The Calcium Assisted Steel-mill Off-gas Hydrogen production process (CASOH) is able to upgrade and decarbonise blast furnace gases (BFG), which is the main source of CO2 emissions in integrated steel making plants. The three main reaction stages of the process (i.e. H2 production via calcium-assisted water-gas-shift of BFG, Cu oxidation and CO2 sorbent regeneration) have been investigated in a lab-scale fixed bed reactor, using readily available functional materials (i.e. a commercial Cu-based catalyst and calcined limestone for the CO2 capture). The reactivity and stability of the materials have been studied after multiple cycles resembling the operating conditions expected in a TRL7 CASOH pilot plant under construction. A one-dimensional reactor model has been developed to simulate in detail the CASOH process and successfully validated with the experimental results obtained in the packed-bed reactor. Synthetic BFG mixed with steam has been converted into a product gas containing up to 40 vol% of H2 in N2 during the CASOH stage at atmospheric pressure and average temperatures in the bed around 650 ºC. During the Cu oxidation stage, the O2 contained in inlet air has been completely converted leading to moderate temperatures in the oxidation front (i.e. around 800 ºC).
The oxidation at 4 bar has minimized the CO2 leakage during this stage. Finally, the reduction of CuO with simulated BFG and CH4 has produced in-situ sufficient heat to partially calcine at temperatures around 880ºC the CaCO3 present in the reactor leaving the solids ready for subsequent reaction cycles, while a CO2-rich gas is produced. The experimental and modelling results obtained in this work will be used to firstly design the experimental campaigns at the TRL7 CASOH pilot, and subsequently to interpret and scale up the pilot results using the validated model.
Authors: G. Grasa, M. Díaz, J.R. Fernández, A. Amieiro, J. Brandt, J.C. Abanades