Recycling of coking plant residues in a finnish steelworks-laboratory study and replacement ratio calculation

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.