CO2 Sequestration Using a Novel Na-salts pH Swing Mineral Carbonation Process

AbstractThe main drawback of the indirect pH swing carbonation processes proposed so far is linked to the large amount of energy required to recycle the chemicals used to accelerate the reactions. The dissolution and carbonation steps of an alternative mineral carbonation pH swing process that employs sodium-based salts has been studied in order to minimize energy requirements typically associated to ammonium based mineral carbonation processes. The dissolution carried out at 70°C using NaHSO4 gave Mg extraction efficiency comparable to that of NH4HSO4 with about 50% of Mg brought into solution as MgSO4. In addition, the carbonation experiments (90% efficiency) demonstrate that NaHSO4 and NaOH can be used in a combined process to mineralize CO2. The feasibility of the other process steps and optimization of the dissolution and carbonation are discussed

An overview of current status of carbon dioxide capture and storage technologies

AbstractGlobal warming and climate change concerns have triggered global efforts to reduce the concentration of atmospheric carbon dioxide (CO2). Carbon dioxide capture and storage (CCS) is considered a crucial strategy for meeting CO2 emission reduction targets. In this paper, various aspects of CCS are reviewed and discussed including the state of the art technologies for CO2 capture, separation, transport, storage, leakage, monitoring, and life cycle analysis. The selection of specific CO2 capture technology heavily depends on the type of CO2 generating plant and fuel used. Among those CO2 separation processes, absorption is the most mature and commonly adopted due to its higher efficiency and lower cost. Pipeline is considered to be the most viable solution for large volume of CO2 transport. Among those geological formations for CO2 storage, enhanced oil recovery is mature and has been practiced for many years but its economical viability for anthropogenic sources needs to be demonstrated. There are growing interests in CO2 storage in saline aquifers due to their enormous potential storage capacity and several projects are in the pipeline for demonstration of its viability. There are multiple hurdles to CCS deployment including the absence of a clear business case for CCS investment and the absence of robust economic incentives to support the additional high capital and operating costs of the whole CCS process

CO₂ conversion into valuable fuels using chromium based supports

AbstractCO2 utilization by direct catalytic conversion of CO2 driven by solar energy is an attractive approach for producing alternative value added products suitable for end-use infrastructure. In order to fully harness the solar spectrum and increase photocatalytic activity and selectivity, Cr-TiO2 based films were deposited on ceramic honeycomb monoliths with varying concentrations synthesized by sol-gel technique and dip coating route. The improved photocatalytic activity of the Cr-TiO2 monoliths in the visible light region compared to pure TiO2 can be attributed to increased visible light absorption and accessible active metal sites arising from the appropriate metal dispersion and loading amount

Mass and energy balance of NH4-salts pH swing mineral carbonation process using steel slag

AbstractA basic evaluation of the entire NH4-salts pH swing mineral carbonation process steel slag based system including CO2 capture, ammonia absorption and regeneration of additives, has been investigated to evaluate its feasibility at industrial scale.Heat released from mineral dissolution, pH adjustment and precipitation of impurities, carbonation reaction and CO2 capture was2.3 MWh/tCO2 and could be recovered using heat exchangers and reused within the mineralization process to heat-up the incoming streams of steel slag, ammonium sulphate and water. Heat required, mainly from water evaporation and regeneration of additives, is reported to be 20 MWh/tCO2

Mineral carbonation from metal wastes: Effect of solid to liquid ratio on the efficiency and characterization of carbonated products

AbstractMineral carbonation technologies aim at permanently storing CO2 into materials rich in metal oxides. A multi-step mineralization process employing Ca-rich waste streams to precipitate calcium carbonate is investigated in this paper. Ground granulated blast furnace slag (GGBS), phosphorus slag (PS) and steel slag (SS) were employed as feeding materials for the process. Solid to liquid ratio (S/L) is an important factor which affects mineral carbonation and this study examines its effect on the carbonation efficiencies. The main phases present in the carbonated residues were identified using XRF, XRD and SEM–EDS analytical techniques. For the three materials investigated, the carbonation efficiency increased when the S/L ratio decreased (from 50g/L to 25g/L and then 15g/L) because of the dilution effect. In a previous study, where an analog process was employed, efficiency using serpentine was found lower than that calculated here for GGBS and SS, and slightly above PS. This confirms that, in general, waste materials require less energy-intensive carbonation conditions, in comparison to mineral rocks. Finally, the structure of the carbonated particles is also discussed