Ferroalloys Manufacturing is a highly power-intensive process. Power cost contributes to more than 30% of the cost of production of Ferro Alloys. We are looking for solutions for reducing specific smelting power consumption in ferroalloy production.
Ferroalloys are alloys of iron and one or more alloying elements such as Chromium, Manganese, Silicon & Nickle etc. Ferroalloys are used as master alloys in the iron and steel industry to improve the properties of steel, especially the tensile strength, wear and corrosion resistance of steel.
In our plant, we make Ferro-Chrome (FeCr) and Ferro-Manganese (FeMn) alloys. Electric Arc Furnaces (EAF) are used to make these alloys from raw materials. The overview of the ferroalloy production process is shown in fig 1, and a typical electric arc furnace is shown in fig 2.
Ferroalloy production is an energy-intensive process. Energy needed per ton varies depending upon the product. For FeCr around 3.52 MWh/T FeCr is required while in case of High Carbon FeMn the requirement is around 2.76 MWh/T FeMn.
The energy in ferroalloy production is consumed by (i) Electric Arc Furnace and (ii) Auxiliary equipment. The auxiliary equipment comprises of conveyors, blowers, cranes, slag handling and other miscellaneous equipment. The Electric Arc Furnaces are submerged Electric Arc Furnaces (EAF) and are in continuous operation.
In terms of energy consumption, the auxiliary equipment energy consumption usually ranges from 3-8% and the remaining energy, around 92 – 97%, is consumed by the Electric Arc Furnace. Power cost contributes more than 30% of the cost of production of Ferro alloys. The problem aggravates when the unit rate of power supplied becomes very high (more than around Rs. 7/kWh), in such cases the operation of these units becomes unviable.
We are looking for solutions to reduce the energy consumption in ferroalloy production, especially, reduction in power consumed by Electric Arc Furnaces.
Solutions for the reduction in energy consumed by auxiliary equipment can be proposed. However, unless the proposed solutions, result in the reduction of specific power consumption from the existing levels (3.55 MWh/TFeCr and 2.765 MWh/TFeMn) by a minimum of 20 kWh/T (FeCr or FeMn) over a sustained period of a minimum of 3 months, the proposed solutions will not be considered. Our main objective is to explore solutions to reduce the power consumption of Electric Arc Furnaces; therefore, solutions addressing this requirement are desirable.
We have tried the following options earlier:
- Technical studies were conducted on using Copper contact clamps, bus bars and other power transmitting devices instead of Brass (85/15). This option was not feasible as the replacement was expensive.
- Preheating of feed material by exhaust gas of the furnace was tried. This option was not pursued because of high Capex, space constraint and the need for modification in the existing setup.
- Using Solar energy to preheat the feed material and to augment the electricity supplied to Electric Arc Furnaces, however as the continuous supply of solar power was not possible, it was not reliable.
- Use of sintering and pelletizing processes, to reduce specific energy consumption due to pre-reduced charge, were tried. But the reduction in power consumption was not significant.
- Pre-treatment (of coke and lumpy ore in the feed material) with lime-based additives was tried expecting to reduce power consumption. However, the results were not encouraging.
The proposed solutions should meet the following requirements:
- It should be economical.
- The footprint should not be large.
- It should not necessitate any major technical modifications in the existing setup.
- The solutions focusing on the methods mentioned above (options tried section) will not be considered.
- It should not require conducting trials while the production is in progress.
- It should meet all the safety and environmental norms of our plant.
- The solution implementation shall be considered successful only if there is a reduction of specific power consumption from the existing levels by a minimum of 20 kWh/T (FeCr or FeMn) over a sustained period of minimum three months.