Lab-scale experimental demonstration of Ca[sbnd]Cu chemical looping for hydrogen production and in-situ CO₂ capture from a steel-mill

In the present work, a lab-scale packed bed reactor has been used to decarbonize mixtures of inlet gases simulating the typical composition of blast furnace gases (BFG) and convert them to H₂-rich streams by means of the Ca[sbnd]Cu chemical looping concept. The reactor was packed with 355 g of Cu-based oxygen carrier (OC) supported on Al₂O₃ and natural Ca-based sorbent. The three main reaction stages; namely (i) Calcium Assisted Steel-mill Off-gas Hydrogen (CASOH), (ii) Cu oxidation and (iii) Regeneration of carbonated Ca-based sorbent were examined. In CASOH stage, BFG is converted into H₂-rich stream (17% by vol.) under the experimental conditions of 600 °C, 5.0 bar and S/CO molar ratio of 2.0. A controlled oxidation causes a mere 3.5% of CaCO₃ to decompose during the Cu-oxidation stage. This resulted in a nearly pure N₂ stream at 600 °C and 5.0 bar operating conditions. During the regeneration stage, BFG and mixture of BFG and CH₄ is used as a reducing fuel. To ensure the amount of heat needed for the decomposition of CaCO₃ during the reduction of CuO, a 1.4 CuO/CaCO₃ molar ratio has been used. It resulted in 46% CO₂ in N₂ at the end of the reduction/calcination stage.