MXPA97008397A - Electrochemical conversion of hydrogenoanhydro halide to halogen gas using a transportation member cation - Google Patents

Abstract

The present invention relates to an electrochemical cell, system and process for converting essentially anhydrous hydrogen halide to essentially dry halogen gas. The process of the present invention is useful for converting anhydrous hydrogen halide, in particular, hydrogen chloride, hydrogen fluoride, hydrogen bromide and hydrogen iodide to a halogen gas, such as chlorine, fluorine, bromine or iodine. In particular, in the present invention, water is supplied to the cation transport membrane at the cathode in various forms. The present invention allows recovering a fluid released in the side or cathode side of the membrane and recycling the recovered fluid back to the side or cathode side of the membrane. In this way, the released, recovered fluid can be recycled to continuously supply water to the membrane, whereby the residual current density or limit of the cell is allowed to be increased and / or controlled

Description

ELECTROCHEMICAL CONVERSION. FROM HYDROGEN HALIDE ANHYDRO TO HALOGEN GAS USING A CATIONIC TRANSPORTATION MEMBRANE FIELD OF THE INVENTION The present invention relates to an electrochemical cell, system and process for converting essentially anhydrous hydrogen halide to essentially dry halogen gas. The process of the present invention is useful for converting anhydrous hydrogen halide, in particular, hydrogen chloride, hydrogen fluoride, hydrogen bromide and hydrogen iodide, to a halogen gas, such as chlorine, fluorine, bromine, or iodine. .

BACKGROUND OF THE INVENTION Hydrogen chloride (HCl) or hydrochloric acid is a reaction byproduct of many manufacturing processes which use chlorine. For example, chlorine is used to produce or manufacture polyvinyl chloride, isocyanates, and chlorinated hydrocarbons / fluorinated hydrocarbons, with hydrogen chloride as a byproduct of these processes. TO Ref .: 26039 cause that the supply exceeds the demand, the hydrogen chloride or the frequently produced acid can not be sold or used, even after careful purification. Shipping or boarding over long distances is not economically accessible. The discharge of chloride or acid ions into wastewater streams is environmentally unhealthy. Recovering and re-feeding the chloride to the manufacturing or production process is the most desirable route for handling the HCl by-product. A number of commercial processes have been developed to convert HCl into usable chlorine gas. See, for example, F. R. Minz, "HC1-Electrolysis - Technology for Recycling Chiorine", Bayer AG, Conference on Electrochemical Processing, Innovation & Progress, Glasgow, Scotland, UK, 4 / 21-4 / 23, 1993. Commonly, there are thermal catalytic oxidation processes to convert anhydrous HCl and aqueous HCl into chlorine. Commercial processes, known as the "Shell-Chlor" process, the "Kel-Chlor" process and the MT-Chlor process, are based on Deacon's reaction.The original Deacon reaction was developed in the 1870s using a fluidized bed containing a copper chloride salt which acts as the catalyst The Deacon reaction is generally expressed as follows: Catalyst 4 HC1 + 02 2C12 + 2 H20 (1) where the following catalysts can be used, depending on the reaction or process in which equation (1) is used. Catalyst Reaction or Process Cu Deacon Cu, Rare Earth, Alkali Shell-Chlor N02, NOHS04 Kel-Chlor CrmOn MT-Chlor Commercial improvements to the Deacon reaction have used other catalysts in addition to or in place of the copper used in the Deacon reaction, such as rare earth compounds, various forms of nitrogen oxide, and chromium oxide, to improve the conversion rate , to reduce the input of energy and to reduce the corrosive effects on the processing equipment produced by rigorous chemical reaction conditions. However, in general these thermal catalytic oxidation processes are complicated because they require separating the different reaction components to achieve purity in the product. They also involve the production of highly corrosive intermediaries, which need expensive construction materials for the reaction systems. In addition, these thermal catalytic oxidation processes are operated at elevated temperatures of 250 ° C and above. Electrochemical processes exist to convert aqueous HCl to chlorine gas by passing direct electric current through the solution. The common electrochemical commercial process is known as the Uhde process. In the Uhde process, the approximately 22% aqueous HCl solution is fed from 65 ° to 80 ° C to both compartments of an electrochemical cell, where exposure to a direct current in the cell results in an electrochemical reaction and a decrease in HCl concentration to 17% with the production of chlorine gas and hydrogen gas. A polymeric separator divides the two compartments. The process requires the recirculation of the diluted HCl solution (17%) produced during the electrolysis step and regenerating a 22% HCl solution to feed the electrochemical cell. The complete reaction of the Uhde process is expressed by the equation: Electric Power 2HC1 (aqueous) - "* • H2 (wet) + Cl2 (hiii-iedo) (2) As is evident from equation (2), the chlorine gas produced by the Uhde process is wetted or moistened, usually It contains approximately 1% to 2% water. This wet chlorine gas must then be further processed to produce a usable, dry gas. If the concentration of HCl in the water becomes so low, it is possible that the oxygen will be generated from the water present in the process of Uhde This possible secondary or parasite reaction of the Uhde process due to the presence of water is expressed by the equation: 2H20 > Oz + 4H + 4e ~ (3) In addition, the presence of water in the Uhde system limits the densities of the current at which the cells can be made at less than 500 amps. / pie2, because of this secondary or parasitic reaction. The secondary or parasitic reaction results in reduced electrical efficiency and corrosion of the cell components.

Another electrochemical process for processing aqueous HCl has been described in U.S. Patent No. 4,311,568 to Balko. Balko uses an electrolytic cell that has a solid polymer electrolyte membrane. Hydrogen chloride, in the form of hydrogen ions and chlorine ions in aqueous solution, is introduced into an electrolytic cell. The solid polymer electrolytic membrane is attached to the anode to allow the transport of the anode surface to the membrane. In Balko, controlling and minimizing the secondary or parasitic reaction of evolution of oxygen is an important consideration. The evaluation of oxygen decreases the efficiency of the cell and leads to rapid corrosion of cell components. The design and configuration of the pore size of the anode and the thickness of the electrode employed by Balko minimize the transport of the chlorine ions. This results in the evolution of effective chlorine while minimizing the evolution of oxygen, since the evolution of oxygen tends to increase under conditions of depletion or depletion of the chlorine ion near the surface of the anode. In Balko, although the evolution of oxygen can be minimized, it is not eliminated. As can be seen from Figures 3 to 5 of Balko, when the total current density increases, the speed of oxygen evolution increases, as is evident from the increase in the concentration of oxygen found in the chlorine produced . Balko can act or reach higher current densities, but is limited by the detrimental effects of oxygen evolution. If Balko's cell were to operate at high current densities, the anode could be destroyed. The conductivity of a membrane is directly related to the water content in the membrane and describes in low water content. The density of the residual current occurs when the concentration of water inside the membrane reaches a value that does not support it plus the conduction of additional protons. Therefore, the residual current density can develop when the conductivity decreases due to low water concentrations. When a cell is operated before the residual current, the components of the cell can be destroyed. The existing electrochemical processes for converting hydrogen halides as described above, are aqueous processes which require first dissolving the hydrogen halide in water. Since these electrochemical cells have water in their anolytes and catholytes, the membranes of such cells are normally kept hydrated. There is a need to directly produce essentially dry halogen gas without first having to dissolve the hydrogen halide in water, and to keep the membrane hydrated during such a process. This will allow the residual current density or limit of the cell to be increased and / or controlled, so that the components of the cell could not be destroyed.

BRIEF DESCRIPTION OF THE INVENTION The present invention solves the problems of the prior art by providing an electrochemical cell, system and process for directly producing essentially dry halogen gas from the essentially anhydrous hydrogen halide.

