Desulfurization, chemical

The oxidation reaction is carried out by a simple contact between the feed and the biocatalyst, followed by separation prior to the aqueous chemical desulfurization reaction, which details can be seen in Ref. [78],... 

See reference (8) for chemical desulfurization studies on this coal. 

The full potential for removing pyritic sulfur from various coals by physical coal cleaning is significant but difficult to achieve. However, SO2 control by precombustion removal of pyrite could be an important S02-emissions reduction strategy. The cleaned coal produced could be used in coal-fired utilities, constructed both pre-and post-NSPS, as well as in industrial boilers. To realize the potential for coal cleaning in actual practice, however, new techniques must be demonstrated in the laboratory and then at the "proof-of-concept" scale (approximately one ton of coal per hour). These new coal beneficiation techniques could be advanced physical-coal-cleaning (PCC) processes, or they could employ microbial desulfurization or chemical desulfurization to remove organic sulfur. These latter processes could be used by themselves or in concert with PCC processes. 

The authors gratefully acknowledge Dr. T.D. Wheelock and Dr. C.-W. Fan at Iowa State University and Dr. Robert Meyers and Dr. Walter Hart at TRW Systems, Inc., for supplying samples of raw and chemically desulfurized coal on which our analyses were performed. Coals chemically cleaned at Ames Laboratory were provided by Mr. 

This decrease in the organic sulfur content of the Lovilia/ROM coal was corroborated by a series of extraction experiments employing ASTM procedures and other analyses for sulfur and iron. The removal of organic sulfur from the other two coals could not be confirmed by this method. However, the different extraction procedures pointed to possible changes in the mineral components and in the organic matrix itself of the coals after the chemical desulfurization treatment. Such changes can affect the analytical values obtained by ASTM procedures. 

Under the experimental conditions noted above sulfur dioxide is evolved, intermittantly, as a function of temperature and distinctive patterns of evolution arise when one compares a given coal before and after chemical desulfurization treatment or when one compares raw coals of different ranks. 

Chemical desulfurization techniques have a common drawback. They require pulverizing the coke to expose maximum surface area to the reactant(s). Thus, the end product is low sulfur coke with no... 

Desulfurization. Chemical desulfurization studies using H O /H SO, and have been carried out by Vasilakos et al. 

Another option for secondary smelters is to desulfurize the battery paste prior to smelting. Chemical desulfurization, however, is dependent on physical mixing conditions and temperature. Chemical desulfurization is achieved by adding a concentrated sodium carbonate solution to an agitated mix of battery paste sludge to convert the lead sulfates to lead carbonates. Complete conversion of lead sulfate to lead carbonate eliminates sulfur in the furnace feed material and sulfur dioxide in the exhaust gases. Complete desulfurization is, however, rarely achieved under normal industrial conditions. 

The Bureau of Mines together with the American Petroleum Institute made concentrated efforts to study both nitrogen and sulfur compounds in domestic crudes in the 1950-1964 period (2,3,4,5). The sulfur studies (API Report of Project 48), while limited to low-molecular-weight compounds, were the first comprehensive attempt to integrate liquid-solid and gas-liquid chromatography with selective chemical desulfurizations and mass spectrometry more than 100 individual sulfur compounds were... 

Chemical desulfurization has been investigated as a method to selectively remove inorganic sulfur (which con-... 

The emulsified oil-in-water conditioning allows for a large interfacial area of contact between the two fluids, which is a favorable situation for the biotreatment of heavy fractions for removal of sulfur or metals, or for a two-phase chemical desulfurization. 

As we have shown previously, obtaining both good cold operation characteristics and sufficient cetane numbers constitutes the principal objective for the refiner in the formulation of diesel fuel. To this is added the need for deep desulfurization and, perhaps in the future, limitations placed on the chemical nature of the components themselves, e.g., aromatics content. 

