Utilization of industrial waste for value-added permanent sequestration of CO2
Mineral carbonation allows to permanently store CO2 into materials rich in metal oxides. However, mineralization technologies still suffer of slow reaction rates and low carbonation efficiencies and, to improve them, there has been increasing interest in employing waste streams as feedstocks. In light of this, the aim of this thesis was to determine the potential use of wastes for permanent sequestration of CO2. It was found that waste streams available for mineral carbonation in the UK have a capture potential of 1Mt/year, and in many cases, waste resources are located close to the CO2 emitters. A novel closed-loop, multi-step mineralization process was developed. The process consists of extracting calcium from the feedstock followed by its precipitation as crystals of calcium sulphate, which are then converted into calcium carbonate. Carbonation efficiency of the process increased when temperature was raised and solid to liquid ratio and particle size reduced. A 74%, 67% and 59% of carbonation efficiency was achieved for steel slag, ground granulated blast furnace slag and phosphorus slag, respectively. Finally, a real case scenario, where the mineralization process would be retrofitted to a steel plant, was investigated. It was found that, because of the thermal and electrical energy required to run the process, the mineralization system would be carbon negative (i.e. storing more CO2 than the amount emitted during the process) when the solid to liquid ratio would be 240g/l or higher.