This cell, system and process allows the direct processing of the anhydrous hydrogen halide which is a by-product of the manufacturing or production processes, without first dissolving the hydrogen halide in water. This direct production of essentially dry halogen gas, when given, for example, for chlorine gas, is less intense in investment than the processes of the prior art, which require the separation of water from the chlorine gas. This direct production of essentially dry halogen gas also requires lower investment costs than the electrochemical conversions of hydrogen chloride of the prior art. This advantage can be translated directly into lower energy costs per pound of broth, chlorine, generated than in the aqueous electrochemical processes of the prior art. The direct production of essentially dry halogen gas also provides a process which produces drier chlorine gas with some processing steps as compared to that produced by prior art electrochemical or catalytic systems, whereby the processing conditions of simplify and reduce investment expenses. In the anhydrous cell, system and process of the present invention, the membrane is kept hydrated. This allows the residual current density of the cell to be increased, as well as controlled. This, in turn, allows an electrochemical cell to be designed in which a measurable component, such as the cation exchange membrane, is produced from prolonged exposure to excessive current, which could deteriorate the membrane, and thus impact in the long-term functioning of the membrane and the cell. In addition, control of the waste stream is especially desirable where it is necessary to compensate for changes in the manufacturing or production rates of suppliers or suppliers of the anhydrous hydrogen halide, such as hydrogen chloride. In accordance with the present invention, the membrane of an electrochemical cell used to convert essentially anhydrous hydrogen halide to essentially dry halogen gas is kept hydrated in a variety of ways. The advantages achieved in maintaining the membrane hydrated by these various forms make the process of the present invention even more practicable and economically more attractive. In a particular embodiment of the present invention, the membrane is kept hydrated by an oxygen supply, which provides an excess of oxygen to the cell. This increases the conversion rate of protons transported through the membrane and the oxygen supplied to the water, which allows the residual current density to be increased. Furthermore, with this oxygen supply, it is possible to take advantage of this excess of oxygen without the economic penalty of cell discharge products associated with other form of membrane hydration. In order to achieve the solutions mentioned above, and in accordance with the purposes of the invention when taken up and described broadly herein, an electrochemical cell is provided to directly produce essentially dry halogen gas from essentially anhydrous hydrogen halide. The electrochemical cell comprises means for oxidizing essentially anhydrous hydrogen halide molecules to produce essentially dry halogen gas and protons, cation transporting means for transporting the protons therethrough, wherein the oxidation means are contacted with one side of the cation transport means, means for reducing transported protons, wherein the reducing or reducing means is disposed in contact with the other side of the cation transport means, and means for supplying water to the cation transport means on the other side of the cation transport medium. Further in accordance with the purposes of the invention, a system is provided for directly producing essentially dry halogen gas from essentially anhydrous hydrogen halide. The electrochemical cell comprises means for oxidizing essentially anhydrous hydrogen halide molecules to produce essentially dry halogen gas and protons; cation transport means for transporting the protons therethrough, wherein the oxidation means are brought into contact on one hand with the cation transport means; means for reducing the transported protons, wherein the reduction means are brought into contact with the other side of the cation transport means, and means of input to supply water to the cation transport means to the other side of the means of transport of cations; reduction; inlet means for supplying water to the cation transport means on the other side of the cation transport means, outlet means for releasing a fluid from the reducing means on the other side of the cation transport means; and means for recirculating the fluid returned to the cation transport means to the other side of the cation transport means. Further, in accordance with the purposes of the invention, a process is provided for directly producing essentially dry halogen gas from essentially anhydrous hydrogen halide, wherein the essentially anhydrous hydrogen halide molecules are fed to an inlet of the cell. electrochemistry and are transported to an anode in the cell; the essentially anhydrous hydrogen halide molecules are oxidized at the anode to produce essentially dry hydrogen gas and protons; the protons are transported through a cation transport membrane of the cell; transported protons are reduced to a cathode of the electrochemical cell; and a stream of humidified gas is supplied to the membrane. Alternatively, the process of the present invention can be described as a process for directly producing essentially dry halogen gas from essentially anhydrous hydrogen halide, wherein the stream is supplied to an electrochemical cell; Essentially anhydrous hydrogen halide molecules are fed to an inlet of the electrochemical cell and transported to an anode in the cell; the essentially anhydrous hydrogen halide molecules are oxidized at the anode to produce essentially dry halogen gas and protons; the protons are transported through a membrane of cation transport of the cell; transported protons are reduced to a cathode of the electrochemical cell; the water is supplied to the membrane at the cathode and the water is transported by diffusion to the anode; the transported protons resist the water present in the membrane towards the cathode; and the amount of current required to achieve a balance between water carried by diffusion to the anode and entrained by proton transport to the cathode is controlled by adjusting or regulating the amount of water supplied to the membrane at the cathode. In either process, a fluid is released from the cell and can be recirculated back to the membrane.BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of an electrochemical cell for producing halogen gas from anhydrous hydrogen halide according to any of the first, second, third or fourth embodiments of the present invention. Figure IA is a top cross-sectional view, in section, of the mass flow fields of the anode and cathode as shown in Figure 1.

Figure 2 is a schematic diagram of a system for producing essentially dry halogen gas from anhydrous hydrogen halide using the electrochemical cell of Figure 1 and for recirculating a fluid released from the cell back to the membrane, where add liquid water to the side entrance of the cathode in the cell. Figure 3 is a schematic diagram of a system for producing essentially dry halogen gas from anhydrous hydrogen halide using the electrochemical cell of Figure 1 and for recirculating a fluid released from the cell back to the membrane, wherein a humidified gas stream comprising hydrogen is added to the side entrance of the cathode of the cell. Figure 4 is a schematic diagram of a system for producing essentially dry halogen gas from anhydrous hydrogen halide using the electrochemical cell of Figure 1 and recirculating a fluid released from the cell back to the membrane, where a stream of Humidified gas comprising oxygen is added to the input side of the cathode of the cell, Figure 5 is a schematic diagram of a system for producing essentially dry halogen gas from anhydrous hydrogen halide using the electrochemical cell of Figure 1 and for recirculating a fluid released from the cell back to the membrane, where a stream of humidified gas comprising oxygen is added to the lateral inlet of the cathode of the cell.

