(589a) Biomass-Driven Chemical Looping Process for Carbon Neutral Ironmaking with Inherent CO? Capture

Achieving net-zero carbon emissions by 2050 requires urgent decarbonization of the ironmaking industry, which currently accounts for 7% of global greenhouse gas emissions. This sector plays a significant role in climate change, making it imperative to implement cleaner technologies. The dominant iron production method, the MIDREX process, relies on syngas—composed mainly of carbon monoxide (CO) and hydrogen (H₂)—produced through natural gas reforming for direct reduction of iron (DRI). However, a major drawback of this process is that the off-gas from the shaft furnace is combusted to supply heat to the reformer, leading to carbon dioxide (CO₂) emissions. While the MIDREX process employs acid gas removal technology to capture CO₂, this approach is highly energy intensive. A more sustainable alternative would integrate an efficient carbon capture method with renewable and carbon-neutral syngas production, such as utilizing biomass, to enable fossil-free iron manufacturing.

Ohio State University (OSU) has developed a moving bed chemical looping technology that leverages biomass to generate syngas, making it a promising candidate for integration with DRI. This approach offers multiple advantages, including eliminating the need for costly investments in tar reformers and air separation units. Additionally, the moving bed reactor design, coupled with the catalytic properties of oxygen carrier (OC) particles, ensures the complete conversion of biomass char. The proposed process integrates off-gas from the DRI plant into the chemical looping system, resulting in a CO₂ stream that is ready for sequestration while also producing high-purity syngas from carbon-neutral biomass, which can serve as a reducing agent in the DRI process.

The proposed system consists of three interconnected reactors. First, off-gas from the DRI plant is introduced into moving bed reactor 1, where it reacts with iron-based oxygen carrier particles, yielding sequestration-ready CO₂. The partially reduced oxygen carriers then proceed to moving bed reactor 2, where they undergo further reduction and contribute their lattice oxygen for the gasification of lignocellulosic biomass, generating high-purity syngas. Finally, the fully reduced oxygen carrier particles enter a third reactor, a fluidized bed combustor, where they are regenerated using air. These regenerated particles are then circulated back to reactor 1 via a riser, completing the chemical looping cycle.

This process was modeled in Aspen Plus and experimentally validated using a 2.5 kW thermal bench-scale setup, followed by a techno-economic (TEA) and life cycle analysis (LCA) . Process simulations confirmed that reactor 1 effectively captures CO₂ from DRI off-gas while reducing oxygen carrier particles, producing a CO₂ stream with a purity exceeding 95%. Meanwhile, reactor 2 facilitates biomass conversion at high temperatures, yielding syngas with a purity greater than 90%. A TEA comparing the conventional MIDREX process with OSU’s chemical looping system revealed that the levelized cost of production (LCOP) in OSU’s process is approximately 14% lower. This cost reduction underscores the economic feasibility of the technology, highlighting its potential for industrial-scale adoption.