USRE26913E - Multistage process for the concentra- tion of heavy water in feed water com- prising a mixture of water and heavy water - Google Patents
Multistage process for the concentra- tion of heavy water in feed water com- prising a mixture of water and heavy water Download PDFInfo
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- USRE26913E USRE26913E US26913DE USRE26913E US RE26913 E USRE26913 E US RE26913E US 26913D E US26913D E US 26913DE US RE26913 E USRE26913 E US RE26913E
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- water
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- hydrogen
- heavy water
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B5/00—Water
- C01B5/02—Heavy water; Preparation by chemical reaction of hydrogen isotopes or their compounds, e.g. 4ND3 + 7O2 ---> 4NO2 + 6D2O, 2D2 + O2 ---> 2D2O
Definitions
- INVENTORS GERALD P. LEWIS PAUL RUETSCHI United States Patent O MULTISTAGE PRCESS FOR THE CONCENTRA- TION 0F HEAVY WATER IN FEED WATER COM- PRISING A MIXTURE OF WATER AND HEAVY WATER Gerald P. Lewis and Paul Ruetschi, by ESB Incorporated, Philadelphia, Pa., a corporation of Delaware, assignee Original No. 3,306,832, dated Feb. 28, 1967, Ser. No. 201,978, June 12, 1962. Application for reissue Aug. 3, 1967, Ser. No. 662,215
- ABSTRACT 0F THE DISCLOSURE A process for concentrating heavy water using successive stages by electrolyzng a mixture of water and heavy water to produce hydrogen and deuteriunz gas at the cathode and oxidizing the gas mixture at the anode.
- the cathode and anode are separated by a diuson barrier which prevents instantaneous mixing of the electrolyte surrounding the electrodes.
- the electrolyte at the cathode becomes enriched by preferential evolution of the hydrogen and is further enriched by being fed to the cathode compartment of the next stage of concentration.
- the present invention generally relates to the production of heavy water. More specifically, the present invention is concerned with a process for increasing the concentration of heavy water in natural water by electrochemical means.
- Heavy water (D20) is present in natural water (H2O) in concentrations of about 1 part in 7,000. lt is known that in the electrolysis of water the ratio of hydrogen (H2) to deuterium (D2) in the gas evolved at the cathode is higher than that in the electrolyte and as a result, the heavy water content of the electrolyte is increased.
- This principle has been utilized in the production of heavy water and water enriched in heavy Water by carrying out electrolysis of water in a series of stages, the enriched water from the rst stage, which is fed with ordinary water, being transferred to the second stage where further enrichment takes place and then to a third stage and so on until the desired degree of enrichment is attained.
- the deuterium content of the gas evolved in each stage is proportional to the heavy water content of the electrolyte and therefore increases with each successive stage of electrolysis.
- This deuterium is recovered and returned to the process by converting the hydrogen and deuterium evolved in each stage, except the first, into water which is then passed back to the electrolyte in the preceding stage.
- One method of converting the hydrogen and deuterium gas mixtures to water is by burning it in an atmosphere containing oxygen, cooling the water and returning it to the process. While this method of producing heavy water is used in some areas where electric power is ⁇ both plentiful and inexpensive, it is not widely used because of the enormous amounts of electric power required by the process.
- the amount of electric power required for the production of heavy water ⁇ by electrolysis may be reduced by the utilization of a process described by Eduard Iusti in his German Pat. No. 1,051,820.
- This process uses gas diffusion electrodes of the fuel cell type as anodes and cathodes in the electrolytic cells. Hydrogen enriched in deuterium is consumed at the anode and hydrogen depleted in deuterium is evolved at the cathode.
- the electrolyte is enriched Cir ICC
- the electrolytic cells in this process have much lower potentials than the electrolytic cells of the conventional type and therefore a considerable saving in energy cost is achieved by this technique. It has been calculated that the voltage of an electrolytic cell in the Justi process with two gas diffusion electrodes would require between 50 and 200 millivolts as compared with at least 1.8 volts for the conventional hydrogen-oxygen cell. Additional energy recovery is obtained by consuming the waste hydrogen in a hydrogen-oxygen fuel cell to produce electrical energy for the process.
