Analyze the reasons for poor oxygen purity?

Analyze the reasons for poor oxygen purity?

The purity of industrial oxygen is 99.5% oxygen. The quality of steel produced with low oxygen purity will be very poor. It will affect the welding quality when used for gas cutting and gas welding. It is also prohibited to use it for medical treatment. When the distillation conditions are abnormal, the purity of O2 and N2 will be significantly reduced.

The reasons are as follows:

(1) The performance of the tower plate is reduced: the distillation tower is tilted, the tower plate is deformed, the sieve hole is blocked, etc.

(2) The distillation conditions are abnormal. “Liquid overflow” or “liquid leakage” occurs in the cold box, and the oxygen purity is reduced.

(3) The main condenser evaporator does not work properly. Impurities in the main condensate will affect heat exchange, and factors such as main condensate leakage will reduce the purity of oxygen.

(4) Excessive oxygen extraction. From the perspective of distillation conditions, excessive oxygen extraction will reduce the amount of steam rising from the upper tower, increase the reflux rate, and increase the amount of downstream liquid, which will inevitably reduce the purity of oxygen.

(5) The purity of liquid air is too low. The lower tower is the bottom of the upper tower. If the purity of the liquid air in the lower tower is too low, this will inevitably affect the purity of the oxygen. Therefore, the optimal distillation condition for the lower tower should be when the liquid nitrogen purity meets the requirements.

(6) The liquid oxygen level in the condenser evaporator is too high. The increase in the initial cooling liquid oxygen level means that the downstream liquid volume is greater than the evaporation volume, and the reflux rate of the residual part increases, resulting in a decrease in oxygen purity.

(7) The greater the amount of air entering the upper tower for expansion, the lower the purity of the waste nitrogen. To ensure the oxygen supply, the oxygen purity must be reduced.