The challenge
During BOF (Basic Oxygen Furnace) and AOD (Argon Oxygen Decarburization) steelmaking, high-energy oxygen blowing generates significant volumes of particles captured by gas-cleaning systems, forming sludge (when water is used for gas cleaning) or forming dust (when electrostatic precipitators are used).
These residues are rich in iron (metallic and oxide forms) and alloying elements (such as chromium and nickel when stainless steel is manufactured), yet around 4% in weight from crude steel production is lost as fine particulate. As an example, a 5 million tons/year steel mill generates around 200 thousand tons/year of sludge or dust. The residue contains large amounts of steel particles, iron oxides and alloys but also contaminants such as zinc and alkalis — leading to landfill disposal and, consequently, raw-material leakage.
The total particle mass is around 4% of the steel produced in the BOF & AOD.
Each steel mill has its own gas cleaning type: wet system (A) or dry system (B).
Thickener
Fine Sludge
~70% of Total
~30% of Total
Akins Spiral Coarse Sludge
Akins overflow
Electrostatic
Precipitator
Coarse ESP Dust
~25% of Total
Fine ESP Dust
~75% of Total
HpM’s solution
HpM developed a proven circular recovery technology that selectively separates metallic steel from oxide fractions, reducing contaminants to acceptable levels, transforming steelmaking residues into process-ready materials to be used in the steel mill.
Segregated and cleaned metallic iron (steel) isolated from coarse sludge or dust is transformed into non-binder briquettes, named BAP Steel (Portuguese acronym for Pure Steel Briquettes). BAP Steel can be directly reintegrated into BOF or AOD operations, as first-quality steel scrap.
The oxides removed from the coarse sludge or coarse dust, during BAP Steel production, are joined to the thin sludge and then submitted to a fine particle disaggregation process. HpM's process can reduce excess lime, zinc and alkalis while concentrating the iron oxide and other metallic alloys. The cleaned oxides are then conditioned and agglomerated (into briquettes or pellets according to customer preference) and named ACO Iron (Portuguese acronym for Oxide Circular Agglomerate). The ACO Iron has high-value use within the steel plant as an iron charge to blast furnaces or as a cooling metallic charge in steelmaking.
The mass balance below shows HpM's technology results for BOF & AOD gas cleaning system particles.
ACO Iron Pellets
BOF or AOD Blowing Process
Particles Generation
Off-Gas Cleaning System
(A) Water Cleaning Process - Sludge Formation
(B) Electrostatic Precipitator - ESP Dust Formation
Sludge and ESP Dust Formation During BOF and AOD Operation
BAP Steel
HpM BOF & AOD Sludge / Dust Regeneration Mass Balance
(Example of a 5 million ton/year carbon steel mill)
Byproduct
Fine Sludge/Dust
(70% of total sludge)
(140.000 ton/year)
Coarse Sludge
(30% of total sludge)
(60.000 ton/year)
BOF / AOD
Magnified Illustration of the Particulates
TOTAL SLUDGE
(~4% of crude steel production)
(200.000 tons of sludge/year)
RECOVERED PRODUCTS
BOF & AOD Sludge / Dust
(183.000 tons of product/year)
BAP Steel
(39.000 ton/year)
ACO Iron
(144.900 ton/year)
Oxides from Corase Sludge
(21.000 ton/year)
Corase sludge isolated and briquetted steel
(85 - 93% metallic)
(39.000 ton/year)
Conditioned Fine Sludge
(up to 62% total Iron)
(123.900 ton/year)
zinc, alkalis, lime
(16.100 ton/year)
GROSS REVENUE POTENTIAL
Based on Average Historic Price
(LME* Scrap / MMI **Fe62% Ore Fines)
LME Scrap USD/Ton: USD378.00
BAP Steel Ton/Year: 39,000.00 Ton
Annual Value Recovered: USD 14,742,000.00
Iron Ore Pellets Fe 62% USD/Ton: USD125.00
ACO Iron Ton/Year: 144,900.00 Ton
Annual Value Recovered: USD 18,112,500.00
Coarse and Fine Sludges/Dust
Total Gross Revenue Potential
BAP Steel + ACO Iron
USD 32,854,500.00 / Year
Zinc Recovery or Construction Use
Resilience & Price Competitiveness through Residues Recovery
This resilience is measurable — strengthening price competitiveness through internally regenerated raw materials, grounded in a proven and fully operational circular economy approach.
What emerges is not a concept, but a practical and profitable business model — validated in real steelmaking operations.
And while carbon steel already demonstrates compelling results, stainless steel producers unlock an even higher value horizon, where the recovery of premium raw materials amplifies both economic and strategic returns.