DISCRETE SAMPLING APPROACH FOR H2S SO2 ANALYSIS IN SULFUR RECOVERY PLANTS

A major challenge in sulfur recovery plants is the operation and maintenance of analysis systems for the measurement of the hydrogen sulfide (H2S) and sulfur dioxide (SO2). The presence of elemental sulfur in this process requires that the sample be heated to approximately 150 degrees C. The sulfur will readily condense if there are any cold spots in the sample system. Many hours of maintenance time have been spent in the operation and maintenance of tail gas analyzers. The purpose of this paper is to present a new sampling approach to the H2S/SO2 analysis system. This new approach features the combination of a discrete sample valve, a UV process photometer and an analyzer controller. The discrete sample valve provides a ''plug'' of sample which is diluted with carrier gas. The UV photometer serves as a detector for the H2S and SO2 analysis peaks. The analyzer controller controls the analysis method and injection of the sample. The cycle time for this analysis is approximately one minute. This new system has been on-line for over one year at a refinery test site and it has provided reliable performance that is virtually maintenance-free.