Purify tail gas from sulfur recovery units (such as Claus units) and other gas streams containing low concentrations of SO2. The type of process to be combined with the Beavon treatment depends on the intended disposition of the treated product gas (e.g., additional sulfur recovery, other component recovery, incineration or exhaust, while meeting stringent air pollution standards). Beavon processing converts sulfur compounds to H2S. Beavon-MDEA processing adds H2S separation. Beavon-Selectox processing converts H2S to elemental sulfur. Beavon-Hi-Activity processing converts H2S to elemental sulfur.
In the Beavon step, essentially all sulfur compounds in the feed gas (SO2, Sx, COS, CS2) are converted to H2S. The feed gas is heated (1) to reaction temperature by mixing with the hot combustion products of fuel gas and air. This combustion is carried out with a deficiency of air to provide sufficient H2 and CO to convert all of the sulfur and sulfur compounds to H2S. The heated gas mixture is then passed through a catalyst bed (2) where all sulfur compounds are converted to H2S by hydrogenation and hydrolysis. The hydrogenated gas stream is cooled in a steam generator (3), and then by direct contact (4) with a buffer solution before entering the selected H2S removal process.
Beavon-MDEA. One of several processes used to remove H2S is by absorption (5) in a solution of MDEA (methyl diethanolamine) or one of the recently developed highly selective amine type solvents. The clean tail gas contains less than 10 ppm H2S when using the newer solvents. When this combination is operating on a Claus tail gas, the separated H2S can be recycled to the Claus unit.
Beavon-Selectox. An alternative (6) for removing the H2S is to convert it to elemental sulfur by the Selectox process.
Beavon-Hi-Activity. Another alternate for removing the H2S is to oxidize it directly to elemental sulfur by the Hi-Activity process.
Operating conditions: All pressures are near atmospheric. The Beavon hydrogenation/hydrolysis reactor operating temperature is in the range of 550°F to 750°F. Equipment is essentially all carbon steel. Sulfur recovery of Claus plus Beavon-Selectox or Beavon-MDEA is more than 99% or 99.9%, respectively.
