Claus tail gas

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. 

Recover sulfur from coke oven gas. Recycle Claus tail gas into coke oven gas system. 

ATS [Ammonium thiosulfate] A process for removing residual sulfur dioxide from Claus tail gas by absorption in aqueous ammonia to produce ammonium sulfite and bisulfite. Addition of hydrogen sulfide from the Claus unit produces saleable ammonium thiosulfate. Developed by the Pritchard Corporation and first operated by the Colorado Interstate Gas Company at Table Rock, WY. 

Beavon Hark 11 Parsons H2S content of <5Z or Claus tail gas Up to 99% overall sulfur recovery. Some COS and CS2 conversion... 

In the SCOT process, the sulfur compounds in the Claus tail gas are converted to hydrogen sulfide by heating and passing it through a cobalt-molybdenum catalyst with the addition of a reducing gas. The gas is then cooled and contacted with a solution of diisopropanolamine (DIPA) that removes all but trace amounts of hydrogen sulfide. The sulfide-rich diisopropanolamine is sent to a stripper, where hydrogen sulfide gas is removed and sent to the Claus plant. The diisopropanolamine is returned to the absorption column. 

Since the Selectox process is capable of well over 90 percent sulfur recovery, the authors recommend a careful cost-benefit study to see if Claus tail gas processing should be required with such plants. It might well be found that—say—95 percent capture of sulfur in the coal conversion plant is acceptable. 

Environmental regulations may force the "Claus" sulfur recovery to exceed 99%, requiring tail gas treatment. High CO2 in the original Claus feed, hence in the Claus tail gas, works strongly against the tail gas processes which use amine solution to extract H2S, and subsequently require incineration of residual H2S in a large volume of CO2. 

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. 

The SCOT Process has been accepted by industry as an excellent means of reducing Claus tail gas sulfur emissions. 

Oil refineries and natural gas plants often produce large amounts of hydrogen sulfide, The most applied process for converting this hydrogen sulfide imo elemental sulfur is the modified Claus process. However, 3 to 5% of the H2S feed is not converted into sulfur and has to be treated alternatively. At the University of Utrecht a new catalytic process has been developed to oxidire hydrogen sulfide in Claus tail gas selectively to sulfur [ I,2 ... 

Because Claus tail gas contains large concentrations of water vapour (up to 30%), the equilibrium results in appreciable concentrations of H2S and SO2-... 

Removal of SO2 from actual boiler fiue gas was first tested in a 1500 ft /hr, 6-inch diameter unit operating on a slipstream from a 50 MW oil-fired boiler. This equipment was operated satisfactorily around-the-clock for periods as long as one week. Scaled up 18-inch diameter adsorbers, capable of handling gas rates of 20,000 ft /hr, also have been operated satisfactorily on fiue gas from an oil-fired boiler and on simulated Claus tail gas. Data from these continuous units showed SO2-removal capabilities to as low as 50 ppm. 

G. Bandel and W. Willing, The Doxosulifreen claus tail gas processes - meeting enhanced sulphur emission standards . Sulphur 96, loose paper. 

A new catalyst for the selective oxidation of hydrogen sulfide in Claus tail gas to elemental sulfur has been developed. The catalyst consists of highly dispersed iron oxide supported on a silica carrier. During operation the activity of this catalyst decreases due to transformation of iron(III) oxide into a less active component. X-ray diffraction, wet chemical qualitative analysts and Mossbauer spectroscopy reveal the component comprises iron(II) sulfate. Although the transformation of inon(III) oxide into iron(IQ sulfate causes deactivation, the increase in selectivity results in high sulfur yields (up to 94%). 

A number of commercial plants are now using the Beavon sulfur removal process to convert the sulfur content of Claus tail gas first to hydrogen sulfide and finally to elemental sulfur. These plants reduce the sulfur content of the tail gas from about 1—3% to less than 100 ppm of which less than 1 ppm is present as hydrogen sulfide. The foregoing con-... 

Table I. Typical Analysis of Sulfur from IFP-1500 Claus Tail Gas Clean-up Plants...

P. H. Berben, et ai, "Deactivation of Claus Tail-Gas Treating Catalysts", in Catalyst Deactivation, eds. Delmon Froment, Elsevier, Amsterdam, 1987, pp. 303-316. 

Regulations regarding the sulphur contents of petroleum products and sulphur emissions from the refinery, mean that most of the sulphur is now recovered in Claus and Claus tail gas units in the refinery in the form of elemental sulphur. 

Goar, B.G., Current Claus Tail Gas Clean-up Processes, Proceedings of the 57th Annual GPA Convention, New Orleans, LA (March 20-22, 1978). 

UCARSOL HS Iff Sohrent vs. DIPA in Claus Tail Gas Cleanup Unit ... 

The process has been tested in a mobile pilot plant capable of treating 200 m /h of gas over a wide range of SO2 concentrations. This unit has been operated on a coal-fired boiler in Eastern Europe. A 3,400 Nm% commercial unit is planned for a Claus tail gas application at an Esso (Exxon) refinery in Norway (Ulset and Erga, 1991 Peterson, 1992). 

The ATS process is claimed to be competitive with existing Claus tail gas technology for removing and recovering sulfur compounds. However, the economics must be calculated for each specific location since the cost of ammonia and the selling price for the ammonium thiosulfate solution vary wideiy. 

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