Hydrogen sulphide removal in waste water treatment plant by compact oxidative scrubbing in Aquilair Plus™ process

Recently, the development of a high voidage contactor, named Aquilair Plus™, has demonstrated high efficiency for chemical scrubbing of hydrogen sulphide. Liquid and gas phases flow at co-current and high velocity, leading to a great dispersion of the liquid and then to an enhancement of the mass transfer rate by comparison with classical packed towers. This study focused on the results which obtained at semi-industrial scale with the Aquilair Plus™ process on a waste water treatment plant located in France. The scrubbing liquid consisted of a sodium hypochlorite alkaline solution. At once, pressure drop, H₂S removal and reagents consumption were followed. The influence of the superficial gas velocity, liquid-to-gas mass ratio (L/G), pH, hypochlorite concentration of the scrubbing liquid and H2S inlet concentration was characterised. H₂S removal percentages higher than 90% could be easily achieved with a moderate pressure drop (< 40 mbar). Both hydrodynamic and chemical conditions proved to influence performances. Reagents consumptions slightly higher than the predicted ones were measured.