Detector and electronic circuit to control redox reaction - partic. to purify chromic and acid effluents from industrial process

摘要

The detector is fitted inside the reactor and comprises an electrode sensitive to the redox reaction and an associated reference electrode. Difference in potential between the sensing and referene electrodes provides a signal which actuates the circuit to regulate the rate of admission into the reactor of at least one reagent. The reactor now also contains a second detector assembly combining a pH-sensitive electrode with associated reference electrode. The electronic circuit correlates input signals from the two detector assemblies to produce a combined output signal which regulates the rate of admission of reagent(s). The output signal is developed to represent the deg ree to which the redox reaction has advanced. The output signal is corrected to be independent of the pH value in the reactor, provided that the pH value lies within an acceptable range. Used for purificn. of waste water esp. effluent from metal finishing and electro-plating factories, e.g. sodium bisulphite used to reduce hexavalent to trivalent chromium andsodium hypochloride used to oxidise cyanide to cyanate. The redox detector does not suffer from variations in potential arising from changes in pH valve of liq. to be treated.