Sour natural gas

Hydrogen sulfide has been produced in commercial quantities by the direct combination of the elements. The reaction of hydrogen and sulfur vapor proceeds at ca 500°C in the presence of a catalyst, eg, bauxite, an aluminosihcate, or cobalt molybdate. This process yields hydrogen sulfide that is of good purity and is suitable for preparation of sodium sulfide and sodium hydrosulfide (see Sodium compounds). Most hydrogen sulfide used commercially is either a by-product or is obtained from sour natural gas. 

The Claus process, which involves the reaction of sulfur dioxide with hydrogen sulfide to produce sulfur in a furnace, is important in the production of sulfur from sour natural gas or by-product sulfur-containing gases (see Sulfurremoval and recovery). 

J. N. Robiason, "Estimation of the Water Content of Sour Natural Gas," presented at Canadian Natural Gas Processing Association, Calgary, Alberta,... 

This graphical method was developed for field operations personnel. It is designed for sour natural gas at 100 to 4,000 psia up to 50% H2S or sweet gas with C3 up to 10%. 

Figure 1. Imperial unit hydrate chart for sour natural gas.

Sulfur first produced from sour natural gas by 1971 this source, together with crude oil, accounted for nearly... 

In the Introduction it has already been mentioned that sulfanes are likely to occur in underground sulfur-rich deposits of sour natural gas. This gas is freed from H2S by washing with an alkaline solvent from which the hydrogen sulfide is later expelled by heating. The Claus process is then applied to convert H2S into elemental sulfur ... 

Sulfur for commercial purposes is derived mainly from native elemental sulfur mined by the Frasch process. Large quantities of sulfur are also recovered from the roasting of metal sulfides and the refining of crude oil, i.e., from the sulfur by-products of purified sour natural gas and petroleum (the designation sour is generally associated with high-sulfur petroleum products). Reserves of elemental sulfur in evaporite and volcanic deposits and of sulfur associated with natural gas,... 

Sublette [285] describes a process for desulfurizing sour natural gas using another commonly known chemolithotrophic microorganism, the aerobic bacterium T. denitrifi-cans. This patent describes a process wherein bacteria of the Thiobacillus genus convert sulfides to sulfates under aerobic conditions. Sublette defined the ideal characteristics of a suitable microorganism for the oxidative H2S removal from gaseous streams as ... 

A sour natural gas stream can be anaerobically desulfurized by a process, which employs a consortium of chemoautotrophic bacteria (ATCC 202177). The H2S and other sulfur species are converted into elemental sulfur, which is recovered as a product [287], The process conditions involve pressures lower than 1000 psi and temperatures up to 60°C. Sulfur content might be diminished from 10,000 ppm H2S to pipeline standards of <4ppm. Further, C02 content can be reduced as well from levels as high as 10% to <2%. 

Sour natural gas, 23 597 Sour syngas defined, 6 829 Sour taste, 11 566 South Africa, platinum-group metal deposits in, 19 604, 612 South African gold mines, 12 686 South African manganese mining, 15 555 South America... 

The first major attempt at precombustion desulphurisation was in the coal gas industry and a number of efficient and effective techniques for removal of H2S, COS, CS2, mercaptans and other volatile sulphur containing products of the gasification process were developed. Many of these techniques found application in the subsequent development of sour natural gas processing where large volumes of hydrogen sulphide had to be removed from the hydrocarbon component. 

Alkanolamines have been widely used for removal of H2S from sour natural gas. Monoethanolamine (MEA) was typically used to react with the acidic H2S to form the alkanolammonium sulphide. This salt could be readily removed... 

Elemental sulfur1-4 occurs naturally in association with volcanic vents and, in Texas and Louisiana, as underground deposits. The latter are mined by injecting air and superheated water, which melts the sulfur and carries it to the surface in the return flow (the Frasch process). Most of the sulfur used in industry, however, comes as a by-product of the desulfurization of fossil fuels. For example, Albertan sour natural gas, which often contains over 30% (90%, in some cases) hydrogen sulfide (H2S), as well as hydrocarbons (mainly methane) and small amounts of C02, carbonyl sulfide (COS), and water, is sweetened by scrubbing out the H2S and then converting it to elemental S in the Claus process.5 The Claus process is applicable in any industrial operation that produces H2S (see Section 8.5) it converts this highly toxic gas to nontoxic, relatively unreactive, and easily transportable solid sulfur. 

Hydrogen sulfide enters natural waters from decay of organic matter (e.g., in swamps), bacterial reduction of sulfate ion, or underground sour natural gas deposits. It can be removed by aeration, anion exchange (Eq. 14.14), or oxidation by chlorine to elemental sulfur ... 

The production of domestic sulfur values (elemental recovered sulfur and the sulfur content of acid) will total about 18 million long tons per year by the year 2000. By region (Petroleum Administration for Defense districts), except for the east coast (PAD I), there will be no deficit areas in the U. S. Major contributors are sour natural gas and the refining of heavier, sour, crude oil. Proximate, scenario dependent sources, are electric utilities and coal-based synfuels. Shale oil, domestic tar sands and heavy oil, and unconventional sources of natural gas will be small suppliers. 

Energy demand, the implementation of sulfur oxide pollution controls, and the future commercialization of coal gasification and liquefaction have increased the potential for the development of considerable supplies of sulfur and sulfuric acid as a result of abatement, desulfurization and conversion processes. Lesser potential sources include shale oil, domestic tar sands and heavy oil, and unconventional sources of natural gas. Current supply sources of saleable sulfur values include refineries, sour natural gas processing and smelting operations. To this, Frasch sulfur production must be added. 

Table II presents a distributed, scaled, estimate of future sulfur production from sour natural gas based on Manderson (22).

FORECAST SULFUR PRODUCTION FROM SOUR NATURAL GAS... 

Finally, if current expectations of future sulfur prices are in continued excess of 100/long ton, the development of very sour natural gas wells (> 60% H2S) may be anticipated. The methane content, even if gas prices remain controlled, becomes secondary. 

On a qualitative basis, the estimates of recovered sulfur from refinery operations appear to be the most secure. Except for district IV, which depends heavily on the ultimate productivity of the Overthrust Belt, estimates of sulfur production from sour natural gas also seem reliable. The heavy crude oil sulfur output estimate is reasonably firm. Oil shale, tar sands, heavy oil and in situ coal combustion will produce little sulfur even under optimistic scenarios. The smelter acid projection is weak. Metal output may... 

In view of the domestic estimates, imports are almost redundant, It appears likely, however, that by 1985-1990 Canada will have about one million additional short tons of acid available for export. At least some would be available in PAD districts I and II, Furthermore, sulfur production from sour natural gas and tar sands is likely to increase. As transport problems are mitigated and formed sulfur gains acceptance, Canadian output will become available to districts I, II, and IV. Excluding the existing stockpile, the estimate for tar sands and heavy oil is... 

The sour natural gas sulfur recovery industry covers virtually the entire gamut of chemistry. From the sour gas reservoir to the Claus plant end product problems are encountered in thermodynamics, kinetics, corrosion, catalysis, redox, rheology and the environment - plus all the rest In reviewing recent developments in such a wide ranging field it is only possible to select examples. It is hoped, however, that these highlights will serve to illustrate the dynamism of the industry in recent years and the progress it has made in developing a new source of one of the world s most basic and essential elements in an environmentally acceptable manner. 

Crude oil represents the largest non-Frasch sulfur resource and this source has received added stimulus from the passage of air pollution control laws and increased refining of heavier, high sulfur crudes. Sulfur recovered from sour natural gas contibutes a third source of by-product sulfur. 

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