Early evaluation of potential worker exposure problems associated with the Claus-type sulfur recovery process

Early evaluation of process plants, such as the Claus-type SRU (sulfur recovery unit), in the design stage not only minimizes worker exposure to toxic chemicals and noise, but also reduces costs for retrofit engineering controls. The Claus-type SRU converts the hydrogen sulfide in refinery acid gas into elemental sulfur. In the process, the SRU handles toxic gases containing high concentrations of H2S, SO2, and other sulfur compounds. These gases can be emitted into the worker's breathing zone during start-ups, shutdowns, routine operations, emergencies, and turnarounds. This paper describes the Claus-type sulfur recovery process, the potential sources of worker exposure to toxic chemicals and noise, and the engineering controls that should be adopted at the plant design stage to minimize the risks of worker exposure. Engineering controls include improved pump seals and a choice of sample configurations based on the physical form and concentration of H2S in the process lines.