RF Patent # 2208589. Filed 03.08.2001, published 20.07.2003.
Bakhir V.M., Zadorozhny Yu.G., Panicheva S.A.
When FEM-3 modules in an RPE reactor are hydraulically connected in parallel, the reactor’s specific parameters and operational characteristics generally precisely correspond to the parameters and characteristics of a single FEM-3 module. This makes it possible to competently develop engineering electrochemical systems with RPE reactors of required capacity on the basis of similar parameters for a single FEM-3 module working in the corresponding regime.
Based on well-known facts that mass m of substances engaged in electrochemical reactions is determined by consumed electricity amount Qe: m = q ´ Qe, where Qe = I ´ t ; q = M/nF, and that given the same electricity amount power Wm consumed during the process is determined only by voltage value U: Wm = I ´ U ´ t , where U = Udecomp. + Upol + I ´ R, investigations were conducted using various electrochemical systems of the relationship between the degree of deviation of physico-chemical parameters of activated solution from equilibrium state (degree of solution meta-stability), intensity and depth of electrochemical impact, as well as initial solution mineralization. The investigations demonstrated that meta-stable (relaxing in time) properties and physical-chemical parameters of anolyte and catholyte produced in conditions of equal specific electricity consumption depended on the degree of electrochemical exposure nonequilibrium, and not on electrolysis laws. Most essentially, meta-stability degree of diluted sodium chloride aqueous solution is affected by the mechanism of charge transfer through the diaphragm of a flow-through electrochemical reactor, depending on the ratio of specific electricity amount and initial water mineralization. At I/Q < F´ cNaCl, hydroxyl (OH- ) and hydroxonium (H+ ) ions practically do not participate in charge transfer through the diaphragm due to their low concentration in comparison with that of chlorine anions and sodium cations. At I/Q @ F´ cNaCl all ions present in the initial solution take part in charge transfer. At I/Q > F´ cNaCl charge transfer is performed only by hydroxyl (OH- ) and hydroxonium (H+ ) ions.
Investigations of single FEM-3 modules showed that in the process of ANK anolyte production according to a flow-sheet envisaging direct-flow movement of solutions in electrode chambers, anolyte oxidant concentration is on the average 15% lower than under counterflow of solutions in electrode chambers. Besides, it was found that regulation of ANK anolyte рН by discharging part of catholyte was more efficient with solutions’ moving in counterflow, since in that case the required volume of discharged catholyte decreased on the average by 20% as compared to a flow-sheet with direct flow (that is, in one direction) of solutions in the electrode chambers of FEM-3 module.
Based on the analysis of experimental research, the flow sheet of ANK anolyte production engaging two hydraulically and consecutively connected FEM-3 modules in a counterflow regime described in the patent was developed.
It was found that such FEM modules’ connection makes it possible to develop an efficient reactor for ANK anolyte production from initial sodium chloride solution of less than 2.5 g/l concentration and 500-600 mg/l oxidants’ content. Bearing in mind that the general mineralization/oxidant concentration ratio of ANK anolyte produced by STEL-10Н-120-01 and STEL-60-03-АНК devices lies within the limits of 10-15, and the corresponding parameter for ECA-30-type devices by far surpasses those figures, the general mineralization/oxidant concentration ratio of ANK anolyte produced by reactor with two consecutively connected FEM-3 modules varies between 5 and 7, which is an important factor of decreasing anolyte corrosive ability. ANK anolyte with the latter-indicated values of the general mineralization (which generally corresponds to sodium chloride concentration in the initial solution) / oxidant concentration ratio is called ANK anolyte with mean specific oxidant content, as distinct from ANK anolyte with the above parameters’ ratio of 10 and higher, which is designated АNК anolyte with low specific oxidant content.