- each stage consists of an electrolytic cell having an anode and a cathode separated from each other by an electrolyte permeable diaphragm which defines an anode compartment and a cathode compartment and which prevents the instantaneous mixing of the electrolyte in these compartments.
- Both the anode and the cathode may be of the porous gas consuming type, however, the cathode may be of the conventional electrolytic type.
- the cathode compartment of the rst stage is fed with water with a natural abundance of heavy water.
- This water is partially electrolyzed at the cathode and the electrolyte in the cathode compartment is consequently enriched in heavy water by the preferential evolution of hydrogen.
- the hydrogen and deuterium gas mixture evolved at the cathode is completely consumed at the anode of the electrolytic cell of the same stage, producing water.
- the electrolyte in the cathode compartment of each stage which is enriched in heavy water is fed to the cathode compartment of the succeeding stage where the heavy water concentration is further increased. Since the electrolyte from the anode compartment of each stage has a heavy water concentration which is less than that of the electrolyte in the cathode compartment of the stage, it is returned as additional feed to the cathode compartment of the preceding stage.
- each stage in the process may be made smaller in size and capacity than the preceding stage.
- Hydrogen is completely recycled within the process and the only feed necessary after operation has begun is natural Water feed.
- the cathode in each stage performs the enrichment while the anode serves only to provide a second electrode to complete the circuit. This results in the preferential evolution of hydrogen at a potential which is about one-tenth that necessary for the conventional electrolysis process producing hydrogen and oxygen. Since the hydrogen is recycled within each stage, the capacity of the plant is dependent only on the size of the stages.
- Each of the stages is essentially similar, but as indicated, decreases in size and capacity as the product stage of the process is reached.
- the number of stages employed will depend upon the degree of heavy water concentration desired in the product. Similar reference numerals with appropriate letter subscripts have been used to designate the components of the stages.
- Each of the stages comprises an electrolytic cell 1 containing an electrolyte 2 which may be either alkaline or acid. In general, alkaline electrolytes are preferred, inasmuch as suitable electrodes for use therewith are more readily available.
- Each of the electrolytic cells 1 is divided into an anode compartment 3 and a cathode compartment 4 by means of an electrolyte permeable diaphragm 5 which is operative to prevent the instantaneous mixing of the electrolyte in the cell compartments.
- Microporous membranes such as those utilized as separators in storage batteries and electrodialysis cells have been found suitable for use as the diaphragms 5.
- Illustrative of such materials is microporous thermoplastic resin such as polyethylene, microporous rubber, and the like.
- the anode compartment 3 of each cell houses a gas diffusion electrode 6 of the porous fuel cell type.
- the gas diffusion anodes 6 may conveniently be made of porous sintered bodies of finely divided metals known to be catalytically active in promoting the oxidation of hydrogen.
- a double skeleton catalyst electrode such as described and claimed in U.S. Pat. No. 2,928,891, issued Mar. 16, 1960, to E. Justi et al., of Rancy-nickel catalyst granules is illustrative of an electrode suitable for this application.
- Porous electrodes fabricated of silver, nickel, palladium and other metals of the platinum group have also been found to malte excellent electrodes for this purpose, providing an electrolyte-gas-catalyst interface ywhich efficiently promotes the oxidation of hydrogen to water at loW polarization potentials.
- the cathode compartment 4 of each all house a cathode 7 which may also be of the porous fuel cell type such as described in connection with the anode 6, however, the cathode 7 may also be a cathode of the type utilized in conventional electrolytic cells for the electrolysis of water.
- the cathodes 7 need not be made of highly catalytically active metals since less noble metals such as iron are adequate for the purpose.
- the electrodes 6 and 7 of the electrolytic cells 1 are connected in series and to a suitable source of direct current 8 by means of the conductors 9 and 10 such that the anode in each cell is at a more positive potential than the cath- 0de.
- the electrodes 6 and 7 0f the electrolytic cells 1 are connected in parallel or to individual power supplies.' the drawing shows the cells having a parallel coltnecton to a suitable source of direct current 8 by means of the conductors 9 and 10 suc/1 that the anode in each cell is at a more positive potential than the cathode.
- the electrolyte in the anode compartment 3a has a lower heavy water concentration than the electrolyte in the cathode compartment 4a and is consequently discharged as waste by means of the feed line 13a.
