The term "scrubber" usually indicates those components used to purify gas and air. The first was designed in the 19th century for a pioneering type if submarine, called Ictineo I.
Scrubbers have evolved a lot since then: initially, their process was liquid-based, then a new dry one was developed.
Their presence in the chemical and petrochemical sectors is quite strong, considering that a good part of the refining process consists of separating complex compounds into simpler ones.
A specific case are melamine plants. Melamine is not very known by laypeople, but almost ubiquitous (we introduced it in a previous article).
Melamine is synthetized directly from urea, and ammonia and CO2 are two by-products. In order to make its production more efficient, these two compounds are reintroduced in the urea production cycle.