|Publication number||US3594232 A|
|Publication date||Jul 20, 1971|
|Filing date||Jul 12, 1968|
|Priority date||Jul 19, 1967|
|Publication number||US 3594232 A, US 3594232A, US-A-3594232, US3594232 A, US3594232A|
|Original Assignee||Varta Ag|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (30), Classifications (15)|
|External Links: USPTO, USPTO Assignment, Espacenet|
July 20,1971 D.sPAHRB|r-:R l' I 3,594,232
DEVICE FOR THE AUTOMATIC ADJUSTMENT OF THE SUPPLY OF LIQUIDS Filed July l2, 1968 7Sheets-Sheet x MY 20. 1971 D. SPAHRBIER 3,594,232
DEVICE FOR THE AUTOMATIC ADJUSTMENT OF THE SUPPLY OF LIQUIDS Fle'd July 11?..v 1968 7 Sheets-Sheet 2 9/ gli MY 20. 1971 n. sPAHRBlER 3,594,232
DEVICE FOR THE AUTOMATIC ADJUSTMENT OF THE SUPPLY OF LIQUIDS Filed July 12, 1968 7 ShBBtS-Sht 5 INVEN'T( )R 0/5729? mf/Raffa?,
July 20, 1971 D. sPAHRBlER 3,594,232-
DEVICE FOR THE AUTOMATIC ADJUSTMENT OF THE SUPPLY OF LIQUIDS Filed July l2. 1968 7 Sheets-Sheet 5 hhhhhhh T 'i 62 6?"9 F ATT( )HNIIKS D. SPAHRBIER July 20, 1971 DEVICE FOR THE AUTOMATIC ADJUSTMENT OF THE SUPPLY OF LIQUIDS Fild July 1'2. 1968 7 Sheets-Sheet 6 I N VE NTOR D. SPAHRBIER July 20, 1971 DEVICE FOR THE AUTOMATIC ADJUSTMENT OF THE SUPPLY OF' LIQUIDS Filed July l2. 1968 7 Sheets-Sheet, 7
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BY 4 i M @ma United States Patent Olce Patented July 20, 1971 3,594,232 DEVICE FOR THE AUTOMATIC ADJUSTMENT OF THE SUPPLY F LIQUIDS Dieter Spahrbier, Frankfurt am Main, Germany, assiguor to Varta Aktiengesellschaft, Frankfurt am Main, Germany Filed July 12, 1968, Ser. No. 744,357 Claims priority, application Germany, July 19, 1967, V 34,103; Mar. 13, 1968, P 16 67 346.4 Int. Cl. B01j 7/02; F04f 1/14; H01m 27/14 U.S. Cl. 136-86C 18 Claims ABSTRACT 0F THE DISCLOSURE BACKGROUND OF THE INVENTION (l) Field of the invention The invention relates to the field of supplying catalytically decomposable liquids or dissolved materials to a catalyst on which such liquids or materials may be decomposed with the attendant formation of gas. The catalyst may be located in a gas diffusion electrode of a fuel cell element.
(2) Description of the prior art German Pat. 1,180,438 discloses that one can operate hydrogen diffusion electrodes in fuel cell elements by supplying the electrode with liquid electrolyte which contains sodium borohydride. The sodium borohydride is decomposed at the catalyst material of the hydrogen diffusion electrode `with evolution of hydrogen.
British Pat. 963,254 discloses a fuel cell element in which a solution of hydrogen peroxide is forced through the porous oxygen electrode and the excess liquid electrolyte is removed from the space between the two electrodes.
It is possible, by using appropriate conveyors and suitable control systems to supply liquid electrolyte or a liquid :which contains hydrogen or oxygen yielding substances to diffusion electrodes in amounts corresponding to the amount of electrical power withdrawn from the fuel cell element. Pumps may be used for this purpose but the electrical power used by the pumps decreases the electrical power output of the fuel cell system. The use of pumps also increases the possibility of failure of the installation. One can also supply liquids to the electrodes by gas pressure instead of other conveyor means.
SUMMARY lOF THE INVENTION An object of the present invention is to provide a process and suitable devices for the automatic adjustment of the flow of liquids or dissolved substances, which may be dego`mposed on a catalyst with the evolution of gas, from a storage container for such liquid to a decomposer which contains catalyst which may be used for the decomposition of such liquids or substances with the evolution of gas.
Another object of the present invention is to provide such a process and devices lwhereby liquids which are decomposable upon contact with catalysts with the attendant evolution of gas may be supplied to the catalyst bed of a decomposer under constant pressure without using a pump.
A further object of the present invention is to provide such a process and devices which are adaptable for supplying such catalytically decomposable liquids to catalytically active layers of gas diffusion electrodes in fuel cell elements in the simplest manner possible.
The essence of the present invention resides in ernploying an auxiliary catalyst body on which a relatively small portion of liquid may be decomposed so as to thereby provide a pressurized supply of gas with a predetermined pressure which may be used, in turn, to regulate the main supply of decomposable liquid to the main liquid decomposing catalyst body.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the devices of the present invention wherein an auxiliary decomposer is employed.
FIG. 2 shows a modification of the device of FIG. l.
FIGS. 3, 7 and 8 show embodiments of the devices of the present invention which are adapted for use with the gas diffusion electrodes of fuel cell elements.
