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. The 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 mostly (>90%) by Electric Arc Furnaces (EAF), which are submerged EAF and are in continuous operation.
We are looking for solutions to reduce the energy consumption/cost in ferroalloy production, especially, reduction in power consumed by Electric Arc Furnaces. The proposed solutions should reduce the power consumption by a minimum of 20 kWh/T (FeCr or FeMn) over a sustained period of a minimum of 3 months.
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 pursued.
- We tried sintering and pelletizing to reduce specific energy consumption due to pre-reduced charge, 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. 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.