The sequestration (liquidation) of CO2 is defined as catching, deposition and storing of CO2. Industrial CO2 can be deposited in the exhausted oil and gas deposits, in unexploitable coal seams or in the aquifers. Different methodology is represented by the binding of CO2 in minerals (rocks) by the methodology of mineral sequestration (carbonatization). The first group of methods is accompanied with the risks of CO2 deliberation during transport and deposition of CO2. Moreover, the storage sites must be located away of the seismo-active zones and expensive monitoring is necessary during hundreds of years.
Some industrial wastes (e.g. fly ashes, slags) contain modified minerals or substances able to react with CO2 with resulting its solid bonds in the lattice of newly formed carbon minerals - carbonates.
The main advantage of mineral sequestration of CO2 by the carbonatization is the safe and fast (lasting only several hours) liquidation of gaseous CO2, resulting in the origin of synthetic carbonates. They have no negative impact on the living environment, and, moreover, they can be used in industrial production.
Our pilot laboratory tests of CO2 sequestration using laboratory high-pressure reactor were done on the samples of the fly ash and slags after the brown coal combustion and the crushed ultramafics (serpentinite) after the exploitation of chrysotile asbestos.
The X-ray analyses revealed in the primary samples of the fly ash and slags 92-100 % of the amorphous phase without the presence of carbonates. The serpentinite samples contained nearly 90 % of serpentinite minerals, only with subsidiary content of calcite. During the reaction of mechanically (fly ash, slags), resp. thermally (crushed ultramafics) activated compounds of the waste with gaseous CO2 at precisely determined P-T conditions (0.1-0.9 MPa, 20-200 °C), the new mineral phases – acid carbonates and carbonates have precipitated in the relatively short time (2-22 hours) after carbonatization, filtration and following drying with crystallization.
The X-ray analyses confirmed the high quality of newly formed mineral phases – precipitated calcium carbonate (ca 100 % CaCO3) with the calcite and aragonite minerals in the ratio 9:1, originating from the sample of fly ash, resp. 3:2 in the case of the sample of slags. The CO2 sequestration using serpentinite has produced the high purity nesquehonite (97 %), resp. hydromagnesite (96 %). The new products have fine-grained to powdery composition of white to white-yellowish colours, which supports their application as inorganic fillings in industrial production of plastics, rubber, cements, paints, paper, etc.
According to the journal Industrial Minerals, in February 2010 the price of the ground calcium carbonate (GCC) reached 80-103 GBP/t, the price of precipitated calcium carbonate (PCC) 320-480 GBP/t, resp. elaborated precipitated calcium carbonate up to 550 GBP/t.
The application of the CO2 sequestration by carbonatization in the industrial scale would result in the lowering of the amount of industrial CO2 emitted into the air and deceleration of the global warming. It will simultaneously lead to minimization of the amount of stored waste material and to production of the economically interesting carbonates usable in manifold industrial branches. By this way the methodology directly as well as indirectly contributes to the protection of living environment. Presented research corresponds with the documents of the European Commission concerning the catching and liquidation of CO2 with the need to lower CO2 emissions by 20 % until 2020.