When elemental sulfur is formed in a sulfur recovery unit H2S is entrained in the liquid sulfur as it runs into the sulfur pit. Polysulfide compounds in the liquid sulfur break down with time to additional H2S. H2S from these sources collects in the vapor space above the sulfur where it could exceed both toxic limits and the lower explosive limit. To prevent a dangerous H2S concentration from accumulating, most pits are air purged. Most plants run with an excessively low H2S level to be on the safe side and compressed air is expensive. In addition to the H2S hazards, the liquid sulfur itself can catch fire thereby spewing high concentrations of SO2 gas into the vapor space above the liquid sulfur. For safety purposes, it is necessary to monitor the vapor space above the liquid sulfur for H2S and SO2 gases.
The AMETEK 888 Sulfur Pit Analyzer measures H2S in the vapor space above the sulfur pit. Substantial cost savings can be made using this reliable analyzer to control the H2S level giving an adequate safety margin. Some customers also measure SO2 in the sulfur pit, reasoning that the presence of SO2 may indicate an incipient fire.
The AMETEK Model 930 H2S analyzer has been field proven as one of the industry’s most reliable instruments for monitoring H2S and SO2 where a remote mounted analyzer is desired. The Model 930 uses AMETEK proprietary high resolution NDUV technology in a dual beam, multiple wavelength configuration. Resolution better than 0.02 nm is provided by high intensity, line source lamps.
The Model 930 analyzer samples the vapor space gas using proven ASR Probe technology. The sampling system has a sulfur knock-out at the probe to eliminate entry of excess sulfur vapor or liquid into the system. The sample is then transported through an electrically traced sample line.