Explicit model conversion kinetics

Computed results from this model are compared to actual kiln performance in Table VI and the operating conditions taken from kiln samples are given in Table VII. There are no unit factors or adjustable parameters in this model. As with the explicit model, all kinetic data are determined from laboratory experiments. Values of the frequency factors and activation energies are given in Table VIII. Diffusivity values are also included. The amount of fast coke was determined from Eq. (49). With the exception of the T-B (5/12) survey, the agreement between observed and computed values of CO, CO2, and O2 is very good considering that there are no adjustable parameters used to fit the model to each kiln. In the kiln survey T-212/10, the CO conversion activity of the catalyst has been considerably deactivated and a different frequency factor was used in this simulation. 

All the previously cited models and works also consider, and some explicitly cite, this assumption—that the catalyst activity varies with time-on-stream (or with coke concentration [12]) in the same manner or with the same deactivation function (VO for all reactions in the network. That is, a nonselective deactivation model is always used. Corella et al. (16) have recently demonstrated that in the FCC process this assumption is not true and that it would be better to use a selective deactivation model. Another work (17) also shows how this consideration, when applied to catalytic cracking, influences the yield-conversion curves. Nevertheless, to avoid an additional complication, we will use in this chapter a nonselective deactivation model with the same a—t kinetic equation and deactivation function (VO for all the cracking reactions of the network. 

Analyses of monolith reactors specific for SCR applications are limited in the scientific literature Buzanowski and Yang [43] have presented a simple one-dimensional analytical solution that yields NO conversion as an explicit function of the space velocity unfortunately, this applies only to first-order kinetics in NO and zero-order in NH3, which is not appropriate for industrial SCR operation. Beeckman and Hegedus [36] have published a comprehensive reactor model that includes Eley-Rideal kinetics and fully accounts for both intra- and interphase mass transfer phenomena. Model predictions reported compare successfully with experimental data A single-channel, semianalytical, one-dimensional treatment has also been proposed by Tronconi et al [40] The related equations are summarized here as an example of steady-state modeling of SCR monolith reactors. 

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