FIGS. 4, 5 and 6 show embodiments of the devices of the present invention in Iwhich the auxiliary decomposer is either directly connected to, or located inside of, or arranged outside of, the storage container for the decomposable liquid.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The problems facing the present inventor were solved by means of the devices and process of the present invention `which may be employed for the automatic adjustment of the supply of liquids or dissolved substances, .which may be decomposed on a catalyst with the evolution of gas, from a storage container for such liquids or substances to a decomposer container ycatalyst material under a predetermined feed pressure. 'The characteristic feature of the devices of the present invention is that the storage container is in liquid supply communication with an auxiliary decomposer which contains catalyst material by way of a valve for liquids, and the operation of the valve is controlled by the gas pressure above the level of the liquid in the storage container. The valve for the liquids is adjusted in such a way that the supply of liquid to the catalyst bed of the auxiliary decomposer is released if the gas pressure above the level of the liquid in the storage container falls 'below a certain predetermined value.
In an advantageous embodiment of the devices of the present invention the auxiliary decomposer is arranged immediately inside the liquid storage container above the level of the liquid therein. The liquid supply communication between the liquid and the catalyst bed of the auxiliary decomposer is formed by a wick. The valve for the liquid is a device for severing the liquid supply communication between the wick and the catalyst bed. The valve can take the form, for example, of a membrane subjected to tension 'by the pressure of a spring, to which membrane the catalyst bed is attached. When the gas pressure above the level of the liquid decreases, which pressure acts upon the membrane, the tension of the spring prevails and moves the catalyst bed against the wick. The liquid absorbed by the wick is decomposed as it contacts the catalyst bed. When the gas pressure above the level of the liquid again reaches a predetermined value due to the pressure of the gas which is liberated by the catalytic decomposition, then the gas pressure is stronger than the tension of the spring and the membrane is deflected and the liquid supply communication between the catalyst bed and the Wick is thereby broken.
In another advantageous embodiment of the devices of the present invention it is not necessary to xedly arrange the auxiliary decomposer inside the liquid storage J container above the level of the liquid. In this arrangement the auxiliary decomposer is arranged in the liquid inside the storage container and the valve for the liquid is rigidly connected to a movable shutter cover over the catalyst bed of the auxiliary decomposer. The valve for the liquid can also contain in this instance a pressure bellows having a membrane tensioned `by the pressure of a spring.
It is particularly advantageous in the devices of the present invention to also connect the storage container to the catalyst bed of the main decomposer by means of a pressure controlled valve for the liquid. It is thereby provided by this procedure that an approximately constant gas pressure is continuously afforded to the gas consumer. The pressure control of the valve for the liquid can be accomplished, for example, by measuring the pressure differential lbetween the gas pressure in the gas consumer and the gas pressure above the level of the liquid and by allowing for the opening of the valve for the liquid when this pressure differential attains a certain predetermined value. In a preferable embodiment of the devices of the present invention the storage container for the liquid is placed in liquid supply communication by means of a valve for the liquid with the catalyst material containing working layer of one of the two gas diffusion electrodes of a fuel cell element, which electrode is the main gas decomposer. The valve for the liquid is operated lby a predetermined pressure differential between the gas pressure above the level of the liquid in the liquid storage container and the gas pressure in the gas chamber of the gas diffusion electrodes. As a result of the supply of liquid to the catalyst bed of the main gas decomposer the volume of liquid in the liquid storage container is lowered and the volume of the gas space above the level of the liquid in the storage container is increased. The gas pressure in this gas space is lowered, therefore, correspondingly to the volume of liquid supplied to the catalyst bed of the main decomposer. The auxiliary decomposer must produce a corresponding amount of gas in order to maintain the gas pressure above the level of the liquid in the storage container at a constant value. In general the increase of the volume with the decomposition of the liquid and the generation of gas in the main decomposer results in a volume amplification factor of the order of magnitude of 100, so that a simple construction and operation of the control system formed by the devices of the present invention is thus made possible.
Particularly advantageous is a preferred embodiment of the devices of the present invention wherein the auxiliary decomposer is arranged outside the liquid storage container. The storage -container is placed in liquid supply communication with one surface 'of the catalytically 21C- tive layer of the porous catalyst body of the auxiliary decomposer -by means of a rising main or pressure pipe. The other surface of the porous catalyst body is in intimate contact with a fine pored layer which is filled with liquid. To the catalyst body there is attached a gas chamber which is in liquid supply communication with the gas space above the level of the liquid of the storage container via a valve controlled Iby gas pressure. This embodiment of the devices of the present invention makes possible a particularly reliable and effective regulation of the supply of liquid to the main decomposer.
Various embodiments of the devices of the present invention may be further explained by references to the drawings. The manner of operating one embodiment of the devices of the present invention may be explained by the following, with reference to FIG. 1. In storage container 1 there is placed liquid 2 which is catalytically decomposable with the attendant formation of gas. Gas chamber or area 3 above the level of liquid 3 is connected with a pressure difference sensing regulator 4 via line 5, which sensing regulator, together with control line 18, effects the control of liquid valve 10. The atmospheric pressure also acts on pressure difference regulator 4 over line 6. When the difference between the gas pressure in gas space 3 and the atmospheric pressure at point 7 is less than the pressure to which the pressure difference regulator 4 -is adjusted then liquid valve 10 is closed by means of control line 18.
