Single contact acidmaking catalyst beds

Double contact acidmaking is more efficient than single contact acidmaking. This has made it the most used industrial process. The reason for its high efficiency is its efficient oxidation of S02 in its after-H2S04-making catalyst bed(s), Chapter 19. 

Figure 19.7 Four catalyst bed single contact acid plant. The third catalyst bed heatup path and intercept are the same as in Figs. 16.3 and 16.4. The fourth bed is new (Table S.4 in Appendix S). Note that (a) the fourth bed oxidizes less than half of the third bed s exit SO2 whereas (b) Fig. 19.6 s after-H2S04-making bed oxidizes 98.9% of the third bed exit SO2 (Section 19.6). This explains the greater efficiency of double contact acidmaking.

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