Crystal Growth of Clathrate Hydrate with Ozone: Implication for Ozone Preservation

Preservation using hydrates as a storage medium is the only technology that enables long-term and high-concentration O3 preservation. This study reports the visual observations of the crystal growth of O3-containing hydrate for the process design of the hydrate production plant. We conducted experiments with the feed gas involving O3, O2, and CO2 in the molar ratio of O3:O2:CO2 = 3.4:42.0:52.6. During observations, O3 in the mixed gas remained at 1.31-2.43 mol %, which is comparable to those of the previous experiments. The observed results of hydrate crystal growth dynamics were classified into two types, which are lateral growth along the gas/water interface and growth into the bulk of the liquid water phase. Crystal morphology varied from polygonal to columnar, dendritic, or haze like with increasing subcooling temperature relative to equilibrium. The diversity of the crystal morphology of O3-containing hydrate was comparable to those of O2 + CO2 hydrate and CO2 hydrate. The implications of the obtained results for the operating conditions of an O3-containing hydrate production plant are discussed.