Isothermal conditions, prediction from

If the S02 and 02 concentrations are switched 180° out of phase so that S02 is absent from the reactor feed during one half cycle and 02 is absent in the other half cycle, Fig. 6 shows that is less than 1 regardless of the cycle period. Forcing just the S02 concentration at a constant 02 concentration also fails to enhance the rate of S02 oxidation in a back-mixed reactor. Even though the experiments of Unni et al. (1973), discussed earlier, were performed under isothermal conditions and differentially so that they could have been simulated by Strots model, the strategy used by Unni was different from those investigated. Nevertheless, one of the experiments undertaken by Unni switched between a reactant mixture and a feed that did not contain S02. This experiment exhibited < 1. Strots model predicts this observation. 

This chapter has outlined the basic ingredients of a scheme for predicting from fundamental quantities the rate of uptake of fission products by spherical particles under dynamic conditions of temperature and pressure. A subsequent paper by Adams, Quan, and Balkwell (1) will present laboratory verification that the approach is on sound ground for isothermal conditions. Additional work is desirable to test the validity of the anisothermal approach to various cooling rates over large temperature extremes. 

The calculated isothermal elastic tensor for yS-HMX is compared in Table 8 to the one reported by Zaug (isentropic conditions). Uncertainties in the calculated elastic coefficients represent one standard deviation in values predicted from five contiguous two nanosecond simulation sequences from the overall ten nanosecond simulation. As mentioned above, Zaug s experiments sufficed to determine uniquely five of the thirteen elastic constants (modulo the... 

The results shown in Fig. 12.10 indicate that both the simplified model and the measured parameters of reaction rates and mass transport describe the general trends identified during the experiments. Clearly, these predictions do systematically underestimate the conversions achievable. This may be in particular due to deviations from isotherm conditions occuring in the reactor. 

Here Ju is the rate of energy density transfer across unit cross-section in unit time arising from the flux in moles of species 1 across unit-cross section in unit time. This ratio is clearly the energy transported under isothermal conditions per mole of species 1, denoted by Uj in Eq. (6.6.3). We see then that a thermomechanical effect is predicted for a fixed pressure difference across the junction, AP, and at constant temperature, a particle flux J1 gives rise to a proportional energy transport - Ujjx. This is a very sensible conclusion. 

R. W. H. Sargent The COj-No (or rather C02-air) values were obtained indirectly from studies on a fixed-bed separation process for removal of CO2 from air. These studies were made on a bed of pellets 4 ft long and 4 inches in diameter two pellet sizes were used, and a range of air flow rates was covered at pressures from 1 to 25 atm and from +15° to —40°C. All the results were successfully predicted by a model assuming both pellet-pore and intracrystalline diffusion under isothermal conditions the two relevant diffusivities were used as adjustable parameters to fit the experimental break-through curves by least squares for one set of conditions at each temperature, and these values then pre-... 

The densification process in rotational molding has been studied from both fundamental and practical perspectives. The models presented in the previous sections have furthered the understanding of the densification process in rotational molding however, their use has been limited to the prediction of the densification process carried out under isothermal conditions. It is well known that heat transfer, powder coalescence, bubble formation, and bubble dissolution are collectively important in rotational molding however, very few studies have addressed all aspects in modeling the densification process in rotational molding. 

Predict the global rate of reaction for the oxidation of SO2 at bulk-gas conditions of 20% conversion at 480°C. Other conditions are as given in Prob. 10-2. The rate at the catalyst surface is to be calculated from Eq. (G) of Example 9-2. Assume isothermal conditions. The constants in this equation at 480°C are... 

The K-butane pyrolysis is analysed here as an initial, simple example of a pyrolysis reaction mechanism. It is important to note that the pyrolysis reactions of small hydrocarbons are fundamental to the proper understanding of the whole process. In fact, the pyrolysis mechanism displays a typical hierarchical structure and the small hydrocarbons must be analysed first. Fig. 1 shows the main and minor products from K-butane decomposition, under isothermal conditions, at 1,093 K and 1 atm. Ethylene, propylene and methane are the main products, while only trace amount of butenes, ethane, benzene and cyclopenta-diene are observed. These model predictions have been confirmed and validated by several experimental measurements (Dente and Ranzi, 1983). 

At isothermal conditions, the catalytic performance of a mixture of regenerated and coked catalyst can be predicted from the performance of a physical mixture. In industrial operation, the use of such mixtures changes local temperatures and associated reactions without affecting the overall heat balance of the FCC unit. As a result, the overall performance of the process can be largely affected. 

Furthermore, when the coke itself is not determined, only one deactivation function can be derived, from the decay with time of the main reactioa The model may then be biased. There is more, however. Since coke content, which is related to the local concentration of the reacting species, it predicts a deactivation independent of concentration that is, the approach predicts a uniform deactivation in a pellet or a tubular reactor (e.g., for isothermal conditions at least). In reality, nonunifonnity in deactivation, because of coke profiles, does occur in pellets (or tubular reactorsX as will be shown in the next section. The consequences of neglecting coke profiles in kinetic studies, in catalyst regeneration, or in design calculations may be serious (see Froment and Bischoff [12, 13]). 

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