Hydrogen Sulfide is a highly toxic and flammable gas. Being heavier than air, it tends to accumulate at the bottom of poorly ventilated spaces. Although very pungent at first, it quickly deadens the sense of smell, so potential victims may be unaware of its presence until it is too late. The lethal concentration for 50% of humans is 800ppm for 5 minutes of exposure. H2S is a by-product in many hydrometallurgical processes. Macrotek has done many systems for some of the major multi-national mining giants all over the world and has developed a unique two stage process that has been successfully applied to several of these systems.
The two stage system allows for maximum concentration of sulfide by-product (which is re-used in the production) and maximum removal efficiency. The first stage is operated at a relatively neutral pH level. The reagent is injected in the second stage, which results in very high pH operation in this zone. This set up allows manipulation of the H2S in the gas, and sulfide in the liquid equilibrium, resulting in optimum removal and minimum reagent utilization.