The safe operation of air separation plants requires special attention not only during design, but also during operation, which needs to be well monitored.
With a variable temperature adsorption system, all process air is passed through alumina to remove moisture and then CO2 is adsorbed at the molecular sieve layer, along with acetylene, isobutane and heavier hydrocarbons. Most hydrocarbons such as isobutane and heavier hydrocarbons are almost completely removed, while propane, ethane and ethylene are only partially removed.
To ensure proper operation of the air purification unit and thus reduce the possibility of hydrocarbons entering the main condensing evaporator, a CO2 analyser is installed to measure the CO2 level at the outlet of the air purification unit on an uninterrupted basis. Any occasional or non-accidental exceedance of the CO2 level should be identified and eliminated. The accuracy of the CO2 analyser should be checked from time to time to ensure that the CO2 level in the air prior to entering the cold box is detected in a timely manner.
The design of the double-bed purifier uses a fixed adsorption bed and has a self-cleaning system to minimise the risk of molecular sieve abrasion and acid corrosion. The possibility of dust ingress is also minimised, as once dust enters the cold box, it will eventually enter the main condensing evaporator and cause equipment blockage.
