Hastelloy and 316L to 304 stainless steel.
Hot gases are often cooled to near the saturation level.
If not cooled, the hot gas stream can evaporate a large portion of the scrubbing liquor,
adversely affecting collection efficiency and damaging scrubber internal parts.
If the gases entering the scrubber are too hot, some liquid droplets
may evaporate before they have a chance to contact pollutants in the exhaust stream,
and others may evaporate after contact,