Other Uses. Other uses include intermediate chemical products. Overall, these uses account for 15—20% of sulfur consumption, largely in the form of sulfuric acid but also some elemental sulfur that is used directly, as in mbber vulcanization. Sulfur is also converted to sulfur trioxide and thiosulfate for use in improving the efficiency of electrostatic precipitators and limestone/lime wet flue-gas desulfurization systems at power stations (68). These miscellaneous uses, especially those involving sulfuric acid, are intimately associated with practically all elements of the industrial and chemical complexes worldwide. 

In the United States calcium carbide-based acetylene is mainly used in the oxyacetylene welding market although some continues to be used for production of such chemicals as vinyl ethers and acetylenic alcohols. Calcium carbide is used extensively as a desulfurizing reagent in steel and ductile iron production allowing steel mills to use high sulfur coke without the penalty of excessive sulfur in the resultant steel (see Sulfurremoval and recovery). Calcium cyanamide production continues in Canada and Europe (see Cyanamides). 

Approximately 50% of the demand for tetrachloroethylene is in the dry-cleaning industry where about 80% of all dry cleaners use it as their primary cleaning agent. Use as a feedstock for chlorofluorocarbon production accounts for 30% of current demand. Metal cleaning and miscellaneous appHcations represent 12 and 8% of demand, respectively. The miscellaneous appHcations include such varied uses as transformer insulating fluid, chemical maskant formulations, and as a process solvent for desulfurizing coal. 

E. P. Stambaugh in Coal Desulfurization, Chemical and Physical Methods, ACS Symposium Series 64, American Chemical Society, Washington, D.C., 1977, p. 198. 

Oxidative Desulfurization Process. Oxidative desulfurization of finely ground coal, originally developed by The Chemical Constmction Co. (27,28), is achieved by converting the sulfur to a water-soluble form with air oxidation at 150—220°C under 1.5—10.3 MPa (220—1500 psi) pressure. More than 95% of the pyritic sulfur and up to 40% of the organic sulfur can be removed by this process. 

Fig. 13. The MgO desulfurization system regeneration. Reproduced by permission of the American Institute of Chemical Engineers, 1984 (77).

Soud, et al., 1993. Hermine N. Soud, Ivlitsuru Takeshita, and Irene M. Smith, "FGC Systems and Installations for Coal-Fired Plants" from "Desulfurization 3," Institution of Chemical Engineers, Warwickshire, UK, 1993. 

All refining operations may be classed as either conversion processes or separation processes. In the former, the feed undergoes a chemical reaction such as cracking, polymerization, or desulfurization. Separation processes take advantage of differences in physical properties to split the feed into two or more different products. Distillation, the most common of all refinery separation processes, uses differences in boiling points to separate hydrocarbon mixtures. 

The Chemistry and Technology of Petroleum, James G. Speight The Desulfurization of Heavy Oils and Residua, James G. Speight Catalysis of Organic Reactions, edited by William R. Moser Acetylene-Based Chemicals from Coal and Other Natural Resources, Robert J. Tedeschi... 

The close structural resemblance between the sedative-hypnotic and anticonvulsant agents was mentioned earlier. It is interesting that the two activities can be related in at least one case by a simple chemical transformation. Thus, reductive desulfurization of the thiobarbituric acid, 158, affords primi-... 

The addition of the lithium enolates of various acetic add esters to (S)-3-(4-methylphcnyl-sulfmyl)-2(5//)-liiranone and (,S)-5,6-dihydro-3-(4-methylphenylsulfinyl)-2//-pyran-2-one gives, after desulfurization with Raney nickel, 4-substituted dihydro-2(3//)-furanoncs and 4-substituted tetrahydro-2//-pyran-2-ones, respectively, in good to quantitative enantiomeric excess. Addition of the enolate occurs via the nonchelate mode. The enolate of methyl (phenylthio)acetatc is best overall in regards to chemical yields and enantiomeric purity of the final lactone product13. 

The series of reactors and exchangers which methanates a raw syngas without pretreatment other than desulfurization is collectively termed bulk methanation. The chemical reactions which occur in bulk methana-tion, including both shift conversion and methanation, are moderated by the addition of steam which establishes the thermodynamic limits for these reactions and thereby controls operating temperatures. The flow sequence through bulk methanation is shown in Figure 1. 

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