Title: A method of production of silicomanganese alloy containing 50-60 weight % Mn
from low grade ferruginous Mn ore
Field of invention:
The present Invention relates metallurgy of manganese and silicon alloy, More specifically the invention describes the use of low grade ferruginous manganese ore in production of silicomanganese alloy by carbothermic reduction in submerged arc furnace without any intermediate beneficiation process steps
Background of invention
Silicomanganese (SiMn) is used as a more effective deoxidizing agent than high carbon ferromanganese in production of different types of steels It is also used as a feed stock to produce refined alloys such as medium and low carbon ferromanganese Using SiMn instead of ferromanganese (FeMn) and ferrosilicon (FeSi) provides technical advantage and also results in cost reduction Indian manganese ore deposits found in Orissa, Madhya Pradesh, Andhra Pradesh, Maharashtra and Gujarat states are mostly ferruginous i e. Ferruginous ores contain high amount of iron having low Mn/Fe ratio There is need to utilize these low grade ferruginous Mn ore due to the scarcity of high grade Mn ore deposits As Mn/Fe ratio is crucial for SiMn production and these ferruginous Mn ore are not suitable for the production of standard grade SiMn
Prior art
CN102041400B patent discloses a process and equipment for producing Manganese and silicon alloy containing 50-85% of manganese from low- grade manganese ore containing 10-25 % of Manganese The equipment for production of high manganese silicon alloy consists of melting furnace, oxidizer, and an electric arc furnace. In this method the low grade Mn ore is melted in presence of carbonaceous material and flux material to the temperature of 1400-1450°C so as to reduce iron from the melt and enrich manganese oxide in slag. The iron is transferred to the oxidation furnace and manganese enriched slag to electric arc furnace to produce silicomanganese

RU2198235 patent discloses the method of obtaining low phosphorous silicomanganese and ferromanaganese from lean grade ore The method described in this patent consists of three consecutive converter types of units located in succession In this method the lean grade ore is treated in succession with coal, metallic additive, oxygen to upgrade the MnO content and reduce the phosphorous content before smelting process
Ahmed et al, 2007, studied the possibility of using local Egyptian manganese ores mixed with ferromanganese slag to produce silicomanganese alloy in a submerged arc furnace at a relatively low temperature, The literature revealed that a standard silicomanganese alloy containing Mn:
65 9-69.0%,Si; 15,6-17.6%, C; 1,8-2.35% C, P; 0 1-0,2% and S: 0,015-0.025% can be produced from the optimal choice of raw materials mix and optimum conditions controlling the production process, such as smelting time, basicity, coke ratio, Mn/Fe and Mn/Si ratios of the blend to obtain standard SiMn.
Ahmed et al. 2014, studied the factors that affecting the production of silicomanganese using manganese rich slag in production of silicomanganese. The literature revealed that the optimum metallic yield and recoveries of manganese and silicon can be achieved with slag basicity, (CaO + MgO)/Al203 of 1.8 by using dolomite as fluxing material and charging quartzite and fluorspar in percentage of 25% and 4% of the blend, respectively,
Alex et al 2007, worked on extraction of silicomanganese from marine and low grade mineral resources. This research has shown that blending the sea nodule residue with a suitable combination of Fe-Mn slag and manganese ore will help to maintain the Mn/Fe ratio and recovery required for 60Mnl4Si grade of alloy.
There is prior art that describes the production of silicomanganese from low grade Manganese ores however, all these processes involve intermediate beneficiation or pyro metallurgical or combination of both processing steps

