of the total mixture.

In exemplary embodiments of the above described process, the water is added at about 6 wt%, 6.1 wt%, 6.2 wt%, 6.3 wt%, 6.4 wt%, 6.5 wt%, 6.6 wt%, 6.7 wt%, 6.8 wt%, 6.9 wt%, 7 wt%, 7.1 wt%, 7.2 wt%, 7.3 wt%, 7.4 wt%, 7.5 wt%, 7.6 wt%, 7.7 wt%, 7.8 wt%, 7.9 wt%, or 8 wt% of the total mixture.

In another embodiment of the present process, the iron source is added at a concentration of about 40 wt% to 50 wt% of the total mixture. In a preferred embodiment, the iron source is added at a concentration of about 41 wt% to 46 wt% of the total mixture.

In exemplary embodiments of the above described process, the iron source is added at a concentration of about 41 wt%, 41.5 wt%, 42 wt%, 42.5 wt%, 43 wt%, 43.5 wt%, 44 wt%, 44.5 wt%, 45 wt%, 45.5 wt%, 46 wt%, 46.5 wt%, 47 wt%, 47.5 wt%, 48 wt%, 48.5 wt%, 49 wt%, 49.5 wt% or 50 wt% of the total mixture.

In yet another embodiment of the present process, the calcium oxide source is added at a concentration of about 40 wt% to 50 wt% of the total mixture. In a preferred embodiment, the calcium oxide source is added at a concentration of about 43 wt% to 47 wt% of the total mixture.

In exemplary embodiments of the above described process, the calcium oxide source is added at a concentration of about 41 wt%, 41.5 wt%, 42 wt%, 42.5 wt%, 43 wt%, 43.5 wt%, 44 wt%, 44.5 wt%, 45 wt%, 45.5 wt%, 46 wt%, 46.5 wt%, 47 wt%, 47.5 wt%, 48 wt%, 48.5 wt%, 49 wt%, 49.5 wt% or 50 wt% of the total mixture.

In still another embodiment of the present process, the binder is added at a concentration of about 2 wt% to 8 wt% of the total mixture. In a preferred embodiment, the binder is added at a concentration of about 2.5 wt% to 7.5 wt% of the total mixture.

In exemplary embodiments of the above described process, the binder is added at a concentration of about 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt% or 8 wt% of the total mixture.

In still another embodiment of the present process, the carbon containing material is added at a concentration of about 4 wt% to 8 wt% of the total mixture. In a preferred embodiment, the carbon containing material is added at a concentration of 4.5 wt% to 7.5 wt% of the total mixture.

In exemplary embodiments of the above described process, the carbon containing material is added at a concentration of about 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt% or 8 wt% of the total mixture.

In an exemplary embodiment of the present process, the iron ore has a composition comprising Fe(t) at a wt% of about 63.76, silicon dioxide (SiO2) at a wt% of about 2.41, calcium oxide (CaO) at a wt% of about 0.41, magnesium oxide (MgO) at a wt% of about 0.061, aluminum oxide (Al2O3) at a wt% of about 2.71, titanium dioxide (TiO2) at a wt% of about 0.165, and sulphur (S) at a wt% of about 0.003. Said iron ore further comprises at least one or more additional elements/components selected from chromium (Cr), manganese (Mn) and phosphorous (P) at various wt% to make up the final composition to 100 wt%.

In another exemplary embodiment of the present process, the mill scale has a composition comprising Fe(t) at a wt% of about 72.12, SiO2 at a wt% of about 0.55, CaO at a wt% of about 0.62, MgO at a wt% of about 0.022, TiO2 at a wt% of about 0.01, and S at a wt% of about 0.006. Said mill scale further comprises at least one or more additional elements/components selected from chromium (Cr), titanium (Ti) and phosphorous (P) at various wt% to make up the final composition to 100 wt%.

In an embodiment of the above described process, the mixing of iron source, calcium oxide source, binder, carbon containing material and water could be in any order.

In a preferred embodiment of the above described process, the mixture obtained by mixing an iron source, a calcium oxide source, a binder, a carbon containing material and water is a granulated mixture.

In an exemplary embodiment of the present process, the mixing of the iron source, the calcium oxide source, the binder, the carbon containing material and the water is carried out in a mixing drum or granulation drum to prepare the granulated mixture.

In an embodiment of the above described process, the sintering step comprises charging, igniting and burning of the mixture comprising iron source, calcium oxide source, binder, carbon containing material and water in a sintering machine.