DESCRIPTION OF THE PREFERRED MODALITIES Reference is now made in detail to the present preferred embodiments of the invention as illustrated in the accompanying drawings. According to a first, second, third and fourth embodiment of the present invention, an electrochemical cell is provided for the direct production of essentially dry halogen gas from the anhydrous hydrogen halide. This cell is generally shown at 10 in Figure 1. The cell of the present invention will be described with respect to a preferred embodiment of the present invention, which directly produces essentially dry chlorine gas from anhydrous hydrogen chloride. Alternatively this cell can be used to produce other halogen gases, such as bromine, fluorine and iodine from a respective anhydrous hydrogen halide, such as hydrogen bromide, hydrogen fluoride and hydrogen iodide. The term "direct" means that the electrochemical cell eliminates the need to remove water from the hydrogen gas produced or the need to convert essentially anhydrous hydrogen halide to aqueous hydrogen halide prior to the electrochemical treatment. In the first mode, the chlorine gas, as well as hydrogen, is produced in this cell. In a second embodiment, water, as well as chlorine gas, are produced by this cell, as will be explained more fully below. The electrochemical cell of the first to fourth embodiments comprises means for oxidizing essentially anhydrous hydrogen halide molecules to produce essentially dry halogen gas and protons. The oxidation means is an electrode, or more specifically, an anode 12 as shown in Figure 1. On the side or side of the anode, the electrochemical cell 10 has a lateral inlet of the anode 14 and a lateral outlet of the anode 16. Since in the preferred embodiment, the anhydrous HCl is carried through the inlet, and the chlorine gas is transported through the outlet, the inlet and outlet can be joined with a perfluoropolymer, sold as TEFLON® PFA (later referred to as "TEFLON® PFA") by E. I. du Pont de Nemours and Company of Wilmington, Delaware (later referred to as "DuPont"). The electrochemical cell of the first to the fourth embodiment also comprises means of transporting the cation to transport the protons therethrough, where one side or side of the oxidation means is placed in contact with a side or side of the cation transport medium. Preferably, the cation transport medium is a cation transport membrane 18 as shown in Figure 1. More particularly, the membrane 18 can be a proton-conducting membrane. The membrane 18 can be a commercial cationic membrane made of a fluoro- or perfluoropolymer, preferably a copolymer of two or more fluoro or perfluoromonomers, at least one of which has pendant or sulfonic acid groups. The presence of carboxylic groups is not desirable, because those groups tend to decrease the conductivity of the membrane when they are protonated. Various suitable resin materials are commercially available or may be made in accordance with the patent literature. They include fluorinated polymers with side chains of the type -CF2CFRS03H and -0CF2CF2CF2S03H, where R is an F, Cl, CF2C1, or a perfluoroalkyl radical of Ci to Cio. The membrane resin can be, for example, a tetrafluoroethylene copolymer with CF2 = CFOCF2CF (CF3) OCF2CF2S03H. Sometimes those resins may be in the form that the pendant or pendant -S02F groups have, rather than the -S03H groups. The sulfonyl fluoride groups can be hydrolyzed with potassium hydroxide to -S03K groups, which are then exchanged with an acid to -S03H groups. Suitable cationic membranes, which are made of polytetrafluoroethylene copolymers, hydrated, and pendant or pendant sulfonic acid groups containing polysulfonyl fluoride vinyl ether, are offered by DuPont under the trademark "NAFION" (hereinafter referred to as NAFION®) . In particular, the membranes of NAFION® containing pendant sulfonic acid groups include NAFION® 117, NAFION® 324 and NAFION® 417. The first type of NAFION® is not supported and has an equivalent weight of 1100 g., Equivalent weight that it is defined as the amount of resin required to neutralize one liter of a 1M sodium hydroxide solution. The other two types of NAFION® are both supported in a fluorocarbon factory, the equivalent weight of NAFION® 417 is also 1100 g. The NAFION® 324 has a two-layer structure, a 125 μm membrane having an equivalent weight of 1100 g., And a 25 μm thick membrane having an equivalent weight of 1500 g. A class of NAFION® 117F is also offered, which is a precursor membrane having groups of -S02F that can be converted to sulfonic acid groups. Although the present invention describes the use of a solid polymer electrolyte membrane, it is within the scope of the invention to use other cation transporting membranes which are non-polymeric. For example, proton conductive ceramics such as beta-alumina can be used. Beta-alumina is a class of non-stoichiometric crystalline compounds that have the general structure Na2Ox "Al203, in which x varies from 5 (ß" -alumin) to 11 (ß-alumina). This material and a number of solid electrolytes which are useful for the invention are described in the Fuel Cell Handbook, A. J. Appleby and F. R. Foulkes, Van Nostrand Reinhold, N. Y., 1989, pages 308-312. Additional useful solid-state proton conductors, especially strontium and barium cerates, such as strontium ketoerypt (SrCe0.95Yb0.o5? 3-a) and barium cerate neodymium (BaCe0.9Nd0.o? 03-a) are described in the final report, DOE / MC / 24218-2957, Jewulski, Osif and Remick, prepared by the US Department of Energy., Office of Fossil Energy, Morgantown Energy Technology Center by Institute of Gas Technology, Chicago, Illinois, December, 1990. The electrochemical cell of the first to the fourth modalities also comprises an electrode, or more specifically, cathode 20, where the The cathode is brought into contact with the other side or side (as opposed to the side that is in contact with the anode) of the membrane 18 as illustrated in Figure 1. The cathode 20 has a side entrance of the cathode 24 and an outlet 26. side of the cathode as shown in Figure 1. Since in the preferred embodiment, the anhydrous HCl is processed, and since some chlorides pass through the membrane and consequently, the HCl is present on the cathode side of the cell , the cathode input and output can be linked with TEFLON® PFA. As is known to one skilled in the art, if electrodes are placed on opposite surfaces of the membrane, the cationic charges (protons in the HCl reaction are described) are transported through the anode membrane to the cathode, while each electrode performs a half cell reaction In the first and second embodiments, the anhydrous hydrogen chloride molecules are transported to the anode surface through a lateral inlet of the anode 14. The anhydrous hydrogen chloride molecules are oxidized to produce essentially dry chlorine gas and protons. The essentially dry chlorine gas exits through the anode side outlet 16 as shown in Figure 1. The protons, H +, are transported through the membrane and reduced at the cathode. This is explained in more detail later. The anode and the cathode may comprise porous gas diffusion electrodes. Such electrodes provide the advantage of highly specific surface area, as is known to the person skilled in the art. The anode and the cathode comprise an adjacent electrochemically active material disposed on or below the surface of the cation transport membrane. A thin film of the electrochemically active material can be applied directly to the membrane. Alternatively, the electrochemically active material can be hot pressed to the membrane, as shown in A. J. Appleby and E. B. Yeager, Energy, vol. 11, 137 (1986). Alternatively, the electrochemically active material can be deposited on the membrane, as shown in U.S. Patent No. 4,959,132 to Fedkiw. The electrochemically active material can comprise any type of catalytic or metallic material or metal oxide, while the material can withstand charge transfer. Preferably, the electrochemically active material can comprise a catalytic material such as platinum, ruthenium, osmium, rhenium, rhodium, iridium, palladium, gold, titanium, or zirconium, and the oxides, alloys or mixtures thereof. However, in general, the oxides of these materials are not used for the cathode. Other catalytic materials suitable for use with the present invention may include, but are not limited to, macro transition metal cycles in monomeric and polymeric forms and transition metal oxides, including perovskites and pyrocoras. In a hot press or electrode, the electrochemically active material may comprise a catalytic material on a support material. The support material may comprise carbon particles and polytetrafluoroethylene particles, which is sold under the trademark "TEFLON" (hereinafter referred to as TEFLON®) commercially available from DuPont. The electrochemically active material can be bonded by virtue of the TEFLON® to a support structure, or gas diffusion layer, of carbon paper or graphite cloth and pressed or hot pressed to the cation transport membrane. The hydrophobic nature of TEFLON® does not allow a water film to form at the anode. A water barrier at the electrode could interfere with the diffusion of HCl to the reaction sites. Preferably the electrodes are thermopressed in the membrane to have good contact between the catalyst and the membrane. The charges of electrochemically active material may vary based on the method of application to the membrane. Thermopressed gas diffusion electrodes, typically have loads of 0.10 to 0.50 mg / cm2. Lower loads are possible with other available methods of deposition, such as distributing them as thin films of inks in the membranes, as described in Wilson and Gottesfeld. "High Performance Catalyzed Membranes of Ultra-low Pt Loadings for Polymer Electrolyte Fuel Cells", Los Alamos National Laboratory, J. Electrochem. Soc, Vol. 139, No. 2 L28-30, 1992, where the inks contain solubilized NAFION® ionomer to improve contact of the catalyst-ionomer surface and act as a binder to the NAFION® membrane sheet. With a system, loads as low as 0.017 mg of active material per cm2 have been reached. The membrane of the present invention serves as the electrolyte in which the protons constitute the current. The membrane must be in a state of sufficient hydration to act as a proton conduit. Electro-osmotic entrainment occurs in the membrane, where protons drag water in the direction of current flow. This leads to the development of a water concentration gradient inside the membrane. The conductivity of a membrane is directly related to the water content in the membrane and decreases at low water content. The residual or limit current occurs when the concentration of water within the membrane reaches a value that will not support the longer proton conduction. Thus, the residual current density can develop when the conductivity decreases due to low water concentrations. Therefore, in accordance with the present invention, water, in the form of a stream of humidified gas or liquid water, is supplied to the membrane at the cathode. This is necessary to achieve efficient proton transport. In the first three modes, which have a hydrogen-producing cathode, the hydration of the membrane is completed or carried out by the introduction of either liquid water in the first mode, or gas stream comprising hydrogen or nitrogen, respectively, in the second and third modes, to the membrane on the side of the cathode of the membrane. In the fourth embodiment, which has a water producing cathode, the hydration of the membrane is carried out by the production of water at the cathode, as well as the introduction of a humidified gas stream comprising oxygen at the side of the cathode of the membrane, which produces water. Although disclosed herein, hydrogen, nitrogen and oxygen, humidified gas streams comprising other gases are within the scope of the present invention. The water on the side of the cathode of the membrane is transported by diffusion to the anode. Additionally, transported protons entrain water in the membrane, which includes water already present in the membrane first, towards the cathode. Applicants have found that the amount of current required to achieve a balance between the water transported by diffusion to the anode and dragged by the transport of protons to the cathode, at this point the residual or limit current occurs, can be controlled by adjusting the quantity of water supplied to the membrane at the cathode. Accordingly, with the present invention, the residual or limit current can be controlled. This is especially desirable where it is necessary to decrease or increase the residual current to compensate for changes in the amount of anhydrous hydrogen halide which needs to be processed. This may change in response to changes in the production or manufacturing speeds of manufacturers that produce hydrogen chloride. To adjust the amount of water supplied to the membrane, the electrochemical cell of the first to fourth embodiments also comprises input means for supplying water to the cation transport means on the other side of the cation transport means. Preferably, the input means comprises a lateral or secondary input of the cathode 24 as shown in Figure 1 which supplies water, in various ways as will be explained later, to the side of the membrane which is brought into contact with the cathode. The electrochemical cell also comprises exit means for releasing a fluid from the reducing means on the other side of the cation transport means.

