Heatup paths curve intercepts

C02 has no effect on S02 + /202 — S03 equilibrium curves, Appendix F. It does, however, have a small effect on heatup paths and intercepts, Fig. 12.6. 

Fig. 12.7. Equilibrium curves, heatup paths and intercepts for 12 volume% S02 feed gas. 690 K feed gas gives a 915 K intercept temperature, in the catalyst degradation range. 660 K feed gas gives a 900 K intercept temperature, avoiding degradation.

This chapter assumes that equilibrium is attained in an acid plant s 1st catalyst bed, i.e. that a feed gas s heatup path always intercepts its equilibrium curve. 

C02-in-feed-gas affects catalyst bed heatup paths and intercepts (but not equilibrium curves, Appendix F). The remainder of this chapter indicates how C02-in-feed-gas affects ... 

Fig. 17.1 shows the effect of C02 on a 1st catalyst bed heatup path and intercept. C02 has no effect on equilibrium curves, Appendix F. 

Fig. 7.5. Heatup path for gas descending the Fig. 7.1 catalyst bed. It begins at the feed gas s input temperature and 0% SO2 oxidized. Its temperature rises as S02 oxidizes. Maximum attainable S02 oxidation is predicted by the heatup path-equilibrium curve intercept, 69% oxidized at 893 K in this case. This low % SO> oxidized confirms that efficient SO-> oxidation cannot be obtained in a single catalyst bed. Multiple catalyst beds with gas cooling between must be used.

For an intercept calculation to be valid, its heatup path and equilibrium curve must be for the same feed gas. Each intercept calculation must, therefore, specify a feed gas... 

Table 12.1 shows heatup path and equilibrium curve % S02 oxidized-temperature points near a heatup path-equilibrium curve intercept. They are for ... 

Fig. 12.3. Heatup paths, equilibrium curves and intercepts for 7, 10, and 13 volume% S02 feed gas. Volume% 02/volume% S02 ratio =1.1. Intercept temperature increases with increasing S02 strength. Intercept % S02 oxidized decreases with increasing S02 strength. The intercepts have been calculated as described in Appendix J.

These pressure differences have no effect on heatup paths, Fig. 12.4 - and little effect on equilibrium curves and intercepts. Intercept temperature and % S02 oxidized both increase slightly with increasing pressure. 

Fig. 12.8. Heatup path, equilibrium curve and intercept for 660 K, 13 volume% S02 feed gas. With 13 volume% S02 and higher, catalyst degradation is likely even with 660 K feed gas. 660 K is about the lowest temperature at which V, alkali metal, S, 0, Si02 catalyst is fully active.

Catalyst bed S02 + /202 — S03 oxidation is represented by heatup paths and equilibrium curves. Maximum S02 oxidation occurs where a feed gas s heatup path intercepts its equilibrium curve. 

Now determine the %S02 oxidized - temperature point at which the Problem 11.4 heatup path intercepts the Problem 10.4 equilibrium curve. 

Fig. 13.2. 1st catalyst bed heatup path, equilibrium curve and intercept point, from Fig. 12.1. The 1st catalyst bed s exit gas is its intercept gas, Section 12.12. It is cooled and fed to a 2nd catalyst bed for more S02 oxidation.

Table 15.1. 2nd catalyst bed % S02 ox/d/zed/temperature points near heatup path-equilibrium curve intercept. They have been calculated as described in Appendices K and D. 

Interpolation suggests that Table 15.1 s heatup path intercepts its equilibrium curve at ... 

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