If the level of liquid 2 in storage container 1 falls because of the supplying of liquid to the main decomposer 16, then the pressure difference to which the pressure difference sensing regulator 4 is adjusted lbecomes greater than the difference in pressure between the pressure in gas space 3 and the atmospheric pressure at point 7 and liquid valve 10 is opened by control line 18. The liquid 2 flows over connecting line 13 into auxiliary decomposer 9 and is decomposed on the catalyst bed in Stich decomposer. The gas that is thus set free flows over line 30 and 8, and through buffer volume 28 inserted between such lines, into gas space 3 and valve 10 is closed when the pressure differential between the pressure in gas space 3 and the atmospheric pressure at point 7 reaches the pressure to which pressure sensing regulator 4 is adjusted. Buffer volume 28 inserted in lines 8 and 30 allows for the delay of the decomposition of the liquid in auxiliary decomposer 9. It has the function in this regard of a surge tank as is customarily employed in discontinuously operating gas pumps (piston pumps). Buffer volume 28 is not needed, however, if the volume of gas area 3 is sufficiently large.
Storage container 1 and main decomposer 16 are also part of a second control system, which supplies operating gas over line 26 to the gas consumer. In this second control system a pressure difference regulator 22 also controls the supply of liquid from storage container 1 over line 14 to main gas decomposer 16 by means of valve 15. The gas pressures in gas space 3 and in main gas decomposer 16 act on pressure difference regulator 22 over lines 23 and 20, respectively. Valve 15 is opened by control line 19 as soon as the pressure difference exceeds the pressure to which pressure difference regulator is adjusted. This Vis the case when valve 24 is opened and the gas which is set free in main decomposer 16 is supplied to the gas user over lines 21 and 31 and buffer 'volume 29. When valve 24 is closed, the pressure in main decomposer 16 rises. The pressure differential then becomes greater than the pressure at which pressure difference regulator 22 is standardized and valve 1S is closed. If the decomposition of liquid in main decomposer 16 is not spontaneous, but takes place with a certain delay, then fluctuations in pressure arise which are intercepted by buffer volume 29 and are smoothed out. The fluctuations in pressure are very small if the pressure in main decomposer 16 is made large in comparison to the pressure at which pressure difference regulator 22 is standardized. The constructive configuration of the devices of the present invention is dependent upon the type and concentration of the catalytically decomposable substances employed in the liquids which are supplied to the catalysts in the decomposers. For a trouble free functioning of the devices of the present invention the following conditions, therefore, must be fulfilled:
1) The auxiliary decomposer must be able to produce a larger volume of gas per unit of time, than that corresponding to the maximum volume of liquid that is supplied to the main decomposer in the same period of time.
(2) The maximum volume of gas, lwhich can be produced in a given unit of time in the main decomposer, must be greater than the volume of liquid supplid in the same unit of time to the main decomposer multiplied by the gas amplification factor. This factor specifies how large the volume of gas is which comes into being upon the decomposition of a specific *olme of liquid.
Lines 11 and 17 in the device of FIG. 1 serve as outlet lines for residual liquid.
FIG. 2 shows a particularly advantageous embodiment of the devices of the present invention which is a modification of the device shown in FIG. 1. Elements 1-11, 13, 25, 27 and 30 are the same in FIG. 2, and perform in the same manner, as the correspondingly numbered elements of FIG. l. The control system which contains main decomposer 16a of the device of FIG. 2 has a particularly simple construction. A rising main 15a which is inserted in line 14a forms the valve for the liquid. In addition, rising main 15a also assumes the function of buffer volume 29 and pressure difference regulator 22 of FIG. l. Elements 17a, 21a, 24a and 26a are the same, and function in the same manner, as elements 17, 21y 24 and 26, respectively, of FIG. 1.
FIG. 3 shows an example of an embodiment of the devices of the present invention which contains two main liquid decomposers which are each catalyst layers of gas diffusion electrodes of a fuel cell element. Elements 1 to 7', 9' to 11', 13', 18', 25', 27' and 30', as Well as elements 1" to 7", 9 to 11", 13, 18, 25", 27" and 30" of FIG. 3, correspond to elements 1 to 7, 9 to 11, 12, 18, 25, 27 and 30, respectively, of FIG. 1. Storage containers 1' and 1" are in liquid supply communication with rising mains 15' and v15" over lines 14 and 14" which rising mains simultaneously vassurne the function in the main control system of the pressure difference regulator and the valve for the liquid. The rising mains 15 and 15" are connected over liquid supply line 14a' and 14a" to gas chambers 35 and 36 of gas diffusion electrodes. Working layer 37 of the porous hydrogen diffusion electrode contains carbonyl nickel and, as a catalyst, Raney-nickel and the fine pored cover layer 39 of the electrode consists of carbonyl nickel. In container 1' there is a 16% by weight solution 2 of sodium borohydride in 6 N KOH, which solution decomposes on -working layer 37 with the evolution of hydrogen gas. At room temperature around 0.5 normal liters of hydrogen gas are produced per hour per cm.2 of electrode surface and at 60 C. about l normal liter of gas is produced. The hydrogen gas is electrochemically reacted in the electrode and residual liquid electrolyte is forced through the pores of working layer 37 and cover layer 39 out into electrolyte chamber 41 which is filled with a 6 n aqueous solution of sodium hydroxide by the gas pressure in gas chamber 35. Rising main 15' simultaneously acts as a pressure difference regulator and as a valve for the liquid from container 2. If the gas pressure in gas chamber 35 is higher than the gas pressure in gas area 3 and the hydrostatic pressure of the column of liquid lying between gas chambers 35 and 3', then the liquid is forced out of gas chamber 35 into rising main 15' and rising main 15' becomes partially filled with gas. In this way the supply of liquid 2' to gas chamber 35 and working layer 37 is prevented when the predetermined pressure differential is exceeded and rising main 15' acts as a pressure difference regulator and as a liquid valve. If, because of the consumption of gas in the electrode, the gas pressure in gas chamber 35 decreases, then, because of the gas pressure in gas area 3', liquid is supplied through rising main 15 to working layer 37 of the electrode.