In another embodiment of the above described process, the sintering step results in the reaction of the calcium oxide and the iron oxide to form a hot sintered calcium ferrite cake.

In an embodiment of the present process, the sintering machine is selected from a group comprising Dwight-Lloyd sintering machine, stationary sinter pot, pan sintering setup, and combinations thereof.

In a preferred embodiment of the present process, the sintering machine is Dwight-Lloyd sintering machine, stationary sintering pot furnace, or a combination thereof.

In another embodiment of the present process, the sintering step to obtain the hot sintered calcium ferrite cake is carried out at a temperature of about 1100 oC to 1350 oC.

In exemplary embodiments of the present process, the sintering step to obtain the hot sintered calcium ferrite cake is carried out at a temperature of about 1100 oC, about 1150 oC, about 1200 oC, about 1250 oC, about 1300 oC or about 1350 oC.

In preferred embodiments of the present process, the sintering step to obtain the hot sintered calcium ferrite cake is carried out at a temperature of about 1100 oC, about 1200 oC, or about 1250 oC.

In yet another embodiment of the present process, the sintering step to obtain the hot sintered calcium ferrite cake is carried out for a time-period of about 20 minutes to 60 minutes.

In exemplary embodiments of the present process, the sintering step to obtain the hot sintered calcium ferrite cake is carried out for a time-period of about 20 minutes, about 25 minutes, about 30 minutes, about 35 minutes, about 40 minutes, about 45 minutes, about 45 minutes, about 50 minutes, about 55 minutes, or about 20 minutes.

In preferred embodiments of the present process, the sintering step to obtain the hot sintered calcium ferrite cake is carried out for a time-period of about 20 minutes or about 30 minutes.

In still another embodiment of the present process of preparing calcium ferrite, the process further comprises cooling the hot sintered calcium ferrite cake obtained during the sintering step, crushing the cake and screening the crushed cake to obtain a calcium ferrite sinter.

In an exemplary embodiment of the above described process, the prepared calcium ferrite sinter is at a size ranging from about 10 mm to 40 mm.

In an embodiment of the present process, the prepared calcium ferrite comprises calcium oxide at a concentration of about 25 wt% to 45 wt% and iron oxide at a concentration of about 40 wt% to 60 wt%.

In another embodiment of the present process, the prepared calcium ferrite comprises a calcium ferrite phase of about 50% to 65%, a hematite phase of about 15% to 20%, a magnetite phase of about 1% to 3%, a slag melt phase of about 3% to 5%, and pores of about 15% to 30%. In an exemplary embodiment, the calcium ferrite phase formed because of the reaction between calcium oxide and iron oxide has an acicular needle like microstructure structure to enhance strength and to quickly react with hot metal during production of steel. More particularly, the prepared calcium ferrite has an acicular needle like microstructure, possesses enhanced strength and immediately reacts with hot metal during steel making process to remove phosphorous.

In still another embodiment of the present process, the prepared calcium ferrite possesses a handling strength, expressed as Tumbler Index, of about 65% to 80% (+6.3mm); and Abrasion Index (-0.5mm) of about 3 to 7.5%.

In still another embodiment of the present process, the prepared calcium ferrite exhibits a low temperature melting behavior, expressed as flow temperature (complete melting temperature), in a temperature range of about 1200 oC to 1250 oC.

In an exemplary embodiment of the present process, the preparation of calcium ferrite comprises sintering a granulated mixture of iron oxide, limestone, lime powder, carbon bearing material and water to obtain a sintered calcium ferrite cake; followed by cooling the cake in air, crushing (sizing) and screening to obtain the calcium ferrite sinter.

In another exemplary embodiment of the present process, the preparation of calcium ferrite comprises:
(a) mixing iron source having a particle size of about 0.5 mm to 10 mm at a concentration of about 40 wt% to 50 wt%, calcium oxide source having a particle size of about 0.6 mm to 3.15 mm at a concentration of about 40 wt% to 50 wt%, lime powder at a concentration of about 2 wt% to 8 wt%, coke breeze at a concentration of about 4 wt% to 8 wt% and water at abo ut 6 wt% to 8 wt% to produce a granulated mixture;
(b) charging, igniting and burning the granulated mixture in a sintering machine at a temperature of about 1100 oC to 1350 oC for a time-period of about 20 minutes to 60 minutes to produce the hot sintered calcium ferrite cake; and
(c) cooling the hot sintered calcium ferrite cake, crushing the cake, and screening the crushed cake to obtain calcium ferrite sinter in the size of about 10 mm to 40 mm.

