Sulfa-Check process uses sodium nitrite (NaNO2) in aqueous solution to oxidize H2S to sulfur. This process was developed and patented by NL Treating Chemicals and is now a product of Exxon Energy Chemicals. It will generate NOX in presence of CO2 and O2. Therefore, local air quality emission standard should be consulted. This process is most suited for small gas streams, generally 0.1 to 10 MMscfd and containing 100ppmto< 1%H2S.
Sulfa-Check gas sweetening process is generally carried out in a contact tower. The sour gas flows into the bottom of the tower and through a sparging system to disperse the gas throughout the chemical solution. The maximum linear gas velocity should be < 0.12 ft/sec. The sweetened gas exits the contact tower at the top and goes to a gas/liquid separator to catch any liquids that may be carried over. An inverted U with a syphon breaker on top should be designed into the gas inlet line to prevent the liquid from being siphoned back. When the chemical is spent, the system is shut down to remove the spent chemical and recharged with a fresh solution to resume the operation.