Simplified sulfur-iodine cycle process to hydrogen blast furnace: Techno-economic and CO2 mitigation analysis

Abstract

In iron-making plants, the carbon emission problem is significant, and the existing reduction strategies focus on hydrogen utilization. Among the hydrogen production processes, a sulfur-iodine (SI) cycle is one of the most competitive candidates and there is a potential for the modification of the process design specifically targeted for the applications on blast furnaces (BF). We suggest a design for the SI process to produce H2 gas for use as a reductant in the BF during iron smelting. We first validated the conventional SI process by using a commercial process simulator with plant data and simplified the process to increase energy efficiency, profitability, and CO2 mitigation. We calculated the energy efficiency of the various process designs and derived the unit production cost of H2. We discussed the economic feasibility of the SI process in BF applications and showed the potential to mitigate global warming. The energy efficiency of the conventional SI process was estimated to be 32% and was increased to 38% by excluding a sulfuric acid decomposer. The unit production cost was estimated to be 1.22US$ kgH2−1 for the conventional SI process, and 0.80US$ kgH2−1 for the modified SI process of sulfuric acid co-production. The economic feasibility of the SI/MSI cycles was confirmed with a calculation of an internal rate of return and net present value. Also, generated H2 was utilized as an alternative fuel in BF, with an expected coke-replacement ratio of 0.168–0.232kgCoke mH2−3, and for the environmental prospects, an annual reduction was expected to 1077ktCO2-eq in the hot metal production scale of 3.8 Mt y−1.