The oxygen for the oxygen electrode of the fuel cell element which contains silver as a catalyst in working layer 38 and whose fine pored cover layer 40 is made of carbonyl nickel is produced in a manner similar to that described above for the generation of hydrogen gas by the decomposition of liquid 2" which is supplied by a device in accordance with the present invention from storage container 1" over rising main 15" and into the gas chamber 36 of the oxygen electrode. The liquid 2" in storage container 1" is in the form of a 30% by weight solution of hydrogen peroxide in water. Valves 24 and 24" allow for the venting of excess gas.
FIG. 4 shows a storage container 1a in a device of the present invention to which there are directly connected a combined pressure difference regulator, a liquid valve and an auxiliary decomposer. In storage container 1a there is located gas chamber or area 3a above the level of liquid 2a and gas chamber 3a is closed by an orifice 50 having an excess pressure valve 501 therein. Liquid 2a is charged into container 1a through tube 52 after twisting out filling screw 51. Valve 53 is arranged in line 14b which leads to the main decomposer. At the base of storage container 1a, the device is sealed by connecting tubes 54 which simultaneously act as pressure difference regulator, liquid valve and auxiliary decomposer. Chamber S15 is filled with gas and chamber 56 beneath membrane `57 is filled with air under atmospheric pressure by reason of air vent 56a. Compression spring 58 can be regulated by means of thumbscrew 59, and it is used to provide membrane 57 with the desired tension, when membrane 55 is displaced, valve cap 61 is actuated by connecting rod 60, which cap in its closed position prevents the passage of liquid 2a from storage container 1a into chamber 55. Chamber 55 is subjected to the gas pressure existing in chamber 3a, which latter chamber is in gas supply communication with chamber 55 through porous hydrophobic plates 62 and l621 and gas line 63. Hydrophobic plates 62 and 621 prevent the passage of liquid through line 63 due to the capillary depression of these plates. A discharge line 64 is provided for undecomposed liquid from chamber 55, and line 64 opens at its lower end into drain vessel 65. At the mouth of the lower end of line 64 there is a porous hydrophilic plate 66 inserted and the capillary pressure in the pores of porous plate 66 is so high that the passage of gas formed in chamber 5-5 through such plate is prevented. Normally, the connection between chamber 55 and storage container 1a is interrupted by valve cap 61. When the gas pressure in chamber 3a falls and, as a result, also the gas pressure in chamber 55, the pressure of spring 58 on membrane 55 preponderates. The membrane is then deflected upwards and valve cap 61 is lifted off connecting tube 54 and fresh gas carrier fluid, laden with dissolved decomposable gas yielding substances, passes from storage container 1a through tubes 54 and onto catalyst bed 67 Gas is generated by the decomposition of the liquid on bed 67. The gas thus generated can then proceed into gas chamber 3a through hydrophobic plates 62 and 621 and gas supply line 63. The increased gas pressure in chamber 55 causes membrane 57 to be forced down into its original position and connecting tubes 54 are sealed again as rod 60 pulls down cap 61.
Thumbscrew 68 serves the purpose, during the filling of liquid into storage container 1 through lling tube 52, of blocking valve cap 61 so that cap 61 is not raised by tensed spring 58 and thus allow liquid to enter catalyst bed 67 during the filling of the liquid into container la. The generation of gas on bed 67 during the filling operation would disturb such operation. Screw 68 is used to limit the extent to which valve cap I61 may be raised.
FIG. 5 shows an embodiment of the pressure difference regulator, liquid valve and auxiliary decomposer of the devices of the present invention in which the function of these three elements is undertaken by a single device. This device can be directly inserted in the liquid 2b in storage container 1b. In this way, it is to be observed, the device is so arranged that the liquid has access to catalyst bed 71 when valve cap 611 is raised. The device consists of a pressure bellows 73, which has a membrane 571 on one of its surfaces, and a lid 74 which, together with membrane 571, encloses chamber 551 which is filled with electrolyte. By means of tubes 72 chamber 551 is placed in continuous liquid supply communication with the volume of liquid 2b and thus chamber 551 is under the same pressure as is the volume of liquid in container 1b. Chamber 561 which is inside pressure bellows 73 is filled with air or another gas or with another good compressible substance and it also contains compression spring 581 which so acts that membrane 571 continuously maintains` a desired tension. If desired, a known regulating device can also be attached to compression spring 581 in order to change the tension of compression spring 581. Connecting rod 6()1 is affixed to membrane 571 and this rod moves valve cap 61 off and onto catalyst bed 71. When the gas pressure in gas chamber 3b decreases then the corresponding pressure in chamber 551 decreases and membrane 57l is so deflected by the tension of compression spring 581 that valve cap 61 is raised otf catalyst bed 71 and fresh liquid 2b Hows onto the catalyst. The gas thus formed by the catalytic decomposition of the liquid on bed 71 flows from the open space beneath cap 61l and collects in gas chamber 3b. The pressure in gas chamber 3b thereby continues to increase until the pressure of the liquid on membrane 571 in chamber 551 neutralizes the tension of spring 58l and the total pressure in pressure bellows 561. Elements 141b, 50a, 50u11, 511 and 521 are the same, and serve the function, as elements 14b, 50, 501, 51 and 52, respectively, of FIG. 4.
