Formation of CO_2 Hydrte in the Presence of Montmorillonite

摘要

Since direct disposal of CO_2 in the ocean is a highly potential sequestration option, the process of oceanic disposal of CO_2 has attracted much attention as an effective technology that can declearte global-warming. When CO_2 is discharged in deep sea region subject to high pressure and low temperature, CO_2 hydrate can be formed easily. For the design purpose of the CO_2 disposal process, the formation rate of the CO_2 hydrte is required. Furthermore, it is well known that natural gas is often found at off-shore, buried under oceanic sediments. It should be necessary, therefore, to understand the interaction between the gas hydrate and the solid materials in the deep sea bed. The purpose of this paper is to investigate experimentaly the effect of clay materials in deep sea bed on rate of formation of CO_2 hydrate. Since montmorillonites are the main components of the clay materials, the authors used two kinds of montmorillonites, Na-and Ca-montmorillonite. The Na-montmorillonite is hydrophillic, while the Ca-montmorillonite is hydrophobic. The rate of formation of the hydrate was determined from measurements of rate of consumption of CO_2. During the process of formation of hydrate, both temperature and pressure in the reactor deviate from the initially setted values. The authors, therefore, studied the relation between the rate of formation of hydrate at an initial stage and the content of the montmorillonite. It was found that the initial rate of formation of hydrate drops as the content of Na-montmorillonite increases. On the other hand, the effect of the Ca-montmorillonite was not so significant.