Oxidation Reduction Potential for Ferric Chloride Endpoint Control

For over 40 years, Powell Oxidation Reduction Potential Electrodes (ORP or Redox) have been used to monitor the endpoint reaction of ferrous chloride (FeCl2) and chlorine (Cl2) to produce ferric chloride (FeCl3).

The Powell ORP electrodes are in-line instruments that are typically mounted with redundant sets in bypass lines to allow maintenance to be performed without shutting the process down.

The MVDC signal from the electrodes are connected to any industrial quality ORP to 4/20 mA current transmitter etc. at the endpoint reaction.

Some basic information on the MVDC signal during the reaction is as follows:

Temperature (F) Corrected Specific Gr. Ferric (%) Ferrous (%) HCl (%) ORP MVDC
120 1.4904 11.92 34.00 0 525
120 1.4596 12.47 31.59 0.15 485
134 1.4038 13.44 27.47 0.3 500
138 1.4328 12.67 26.50 0 521
156 1.5058 45.60 0.25 0 731
128 1.485 44.00 0.17 0.32 719
132 1.4585 40.62 0.17 0 726
134 1.4313 40.00 0.15 0.19 741

As seen by the chart above, keeping the free acid as low as possible in the ferrous/ferric chloride reaction will result in more repetitive end point control.

Contact Powell for further information. Powell can assist in all phases including chlorine unloading, scrubbers, Tefzel magnetic drive pumps, Titanium pumps, heat exchangers, valves, and piping products.

Oxidation Reduction Potential (ORP) for Ferric Chloride Endpoint Control