Sulphur recovery

Total reduced sulphur (sulphur recovery plants) 15A... 

RSRP [Richards sulphur recovery process] A proposed modification of the Claus process in which liquid sulfur is used to cool the catalyst bed. Developed jointly by the Alberta Energy Company and the Hudson s Bay Oil Gas Company, but not reported to have been commercialized. 

SuRe [Sulphur recovery] A version of the Claus process in which the capacity of the plant is increased by using air enriched in oxygen in the production of the sulfur dioxide. There are two versions SURE SSB [Side Stream Burner], and SURE DC [Double Combustion], In the first, a small portion of the feed stream containing hydrogen sulfide is burnt sub-stoichiometrically in a second burner in the second, the hydrogen sulfide is oxidized in two stages, with cooling and sulfur separation between them. Both of these... 

In the coal gasification, as well as in the FT process massive amounts of CO are inevitably produced. CO is the main component of the off-gas in the Sulphur recovery plarft (see above) and in the Benfield plant (which scrubs CO2 from the Synthol tailgas). The latter source is the purer of the two. CO is used in fire extinguishers and the production of "dry ice". 

Grancher P., "Recent Advances in Claus Techniques for Sulphur Recovery from Acid Gases", 27th Canadian Chem. Eng. 

Syncrude s Sulphur Recovery Units are two parallel trains of the conventional Claus plant consisting of thermal conversion and three catalytic reactors in series. Air is supplied to the furnace to oxidize sufficient H2S to SO2 such that an H2S S02 ratio of 2.1 1 is effected (1). The sulphur recovery efficiency is designed for approximately 95% (2) however, experience to date, at near design capacity, has indicated 98% H2S conversions and 97% sulphur recoveries (1). 

Especially on sulphur recovery units and heavy crude oil service, there could be excessive seat leakage of 316 SST trims caused by sulphide corrosion/pitting. In this case retrofit the valve with, for instance, an Inconel 718 nozzle and disc insert (with high nickel content). In any case, make sure that a proper material selection for the service is used. 

The most commonly used process for sulphur recovery from H2S is the Claus process. This process was developed by C.F. Claus in 1883 [3], LG. Farbenindustrie AG modified the process in 1936 to its current lay-out, including a thermal and a catalytic separation step [4],... 

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],... 

Standards Support and Environmental Impact Statement. Volume 1 Proposed Standards of Performance for Petroleum Refinery Sulphur Recovery Plants", EPA Research Triangle Park, N.C. EPA Publication No. EPA-450/2-76-016-a, 1976. 

Palm, J. W. 1979. Sulphur Recovery Plant Operation, Sulphur 143, 34—39. 

Pollution Control in Claus Sulphur Recovery Plants, Sulphur. 109, 36, Nov./Dec. (1973). 

Along with natural gas, oil fields have other products. Hydrogen sulphide is the most abundant of the impurities. A small quantity in natural gas is desirable as a warning of leakage. When large quantities are present this sour gas is used to manufacture carbon black or is processed for sulphur recovery. Sometimes helium is present in useful quantities. Carbon dioxide is found in some fields. It is recovered and used in the manufacture of dry ice. 

Claus sulphur recovery with SCOT tailgas clean up... 

The offgas is cooled in a waste heat boiler and de-dusted in two electrostatic precipitators before being fed to the existing acid plant. Total sulphur recovery is in excess of 99%. 

Sulphur recovery consists of a hydrocyclone and two parallel flotation circuits. Normally, over 95% of the elemental sulphur is recovered in this circuit. Work is ongoing to improve the recovery of the finer sulphur size fraction. The sulphur concmtrate is dewatered on a belt filter, melted and passed through a molten sulphur filter to remove unreacted minerals and ash to produce a marketable sulphur product. 

One of the options to increase zinc production in the future is to refurbish and restart the 1 autoclave and run two autoclaves in parallel. The successful plant test with Red Dog concentrate, combined with anticipated improvements in sulphur recovery, makes this pressure leaching option very appealing. 

Kunkel, L.V., GPA H2S Removal Panel - Part 3, Claus Process Improvements in Sulphur Recovery, Oil and GasJ., 92-99 (August 7, 1978). 

Parnell, D.C., Claus Sulphur Recovery Unit Start-ups, Chem. Eng. Prog., 69 (8) (August 1973). 

Wright, R.D., and J.W. Strange, Modified Sulphur-Recovery Process Meets Air-Quality Regulations, Oil and GasJ., 99-102 (Febmary 22, 1978). 

Forbath, T. P. 1953. Sulphur Recovery From Low-Grade Surface Deposits, Mining Engineering, 5 881-885. 

In the Claus process Sulphur Recovery Units, metallic bellow expansion joints in the tail gas line to Incinerator, seldom fail by developing crack on the bellow element due to various mechanical and metallurgical reasons. 

For NGL plants, emissions usually come from gas sweetening units when acid waste gas is burned or incinerated. Most frequently, the acid waste gas is used as a feedstock in sulphur recovery units or in sulphuric acid plants. While flaring is often expected in NGL plants, the major poison and pollutant of concern is S02- Most plants employ elevated smokeless flares or gas incinerators for combustion of all waste gas constituent, including tail gas incinerator in which H2S is oxidized to SO2 (Berkel, 2000) [7]. Such practices are not sustainable. CP can be implemented to reduce and/or eliminate gas flaring or incinerations beyond acceptable level as stipulated by local environment authorities. 

An input/output model for AGRU revealed that there are two undesirable streams i.e. sour water and acid gas flare. These streams constitute CP issues that need to be addressed. For the GDU, an identified CP issue was to do with acid gas flare. In the SRU, a CP issue was to do with sulphur recovery. In summary, the common CP issues identifiesd in the case study were gas flaring, venting, acid gas incineration and sulphur incineration. The incinerated acid gas contains CO2 and H2S. This incineration leads to greenhouse gas emissions, acid rain, and hence contributes to global warming. 

The major limitation in sulphur recovery was due to the fact that the recovered stream consisted of 65% of CO2, and 35% of H2S. If richer with H2S, then recovery should theoretically increase. The specific recommendation made for this issue were as follows (i) to inject the acid gas after liquefaction in deep geological formation into natural gas reservoir, (ii) to separate the CO2 from the feed so that it is rich in H2S while CO2 is being injected to the gas reservoir, (hi) to separate the CO2 from the feed before entering the recovery imit in order to enhance the recovery. A viable solution to the C02 issue in the case study would be to utihze it as a feed stock for methanol production in another facility. 

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