Uhdenora S.p.A.

This section is mainly composed by two absorbing systems:

the main chlorination system;
the tail gas absorption system.

Both are made by:

one packed tower;
two circulation tanks, one in operation and one in stand-by;
a battery of two circulation pumps; while one of them is in operation the other one performs transfer operations;
one cooler, which cools-down the circulating solution.

Ferrous chloride solution, coming from intermediate tank, is pumped to the tail gas absorption system.
A battery of three filters on the process line carries out suspended solid separation in order to avoid dangerous operations of the following absorption systems.
The tail gas absorption system provides for:

cooling of the FeCl₂ solution produced in the reactors from 70 °C to 40 °C;
washing of the tail gas leaving the chlorination tower in order to remove the last traces of chlorine.

Tail gas enters the bottom of the tower and flows upwards through the packing; the fresh batch of FeCl₂ solution, coming from circulation tank in operation enters the top of the tower, falls over the packing to the bottom and then returns to the circulation tank.

The cooler, placed before the tower, cools-down the circulating FeCl₂ solution. Cooling water flow rate to the exchanger is automatically controlled by TIC in order to keep the temperature of the solution leaving the tower at about 40°C.

Cooled ferrous chloride is then transferred to the main chlorination system where ferric chloride synthesis occurs by the packed tower.
Since the tower is at a constant but slightly negative pressure (as it is on the suction of the exhauster fan), chlorine gas enters the bottom of the tower and flows upwards through the packing.

The suction is kept constant by the pressure PIC controller which operates the automatic valve allowing atmospheric air into the system.
Chlorine is continuously fed to the tower and its flow rate is automatically controlled by FIC.

The FeCl₂ solution, coming from circulation tank in operation enters the top of the tower and falls over the packing to the bottom and then returns to the circulation tank.

Before entering the tower, the reacting solution is cooled-down by the cooler in order to remove the heat of reaction. Cooling water flow rate is automatically controlled by TIC in order to keep the temperature of the solution leaving the tower at about 45 °C.

As soon as the concentration of the produced ferric chloride reaches the desired value, the system should be switched to the stand-by tank and it is necessary provide for discharging operation of the produced batch.

Synthesised 40% FeCl₃ solution is stored in the tanks connected to two groups of pumps. The first one provide for FeCl₃ necessary to scrap iron reaction. The second one provide for tank trucks filling by the filling station.

Before the produced FeCl₃ solutions is sent to the filling station it should be recirculated through the mixer in order to carry out water dilution if necessary.

Practically two third of the ferric chloride solution are recycled back to the first step of the process, while one third constitutes the final product.