In yet another exemplary embodiment of the present process, the preparation of calcium ferrite comprises:
(a) mixing iron oxide as an iron source having a particle size of about 0.5 mm to 10 mm at a concentration of about 40 wt% to 50 wt%, limestone as calcium oxide source having a particle size of about 0.6 mm to 3.15 mm at a concentration of about 40 wt% to 50 wt%, lime powder as binder at a concentration of about 2 wt% to 8 wt%, coke breeze as fuel at a concentration of about 4 wt% to 8 wt%, and water at about 6 wt% to 8 wt% in a mixing drum or a granulation drum to produce a granulated mixture;
(b) charging, igniting and burning the granulated mixture in a sintering machine at the temperature of about 1100 oC to 1350 oC for a time-period of about 20 minutes to 60 minutes to produce the hot sintered calcium ferrite cake; and
(c) cooling the hot sintered calcium ferrite cake in air, crushing the cake in sinter crushing machine, and screening the crushed cake in screening machine to obtain calcium ferrite sinter in the size of 10 mm to 40 mm.

The present disclosure further relates to calcium ferrite product including calcium ferrite or calcium ferrite sinter obtained by the calcium ferrite preparation process as described herein.

In an embodiment of the present disclosure, the calcium ferrite comprises a calcium ferrite phase of about 50% to 65%, a hematite phase of about 15% to 20%, a magnetite phase of about 1% to 3%, a slag melt phase of about 3% to 5%, and pores of about 15% to 30%.

In another embodiment of the present disclosure, the calcium ferrite possesses an acicular needle like microstructure structure.

In yet another embodiment of the present disclosure, the calcium ferrite comprises calcium oxide at a concentration of about 25 wt% to 45 wt%, and iron oxide at a concentration of about 40 wt% to 60 wt%.

In an exemplary embodiment of the present disclosure, the calcium ferrite comprises Fe(t) at a concentration of about 35 wt% to 45 wt%, FeO at a concentration of about 8 wt% to 11 wt%, CaO at a concentration of about 25 wt% to 45 wt%, SiO2 at a concentration of about 2 wt% to 7 wt%, MgO at a concentration of about 1 wt% to 3 wt%, Al2O3 at a concentration of about 1 wt% to 3 wt%, and phosphorous (P) at a concentration of about 0.05 wt% to 0.4 wt%.v Said calcium ferrite further comprises at least one or more additional elements/components selected from chromium (Cr), titanium (Ti), copper (Cu) and sulphur (S) at various wt% to make up the final composition to 100 wt%.

In an embodiment of the present disclosure, the calcium ferrite possesses a handling strength, expressed as Tumbler Index, of about 65% to 80% (+6.3mm).

In another embodiment of the present disclosure, the calcium ferrite possesses an Abrasion Index (-0.5mm) of about 3 to 7.5%.

In yet another embodiment of the present disclosure, the calcium ferrite exhibits a low temperature melting behavior, expressed as flow temperature (complete melting temperature), in the temperature range of about 1200 oC to 1250 oC.

The present disclosure also describes a process of dephosphorization of metal during production of steel, said process comprising reacting the calcium ferrite described herein with the metal to obtain dephosphorized metal and phosphorous rich slag.

In an embodiment of the above described dephosphorization process, the metal is hot metal.

In another embodiment of the above described dephosphorization process, the calcium oxide from the calcium ferrite increases the dephosphorization rate.

In yet another embodiment of the above described dephosphorization process, the calcium ferrite comprises a calcium ferrite phase of about 50% to 65%, a hematite phase of about 15% to 20%, a magnetite phase of about 1% to 3%, a slag melt phase of about 3% to 5%, and pores of about 15% to 30%; and wherein the calcium ferrite comprises calcium oxide at a concentration of about 25 wt% to 45 wt% and iron oxide at a concentration of about 40 wt% to 60 wt%.

In still another embodiment of the above described dephosphorization process, the calcium ferrite possesses high handling strength to withstand handling loads and exhibits a low temperature melting behavior, expressed as flow temperature, in a temperature range of about 1200 oC to 1250 oC enabling quick reaction with the hot metal to remove phosphorous during the production of steel.

The present disclosure further provides use of the calcium ferrite described herein as a dephosphorization agent during production of steel.

In an embodiment of the present disclosure, the calcium ferrite removes phosphorous from hot metal during the production of steel resulting in manufacture of low phosphorous steel.

