Liquefied gas supply system and air separation unit comprising same

An air separation process comprising the steps of:

• providing a first rectification column operating at a first pressure, a second rectification column operating at a second pressure, less than the first pressure, the first rectification column having a top condenser enclosed within a condenser section operating at the second pressure, wherein the second rectification comprises a supply source that is disposed in a lower region of the second rectification column, the first rectification column and the second rectification column being placed side by side;
• sending feed air to a heat exchanger to be cooled and then from the heat exchanger to the first rectification column;
• sending a gas from the condenser section to a bottom section of the second rectification column;
• removing a top gas is removed from a top section of the second rectification column, and then sending the top gas from the top section to the heat exchanger to be warmed,
• wherein in normal operation, the process further comprises the steps of:
• using a first pump and a second pump that are connected in parallel to pressurise liquid from the bottom of the second rectification column, the first pump producing liquid at a first liquid pressure and the second pump producing liquid at a second liquid pressure, higher than the first liquid pressure, and
• using the first pump to send liquid at the first liquid pressure to the condenser section and
• using the second pump to send liquid at the second liquid pressure to the heat exchanger, wherein liquid at the second liquid pressure is at least sometimes sent from the second pump to the condenser section.

An air separation unit comprising a liquefied gas supply system, the liquefied gas supply system comprising:

• a first liquid feed pump which is used to feed a first liquefied gas from a supply source to a low-pressure supply destination for low-pressure purposes;
• a second liquid feed pump which is used to feed a second liquefied gas from the supply source to a high-pressure supply destination for high-pressure purposes;
• and
• a control unit for controlling the first liquid feed pump and the second liquid feed pump, wherein
• the control unit:
• implements first circulation liquid in-feed processing for feeding in the first liquefied gas from the supply source to the low-pressure supply destination by means of the first liquid feed pump which is in a low-pressure operating mode;
• and first product liquid in-feed processing for feeding in the second liquefied gas from the supply source to the high-pressure supply destination by means of the second liquid feed pump which is in a high-pressure operating mode;
• and/or
• implements second circulation liquid in-feed processing for feeding in the first liquefied gas from the supply source to the low-pressure supply destination by means of the first liquid feed pump which is in the low-pressure operating mode, and also for feeding in a portion of the second liquefied gas from the supply source to the low-pressure supply destination by means of the second liquid feed pump which is in the high-pressure operating mode;
• and second product liquid in-feed processing for feeding in the remainder of the second liquefied gas from the supply source to the high-pressure supply destination by means of the second liquid feed pump which is in the high-pressure operating mode.