| 摘要 |
A method and apparatus for delivering a cryogen in which a cryogen is stored and delivered in a cryogenic storage facility having three tanks. Each of the tanks is filled with the cryogen in a subcooled liquid state to wash contaminants down toward a bottom region thereof. Thereafter, a minor stream composed of superheated vapor is introduced into the bottom region of each tank to pressurize each tank. A major stream of the superheated vapor is then introduced into each tank to form scrubbed cryogenic vapor in the head space region thereof which is used in forming the product stream. Each tank is subsequently used to dispense the cryogen to a vaporizer to form the superheated vapor which is in turn divided into the major and subsidiary streams. The forgoing operations are preferably conducted the three tanks as an out of phase cycle such that one tank dispenses the liquid cryogen to the remaining tanks as the major and subsidiary streams and after having dispensed the cryogen, each tank is refilled which again substantially clears the top head space region thereof of contaminants. |
