Use of HBI in EAF (Electrical Arc Furnace)
Production of Steel in Electrical Arc Furnace (EAF) is growing worldwide. Also, the supply and use of Pig Iron, Sponge Iron (DRI) and HBI in the EAF have been increasing during the last 5 years.
- Hot Briquetted Iron (HBI) is not a scrap substitute but rather a source of clean iron units that could be used to additive and boost the scrap charge.
- HBI has high iron (Fe), low metallic residual for the production of high-quality iron and steel products in different varieties of furnaces.
- The net worth of Hot Briquetted Iron is varied for different melt shops and depends on the local steel scrap supply, production equipment, metallurgical practice as well as steel product mix
Use of HBI in BOF (Basic Oxygen Furnace)
The usage of HBI is advised for the following situations:
- When the ratio of used hot metal and scrap ends in overheating at the last step of
- the blowing process (using Hot Briquetted iron as a coolant makes the required temperature with no need of a cooling process)
- When iron ore is applied as the cooling agent owing to the lack of scrap (that reduces
productivity).
- When scrap is not available.
- When the charge material Sulphur content needs to below.
- When the content of residual requires to be low.
The Benefits of using HBI in BOF
HBI provides an optimum charge to the Basic Oxygen Furnace because of:
- Low levels of residual elements
- Bulk density of 2.8 t/m3 – more than scrap’s
- Metallic yield as same as hot metal
- More heat balances & predictable mass
HBI is an excellent trim coolant due to the following characteristics:
- Free-flowing from the upper baskets
- Certain physical and chemical specifications
- Maintains finished steel composition
- Charges easily from overhead baskets.
- Fast penetration of slag
- Decreases slag volume when it is used instead of fluxes
- Higher yield and productivity compared to while with conventional coolants
Use of HBI in Blast Furnace (BF)
HBI is used as the blast furnace burden material with the following advantages considering the environment, productivity and cost:
- lower emission of CO2
- increased-productivity of BF (an increase of around 8% per each 10% increase in burden metallization)
- reduced rate of coke (decrease of around 7% per each 10% increase in burden metallization).
Why Charging of HBI into the Blast Furnace (BF)?
Different circumstances in which HBI is included in the BF burden will have a positive economic side effect:
- the capacity of Coke production is limited and the investment on coke ovens is not workable.
so, the factory needs to decrease the exact coke consumption.
- Purchased coke is used, but the price is high enough to make it possible to reduce the coke consumption to equal higher cost while adding HBI to the BF burden.
- among several BF’s, one BF needs to be re-lined, therefore it is required to increase the production of hot metal from the remaining BF’s to reduce losses of downstream production.
- There is an imbalance between the quantity required for hot metal and BF capacity: three BF’s
are operated in the factory while the hot metal output of 2-3 BF’s would be adequate. Thus, it would be cost-effective to operate 2 BF’s at a somehow higher hot metal cost to enhance the production of downstream equipment.
Under these conditions, the increase in the cost of hot metal feedstock because of adding Hot Briquetted Iron (HBI) to the BF burden could be justified based on the steel production increase, higher productivity of BF and coke consumption reduction. HBI properties for the usage of BF could be less stringent than of EAF steelmaking since high levels of SiO2, FeO and Sulphur and also lower metallization are tolerable in the BF.
Source: IIMA – www.metallics.org
