For regeneration of ferrous hydrochloric pickling solutions a number of regeneration processess are known. Since 1970, the most economically and ecologically advantegous process is the Pyrohydrolysis of spent pickling solutions.


Basiclly the chemical process consists of thermal decomposition of existent Fe2+ and Fe3+ chlorides and transformation into Fe2O3 at a temperature range of 300 - 900°C:


4 FeCl2 + 4 H2O + O2 -> 8 HCl + 2 Fe2O3

2 FeCl3 + 3 H2O           -> 6 HCl + Fe2O3


After separation of the oxide, the HCl in vapour phase is adiabatically absorbed and afterward returned into the pickling process.


This allows the complete regeneration of hydrochloric acid in a closed circuit. The now additionally formed iron oxide is an important raw material for many industries, such as ferrites, pigments, paints, corrosive protection, food additivies, etc.


To create a continous process a hadrochloric storage system is indispensable. Therefore a proper tank supply helps to work as a puffer and to manage to pass by shut down times of the pickling line and maintenance periods.



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