Modern air separation units are equipped with molecular sieve adsorber vessels for front-end purification. Because of changes in operating conditions, in some cases CO2 may slip through, which could cause operational problems and safety risks.
What occured in the plant?
In the described case carbon dioxide gas traces slipped through the molecular sieve adsorbers. Carbon dioxide froze in the main heat exchanger and blocked the air passages. As a result, the performance of the main heat exchangers decreased. Losses of produced cold increased. This in turn lowered plant production.
How did the Linde specialists solve the problem?
A Linde start-up engineer analyzed the situation at the plant and optimized adsorber parameters. The start-up engineer found that the heat exchangers were blocked with frozen CO2 and dust from the upstream molecular sieve adsorber.
One heat exchanger after another was cleaned by blasting air through the passages. After blasting, the plant performance was recovered and the specific energy costs were reduced to even lower levels than originally specified.
