Plasmas for destruction of H2S and mercaptans

Plasmas are reviewed as activation media for an oxidation of H2S or CH3SH d iluted in air, CO2 or steam in order to convert them into less malodorous S O2. The product can be then used as a reagent in a Claus-like process in pr esence of water to convert twice as much of initial pollutants into element al sulfur. A particular attention is devoted to the gliding electrical disc harges (GlidArc). These powerful discharges produce non-thermal plasma, whi ch activates oxidation reactions. Most of experiments were performed using one and four-stage GlidArc-I reactors. Air-diluted sulfides at initial conc entrations up to 1% (H2S) or 0.1% (CH3SH) were processed at up to 70 m(3)(n )/h flow rate and 5 kW power scale. The tests were done at 1 atm. Up to 100 % clean-up was obtained at a quite low energy cost depending on initial pol lutant concentration: roughly 1000 kWh per 1 kg of removed sulfur at 100 pp m of H2S, but only 10 kWh/kg for 1% initial H2S in air. Almost the same ene rgies were needed in the case of CH3SH-air mixtures. Using a very simple wa shing column in which water saturates with the produced SO2 and so captures unprocessed H2S we cut these process energy by three, avoiding the SO2 emi ssion and obtaining non-toxic sulfur. New development based on GlidArc-II b rush-like electric discharges is also presented. Preliminary tests are very promising as the energy expense is already cut down by a factor of two wit h respect to the GlidArc-I devices. Up to industrial scale tests can be the refore performed.