Flowsheets single contact

Fig. 9.1. Single contact H2SO4 making flowsheet. SO3 rich gas from catalytic SO2 oxidation is reacted with strong sulfuric acid, Reaction (1.2). The reaction consumes H20(f) and makes H2S04(f), strengthening the acid. Double contact H2SO4 making is described in Fig. 9.6. A few plants lower the SO2 content of their tail gas by scrubbing the gas with basic solution (Hay et al., 2003).

Fig. 21.1. Heat transfer flowsheet for single contact, sulfur burning sulfuric acid plant. It is simpler than industrial plants, which nearly always have 4 catalyst beds rather than 3. The gaseous product is cool, S03 rich gas, ready for H2S04 making. The heat transfer product is superheated steam. All calculations in this chapter are based on this figure s feed gas composition and catalyst bed input gas temperatures. All bed pressures are 1.2 bar. The catalyst bed output gas temperatures are the intercept temperatures calculated in Sections 12.2, 15.2 and 16.3.

Fig. 23.1. Simplified single contact sulfuric acid production flowsheet. Its inputs are moist feed gas and water. Its outputs are 98 mass% H2S04, 2 mass% H20 sulfuric acid and dilute S02, 02, N2 gas. The acid output combines gas dehydration tower acid, H2S04 making tower acid and liquid water. The equivalent sulfur burning acid plant sends moist air (rather than moist feed gas) to dehydration. Appendix V gives an example sulfur burning calculation.

This process is an extension of single-contact extraction, wherein the raffinate from the first stage is extracted with fresh solvent of the same composition in successive stages, as the flowsheet of Fig. 6.I80 indicates, the concentration of C in the raffinate thus being further reduced. Different quantities of solvent may be used in the various stages. 

Solvent Recovery. Only a single raflBnate, that from the last stage n, is treated for solvent recovery. The extracts from all stages are ordinarily combined and the mixture then treated for solvent recovery, although individual extracts may be treated separately if so desired. Refer to Fig. 6.20. The flowsheet and construction are the same for single contact except that a combined extract E is prepared ... 

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