Abstract
Material efficiency is one of the most effective methods for achieving more sustainable operations in iron and steelmaking. Sintering and briquetting processes are commonly used in integrated steel plants to recycle carbon- and iron-containing residues back to blast furnace. In the Ruukki steelworks in Finland, a surplus of solid coking plant by-products is produced, none of which are presently utilized within the steelworks. In this paper, a novel concept for recycling solid coking plant by-products to a blast furnace via liquid-solid injection is evaluated. According to the conducted laboratory study, all the solid by-products could be utilized via liquid-solid mixture injection. By pulverizing the coke gravel and coke sand and mixing it with extra heavy bottom oil, the annual coke requirement of a blast furnace could be decreased by almost 9% with constant oil injection and could reduce annual oil requirements by almost 39% with constant coke rate. Evaluation of direct and indirect environmental impacts reveals that there would be more positive than negative impacts when recycling solid coking plant by-products inside steel plant boundaries.
Highlights
Material efficiency has been identified as one of the key issues in steel production with respect to minimizing the need of virgin raw materials, reducing waste and saving energy
A number of residues are produced inside the system boundaries, some of which are utilized inside the steel work unit processes
Beside the above-mentioned measures to recycle internal carbonaceous materials, this paper proposes a liquid-solid injection practice that could further increase the use of carbonaceous by-products inside steel plant
Summary
Material efficiency has been identified as one of the key issues in steel production with respect to minimizing the need of virgin raw materials, reducing waste and saving energy. A majority of steel today is produced by using the integrated blast furnace–basic oxygen furnace (BF-BOF) route where iron oxides are reduced and melted into hot metal in BF and refined into steel in BOF [1]. Some integrated steel plants have their own coking plants which produce coke for use as a blast furnace reducing agent. Integrated steel plants are complex entities with crossing material and energy flows. A number of residues are produced inside the system boundaries, some of which are utilized inside the steel work unit processes. Sintering, which is a unit process to agglomerate iron ore fines in high temperature, has been traditionally used to refine many of the solid residues produced inside the system boundaries [2,3]
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