FIG. 3.6.10 Integrated process development.

FIG. 3.6.11 Letter acid production. (Reprinted, with permission, from Ian G. Laing, 1992, Waste minimisation: The role of process development, Chemistry & Industry [21 September].

Raw material consumption reduced from 13.3 tn to 7.5

tn per ton of product—a decrease of 44%. The solvents were recycled, and the hydrochloric acid (gas) was converted back to chlorosulphonic acid and recycled in the process. Sulfur dioxide gas was purified, liquified, and sold for external recycling (no sulfur dioxide emissions). All waste was reduced by about half and the aqueous effluent by about 80%. The organic load in the aqueous effluent was reduced by more than 97% through the integration of wet air oxidation, and waste gas was reduced to zero through the inclusion of waste air incineration.

As in another plant, the waste was drastically reduced but not totally eliminated. Even with ever increasing automation and processing technologies, the optimization between the input and output streams of a production process is never complete. The potential for improving efficiency always exists.

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