Abstract: A process and apparatus for bringing CO.sub.2 from a storage tank wherein it is stored at a medium pressure and below 0.degree. C. (e.g. -20.degree. C. and 20 bars pressure) to a high pressure such as 80-130 bars, without utilizing any pump operating below 0.degree. C. The build-up of ice on such a pump is thus avoided. To do this, liquid from the tank is caused to completely fill by gravity an intermediate vessel. Then the vessel is heated to about ambient temperature; and while maintaining such temperature (e.g. by means of resistor 16), the liquid in the vessel is subcooled by compression in FIG. 1 or by cooling water in FIG. 2, and conveyed to the inlet of the high pressure pump.