What are the common abnormalities in pressure swing adsorption (VCM)?

The fire might be caused by too high an oxygen level; check whether the feed gas contains oxygen. Pressure swing adsorption venting can also cause fires; this may be due to insufficient purity of hydrogen chloride, an excessive amount of hydrogen, and the generation of static electricity during venting. The unqualified purified gas is due to an inappropriate setting of the adsorption time; changes in the flow rate or purity of the feed gas require adjustments to the adsorption time. Otherwise, if the adsorption time is too long, vinyl chloride and acetylene will pass through the adsorbent and enter the purified gas, causing it to exceed the specified standards. Too short an adsorption time will also result in a low concentration of the product gas. The pressure swing adsorption unit is equipped with packing that adsorbs vinyl chloride and acetylene, while the hydrogen recovery unit is used to adsorb impurities other than hydrogen.

You must be Ito, right? Regarding the issues over there, didn’t Sichuan Kaiyuan investigate the reasons for them in the past? The Kaiyuan manufacturer is currently conducting adjustments at our company; he visited your company before and talked about it.

Adjust the adsorption time based on the analysis data of the feed gas

The poster is referring to the possible abnormal issues with pressure swing adsorption used in VCM production plants manufactured by the calcium carbide method, right! ?

1. Programmable valve sticking 2. High oxygen content in the recovered gas 3. High concentration of useful gases in the exhaust gas

1. There are three main reasons for the unqualified purified gas: first, the packing becomes saturated due to adsorption; second, the flow rate of the raw gas is too high, causing the system to operate beyond its capacity； Second, the regeneration of the filler is incomplete, resulting in a decrease in its adsorption capacity ； Third, when the lifespan of the packing is reached or its adsorption capacity declines, if liquid monomer enters the adsorption tower, the packing becomes saturated with adsorbates, and it is necessary to regenerate the packing or replace it.

2. The ignition of the hydrogen production filler is caused by excessive levels of the purified gas upstream, which leads to exothermic adsorption by the hydrogen production filler； Another possibility is a defect in the equipment; inhaling air during regeneration can also pose a risk of explosion.

3. The adsorption fillers are primarily used to adsorb acetylene and vinyl chloride, with aluminum oxide, silica gel, and activated carbon being the most common ones； The hydrogen production filler is used to adsorb impurity gases other than hydrogen. Generally, in cases where the levels of acetylene and vinyl chloride in the purified gas are not within acceptable limits, additional filler designed to adsorb these substances is used. Without such filler, it would be extremely dangerous to continue operating the hydrogen production process when the levels of impurities in the gas exceed the allowed limits.

4. Fluctuations in system pressure will certainly cause fluctuations in the operation of the adsorption tower; this results in an excessive instantaneous processing capacity of the tower, and the adsorption tower that has become saturated no longer has the ability to absorb substances, leading to the leakage of acetylene and vinyl chloride and resulting in untreated gas that does not meet quality standards.

5. If you have understood the previous points, it should be easy to grasp: pressure swing adsorption is used for treating vinyl chloride and acetylene. In other words, the levels of vinyl chloride and acetylene determine the operating load on the system. At the same gas flow rate, an increase in the concentration of vinyl chloride and acetylene will increase the processing load on the system.