FIG. 6 shows an embodiment of the device of the present invention in which the auxiliary decomposer is arranged outside of storage container 1c. Liquid 2c is supplied over liquid supply line 95 and through rising main 80 into auxiliary decomposer 96. The catalyst bed of the auxiliary decomposer consists of a porous catalyst containing body 81. Adjacent to this body 81 there is a tine pored layer 82 filled with liquid. Liquid 2c is decomposed upon coming in contact with the catalyst in porous body 81 and the gas which is thus generated collects in gas chamber l83 and from there it passes into gas chamber 3c above the level of liquid 2c in container 1c by way of connecting gas line 84, valve chamber 85 and gas line 86. Gas is generated by the decomposition of liquid 2c on the catalyst of body `81 up to the point where the spring pressure of spring -87 is overcome by the pressure of the gas being exerted on membrane 88 and then the valve opening between chambers `83 and 85 is closed by valve plate 89. The gas pressure in chamber 3c then ceases to rise any further. With the further decomposition of liquid on bed 81, the gas that is formed, therefore, only then raises the pressure in chamber 83 and under the effect of this rising gas pressure in chamber 83 the liquid is forced back into rising main 80 and the supply of liquid 2c to porous body 81 is interrupted until the pressure in chamber 3c subsides again and thus alows valve 89 to open again. By means of thumb screw 90 the pressure of spring 87 can be regulated. In this way the gas pressure in chamber 83 and in chamber 3c can be regulated. If a main decomposer is supplied with liquid 2c over liquid supply line 91 then the standardized and regulated gas pressure in chamber 3c which is used for operating the auxiliary decomposer remains constant in spite of the outliow of a volume of liquid for this purpose. In order to assure a trouble-free operation of auxiliary decomposer 96 it is expedient to insert a device 92 with a suitable resistance to the flow of liquid in connecting line 95. With the selection of a properly dimensioned current resistance 92 it is possible to supply only as much liquid 2c to layer 81 as can be optimally decomposed on the catalyst layer in a given unit of time. The undecomposable residual liquid passes through porous layer 82 into chamber 93 and from there it passes out through drain line 94. Porous layer 83 can be formed as a line pored diaphragm completely filling chamber 93. The diaphragm then has a smaller average pore diameter than the pores of porous body 81 and liquid 2c is, in this way, retained in layer 82.
The capillary pressure of the liquid in layer -82 prevents the passage of gas from chamber 83 into chamber 93. Fine pored layer 82 can also be iixedly combined with porous body 81 by sintering or by other ways. It 1s also possible to ll chamber 92 completely with a porous layer 82.
The device of the present invention have a serles of advantages. These devices, in particular, do not have any movable parts such as supply pumps and the power umts that are used with such pumps. In this way the life and reliability of the devices are considerably increased. v
The supply of liquid to the catalyst bed of the main decomposer takes place automatically without the need for any outside source of energy in this regard. The supply pressure thus remains constant.
The regulating process can be initiated with a pressure difference of a few millimeters of a Water column between the desired and the existing supply pressure.
In comparison to installations in which supply pumps are used the flow resistance for the liquid gas carrier is small in the control system. Therefore one has a high speed control together with a good constant holding of the supply pressure. The supply pressure can be easily adjusted.
The devices of the present invention can be used for different fields for use. For example, they can be used for the generation of operating gases such as hydrogen and oxygen for fuel cell batteries. Also they can be used for the production of the purest hydrogen and oxygen gases for different purposes or for the production of the gases, hydrogen and nitrogen, that may be split from hydrazine. These devices can also be used for the production of oxygen gas for breathing devices. In these instances it is of particular advantage that the liquids which have to be transported for a certain amount of gas represent signicantly less Weight than has been the case with the devices employed up to this time since such latter devices employ steel asks of considerable weight which are filled with pressurized gas.
The devices of the present invention, and the process in which they are employed are particularly suited for use in regulating the supply of decomposable liquid to the catalytically active layers of gas diffusion electrodes in fuel cell elements and batteries. A particularly advantageous embodiment of a fuel cell element or fuel cell battery with which the process of the present invention may be employed is characterized in that the storage container for the decomposable liquid is in liquid supply communication over a liquid supply line or liquid supply line system with the surface of the catalytically active layer of the corresponding electrode and the storage container is in gas supply communication with a gas chamber. In such gas chamber there is located a movable catalyst body which contains a catalyst which is adapted for decomposing the liquid and liberating gas therefrom for use in the electrodes. The catalyst body is connected to a movable membrane which is moved by the gas pressure existing over the liquid in. the storage container, and a wick or absorbent body is positioned in the direction of movement of the movable catalyst body, which wick body is iilled With the decomposable liquid. A device of the present invention of this type is shown in FIG. 7, together with a fuel cell element. In storage container 10'1 there is located liquid reactant 102, for example, a 7% by Weight solution of hydrogen peroxide in water. Into this liquid 102 there is dipped a wick body 103 so that porous plate 104 which is arranged above the level of liquid 102, is saturated with such liquid. Above porous plate 104 there is located catalyst body 105 which can be brought into contact with porous plate 104 by means of thumb screw 106 and gas tight threaded collar 105. As soon as such contact takes place the solution of peroxide which is present in porous plate 104 decomposes into water and oxygen gas. The oxygen which evolves causes a rise in gas pressure in chamber 108. With the rise in gas pressure in chamber 108 flexible membrane or diaphragm 109 is forced outward and catalyst body i105 is thereby raised off porous plate 104 so that further decomposition of the liquid is interrupted. The gas pressure thus created in chamber 108 can be vented to lmanometer 110. If such gas pressure does not yet correspond to a desired supply pressure then catalyst body 5 is brought into contact with porous plate 104 again by turning thumb screw 106. The liquid present in plate 104 is then decomposed with the formation of' oxygen gas and the gas pressure in chamber 108 rises further. By repeating this process the desired supply pressure can be created in chamber 108. The catalyst body 105 is then lifted off porous plate 104 by the deflection of flexible membrane 109 by the gas pressure in chamber 108.
