Sulfur loading

Although the separation between some unwanted co-extractants and the analytes is well suited to an on-line system, high lipid or elemental sulfur loading is more effectively removed off-line. Most on-line systems at present work most effectively with low lipid contents [493,494], although some applications have overcome the problem of lipid removal. 

Deposition of reduced sulfur compounds to enclosed surfaces could also be measured by adding low loss (5 ng/min, GC Industries) permeation tubes to the inlet of the chambers. This permeation rate adds an additional sulfur load which varied typically between 2 and S times that already within the enclosure. These studies were limited to surfaces where large temporal changes in natural emissions were not occurring, and ultimately became limited by the reliability of the permeation devices. 

Most of the emissions data available in the literature was obtained within alterniflora marshes, and hence reflect the complexity of this ecosystem. Our data set extends the available emissions data to less complex systems, and at the same time lowers our estimation of the biogenic contribution to atmospheric sulfur loading. Even our highest estimate of biogenic emissions, that of... 

The experiments were carried out at ambient pressure. All hydrocarbons were tested at a S/C ratio of three and all alcohols at a corresponding oxygen to carbon ratio. Decreasing conversion was found for the various fuels with increasing feed rates except for methanol owing to the very high reaction temperature of 725 °C. Table 2.9 summarizes some of the results presented for the various fuels. The proprietary catalyst showed only minor deactivation after 70 h TOS. It was deactivated reversibly by sulfur. Load changes of the liquid input from 100 to 10% resulted in a system response after 5-10 s. 

Weigh to obtain sulfur loading test control specimens. 

Figure 4. Relation between sulfur loading and compressive strength of sulfur-infiltrated concrete. Wide scattering at higher loadings suggests variable porosity and/or inconsistent filling.

The catalytic activity of these materials depends upon the sulfur content. When the sulfur loading in the catalyst increases, structures with S-O-S bonds similar to those in pyrosulfuric or higher polysulfuric acids may exist on the surface of the catalysts. 

Costa F., Scaillet B., Gourgaud A. (2003). Massive atmospheric sulfur loading of the AD 1600 Huaynaputina eruption and implications for petrologicl sulfur estimates. Geophys. Res. Lett. 30(2), 10.102912002GL016402. 

Goud et al.141 studied the kinetics of deactivation of Pd/Zr02 catalyst in the steam reforming of n-hexadecane. A first-order kinetic model, with first-order deactivation rate, was used to obtain the best fit values for the reaction rate constant and the deactivation rate constant as a function of S/C ratio, temperature, and sulfur loading. They noticed that the reaction rate was enhanced by an increase in temperatures and S/C ratios, but decreased by the presence of sulfur. The catalyst deactivation was more rapid in the presence of sulfur, at low S/C ratios and at lower temperatures. 

ZnO has been widely used for more than 30 years as an H2S removal agent from natural gas.176 The achieved dynamic capacity was 22-24 wt% (370 °C, 400 h 1), with a maximum possible sulfur loading of 33 wt%, which corresponds to the complete conversion of ZnO to ZnS. If the concentration of sulfur in the feed gas is very small, then on-site regeneration is not necessary for some applications. For such cases, upon breakthrough, the absorbent bed is replaced with a fresh batch of ZnO and then sulfur removal continues. From this point of view, the use of ZnO as a... 

Fig. 4. S EM images of the sulfur loaded composite catalyst (sulfur loading of 150 wt.%).

We have to emphasize here that the majority of the sulfate-sulfur in the tropospheric reservoir in not sea salt. Friend (1973) estimated that the atmospheric sea-salt burden is around 0.1 x 106 t. By subtracting this value from the sulfate-sulfur loading given in Fig. 19 and considering only the strength of chemical sources (62 x 106 t yr 1), a residence time of more than 4 days is obtained for the excess sulfate. 

Some sulfur dioxide concentrating systems can be designed to accept gases with fluctuating volumes and sulfur loadings. The sulfur dioxide is either physically or chemically bound in a solid or liquid medium in... 

A zonation of sulfur load areas is further possible on the base of the sulfur content in spruce needles. The contents of total sulfur in the needles of spruce should not exceed the following limits <0.11% S in dry matter for 1-year-old 0.14% S for 2-year-old and 0.17% S for 3-year-old needles. In the case of beech, the limit in the leaves is 0.08% S. 

Anthropogenic air pollution is an important source of acidity in ecosystems without carbonates in the soil (Legge and Krupa 1990). The sum of nitrogen and sulfur loads contributes to the critical acidity load. The acidity is linked with the cycles of base cations and phosphorus. 

According to the Eq. (32), the rate of conversion of H2S is influenced by the partial pressures of H2S, H2O, SO2, O2, the mass of the sulfur loaded on the catalyst and the reaction temperature. This equation can be used in designing a commercial fixed-bed reactor for one stage oxidation of hydrogen sulfide. 

Fig. 7.18 (A) H2S conversion and the corresponding solid sulfur deposit on the surface of the NiS2/SiC-grains (open symbols) and NiS2/SiC-nanotubes (filled symbols) catalysts as a function of time on stream at 60°C. The sulfur selectivity at 60°C was the total on the two catalysts. (B) SEM micrographs of the SiC nanotubes supported NiS2 catalyst after more than lOOh of reaction with a solid sulfur loading of200wt.%.

Both sulfate and sulfide have been detected by XPS on sulfided Pt/Al203 and platinum black sulfide ions selectively eliminated aromatisation and hydrogenolysis of n-hexane, while sulfate ions stopped all processes except dehydrogenation. At high sulfur loadings, where both forms were present, activity was reduced by 95%. 

The equipment of an all-out purification unit is certainly less complex than that of the selective type. However, since the combined removal of the sulfur components and the entire CO2 would leave the acid gas with so low a sulfur load that sulfur recovery in a Claus unit would not be possible any more, this arrangement requires a considerable effort to desulfurize the offgases sufficiently to conform to environ mental legislation and to make sulfur recovery cost-effective. 

ZnS is generated at the adsorbent surface as a new chemical species. Therefore, Eq. (34.2) must be attributed to chemisorption, which is a sub-class of adsorption. The maximum possible sulfur loading is 33%, which corresponds to the complete conversion of ZnO to ZnS. If the amount of sulfur in the feed gas concentration is small enough, on-site regeneration can be dispensed with. After breakthrough, the absorbent bed must be replaced by a fresh one. In such a concept, ZnO is used as a poHshing bed. 

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