Iron-based chemical-looping technology for decarbonising iron and steel production

The application of iron-based chemical-looping processes offers an efficient and convenient strategy for decarbonising iron and steel production. Here we present a novel chemical-looping with water splitting process for the co-generation of hydrogen and a saleable, reduced iron product (CLWSFe). The high-purity H-2 stream provides a decarbonised fuel source for producing direct reduced iron (DRI), and the spent oxygen carrier, OC (if removed in reduced form) is a source of iron that could be blended with the DRI for casting or further processing to steel. A fully heat integrated model of the CLWSFe process developed in ASPEN-PLUS is presented. The thermal and exergy efficiencies of the optimised process were studied and compared with a conventional steam-methane reforming (SMR) process. An assessment of the economic feasibility based on CAPEX, OPEX and the production cost of hydrogen was carried out. The added value associated with the reduced iron (spent OC) product and its effect on the process CAPEX and OPEX was considered. The effective efficiency of the CLWSFe process was 20.8% higher than a conventional SMR process with the advantage of producing a saleable Fe product. The hydrogen production cost was 1.16 $/kg-H-2. The multicycle performance of different iron ores and steel production residues supplied by Nippon Steel Corporation were also studied in a thermogravimetric analyser at conditions relevant to both conventional chemical-looping combustion and CLWS processes. Kinetic and cyclic performance data provided useful inputs for the model assisting with reactor sizing and the estimation of oxygen carrier replenishment rates.