Visualization study of dissolution behavior of liquid CO2 with hydrate using pH indicator

Abstract

In recent years, CCS (CO2 Capture and Storage), which capture CO2 from CO2 emission source and storage it in ocean, for mitigation of global warming has been expected. Especially, the method using depression region in seabed that can be stored huge amount of CO2 and reduce the influence on surrounding environment is required to practical use. In this method, hydrate is formed at the interface of liquid CO2 and seawater, but the diffusion behavior of CO2 with the hydrate film is not clear. Therefore, this paper aimed to measure CO2 concentration distribution and estimate effective diffusion coefficient. We visualized pH distribution in timeseries using bromophenol blue as a pH indicator in a pressure resistance visualization apparatus under hydrate formable conditions. As a result, pH concentration in water due to CO2-dissolving was verified by variation of colors of water including pH indicator, and saturated solution of CO2 represents pH 2.9. The diffusion process of CO2 was evaluated by calculated line of pH 3.0 from diffusion equation with the hydrate. We compared the experimental results and calculated results from diffusion equation, and the calculated results with larger diffusion coefficient than the conventional knowledge corresponds with experimental results. We compared experiment results with calculation results estimated by the diffusion equation of surface renewal model and small eddy model, and we confirmed that acceleration of diffusion can be explained by these models.

Keywords

• co2 hydrate
• dissolution
• diffusion
• visualization
• ph
• ccs