Preferably, the exit means comprises a lateral or secondary cathode outlet 26 as shown in Figure 1, which releases a cathode fluid to the side of the membrane that contacts the cathode. Since in the preferred embodiment, the anhydrous HCl is processed, and since some chloride can be passed through the membrane to the side of the cathode of the cell, the lateral entrance of the cathode and outlet is preferably coated with TEFLON® PFA. The electrochemical cell of the first to the fourth embodiment further comprises an anode flow field 28 disposed in contact with the anode and a cathode flow field 30 disposed in contact with the cathode. The flow fields are electrically conductive, and act as both current and mass flow fields. More specifically, the mass flow fields may include a plurality of anode flow channels 29 and a plurality of cathode flow channels 31 as shown in Figure IA. The anode flow field and channels 29 direct reagents, such as anhydrous HCl, and products, such as essentially dry chlorine gas, from the anode. The flow field of the cathode 30 and channels 31 direct the catholyte, such as liquid water in the first mode, or a humidified gas stream in the second to fourth modes, to the cathode, and products, such as hydrogen vapor, liquid water and HCl dissolved in water in the first mode, hydrogen and hydrogen halide, in the vapor form, in the second mode, hydrogen, nitrogen, water and hydrogen halide, all in the form of vapor, in the third embodiment, and oxygen, water and hydrogen halide, all in the form of vapor, in the fourth mode. The anode and the mass flow fields of the cathode may comprise fluted porous graphite paper. The flow fields can also be made of a porous carbon in the form of a foam, cloth or weft. The electrochemical cell of the first to the fourth embodiment may also comprise an anode mass flow collector 32 and a cathode mass flow field collector 34 as shown in Figure 1. The purpose of such collectors or pipes is bring the anolyte to products from the anode, and catholyte to products from the cathode. In addition, the pipes or collectors form a framework around the anodic mass flow field and the anode, and the cathodic mass flux field and the cathode, respectively. These pipes are preferably made of a corrosion resistant material, such as TEFLON® PFA. A plug or seal 36, 38 also contributes to forming a framework around the respective mass flow fields of the cathode and anode. Also these seals are preferably made of a corrosion resistant material, such as polytetrafluoroethylene, sold under the trademark TEFLON® PTFE by DuPont. The electrochemical cell of the first to fourth embodiments also comprises an anode current distribution bar 46 and a cathodic current distribution bar 48 as shown in Figure 1. The transports or current distribution bars conduct the current to and from a voltage source (not shown). Specifically, the anodic current bus 46 is connected to the positive terminal of a voltage source, and a bus or distribution bus 48 of the cathode is connected to the negative terminal of the voltage source, so that when the voltage is supplied to the cell, the current flows through all the components of the cell to the right of the current distribution bar 46 as shown in Figure 1, including the current distribution bar 48, from which it is returned to the voltage source. The3 busbars are made of a conductive material, such as copper. The electrochemical cells of the first and second embodiments also comprise a respective current distributor arranged in contact with a respective flow field. An anode current distributor 40 is arranged in contact with the flow field of the anode 28and a cathodic current distributor 42 is arranged in contact with the flow field of the cathode 30. The anodic current distributor collects or picks up current from the anode busbar and distributes it to the anode by electronic conduction. The cathodic current distributor collects cathodic current and distributes it to the cathode distribution bar. The anodic and cathode current distributors preferably each comprise a non-porous layer. The anodic current distributor provides a barrier between the anodic current distribution bar and the anode, as well as between the current distributing bus and the anhydrous hydrogen halide, such as hydrogen chloride, and the halogen gas, such as chloride. The cathodic current distributor provides a barrier between the cathodic current distribution bar and the cathode, as well as between the cathodic current distribution bar and the hydrogen halide. The barrier is desirable, when there is some migration of the hydrogen halide through the membrane. The current distributors of the present invention can be made from a variety of materials, and the material used for the anode current distributor needs not to be the same as the material used for the cathodic current distributor. In one instance, the anodic current distributor is made of platinized tantalum, and the cathodic current distributor is made of a nickel-based alloy, such as UNS10665, sold as HASTELLOY® B-2, by Haynes, International. In the first to the fourth embodiment, the electrochemical cell also comprises a structural support 44 arranged in contact with the anodic current distributor 40. The support on the side of the anode is preferably made of UNS31603 (316L stainless steel). A seal 45, preferably in the form of an O-ring made of a perfluoroelastomer, sold under the trademark KALREZ® of DuPont, is placed between the structural support 44 on the side of the anode and the anodic current distributor 40. The The cathodic current distributor acts as a structural support piece resistant to corrosion on the side of the cathode. This piece can be perforated and tapered to accept the adjustment of the TEFLON® PFA, which is used for the entry and exit. When more than one anode-cathode pair is used as in manufacturing, a bipolar array, so familiar to one skilled in the art, is preferred. The electrochemical cell of the present invention can be used in a bipolar cell. To create such a bipolar battery, the current distributors 40 and 42 and all the elements arranged in the middle as shown in Figure 1 are repeated along the length of the cell, and the current distribution bars are placed in the outside of the pile. In any of the first to fourth modes, the electrochemical cell can be operated over a wide range of temperatures. The operation at room temperature is an advantage, due to the ease of use of the cell. However, operation at elevated temperatures provides the advantages of increased electrolytic conductivity and improved kinetics. In addition, it should be noted that anyone is not restricted to operate the electrochemical cell of any of the first to fourth modes, at atmospheric pressure. The cell could operate at differential pressure gradients, which change the transport characteristics of water or other components in the cell, including the membrane. The electrochemical cell of any embodiment of the present invention can be operated at temperatures above a given pressure than the electrochemical cells operated with aqueous hydrogen chloride of the prior art. This affects the kinetics of the reactions and the conductivity of the NAFION®. Higher temperatures result in lower cell voltages. Nevertheless, limits in temperature occur because of the properties of the materials used for elements of the cell. For example, the properties of a NAFION® membrane change when the cell is operated above 120 ° C. The properties of a polymer electrolytic membrane make it difficult to operate a cell at temperatures above 159 ° C. With a membrane made of other materials, such as a ceramic material similar to beta-alumina, it is possible to operate a cell at temperatures above 200 ° C. Further in accordance with the first embodiment of the present invention, there is provided a system and a process for recirculating a fluid released from an electrochemical cell used for the direct production of essentially dry halogen gas from essentially anhydrous hydrogen halide. The system of the first embodiment is shown in Figure 2 and comprises an electrochemical cell 10, which is the same as the electrochemical cell 10 as described above. In the first embodiment, the liquid water is fed to the lateral inlet of cathodes 24 as shown in Figure 1, and subsequently to the side of the cathode of the membrane. The side outlet of the cathode 26 releases a fluid, which in the first embodiment comprises water (H20) in the form of a liquid, hydrogen (H2) in the form of a vapor, and hydrogen halide, such as hydrogen chloride , which dissolves in water. The system for directly producing essentially dry halogen gas from essentially anhydrous hydrogen halide further comprises means for recirculating the released fluid back to the cation transport medium. More specifically, the recirculation means comprises a recirculation circuit which recirculates the released fluid back to the membrane next to the cathode of the membrane. The recirculation means may comprise a cooler for cooling the released fluid. As shown in Figure 2, hydrogen (H2) in the form of a vapor, water (H20) in the form of a liquid, and a hydrogen halide, such as hydrogen chloride, which dissolves in water, which has been released from the cell, are transported through line 50 to a cooler 52 which cools the fluid released. The recirculation medium may also comprise a separator for removing a portion of the hydrogen halide from the released fluid. As shown in Figure 2, after the released fluid is cooled, transported or carried through a line 54 to a separator 56, which removes a portion of the hydrogen chloride dissolved in water (H20) through a line 70 as shown in Figure 2. The recirculation medium may further comprise a scrubber or cleaner to remove another portion of the hydrogen halide. Specifically, hydrogen (H2), hydrogen chloride (HCl) and water (H20), all in the vapor form, are transported through a line 60 to a scrubber or cleaner 62. An alkaline solution is added to the scrubber or gas scrubber 62 through line 64, so that the scrubber or scrubber removes the other portion of the hydrogen chloride through a line 68, such as an alkaline halide salt. The hydrogen (H2) and water (H20) both in the vapor form, which can be discharged or used in another process, are vented from the scrubber or cleaner 62 through line 66. In the first embodiment of Figure 2 , the recirculation means also comprises a pump for pumping the fluid released through the recirculation circuit back to the membrane. As shown in Figure 2, liquid water (H20) and hydrogen chloride (HCl), dissolved in water, are transported or conducted through line 70 to a pump 72. Water and hydrogen chloride then they are conveyed or transported out of the pump 72 through line 74. The recirculation means of the first mode may also comprise a temperature regulator or timer, shown as a heater / cooler 80 in Figure 2., which tempers or regulates the temperature of the released fluid. The temperature regulator 80 can heat or cool the released fluid, depending on the desired temperature for the electrochemical cell. The recirculation means of the first embodiment may additionally comprise an air conditioner 78 for conditioning or conditioning the released fluid. Conditioner 78 supplies heat and water through a line 77 to the released fluid. The liquid water (H20), with a small amount of residual hydrochloric acid, is conducted or transported through a line 82 back to the electrochemical cell 10, where it is used to continuously supply liquid water to the membrane. Further in accordance with the second embodiment of the present invention, there is provided a system and a process for recirculating a gas stream from an electrochemical cell used for the direct production of an essentially dry halogen gas from an essentially anhydrous hydrogen halide. . The system of the second embodiment is shown in Figure 3 and comprises an electrochemical cell 10 ', which is the same as the electrochemical cell 10 as described above. In the second embodiment, a humidified gas stream comprising hydrogen is fed to a cathode side inlet 24 of the cell as shown in Figure 1. The humidified gas stream comprises primarily hydrogen. However, in practice, traces of other gases, except oxygen, can be included in the gas stream of the second embodiment. The lateral outlet of the cathode 26 as shown in Figure 1 releases a fluid from the cathode, which in the second embodiment comprises water (H20), hydrogen (H2), and hydrogen halide, such as HCl, all in the form steam.

