LIQUEFACTION/SEPARATION METHOD FOR AIR AND DEVICE THEREOF UTILIZING LNG COLD HEAT

PURPOSE:To make it possible to operate a high rating fractionator by a method wherein an excessive liquid air is prepared as an intermediate product under a condition in which much more LNG cold heat can be utilized, and the liquid air is stored in a liquid air storage tank, and the stored liquid air is fed to the fractionator when the feeding volume of the LNG cold heat decreases. CONSTITUTION:When the utilizable volume of LNG is large, a high load operation of an air liquefaction device is performed, and one part of the produced liquid air is stored in a liquid air storage tank 17, and at the same time, the other part is separated by a fractionator 9 into liquid oxygen and liquid nitrogen or crude argon, etc., and stored. In the meantime, in a time zone in which the LNG utilizable volume decreases, an operation for which the taking-in of raw material air is limited in response to the decreased portion is performed. Therefore, for the replenishment of liquid air, the liquid air which is previously produced and stored in the storage tank 17 is introduced to the fractionator by a required quantity. By this method, the operation of the frationator 9 can be kept always uniform without being affected by the LNG utilizable volume.