Industrial Manufacturing of Aqueous Solutions of Sodium Sulfhydrate (NaHS 43%) in a Multi-Phase Reactor

Background: This research deals with the manufacture of sodium sulphides and sodium sulfhydrate in an isothermal multiphase chemical reactor to produce concentrated aqueous solutions of sodium sulfhydrate (greater than 43%) through Gas-Liquid-Solid reactions from hydrogen sulfide and hydroxide of sodium at 50%. Methods: A method is proposed that integrates the recovery of hydrogen sulfide from an industrial chemical process where the H2S gas is generated as a sub product, the strategy of the developed process was integrated into a manufacturing plant of dithiophosphoric acids (ADTF) where it was possible to recover the hydrogen sulfide in the form of an aqueous solution of NaHS with a concentration higher than 43%. Results: The experimental tests showed that the biphasic reaction mixture formed by Na2S, NaHS and H2O with global compositions of 13.3%; 26.9% and 59.7% respectively, is appropriate to obtain 43% sodium sulfhydrate in a stirred tank reactor, operated at temperatures ranging from 50°C to 55°C, where gaseous hydrogen sulfide is continually bubbled. Conclusion: Sodium sulfide (specifically Na2S.5H2O crystals) of the biphasic mixture is produced from a solution of sodium sulfhydrate (43% NaHS) and aqueous sodium hydroxide (50% NaOH). The environmental problem generated by the H2S was solved with a 90% recovery in the multiphase reactor and 5% in the safety absorber.