- the electrolyte in the anode compartment 3b of the second stage, stage B, whose heavy water concentration is less than that in the cathode compartment 4b of the stage is returned as an additional feed to the cathode compartment 4a of stage A by means of a feed line 13b.
- the feed arrangements for each of the subsequent stages are similar and similar reference numerals with appropriate letter subscripts have been used to designate these components.
- the hydrogen-deuterium gas mixtures evolved at the cathodes 7 of each of the stages is fed by means of a gas feed line 14 to the gas diffusion anode 6 of the stage where it is completely consumed.
- the product is withdrawn from the cathode compartment 4n of the last stage by means of the product feed line 12u.
- the process of the present invention is based upon the cathodic evolution of hydrogen and deuterium gas mixtures from an electrolyte and anodic oxidation of hydrogen and deuterium gases in the same stage.
- the electrolyte is electrolyzed, thereby evolving gas, an enrichment of heavy water in the electrolyte is achieved.
- the evolved gas is poor in deuterium and this can be oxidized electrochemically to produce water.
- the process utilizes the separation of the hydrogen isotopes obtained by electrolysis, the separation factor, S, being defined as the ratio of hydrogen to deuterium in the gas, divided by the same ratio in the liquid.
- This factor is generally expressed as (H i "15) gab S- H ll l 't (-5) c cetro y e
- a cathodic separation factor S can be as high as '7.
- the electrochemical oxidation of hydrogen and deuterium gas simultaneously on a similar porous gas diffusion electrode also results in small voltage losses.
- the anodic separation factor is l.
- the net result of such a system is an electrochemical voltage for the production of hydrogen and the consumption of hydrogen which is not more then one-tenth of the voltage required for the standard technique of electrolysis with hydrogen and oxygen production, since no oxygen evolution is involved.
- the process of the present invention can consist of N number of stages, each stage being smaller than the preceding one as the concentration of heavy water in the cathode compartment electrolyte and evolved gas is increased.
- the diaphragm 5 separating the anode compartment 3 and cathode compartment 4 of each stage prevents the instantaneous mixing of the electrolyte of the stage.
- the operation of each stage is identical, the feed to the cathode compartment of each stage being partially electrolyzed and the electrolyte in the cathode compartment of the stage being consequently enriched in heavy water.
- the evolved gas mixture is deuterium poor.
- the electrolyte from the cathode compartment 4 is then fed to the cathode compartment 4 of the succeeding stage.
- the hydrogen gas produced at the cathode compartment 4 is anodically consumed by the gas diffusion anode 6 producing water which dilutes the electrolyte in the anode compartment 3.
- This electrolyte has a lower heavy water content than the electrolyte in the cathode compartment 4 of the stage.
- electrolyte in the anode compartment 4a is discharged as waste, but the electrolytes in the anode compartments of subsequent stages are fed back as additional feeds to the cathode compartment of the preceding stage, resulting in a maximum deuterium recovery. This process is continued until the desired degree of heavy water concentration is achieved in the cathode compartment of the last stage.
- a process for the concentration of heavy water by successive stages comprising the evolution of a hydrogen and deuterium gas mixture by electrolysis at the cathode of an electrolytic cell from an electrolyte containing mixtures of water and heavy water and consuming said gas mixture by electrochemical oxidization at the anode of said cell, said cathode being separated from said anode by a diffusion barrier which prevents the instantaneous mixing of the electrolyte surrounding said electrodes, an enrichment of the electrolyte taking place at said cathode by a preferential evolution of hydrogen, said enriched electrolyte being fed to the cathode compartment of the next stage of concentration for further enrichment.
- a process for the concentration of heavy water by successive stages the process in each stage comprising the evolution of a hydrogen and deuterium gas mixture at the cathode of an electrolytic cell from an electrolyte containing mixtures of water and heavy water and consuming said gas mixture by electrochemical oxidation at the anode of said cell, said anode and said cathode being separated from each other by an electrolyte permeable barrier which prevents the instantaneous mixing of the electrolyte surrounding said electrodes and which defines an anode compartment and a cathode compartment in said cell, the electrolyte in the cathode compartment being enriched by the preferential evolution of hydrogen and feed to the cathode compartment of the next succeeding stage for further concentration.
