The ISAC is a small, packed column placed underneath the WSA condensers in WSA and SNOX™ plants. The purpose is to boost the acid concentration from what can be produced in the WSA condenser, e.g. 98%, to e.g. 98.5%. For special applications of sulfuric acid, a very high acid concentration is important.

The acid produced in the WSA condenser flows downwards through the packing in countercurrent with hot, dry air, generated in a package unit with air blower, dryer , nd heater. The hot, dry air drives some of the water content out of the sulfuric acid. The water vapor leaves the plant with the clean gas from the WSA condenser.

ISAC units are supplied only in connection with WSA or SNOX™ plant technology.