Sulfur continued refinery

Recovered sulfur proved to be the downfall of the Mexican Frasch industry as well. In August 1992, APSA declared bankruptcy. The debt of the company was 220 million. APSA closed its three mines in November 1992, and CEDI closed its mine in May 1993. Total sulfur production from the Frasch industry in Mexico was 55 million tonnes (see Table 4.8, and Figure 4.13). The assets of APSA and control of Mexican sulfur exports were assigned to Pemex (becoming their Texistepec Mining Unit) by the Mexican government in lieu of prior sulfur sales owing. Sulfur continued to be produced from their oil refineries at Salina Cruz and Tula. Pemex operates nine sulfiir recovery units, and produces over one million tonnes of recovered sulfur per year. 

Sodium and potassium are restricted because they react with sulfur at elevated temperatures to corrode metals by hot corrosion or sulfurization. The hot-corrision mechanism is not fully understood however, it can be discussed in general terms. It is believed that the deposition of alkali sulfates (Na2S04) on the blade reduces the protective oxide layer. Corrosion results from the continual forming and removing of the oxide layer. Also, oxidation of the blades occurs when liquid vanadium is deposited on the blade. Fortunately, lead is not encountered very often. Its presence is primarily from contamination by leaded fuel or as a result of some refinery practice. Presently, there is no fuel treatment to counteract the presence of lead. 

Thiophenes continue to play a major role in commercial applications as well as basic research. In addition to its aromatic properties that make it a useful replacement for benzene in small molecule syntheses, thiophene is a key element in superconductors, photochemical switches and polymers. The presence of sulfur-containing components (especially thiophene and benzothiophene) in crude petroleum requires development of new catalysts to promote their removal (hydrodesulfurization, HDS) at refineries. Interspersed with these commercial applications, basic research on thiophene has continued to study its role in electrocyclic reactions, newer routes for its formation and substitution and new derivatives of therapeutic potential. New reports of selenophenes and tellurophenes continue to be modest in number. 

Assuming that demand for petroleum continues to increase at a rate of 1.2% per annum to 2010,37 and that all gasoline and diesel produced by U.S. refineries will have a sulfur content of less than 30 ppm, desulfurization of gasoline and diesel to these low levels will require extensive hydrotreating of both catalytic cracker feed and product of distillate. 

Swain, E. Coke, Sulfur Recovery from U.S. Refineries Continues to Increase. Oil Gas Journal, January 2, 1995. 

In 1979 sulfur obtained as a by-product from petroleum refining accounted for 19.7 percent of total sulfur produced in the U.S. The requirement to desulfurize residual fuels or alternatively to refine them to finished transportation fuels will result in a substantial increase in sulfur produced at refineries even if medium sweet crudes continue to be the primary refinery feedstock. However, most experts predict that crudes will become sourer in the future. The contribution from natural gas is an additional uncertainty. Conventional wisdom predicts that natural gas demand will maintain current levels or possibly decline over the next 20 years. The combination of these factors may increase conventional by-product sulfur from petroleum and natural gas by a factor of three or more by the year 2000. This would bring its sulfur contribution up to approximately 12 million tons by 2000, the same as that predicted by the MITRE estimate for synthetic fuels sulfur production. Thus, a possible total contribution of 60 percent of projected sulfur demand could be met by the combination of these by-product sources of sulfur. 

Tomorrow s fuels will contain less sulfur to be compatible with the more sophisticated engine designs of new automobiles. Fuels specifications will further reduce the concentrations of gasoline compounds that are listed and/or considered to be toxic. Refiners will continue to upgrade heavier components to lighter products and refineries will continue to use innovative catalysts and processing equipment to cost-effectively manufacture fuels and petrochemical feedstocks. We have barely touched on the sophisticated engineering needed to transform a barrel of crude oil into consumable products. 

Crude oil supplied to the refineries will not change significantly in quality the next five years because of the wide availability of sweet crudes. The product slate will continue to shift from fuel oil to transportation fuels (outside the USA). Distillate and jet will be the products with the strongest growth [36]. All oil products will face tighter specifications in particular sulfur levels will be decreased. 

The refinery blend contained a variety of light olefins, and contaminants (e.g., butadiene, oxygenates, sulfur) which are known to produce significant catalyst deactivation. These experiments were performed in a continuous, automated reaction/regeneration system... 

Elemental analysis of petroleum shows that the major constituents are carbon and hydrogen with smaller amounts of sulfur (0.1-8% w/w), nitrogen (0.1-1.0% w/w), and oxygen (0.1-3% w/w), and trace elements such as vanadium, nickel, iron, and copper present at the part per milHon (ppm) level. Of the non-hydrocarbon (heteroelements) elements, sulfur is the most abundant and often considered the most important by refiners. However, nitrogen and the trace metals also have deleterious effects on refinery catalysts and should not be discounted because of relative abundance. Process units with, for example, a capacity of 50,000 bbl/day that are in operation continuously can soon reflect the presence of the trace elements. The effect of oxygen, which also has an effect on refining catalysts, has received somewhat less study than the other heteroelements but remains equally important in refining. 

Use of on-stream XRE analysis for monitoring liquid process streams has been reported for a number of applications including measurement of Fe, Cu, Co, Ni and Mo from five different points in a solution purification process of a cobalt refinery [28] analysis of Cu, As and S in copper electrolyte purification solutions [29] control of a solvent extraction process for La and Nd [30, 31] continuous monitoring of catalyst elements (Mn, Co and Br) in terephthalic acid process solutions [32] and measurement of various elements (particularly sulfur) in petroleum product and refinery streams [33, 34]. 

Bullion was tapped continuously via a siphon from the centre of the furnace and slag was tapped intermittently from one end. Lead bullion contained around three per cent S, which was transferred to either of two small batch operated Pierce Smith converters, blown with air to remove sulfur. Slag from the converters and dusts collected from converter gases were also returned to the electric furnace. A copper matte was periodically recovered from the converters and the bullion was sent to the lead refinery. 

In a refinery, the sulfide fraction is a degree of freedom for optimization, since final products are made by mixing intermediate products. The value of an intermediate product is therefore a continuous function of the sulfur contents, in other words there is no unique quality requirement. 

Hydrogen fluoride (HF) has many industrial uses. In the process industries, it is used in many refineries as an alkylation catalyst (the alternative is sulfuric acid). The HF arrives either by tank car or truck. It is loaded into a storage tank, from where it is fed on a continuous basis. 

Delayed coking. Semi-continuous thermal cracking process used in petroleum refineries to upgrade and convert bottoms from atmospheric and vacuum distillation of crude oil into liquid and gas product streams, leaving behind a solid concentrated carbon material, petroleum coke, whose value will depend on its properties such as sulfur, metals, etc. The products of a delayed coker are wet gas, naphtha, light and heavy gas oils, and coke. The coke produced in the delayed coker is almost pure carbon and is utilized as fuel or, depending upon its quality, in the manufacture of anodes and electrodes (Hamilton, 2002 Elliott, 2003 Haniford, 2003 Elliott and Wedlake, 2007). 

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