The system for directly producing essentially dry halogen gas from essentially anhydrous hydrogen halide of the second embodiment also comprises means for recirculating the released fluid back to the cation transport medium. More specifically, the recirculation means comprise a recirculation circuit which recirculates the fluid released back to the membrane on the side of the cathode of the membrane. The recirculation means of the second embodiment may comprise a cooler for cooling the released fluid. As shown in Figure 3, water (H20), hydrogen (H2) and hydrogen halide, all in the form of vapor, are transported or carried through a line 50 'to a cooler 52' which cools the fluid released. As noted above, the released fluid comprises hydrogen halide, specifically hydrogen chloride in a preferred embodiment, and the recirculation medium can also comprise a separator for removing a portion of the hydrogen halide from the released fluid. As shown in Figure 3, after the released fluid is cooled, it is transported through line 54 'to a separator 56', which removes a portion of the hydrogen chloride, as well as water vapor, through of line 70 'as shown in Figure 3. This HCl and water are discharged. The recirculation medium may further comprise a scrubber or cleaner to remove another portion of the hydrogen halide. Specifically, hydrogen (H2), hydrogen chloride (HCl) and water (H20), all in the vapor form, are transported through a 60 'line to a scrubber or cleaner 62'. An alkaline solution is added to the scrubber or cleaner 62 'through a line 64', so that the scrubber or scrubber removes another portion of the hydrogen chloride through line 68 ', such as an alkaline halide salt. Hydrogen vapor (H2) and water vapor (H20), which can be discharged or used in another process, are vented from the scrubber or cleaner 62 'via line 66'. Hydrogen vapor (H2) and water vapor (H20) are transported or carried away from the scrubber or cleaner 62 'via line 67'. In the second embodiment of Figure 3, the recirculation means may also comprise a humidifier for humidifying or wetting the released fluid. A humidifier 65 'humidifies the released fluid, which is hydrogen vapor and water vapor, with water, in either the liquid or vapor form, through the line 69'. The humidified hydrogen and water vapor are taken out of line 69 'by line 71'. The recirculation means may also comprise a compressor 72'to compress the released fluid. Then water and hydrogen are transported out or carried out from the compressor 72 'through line 74'. The recirculation means of the second embodiment may also comprise a hardener, shown as a heater / cooler 80 'in Figure 2, which tempers or regulates the temperature of the released fluid. The temperature regulator or hardener 80 'can heat or cool the released fluid, depending on the desired temperature of the cell. The water and hydrogen vapor are then transported through a line 76 '. The recirculating means of the second embodiment may additionally comprise an air conditioner 78 'for conditioning, or supplying heat and water, to the released fluid, which is still steam of hydrogen and water vapor, through the line 77". In the second mode, either a humidifier or an air conditioner are used, but not both. Hydrogen and water vapor are carried through line 82 'back to electrochemical cell 10', where they are used to continuously supply a stream of humidified gas, which includes hydrogen, to the membrane.