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: Preparation of calcium ferrite using Dwight-Lloyd sintering machine by employing iron ore as iron source and limestone as calcium oxide source
This example demonstrates the production of calcium ferrite sinter in Dwight-Lloyd sintering machine by employing iron ore as an iron source and limestone as calcium oxide source.

Table 1 provides the chemical composition of major raw materials/ingredients employed for calcium ferrite production. Further, the particle sizes of the raw materials employed in the present preparation are: iron ore at a particle size between 0.5 mm to 10 mm, limestone at a particle size between 0.6 mm to 3.15, lime powder at a particle size between 25 microns to 150 microns, and coke breeze at a particle size between 0.6 mm to 4 mm.

Table1: Chemical composition (in wt%) of major raw materials employed in production of calcium ferrite sinter
Raw Materials Fe(T) CaO SiO2 Al2O3 MgO TiO2 S
Iron ore 63.76 0.148 2.41 2.71 0.061 0.165 0.003
Limestone 1.93 43.69 8.43 1.15 4.97 0.005 0.071
Lime 0.6 67.31 0.977 0.36 0.839 0.083 0.111

The process of preparing calcium ferrite begins with the preparation of the raw materials consisting of iron ore fines, fluxes (limestone and lime), and fuel (coke breeze). These materials are mixed in a rotating drum and water is added around 6-8 wt% to reach proper agglomeration of the raw materials mix into micro billings in the range of about 2-3 mm. To complete the chemistry of calcium ferrite (CF), burnt lime is added as trimming addition in the range of about 1-4 wt%. Similarly, limestone is also added at about 4-6 wt%. The obtained agglomeration/granular mixture is in the form of micro-pellets. These micro pellets assist in obtaining optimum permeability during the sintering process. These micro pellets are then conveyed to the sintering machine and charged.
A layer of controlled size sinter (bedding) is fed to the bottom of the sinter called as hearth layer for the protection of the grates. After this, the moistened micro pellets of the raw materials mix are fed and leveled. For the production of calcium ferrite, the masses of raw materials employed is as shown below:
Iron ore - 47 wt. %
Limestone – 42.8 wt. %
Lime – 3.7 wt. %
Coke Breeze – 6.5 wt. %
Water – 6.5 wt. % of the total weight of iron ore, limestone, lime and coke breeze mixture

For production of normal sinter in plant, sinter return fines are employed in major proportions (15-30%). However, in case of calcium ferrite production, return sinter is not a part of blend for close control of chemistry.

After the raw materials mix (moistened micro pellets) is leveled on the sinter machine, the surface of the charged material on the sinter machine is ignited using gas or oil burners. Air is drawn through the moving bed causing the fuel to burn.

During the production of calcium ferrite sinter, the vertical machine speed in the range of 2.3 to 2.6m/min and ignition hood temperature in the range of about 1000 oC to1100 oC is maintained. Sinter machine velocity and gas flow are controlled to ensure that ‘burn through’ (i.e. the point at which the burning fuel layer reaches the base of the strand) occurs just prior to the sinter being discharged. The burn through point is the indication of completion of sintering process. During production, the burn through temperature in the range of about 230 oC to 260 oC and the suction pressure in the range of about 100-110 mbar is maintained. Total sintering time of about 25-35 minutes is employed.

At the end of the machine, the sintered material in the form of cake is discharged into the hot sinter crusher. Here, the hot sinter cake is crushed to a pre-determined maximum particle size of about 10-30 mm. From here, the crushed cake is discharged from the sinter. After cooling, the sinter is transferred to screening section wherein the sinter is screened in the size range of about -40 mm to +10 mm.

In the screening section, the product (sinter), bedding and return fines are separated. Return fines not suitable for downstream processing are conveyed to a bin for recycling in the sintering process.

The prepared calcium ferrite sinter is tested for chemical and microstructural analysis. The results of microstructural analysis are provided under Figures 4-6, respectively. The chemistry of prepared calcium ferrite sinter is provided in Table 2.

Table 2: Chemical composition (wt% of major constituents) of calcium ferrite sinter produced in sintering machine
Samples Fe(T) FeO CaO SiO2 Al2O3 MgO
Calcium Ferrite sinter 45.10 8 26.84 4.41 2.32 1.19

The handling strength and abrasion properties of the prepared calcium ferrite sinter are also tested. In tumbler test, 15 kg of about 10-40 mm size calcium ferrite sinter is conveyed for rotation in a drum (1 m diameter, 0.5m width) for 200 revolutions with 25 RPM. After revolutions, the percentage of +6.3mm is the tumbler index (TI) and percentage of -0.5mm is the abrasion index (AI) of the calcium ferrite sinter. The tumbler index and abrasion index of calcium ferrite sinter produced in the present example is shown in Table 3.

