Abstract: Electrolyzer for the electrolysis of a solution of a salt for the production of a solution containing an acid and a solution of a base, said electrolyzer comprising at least one elementary cell divided into three compartments by two cation-exchange membranes, the first of said compartments contains the first of said membranes and a cathode for hydrogen evolution and the production of the base, a central compartment is defined by said cation-exchange membranes and has an inlet for the solution of the salt and has an outlet for the withdrawal of the solution containing the acid, a third compartment contains the second of said cation exchange membranes and an anode, said anode comprises a porous electrocatalytic sheet for hydrogen ionization and a porous rigid current collector, said third compartment further has an inlet for a hydrogen-containing gaseous stream and an outlet for the venting of the rest of gas characterized in that said current collector has a multiplicity of contact points and said porous elect

Abstract: The novel jumper switch means of the invention is directed to by-passing an electrolyzer in a row of electrolyzers electrically connected in series to permit removal of the by-passed electrolyzer for maintenance. The jumper switch means comprises one or more internal bus bars connected to suitable arrays of switches, the internal bus bars being dimensioned in such a way that when substantially all the electrolysis current flows through the jumper switch means, the voltage at its two connection terminals and therefore at the contact points of the by-passed electrolyzer, is close to, but in any case lower than the voltage spontaneously reached by the electrolyzer when electrolysis current is no more fed. Further, the present invention offers the possibility of housing the array of switches and said internal bus bars in a structure having a U-shape wherein the planar part has a limited height which does not hinder the lateral removal of the by-passed electrolyzer by a suitable fork-lift truck.

Abstract: Electrolyzer comprising at least one elementary cell divided into electrolyte compartments by cation-exchange membranes, said compartments are provided with a circuit for feeding electrolytic solutions and a circuit for withdrawing electrolysis products, said cell is equipped with a cathode and a hydrogen-depolarized anode assembly forming a hydrogen gas chamber fed with a hydrogen-containing gaseous stream, characterized in that said assembly comprises a cation-exchange membrane, a porous, flexible electrocatalytic sheet, a porous rigid current collector having a multiplicity of contact points with said electrocatalytic sheet, said membrane, sheet and current collector are held in contact together by means of pressure without bonding.

Abstract: A membrane electrochemical cell, in particular a fuel cell, of an improved type comprising a multiplicity of cell elements, each element made up of bipolar plates, current collectors, electrodes and membranes, wherein the function of electric current transmission through the cell elements, the release of heat towards the outside environment, the distribution of electric current to the electrodes and membranes, the removal of heat from the electrodes and membranes and the distribution of the reactants and products are performed by distinct components, in particular bipolar plates for the first two and porous electroconductive collectors for the others. The bipolar plates may have flat surfaces without grooves and are preferably manufactured with aluminum, titanium or alloys thereof, through cheap mass productions techniques; the bipolar plates are used together with collectors provided with deformability, residual resiliency and high porosity.

Abstract: A membrane electrochemical cell, in particular a fuel cell, of an improved type comprising a multiplicity of cell elements, each element made up of bipolar plates, current collectors, electrodes and membranes, wherein the function of electric current transmission through the cell elements, the release of heat towards the outside environment, the distribution of electric current to the electrodes and membranes, the removal of heat from the electrodes and membranes and the distribution of the reactants and products are performed by distinct components, in particular bipolar plates for the first two and porous electroconductive collectors for the others. The bipolar plates may have flat surfaces without grooves and are preferably manufactured with aluminum, titanium or alloys thereof, through cheap mass productions techniques; the bipolar plates are used together with collectors provided with deformability, residual resiliency and high porosity.

Abstract: A chlor-alkali diaphragm electrolysis cell comprising pairs of interleaved cathodes (C) and anodes (B), said cathodes having surfaces with openings and are provided with porous corrosion resistant diaphragms, said cell further comprising feed brine inlets and outlets (H, I, L) for the removal of produced chlorine, hydrogen and caustic, said anodes (B) are expanded by internal extenders (F) and have electrode surfaces with openings for releasing produced gaseous chlorine, characterized in that each of said expanded anodes (B) comprises a plurality of pressing means (O,Q) made of corrosion resistant material having elastic properties to maintain the electrode surfaces of the anodes against the diaphragm and said pressing means are longitudinally positioned inside the anodes having very low operating voltages.

