Sulfur concentrating systems

Using a batch reactor, a constant concentration of sulfuric acid can be maintained by adding concentrated sulfuric acid as the reaction progresses, i.e., semi-batch operation. Good temperature control of such systems can be maintained, as we shall discuss later. 

Thermo dynamic data for nitric acid are given ia Table 2. Properties for the ternary systems sulfuric acid—nitric acid—water (5,14) and magnesium nitrate—nitric acid—water (11,15—17) used ia processes for concentrating nitric acid are available. 

Figure 14.4 Schematic diagram of the cliromatographic system used for the analysis of very low concentrations of sulfur compounds in ethene and propene CP, pressure regulator CF, flow regulator SL, sanrple loop R, restriction to replace column 2 VI, injection valve V2, tliree-way valve to direct the effluent of column 1 to either column 2 or the restriction column 1, non-polar- capillary column column 2, tliick-film capillary column SCD, sulfur chemiluminescence detector FID, flanre-ionization detector.

The classical discoveries of the reacting nitrosation reagents mentioned above were mainly the result of kinetic investigations. There were some surprising results, e.g. the dependence of the diazotization rate on the square of the nitrous acid concentration in sulfuric or perchloric acid up to 0.3 M. Nitrous acid is a fairly weak acid (pK = 3.1569). Therefore, the low concentration of nitrite ions in the last step of the nitrous acid equilibria system of Scheme 5 does not appear to favor the formation of dinitrogen trioxide. N2O3 is, however, strongly indicated by the second order of rate on the (analytical) nitrous acid concentration. 

When elemental sulfur or a sulfur-bearing compound is present in any combustion system, the predominant product is sulfur dioxide. The concentration of sulfur trioxide found in combustion systems is most interesting. Even under very lean conditions, the amount of sulfur trioxide formed is only a few percent of that of sulfur dioxide. Generally, however, the sulfur trioxide concentration is higher than its equilibrium value, as would be expected from the relation... 

Infrared spectra suggested that a sulfate ion coordinates to two titanium atoms as a bidentate in particles. The maximum particle size was found at Aerosol OT mole fraction of 0.35 in the mixtures. The particle size increased linearly with increasing the concentration of sulfuric acid at any Wo, but with increasing Wo the effect was the opposite at any sulfuric acid concentration. These effects on the particle size can be explained qualitatively in relation with the extent of number of sulfate ions per micelle droplet. These precursor particles yield amorphous and nanosized TiO particles, reduced by 15% in volume by washing of ammonia water. The Ti02 particles transformed from amorphous to anatase form at 400°C and from anatase form to rutile form about at 800°C. In Triton X-100-n-hexanol-cyclohexane systems, however, spherical and amorphous titanium hydroxide precursor were precipitated by hydrolysis of TiCl4 (30). When the precursor particles were calcinated,... 

Efforts to develop modified Claus processes that will operate with low concentrations of sulfur in the feed gas have been previously mentioned. A similar system is being laboratory tested at IGT which does not require precise, instantaneous control of the oxygen/sulfur feed ratio. 

Description Aniline is produced by the nitration of benzene with nitric acid to mononitrobenzene (MNB) which is subsequently hydrogenated to aniline. In the DuPont/KBR process, benzene is nitrated with mixed acid (nitric and sulfuric) at high efficiency to produce mononitrobenzene (MNB) in the unique dehydrating nitration (DHN) system. The DHN system uses an inert gas to remove the water of nitration from the reaction mixture, thus eliminating the energy-intensive and high-cost sulfuric acid concentration system. 

In sulfuric acid production, acid brick lining of membrane coated mild steel tanks and reaction vessels is considered the most durable and versatile construction material for the sulfuric acid plant. Such linings wiil reduce the steel shell temperature and prevent erosion of the normally protective iron sulfate film that forms in stagnant, concentrated (oxidizing) sulfuric acid. Dilute (red uC ing) sulfuric acid solutions are very corrosive to carbon steel, which must be protected by impermeable (e.g., elastomeric) membranes and acid brick lining systems. Such acid brick linings often employ membranes comprising a thin film of Teflon or Kynar sandwiched between layers of asphalt mastic. 

The underflow of the cyclone 7 is withdrawn by an eccentric worm pump 8 and delivered to a belt filter press 9 yielding a highly dewatered cake and a filtrate consisting essentially of water but loaded with small concentrations of sulfuric acid, furfural, and by-products. This filtrate is recycled to tank 1 for preparing the feed stock slurry. Due to this scheme, most of the sulfuric acid is recovered and reutilized, the only loss being the quantity contained in the cake. This loss is replaced in tank 1. Analogously, the water leaving the system with the cyclone vapor and the cake is also replenished in tank 1 so that the overall mass balance is satisfied. 

The effect of SO-j on tlie rate of the selective catalytic rcductiori(SCR) of NO by NH3 over a mordenile type ztiolUe catalyst has been examined in a flotv reactor system. The deactivation of the catalyst is strongly dependent on the I eaction temperature and independent of the SO2 feed concentration. The sulfur content of the catalyst and its surface area appear to be dominant deactivation parameters. The catalytic activity is inversely related to the sulfur content of the catalyst. 

Figure 1.4 Enthalpy-concentration of sulfuric acid-water system relative to pure components. (Water and H2SO4 at 32°P and own vapor pressure.) (Data from International Critical Tables, 1943 O. A. Hougen and K. M. Watson.)...

Figure 1. Mn concentration and pH as a function of acid concentration in sulfuric iK id/ hydrazine systems.

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... 

Figure 5. Composition of gases from sulfur dioxide concentrating systems (dry basis)...

The factorial map F1F2 (Figure 12.2), which accounts for most of the variance of the system (i.e. 62.23 percent), clearly reveals an opposition between the presence or the absence of detectable concentrations of sulfur... 

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