Sulfur conversion

Maximize the recovery of sulfur by operating the furnaces to increase the SO, content of the flue gas and by providing efficient sulfur conversion. Use a double-contact, double-absorption process. 

Both XIV and XV are highly reactive and neither can be isolated from the reaction mixture in the absence of F,t2NH however, upon reaction with elemental sulfur, conversion to the phosphorus sulfide analogs (XVI and XVII) occurs. The latter are crystalline solids stable indefinitely at 25°C in the absence of Et2NH. 

The desulfurization process reported by the authors was a hybrid process, with a biooxidation step followed by a FCC step. The desulfurization apparently occurs in the second step. Thus, the process seems of no value, since it does not remove sulfur prior to the FCC step, but only oxidizes it to sulfoxides, sulfones, or sulfonic acids. The benefit of such an approach is not clearly outlined. The benefit of sulfur conversion can be realized only after its removal, and not via a partial oxidation. Most of the hydrotreatment is carried out prior to the FCC units, partially due to the detrimental effect that sulfur compounds exert on the cracking catalyst. It is widely accepted that the presence of sulfur, during the regeneration stage of the FCC units, causes catalyst deactivation associated with zeolite decay. In general terms, the subject matter of this document has apparent drawbacks. 

Sulfur Compounds Conversion of Sulfur, % Conversion of H202, % S04 mol % In aqueous Phase... 

After die reaction the two phase separated. Sulfur Conversion measure by GC from Organic Phase, Hydrogen Peroxide and Sulfate Concentration measured from aqueous phase. 

Ammonia. Ammonia interferes with existing acid gas removal processes because it can pass on through the scrubbers and then solidify on cyrogenic surfaces or it can go with the acid gases and poison the sulfur conversion catalysts. If ammonia is absorbed into an aqueous stream, then this aqueous stream must be... 

Figure 1. Variation of LOG and H2S yields as a function of sulfur conversion from Mequinenza lignite.

Later authors established the approximate composition of products formed in the reaction of acetylene with sulfur at different temperatures. At 325° the composition was found to be CSj 77%, thiophene 9%, thienothiophene 1 6% at 500°, CSj 77%, thiophene 12%, and thienothiophene 1 6% at 650° CS2 83%, thiophene 5%, and thienothiophene 1 3%, with sulfur conversion being 38%, 74%, and 77%, respectively. When studying this reaction at 290°-390°, Bhatt et isolated thiophenol in addition to the above compounds but failed to increase the yield of thienothiophene 1. 

Sievering, H., J. Boatman, J. Galloway, W. Keene, Y. Kim, M. Luria, and J. Ray, Heterogeneous Sulfur Conversion in Sea-Salt Aerosol Particles The Role of Aerosol Water Content and Size Distribution, Atmos. Environ., 25A, 1479-1487 (1991). 

Among the most effective of the modifications to Claus operating procedure is accurate temperature control of the catalyst beds. Gamson and Elkins (27) in the early 1950 s showed that equilibrium sulfur conversion efficiencies in the catalytic redox reaction rise dramatically as operating temperatures are lowered toward the dewpoint of sulfur. While some highly efficient subdewpoint Claus type processes are now in use the bulk of sulfur production from H2S still requires that the converters be operated above the dewpoint. Careful control of converter bed temperature has, however, contributed to improved efficiencies. This has in large part resulted from better instrumentation of the Claus train and effective information feed back systems. 

Various Keggin-type polyoxometalates (POMs) were tested as catalysts for the ODS of gas oil with t-butyl hydroperoxide. Alumina-supported phosphomolybdic acid (H3PMoi2O40) proved to be quite active, yielding sulfur conversion higher than... 

When sulfur conversion levels are pushed above 90%, the unique refractoriness of asphaltenes becomes dominant. The tendency of a fine pore catalyst to partially exclude asphaltenes and the complete steric hindrance or "burying" of sulfur in asphaltenes contribute to this refractoriness. 

Whereas the relative amount of aromatics remained fairly constant as sulfur conversion level was increased to 92-94%, the relative amount of sulfur in the aromatic fraction decreased markedly. This also is depicted in Figure 3. Polar aromatics are intermediate to the aromatics and asphaltenes in regard to this behavior. 

What we found is that all metal ions catalyze P—O fission. Selective P—O fission by amines was increased from 80% to 100% in the presence of Mg2+ ion, which also enhanced the rate. Exclusive P—O fission also occurred in the attack by the oxyanion of PCA in the presence of Zn2+ ion. A plausible rationale is that such a path, which involves metal ion assistance in a pentacovalent intermediate as illustrated in Figure 12a, is energetically much more favorable than that of Sn2 displacement on sulfur. Conversely, if an enzyme that catalyzes the reaction of phosphosulfate is metal ion dependent, the reaction probably involves P—O fission, as suggested by Roy (4). 

Equations (4-24) through (4-32) were solved on the computer by Shah et al.47 For a given set of conditions, a value of Q (as a function of quench position) at zero time was obtained. This Q was kept constant during the cycle life. As the reactor aged, the activity decline was counterbalanced by the increase in feed temperature so as to keep the sulfur conversion constant. The effects of various system parameters on the reactor cycle life obtained from these calculations are briefly described below. 

Higher sulfur conversion and feed sulfur concentration give a lower cycle life. For a typical set of conditions, these effects are illustrated in Figs. 4-10 and 4-11, respectively. 

FIGURE 9.1 I Schematic diagram of the converter section of a contact sulfuric acid plant employing an interpass absorption system for both better sulfur conversion and emission abatement. Product acid (or oleum) is cooled indirectly with process water prior to storage for sale. 

The U.S. Bureau of Mines has tested a pilot-scale sulfur dioxide to sulfur conversion process which involves initial absorption of sulfur dioxide in an aqueous solution of citric acid, H0C(CH2C02H)2C02H, and sodium citrate (Fig. 13.11). This solution is then contacted with hydrogen sulfide to reduce the sulfur dioxide to elemental sulfur, which is then readily filtered from the resulting slurry (Eqs. 13.41-13.43). 

It should be observed that mixtures which evolve sulfur as diatomic gas often show large spritzels with the blue flame typical of burning sulfur. Conversely, mixtures which tend to evolve sulfur as monoatomic gas often show no visible flame, but SO2 can be detected a few inches from the burning material as monoatomic sulfur combines with atmospheric oxygen. Burning the comps which produce monoatomic sulfur in quartz tubes with inert atmosphere, the sulfur will be recovered as the element. The barium nitrate formulation produces only BaS and is energetic enough to produce monoatomic sulfur. 

This indicated that total oxidation was predominant at the reactor inlet but then steam reforming consumed the water that had been produced. Heat losses of about 1.14kW were calculated for the reactor, which underlined the need for sufficient insulation, especially at temperatures exceeding 600 ° C. When the feed was switched from sulfur-free jet fuel to jet fuel containing 300 ppm sulfur, conversion dropped quickly and then deteriorated slowly with the time on stream. 

Therefore, 1 pound of sulfur can usually result in 2-3 pounds of medium-pressure steam. Sulfur conversion efficiency can vary significantly, depending on the specific operating conditions and technology. 

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