The gas pressure in chamber 108 also prevails in chamber 112 above the level of liquid 102 since porous hydrophobic plate 111 allows for the passage of gas into chamber 112. 'Ihe capillary depression in porous hydrophobic plate 11-1 makes it possible to tip storage container 101 over more than 90 without having liquid 102 ow directly onto catalyst layer 105. For venting excess gas pressure from chamber 108 a safety valve 111a can be placed in the wall of the chamber.
4Due to the gas pressure in chamber 112, liquid 102 is supplied over supply line 113, rising main 114 and capillary 116 to the Working layer of the oxygen electrode 115 of a fuel cell element 124. As the level of the liquid in storage container 101 falls then so falls the gas pressure in chambers 112 and 108. As a result of this decrease in gas pressure flexible membrane 109 is so dellected as to cause catalyst body 105 to fall again and come in contact with porous plate 104 and a generation of gas is initiated again which will persist until the original gas pressure is generated again so as to again deflect membrane 109 outwards and thus cause catalyst body 105 and porous plate 104 to be separated again. The deflection of flexible membrane 109 is determined by the difference in pressure between the pressure inside chambers 108 and 112 and the atmospheric pressure outside membrane 109.
It is, however, also possible to provide an embodiment of the devices of the present invention which operates independently of the outside atmospheric pressure. Thus, one can replace the atmospheric air pressure which acts on the outside of membrane or diaphragm 109 by a spring, the pressure of which is as high as that of the atmospheric air. Thumb screw 106 is, in this instance, replaced by another thumb screw which is adapted to adjust the pressure of the spring 'on the membrane.
As soon as liquid reactant 102 reaches electrode 115 the decomposition reaction proceeds on the catalyst of the electrode after a certain delay, which reaction causes the formation of oxygen gas whereby the liquid reactant present in capillary 116 is forced back by the resulting gas. In this way the decomposition reaction at the electrode is interrupted. If the pressure of the resulting cushion of gas at electrode 115 is designated as pg, and the gas pressure in gas chambers 108 and 112 of container 101 is designated as pv, and the hydrostatic pressure of the liquid reactant is designated as ph, then the following holds true:
FFA/+1111 (as long as no consumption of gas occurs).
Electrode 115 functions when pressure pl,I corresponds to the operating pressure of the electrode. If the fuel cell is subjected to an electrical load, then pressure pg falls due to the consumption of gas and liquid reactant 102 is caused to flow in the direction of electrode 115. As soon as the volume of gas which is between liquid reactant 102 and electrode 115 is consumed then liquid reactant 102 begins to moisten the catalytically active layer of the electrode. Since the decomposition reaction does not take place spontaneously and, on the other hand, since the velocity of the ow of the liquid reactant to the electrode continues as a result of the continuous flow of the electric load even after the initial [wetting of the electrode, more liquid reactant ows and therefore more gas is steadily evolved until the point is reached Where more gas is being evolved by the decomposition of the liquid at the electrode than is being consumed by the electrical load. Under these conditions an excess of gas arises fwhich leads to an increase in gas pressure. lIn order to avoid the situation wherein under a constant consumption of gas the pressure of the entire system continues to increase in the manner described above, rising mains 114 and 117, which are provided in the device of FIG. 7, have been found necessary. The liquid coreactant, which is supplied from container 101, must be continuously supplied through rising main 114 from the bottom thereof to the top. The same holds true for liquid reactant supplied over line 118 to rising main 117, such as a solution of sodium borohydride for decomposition on hydrogen gas diffusion electrode 123 with the attendant evolution of hydrogen gas. The rising mains are so dimensioned that they can completely absorb any excess volume of gas arising during the decomposition of the decomposable gas yielding liquids on the respective electrodes under the prevailing electrical load conditions. In this way the rise in pressure which is created by such decomposition is caused to regress since the resulting excess volume of gas is used irst before the decomposable liquid coreactant can `again Wet the electrode, whereupon the above described liquid supply and gas generation process is repeated again. A completely analogous regulation of the supply of liquid takes place if the fuel cell element 124 shown in FIG. 7 is operated as a gas generator. If, for example, a solution of hydrogen peroxide is supplied over line 113 and a sodium borohydride solution is supplied over line 11=8 then oxygen that is generated on catalytically active layer can be supplied over gas line 120 by opening valve 119 and hydrogen that is generated on catalytically active layer 123 can be supplied over line 122 by opening valve 121. Electrolyte 125 is used in the electrochemical reactions.
