APPARATUS FOR ION EXCHANGE PROCESS CONTROL

1286677 Ion exchange process control SINTEX ORGANICO-INDUSTRIAL SA 27 Aug 1969 [19 Sept 1968 22 May 1969] 42598/69 Heading B1J Operation of an ion exchange process in which ion exchange material in the form of a bed is used to treat liquid, for example to soften water, is controlled by a method which comprises generating a voltage proportional to two resistances, one resistance being the resistance measured between two electrodes disposed in the bed of ion exchange material at a small distance from where treated liquid leaves the bed and the other resistance being the resistance measured between two electrodes disposed in a vessel full of exhausted ion exchange material, the bed of ion exchange material and the vessel being so arranged that liquid to be treated passes through the vessel before entering the bed, and thereafter applying the generated voltage to electrical circuitry which controls means for indicating the state of the ion exchange material of the bed according to the magnitude of the generated voltage. The generated voltage may be amplified and used to operate a reading instrument, for example a meter or recording chart, and/or applied to electrical circuitry which produces a first signal when the generated voltage reaches a value corresponding to exhaustion of the ion exchange material and a second signal when the generated voltage reaches a value which is less than but near to the value corresponding to freedom of the ion exchange material from regenerant therefor; the presence or absence of such signals may be used for example to trigger a warning and/or to operate a valve or valves for controlling flow of fluid through the bed of ion exchange material. The aforementioned other resistance alternatively may be represented by the resistance of two parallel-connected resistances, in which case either one such resistance is the resistance of a resistor having fixed resistance and the other such resistance is the resistance measured between electrodes disposed in an empty receptacle or one such resistance is the resistance measured between electrodes disposed in a first empty receptacle and the other such resistance is the sum of the resistance of a resistor having fixed resistance and the resistance measured between electrodes disposed in a second empty receptacle arranged to be electrically in series with the resistor or one such resistance is the resistance of a first resistor having fixed resistance and the other such resistance is the sum