Superclaus process

Basically there are two different conventional Claus processes, the straight-through process and the split-flow process. For gas mixtures containing 50-100 mol-% H2S the straight-through process is recommended, for the other mixtures the split-flow process is more appropriate. Both processes will be treated in some more detail below [2], Several modifications to the original Claus process have been developed in the mean time. One of them, the Superclaus process is also treated below, for other variations on the conventional process, the interested reader is referred to [2],... 

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],... 

In the so-called Superclaus process, the last catalytic converter of the conventional Claus process is replaced by a catalytic converter containing the Superclaus catalyst . This catalyst consists of an a-alumina support with iron and chromium oxides as catalytic material. The Superclaus catalyst is highly selective for the direct oxidation of hydrogen sulphide ... 

The sulfur yield is between 96% (with two catalytic reactors) and 98% (with three catalytic reactors). The tail gases from Claus plants have to be cleaned, for which there are a number of processes. In the so-called Superclaus process a yield of up to 99.5% is obtained by using improved catalysts. 

Claus plant tail gas is normally quite dilute, and more concentrated H2S streams can be made dilute by recycling product gas. When direct oxidation is used in conjunction with a conventional Claus plant it is necessary to assure that essentially all sulfur in the tail gas is in the form of H2S. This can be accomplished by operating the Claus system with slightly less than the stoichiometric amount of air or by providing a separate hydrogenation/hydrolysis step to convert sulfur compounds to H2S before direct oxidation. Commercial direct oxidation processes include the Superclaus process offered by Comprimo, the Selectox process offered by Unocal/Parsons, Mobil s MODOP process, and the previously discussed Catasulf process. 

The Superclaus process can be used in combination with other Claus process modifications, such as Recycle Selectox and COPE, to achieve higher overall sulfur recovery, and with tail gas units such as BSR/Stretford and SCOT to save utility costs by reducing the sulfur load. 

A sulfur condenser follows the reactor. These processes, ie, Superclaus or Parson s Hi-Activity process, can boost the overall sulfur recovery to up to 99.2%. 

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. 

Comprimo A version of the Claus process offered by Comprimo Engineers Contractors, The Netherlands. In 1983, plants using this process were being installed in Italy, Kuwait, France, and Japan. See also Superclaus. 

In a Claus plant plant H2S is converted into sulfur however, the conversion is not complete (94-98%). About 1% H2S and 0.5% COS remain in the off-gas due to the thermodynamics of the Claus equilibrium reaction. Van Nisselrooy and Lagas [162] developed a catalytic process, called Superclaus, which is based on bulk sulfur removal in a conventional Claus section, followed by selective catalytic oxidation of the remaining H2S to elemental sulfur. Iron oxides and chromium oxides supported... 

The Claus reaction continues in the catalytic step with activated aluminum(III) or titanium(IV) oxide, and serves to boost the sulfur yield. More hydrogen sulfide (H2S) reacts with the SO2 formed during combustion in the reaction furnace in the Claus reaction, and results in gaseous elemental sulfur. About one-third reacts via Eq. (34.11) and two-thirds via Eq. (34.12). Further process modification such as the COPE, Lurgi OxyClaus, BASF Catasulf, and Superclaus were described by Kohl and Nielsen [21]. 

Figure 8-23. Superclaus 99 and 99.5 processes (Lag etal., 198. Reproduced with permission from Hydrocarbon Processing...

With one thermal stage and two catalytic Claus stages upstream of the Superclaus selective oxidation stage, an overall sulfur recovery of 99.0% is claimed for a rich feed gas. The process licensor reports that the capital cost of this configuration is approximately 5% greater than that of a typical three-stage Claus plant. With the addition of a further Claus... 

With a rich feed gas and two Claus catalytic stages, the Superclaus 99.5 process is claimed to be capable of a minimum overall sulfur recovery of 99.2%. The process licensor claims that this is obtained with a capital investment that is about 20% greater than that required for a typical three-stage Claus plant. A minimum overall sulfur recovery of 99.4% is claimed when three Claus reactors are included, for an investment repotted to be about 30% greater than that for a typical three-stage Claus plant. 

Goar, B. G., Lagas, J. A., Borsboom, J., and Heijkoop, G., 1991, Superclaus Updates How the Process is Performing, Worldwide, paper presented at British Sulphur s 19th International Conference, New Orleans, LA, November 17-20. 

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