In association with the National Metallurgical Academy of Ukraine, GoodRich offers Gas Oxygen Refiner (GOR) and other technologies for the following applications in the ferro-alloy industry –

1)   Conversion of high carbon ferro chrome into medium carbon ferro chrome in the GOR –

High carbon ferro chrome contains more than 8% carbon, which leads to lower chrome availability, higher oxygen consumption & prolonged time for stainless steel making in the AOD furnace.

In the GOR process, this high carbon ferro chrome can be converted into medium carbon ferro chrome (2% carbon) with a yield of 88-90%. The process takes 70-80 minutes.

When we use FeCr with 60% Cr, 8.5% C, 4% Si, 0.05% P (and the remaining iron) in the GOR, we get the medium carbon FeCr with the following composition –

Cr  –  58-62%

C   – 1.8-2.2%

Si  –   0.4-0.6%

There will be some chrome oxides in the slag, after the GOR process. To recover the chrome from its oxides, we need 30 kgs of Ferro Silicon (with 70% Si), per ton of medium carbon FeCr.  We also need 200-300 kgs of lime per ton. If FeSiCr with Si content of 40-50% is available, it can also be used to recover the chrome from the slag. In such a case, the consumption of FeSiCr is only 10-15 kgs per ton.

The consumption of gases per ton of medium carbon FeCr is –

1)   Oxygen                             –   120-130 m³/ton

2)   Natural gas / propane gas –   12-13 m³/ton

3)   Argon                                –   2-3 m³/ton

The ferro chrome containing 2% carbon is an import-substitute & sells at 50% higher price as compared to the ferro chrome containing 8% carbon. Hence the project is highly viable, with a pay-back period of 1 year.

Low carbon ferro chrome –   To produce low carbon ferro chrome, we need to use low carbon ferro-silico chrome (FeSiCr) as the starting material. FeSiCr normally contains 40% chrome, 30% Si, 30% Fe and 0.06% carbon. In this case, the process of getting low carbon ferro chrome is fast & efficient.

In the process, the liquid FeSiCr is poured into the GOR converter, where pre-heated lime stone & chromium ores are already added. After blowing with oxygen, argon and natural gas, low carbon FeCr is produced. The NMA has done such melts before.

For pre-heating the limestone and chromium ores, a rotary kiln is needed.  Pre-heating ensures the heat balance of the process, as the smelting temperatures of low carbon ferro chrome are quite high (1,680-1,700°C).

Low carbon ferro chrome is selling at double the price of high carbon ferro chrome in the market. Following are the typical consumption figures per ton of low carbon ferro chrome (containing Cr- 65.5%, Carbon- 0.05-01% and silicon 0.8-1.0%) –

–   Chromium ore                                  – 1,150-1,200 kgs

(Cr₂O₃– 50-52%; FeO- 16-17.25%)

–   Ferro silico chrome                        –    680 kgs (+ 5% to reach the required temperatures for the process)

–   Lime stone                                          –     1,050-1,100 kgs

–   Oxygen                                               –     8-12 m³

–   Argon                                                  –     5-7 m³

–   Natural gas                                         –      1 m³

Low-silicon ferro chrome – GOR can convert the high carbon ferro chrome with 4% silicon into high carbon ferro chrome with 1.5% silicon. For this purpose, oxidize the Si in the GOR, which happens before the oxidization of carbon. The recovery of low-silicon ferro chrome is 95-96%.

2) Production of chromium cast iron in the blast furnace –

The experience of the National Metallurgical Academy for industrial production of chromium cast iron with chrome content of 18-19% in the blast furnace is based on the following –

1)   It was not the mixture of chromium ore and iron ore, which was loaded into the blast furnace; but it was a preliminary prepared iron-chromium sinter (agglomerate).

2)   To determine the amount of chromium ore, it is necessary to calculate the amount of charging material for melting in the blast furnace, taking into account that chrome availability in the cast iron is 98%.