Further in accordance with the third embodiment of the present invention, there is provided a system and a process for recirculating a gas stream from an electrochemical cell used for the direct production of essentially dry halogen gas from essentially anhydrous hydrogen halide. The system of the third embodiment is shown in Figure 4 and comprises an electrochemical cell 10 '', which is the same as the electrochemical cell 10 described above. In the third embodiment, a humidified or humidified gas stream comprising nitrogen is fed to the lateral cathode inlet 24 as shown in Figure 1. The humidified gas comprises mainly nitrogen. However, in practice, traces of other gases other than oxygen can be included in the gas stream. The outlet from the side of the cathode 26 as shown in Figure 1 releases or releases a fluid from the cathode through the line 50", which in the third embodiment comprises nitrogen (N2), hydrogen (H2), water ( H20), and hydrogen halide, such as hydrogen chloride (HCl), all in the vapor form, as shown in Figure 4.

The system for directly producing essentially dry halogen gas from essentially anhydrous hydrogen halide of the third embodiment also comprises means for recirculating the released fluid back to the cation transport medium. More specifically, the recirculation means comprises a recirculation circuit which recirculates the released fluid back to the membrane on the side of the cathode of the membrane. The recirculation means of the third embodiment may comprise a cooler for cooling the released fluid. As shown in Figure 4, water (H20), nitrogen (N2), hydrogen (H2) and halide of hydrogen, such as HCl, all in the form of a vapor, are transported or conducted through a line 50. '' to a cooler 52 '' which cools the fluid released or discharged. As noted above, the discharged released fluid comprises hydrogen halide, specifically hydrogen chloride in a preferred embodiment, and the recirculation medium also comprises a separator for removing a portion of the hydrogen halide from the released fluid. As shown in Figure 4, after the released or discharged fluid is cooled, transported or conducted through a line 54"to a separator 56", which removes a portion of the hydrogen chloride and water (H20) in the form of liquid through a line 70". The recirculation medium may additionally comprise a scrubber or cleaner to remove another portion of the hydrogen halide. Specifically, hydrogen (H2), nitrogen (N2), hydrogen chloride (HCl) and water (H20), all in the vapor form, are conducted through line 60"to a scrubber or cleaner 62". An alkaline solution is added to the scrubber or cleaner 62"through a line 64", so that the scrubber removes another portion of the hydrogen chloride through line 68", such as an alkaline halide salt. In this third mode, nitrogen and hydrogen and water vapor can not be separated. Thus, a portion of the hydrogen (H2), nitrogen (N2) and water (H20), all in the vapor form, are vented through a line 66". Another portion of the hydrogen (H2), nitrogen (N2) and water (H20), all in the vapor form, are conducted away from the scrubber or cleaner 62"by a line 67". In the third embodiment of Figure 4, the recirculation means also comprises a humidifier for moistening the released or discharged fluid. A humidifier 65"moistens the released fluid, which is hydrogen vapor, nitrogen vapor and water vapor, with water, in the form either liquid or vapor through the line 69". The recirculation means also comprises a compressor 72"to compress the released fluid. The water, hydrogen and nitrogen, all in the form of vapor, are then removed from the compressor 72"through the line 74". The humidified fluid is carried away from line 69"by line 71". The recirculating means of the third embodiment may also comprise a temperature regulator, shown as a heater / cooler 80"in Figure 4, which regulates the acclimatization of the released fluid. The water, hydrogen and nitrogen are then transported or conducted through a line 74"to the temperature regulator 80". The temperature regulator 80"can heat or cool the released fluid, depending on the desired temperature of the cell. The recirculation means of the second embodiment may additionally comprise an air conditioner 78"to supply heat and water to the fluid released through the line 77". As in the second previous embodiment, either a humidifier or an air conditioner are used in the recirculation circuit of the third mode, but not both. Further, in the third embodiment, the additional nitrogen is supplied from a source 84"to the cell through a line 83", since the nitrogen is lost in the circuit through line 66. However, it should be noted that nitrogen can be added anywhere in the recirculation circuit. Nitrogen (N2) and water vapor (H20 (steam)) are conducted through a line 82"back to the electrochemical cell 10", where they are used to continuously supply a humidified or humidified gas stream. , which includes nitrogen, to the membrane next to the cathode of the membrane. Further in accordance with the fourth embodiment of the present invention, there is provided a system and a process for recirculating a gas stream from an electrochemical cell used for the direct production of essentially dry halogen gas from the essentially anhydrous hydrogen halide. The system of the fourth embodiment is shown in Figure 5 and comprises an electrochemical cell 10 '' ', which is the same as the electrochemical cell 10 described above. In the fourth embodiment, a humidified gas stream comprising oxygen is fed to the cathode side entrance 24 as shown in Figure 1. The humidified gas comprises mainly oxygen. However, in practice, traces of other gases, not including hydrogen, but including nitrogen, may be in the gas stream. The lateral outlet of the cathode 26 as shown in Figure 1 releases or discharges a fluid from the cathode through a line 50 '' ', which in the fourth embodiment comprises oxygen (02), water (H20) and hydrogen halide , such as hydrogen chloride (HCl), all in the vapor form, as shown in Figure 5. The system for directly producing essentially dry halogen gas from essentially anhydrous hydrogen halide of the fourth embodiment, further comprises means for recirculating the fluid released back to the cation transport medium. More specifically, the recirculation means comprises a recirculation circuit which recirculates the fluid released or discharged back to the membrane on the side or side of the cathode of the membrane. The recirculation means of the third embodiment may comprise a cooler for cooling the released fluid. As shown in Figure 5, water (H20), oxygen (02) and hydrogen chloride (HCl), all in the form of vapor, are conducted through a line 50"'to a cooler 52". 'which cools the fluid released. As noted above, the released fluid comprises hydrogen halide, and preferably hydrogen chloride, and the recirculation medium also comprises a separator for removing a portion of the hydrogen halide from the released fluid. As shown in Figure 5, after the released fluid is cooled, transported or conducted through a line 54 '' 'to a separator 56' '', which removes a portion of the hydrogen chloride and water (H20), in the form of liquid, through a line 70 '' '. The recirculation medium may additionally comprise a scrubber or cleaner to remove another portion of the hydrogen halide. Specifically, oxygen (02), hydrogen chloride (HCl) and water (H20), all in the form of vapor, are conducted through a line 60 '' 'to a scrubber or cleaner 62' ''. An alkaline solution is added to the scrubber or cleaner 62 '' 'through a line 64' '', so that the scrubber removes another portion of the hydrogen chloride through a line 68 '' ', such as an alkaline salt of halide In this fourth embodiment, a portion of the oxygen vapor (02) and water vapor (H20) is not vented, but preferably all of the oxygen and water vapor are carried away from the scrubber 62 '' 'by a line 67'. ''. In the fourth embodiment of Figure 5, the recirculation means may also comprise a humidifier 65 '' 'for moistening the fluid released with water, in either the liquid or vapor form, through line 69' ''. The humidifying fluid moves away from the line 69 '' 'by a line 71' ''. The recirculation means may also comprise a compressor 12 '' 'for compressing the released or discharged fluid. The water vapor and oxygen vapor are then made or conducted outside the compressor 72 '' 'through the line 74' ''. The means of recirculation of the fourth embodiment may also comprise an oxygen supply to supply additional oxygen to the fluid released. An oxygen supply supplies additional oxygen to the fluid released through line 77 '' 'as shown in Figure 5, although this line could be replaced anywhere in the recirculation circuit. It is necessary to add oxygen in the fourth mode since the oxygen becomes consumed when it is reacted with protons in the cell to make or produce water. A line 79 '' 'conducts oxygenated released fluid away from the oxygen feed or supply line 83' ''. The recirculation means of the fourth embodiment also comprises a hardener. Shown as heater / cooler 80 '' 'in Figure 5, which anneals the released fluid. The temperature regulator 80 '' 'can heat or cool the released fluid, depending on the desired temperature of the cell. A line 76 '' 'conducts the tempered fluid away from the quencher 80' ''. The recirculating means of the fourth embodiment may further comprise an air conditioner 78 '' 'for supplying heat and water to the fluid released through line 11' ''. As in the second and third modes, either a humidifier or an air conditioner, but not both, it is used in the fourth mode. Oxygen (02) and water vapor (H20 (Steam)) are conducted through line 82 '' 'back to electrochemical cell 10' '', where oxygen is used to continuously supply a stream of oxygen. humidified gas, which includes oxygen, to the membrane. Further in accordance with the first to fourth embodiments of the present invention, a process is provided for the direct production of essentially dry halogen gas from the essentially anhydrous hydrogen halide. The anhydrous hydrogen halide can comprise hydrogen chloride, hydrogen bromide, hydrogen fluoride or hydrogen iodide. It should be noted that the production of bromide gas and iodide gas can be performed when the electrochemical cell is operated at elevated temperatures (i.e., about 60 ° C and above for bromide and about 190 ° C and above for iodide). In the case of iodide, a membrane made of a material other than NAFION® should be used.

