A METHOD OF DRAINING A TANK AND A PLANT FOR USE IN SUCH DRAINING

摘要

PCT No. PCT/NO94/00215 Sec. 371 Date Dec. 31, 1996 Sec. 102(e) Date Dec. 31, 1996 PCT Filed Dec. 30, 1994 PCT Pub. No. WO96/21121 PCT Pub. Date Jul. 11, 1996A method of draining a tank that has been containing liquid gas, and a plant for use in such draining. After draining of the major part of the tank contents, but while residual contents of gas are present in vapourized state in the tank, the residual contents are conveyed for exchanging heat directly or indirectly with cold nitrogen. Nitrogen is vapourized and heated and conveyed to the tank, while the residual gas is cooled and condensed and conveyed to a collector tank. The plant comprises a heat exchange system connected to the supply of nitrogen, and residual gas is forced from the tank to be drained and through the heat exchange system in order to cause vapourization and heating of nitrogen to be conveyed to the tank, in such a manner that the residual gas from the tank condenses, whereby a collector container is connected for receiving condensed residual gas. In order to prevent that the residual gas freezes during the exchange of heat a cooling agent can be used which causes vapourization and heating of the nitrogen and which also is used for condensing the residual gas, without cooling the latter to below its freezing point.