- a process for producing multistage concentration of heavy water in feed water containing a mixture of water and heavy water which consists in supplying the feed water to the cathode compartment of an electrolyte containing electrolytic cell comprising the first stage of the process, electrolyzing said feed water at a cathode in said cathode compartment to evolve a mixture of hydrogen and deuterium gas, the electrolyte in said compartment being enriched by the preferential evolution of hydrogen, feeding said hydrogen and deuterium gas mixture to a gas diffusion anode in an anode compartment of said cell and oxidizing said gas mixture at said anode to produce water, said anode compartment and said cathode compartment being separated by an electrolyte permeable diffusion barrier which prevents the instantaneous mixing of the electrolytes in said mixture, feeding the electrolyte from the cathode compartment to the cathode compartment of the next stage, repeating the electrolyzing to further enrich said electrolyte in a series of similar electrolytic cells in which the hydrogen and deuterium gas mixture
- a process for producing multistage concentration of heavy water in feed water containing a mixture of water and heavy water which consists in supplying the feed water to the cathode compartment of an electrolytic cell having a cathode compartment and an anode compartment defined by an electrolyte permeable diaphragm preventing the instantaneous mixing of the electrolyte in said compartments, electrolyzing said feed water at a cathode in said cathode compartment to evolve a mixture of hydrogen and deuterium gas, the electrolyte in said compartment being enriched by the preferential evolution of hydrogen feeding said hydrogen and deuterium gas mixture to a gas diffusion anode in the anode compartment of said cell and oxidizing said gas mixture at said anode to produce water, repeating the process in a series of similar electrolytic cells to achieve further enrichment, the feed to the cathode compartments of said series of electrolytic cells ⁇ being derived from the cathode compartment of the electrolytic cell of the preceding stage and the anode compartment of the electrolytic cell
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Description
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US66221567A | 1967-08-03 | 1967-08-03 |
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USRE26913E true USRE26913E (en) | 1970-06-23 |
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US26913D Expired USRE26913E (en) | 1967-08-03 | 1967-08-03 | Multistage process for the concentra- tion of heavy water in feed water com- prising a mixture of water and heavy water |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2900913A1 (en) * | 1978-05-22 | 1979-11-29 | Atomic Energy Of Canada Ltd | DEVICE AND METHOD FOR ENRICHMENT AND PROCESSING OF HEAVY WATER |
US5183542A (en) * | 1990-01-05 | 1993-02-02 | Westinghouse Electric Corp. | Apparatus and method for separating zirconium isotopes using balanced ion electromigration |
-
1967
- 1967-08-03 US US26913D patent/USRE26913E/en not_active Expired
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2900913A1 (en) * | 1978-05-22 | 1979-11-29 | Atomic Energy Of Canada Ltd | DEVICE AND METHOD FOR ENRICHMENT AND PROCESSING OF HEAVY WATER |
US5183542A (en) * | 1990-01-05 | 1993-02-02 | Westinghouse Electric Corp. | Apparatus and method for separating zirconium isotopes using balanced ion electromigration |
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Owner name: CONGRESS FINANCIAL CORPORATION; A CORP OF CA. Free format text: SECURITY INTEREST;ASSIGNOR:EXIDE CORPORATION;REEL/FRAME:004122/0001 Effective date: 19830322 |
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Owner name: NATIONAL BANK OF CANADA, A BANKING CORP. OF CANADA Free format text: SECURITY INTEREST;ASSIGNOR:EXIDE CORPORATION;REEL/FRAME:004122/0122 Effective date: 19830322 |
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Owner name: EXIDE CORPORATION Free format text: SECURITY AGREEMENT RECORDED MARCH 31, 1983, REEL 4122-FRAMES 001 TO 074 IS HEREBY TERMINATED;ASSIGNOR:CONGRESS FINANCIAL CORPORATION;REEL/FRAME:004747/0780 Effective date: 19870409 |
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Owner name: EXIDE CORPORATION Free format text: RELEASED BY SECURED PARTY;ASSIGNOR:NATIONAL BANK OF CANADA;REEL/FRAME:004775/0726 Effective date: 19870921 Owner name: EXIDE CORPORATION, A DE CORP. Free format text: RELEASED BY SECURED PARTY;ASSIGNOR:NATIONAL BANK OF CANADA;REEL/FRAME:004775/0726 Effective date: 19870921 |