Process cooling can be done either by contact, in the case of solids, or non-contact, in the case of liquids.

In the case of contact systems, the cooling liquid is usually sprayed onto a hot product, such as a steel slab in continuous casting, in an effort to cool the product to a desired temperature. In so doing, the water usually picks up loose particulate of the product to be cooled and carries it through the system. In addition, such systems often include some sort of open containment vessel, which is used to collect the cooling water as it leaves the product, which is an additional source of particulate.

The water is typically re-circulated through either a cooling tower or a heat exchanger to reject the excess heat. It is desirable to remove the particulates picked up in the process prior to passing the water through the tower or heat exchanger.