FIG. 8 shows another embodiment of the devices of the present invention for the automatic supply of liquid 202 from storage container 201 to the decomposition catalyst in layer 215 of fuel cell element 216 over supply line 213 and rising main 214. The device of the present invention is connected by by gas line 230 to open gas area 208 which is above the level of liquid 202 in container 201. The sealed pressure chamber 239 is formed by the lower part of container 231 and by gas impermeable elastic membrane or diaphragm 232 which cats to form and seal the upper portion of chamber 239. Porous absorbent body or wick 233 is located in sealed chamber 239 and above this absorbent body or wick 233 there is positioned a catalyst body 234 which is xedly connected to movable membrane 232. In the upper portion of container 231 there is located an internally threaded shaft 235, threaded bolt 236 and a pressure plate 237 and by means of turning nut 236 and forcing down plate 237 tension is applied to spring 238 and, in turn, to membrane 232, which tension corresponds to the desired pressure for the delivery gas in chamber 239. If the pressure of the delivery gas lies below the desired delivery pressure then catalyst body 234 is pressed down on porous body 233. Porous body 233 is filled with decomposable gas yielding liquid before initiating the operation of the device through an orifice which is not shown. As a catalyst there can be used a sintered nickel body, for example, for the decomposition of a 16% by Weight solution of sodium borohydride in 6 N aqueous sodium hydroxide for the generation of hydrogen gas. If the liquid 202 which is to be supplied to electrode 215 is also a 16% by weight solution of sodium borohydride in 6 N aqueous sodium hydroxide then sucking body 233 can also be filled from the liquid in container 201 by tipping the device so as to allow liquid 202 to flow through line 230 onto sucking body 233.
Obviously the device of FIG. 8 can also be so constructed that absorbent body 233 is made movable and catalyst body 234 is permanently positioned.
As a result of the supplying of liquid 202 from storage container 201 to electrode 215 the volume of open gas chamber 208 above the level of liquid 202 is increased and the gas pressure, therefore, in the entire area encompassing gas chambers 208 and 239 and gas line 230 is correspondingly decreased so that membrane 232, which had been raised while the desired gas pressure was in chamber 239, and catalyst body 234 are again pushed down against body 233 by spring 238. By a choice of a suitable dimensioning of the volume of gas that is to be employed in areas 239 and 208 it is possible to continuously provide in the devices of the present invention 1 1 that only relatively slight uctuations of the delivery gas pressure occur.
A continuously regulatable gas or electric current supply under constant pressure is possible as long as the velocity of the decomposition of the liquid coreactants on catalytically active gas dilfusion electrodes 215 and 223, as well as the possible speed of supply of the liquid to the electrodes, is greater than the corresponding consumption of gas and electric current.
1. In a gas generating installation comprising:
a container to contain a supply of gas yielding decomposable liquid,
a gas space above the level of said liquid,
a main decomposer having a catalyst adapted to catalytically decompose said liquid and thus provide for the generation of gas therefrom,
a first liquid supply passage means adapted to supply said liquid from said container to said main decomposer,
an auxiliary decomposer having a catalyst adapted to catalytically decompose said liquid to provide for generation of gas pressure,
a irst gas supply passage means adapted to convey gas from said auxiliary decomposer to said gas space so as to provide a desired supply of gas pressure therein,
second liquid supply passage means adapted to supply liquid from said container to said auxiliary decomposer,
and pressure operated automatic liquid supply control means adapted to control the supply of liquid to said auxiliary decomposer to limit the generation of gas in said auxiliary decomposer.
2. An installation as in claim 1 in which said liquid supply control means includes a irst control valve in said second liquid supply passage means, a sensing means to sense the gas pressure in said gas space adapted to operate said control valve according to the gas pressure in said gas space in order to release a supply of said liquid to said auxiliary decomposer when the gas pressure in said gas space falls below a predetermined supply.
3. An installation as in claim 2 in which said pressure difference sensing means adapted to control said rst control valve is actuated by a difference in pressure between the gas pressure in said gas space and a reference pressure external of said gas space.
4. An installation as in claim 1 in which said first gas supply passage means further includes a buffer Volume means.
5. An installation as in claim 1 in which said rst liquid supply passage means comprises a second control valve for said liquid which is adapted to be controlled by the gas pressure in said gas space and to release a supply of said liquid to said main decomposer when the gas pressure in said gas space exceeds a predetermined supply pressure.
6. An installation as in claim 5 further including second gas passage means for conveying gas from said main decomposer to a gas consuming device and said second gas line means comprises buffer volume means.
7. An installation as in claim 1 in which said first liquid supply passage means further comprises rising main means.
8. An installation as in claim 1 in which said main decomposer is a power cell.
9. An installation as in claim 1 in which said liquid supply control means comprises a first valve for said gas in said iirst gas supply passage means which is adapted to be controlled by the pressure of gas generated by said auxiliary decomposer and thereby control the pressure of gas in said gas space and thus control the supply pressure of said liquid to said auxiliary decomposer.
10. An installation as in claim 9 in which said second liquid supply passage means comprises rising main means.
11. An installation as in claim 10 in which said second 12 liquid supply passage means further comprises means throttling the flow of liquid therethrough.
