An innovative way to recover elemental sulfur from SO2 emissions

Sulfur dioxide emissions from metals smelters and other process plants are typically treated by converting the SO2 to sulfuric acid, but this may not be convenient, because of the shipping cost for plants located far from an acid market. WorleyParsons (Monrovia, Calif.; www.worleyparsons.com) offers a solution to this problem with a process that converts SO2 to elemental sulfur, which is easier and safer to ship. WorleyParsons’ process works with a pure SO2 stream that is extracted from the offgases by an amine-based concentrator. After that, the process has two steps, both of which use conventional technologies. In the first step, methane is reacted with liquid sulfur in an externally fired tube heater at about 650°C to obtain hydrogen sulfide and carbon disulfide (see figure). The H2S is then reacted with the SO2 stream to produce elemental sulfur by the Claus process. The Claus reaction takes place over two or three alumina-filled beds, says Helmy Andrawis, vice-president and process engineering manager. CS2 is converted to H2S by hydrolysis, using water produced in the process. “The only piece missing (compared to a standard Claus plant) is the reaction furnace to make SO2,” says Andrawis. “We don’t…