Abstract
In the Swedish steel industry, much work is put on further increasing the recycling and use of residual materials. However, blast furnace sludge is one residual which currently, despite its valuable contents of iron and carbon, is put on landfill or long-term storage due to its zinc content. Linde has developed the OXYFINES technique which is suitable for upgrading of fine particulate and zinc containing materials. The material is fed to the OXYFINES burner whereby its zinc content is vaporised to a generated dust phase whereas other non-gasifiable contents, such as iron, forms an oxidic sinter phase in the bottom of the reactor. The technique has proven a high degree of zinc separation, is relatively flexible and straightforward, and does not require sludge pre-treatment such as drying. Pilot set-up and trials, using the OXYFINES technique, were performed at Swerim’s research facility. In the trials, the effects from altering different process parameters were tested aiming to develop an optimal concept for upgrading the blast furnace sludge. The pilot trials’ results showed the required process settings to attain a high degree of zinc separation from the sludge, and to generate an iron oxide product, suitable for straightforward charging to the steelmaking process.
Highlights
The production of iron and steel generates a variety of residual materials such as dust, sludge, scales, and slag
Established routes for recycling in ore-based steel production are through sintering process, via injection of the blast furnace (BF) flue dust in the BF and by charging cold-bonded briquettes, basic oxygen furnace (BOF) slag and desulphurisation scrap to the BF [2,3,4,5,6]
The sinter was crushed into lumps after cooling, practically without any fines’ generation, making it a suitable product for handling, and charging to the steelmaking processes
Summary
The production of iron and steel generates a variety of residual materials such as dust, sludge, scales, and slag. New technological solutions are required for achieving higher by-product qualities and increasing their utilisation in an environmental and economic sustainable way. Established routes for recycling in ore-based steel production are through sintering process, via injection of the blast furnace (BF) flue dust in the BF and by charging cold-bonded briquettes, basic oxygen furnace (BOF) slag and desulphurisation scrap to the BF [2,3,4,5,6]. The Nordic sintering plants have been closed due to environmental issues whereas the recycling of in-plant fines in Swedish ore-based steel production is mainly by BF flue dust injection and via cement-bound briquettes charged to the BF. The BF briquettes consists of a variety of iron-, carbon- and lime-containing residual materials
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