3)  Coke consumption increases and it is understandable. For industrial meltings (18-19% of chrome), this increase was 450-500 kg/ton of cast iron.

Taking into account the technology of melting in the blast furnace, NMA thinks that it is better to melt cast iron with chrome content of 8-10%. They had such experience in China. When melting the cast iron with 10% of chrome, coke consumption increases. Based on the meltings made in China, when producing cast iron with 7-8% of chrome, coke consumption in the charging material increased up to 100-140 kg/ton.

For melting of chromium cast iron in the blast furnace, use of the charge material (coke, iron ore, flux) with low phosphorous level is very important.

For small blast furnaces up to 30,000 tons/year, it may be problematic to make iron-chromium sinter (agglomerate).  However, there are some options, for example, to use chromium ore and an ordinary sinter in the charging material or to make pellets containing chrome of the required concentration. Here, we need just a simple “plate” to make chrome-containing pellets & NMA has this technology. We can also use chrome-containing briquettes; NMA knows how to make them and they can manufacture a special unit to make these briquettes.

Sometimes ago, they did experiments of pig iron smelting in the blast furnace with 19 – 20% chrome content. The amount of coke, required for the smelting, increased. There were problems with phosphorus, when smelting high chromium pig iron (phosphorus cannot be removed from the chromium-containing metal during further metallurgical processes).

While making chromium pig iron with 10% chrome content, the problems will be insignificant.

Smelting of manganese pig iron in the blast furnace –

As for the smelting of pig iron with enhanced manganese content of 15 – 16%, here also the NMA do not see any technological problems. In Ukraine, they still make ferro manganese in the blast furnaces. The question is where the produced pig iron with high manganese content of 15 -16% is going to be used. To be used in the smelting of 200 grade stainless steel, this pig iron must be decarbonized, which means that oxidizing-refining must be done. Here, a part of manganese will be lost. There are certain difficulties with oxidized manganese recovery during decarbonization. According to their estimate, up to 40% of pig iron’s manganese will be lost during steel smelting. In their opinion, the best time for alloying the metal bath by manganese is the recovery period of the converter melt.

3)   Conversion of low carbon silico manganese into metallic manganese in the GOR –

Here, the  molten low carbon silico manganese (containing 55% Mn, 0.1% carbon, 17% Fe & 28% silicon) is poured on to the GOR. Then, high grade manganese ore is added to the melt and the blowing is done by argon. The silicon in the silico manganese reacts with the oxides of manganese ore to produce metallic manganese as under –

[Si] + 2(MnO)→ 2[Mn] + (SiO₂)

Using the available grades of low carbon silico manganese in India, the metallic manganese can be produced with the following composition –

Mn  –  85-88%

Fe   –  12-13%

Si    –   1.5%

C     –   0.08%

The sulphur-phosphorus will remain at the same level, as in the silico manganese used.

If the imported silico manganese containing 65-70% Mn& 26-28% silicon is used in the process along with high grades of manganese ore (52-55% Mn), the metallic manganese will have 95% Mn. The landed cost of imported 95% metallic manganese into India is Rs. 105 per kg.

There is no restriction for the use of metallic manganese with increased Fe content (Mn 75-95% and Fe 2-12%) in the stainless steel / alloy steel. The use of metallic manganese is economically more efficient for making special steels.

To obtain 1 ton of 85-88% Mn, the following materials are needed –

a) 640-660 kgs of low carbon silico manganese (55% Mn & 28% Si); &

b) 1,200-1,250 kgs of manganese ore, based on the following typical composition –

–   Mn                       –   48%

–   Fe                         –   4.3%

–   SiO₂                     –   4.5%

–   Al₂O₃                    –   4.5%

–   Phosphorus          –   0.09%

The metallic manganese is obtained by the silico thermic process in the GOR, where Si acts as a reductant. The duration of the GOR process is less than 1 hour. The Mn content in the slag will be 8-12%.

