Lab-Scale Experimental Demonstration of Ca-Cu Chemical Looping for Hydrogen Production and In-Situ Co2 Capture from a Steel-Mill

Abstract

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-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 the first stage CASOH, calcium assisted water gas shift reaction converts the BFG 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. The oxidation of Cu is highly exothermic, but, 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 under the operating conditions of 600 °C and 5.0 bar. 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 using simulated BFG and CH4, a CuO/CaCO3 molar ratio of 1.4 has been used. It resulted in 46% CO2 in N2 at the end of the reduction/calcination stage.

Keywords: CO2 capture, steel mill, blast furnace gas, chemical looping combustion, calcium-cupper looping