SO2 oxidation efficiency

Catalyst bed exit gas temperatures are also measured. They are indicative of each bed s SO2 oxidation efficiency. First catalyst bed exit gas temperature is especially important. This bed s catalyst may overheat and degrade near the bottom of the bed. 

This predicts high SO2 oxidation efficiency with low feed gas temperature. This prediction is discussed extensively in Chapter 12 onwards. 

This limitation is overcome industrially by passing T catalyst bed eidt gas through two or more gas cooling/catalytic oxidation steps - bringing SO2 oxidation efficiency up to... 

Chapter 12 shows that a 1 catalyst bed oxidizes less than 80% of its input SO2. It also indicates that this SO2 oxidation efficiency is increased to 98+% by passing T catalyst bed exit gas through a series of gas cooling/catalytic oxidation steps. 

Fig. 13.2 s SO2 oxidation efficiency is less than 70%. This low efficiency arises because ... 

The next chapter shows that attainment of equilibrium in the 2" catalyst bed increases SO2 oxidation efficiency even further - to almost 95%... 

Fig. 15.1. SO2 oxidation efficiency in two catalyst beds with gas cooling between beds. The 1 bed oxidizes 69.2% of 1 catalyst bed feed SO2 - the 2" bed an additional 25%. Note that the equilibrium curve is exactly the same for both catalyst beds, Section 15.1.1.

Cooling 1 catalyst bed exit gas and passing the cooled gas through a 2" catalyst bed increases SO2 oxidation efficiency from ... 

Fig. 16.4. Blowup of top portion of Fig. 16.3. Overall SO2 oxidation efficiency increases with each bed but the gain diminishes.

The following sections describe the effects of six industrial variables on 3-bed SO2 oxidation efficiency. Except where gas input temperature is variable, input gas temperature is 690 K, all beds. 

Fig. 18.4. Effect of gas pressure on intercept SO2 oxidation efficiency. The lines show that % SO2 oxidized increases with increasing pressure, all beds. After 3 catalyst beds the effect is small.

Fig. 18.5. Comparison of intercept SO2 oxidation efficiency with (i) 1.2 bar pressure in all beds and (ii) 1.3, 1.2 and 1.1 bar pressure in beds 1, 2 and 3. After 3 beds, the predicted efficiencies are virtually identical.

Fig. 18.6 describes the effect of SO2 concentration on intercept SO2 oxidation efficiency. It indicates that ... 

Fig. 18.6. Effect of 1 catalyst bed feed gas SO2 strength on intercept SO2 oxidation efficiency. The effect is significant after beds 1 and 2 but not after bed 3. The lower SO2 oxidation efficiency with higher SO2 strength is explained in Section 11.13.1 and Fig. 12.3.

Fig. 18.7 shows the effect of feed gas O2 strength on intercept SO2 oxidation efficiency. 

Figs. 18.8 and 18.9 show how catalyst bed input gas temperature affects intercept SO2 oxidation efficiency. Efficiency increases significantly with decreasing input gas... 

Fig. 18.9. Intercept % SO2 oxidized values as a function of catalyst bed gas input temperature. SO2 oxidation efficiency is seen to increase with decreasing input gas temperature.

The reason for double contact s high SO2 oxidation efficiency is given in Figs. 19.6 and 19.7. 

Appendix U examines this situation. It shows that this small amount of SO3 has little effect on double contact s overall SO2 oxidation efficiency. 

Calculate the equivalent SO2 oxidation efficiency with 4 catalyst beds but no intermediate H2SO4 making. Use the technique described in Appendix S with all of Prob. 19.1 s temperatures and pressures. 

Fig. 20.1 compares the total SO2 oxidation efficiencies of these arrangements. The theoretical 1 - 3 arrangement is also shown. 

Fig. 20.1. Total SO2 oxidation efficiencies of 4 four-catalyst-bed arrangements. The 3 - 1 bed arrangement is seen to be the most efficient.

Fig. 20.2. SO2 oxidation efficiency of 5 five-catalyst bed arrangements. The 4 - 1 arrangement is the most efficient. It is, however, only slightly more efficient that the 3 - 2 arrangement.

Fig. 20.3. SO2 oxidation efficiency of acid plants with 1 catalyst bed after intermediate H2SO4 making. Oxidation efficiency increases with increasing number of before-intermediate-H2S04-making beds. However, the difference between 3 -1 and 4 - 1 plants is very small.

Fig. 20.4. Effect of catalyst bed gas input temperature on double contact SO2 oxidation efficiency. Efficiency falls slightly with increasing gas input temperature.

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