Sulfur concentration profile

Figure 2. Electron-probe microanalyses of a deactivated catalyst semiquantitative vanadium and sulfur concentration profiles...

Figure 7.17a and b illustrate the dynamic profiles of sulfur concentration and temperature of industrial HDT reactor, which were determined from mass and energy balance equations. The results of the transient simulation of sulfur profiles of bench-scale reactor and experimental temperature are also shown for comparison. It can be observed that the steady state was reached at the same time (1700 s), which is due to the same space velocity and initial temperature used in both reactors. Because a single point at steady state is used to validate the dynamic model, some uncertainness remains regarding the shape of dynamic profiles of bench-scale and industrial reactors. According to Carberry and Varma (1987), the small peak in the sulfur concentration profile at the outlet of the commercial reactor is a typical response from HDT reactors that perform well with a weak bypass effect. 

The transient behavior of the sulfur concentration in the commercial HDT reactor is illustrated in Figure 7.18. It can be observed that there is a distinctive maximum in transient values, which is highest at the top of the reactor and progressively decreases down the reactor. These transient sulfur concentration profiles are important for online tuning of the controller settings in the control system of HDT processes. 

FIGURE 7.18 Dynamic sulfur concentration profiles in the liquid phase of commercial... 

FIGURE 9.5 Sulfur concentration profile in liquid bulk and catalyst surface at 400°C, 6.9 MPa, and LHSV = 1 h" , ( ) experimental value. 

FIGURE 9.8 Sulfur concentration profiles as function of inverse of LHSV at 6.9MPa (o) 380°C, ( ) 400°C, (A) 420°C. (Lines) Simulated, (Symbols) Experimental. 

FIGURE9.10 Sulfur concentration profiles in liquid phase as functions of reactor length at 420°C, LHSV of 0.33 h ", and 8.3 MPa. ( ) Experimental value. 

The refined source profiles that best reproduced the coarse fraction are listed in table 7. The calculated profiles of the two crustal components follow those of Mason ( ), though the calcium concentration of 20 in the limestone factor is less than the reported value. The paint pigment profile strongly resembles that calculated for the fine-fraction data. The only major difference is that unlike the fine fraction, the coarse-fraction profile does not associate barium with the paint-pigment factor. The calculated sulfur concentration in the coarse-fraction sulfate factor is much less than that in the fine-fraction and there are sizable concentrations of elements such as aluminum, iron, and lead not found in the fine-fraction profile. The origin of this factor is not clear although as described earlier a possible explanation is that a small part of the sulfate particles in the fine fraction ended up in the coarse samples. 

Concentration changes observed between mother liquor in the flash zone and liquid product in the melt zone of an experimental triple-point crystallizer have been dramatic. A qualitative concentration profile typical of those observed in the experimental unit is shown in Figure 8. The mother liquor concentration is relatively uniform above the packed bed, but a sharp drop in contaminant concentration occurs within the top several inches of the loosely packed crystal bed. Concentration changes of the order 500 to 5000 have been observed for representative sulfurous compounds and trace contaminants, including hydrogen sulfide, carbonyl sulfide, methyl mercaptan, ethane, and ethylene. Concentration profiles calculated for the packed bed of solid carbon dioxide using a conventional packed bed axial dispersion model agree very well with the observed experimental profiles. 

In the solar evaporation ponds, salinities in the cores reached almost four times oceanic values. In these cores the concentration profile of bimane sulfide with depth also tracked that of methylene blue sulfide and bimane total reduced sulfur tracked DTNB. However, the difference between the bimane method and the other two methods is unacceptably large and suggests that there was some inhibition of the bimane reaction. Pore water samples which were diluted to normal seawater salinity with 200 mM HEPES buffer pH 8 were not inhibited. Dilution will of course lead to a loss of sensitivity for trace thiols. Another factor which can effect the yield of the bimane reaction is the unusual... 

The energy separation of the thresholds allows a clear distinction between sulfide S11 (2470eV), sulfite SIV (2478eV) and sulfate SVI (2482eV). It is then possible to image profiles (Fig. 7b) of the different sulfur species across the inclusion (Fig. 7 a), even for very low sulfur concentrations. 

Auger electron spectroscopy (AES) is particularly suited for surface analysis (depth 0.5-1 nm). AES depth profile analysis was employed to determine the thickness and composition of surface reaction layers formed under test conditions in the Reichert wear apparatus in the presence of four different ZDDPs additives at different applied loads (Schumacher et al., 1980). Using elemental sensitivity factors the concentration of the four elements (S, P, O, C) was determined at three locations corresponding to a depth of 1.8, 4.3, and 17 nm. No significant correlation between wear behavior and carbon or oxygen content of the reaction layer was observed. A steady state sulfur concentration is reached after a very short friction path. Contrary to the behavior of sulfur, phosphorus concentration in the presence of ZDDPs increases steadily with friction path, and no plateau value is reached. 

The electrolytic conductivity detector is a good alternative to the FPD for selective sulfur detection. The ELCD has a larger linear dynamic range and a linear response to concentration profile. The ELCD in most cases appears, under ideal conditions, to yield slightly lower detection limits for sulfur (about 1-2 pg S/sec), but with much less interference from hydrocar-... 

Concentration Profiles. The relative fluorescence intensity profiles for OH, S2, SH, SO, and SO2 were converted to absolute number densities according to the method already outlined. Resulting concentration profiles for a rich, sulfur bearing flame are exhibited in Figure 17. H-atom densities were calculated from the measured OH concentrations and H2 and H2O equilibrium values for each flame according to Equation 6. Similar balanced radical reactions were used to calculate H2S and S concentrations 6). Although sulfur was added as H2S to this hydrogen rich flame, the dominant sulfur product at early times in the post flame gas is S02 ... 

