Partial pressure sulfur dioxide

The choice of a specific CO2 removal system depends on the overall ammonia plant design and process integration. Important considerations include CO2 sHp required, CO2 partial pressure in the synthesis gas, presence or lack of sulfur, process energy demands, investment cost, availabiUty of solvent, and CO2 recovery requirements. Carbon dioxide is normally recovered for use in the manufacture of urea, in the carbonated beverage industry, or for enhanced oil recovery by miscible flooding. 

Partial Pressures of H O and SO2 over Aqueous Solutions of Sulfur Dioxide ... 

TABLE 2-144 Partial Vapor Pressure of Sulfur Dioxide over Water, mm Hg... 

The sulfation reaction does not have an optimum reaction temperature under pressurized operating conditions and the higher partial pressure of oxygen results in increased conversion of sulfur dioxide to sulfur trioxide. 

The very important factor for the efficient sulfoxidation of alkanes is the partial pressure of sulfur dioxide. The study of alkanes sulfoxidation under S02 pressures higher than 1 atm proves that an optimal temperature exists for alkane sulfoxidation. The data (vmax) on different alkane sulfoxidation are listed below [25], The reaction rate v was the maximal rate measured in the experiment. 

A realistic boundary condition must account for the solubility of the gas in the mucus layer. Because ambient and most experimental concentrations of pollutant gases are very low, Henry s law (y Hx) can be used to relate the gas- and liquid-phase concentrations of the pollutant gas at equilibrium. Here y is the partial pressure of the pollutant in the gas phase expressed as a mole fraction at a total pressure of 1 atm x is the mole fraction of absorbed gas in the liquid and H is the Henry s law constant. Gases with high solubilities have low H value. When experimental data for solubility in lung fluid are unavailable, the Henry s law constant for the gas in water at 37 C can be used (see Table 7-1). Gas-absorption experiments in airway models lined with water-saturated filter paper gave results for the general sites of uptake of sulfur dioxide... 

Here PNO2 partial pressure of nitrogen dioxide in pascals (1 Pa = 0.000145 psi), and the activation energy is 3870 kJ/mol. Other saturated polymers are less susceptible to attack by NO2 than most unsaturated polymers such as synthetic rubbers (polyiso-prene, polybutadiene, and butyl rubber). The presence of oxygen also tends to accelerate degradation by NO2. The reaction of sulfur dioxide with saturated polymers is complex, but appears to be activated by ultraviolet radiation. 

Direct-oxidation processes can conveniently remove H2S from the process gas to levels of 100 ppm. At significantly greater cost, levels of perhaps 10 ppm can be achieved. The systems are characterized by relatively low sulfur-carrying capacities and, therefore, high liquor recirculation rates. They are not generally applicable to gas streams with high partial pressures of carbon dioxide the carbon dioxide also dissolves in the solution, causing a pinch in the column and a reduction of sulfur purification capability. 

The dew point must be warmer than -56.6°C to permit use of liquid carbon dioxide absorbent because pure liquid carbon dioxide cannot exist below the triple point. The carbon dioxide partial pressure, i.e., gas phase CO2 mol fraction times total pressure, of synthesis gas mixtures with -56.6°C dew points is plotted versus synthesis gas pressure in Figure 4. Increasing the H2 CO ratio at fixed total pressure decreases the carbon dioxide partial pressure required for a -56.6°C dew point. Liquid carbon dioxide can be used to absorb sulfur molecules for any combination of gas pressure and carbon dioxide partial pressure which lies above the curves of Figure 4. 

Although the process requires the treated gas to have a certain minimum carbon dioxide partial pressure for removal of sulfurous compounds with liquid carbon dioxide, promising new SNG processes under development produce medium to high carbon dioxide content crude gases ideally suited for acid gas removal via the CNG process (12,13). The novel features of the CNG process have been demonstrated with bench-scale process development units second generation process development units are in various stages of... 

At elevated pressure, the partial pressure of carbon dioxide inhibits calcination, and sulfur dioxide is captured by displacement of the carbonate radical. The overall effect is similar except, as no free lime is formed, the resulting sorbent ash is less alkaline, consisting solely of CaS04 and CaCOs. 

Example 9-2 Olson and Schuler determined reaction rates for the oxidation of sulfur dioxide, using a packed bed of platinum-on-alumina catalyst pellets. A differential reactor was employed, and the partial pressures as measured from bulk-stream compositions were corrected to fluid-phase values at the catalyst surface by the methods described in Chap. 10 (see Example 10-1). The total pressure was about 790 mm Hg. 

From previous studies and the qualitative nature of the rate data a likely combination appeared to be a controlling surface reaction between adsorbed atomic oxygen and unadsorbed sulfur dioxide. In order to determine ail the constants in the rate equation for this mechanism, it is necessary to vary each partial pressure independently in the experimental work. Thus measuring the rate of reaction at different total pressures but at constant composition is not sufficient to determine all the adsorption equilibrium constants. Similarly, if the data are obtained at constant composition of initial reactants but varying conversions, the partial pressures of the individual components do not vary independently. However, in these cases it is possible to verify the validity of the rate equation even though values of the separate adsorption equilibrium constants cannot be ascertained. Olson and Schuler studied the effect of conversion alone and obtained the data in Table 9-1 at 480°C. 

Because the partial pressures of sulfur dioxide and sulfur trioxide are both small, the value of will not vary significantly with conversion. Hence may be... 

The numerical results are more meaningful if they are converted to partial pressures.-In atmospheres, the difference between bulk and surface pressures of sulfur dioxide is... 

Example 13-5 Using the one-dimensional method, compute curves for temperature and conversion vs catalyst-bed depth for comparison with the experimental data shown in Figs. 13-10 and 13-14 for the oxidation of sulfur dioxide. The reactor consisted of a cylindrical tube, 2.06 in. ID. The superficial gas mass velocity was 350 lb/(hr)(ft ), and its inlet composition was 6.5 mole % SO2 and 93.5 mole % dry air. The catalyst was prepared from -in. cylindrical pellets of alumina and contained a surface coating of platinum (0.2 wt % of the pellet). The measured global rates in this case were not fitted to a kinetic equation, but are shown as a function of temperature and conversion in Table 13-4 and Fig. 13-13. Since a fixed inlet gas composition was used, independent variations of the partial pressures of oxygen, sulfur dioxide, and sulfur trioxide were not possible. Instead these pressures are all related to one variable, the extent of conversion. Hence the rate data shown in Table 13-4 as a function of conversion are sufficient for the calculations. The total pressure was essentially constant at 790 mm Hg. The heat of reaction was nearly constant over a considerable temperature range and was equal to — 22,700 cal/g mole of sulfur dioxide reacted. The gas mixture was predominantly air, so that its specific heat may be taken equal to that of air. The bulk density of the catalyst as packed in the reactor was 64 Ib/ft. ... 

Sulfur dioxide (SO ) and nitrogen oxides (NO ) are oxidized to sulfate and nitrate aerosols either homogeneously rn the gas phase or heterogeneously in atmospheric microdroplets and hydrometeors Gas-phase production of nitric acid appears to be the dominant source of aerosol nitrate because the aqueous phase reactions of NO (aq) are slow at the nitrogen oxide partial pressures typically encountered in the atmosphere (5,i5). Conversely, field studies indicate that the relative importance of homogeneous and heterogeneous SO2 oxidation processes depends on a variety of climatological factors such as relative humidity and the intensity of solar radiation (4, -1 ). 

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