Switching heat exchanger flow oxygen generator, in order to achieve the self-cleaning of moisture and carbon dioxide, requires a large amount of dirt nitrogen to ensure the condition of not freezing, therefore, the amount of pure gas nitrogen products is less, it can only reach 1.3 times of the gas and oxygen production at most. Therefore, the amount of pure liquid nitrogen provided by the lower tower to the upper tower is relatively small, so a stream of sewage nitrogen can be extracted to the upper tower. In this way, the reflux ratio of the distillation section of the upper tower can be increased, which makes it have greater rectification potential, thus allowing more inflated air to enter the upper tower to prevent the inflated air from passing by and affecting the oxygen extraction rate.
As for the oxygen generator with the purification and booster expansion process of the molecular sieve, the quantity of pure gas and nitrogen products has been greatly improved because it is not restricted by self-cleaning. In addition to ensuring the amount of dirty nitrogen used for regeneration of the molecular sieve purifier, the rest can be sent out as pure gas 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 directly increase the reflux ratio of the distillation section by extracting sewage nitrogen. At the same time, because there is no sewage and nitrogen pumping, the lower tower reduces the pumping outlets, pipelines and valves, and the process is simplified.
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 extract sewage nitrogen from the lower tower.