In that earlier study an examination of the available sulfur chemical kinetics lead to the identification of the following 8 fast coupled radical reactions that could account for the measured concentration profiles. 

Figures 28 and 29 show the transient methanation activity of a Ni/Al203 flat-plate catalyst and the gas-phase H2S concentration profile, respectively. The presence of just 13-ppb H2S caused about a 200-fold loss in steady-state methanation activity. Increasing the H2S level to 62 ppb resulted in an additional tenfold activity loss an increase to 95 ppb lowered the activity further. However, increasing the H2S level above 95 ppm did not cause a significant additional decrease in activity (Fig. 30) and decreasing the H2S level from 95 to about 15 ppb reversibly restored the activity level originally observed at this latter concentration level, thereby demonstrating that sulfur adsorption and poisoning by sulfur are reversible, and that a truly dynamic...

Fig. 35. Sulfur coverage of the nickel surface of a reforming catalyst in a typical naphtha-based ammonia plant as a function of distance through the reactor and inlet sulfur concentration (ppm) (Ref. 237b). Assumed profiles of temperature and hydrogen flows ...

The work of Rostrup-Nielsen is very informative, but it also raises a number of important questions. How can more realistic temperature and concentration profiles through the reactor be incorporated into a reactor deactivation model Could experimental measurements be performed to determine how sulfur is actually distributed in the catalyst pellets and in the bed and how this distribution changes as a function of time at various H2S concentrations Would it be worthwhile to consider a modification of the model by Wise and co-workers (195,233) for steam reforming in which pore... 

Leung, Colussi and Hoffmann have used isotopic analysis in an attempt to constrain the amount of sulfate that could be produced by Crutzen s mechanism [129,130]. The first study retrieved the concentration profiles of OC S and OC S from infrared transmission spectra of the atmosphere recorded by the NASA MkIV balloon-borne interferometer. They derived an enrichment factor of 73.8 zb 8.67oo defined such that photolytically generated sulfur would be enriched in An isotopic budget based on this result shows that OCS photolysis cannot be a significant source of sulfate aerosol, since the enrichments of OCS, sulfuric acid aerosol and SO2 are known to be small [131]. A later laboratory study by the same group came to the conclusion that stratospheric photolysis results in an enrichment of 67 zb 77oo. 

Single Pellet One Reaction. The sulfation reaction which is considered here for calcium carbonate is given by Eq. 3, and the temperature and concentration profiles of a typical growing limestone particle are shown in Figure 2. The rate of disappearance of sulfur dioxide is assumed to be the first order and is given by... 

The development of mathematical models to describe the thermochemical process occurring in a fluidized bed involves setting up the material and energy balance equations. The total process is represented in terms of a set of independent equations which are solved simultaneously to obtain such quantities as combustion efficiency, sulfur retention, oxygen utilization, oxygen and sulfur dioxide concentration profiles in the bed, etc. 

The solution of Eq. 87 with Eq. 88 will establish the sulfur dioxide concentration profile along the fluidized bed combustor. 

The concentration profile of oxygen in the bed is fixed by establishing apriori a value for b as 4.5 and that of a as obtained from the assumed values of carbon conversion and sulfur absorption efficiencies. For a given oxygen profile the reaction rate constant, k3(To), and the size of the dolomite feed are varied. The changes in both of these parameters affect the value... 

Figure 10. Concentration profiles of oxygen, wAi and sulfur dioxide, wbh, in the bed corresponding to rfccs = 0.995, rjsAE = 0.99,Y=Y = 0.04 cm and =...

This paper proposes a system of 10 non-linear, simultaneous differential equations (Table I) tdiich upon further development and validation, may serve as a comprehensive model for predicting steady state, vertical profiles of chemical parameters in the sulfide dominated zones of marine sediments. The major objective of the model is to predict the vertical concentration profiles of H2S, hydrotriolite (FeS) and p3nrite (FeS2). As with any model there are a number of assumptions involved in its construction that may limit its application. In addition to steady state, the major limiting assumptions of this model are the assumptions that the sediment is free of CaC03, that the diffusion coefficients of all dissolved sulfur species are equivalent and that dissolved oxygen does not penetrate into the zone of sulfate reduction. 

Because the PPR is operated as an adiabatic reactor, the strongly exothermic oxidation reaction (iii) causes a temperature wave traveling through the bed, giving rise to a peak outlet temperature in the initial period of the acceptance cycle, as. shown in Fig. 26. In this figure, the temperature profile predicted by a mathematical model developed at the Shell laboratory in Amsterdam is compared with the profile measured in an industrial reactor to be described later. During the initial oxidation period, the copper is not yet active for reaction with sulfur oxides, so there is a slip of sulfur in the initial period, as can be seen in Fig. 27. It can be inferred that the sulfur dioxide concentration profile of the effluent of the industrial reactor is in close agreement with the profile predicted on the basis of a kinetic model developed at the Shell laboratory in Amsterdam. 

We denote by Vr the volume of regenerant effluent recycled from one cation exchange cycle, and by Vea the volume of acid necessary for regeneration if it were used at the same concentration as in the production of ammonium nitrate or ammonium sulfate (55% for nitric acid and 98% for sulfuric acid). The acid is actually diluted twice, firstly when the regenerant solution is prepared and secondly in the resin bed by longitudinal diffusion wbich broadens the concentration profile at the front and tail. 

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