Oxygen generators are switchable heat exchanger process oxygen generators and molecular sieve pressurised expansion process oxygen generators.
The pure liquid nitrogen supplied to the upper tower is less and a stream of dirty liquid nitrogen can be pumped to the upper tower.
The oxygen generator of the pressurised expansion process, because there is no restriction of self-scavenging, so the amount of pure gas nitrogen product is increased substantially, except to ensure that the molecular sieve purifier is regenerated with dirty gas nitrogen, all other nitrogen products can be sent out as pure gas nitrogen products, with a ratio of pure nitrogen production to oxygen production of 3 - 3.5 times. In this way, the lower tower requires a large reflux ratio to ensure the amount and purity of pure nitrogen, which is then fed into the upper tower as a reflux.
In addition, due to the use of pressurised expansion, the unit cooling capacity of the expansion mass is higher, and the expansion volume required to supplement the same cold loss is smaller and generally does not exceed the amount of air allowed into the upper tower, therefore, there is no need to pump dirty liquid nitrogen to directly increase the reflux ratio of the distillation section.
Dear Air Separation has experience in manufacturing, pure gas nitrogen products with a large output of oxygen generators in the lower tower generally do not pump dirty liquid nitrogen. As a result in small air separation unit we do not pump dirty liquid nitrogen, the lower tower has fewer pumping ports, piping and valves, and the process is simplified.
