Serpentine and single stage mineral carbonation for the storage of carbon dioxide

Abstract: Mineral carbonation is the formation of stable calcium, magnesium, and iron carbonates from the reaction between the metals in common minerals and carbon dioxide. The benign and longterm nature of this CO2 sequestration option has led to ongoing research efforts. Magnesium silicates such as olivine and serpentine have been the focus of mineral carbonation research for the sequestration of CO2 for over a decade. The aqueous carbonation route has received more attention over simpler solid-gas reactions due to reaction kinetics and carbonation conversion efficiencies. However, the removal of magnesium from the magnesium silicate matrix remains as a challenge for the aqueous carbonation scheme. Strong acids such as sulfuric and hydrochloric acid have been used to improve upon the rate limiting step of magnesium removal. Although the use of an acid-accelerating medium can improve the reaction kinetics and reduce the reaction pressures and temperatures, it requires an additional step. Reagents are required to raise the pH to support carbonation, therefore imparting costs to the reaction process that, to date, are prohibitive. Our preliminary investigations have demonstrated that serpentine has the intrinsic ability to buffer against the acidic conditions resulting from the dissolution via carbonic acid, while leaching magnesium into solution for subsequent carbon storage

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 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

Monitoring techniques of a natural analogue for sub-seabed CO2 leakages

Carbon dioxide sequestration in sub-seafloor aims to store CO2 inside geological trapping structures below the seafloor. However there are concerns related to the possibility of leakage from the storage sites and potential consequences on the marine environment. In order to develop safe and reliable methods for CO2 monitoring, field studies were conducted in a natural analogue–an area where there is a natural release of CO2 from the seafloor. Due to the very high volume of gas emitted, this natural analogue could be considered as the worst-case scenario for a possible leakage from a sub-seabed storage site. Sampling procedures for free and dissolved gas and measuring techniques of the main physical and chemical parameters were developed for use both from the surface and directly underwater by scientific scuba divers. The first results of the research indicate that high levels of CO2 released in the marine realm strongly affect the local environmental conditions with a generalized acidification of the seawater. The experience gained in this study allows further development of a more accurate and suitable monitoring suite that will integrate sensors for measuring pH, dissolved CO2, and eventually, acoustic systems for the detection, monitoring and quantification of gas bubbles. The monitoring system could be deployed on the seafloor for long-term monitoring or could be carried onboard movable platforms such as ROV’s (Remote Operated Vehicles) or AUV’s (Autonomous Underwater Vehicles) for systematic surveys of the sub-seabed storage areas

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