CaCO3 decomposition enhanced by dielectric barrier discharge plasma – the effect of plasma-catalysis
Guido Giammaria is a PhD student in the research group Catalytic Processes and Materials (CPM). His supervisor is prof.dr.ir. L. Lefferts from the Faculty of Science and Technology.
Nowadays, there is much focus on reduction of CO2 emissions in order to contain the increase of the average global temperature. The goal to become a carbon-neutral society before 2050, combined with the ever increasing energy demand per capita, requires a radical change in the energy supply, towards renewable electrical energy (e.g. solar and wind) instead of fossil fuels (e.g. coal and natural gas). As the availability of wind and solar is intermittent, e.g. in day/night and seasonal cycles, and because distribution of availability of wind and solar over the globe does not match local demand, storage and transport of energy is becoming increasingly essential for the energy transition. Electrical energy cannot be stored directly in amounts required for seasonal cycles, nor can it be transported efficiently over large distances. Hence conversion to handier forms is required, e.g. to liquid or gaseous chemicals and fuels.
Non-thermal Dielectric Barrier Discharge (DBD) plasma is a new technology for energy storage, converting electrical energy to fuels. The amazing properties of such a plasma is the fact that energy can be directed directly to bonds to break, e.g. C-O bonds in CO2, without the need to heat the gas. In other words, the temperature is not equilibrated with the large energy input to the C-O bond; hence the term non-thermal or non-equilibrium plasma. DBD plasma can be applied at atmospheric pressure and combined with catalysts, which is interesting for large scale applications. Very promising results have been obtained for CO2 conversion into CO, methane or methanol, resulting in CO2 abatement as well energy storage.
Our research addresses the application of DBD plasma to exisitng technology for CO2 separation from flue gases, the Calcium Looping Cycle (CLC). It consists in capturing the CO2 on-stream by calcium oxide, forming CaCO3, at relatively mild temperatures of ca. 600°C. Once saturated, the CaCO3 must be decomposed separately to allow recycling, but the high temperatures required for the decomposition, ca. 900°C to obtain a pure CO2 stream at 1 bar, compromise the material stability.
The goal of this work is to assess the effect of DBD plasma on the decomposition of calcium carbonate in terms of 1) decrease of the decomposition temperature and 2) conversion of CO2 in CO in situ. The role of plasma is assessed by distinguishing between thermal effect (i.e. increase of temperature) and other effect, either physical or chemical. Different plasma compositions are tested: first a pure physical plasma made of argon, then chemically reactive plasma with hydrogen or steam.
Unfortunately, DBD plasma doesn’t have any effect on the decomposition temperature, regardless of the composition. Nevertheless, DBD plasma allows in situ CO2 conversion to CO, which is accelerated in presence of hydrogen and calcium oxide via a plasma-catalytic effect.