Table 3: Tumbler Index and Abrasion Index of calcium ferrite sinter produced in sintering machine
Sample Tumbler Index Abrasion Index
Calcium Ferrite sinter 77.5 % 3.2 %

The above results indicate the achievement of calcium ferrite sinter possessing high strength and high abrasion resistance, prepared by the present process employing raw materials with larger/coarse particle size.

EXAMPLE 2: Preparation of calcium ferrite using sinter pot by employing iron ore as iron source and limestone as calcium oxide source
This example demonstrates the production of calcium ferrite sinter using sinter pot by employing iron ore as the iron source and limestone as the calcium oxide source.

Table 4 provides the chemical composition of major raw materials/ingredients employed for calcium ferrite production. Further, the particle sizes of the raw materials employed in the present preparation are: iron ore at a particle size between 0.5 mm to 10 mm, limestone at a particle size between 0.6 mm to 3.15 mm, lime powder at a particle size between 25 microns to 150 microns and coke breeze at a particle size between 0.6 mm to 4 mm.

Table 4: Chemical composition (in wt%) of major raw materials employed in production of calcium ferrite sinter
Raw Materials Fe(T) CaO SiO2 Al2O3 MgO TiO2 S
Iron ore 63.76 0.148 2.41 2.71 0.061 0.165 0.003
Limestone 1.93 43.69 8.43 1.15 4.97 0.005 0.071
Lime 0.6 67.31 0.977 0.36 0.839 0.083 0.111

Further, the masses of raw materials employed for the production of calcium ferrite is as shown below:
Iron ore – 43 wt %
Limestone - 43 wt %
Lime - 7 wt %
Coke breeze 7 wt %
Water – 7.5 wt % of the total weight of iron ore, limestone, lime and coke breeze mixture

The process of preparing calcium ferrite begins with mixing 30 kg of sinter raw mix (iron ore, limestone and lime) in a mixer drum for about 3 to 5 minutes. Thereafter, moisture is added and mixed for about 8 to 10 minutes to convert the fines into micro ball having mean particle size of about 2.5 mm. The green sinter mix is then transferred to 30 kg pot sinter. Pot sinter is ignited for about 3 minutes with ignition hood followed by suction. In all set of trials, the suction rate and the ignition flame temperature for firing the sinter during sintering process is kept constant (1300 mm of water column) and at about 1000 oC respectively.

During sintering process, the time to complete the sintering process is noted i.e. after achieving the burn through temperature of sinter bed (maximum temperature of waste gas). The fired sinter is then stabilized by dropping the whole mass of sinter for about 4 times from 2 meter height. After dropping, minus 5 mm fraction of sinter fines is removed and weighed, and the remaining sinter is further screened in size range of about -40 mm to +10 mm for tumbler test. The sinter is then tested for chemical and microstructural analysis. The results of microstructural analysis are provided under Figures 1-3, respectively.

The chemistry of prepared calcium ferrite sinter is provided in Table 5.

Table 5: Chemical composition (wt% of major constituents) of produced calcium ferrite
Calcium ferrite sinter Fe(T) FeO CaO SiO2 Al2O3 MgO
Iron ore 40.5 8 30.14 6.7 1.61 2.48

The handling strength and abrasion properties of the prepared calcium ferrite sinter are tested. In tumbler test, 15 kg of about 10-40 mm size calcium ferrite sinter is conveyed for rotation in a drum (1 m diameter, 0.5m width) for 200 revolutions with 25 RPM. After revolutions, the percentage of +6.3mm is the tumbler index (TI) and percentage of -0.5mm is the abrasion index (AI) of the calcium ferrite sinter. The tumbler index and abrasion index of calcium ferrite sinter produced in the present example is shown in Table 3.

Table 6: Tumbler Index and Abrasion Index of calcium ferrite sinter produced in sinter pot
Sample Tumbler Index Abrasion Index
Calcium Ferrite sinter 76.8 % 5.2 %

The above results indicate the achievement of calcium ferrite sinter possessing high strength and high abrasion resistance, prepared by the present process employing raw materials with larger/coarse particle size.

EXAMPLE 3: Preparation of calcium ferrite using sinter pot by employing mill scale as iron source and limestone as calcium oxide source
This example demonstrates the production of calcium ferrite sinter in sinter pot by employing mill scale as iron source and limestone as calcium oxide source.

