The liquid oxygen from the main condensing evaporator is compressed by the internal compressed oxygen pump, evaporated and reheated, and then enters the main heat exchanger. The liquid oxygen then flows out of the cold box as an oxygen product. The low pressure nitrogen is pumped out of the top of the low pressure tower and its cooling capacity is transferred to the return liquid in the sub-cooler. The cooling capacity is sent out of the cold box via the main heat exchanger, part of which is compressed by the first stage charge nitrogen compressor and sent to the nitrogen recirculation compressor. A portion is sent out as a low pressure nitrogen product. The remainder is further compressed by the charge nitrogen compressor, cooled by the aftercooler and sent out as a low pressure nitrogen product.
The medium pressure nitrogen is fed out of the first section of the nitrogen recirculation compressor (after the intercooler). The high pressure nitrogen is delivered from the second stage of the nitrogen cycle compressor (before the intercooler). The ultra-high pressure nitrogen is delivered from the last section of the nitrogen cycle compressor (before the compressor aftercooler).
The liquid nitrogen product comes from the main condensing evaporator, where one stream of liquid nitrogen product is cooled in the cooler and flows out of the cold box to provide subcooled liquid nitrogen for the liquid nitrogen cleaning unit. The other stream of liquid nitrogen is fed directly into the storage tank. The instrument air and plant air products are extracted from the process air after the molecular sieve and further compressed to the required pressure by a single stage air compressor with an aftercooler.