Indian manganese ore deposits found in Orissa, Madhya Pradesh, Andhra Pradesh, Maharashtra and Gujarat states are mostly ferruginous i e Ferruginous ores contain high amount of iron having low Mn/Fe ratio Hence, there is a need of a process that can produce silicomanganese alloy without involvement of intermediate beneficiation process steps,
Objective of invention:
The object of the present invention to propose a process for production of silicomanganese alloy containing 50-60% Manganese and 11-24% Silicon by using the low grade ferruginous manganese ore, slag from high carbon ferromanganese production and gas cleaning plant (GCP) sludge
Still another object of the invention is to propose a process that does not involve intermediate benefaction steps of beneficiating the low grade ferruginous manganese ore
Still another object of the invention is to produce silicomanganese alloy using plant by-products such as ferromanganese slag and GCP sludge agglomerates with control of input basicity,
Summary of invention
The current invention describes a process for production of silicomanganese alloy with a composition of 50-60 wt% of Mn, 11-24 wt% of silicon from low grade ferruginous Mn ore As per IS: 11895-2006, the low grade ferruginous Mn ore has a Mn 25-35 wt%, Fe: 13-23 wt% The process describes the production of silicomanganese alloy by carbothermic reduction of feed in a submerged arc. The feed as per the current invention comprises 50-60 wt% low grade ferruginous Mn ore (Mn/Fe=2 1-2.5), 40-45 wt% Ferro Manganese slag (Mn/Fe=22-27) and 10-15 wt% GCP sludge generated (Mn/Fe-9 to 11) at input basicity of 0 3 to 0 45 and input R value of 1.3 to 1 8

Description of Drawings;
Fig 1 explains the slag-liquid projection for pseudo-ternary slag system (CaO+MgO)-AJ203-Si02-MnO.
Detailed description of the invention
Silicomanganese alloy is produced by smelting of manganese bearing raw materials, quartz, coke and fluxes in submerged arc furnaces (SAF) In an embodiment of the current invention, Ferrosilicon or silicon remelts and off grade products may also be used to increase Si content in the final product The process of producing silicomanganese alloy from low grade ferruginous Manganese (Mn) comprises subjecting feed mixture comprising low grade ferruginous Mn ore, Ferromanganese slag and GCP sludge to carbothermic reduction The process further employs fluxes such as dolomite, quartzite. In an embodiment of the invention coke is used as reductant Coke amount has significant effect on Si recovery in alloy Coke amount beyond theoretical amount has little effect on the recovery of Fe and Mn content in alloy In an embodiment of the invention, coke is present approximately 30-35 weight percentage of above Mn bearing raw materials mix (Ore, FeMn slag, GCP sludge) considered during
Quartzite and dolomite are added to achieve target level of input basicity, B ((CaO+MgO)/Si02) and input R ((CaO+MgO)/A12O3) values In silicomanganese smelting, R is defined as an alternative basicity term in terms of ratio of stable oxides or non-reducible oxides i e, R=(CaO+MgO)/A12O3 In an embodiment of the current invention, the input burden basicity values (B) varies in the range of 0 3 to 0 45 and alternate basicity in terms of stable or non-stable oxides-Input R ((CaO+MgO)/A12O3) value varies in the range of 1.3 to 1.8 In an embodiment of the invention, the GCP sludge agglomerates are used in the form of briquettes In another embodiment of the invention, the GCP sludge agglomerates are used in the form pellets,
All the input raw materials such as Mn bearing materials (Mn ore, Ferromanganese slag and GCP sludge agglomerate), Fluxes (quartizite and dolomite) and reductant (coke) are mixed and charged to the furnace together in a continuous charging manner The operation consists of (a) heating of

furnace (b) charging of raw material (c) Holding or soaking. The heating of the furnace crucible was done by arcing between electrode and coke at bottom. Charging of raw materials into the arc furnace was started after it attains the desired temperature During experiment the operation temperature was maintained at 1600±50°C, A holding time or soaking time was allowed to the molten mass after completion of charging activity After the completion of smelting operation the electrode was withdrawn from the crucible and the slag-metal molten mass was allowed to cool inside the crucible Thereafter, it was taken out and metal and slag were separated manually
In an embodiment of the current invention, the carbothermic reduction is performed in a submerged arc furnace The feed mixtures as per the current invention comprises of Ferruginous manganese weight percentage in the range of 50 to 60, Ferromanganese slag weight percentage in the range of 40 to 45, GCP sludge weight percentage in the feed mixture varies in the range of 10-20 Fluxes are added to the feed mixture to achieve the desired level of input basicity, B ((CaO+MgO)/SiO2) and input R ((CaO+MgO)/A12O3) values.
The final slag composition contains slag composition contains CaO: 15 to 27 wt%., MgO: 4 to 12 wt%, SiO2: 24 to 46, A12O3 13 to 31, MnO: 3 to! 2, FeO: 0 4 to 4 wt%.
In an embodiment of the current invention, the low grade Ferruginous manganese ore, Ferromanganese slag, GCP Sludge has Manganese to Iron (Mn/Fe) ratio varying from 2 1 to 2 5, 22 to 27 and 9 to 11 respectively
The different chemical constituents of the low grade Ferruginous manganese ore, Ferromanganese slag, GCP Sludge, Dolomite, Quartzite and Coke are present in varying weight percentage as described in the table 1 below:


Silicomanganese production is often integrated with HCFeMn so that the ferromanganese slag car be used in Silicomanganese production Fig 1 explains the slag-liquid projection for pseudo-ternary slag system (CaO+MgO)-Al2O3-SiO2-MnO
Following are the probable reactions occur during smelting process:

Equation (1) and (3) are independent reactions and Equation (4) is a combination of both of these.

Slag/metal reaction is represented by Equation (4) and it is fast compared to Equation (1) and (3),. Equation (1) is a sluggish reaction and it is usually disregarded (Davidson 2011) SiO2 in the slag is reduced according to equation (2) as SiC replaces graphite as the stable carbon phase
The slag in silicomanganese production consists of two types of oxides (1) reducible types such as SiO2, MnO and FeO (2) un-reducible types such as A12O3, CaO and MgO The un-reducible oxides will not be reduced under the conditions present in the furnace Iron can be reduced directly by CO (g) in the charge, before the raw materials reach the coke bed zone At temperatures preferably around 1600°C practically all the iron will be present in the metal phase The un-reducible oxides are introduced through the fluxing materials and other raw materials added during smelting. These oxides such as CaO, A12O3 and MgO remain almost stable during the smelting process but affect the thermo dynamical and physical properties of the slag Hence the slag composition and its thermodynamic properties are vital for determining the alloy composition as it effects on the distribution of Si and Mn between the alloy and slag phase. The basicity of SiMn slag is expressed as the ratio between the basic and acid slag constituents as given in equation During SiMn production both MnO and SiO2 are reduced out from the slag So for an alternative measure of slag basicity, an expression (R) containing only unreducible oxides is more relevant than basicity expression given by equation (8) According to the equilibrium studies of earlier researchers R ratio strongly influences the SiO2 activity of the slag and therefore significantly affects the alloy composition in silicomanganese

The Mn and Si recovery during the process depends on the slag composition The basic oxides such as MgO and CaO play an important role in improving the MnO activity of the slag In SiMn smelting process the simultaneous reduction of Si and Mn becomes tricky to maintain the desired alloy grade as increasing percentage of Si will decrease Mn percentage Alumina behaves as basic component in acidic slag system and reduces MnO loss, while it behaves as acidic component in basic slag system and produce opposite effect So selection of slag basicity in SiMn production is very tricky as both MnO and SiO2 are reduced out from the slag So to avoid the ambiguity the