Abstract: A membrane electrochemical cell, in particular a fuel cell, of an improved type comprising a multiplicity of cell elements, each element made up of bipolar plates, current collectors, electrodes and membranes, wherein the function of electric current transmission through the cell elements, the release of heat towards the outside environment, the distribution of electric current to the electrodes and membranes, the removal of heat from the electrodes and membranes and the distribution of the reactants and products are performed by distinct components, in particular bipolar plates for the first two and porous electroconductive collectors for the others. The bipolar plates may have flat surfaces without grooves and are preferably manufactured with aluminum, titanium or alloys thereof, through cheap mass productions techniques; the bipolar plates are used together with collectors provided with deformability, residual resiliency and high porosity.

Abstract: The present invention is intended to prevent the formation of impurities such as chlorate in electrolysis using the ion exchange membrane method, without resorting to the addition of hydrochloric acid to counter the migration of alkali hydroxide from the cathode compartment to the anode compartment. The method of the present invention includes feeding a portion of an aqueous solution of an alkali chloride (as the raw material) into an auxiliary electrolytic cell of the cation exchange membrane type in which the anode is a hydrogen gas electrode, thereby effecting electrolysis to generate hydrochloric acid in the anode compartment, and then feeding the hydrochloric acid-containing aqueous solution of alkali chloride into the main electrolytic cell, thereby neutralizing the alkali hydroxide which migrates from the cathode compartment.

Abstract: A process for the electrolytic recovery of metals from solutions containing metal ions and fluorides and/or anionic flurocomplexes in diaphragmless cells wherein the deposition of the metals at the cathodes and the oxygen evolution at the anodes is effected, the improvement comprising the use of insoluble anodes made of sintered powders of doped tin dioxide optionally provided with coating of zirconyl phosphate and metal oxides which prevents the deposition of metal oxides on the anode surface and catalyze the oxygen evolution reaction.

Abstract: The underwater propulsion apparatus, which is mounted on a ship, has the anode and cathode electrodes including an anode compartment and cathode compartment whose electrode materials are separated from seawater in a central duct by the ion exchange membranes so that they are protected from poisoning by seawater. In the method utilizing the apparatus, the anode compartment and cathode compartment are supplied with moist hydrogen and moist oxygen, respectively, so as to substantially suppress the evolution of gas in the duct, which lowers the thrusting force.

Abstract: A shortcircuiting system, particularly useful for by-passing an electrolyzer in a multiplicity of monopolar or bipolar electrolyzers in an electrolysis circuit, said system comprising power supply means for feeding electrolysis current to said electrolyzers, a jumper switch means for by-passing said electrolyzer and means for controlling and interrupting the electric current supplied to said electrolyzers at least for a time sufficient to permit shortcircuiting of the electrolyzer to be by-passed without significantly affecting the operating conditions of said electrolyzers.

Abstract: In a process of chlor-alkali electrolysis carried out in a diaphragm cells comprising pairs of interleaved anodes and cathodes, the cathodes being provided with openings and coated with a porous diaphragm resistant to corrosion, at least part of the said anodes being provided with hydrodynamic circular to produce circulation of the anodic brine, the cell having inlets for feeding the fresh brine, and outlets for the removal of produced chlorine, hydrogen and caustic, the improvement comprising controlling the oxygen content in the chlorine and chlorate concentration in the caustic independently from the the fresh brine introduced and the concentration of the the brine by adding an aqueous solution of hydrochloric acid to the brine in the anodic compartment of the cell through a distributor positioned over the hydrodynamic circulator.

Abstract: A method for by-passing a monopolar electrolyzer out of a plurality of monopolar electrolyzers connected in series to an electrical power source, which electrolyzers consist of individual electrolysis cells each having anodic and cathodic contact points, using a jumper switch means comprising an internal circuitry and multiplicity of extension arms for connection to the electrolyzers immediately preceding and following the electrolyzer to be by-passed while preventing a shift in current through individual cells of the electrolyzers adjacent to the electrolyzer to be by-passed and to prevent damage to the electrolyzers by avoiding reversed current flow.

