Development of CO2 Slurry Release Nozzle for CO2 Ocean Storage

Ocean storage of CO₂ is one of greenhouse gas control technologies. The authors developed a release nozzle based on the concept of a CO₂ sending method for the ocean storage, COSMOS, where liquid CO₂ is released as a mixture with dry ice, CO₂ slurry, at the depth as shallow as 500 m to sink to deep water. The authors have carried out the development of CO₂ slurry release nozzle. At first preliminary experiments with a single-tube nozzle were conducted. The results of the preliminary experiments implied that the plugging of nozzle outlet should be prevented to allow the slurry to be released continuously. Then, the authors proposed the concept of coaxial double-tube release nozzle and demonstrated the effectiveness of the concept by injection experiments with a double-tube slurry injection unit. Slurry injection experiments were carried out with two types of inner tube with different inner diameter to investigate the effect of the nozzle dimensions and the slurry flow on the slurry drops released from the nozzle. The length of the mixing zone in the nozzle (Δ), which is the length from the outlet of the inner tube to the outlet of the outer tube, and the slurry injection rate were varied in the experiments. The surface of slurry drops from the nozzle with smaller Δ was more stable than that from the nozzle with larger Δ. Moreover, as the injection rate was increased, the instability of the slurry drop surface was increased. These results suggest that the nozzle dimensions and the slurry flow would affect the size and shape of slurry drops from the nozzle.