Double contact flowsheets

Fig. 1.4. Double contact sulfuric acid manufacture flowsheet. The three main S02 sources are at the top. Sulfur burning is by far the biggest source. The acid product leaves from two H2SO4 making towers at the bottom. Barren tail gas leaves the final H2S04 making tower, right arrow.

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. 9.6 is a flowsheet for double contact H2S04 making. It shows ... 

Fig. 19.2. Double contact acidmaking flowsheet with numerical values used in this chapter s calculations. The plant consists of 3 catalyst beds followed by intermediate H2S04 making and a 4th catalyst bed. The gas from the last catalyst bed goes to cooling and final H2S04 making (not shown). All kg-mole values are per kg-mole of 1st catalyst bed feed gas. Gas pressure = 1.2 bar, all beds.

Figure 9.6 Double contact H2SO4 making flowsheet. The two absorption towers are notable. The left half of the flowsheet oxidizes most of the S02-in-feed-gas and makes the product SO3 into strengthened sulfiiric acid. It makes about 95% of the plant s new H2SO4. The right half of the flowsheet oxidizes almost all the remaining SO2 and makes its product SO3 into strengthened sulfuric acid. The final exit gas is very dilute in SO2 and SO3. Industrially, all the catalyst beds are in the same converter (Fig. 7.7). Table 23.2 gives industrial final H2SO4 making data.

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