Concerning with the disposal of CO₂ in ocean, technical aspects on sending CO₂ into deep ocean with a long vertical pipe from a floating platform are treated in this paper. At first, the heat balance of liquid CO₂, pipe, ice on the wall and the surrounding seawater is formulated under the equilibrium condition. In order to estimate the vertical temperature change of CO₂ correctly, it is found that the heat insulating effects of the ice covered on the pipe wall should be taken into accout. The validity of the estimation method is confirmed with a laboratory test. A stainless pipe is fixed in a seawater-circulating tank and cold N₂ gas is let flow in the pipe constantly. The temperature change of the N₂ gas and the thickness of ice generated on the pipe wall are measured to be compared with calculated results. Secondly, case studies are performed on liquid CO₂ recovered from a 1.0 GW-class coal burning power station. Here, the equipments and piping diagram are initially designed under the necessary condition that the temperature and the pressure of CO₂ at the lower outlet are almost the same with those of surrounding seawater.