With its wide-ranging ability to measure hydrogen sulphide from % levels down to ppb levels, the Diteco NovaSulf HG400 range from HMA INSTRUMENTATION can be utilised in many process industries, including natural gas pipelines (reformer recycle gas, LPG) and offshore gas production (fuel gas monitoring, flare gas).
A reel of paper tape impregnated with lead acetate is exposed to the gaseous process sample in the sample chamber. Hydrogen sulphide in the process sample reacts with the lead acetate after acidification to form lead sulphide, a brown compound that stains the tape. The higher the concentration of hydrogen sulphide, the darker the stain. A focused LED and single photo detector measure the darkening stain, while the analyser reports this as a 4-20mA output of the concentration of hydrogen sulphide. Incremental measurements are made on the same spot until saturation occurs, when the tape is advanced to a fresh section, obviating the need for frequent zero or span calibrations.