Claus Shell

When the Claus reaction is carried out in aqueous solution, the chemistry is complex and involves polythionic acid intermediates (105,211). A modification of the Claus process (by Shell) uses hydrogen or a mixture of hydrogen and carbon monoxide to reduce sulfur dioxide, carbonyl sulfide, carbon disulfide, and sulfur mixtures that occur in Claus process off-gases to hydrogen sulfide over a cobalt molybdate catalyst at ca 300°C (230). 

A bleed from the scmbbing system is sent to a sour slurry stripper. The water is then clarified and can be recycled to minimize the volume of effluent to be biotreated and discharged or evaporated. The acid gas from the acid gas removal system and from the sour slurry stripper is fed to a Claus plant, where salable elemental sulfur (qv) is produced. For maximum sulfur recovery and minimal sulfur emissions, the Shell Claus off-gas treating process (SCOT) is used. 

Claus Process Parsons, Shell, Amoco Normally 15-20% HjS Production Co., through or more, with product Its licensees such as sulfur-burning, can Ford, Bacon Davis, handle H2S contents Ortloff, Olsen, and down to 5% many others 92 97% removal with 3 catalytic stages. COS CS2 not converted without provisions in design... 

SCOT Shell Development Co. Claus tall gas 99.8% overall sulfur recovery if COS/CS2 content is not excessive. <300 ppmv sulfur compounds in treated gas. H2S is about 150-200 ppmv... 

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,... 

Reductive Tail Gas Treatments. It was largely as a result of the effort to achieve better than 99% recovery that the reductive tail gas desulfurization processes (46) were developed in the 1970 s. The two main methods are the Beavon Sulfur Removal (BSR) (47) and the Shell Claus Off-Gas Treatment (SCOT) (48) processes. Both of these processes are now widely used as tail gas desulfurization units on sulfur recovery plants and can readily achieve point source emission levels below 250 ppm and below 100 ppm if necessary to meet regulatory standards. 

Claus process A process for obtaining sulfur from the H2S in oil wells by the oxidation of H2S with S02 the latter is formed by the oxidation of H2S with oxygen, closed shell (or subshell) A shell (or subshell) containing the maximum number of electrons allowed by the exclusion principle. Example the neonlike core 1s22s22 p6. 

Scaling Up from Laboratory Data Laboratory experimental techniques offer an efficient and cost-effective route to develop commercial absorption designs. For example, Ouwerkerk (Hydrocarbon Process., April 1978, 89-94) revealed that both laboratory and small-scale pilot plant data were employed as the basis for the design of an 8.5-m (28-ft) diameter commercial Shell Claus off-gas treating (SCOT) tray-type absorber. Ouwerkerk claimed that the cost of developing comprehensive design procedures can be minimized, especially in the development of a new process, by the use of these modern techniques. 

The H2S concentration in the tail gas of a conventional Claus plant is still some 5%. This H2S is normally incinerated to S02 and released to the atmosphere. Due to stricter environmental regulations a large number of new technologies based on Claus tail gas treatment have been developed to minimise the S02 exhaust from sulphur recovery units. The Superclaus process and the Shell Claus Off-Gas Treating (SCOT) process are treated below. For descriptions of other tail-gas processes, the reader is referred to [2],... 

The acid gas from the Sul find regenerator must be disposed of in an environmentally acceptable manner. The Claus process offers an effective means for converting nearly all of the sulfur in the acid gas to saleable elemental sulfur. The tail gas from the Claus plant still contains some sulfur compounds. To minimize sulfur emissions from the plant, the Claus tail gas can be fed to a Shell Claus ff-gas Jreating (SCOT) unit where most of this sulfur is recovered and recycled to the Claus plant. With use of the SCOT Process, additional marketable sulfur is recovered within the Claus plant while tail gas sulfur emissions are substantially reduced, to typically less than 250 ppmv. 

Shell also offers for license a -selective version of the Shell ADIP Process. The ADIP process, which has a flow scheme very similar to Sulfinol, can be used to treat the Sulfinol acid gas to raise the H2S concentration by selectively rejecting the CO2. Some integration of the SCOT process with the ADIP process is often possible thus, reducing overall equipment and operating costs. Costs for the Claus plant are substantially reduced when "selective" ADIP is applied. Two selective ADIP plants are scheduled to come on stream in the first half of 1979. 

Sulfur recovery can be achieved using the industrially proven Claus and SCOT (Shell Claus Off-gas Treating process) processes where the absorbed H2S is recovered as elemental sulfur via the following reactions ... 

Traditionally, acid gas treatment has required two separate processes. One is to remove hydrogen sulfide and the other is to convert the concentrated hydrogen sulfide stream to sulfur. A new process called the SulFerox process, developed by Shell Oil Company and The Dow Chemical Company, now offers a single process that handles both steps. The process has high degree of flexibility and requires a smaller capital investment than the Amine/Claus process. Chelated iron compounds are the heart of the process and the chemistry allows an aqueous solution of iron in high concentrations. As a result, circulation rates are low and equipment size is very small for the capacity. Figure 5.1 shows a schematic of the SulFerox process [76]. 

The elemental sulfur that is formed in the primary reactor system is condensed in a horizontal shell-and-tube steaming condenser (17). This represents over 40% of the total recovered sulfur. The process gas stream then enters the first stage (18) of a two-stage Claus reactor system where the following exothermic reaction occurs ... 

The Shell Claus Offgas Treating (SCOT) Process... 

The SCOT process was first made public in September 1972, at a technical meeting in Japan by Shell Internationale Research Maatschappij (SIRM). Shell had proved the effectiveness and life of the catalyst in the reduction step in bench-scale work at their Amsterdam laboratory and a semi-commercial demonstration on Claus SRU tail gas at Shell s Gor-dorf, Germany refinery. Confidence in the effectiveness and selectivity of the amine absorption step was based on Shell s extensive use of the ADIP process in worldwide applications bolstered by laboratory bench-scale testing. 

The Scot Process (SHELL Claus Off-gas Treating) developed by SHELL Internationale Maatschappij already in 1971 uses two steps ... 

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