Numerical modeling and analysis of hydrogen blast furnace ironmaking process

Abstract

Hydrogen use in the blast furnace (BF) ironmaking process promises to mitigate the carbon footprint substantially. This paper presents a numerical study on the effects of hydrogen enrichment on the inner states and overall performance of a 380-m3 industrial BF. This is done using a recently developed three-dimensional process BF model. The model is validated under different conditions. A case of 40-degree pure hydrogen being injected into the hearth tuyeres is considered. The hydrogen content in the bosh gas varies from 3% to 49.5%, while the hot metal temperature, bosh gas volume, and flame temperature are fixed. The numerical results reveal that with increasing hydrogen enrichment, the coke rate decreases initially to a minimum, then increases; however, the productivity increases and subsequently slows down. Therefore, an optimum hydrogen enrichment is identified according to the minimum coke rate. The flow and thermochemical behaviors are analyzed in detail. It shows that as the hydrogen enrichment intensifies, the cohesive zone has a narrower horizontal width and a shorter total length, contributing to a reduced tuyere pressure. The relative importance of chemical reactions at different hydrogen enrichments is also analyzed. It shows that the intensified hydrogen enrichment enhances the H2 indirect reduction and impedes the carbon solution reaction. However, it also decreases the CO indirect reduction rate that is more significant than the H2 indirect reduction rate under the conditions considered. In addition, hydrogen enrichment requires extra coke combustion to compensate for the sensible heat of the reduced hot blast rate. Overall, hydrogen enrichment improves the energy efficiency of BF.