burden basicity is regulated by two basicity terms such as input B ((CaO+MgO)/SiO2) and input R ((CaO+MgO)/A12O3) values. In the present invention the Mn bearing raw materials mix is prepared after blending Mn ore, FeMn slag and/or GCP sludge agglomerates (pellet/briquette) in different weight ratios Quartizite and dolomite is added according to the desired level of input basicity, B ((CaO+MgO/SiO2) and input R ((CaO+MgO)/A12O3) values.
Example-1
500gm of Manganese ore, 400gm of high carbon ferromanganese slag, l00gm of GCP sludge, 230gm of quartzite, and 212 gm of dolomite and 320gm of coke are blended to make the charge mix material before smelting. During smelting experiments the operation time consists of a (a) heating of crucible for 15min (b) charging of raw material for 5 min (c) Holding or soaking for 10-20 min The heating of the crucible was done by arcing between electrode and coke at bottom. Charging of raw materials into the crucible was started after it attains the desired temperature The raw materials were added slowly to the crucible in small quantities and the charging operation completed in 5 minutes. During experiment the operation temperature was maintained at 1600±50°C and monitored by infrared pyrometer A holding time or soaking time of 10-20 was allowed to the molten mass. Molten slag and metal are allowed to cool inside the furnace after completion of the reduction experiment The metallic and non-metallic parts are physically separable and can be recovered by breaking the cakes The metallic part is of Silicomanganese alloy type and its composition: Mn- 58 78 wt%, Si-12 21 wt%, Fe-24 17 wr%, C-2 77 wt% The Slag composition consists of: CaO-17.36, MgO-9 06 wt%, A12O3-17.57 wt%, SiO2-34 57 wt%, MnO-8.85 wt%, FeO- 3 09 wt%.
Example-2
600gm of Manganese ore, 400gm of high carbon ferromanganese slag, 290gm of quartzite, 175 gm of dolomite and 320gm of coke are blended to make the charge mix material before smelting. The charging of the materials and smelting experiment in arc furnace and slag metal separation were conducted in a similar manner as explained in example-1 The Silicomanganese alloy obtained after experiment consists of: Mn- 50 95 wt%, Si-19 wt%, Fe-24 55 wt%, C-2 16 wt%. The Slag chemical composition consists of: CaO-24 33, MgO-4 44 wt%, A12O3-27,81 wt%, SiO2-26 25 wt%, MnO-4 42 wt%, FeO- 0 39 wt%.

The current invention uses plant by-products such as GCP sludge, high carbon ferromanganese slag. The process results in making use of the low grade ferruginous Manganese (Mn) ore The other advantage of the invention is that the desired alloy grade can be produced by controlling input basicity such as B ((CaO+MgO)/SiO2) and input R ((CaO+MgO)/Al203) values,

References
1 A. Ahmed, A, El-Molhammady, M Eissa, K. El-Fawakhry, Factors affecting silicomanganese production using manganese rich slag in the charge, (2007), steel research international, 78: 24-30
2 A Ahmed, S, Ghali, M K, El-Fawakhry, H El-Faramawy and M Eissa, Silicomanganese production utilising local manganese ores and manganese rich slag, (2014), Ironmaking and Steelmaking, 41: 310-320,
3 T C. Alex, K M Godiwalla, S Kumar and R K Jana, extraction of silicomanganese from marine and low grade mineral resources, proceedings of INFACON XI, Cape Town, South Africa, 2007, 206-214.
4 J E Davidsen, (2011) Formation of Silicon Carbide in the Silicomanganese Process, PhD thesis, NTNU.

We claim
1, A process of producing silicomanganese alloy from a low grade ferruginous Manganese
(Mn) ore, the process comprising:
subjecting feed mixture comprising the low grade ferruginous Manganese (Mn) ore, Ferromanganese slag and GCP sludge to carbothermic reduction in a submerged arc furnace
2, The process as claimed in claim 1, wherein the low grade ferruginous manganese ore has Manganese to Iron (Mn/Fe) ratio varying from 2.1 to 2 5.
3, The process as claimed in claim 1, wherein the low grade Ferruginous manganese ore weight percentage in the feed mixture varies in the range of 50 to 60

4 The process as claimed in claim 1, wherein the low grade Ferruginous manganese ore comprises (wt%): Mn: 25 to 35%, Fe 13 to 16, Si02: 2 to 5, Al2O3:4 to 6%
5 The process as claimed in claim 1, wherein the, Ferromanganese slag has Manganese to Iron (Mn/Fe) ratio varying from 22 to 27.
6 The process as claimed in claim 1, wherein the Ferromanganese slag weight percentage in the feed mixture varies in the range of 40 to 45.
7 The process as claimed in claim 1, wherein the Ferromanganese slag comprises (weight %) Mn: 22 to 27, Fe