Control of foaming in hydrogen sulfide/water mixtures

Hydrogen sulfide/water mixtures are frequently encountered in the petrochemical and heavy water industries. Such mixtures exhibit an inherent foaminess when operating close to the liquefaction pressure of H2S. This can cause severe problems in fluid handling equipment. The foaming is associated with the adsorption of several layers of H2S molecules on the bubble interface thus giving the bubble rigidity and stability. Foaming is further increased by the presence of certain trace impurities in the water. Some nonionic surfactants are effective antifoams for these mixtures. The antifoam action is due to surfactant micelle formation which is enhanced by the presence of H2S through a ''salting out'' mechanism. The pressure at which a particular surfactant becomes an antifoam can be predicted from the hydrophobicity of the surfactant molecule. Such understanding could be applied to control foaming in other systems