The consumptions of utilities are –

–   Oxygen            –    10-15 m³/ton

–   Natural gas     –    5 m³/ton

–   Argon              –   15 m³/ton

–   Lime               –    600-650 kgs/ton

–   Refractory       –   25-30 kgs/ton

It is recommended to use low phosphorus-containing manganese ore, as the phosphorus content is one of the major indicators of the metallic manganese. The SiO₂ in the initial ore or in the concentrate should also be low, as the presence of manganese silicates complicates the process of smelting the metallic manganese in the GOR.

Since the metallic manganese is imported into India & demanded by the stainless steel manufacturers (to make 200 series), the project is highly viable with a payback period of 1 year.

4)    Pre-heating of manganese ore + coal and hot-charging into the submerged arc furnace- 

The National Metallurgical Academy (NMA) can provide the technology for pre-heating the manganese ore + coal in the rotary kiln and hot-charging into the submerged arc furnace. In Nikopolskii Ferro alloy plant, it resulted in a significant reduction of power consumption by 1,350 KWh/ton.

The rotary kiln can heat up the charge materials & also partially convert the  manganese ore into MnO. The NMA did a lot of work on the thermal treatment of  manganese concentrates or manganese ores for smelting into ferro manganese & silico manganese in 63 & 75 MVA arc furnaces, with the arc submerged into the charge material of the furnace bath.

Thermal treatment of manganese-containing charge materials allows the sintering of the manganese ore together with the carbon agent at a specified temperature & the recovery of manganese ore / concentrate into MnO; recovery of iron oxides into metal and simultaneous softening & lumping of the charge, to obtain sintered lumps.

The off gases from the closed submerged arc furnaces can also be used as a fuel for the rotary kiln. As a rule, such ferro-smelting furnaces can operate with the rotary kilns. The combustion of off gases in the rotary kiln ensures 50% reduction in the consumption of coal.

Using the sintered ferro-manganese charge with a set interval of softening does not increase the thickness of the softened layer in the furnace bath, between the melt & the solid charge. The electric regimes of ferro-manganese smelting with the use of hot-sintered charge by way of lumps of the charge materials do not differ from the smelting regimes of using the manganese ores directly. This fact remains the same, when we use the hot-sintered charge (lumps) for silico-manganese smelting.

The technology of smelting the hot-sintered lumps in the submerged arc furnaces also resulted in the increased recovery of ferro manganese by 5% and increased overall output by 25-28%.

5)    Technology to remove phosphorus & silicon from the manganese ore –

 NMA has developed a technology in 1980’s to remove phosphorus & silicon from the manganese ore.  Here, the Mn ore is mixed with soda ash (sodium carbonate or Na₂CO₃) & heated in a rotary kiln up to 900⁰ C.  P₂O₅& SiO₂ reacts with Na₂CO₃ & becomes water-soluble. Then, they are separated by using hot water.

Another advantage of the process is that we can recover sodium carbonate as a white powder, which can be directly used for glass production.

The size of the manganese ore used in the beneficiation process is 0-1 mm. When the original manganese ore contains 25% silica, it is possible to reduce the same to 12% in the process.  Any amount of phosphorus (for example, 1-2%) in the ore can be reduced to 0.06%.

6)  The combined process of making steel & ferromanganese from the ferruginous manganese ores, containing 25-30% Mn & 25-30% Fe –

The National Metallurgical Academy (NMA) has worked on the problems of using the ferruginous manganese ores to make acceptable grades of ferro manganese. They suggest the following alternate process route –

a) The ferruginous manganese ore is loaded into the ore-smelting furnace to get the molten manganese slag, containing 50-52% MnO. The other products are metallic manganese (up to 45%) and metallic iron (up to 50%) in the melt.

b) The slag containing 50-52% MnO is loaded into another submerged arc furnace, and ferro manganese is produced.

c) The metallic part is charged into the GOR to produce steel. The resulting slag contains 60% MnO, which is also loaded into the submerged arc furnace, to get Ferro manganese.

d) The power required to convert the molten MnO slag into FeMn (with high Mn) is 1,000-1,100 KWh per ton of slag.

