Sulfur products

The concentrated hydrogen sulfide gas is then sent to the sulfur production unit (Claus process). 

The process options reflect the broad range of compositions and gas volumes that must be processed. Both batch processes and continuous processes are used. Batch processes are used when the daily production of sulfur is small and of the order of 10 kg. When the daily sulfur production is higher, of the order of 45 kg, continuous processes are usually more economical. Using batch processes, regeneration of the absorbant or adsorbant is carried out in the primary reactor. Using continuous processes, absorption of the acid gases occurs in one vessel and acid gas recovery and solvent regeneration occur in a separate reactor. 

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). 

Sulfonation Plant Operations and Gas Effluent. Standards governing U.S. sulfonation plant gas effluents differ depending on whether or not the plant is equipped with a H2SO4 scmbbing system for adsorption of SO gas (see Fig. 3). The installation of the SO adsorber system qualifies the plant as a sulfuric production plant which has stringent regulations. Limitations and typical effluent from the sulfonation system are as follows ... 

Sources of sulfur are called voluntary if sulfur is considered to be the principal, and often the only, product. Sulfur has also been recovered as a by-product from various process operations. Such sulfur is termed involuntary sulfur and accounts for the largest portion of world sulfur production (see Sulfur REMOVAL AND RECOVERY). 

Pyrite is the most abundant of the metal sulfides. Eor many years, until the Erasch process was developed, pyrite was the main source of sulfur and, for much of the first half of the twentieth century, comprised over 50% of world sulfur production. Pyrite reserves are distributed throughout the world and known deposits have been mined in about 30 countries. Possibly the largest pyrite reserves in the world are located in southern Spain, Portugal, and the CIS. Large deposits are also in Canada, Cypms, Einland, Italy, Japan, Norway, South Africa, Sweden, Turkey, the United States, and Yugoslavia. However, the three main regional producers of pyrites continue to be Western Europe Eastern Europe, including the CIS and China. 

Table 2 shows the estimated aimual world sulfur production capacity in all forms. Figure 2 shows actual annual world sulfur production by type. 

Fig. 2. World sulfur production by type, where ( ) represents brimstone (Ml), SOF (B), pyrites and ( ), total sulfur (33).

Sulfur consumption reached peak levels by the beginning of the 1990s. The apparent annual consumption of sulfur in all forms in the United States nearly reached 13.2 million metric tons by 1995. World sulfur production increased steadily from 53.6 million metric tons in 1984 to an all-time high of 60.1 million metric tons in 1989, declining to 54.6 million metric tons in 1995. 

Increased environmental awareness contiaues to create new challenges as well as a variety of new market opportunities for sulfur producers. Further pollution reduction requirements contiaue to iacrease gradually aoadiscretioaary suppHes of sulfur and sulfur products. At the same time, recycling and reengineering have caused slight decreases ia demand. These trends are likely to contiaue ia the future. 

The physical properties of elemental sulfur can be modified by its reaction with various organic and inorganic compounds. Many of the resulting sulfur products tend to have properties similar to paving asphalt (49,50). 

J. B. Hyne, Recent Developments in Sulfur Production from Hydrogen Sulfide Containing Gases, paper presented at 181st National Meeting, ACS, Adanta, Ga., Mat. 29-Apt. 3,1981. 

Sulfur Products Handbook on Sulfur Monochloride and Sulfur Chloride, Bulletin SPE-SUL-HB 10/9, Oxychem Basic Chemicals Group, Occidental Chemical Corp., Dallas, Tex., 1993, p. 3. 

Sulfur can be produced direcdy via Frasch mining or conventional mining methods, or it can be recovered as a by-product from sulfur removal and recovery processes. Production of recovered sulfur has become more significant as increasingly sour feedstocks are utilized and environmental regulations concerning emissions and waste streams have continued to tighten worldwide. Whereas recovered sulfur represented only 5% of the total sulfur production ia 1950, as of 1996 recovered sulfur represented approximately two-thirds of total sulfur production (1). Recovered sulfur could completely replace native sulfur production ia the twenty-first century (2). 

The reaction involves two electrons per thionyl chloride [7719-09-7] molecule (40). Also, one of the products, SO2, is a Hquid under the internal pressure of the cell, facihtating a more complete use of the reactant. Finally, no cosolvent is required for the solution, because thionyl chloride is a Hquid having only a modest vapor pressure at room temperature. The electrolyte salt most commonly used is lithium aluminum chloride [14024-11-4] LiAlCl. Initially, the sulfur product is also soluble in the electrolyte, but as the composition changes to a higher SO2 concentration and sulfur [7704-34-9] huA.ds up, a saturation point is reached and the sulfur precipitates. 

