The most commonly used methods for removing moisture, carbon dioxide, and acetylene from the air are adsorption and freezing.
The adsorption method uses silica gel or molecular sieves as adsorbents to separate impurities such as water, carbon dioxide, and acetylene from the air, as well as acetylene from liquid air and liquid oxygen, and concentrate them on the surface of the adsorbent (without chemical reaction). When heated and regenerated, they are then removed to achieve the purpose of purification. For example, setting up dryers, carbon dioxide adsorbers, liquid air adsorbers, and liquid oxygen adsorbers.
The freezing method is to freeze the moisture and carbon dioxide contained in the air when it passes through a cold storage or switching heat exchanger (acetylene cannot freeze), and then be carried out of the device by dry backflow gas, which is self clearing.
In high-pressure, medium pressure, high and low-pressure oxygen production systems, the alkaline washing method was used to remove carbon dioxide, that is, using an aqueous solution of sodium hydroxide (Na0H) to absorb carbon dioxide from the air. Due to inconvenience in operation, it has been phased out.
The use of molecular sieve purification process can simultaneously adsorb and remove moisture, carbon dioxide, and acetylene from the air, simplifying the process. It has been widely used in oxygen concentrators.
