After the argon fraction is extracted from the upper tower, it enters the crude argon tower for oxygen and argon separation using distillation method. Generally, the components of coarse argon extracted from the top of the coarse argon tower are: argon greater than 98%, nitrogen less than 0.5%, and oxygen less than 1.5%. Introduce crude argon with a purity greater than 98% into the molecular sieve adsorber. Two adsorbers are set for each group, with one adsorber containing 5A molecular sieve to adsorb nitrogen from coarse argon gas; Another adsorber is equipped with 4A molecular sieve to adsorb oxygen from crude argon gas.
In order to desorb the adsorbent, two sets of adsorbers need to be set up and switched for use. The adsorber operates at a temperature of 90K. The coarse argon gas first enters the 5A molecular sieve adsorber for nitrogen removal, and then enters the 4A molecular sieve adsorber for oxygen removal. The process is shown in Figure 18. The gas from a group of molecular sieve adsorbers can have an argon purity of 99.99%, which is pure argon.
The advantages of adsorption method for argon are simple process flow, convenient operation, and low cost. However, the purity of argon can only reach 99.99%. Due to the limitation of the selective adsorption capacity of molecular sieves, a purity of 99.999% cannot be obtained. A's high-purity argon gas. Another disadvantage is that the working temperature of the adsorber is 90K, and the regeneration temperature is 423K, making the design of the adsorption structure more difficult.
When the adsorber is working, the bed layer must be cooled, often using a jacket or liquid oxygen cooling inside the tube. It is very difficult to achieve a uniform cooling temperature for larger diameter adsorbers required for large-scale argon production equipment. Due to the above two drawbacks, the application of adsorption method for pure argon is limited. At present, the adsorption method for argon in China has a capacity of no more than 10m3/h and is only used on argon production equipment matched with 150m3/h air separation equipment. It has not yet been applied to large-scale argon production equipment.