Product acid at up to 38% hydrochloric
acid leaves at the bottom of the falling film
absorber at a suitable temperature for storage
and is ready for pumping.
The remaining unabsorbed hydrogen chloride gas
and any inert gases present leave at the bottom
of the falling film unit and enter at the bottom
of the tails tower.
Process feed water entering at the top of the
tails tower absorbs the hydrogen chloride to form
dilute hydrochloric acid.
The dilute acid flows by gravity to the top of
the falling film absorber to serve as the liquid
feed to the tubes.