In a modem carbon disulfide plant, all operations are continuous and under automatic control. On-stream times in excess of 90% are obtainable. The process is in three steps melting and purification of sulfur production and purification of carbon disulfide and recovery of sulfur from by-product hydrogen sulfide. A typical process appears in the flow diagram of Figure 1 (50). 

Gas treating is defined here as removal of H2S and CO2. Other sulfur compounds are discussed where applicable. Dehydration and sulfur production are not included, except for discussing sulfur production in the Stretford Process and for selective H2S removal. H2S must be removed from natural gas and process streams for health reasons and prevention of corrosion. Natural gas pipeline specifications require no more than % grain/100 SCF. This is equivalent to 4ppmv or 7ppmw (for a 0.65 specific gravity gas). By comparison, the human nose can detect... 

Virgin naphtha hydrofining processing conditions have been standardized at 550°F, 4 V/hr/V, 300-400 psig and 400-500 SCF/B of 70% H treat gas. Such conditions will make a 4 ppm sulfur product of most stocks of interest. 

Cokers produce no liquid residue but yield up to 30% coke. Much of the low-sulfur product is used for electrolytic electrodes for smelting of aluminum. Lower-quality coke is burned as fuel im.xcd with coal. 

Multiple reactors achieve 95-96% conversion and recovery, and stringent air pollution legislation has now pushed this to 99%. A similar sequence of reactions is used for sulfur production from crude oil except that the organosulfur compounds must first be removed from the refinery feed and converted to H2S by a hydrogenation process before the sulfur can be recovered. 

All gaseous sulfur products obtained as a result of incubation of sulfur-treated fruit were oxidized with alkaline hydrogen peroxide, precipitated as barium sulfate, and counted with a thin window Geiger counter. The peel and peel proteins were oxidized with magnesium nitrate, the sulfur was precipitated as barium sulfate according to standard methods, and counted as in the case of the gaseous products. Counting data, as reported, are fully corrected. 

Sulfur products Multiple products Powdery mildew, certain spot, scale, certain rust Various fruits and vegetables Fungicide... 

CBA [Cold bed adsorption] A variation of the Claus process in which the sulfur product is desorbed from the catalyst by a side stream of hot gas from the main process. Developed by AMOCO Canada Petroleum Company and operated in Alberta. 

LO-CAT A process for removing hydrogen sulfide and organic sulfur compounds from petroleum fractions by air oxidation in a cyclic catalytic process similar to the Stretford process. The aqueous solution contains iron, two proprietary chelating agents, a biocide, and a surfactant the formulation is known as ARI-310. The sulfur product is removed as a slurry. Developed in 1972 by Air Resources (now ARI Technologies) and first commercialized in 1976. Over 125 units were operating in 1996. An improved version, LO-CAT II, was announced in 1991. 

MERICAT A process for removing mercaptans from petroleum fractions by a combination of catalytic oxidation and extraction with aqueous sodium hydroxide, using a proprietary contactor based on a bundle of hollow fibers. The sulfur products are disulfides, which remain in the hydrocarbon product. Developed by the Merichem Company, Houston, TX, and used in 61 plants as of 1991. Mericat II is a variation which includes a carbon bed too there were four installations as of 1991. See also Thiolex. 

Independent conversion processes may not employ the Claus reaction for sulfur production and do not recycle the captured sulfur compounds to the Claus plant. Examples are the Beavon Mark I Process (Hydrogenation + Stretford) (13), the Beavon Mark II Process (Hydrogenation + Claus) (13), and the SNPA/Haldor-Topsoe Process (Catalytic Oxidation to SOi.) (9,10). 

The solid sulfur product need not be chosen as an unknown. Near room temperature, only a small percentage of it is oxidized to soluble sulfur-containing anions(4). It can be assumed, therefore, that none of the sulfur atoms originally present in the solid chalcopyrite enter the solution. The sulfur product is not recovered in the leaching process and does not affect the solution chemistry. 

Under fuel-rich combustion conditions, in addition to sulfur dioxide, the stable sulfur products are found to be hydrogen sulfide, carbonyl sulfide, and elemental sulfur. 

Stronger oxidizing agents such as hydrogen peroxide or ozone readily oxidize H2S forming sulfur and various other sulfur products. For example, HaOa reacts with HaS under neutral conditions forming sulfur and water ... 

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