Beavon process

Alternative means for removal of carbonyl sulfide for gas streams iavolve hydrogenation. For example, the Beavon process for removal of sulfur compounds remaining ia Claus unit tail gases iavolves hydrolysis and hydrogenation over cobalt molybdate catalyst resulting ia the conversion of carbonyl sulfide, carbon disulfide, and other sulfur compounds to hydrogen sulfide (25). 

Another variation of the Selectox process can be used with the Beavon process in tail gas treating. The hydrogenated Claus tail gas stream is sent to a Selectox reactor. Overall recoveries of up to 98.5% are possible. Use of Beavon/Selectox, however, typically costs more than use of Superclaus. 

Selectox Also called BSR/Selectox. A process for converting hydrogen sulfide in refinery gases to elemental sulfur. The gases are passed over a fixed bed of a proprietary catalyst (Selectox 33) at 160 to 370°C. Claimed to be better than the Claus process in several respects. Often used in conjunction with the Beavon process. Developed by the Union Oil Company of California and the Ralph M. Parsons Company, and first operated in 1978. Thirteen units were operating in 1996. 

Since the Claus process by itself removes only about 90% of the hydrogen sulfide in the gas stream, the Beavon process (Speight, 1993, p. 268), SCOT (Shell Claus Off-Gas Treating) process (Speight, 1993, p. 316 Hydrocarbon Processing,... 

The heart of the Beavon process is a catalytic reactor which converts essentially all of the sulfur in the tail gas to hydrogen sulfide either by hydrogenation or hydrolysis. Hydrolysis reactions are typified by Reactions 2 and 3 ... 

Introduction. The Beavon Sulfur Removal (BSR) process, as repotted by Beavon and King (1970) and Beavon and Vaell (1971), is capable of reducing the total sulfur content of Claus unit tail gases to less than 250 ppm by volume (calculated as sulfur dioxide) and thus of attaining an overall conversion of more than 99.9% of the hydrogen sulfide fed to the Claus unit. The residual sulfur compounds from the Beavon process consist almost entirely of carbonyl sulfide, with only traces of carbon disulfide and hydrogen sulfide. The effluent gas is practically odorless and can often be vented directly to the atmosphere, obviating the need for incineration and the attendant consumption of fuel. 

The Beavon Sulfur Removal (BSR) process was developed jointly by the Parsons Coip. of Pasadena, California, and the Union Oil Company of Califoinia (now Unocal Corporation of Los Angeles, California). The term Beavon process refers to a group of processes utilized for the removal of residual sulfur compounds from Claus plant tail gases. This family of processes has in common an initial hydrogenation and hydrolysis unit to convert all residual sulfur compounds to H2S. Individual processes within this family differ from each other in the technology used to remove the H2S from the Claus tail gas stream. Process improvements and operating experience have been reported by Andrews and Kouzel (1974). Fenton et al. (1975), Beavon and Brocoff (1976), and Kouzel et al. (1977). 

Process Description. The Beavon process H2S conversion step is carried out at elevated temperatures over a cobalt-molybdate catalyst and involves hydrogenation and hydrolysis of sulfur compounds according to equations 8-10 through 8-15. 

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