Sulfur in natural gas

Hydrogen can be produced by steam methane reformation (the most widely used process) or by off-gas purification. Hydrogen can be produced at normal purity (95-98%) or at ultra-high purity (99.99%). The first step to obtain pure hydrogen in the steam reformer process when using a natural gas feedstock is to perform a pretreatment. There are small amounts of sulfur in natural gas that must be... 

Organic sulfurs in natural gas and liquid fuels are poison to both the reforming catalyst and fuel cell s electrocatalysts. Many zeolites adsorb organic sulfurs and can efficiently remove these impurities from fuels. Sulfur removal by adsorption... 

D3031 Test Method for Total Sulfur in Natural Gas by Hydrogeneration ... 

Sulfur also occurs in natural gas and petroleum crudes and must be removed from these products. Formerly this was done chemically, which wasted the sulfur new processes now permit recovery. Large amounts of sulfur are being recovered from Alberta gas fields. 

In 1991, there were approximately 418 sulfur production plants associated with oil and gas production in operation throughout the world. Approximately 86% of these plants were based on the Claus process, and there were 118 Claus units operating in natural gas processing faciHties (11). 

Natural gas contains both organic and inorganic sulfur compounds that must be removed to protect both the reforming and downstream methanol synthesis catalysts. Hydrodesulfurization across a cobalt or nickel molybdenum—zinc oxide fixed-bed sequence is the basis for an effective purification system. For high levels of sulfur, bulk removal in a Hquid absorption—stripping system followed by fixed-bed residual clean-up is more practical (see Sulfur REMOVAL AND RECOVERY). Chlorides and mercury may also be found in natural gas, particularly from offshore reservoirs. These poisons can be removed by activated alumina or carbon beds. 

Sulfur constitutes about 0.052 wt % of the earth s cmst. The forms in which it is ordinarily found include elemental or native sulfur in unconsohdated volcanic rocks, in anhydrite over salt-dome stmctures, and in bedded anhydrite or gypsum evaporate basin formations combined sulfur in metal sulfide ores and mineral sulfates hydrogen sulfide in natural gas organic sulfur compounds in petroleum and tar sands and a combination of both pyritic and organic sulfur compounds in coal (qv). 

An accident complicated by fog, weak winds, and a surface inversion occurred in Poza Rica, Mexico, in the early morning of November 24, 1950, when hydrogen sulfide was released from a plant for the recovery of sulfur from natural gas. There were 22 deaths, and 320 persons were hospitalized. 

By far the most important sulfide is CS2, a colourless, volatile, flammable liquid (mp — 111.6°, bp 46.25°, flash point —30°, autoignition temperature 100°, explosion limits in air 1.25 50%). Impure samples have a fetid almost nauseating stench due to organic impurities but the purified liquid has a rather pleasant ethereal smell it is very poisonous and can have disastrous effects on the nervous system and brain. CSt was formerly manufactured by direct reaction of S vapour and coke in He or steel retorts at 750 1000°C but, since the early 1950s, the preferred synthesis has been the catalysed reaction between sulfur and natural gas ... 

Self-Test K.3A In the Claus process for the recovery of sulfur from natural gas and petroleum, hydrogen sulfide reacts with sulfur dioxide to form elemental sulfur and water 2 H2S(g) + S02(g) — 3 S(s) + 2 H20(1). Identify the oxidizing agent and the reducing agent. 

Because of their inherent penetrating smell, certain organic sulfur compounds are used for odorization. Repellents from the skunk contain compounds such as trans-2-butene-l-thiol and 3-methyl-1-butanethiol. Ethylmercaptan, because of its extremely low odor threshold, is the favorite compound used as an odorant in natural gas and liquid propane for leak detection. Tetrahydro-thiophene is also often used. Common odorization reagents are summarized in Table 15-1 and Figures 15-1 to 15-3. 

Haines A process for recovering sulfur from natural gas, using a zeolite adsorbent. The hydrogen sulfide in the gas is adsorbed on the zeolite when the bed is saturated, hot sulfur dioxide is passed through it. The zeolite catalyzes the reaction between hydrogen sulfide and sulfur dioxide to fonn elemental sulfur, which sublimes out and is condensed. The process was invented by H. W. Haines in 1960 it was developed by Krell Associates and piloted in Canada from 1961 to 1962, but not commercialized because of problems caused by fouling of the zeolite with heavy hydrocarbons. 

Sulfur concrete (SC), 23 592 Sulfur-containing compounds, in natural gas, 12 369... 

Sulfuric acid is number 1 by far, with a volume of over 90 billion lb produced yearly in the U.S. It is way ahead of number 2, nitrogen, which is produced at more than 75 billion lb annually. The highest volume organic chemical is ethylene, the basic petrochemical used to synthesize so many other important organic chemicals. It is the leader of the basic seven organics—ethylene, propylene, the C4 mixture, benzene, toluene, xylene, and methane—from which all other important organic chemicals are derived. Methane does not itself appear in the list because it is not synthesized by a chemical process. However, it is the major constituent in natural gas and is used to make many other chemicals. 

To circumvent such problems, up to two-thirds of the acid gas has been removed from the flame and sent directly to the catalytic reactor, the so-called "long bypass" scheme. This strategy has worked with mixed success in natural gas plants, where hydrocarbons in the acid gas are C1-C3 paraffins, chiefly methane, and no olefins. Such a configuration has been put forward for use in coal gasification plants. In the writer s opinion it is unworkable if the bypassed acid gas contains even traces of olefins or aromatics these compounds react with SO2 to form tarry products which foul the catalyst and discolor the product sulfur. 

World sulfur supplies are expected to grow at roughly 3.7% per year over the coming decade as compared with 2.6% per year from 1973 to 1980. Sulfur production will grow markedly in the United States, primarily due to increased recovery of sulfur from natural gas processing and petroleum refining. 

The speciation of the gas-phase sulfur depends on the parent fuel and the reaction conditions [204]. The sulfur-containing compounds occurring in combustion range from simple species such as H2S in natural gas and produced from gasification of solid fuels to com-... 

Figure 24-20 Gas chromatograms showing sulfur compounds in natural gas (o) flame ionization detector response and (b) sulfur chemiluminescence detector response. The organosulfur compounds are too dilute to be seen in flame ionization, and the sulfur chemiluminescence is insensitive to hydrocarbons. [From N. G. Johansen and J. W. Birks, Determination of Sulfur Compounds in Difficult Matrices." Am. Lob. February 1991.112.]...

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