Spray towers can be used as chemical scrubbers, in order to
remove some gaseous compounds. Even if packed towers are
the most commonly employed for deodorisation, they are limited
to the “closed sites”, where the polluted gas can be collected,
whereas spraying can be implemented on “open sites”. Among
the long list of gaseous compounds which have to be removed,
there are toxic and odorous ones, like H2S. H2S is produced
by the anaerobic decomposition of sulphur-containing organic
and inorganic matter. Many industrial activities contribute to
its emission (paper industry, wastewater treatment plants, etc.).
The human nose can detect the H2S “rotten egg” odour at very
low concentrations (0.4 ppb) and the toxicity threshold of this
compound is about 10 ppmv [7]. Various oxidants (chlorine
(Cl2), ozone (O3), sodium hypochlorite (NaOCl) and hydrogen
peroxide (H2O2), etc.) are able to remove H2S after it has
been transferred to the liquid phase. The most frequently used
is a combination of sodium hydroxide (NaOH) and sodium
hypochlorite because of the low cost and efficiency [8]. The
addition of chlorine in the scrubbing solution enhances the H2S
mass transfer in the liquid phase. Bonnin [7], who worked on
the elimination of sulphur compounds by chlorine in a packed
tower, found that four moles of Cl2 are necessary to remove one
mole of H2S.