The operation of the electrochemical cell of the first three embodiments will now be described as referring to a preferred embodiment of the process of the present invention, wherein the anhydrous hydrogen halide is hydrogen chloride. In the operation, the current flows to the anode busbar, and the anodic current distributor 40 collects or recovers the current from the anode busbar and distributes it to the anode by electronic conduction. The essentially anhydrous hydrogen chloride gas molecules are fed to an inlet, specifically the inlet 14 of the anode of the electrochemical cell 10, and are conveyed to the surface of the anode 12 and through the gas channels in the flow fields of the electrode. dough. In the first mode, the liquid water as shown in Figure 2 is added to the cell at the cathode. Water is supplied to the cathode through the cathode inlet 24 and through the flow channels 31 formed in the cathode flow field 30. In the second mode, a stream of humidified gas comprising hydrogen is supplied to the cathode at through the cathode inlet 24, and in the third embodiment, a stream of humidified gas comprising nitrogen is supplied or provided through the inlet 24.

This hydrates the membrane and thereby increases the efficiency of proton transport through the membrane. The molecules of anhydrous hydrogen chloride are oxidized at the anode under the potential created by the voltage source to produce essentially dry chlorine gas at the anode, and protons (H +). The reaction is given by the equation: Electric Power 2HC1 (g) 2H + + Cl2 (g) + 2e "4) The chlorine gas exits through the anode outlet 16 as shown in Figure 1. The protons are transported through the membrane, which acts as an electrolyte. Transported protons are reduced at the cathode. This reaction is provided by the equation: Electric Power 2H + + 2e "H2 (g) (5) A fluid is released or discharged from the cell and recirculated back to the membrane through the recirculation circuits as described above with respect to Figures 2-4. The hydrogen that is wrapped at the interface between the cathode and the membrane exits via the lateral outlet of the cathode 26. The hydrogen bubbles through the water and is not affected by the TEFLON® in the electrode. The cathode current distributor 42 collects or collects the current from the cathode 20 and distributes it to a collector or distribution bar 48 of the cathode. In the first to third embodiments, the amount of current required to achieve a balance between the water carried by diffusion to the anode and entrained by proton transport to the cathode is controlled by adjusting the amount of water supplied to the membrane. In the second and third modes, the water supplied to the membrane is adjusted by controlling the feed rate of the humidified gas stream. Alternatively, the water fed or supplied to the membrane is adjusted by controlling the water content of the humidified gas stream. As noted above, although humidified gas streams comprising either hydrogen or nitrogen are described by the first embodiment, it is within the scope of the present invention for humidified gas streams comprising other gases.

In the fourth embodiment of the present invention, the electrochemical cell is operated as described above, except that a stream of humidified gas comprising oxygen is supplied to the cell at the cathode. The oxygen and transported protons are reduced in the cathode to water, which is expressed by the following equation: 1/2 02 (g) + 2e ~ + 2H + - »H20 (g) 6) The formed water exits via the side outlet of the cathode 26 as shown in Figure 1, along with any nitrogen and unreacted oxygen. The water also helps maintain the hydration of the membrane. The lateral outlet of the cathode releases a fluid from the cathode, which comprises oxygen (02), water (H20) and hydrogen halide, such as hydrogen chloride (HCl), as described above with respect to Figure 5. This fluid released from the cell is recirculated back to the membrane through the recirculation circuit as described above with respect to Figure 5. As in the first three modes, in the fourth embodiment, the amount of current required to achieve a balance between water carried by diffusion to the anode and entrained by the transport of protons to the cathode, it is controlled by adjusting the amount of water supplied to the membrane. Also in the fourth embodiment, as in the second and third modes, the water supplied to the membrane is adjusted by controlling the feeding speed of the humidified gas stream. Alternatively, the water supplied to the membrane is adjusted by controlling the water content of the humidified gas stream. Again, although a stream of humidified gas comprising oxygen is described by the second embodiment, humidified gas streams comprising other gases are within the scope of the present invention. In this fourth embodiment, the reaction of the cathode is in the formation of water. This reaction of the cathode has the advantage of more favorable thermodynamics relative to the production of H2 at the cathode as in the first mode. This is because of the total or complete reaction of this modality, which is expressed by the following equation: Electric Power 2HCl (g) + 1 202 (g) > H20 (g) + Cl2 (g) (12) involves a lower free energy change than the free energy change for the total or complete reaction in the first mode, which is expressed by the following equation: Electric Power 2HCl (g) > H2 (g) + Cl2 (g) (13) Therefore, the amount of voltage and energy required as cell power is reduced in all four modes. Furthermore, in the first three embodiments of the present invention, there is no oxygen in the cathode reaction. However, in the fourth mode, where oxygen is added to the cell, there is always an excess of oxygen in the cell. This means that almost all of the protons transported through the membrane react with oxygen to form water. This provides a higher conversion to water. In addition, the largest excess of oxygen, the fastest of the cathode reactions proceed. Therefore, the recirculation circuit of the fourth particular mode provides a faster cathode reaction. In addition, with the fourth embodiment, it is possible to take advantage of this oxygen excess without the economic penalty of discharging products from the cell through a suction cup or vent hole 66, 66 'or 66"as described above for the three first modalities. Additional advantages and modifications will easily occur to those skilled in the art. The invention, in its broader aspects, is therefore not limited to the specified details, representative apparatus and illustrative examples shown and described. Accordingly, deviations can be made from such details without departing from the spirit or scope of the general concept of the invention as defined by the appended claims and their equivalents. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, the content of the following is claimed as property

Claims (48)

1. A process for the direct production gas essentially dry halogen from hydrogen halide essentially anhydrous, characterized in that: (a) molecules of hydrogen halide essentially anhydrous feed to an inlet of the electrochemical cell and are transported to an anode of the cell; (b) the molecules of the essentially anhydrous hydrogen halide are oxidized at the anode to produce essentially dry halogen gas and protons; (c) the protons are transported through a cation transport membrane of the cell; (d) transported protons are reduced to a cathode of the electrochemical cell; and (e) a stream of humidified gas is supplied to the membrane.

