Chlorine Removal

Input - Output Structure

As in the previous example the input-output level, as in Figure 1, shows a feed flow control loop and two incomplete composition loops.

Figure 1 - Chlorine Removal : Input/Output Structure

Final Structure

The process has no recycle as the caustic emerges with the chlorine in the form of sodium hypochlorite NaClOCl. Note that this has to be treated before being discharged, although this is not specified as part of the process. The expanded block diagram, figure 2 below, shows the functional blocks. These are rather straightforward, so no process flow sheet is shown.

The absorber would run open to atmosphere with the pipework pressure setting the stripper pressure somewhat above ambient. A blower would obviously be required on the air supply, so the valve there would probably be a motor speed adjustment. Although the absorption of chlorine in NaOH is highly exothermic, the exit stream from the stripper would be quite dilute, so temperature regulation on the absorber would be unnecessary.

Figure 2 - Chlorine Removal : Final Structure

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