12. An installation as in claim 1 in which said auxiliary decomposer is positioned within said container above the level of decomposable liquid therein and said second liquid supply passage means comprises a wick adapted to absorb said liquid and supply it to said auxiliary decomposer.
13. An installation as in claim 12 in which said pres surized liquid supply control means comprises a flexible membrane to which said auxiliary decomposer catalyst is rigidly attached and said exible membrane is adapted to being exed by variations in gas pressure in said gas space to bring said auxiliary decomposer catalyst into contact with said wick when said flexible membrane is exed in one direction and to interrupt catalyst contact with said wick within said auxiliary decomposer when said flexible membrane is fixed in the opposite direction.
14. An installation as in claim 1 in which said auxiliary decomposer is positioned outside of, and below the base of said container, and said catalyst is mounted on a movable shaft which is adapted to being raised and lowered through the base of said container, the base of said container having said liquid supply passage means incorporated therein for supplying decomposable liquid to said auxiliary decomposer from said container when said shaft is raised, said shaft having a valve head adapted to seal said liquid supply passage means when said shaft is lowered, and said pressurized liquid supply control means comprising a flexible membrane upon which said auxiliary decomposer rests and said flexible membrane is adapted t0 be tiexed by variations in gas pressure in said gas space and to raise and lower said auxiliary decomposer upon being flexed.
15. An installation as in claim 1 in which said auxiliary decomposer and said pressurized liquid supply control means are positioned within said container and said pressurized liquid supply control means comprises a tlexible membrane adapted to be flexed upwards and downwards and a valve head joined by a rigid connecting rod to said membrane, said valve head being adapted to cover and enclose said catalyst and thereby prevent liquid from contacting said catalyst in said auxiliary decomposer when sadi valve head is moved toward said catalyst by flexing of said flexible membrane under an increase in pressure and to uncover said catalyst to thereby allow access of liquid in said container to said catalyst when said valve head is raised by flexing of said exible membrane under the influence of a decreased pressure, one side of the surface of said exible membrane being in communication with the liquid in said container and the other side of the surface of said flexible membrane being subject to a predetermined exing pressure, so that differences in the pressure between the gas pressure in said gas space and said predetermined flexing pressure will cause the exing of said flexible membrane to cause a raising or lowering of said valve head.
16. An installation as in claim 1 in which said auxiliary decomposer is positioned outside said container and above a. supply of decomposable liquid and said pressurized liquid supply control means comprises a movable member adapted to being moved upwards and downwards and to which movable member said auxiliary decomposer catalyst is rigidly attached, one side of said movable member being subjected to a pressure from outside said gas area and the other side of said movable member being subject to the pressure within said gas area whereupon differences in suc-h pressures cause a movement of said movable member and said auxiliary decomposer catalyst upwards and downwards and thus cause an interruptable contact of said auxiliary decomposer catalyst with said supply of decomposable liquid.
17. In combination with a container for a liquid that is decomposable to evolve a gas by contact with a catalyst in which the container is provided With a bottom connection for withdrawing said liquid, the top of said container dening a gastight space to hold gas under a predetermined pressure so that the liquid may be withdrawn from said bottom connection: an auxiliary decomposer forming a gas supply means to add gas to said top of said container, said auxiliary decomposer including a chamber, a catalyst in said chamber, means to supply decomposable liquid to said chamber, and gas passage means from said chamber t0 supply gas generated by contact of said liquid with said catalyst to said top of the container; and means operated by a difference of the pressure in said chamber which is connected to the top of said Container and a selected other pressure, said means operated by a diierence of the pressures being operable to bring said liquid and said catalyst in said chamber into contact with each other to decompose said liquid to generate gas when the pressure in said container and said chamber falls below a predetermined pressure in the top of the container compared with the selected pressure, and preventing contact between said liquid and catalyst when the pressure in said container and said chamber rises to a higher preselected pressure compared to said selected pressure.
18. In combination with a container for a liquid that is decomposable to evolve a gas by contact with a catalyst in which the container is provided with a bottom connection for withdrawing said liquid, the top of said container delining a gastight space to hold gas under a predetermined pressure so that the liquid may be withdrawn from said bottom connection: an auxiliary decomposer forming a gas supply means connected operatively to said container to deliver additional gas to said container when the pressure in said container drops, said auxiliary decomposer comprising a chamber having a Wick element providing a source of decomposable liquid, and having a catalyst therein, and incorporating a control means including a diaphragm means operated by the pressure within said chamber on one side, and a selected pressure on the other side to bring said catalyst intoy Contact with said decomposable liquid in said wick element when the pressure in said chamber decreases below said selected pressure and to prevent contact of said catalyst with said Wick element and so with said decomposable liquid when said pressure increases.
References Cited UNITED STATES PATENTS 868,487 10/ 1907 Rosengarten 10B-234 2,258,299 10/ 1941 Miller 103-240 2,373,006 4/ 1945 Baker 23-282X 2,658,819 11/1953 Formwalt 23-282X 2,892,416 6/ 1959 Alexander 103-234 ALLEN B. CURTIS, Primary Examiner U.S. Cl. X.R.
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|U.S. Classification||429/416, 422/211, 417/65, 422/106, 417/120, 417/118, 429/513, 422/510|
|International Classification||H01M8/06, B01J8/02|
|Cooperative Classification||Y02E60/50, H01M8/0606, B01J8/0278|
|European Classification||B01J8/02F, H01M8/06B|