Abstract: The present invention relates to metal anodes for oxygen evolution from solutions containing fluorides or artionic fluorocomplexes such as tetrafluoroborates and hexafluorosilicates, the anodes having a metal substrate or matrix selected in the group comprising nickel-copper alloys with a copper content in the range of 2.5 and 30% by weight, tungsten or tantalum, niobium or titanium, combinations thereof or alloys of the same with palladium, nickel or yttrium. The anodes further comprise electrocatalytic compounds for oxygen evolution dispersed in the metal matrix. In the case of nickel- copper alloys, useful electrocatalytic compounds are cerium or tin dioxides, with suitable additives, while for tungsten, cobalt added with nickel, iron, copper or palladium may be used.

Abstract: An electric jumper switch means for electric current bypass of at least one electrolyzer consisting of individual electrolysis cells, out of a plurality of monopolar electrolyzers connected in series to an electrical power source characterized in that said jumper switch means comprises a multiplicity of first extension arms suitable for connection to the anodic contact point of each individual cell of the electrolyzer preceding the electrolyzer to be bypassed and a multiplicity of second extension arms suitable for connection to the cathodic contact point of each individual cell of the electrolyzer immediately following the electrolyzer to be bypassed, said jumper switch means comprising a resistor means to provide a uniform reduction of the current flow in the individual cells of the electrolyzer to be bypassed without a shift of electrical current in the adjacent cells of the electrolyzers immediately preceding and following the electrolyzer to be bypassed and a method of shutting down an electrolyzer in a

Abstract: Operation of diaphragm monopolar electrolyzers for chlor-alkali electrolysis is improved by providing at least part of the anodes in their upper portion with hydrodynamic baffles capable of generating a plurality of lifting and downcoming recirculation motions of the mixed anolyte-gas phase and of the anolyte separated from gas, respectively, which baffles are characterized by their superior edge or overflow holes located under the free surface of the anolyte, resulting in a reduction of the cell voltage and an increase in the faradic efficiency and the quality of the products.

Abstract: The present invention discloses a method for identifying defective ion exchange membranes installed in monopolar and/or bipolar electrolyzers for chlor-alkali production. The method of the present invention comprises reducing the electric load of the electrolyzer down to 2 to 10% of the normal load and under these reduced load conditions, a measurement of the single electric current load absorbed by each elementary cell in a monopolar electrolyzer is effected as well as the measurement of the single electric voltage of the elementary cell in the case of bipolar electrolyzers. The method further comprises calculating the deviations of the single current or voltages with respect to average values. All membranes which present values comprised between a determined threshold value are considered as suitable for operation.

Abstract: The invention is an electrode at least having a primary hydraulically permeable electrode member with a multiplicity of spaced apart depressions projecting a predetermined distance from the plane of the electrode. The invention also includes an electrolytic cell using the electrode and a method for electrolyzing an electrolyte using the cell.

Abstract: An apparatus for uniformly pressing a plurality of flat plate-type structures together comprising a first and second vertical support means, a pair of side rails spaced apart and supported on the support means, the side rails being perpendicular to the support means and adapted to support flat plate-like structures, a plurality of flat plate-like structures with hanger members to slidably and pivotably mount the structures on the side rails, a vertical mobile platen provided with top and bottom hanger members connected to a press means adapted for pressing the mobile platen against and toward the flat plate-type structures to compress them together and retracting the mobile platen from the plate-like structures, the press means comprising at least one coiled spring, a first contactor plate attached to the mobile platen and a second contactor plate attached to a positioning device secured to one of the support means and a first and second guide chamber for directing the positioning device and coiled spring per

Abstract: The present invention concerns electrodes for use in electrochemical processes, particularly as cathodes for hydrogen evolution in cells for the electrolysis of alkali metal halides, the electrodes comprising an electrocatalytic ceramic coating obtained by thermal deposition. Elements of the groups IB, IIB, IIIA, IVA, VA, V B; VI A; VI B and VIII are added to the solutions or dispersion of precursor compounds of electrocatalytic ceramic materials, the solutions or dispersions being thermally decomposed to obtain the coating.The surface of the doped coating thus obtained is substantially immune to poisoning by metal impurities, when the electrode according to the present invention is used as cathode in poisoned alkali solutions.