Multi-stage circulation evaporators that employ heat recycling have proven themselves in technical practice with regard to the concentration of sulfuric acid beginning at a starting concentration of 20 wt% up to a final concentration of 70 wt%. Due to great water evaporation, the condensation heat of the exhaust steam is almost fully employed to heating in order to save energy.

Multi-stage Evaporator

The presented example displays a three-stage plant that is operated at 100 mbar, 300 mbar, and ambient pressure. Other combinations of steam heating and energy integration are possible, and are aligned to available steam pressures and waste acid concentration.

The evaporation behavior of the acid must also be considered, e.g. for soluted gasses, foaming or precipitationing, and crystallisation of soluted ingredients.

In many cases , it may be technically or economically of advantage to use forced circulation evaporators or horizontal evaporators instead of standard evaporators.