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Vitold Bakhir Electrochemical Systems and Technologies

FEM-7 Flow-Through Electrochemical Module Cell

FEM-7 cell, 2002

Electrochemical modular cell to treat water solutions, a device to produce products of anodic oxidation of alkaline or alkaline-earth metal chloride solutions

RF Patent No. 2176989. Priority claimed on 01.11.2000, published on 20.12.2001.

Authors: V. M. Bakhir, Yu. G. Zadorozhny, B.I. Leonov, S. A. Panicheva

FEM-7 module is a tiny diaphragm-type electrolyzer with co-axially mounted electrodes and a diaphragm. The outer electrode of FEM-7 module serves as cathode and is made of titanium. The inner electrode (anode) is also made of titanium. Anode’s surface has a special coating (the know-how technology). Particularly firm anodic coating (as compared to routinely used ORTHA electrodes) under equal other operational conditions has a 800 – 1500 times longer service life. Experience of continuous five-year anode operation in AQUACHLOR device demonstrated no signs of wear and tear of original anodic coating. Deteriorated anodic coating is easily replaced by a new one, since the anode itself in the process of operation is immune to wear: working voltage on FEM-7 module is not sufficient to disrupt protective oxide film. FEM-7 module ceramic diaphragm is made of zirconium, aluminum and yttrium oxides, it is exclusively resistant to the action of acids, alkali, oxidants and reductants; withstands up to 5 atm bursting pressure and has an unlimited service life. No diaphragm cleansing is required in the process of AQUACHLOR operation if a softened saline solution is used for the device’s supply. When a saline solution containing hardness salts is used, the diaphragm should be regularly cleaned with a 5% hydrochloric acid. Cleaning is performed by rinsing the reactor of AQUACHLOR device for 15-30 minutes, without disassembly thereof. The voltage on a single FEM-7 module in the process of operation can vary from 2,8 to 4,5 V, at current strength ranging between 20 and 35 A and source solution mineralization being from 200 to 250 – 300 g/l. The degree of salt decomposition under any mode of operation is 99,3 – 99,8 %. In this connection, actual specific salt consumption for the production of oxidants in AQUACHLOR device is approximately 1,7 g per 1 g of oxidants.

At current strength of 23 – 24 A, a FEM-7 module’s output of oxidants is 30 g/h (in terms of molecular chlorine), and the voltage on it approaches 2,8 – 2,9 V, with specific power consumption being about 2 kWt per 1 kg of oxidants (chlorine). Under this mode of operation, the share of molecular chlorine in isolated gas is 98 – 99%.

Electrochemical unit of Aquachlor-50 device is represented by two FEM-7 modules. In 2002, Aquachlor devices were approved by State Sanitary and Epidemiological Control Committee of Russia as systems for disinfection of drinking water, swimming pool water and wastewater. The device’s oxidant output is 50 g/h (50 cu. m. per hour of decontaminated water), consumed electric power – 100 W.