Remove hydrogen sulfide (H2S) and hydrogen poly-sulfides (H2Sx) dissolved in liquid sulfur. Safety: Hydrogen sulfide is a highly toxic and potentially explosive gas. A concentration of 600 ppmv is lethal and is explosive at approximately 3.5% vol. Dissolved H2Sx is decomposed, and H2S is released in storage, during loading and unloading and also during transportation, thus leading to potentially dangerous conditions.
Product: Liquid sulfur containing 10 ppmw of H2S or less.
Liquid sulfur flowing from the Claus plant to the sulfur pit contains typically 250–350 ppmw of H2S + H2Sx. Sulfur is degassed using an active gas-liquid contacting system to release dissolved gas. Adding chemicals is not required. Sulfur from the pit is pumped into the degassing tower where it is contacted counter-currently with hot compressed air over a fixed catalyst bed. Degassed sulfur is returned to the product section of the sulfur pit.
Operating conditions: The operating temperature in the sulfur degassing tower can vary from 125°C to 150°C depending on the temperature in the sulfur pit. The operating pressure drop is around 0.3–0.5 bar. Treated sulfur has a residual H2S level in the range of 5–10 ppmw.
Materials of construction: Mainly carbon steel. Aluminized steel may be used for the degassing tower.
Licensor: BP AMOCO through SIIRTEC NIGI