Carbon Capture in Molten Salts A new process for CCS based on Ca-looping chemistry Summary Espen Olsen a, Viktorija Tomkute a, Asbjørn Solheim b a Dep. Mathematical Sciences and Technology, UMB, N-1432 Ås, Norway b Dep. Energy Conversion and Materials, SINTEF Materials and Chemistry, N-0314 Oslo, Norway Carbon Capture in Molten Salts (CCMS) has been demonstrated on the laboratory scale. Absorption of CO 2 from a simulated combustion gas is shown to exhibit extremely efficient characteristics, absorbing up to 99.97% of CO 2 from a simulated flue gas in a reactor column of 10 cm length. Desorption proceeds to 100% so all CaO is regenerated in reactive state overcoming the main challenge in conventional Ca-looping. If the process characteristics are scalable to larger scale reactors exhibiting similar efficiency, selective capture and release of CO 2 from a wide range of gas compostitions is possible. This opens for a large number of applications. Introduction and Theory Experimental Conclusions and further work Results The Ca-looping principle 1 relies on displacement of the equilibrium described by Eq.(1) (M denotes an alkaline-earth metal) by thermal cycling at elevated temperatures ( °C). This minimizes fundamental losses due to low temperature waste heat. The process is performed in FBR-reactors and is being developed on the demonstration scale 2. The main obstacles for successful commercial implementation is deactivation of CaO powders by decomposition and sintering introduced by thermal cycling. A dedicated laboratory set up involving a high- sensitivity FTIR gas analyzer and TGA functionality is used. A simulated flue gas (0- 100% CO 2 in N 2 ) is fed to a 10 cm column of molten salt containing CaO. The gas composition before and after absorption is analyzed with high accuracy References: 1 Chem. Eng. Res. Des. 89, (2011), Norwegian patent No Figure 1: The Gibbs free energy of reaction (1) vs. temperature and alkali-earth cation. Figure 3: Details of the reaction chamber. Outer sleeve of steel, inner crucible and feed tube of Ni. Figure 2: The experimental setup, schematically depicted. The absorption-desorption processes are monitored by gravimetry (TGA) and mass balance by gas analysis (FTIR). The CCMS idea: By (partly) dissolving the active substances in a supersaturated molten salt, highly reactive absorbing CaO is constantly regenerated as described by Eq.(2). (M denotes an alkaline-earth metal) The CCMS project aims at: To develop a new and patented process for carbon capture. 3 Establish the scientific foundation for industrialization. Time frame: 5-10 years. Figure 5: Repeated absorption-desorption cycling (4x, 800°C/950°C) from a simulated flue gas (N 2 +27% CO 2 ) in a chloride based absorbing liquid (CaCl 2 +5%CaO). The content of CO 2 in the gas emitted is shown in the bottom panel while the mass of the reaction vessel () as well as temperature () is shown in the top panel. Figure 6: The conversion efficiency of the cycling between CaO and CaCO 3 during absorption ( ) and desorption ( ) in each of the cycles from Fig.5. The decarbonation of CaCO 3 by forming CaO and CO 2 is reaching 100% efficiency in all the cycles while the conversion of CaO to CaCO 3 during absorption shows a rising trend with each cycle, contrary to the loss in reactivity experienced in solid state Ca-looping. Figure 7: Absorption with subsequent desorption of CO 2 from a simulated flue gas (N 2 +27% CO 2 ) in a fluoride based liquid (NaF/CaF 2 /10% CaO) at 820°C. Desorption at 1150°C. The content of CO 2 in the gas emitted from the reactor () and temperature (). The CCMS process works as predicted from fundamental thermodynamic modeling. 5 cycles has been completed with 100% conversion efficiency from CaCO 3 to CaO. The present results are promising indicating the potential for CCS from a wide variety of gas compositions from different sources. Focus will be now be directed towards construction of a lab pilot reactor for continous operation (1) (2) Figure 4: Schematic set up of a pilot scale reactor for continous operation.