Study on CO2 releasing nozzle for CO2 ocean storage

Ocean storage of CO(2) is one of greenhouse gas control technologies, where C02 captured from flue gas of fossil fuels is injected into deep sea below 3500m depth to be sequestered from the atmosphere. A CO(2) sending method, COSMOS, was proposed as a method of ocean storage, which enables CO(2) drops released in mid-depth water to descend to deep sea floor below the depth of 3500m. Then, the authors have worked for development and evaluation of COSMOS. In the first phase of the COSMOS project, the concept of COSMOS was demonstrated by in situ experiments of small-scale CO(2) releasing at mid-depth water in Monterey Bay, U.S.A. Three models of CO(2) releasing nozzle unit were developed for the experiments. The first model of nozzle unit released liquid CO(2) as one mass; however, it was immediately broken into small droplets and soon turned to ascend. The second and third models were designed to have thermal insulator enough to keep low temperature so that both models successfully released liquid CO(2) with dry ice, which continued descending for a few minutes. Based on these results, COSMOS was improved, where injection of a mixture of liquid CO(2) and dry ice, CO(2) slurry, is expected to enable small CO(2) drops to descend to deep sea floor below 3500m depth. Then, in the second phase of the COSMOS project, the authors started an investigation on the effect of the aspects of releasing nozzle on the behavior of released slurry drops, and obtained a few results from lab experiment of CO(2) slurry releasing from two types of nozzle head.