When fractionating on the upper tower, the part below the liquid air inlet is called the stripping section, and the part above the liquid air inlet is called the distillation section. The stripping section realizes the separation of oxygen and argon, and the distillation section realizes the separation of oxygen and nitrogen. Because the boiling points of oxygen and argon are relatively close, the separation is difficult. In order to ensure the purity of oxygen, the oxygen in the distillation section is generally not separated cleanly, and argon escapes with oxygen and nitrogen. If high-purity nitrogen is to be obtained, argon will condense with oxygen in the distillation section, affecting the purity of oxygen. In order to ensure the purity of oxygen and obtain high-purity nitrogen, it is necessary to extract part of the gas with high argon concentration in the distillation section.
Kaifeng DEAR air separation plant is a kdon-300/3000 air separation plant for Shandong Kenli petrochemical. The unit is equipped with an external oxygen tower, which uses oxygen enriched liquid air as raw material to produce part of oxygen. The oxygen enriched liquid air is extracted from the condensing evaporator and throttled into the upper part of the oxygen tower as reflux liquid. The pressure nitrogen at the top of the distilling tower is used as the heat source of the oxygen tower evaporator to exchange phase change heat with liquid oxygen. The liquid oxygen evaporation is used as the rising steam of the oxygen tower, and the nitrogen condenses and returns to the lower tower. The product oxygen is extracted from the lower part of the oxygen tower and sent out after being reheated by the main heat exchanger. Liquid nitrogen products are pumped from the liquid nitrogen return pipeline of the condensation evaporator to the lower tower and transported to the storage tank. The system is equipped with liquid nitrogen reinjection pipeline, which greatly shortens the start-up time, and users are full of praise for the performance of this air separation unit.
