As for the oxygen generator in the flow of switching heat exchanger, in order to achieve the self-elimination of moisture and carbon dioxide, the amount of dirt and nitrogen is relatively large, so the condition of not freezing can be guaranteed. Therefore, the amount of pure gas and nitrogen products is relatively small, it can only reach 1.3 times of the output of gas and oxygen at most, so the amount of pure liquid nitrogen provided by the lower tower is less, so a stream of sewage nitrogen can be extracted to the upper tower, which increases the reflux ratio of the distillation section of the upper tower, it has greater rectification potential, thus allowing more inflated air to enter the upper tower to prevent inflated air from passing by and affecting oxygen extraction rate.
As for the oxygen generator in the process of purification, pressurization and expansion of molecular sieve, the quantity of pure gas and nitrogen products has been greatly increased due to the lack of self-cleaning restriction. In addition to the quantity of dirt and nitrogen used for regeneration of the molecular sieve purifier, both can be sent out as pure gas and nitrogen products, and the ratio of pure nitrogen production to oxygen production can reach 3 ~ 3.5. In this way, the lower tower needs a larger reflux ratio to ensure the amount and purity of pure liquid nitrogen, and then it is sent to the upper tower as the reflux liquid.
In addition, because this process adopts pressurized expansion, the unit refrigerating capacity of the expansion working medium is relatively high, under the premise of compensating the same cold loss, the required expansion capacity is relatively small, generally, it will not exceed the air volume allowed by the upper tower, therefore, it is not necessary to extract sewage nitrogen to directly increase the reflux ratio of the distillation section. At the same time, because there is no sewage and nitrogen pumping, the lower tower reduces the pumping outlets, pipelines and valves, and simplifies the process.
In a word, oxygen generator with high production of pure gas and nitrogen generally does not draw sewage and nitrogen. In the case of pressurized expansion and small expansion, it is even more unnecessary to draw sewage nitrogen from the lower tower.
