Treating processes desulfurization

Kvaerner John Brown developed the Super Treat process addressing the H2S inhibition on HDS and favoring the desulfurization on refractory compounds [92], To begin with, they realized that more than 90% of the total produced H2S takes place in the first reaction stage, from the HDS of the most reactive S-compounds. Kvaerner technology... 

The high solubility of aromatic compounds in ionic liquids can also be used for the removal of the different dibenzothiophenes using liquid-liquid extraction. These are the compounds that are usually difficult to convert by hydro-treating in desulfurization processes. 

Grindley, T., and Steinfeld, G., 1985, Desulfurization of Hot Coal Gas by Zinc Ferrite, in Acid and Sour Gas Treating Processes, Gulf Publishing Co., Houston, TX, p. 419. 

There are three major ways of attaining sweetening (1) processes that oxidize mercaptans to disulfides, (2) processes that remove the mercaptans, and (3) processes that destroy and remove other sulfur compounds along with mercaptans, hydrogen sulfide, and sulfur. The last of these methods is usually considered as a desulfurization process. Walker and Kenney present a comprehensive discussion of the various treating processes. ... 

Flotation or froth flotation is a physicochemical property-based separation process. It is widely utilised in the area of mineral processing also known as ore dressing and mineral beneftciation for mineral concentration. In addition to the mining and metallurgical industries, flotation also finds appHcations in sewage treatment, water purification, bitumen recovery from tar sands, and coal desulfurization. Nearly one biUion tons of ore are treated by this process aimuaHy in the world. Phosphate rock, precious metals, lead, zinc, copper, molybdenum, and tin-containing ores as well as coal are treated routinely by this process some flotation plants treat 200,000 tons of ore per day (see Mineral recovery and processing). Various aspects of flotation theory and practice have been treated in books and reviews (1 9). 

Sulfur Compounds. Various gas streams are treated by molecular sieves to remove sulfur contaminants. In the desulfurization of wellhead natural gas, the unit is designed to remove sulfur compounds selectively, but not carbon dioxide, which would occur in Hquid scmbbing processes. Molecular sieve treatment offers advantages over Hquid scmbbing processes in reduced equipment size because the acid gas load is smaller in production economics because there is no gas shrinkage (leaving CO2 in the residue gas) and in the fact that the gas is also fliUy dehydrated, alleviating the need for downstream dehydration. 

Naphthalene sodium prepared in dimethyl ether or another appropriate solvent, or metallic sodium dissolved in Hquid ammonia or dimethyl sulfoxide, is used to treat polyfluorocarbon and other resins to promote adhesion (138—140). Sodium, usually in dispersed form, is used to desulfurize a variety of hydrocarbon stocks (141). The process is most useful for removal of small amounts of sulfur remaining after hydrodesulfurization. 

Owing to the reversible nature of the allylic sulfenate/allylic sulfoxide interconversion, the stereochemical outcome of both processes is treated below in an integrated manner. However, before beginning the discussion of this subject it is important to point out that although the allylic sulfoxide-sulfenate rearrangement is reversible, and although the sulfenate ester is usually in low equilibrium concentration with the isomeric sulfoxide, desulfurization of the sulfenate by thiophilic interception using various nucleophiles, such as thiophenoxide or secondary amines, removes it from equilibrium, and provides a useful route to allylic alcohols (equation 11). 

Newer secondary recovery plants use lead paste desulfurization to reduce sulfur dioxide emissions and waste sludge generation during smelting. Battery paste containing lead sulfate and lead oxide is desulfurized with soda ash to produce market-grade sodium sulfate solution. The desulfurized paste is processed in a reverberatory furnace. The lead carbonate product may then be treated in a short rotary furnace. The battery grids and posts are processed separately in a rotary smelter. 

At the beginning of the 1990s, Houston Industries developed an enzymatic process ( Enzymatic Coal Desulfurization ) protected in Canada and US [83,84], Although, the application was focused to coal desulfurization it may also be applicable to crude oil and fossil fuel-derived liquids. The processes claim the removal of both, organic as well as inorganic sulfur species. The process was described as using ground coal (10-50 p,m) slurried with water, while the oil was treated in an aqueous emulsion. 

Dual Alkali A flue-gas desulfurization process. The sulfur dioxide is absorbed in aqueous sodium hydroxide and partially oxidized, and this liquor is then treated with calcium hydroxide to regenerate the scrubbing solution and precipitate calcium sulfate. Developed by Combustion Equipment Associates and Arthur D. Little. 

Molten Carbonate A flue-gas desulfurization process in which the sulfur dioxide contacts a molten mixture of inorganic carbonates. These are converted to sulfates and sulfides and then reduced to hydrogen sulfide, which is treated in a Claus kiln. The advantage of this process over most others is that it does not cool the flue-gases. Not commercialized. Oldenkamp, R. D. and Margolin, E. D., Chem. Eng. Prog, 1969, 65(11), 73. 

NEUTREC A flue-gas desulfurization process, intended for treating the waste gases from incinerators for municipal, hospital, and industrial wastes. Sodium bicarbonate, optionally mixed with active carbon, is injected into the gases after the usual bag filter, and the solid products are removed in a second bag filter. Sodium compounds can be recovered from the product for reuse, and ary toxic compounds disposed of separately. Developed by Solvay and operated in Europe since 1991. 

A variety of unimolecular processes involving loss of small molecules are shown below. Thiazine 1,1-dioxide 170 loses sulfur dioxide when heated (Equation 1) <19728311>, whereas thiazines with the general structure 179 undergo desulfurization to give pyrroles when treated with triethylamine (Equation 2) <1984JOC4780, 1985JHC1621>. 

If new investment is considered, then there are many new approaches to reducing the sulfur level in gas oils and diesel fuels by means of sequentially staged operations. The first stage can be a mild-severity selective process to modify the feed so as to make desulfurization more facile, or it may be a severe process to lower the sulfur level but produce a product that must be further treated to meet some other specification. 

The high-boiling distillates, such as the atmospheric and vacuum gas oils, are not usually produced as a refinery product but merely serve as feedstocks to other processes for conversion to lower-boiling materials. For example, gas oils can be desulfurized to remove more than 80% of the sulfur originally in the gas oil with some conversion of the gas oil to lower-boiling materials (Table 6-11). The treated gas oil (which has a reduced carbon residue as well as lower sulfur and nitrogen contents relative to the untreated material) can then be converted to lower-boiling products in, say, a catalytic cracker where an improved catalyst life and volumetric yield may be noted. 

Sulfur removal, as practiced in various refineries, can take several forms for instance, concentration in refinery products such as coke (Table 7-1), hydrode-sulfurization, or chemical removal (acid treating and caustic treating, i.e., sweetening or finishing processes). Nevertheless, the desulfurization of petroleum is almost universally accomplished by the catalytic reaction of hydrogen with the sulfur-containing constituents of petroleum to produce hydrogen sulfide that can be readily separated from the liquid products (Chapter 9). 

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