A low pressure nitrogen expander is added to the process design. The pressure nitrogen from the pressure tower and high pressure expander is expanded into low pressure nitrogen, which is combined with the nitrogen coming from the low pressure tower and fed into the charge gas compressor. This is specially set up for rapid oxygen load changes. The oxygen product flow rate during normal operation corresponds to the amount of oxygen contained in the amount of air entering the air separation unit. That is, the amount of liquid oxygen pumped from the low pressure tower into the storage tank is the same as the amount of liquid oxygen extracted from the storage tank and pressurized by the liquid oxygen pump to the main heat exchanger of liquid air separation plant.
With this nitrogen cycle rapid load change technology, compared with the conventional air booster internal compression process, it is not only possible to meet a large range of rapid oxygen production changes without bypass or additional compressors, but also to minimize the impact of compressor flow and pressure changes on the distillation column caused by a wide range of variable loads. The working condition in the distillation tower remains basically unchanged when the oxygen output varies from ±20,000Nm3/h at the operating point.
