Reducing power consumption in a cryogenic air separation plant for filling oxygen cylinders in-situ by utilizing thermal energy of pumped liquid oxygen

Cryogenic air separation plants produce oxygen at 99.5% purity at 150, 230 and 300 bar to fill cylinders. From the production location, liquid oxygen is often transported to a cylinder-filling plant located at a far-off location where it is pumped to high pressure and gasified in ambient vaporizers. Among the methods of cylinder filling, external vaporization is the safest, operationally most flexible, and allows the main heat exchanger to be designed at low pressure. Despite these advantages, external vaporization is not preferred for filling cylinders "in situ" because of high power consumption attributed to the loss of the entire cold exergy of pumped liquid to the environment. An appropriate modification of the plant helps to utilize the thermal energy of pumped liquid oxygen that is externally vaporized to fill cylinders at the plant site. A reduction of specific power consumption by 23% to 29% is possible while the main heat exchanger still operates at low pressure. Cylinders can also be filled at any of these pressures from the same plant with a penalty of 2% to 3% in SPC. The paper shows ways to adjust the operation of the air compressor to obtain oxygen at varying pressures with utilization of the thermal energy of liquid oxygen.