Table 7 provides the chemical composition of major raw materials/ingredients employed for calcium ferrite production. Further, the particle sizes of the raw materials employed in the present preparation are: iron ore at a particle size between 0.5 mm to 10 mm, limestone at a particle size between 0.6 mm to 3.15 mm, lime powder at a particle size between 25 microns to 150 microns and coke breeze at a particle size between 0.6 mm to 4 mm.

Table 7: Chemical composition (in wt%) of major raw materials employed in production of calcium ferrite sinter
Raw Materials Fe(T) CaO SiO2 Al2O3 MgO TiO2 S
Mill scale 72.12 0.62 0.55 0.22 0.022 0.01 0.006
Limestone 1.93 43.69 8.43 1.15 4.97 0.005 0.071
Lime 0.6 67.31 0.977 0.36 0.839 0.083 0.111

Further, the masses of raw materials employed for the production of calcium ferrite is as shown below:
Iron ore – 41.5 wt %
Limestone – 43.5 wt %
Lime – 7.5 wt %
Coke breeze 7.5 wt %
Water – 7 wt % of the total weight of iron ore, limestone, lime and coke breeze mixture

The process of preparing calcium ferrite begins with mixing 30 kg of sinter raw mix (iron ore, limestone and lime) in a mixer drum for about 3 to 5 minutes. Thereafter, moisture is added and mixed for about 8 to 10 minutes to convert the fines into micro ball having mean particle size of about 2.5 mm. The green sinter mix is then transferred to 30 kg pot sinter. Pot sinter is ignited for about 3 minutes with ignition hood followed by suction. In all set of trials, the suction rate and the ignition flame temperature for firing the sinter during sintering process is kept constant (1300 mm of water column) and at about 1000 oC respectively.

During sintering process, the time to complete the sintering process is noted i.e. after achieving the burn through temperature of sinter bed (maximum temperature of waste gas). The fired sinter is then stabilized by dropping the whole mass of sinter for about 4 times from 2 meter height. After dropping, minus 5 mm fraction of sinter fines is removed and weighed, and the remaining sinter is further screened in size range of about -40 mm to +10 mm for tumbler test. The sinter is then tested for chemical analysis.

The chemistry of prepared calcium ferrite sinter is provided in Table 5.

Table 8: Chemical composition (wt% of major constituents) of produced calcium ferrite
Calcium ferrite sinter Fe(T) FeO CaO SiO2 Al2O3 MgO
Iron ore 37.51 10.5 42.06 1.21 1.13 0.36

The handling strength and abrasion properties of the prepared calcium ferrite sinter are tested. In tumbler test, 15 kg of about 10-40 mm size calcium ferrite sinter is conveyed for rotation in a drum (1 m diameter, 0.5m width) for 200 revolutions with 25 RPM. After revolutions, the percentage of +6.3mm is the tumbler index (TI) and percentage of -0.5mm is the abrasion index (AI) of the calcium ferrite sinter. The tumbler index and abrasion index of calcium ferrite sinter produced in the present example is shown in Table 3.

Table 9: Tumbler Index and Abrasion Index of calcium ferrite sinter produced in sinter pot
Sample Tumbler Index Abrasion Index
Calcium Ferrite sinter 65.14 % 7.14 %

The above results thus indicate the achievement of calcium ferrite sinter possessing high strength and high abrasion resistance, prepared by the present process employing raw materials with larger/coarse particle size.

The present disclosure is thus successful in providing a simple, economical, non-toxic and efficient method of preparing effective calcium ferrite from iron and calcium oxide containing materials. In particular, the present disclosure shows that highly efficient calcium ferrite can be prepared despite employing raw materials with greater/coarser particle sizes. The prepared calcium ferrite has high strength, expressed as Tumbler Index, of about 65% to 80% (+6.3mm), and high abrasion resistance with an Abrasion Index (-0.5mm) of about 3 % to 7.5 %. Said calcium ferrite is capable of withstanding handling loads and melting at low temperatures such that the calcium ferrite quickly reacts with hot metal to remove phosphorous effectively during production of steel. Additionally, cost of preparing calcium ferrite by the process described herein is very low because the process does not comprise complete melting of the constituents/raw materials. The prepared calcium ferrite is immensely advantageous as a dephosphorizing agent during steel production for removing phosphorous from the hot metal to achieve low phosphorous steel or dephosphorized steel, and in other applications which requiring high strength calcium ferrite.