Since high grades of manganese & steel can be produced separately and since the ferruginous manganese ores are cheap, this technology will result in higher profits, when compared to the blending of ferruginous manganese ores with imported manganese ores, having high Mn & low Fe.

The NMA has also developed many “classic” technologies for the production of metallic manganese and low carbon ferro manganese; with or without the use of GOR. These technologies have been tested by the Department of Ferro alloys & used by the large ferro alloy plants in Ukraine, even when the charge materials have problems, for example, high phosphorus-containing Mn ores.

7)  Ferro Nickel production in the existing ferro alloy plants –

The existing ferro alloy furnaces can be modified to make ferro nickel from nickel containing ores.  Such nickel ores are available in Indonesia, Philippines, Australia, New Caledonia, Russia etc., with 1.5 to 2% Ni & up to 20% Fe.  It can be converted into ferro nickel with 15–20% Ni, which sells at Rs. 100-130 per kg, at present.

India does not make even a single kg of ferro nickel & there is a demand for more than 1 million tons of ferro nickel from the Indian stainless steel manufacturers, which opens up a new business opportunity for more than Rs. 10,000 crores per year. The market size is enough to convert 100 sponge iron units / submerged arc furnaces into ferro nickel plants in India.  NMA has already given this technology to Sino Steel, China.

In the process, the nickel ore is preliminarily dried in a rotary drier to reduce its moisture content to 20%. It is then heated in a rotary kiln along with coal, limestone&hot-charged into a submerged arc furnace. The pre-heating time in the rotary kiln is 3 hours & the temperature of heating is 950°C. This temperature is increased to 1,400°C in the submerged arc furnace & the molten slag is continuously removed.  There is some coal consumption in the submerged arc furnace also.

The nickel concentration increases in the submerged arc furnace & ferro nickel is discharged once in 3 hours, when the nickel concentration reaches 10-15%. While nickel is fully recovered in the process, Fe is partially recovered & partially burnt. Hence, the process is called ‘Recovery burning’.

In the final stage, the molten ferro nickel is taken into the GOR, where its concentration increases to 15-20%.  (If the nickel content in the ore is 1.5%, then the nickel content in the final concentration is 15%; if the nickel in the ore is 2%, then the nickel content in the final concentration is 20%). In the GOR, excess carbon, silicon, phosphorus and also Fe are oxidized.

Nickel content in the slag of the submerged arc furnace is almost zero, while the nickel content in the slag of the GOR is 0.2%.  The carbon content in ferro nickel from the submerged arc furnace is 2.5-3%, while the same after the GOR process is 0.3%. The GOR process takes 40-50 minutes.

Finally, the finished ferro-nickel from the GOR is poured into the machine-cast piglets on a conveyor, or granulated.

It is possible to use the existing submerged arc furnaces to make crude ferro nickel, but the smelting needs a high secondary voltage & the furnaces should be closed type. The electricity consumption per ton of ferro nickel in the submerged arc furnace is 3,000 KWh. For the existing submerged arc furnaces, the pay-back period on the incremental investment (rotary kiln & GOR) will be less than 1 year.

If the nickel ore contains only 1.2% Ni, then it is possible to add some quantity of stainless steel scrap into the GOR, to bring the Ni content in the ferro nickel to 15% minimum.

Dr. M.I. Gasik, (who is known as the No. 1 scientist for manganese in the world) and his team developed lots of equipments & technologies for ferro alloy production; they improved the technical and economic values of the process and the furnace operation of the plants.

For the Indian ferro alloy industry, it is now possible to involve the world-class specialists from the National Metallurgical Academy of Ukraine, who have a treasure of knowledge and practical experience.