2. A process for the direct production of essentially dry halogen gas from the essentially anhydrous hydrogen halide, characterized in that: (a) the current is supplied to an electrochemical cell; (b) essentially anhydrous hydrogen halide molecules are fed to an inlet of the electrochemical cell and transported to an anode in the cell; (c) essentially anhydrous hydrogen halide molecules are oxidized at the anode to produce essentially dry halogen gas and protons; (d) the current supplied to the electrochemical cell causes the protons to be transported through a cation transport membrane of the cell; (e) transported protons are reduced to a cathode of the electrochemical cell; (f) the water is supplied to the membrane at the cathode and is transported by diffusion to the anode; (g) transported protons entrain water in the membrane towards the cathode; and (h) the amount of current required to achieve a balance between the water carried by diffusion to the anode and entrained by proton transport to the cathode is controlled by adjusting the amount of water supplied to the membrane.

3. The process according to claim 2, characterized in that the water is supplied to the membrane by adding a stream of humidified gas to the cathode.

4. The process according to any of claims 1 or 3, characterized in that the water supplied to the membrane is adjusted by controlling the feed speed of the humidified gas stream.

5. The process according to any of claims 1 or 3, characterized in that the water supplied to the membrane is adjusted by controlling the water content of the humidified gas stream.

6. The process according to any of claims 1 or 3, characterized in that the humidified or moistened gas stream comprises hydrogen.

7. The process according to any of claims 1 or 3, characterized in that the humidified gas stream comprises nitrogen.

8. The process according to any of claims 1 or 3, characterized in that the humidified gas stream comprises oxygen.

9. The process according to any of the embodiments 1 or 2, characterized in that a fluid is released from the cell and recirculated back to the membrane.

10. The process according to claim 10, characterized in that the released fluid is cooled before being recirculated back to the membrane.

11. The process according to claim 9, characterized in that the water is supplied to the membrane by adding liquid water to the cathode.

12. The process according to claim 11, characterized in that the fluid released or discharged comprises water, hydrogen and hydrogen halide.

13. The process according to claim 12, characterized in that the hydrogen halide portion and the water are removed from the fluid released by separation.

14. The process according to claim 13, wherein another portion of the hydrogen halide and hydrogen is sent to a scrubber or cleaner, and hydrogen is separated from the hydrogen halide in the scrubber or cleaner.

15. The process according to claim 9, characterized in that the humidified gas stream comprises hydrogen.

16. The process according to claim 15, characterized in that the fluid released comprises water, hydrogen and hydrogen halide.

17. The process according to claim 16, characterized in that a portion of the hydrogen halide and water are removed from the gas recovered by separation.

18. The process according to claim 17, characterized in that another portion of the hydrogen halide and water are sent to a scrubber or cleaner, and the hydrogen and water are separated from the hydrogen halide in the scrubber or scrubber cleaner. gases

19. The process according to claim 18, characterized in that the portion of hydrogen and water, in the form of steam, are vented from the scrubber or gas cleaner.

20. The process according to claim 11, characterized in that the moistened gas stream comprises nitrogen.

21. The process according to claim 20, characterized in that the recovered gas comprises hydrogen, nitrogen, water and hydrogen halide.

22. The process according to claim 21, characterized in that a portion of the hydrogen halide and water are removed from the fluid released by separation.

23. The process according to claim 22, characterized in that another portion of the hydrogen halide and water, and nitrogen and hydrogen are sent to a scrubber or cleaner, and the hydrogen, nitrogen and water are separated from the hydrogen halide. by the scrubber or gas cleaner.

24. The process according to claim 23, characterized in that a portion of hydrogen and nitrogen, and water, in the vapor form, are vented from the scrubber or gas scrubber.

25. The process according to claim 9, characterized in that the humidified or humidified gas stream comprises oxygen.

26. The process according to claim 25, characterized in that the recovered gas comprises oxygen, water vapor and hydrogen halide.

27. The process according to claim 26, characterized in that a portion of the hydrogen halide and water are removed from the fluid released by separation.

28. The process according to claim 26, characterized in that another portion of the hydrogen halide and the water, in the vapor form, and the oxygen are sent to a scrubber or cleaner, and the oxygen and water are separated from the halide of hydrogen by the scrubber.

29. The process according to claim 23, characterized in that all the oxygen and water vapor are recirculated to the membrane.

30. The process according to claim 29, characterized in that an additional supply of oxygen is added to the released fluid before being recirculated to the membrane.

31. The process according to claim 9, characterized in that the released or discharged fluid is compressed before being recirculated to the membrane.

32. The process according to claim 9, characterized in that the released or discharged fluid is quenched before being recirculated to the membrane.

33. The process according to claim 9, characterized in that the released fluid is humidified with water before being recirculated to the membrane.

34. The process according to claim 9, characterized in that the released fluid is heated with current before being recirculated to the membrane.

35. An electrochemical cell for directly producing essentially dry halogen gas from essentially anhydrous hydrogen halide, characterized in that it comprises: (a) means for oxidizing essentially anhydrous hydrogen halide molecules to produce essentially dry halogen gas and protons, (b) cation transport means for transporting the protons therethrough, wherein the oxidation means is brought into contact with one side of the cation transport medium; (c) means for reducing transported protons, wherein the reduction means are brought into contact with the other side of the cation transport means; and (d) means for supplying water to the cation transport means on the other side of the cation transport means.

36. The electrochemical cell according to claim 35, characterized in that the oxidation means is an anode, the reduction means is a cathode, and the cation transport means is a cathode.

37. The electrochemical cell according to claim 36, characterized in that the means for supplying water to the membrane comprises an inlet disposed on the side or side of the cathode of the membrane.

38. A system for recirculating a fluid released or discharged from an electrochemical cell used for the direct production of essentially dry halogen gas from essentially anhydrous hydrogen halide, characterized in that it comprises: (a) an electrochemical cell comprising: (i) to oxidize essentially anhydrous hydrogen halide molecules to produce essentially dry halogen gas and protons; (ii) cation transport means for transporting the protons therethrough which have a side disposed in contact with the oxidation means; (iii) means for reducing transported protons, wherein the reduction means are placed in contact with the other side of the cation transport means; (iv) means of entry to supply water to cation transport means; and (v) outlet means for releasing a fluid from the reduction medium; and (b) means for recirculating the fluid to the cation transport means.

39. The system according to claim 38, characterized in that the oxidation means comprises an anode, the reduction means comprises a cathode and the cation transport means comprises a membrane.

40. The system according to claim 39, characterized in that the recirculation means comprises a cooler for cooling the release fluid before it is recirculated to the membrane.

41. The system according to claim 39, characterized in that the recovered gas stream comprises hydrogen halide and wherein in addition the recirculation means comprises a separator for removing a portion of the hydrogen halide from the fluid.

42. The system according to claim 41, characterized in that the recirculation means further comprise a scrubber to remove another portion of the hydrogen halide.

43. The system according to claim 39, characterized in recirculating means further comprise a compressor for compressing the released fluid before being recirculated to the membrane.

44. The system according to claim 39, characterized in that the recirculation means further comprise a pump for pumping the release fluid to the membrane.

45. The system according to claim 39, characterized in that the recirculation means additionally comprise tempering means for quenching the released fluid before being recirculated to the membrane.

46. The system according to claim 39, characterized in that the recirculation means further comprises a humidifier for humidifying or humidifying the released or discharged fluid before it is recirculated to the membrane.

47. The system according to claim 39, characterized in that the recirculation means further comprises an air conditioner for conditioning the released fluid before it is recirculated to the membrane.

48. The system according to claim 40, characterized in that the released fluid comprises oxygen and the recirculation means further comprise an oxygen supply to supply oxygen additional to the recovered oxygen before the oxygen is recirculated to the membrane.