Electric arc furnace (EAF) dust
Currently, more than half of the electric arc furnace (EAF) dust produced worldwide is still sent to landfill. This dust contains approximately 7.0% of the world Zn production. The other half of the EAF dust is processed pyrometallurgically or hydrometallurgically to recover Zn. The processing costs for EAF dust strongly depend on the Zn concentration. Therefore, several steel mills apply in-plant enrichment of Zn by recycling part of the dust back into the furnace to reduce the specific processing cost for the EAF dust and at the same time decrease the amount of dust that has to be discharged. Separation of EAF dust into size fractions by air classification showed a distinct dependence of the Zn concentration on the particle size with an enrichment of Zn in the fine size fractions and depletion in the coarse fractions. Therefore, in in-plant dust recycling, air classification of the dust could be used to reduce the amount of recycled Zn and dust but still reaching the same Zn concentration in the discharged dust. This would reduce the energy demand for Zn volatilization in the furnace and the required capacity of the dust recycling system. Highlights Size dependence of zinc concentration in electric arc furnace dust proved. Higher zinc concentration in the fine EAF dust fraction. Air classification of EAF dust improves efficiency of dust in-plant dust recycling. Lower energy consumption of in-plant recycling due to reduced number of cycles (read more) …
High grade hematite
Iron ores are rich in iron oxides and vary in color from dark grey, bright yellow, deep purple, to rusty red. The iron itself is usually found in the form of magnetite (Fe3O4), hematite (Fe2O3), goethite, limonite or siderite. The name, also spelled as Haematite, originates from the Greek word for blood ‘haima’, because hematite in powdered form can be red.
Because of its color, it is used in the pigment industry (building products and glass). Other specific characteristics makes it suitable to use in for example foundry applications (in exothermic products and as core additive) and in the welding and oil-drilling industry.
Cold briquetting iron and carbon
Cold Briquetted Iron and Carbon (CBIC) is an innovative product in direct reduction family which was introduced to iron and steel industry in the past few years.
CBIC is the compacted form of Cold Direct Reduced Iron (CDRI) which is produced in direct reduction process. CBIC has some advantages over CDRI which include higher density, higher oxidation resistance, lower water absorption and higher capability of carbon content. These advantages not only make its storage and shipment easier and more economic but also, have significant effects on steel-making process.
Experiments have shown that replacing CDRI with CBIC in charging regime of steel-making process (up to 50%) reduces dust generation, energy consumption and tap-to-tap time and improve the productivity of steel-making plant.
Hot Briquetted Iron
Hot Briquetted Iron (HBI) is a relatively new product, developed in the past 25 years, as a supplement for pig iron and scrap in electric furnace steel mills. It is a compacted form of direct reduced iron (DRI), which facilitates its handling, storage, and use.
HBI is a premium form of DRI that has been compacted at a temperature greater than 650° C at time of compaction and has a density greater than 5,000 kilograms per cubic metre (5,000 kg/m3).
HBI was developed as a product in order to overcome the problems associated with shipping and handling of DRI – due to the process of compaction it is very much less porous and therefore very much less reactive than DRI and does not suffer from the risk of self-heating associated with DRI.
The principle market for HBI is electric arc furnace (EAF) steelmaking, but HBI also finds application as a trim coolant in basic oxygen furnace (BOF) steelmaking and as blast furnace feedstock.
Direct Reduced Iron
Direct Reduced Iron (DRI) is the product of the direct reduction of iron ore in the solid state by carbon monoxide and hydrogen derived from natural gas or coal. See more information about the production of DRI. Most gas-based direct reduction plants are part of integrated steel mini-mills, located adjacent to the electric arc furnace (EAF) steel plant. DRI can be either hot or cold charged to the EAF. Some steel companies ship DRI from their captive direct reduction plants to their remote steel mills and a small volume of DRI is sold to third parties. In India there are many small rotary kiln furnaces producing DRI, known locally as sponge iron, using coal as energy and reductant source.
Iron ore pellets
Iron Ore Pellets are formed from beneficiated or run of mine iron fines. The iron is usually ground to a very fine level and mixed with limestone or dolomite as a fluxing agent and bentonite or organic binders as a binding agent. If the ore is a Hematite ore, coke or anthracite coal can be added to the mix to work as an internal fuel to help fire the pellets. This mixture is blended together in a mixer and fed to balling discs or drums to produce green pellets of size typically about 9-16mm. The green pellets are then fed to the induration machine. Both straight grates and grate kilns dry the pellets out in a drying section, then bring the pellets up to a temperature of about 800-900 °C in a preheat zone, then finish the induration process at roughly 1200-1350 °C. The pellets are then cooled to a suitable temperature for transporting to a load out facility. Both processes recycle the heat from the pellet back through the process to aid in energy efficiency and decrease fuel usage.
Both processes can be used to generate almost any type of desired pellet chemistry, from direct reduction pellets (DR pellets) to blast furnace pellets. By adjusting the amount of fluxing agent or limestone added, pellets can be made that are anywhere from acid (or non-fluxed) pellets to heavily fluxed pellets.