Replacing coke in the iron-and steel-making process is important issue in terms of sustainable operation and operating costs reduction. Previously, coke was partially replaced by pulverized coal injection technique. Recently, these attempts have been made for natural gas, hydrogen, and waste plastics.
In this study, we found unique application to replace coke by utilizing the off-gas generated in the blast furnace, i.e., BFG. We tried to separate carbon monoxide (approximately 20% contained in BFG) from the blast furnace gas and recycle it. In order to evaluate the feasibility of the proposed process, (1) a vacuum-pressure swing adsorption (VPSA) process, and (2) a blast furnace process model were developed.
For the separation process, an alumina-based adsorbent was developed to effectively purify a large amount of nitrogen components (> 50%) contained in the BFG. In the case of the blast furnace model, a model was proposed to predict the amount of coke that can be reduced when the separated carbon monoxide is injected. In particular, the blast furnace model includes 57 variables, which can reflect (1) all fuel components (sintered ore, pulverized coal, flux, oxygen enrichment, water injection, etc.) and (2) pig iron and blast furnace slag components.
Based on this, it was possible to explore the practical applicability of replacing coke, and it was also possible to estimate additional carbon dioxide reduction by the BFG recycling.
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