Metallgesellschaft Aktiengesellschaft

Gunter Roller

Dieter Stein

Ulrich Wagner

Ludwig Englmaier

Ingo F Litzenberger

A solution to be evaporated is passed through one or several evaporation stages. In each evaporation stage, the solution is circulated between a heat exchanger and an evaporating vessel, and steam is withdrawn from the evaporating vessel. For removing crusts, the evaporation in the respective evaporation stage is interrupted, and a cleaning suspension containing at least 3 wt % granular solids is circulated through the heat exchanger and the evaporating vessel. The solids, which have an abrasive effect, remove the crusts. Preferably, the solution to be evaporated is circulated through the evaporation stage for removing the crusts, where the heat exchanger is heated and the cleaning solution is evaporated to such an extent that solids crystallize out and a cleaning suspension is formed.

Method of removing encrustations in evaporation plants

An aqueous ammonium alum solution which contains Fe.sup.3+ ions and has a pH not in excess of 5 is passed through at least one half of the Fe.sup.3+ ions in the solution to Fe.sup.2+ ions. The solution is cooled and ammonium alum is crystallized whereas the Fe.sup.2+ ions remain in the liquid phase.

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Bad Homburg, Germany

Gunter Roller