US 2695874 A
Description (OCR text may contain errors)
Nov. 30, 1954 E. A. ZDAN PRESSURE REGULATING Filed Feb. 23, 1951 SKY 2,695,874 DEVICE FOR ELECTROLYTIC GAS GENERATIN G DIAPHRAGM CELLS 3 Sheets-Sheet l F/E. i
i I l 0 I I i 5 INVENTOR. ELJALD A. Z0 r-/sr Nov. 30, 1954 E. A. ZDANSKY PRESSURE REGULATING DEVICE FOR ELECTROLYTIC GAS GENERATING DIAPHRAGM CELLS s sheets-sheet 2 Filed Feb. 23, 1951 INVENTOR.
fi/Aw' A. ZDANSKY BY Nov. 30, 1954 E. A. ZDANSKY 2,695,874
PRESSURE REGULATING DEVICE FOR ELECTROLYTIC GAS GENERATING DIAPHRAGM CELLS Filed Feb. 25, 1951 3 Sheets-Sheet 3 I INVENTOR. EwALp l9. ZDH/YSKY United States Patent PRESSURE REGULATING DEVICE FOR ELECTRO- LYTIC GAS GENERATING DIAPHRAGM CELLS Ewald A. Zdansky, Monthey, Switzerland Application February 23, 1951, Serial No. 212,309
Claims priority, application Switzerland February 22, 195 0 6 Claims. (Cl. 204-258) This invention relates to pressure electrolysers and to the control means, used in connection with such electrolysers.
Especially, this invention concerns means ensuring an exactly maintained pressure compensation between the generating spaces for hydrogen and for oxygen which in the individual cells are separated from each other only by a permeable diaphragm. Such means must guarantee that the pressure difference existing between both sides of the diaphragm does not exceed 10-100 mm. water in order to obviate any intermingling of the gases by diffusion or mechanical breakdown of the diaphragm. In the case of a pressure electrolyser in which the working pressure may attain, e. g., 25 to 50 atmospheres gauge, such pressure differences are only a few tenths of one percent of the working pressure, and it is consequently obvious that all attempts hitherto to obtain pressure equalization by mechanical means, have failed to provide a satisfactory solution.
The invention refers to a novel device for controlling the pressures in a pressure electrolyzer, capable of eliminating all existing disadvantages and distinguished by great simplicity and reliability in operation. The invention utilizes the gas and liquid spaces of the two gas separators already provided in any electrolyzer, for hydrogen and oxygen respectively, as buffer chambers.
For this purpose, the aforesaid gas separators are constructed as intercommunicating vessels. This system is consequently in communication with the cells of the electrolyzer, by the gas collecting pipes and by the electrolyte reflux pipes, directly, in such manner that the pressure prevailing in the cells is approximately the same as that in the gas separators. The buffer effect is obtained in the manner that pressure equalization between the anode and cathode spaces, is effected exclusively through this system of intercommunicating vessels. The greater the total volume of the system, consequently, the greater and more uniform is the resulting buffer effect. Suitably, therefore, extremely large spaces are used, far exceeding the volumes necessary for separation of the gases. Thus, e. g., in the case of an electrolyzer built up in the manner of a filter press of a number of narrow cells, the volume of this system is suitably made equal to more than 10% of the total electrolyte volume of the connected cell assembly. In order to obtain the greatest possible volume of liquid in the system and improve the buffer effect, the gas separators communicating with the electrolyzer are filled with electrolyte to such a degree that the liquid level during operation is maintained in both separators at approximately half their height. The gas separators are provided with windows through which the liquid level can be observed. An essential feature of the principle of the invention is further that the discharge of gas from one of the gas separators is effected by means of a pressure-controlled valve, while the gas discharge from the other gas separator is effected through a valve which is controlled by the level of the liquid in this particular gas separator.
The method according to the invention, of obtaining the required pressure equalization by means of the arrangement just described, consists in that the gas discharge from the one gas separator through a pressurecontrolled valve is effected in such manner that the working pressure is maintained at a preset mean value, e. g. about 30 atmospheres, while the gas discharge from the other gas separator through a level-controlled valve is adjusted in such manner that the liquid level in this Patented Nov. 30, 1954 gas separator is continuously maintained approximately at a mean value (half the depth of the separator).
In this manner equalization is controlled quite independently of the absolute pressure prevailing in the electrolyzer by virtue of the fact that the level-controlled gas discharge acts to close the pressure-controlled valve as soon as any quantity of liquid is withdrawn from the other separator vessel. The true pressure difference between the hydrogen and the oxygen sides is thus always controlled by the difference in liquid level between the two separator vessels, and amounts to only a few centimetres water column.
In practical operation the level-controlled valve maintains the liquid level in the particular gas separator always at an approximately equal height. This arrangement fulfills the requirement of maintaining a low differential pressure in the cells, since, as already explained, a pressure dilference can only arise in the cell spaces when the level difference between the two gas separator vessels fluctuates.
As experiments have, however, shown, the proposed use according to the invention of especially large volumes of electrolyte in the intercommunicating vessels forming the gas separators, ensures proper pressure equalization not only in the presence of small pressure differences, but equally with quite considerable gas losses occurring suddenly owing to leaks in the system or irregularities in the operation of the valves. With the system of controlling valves employed, of exceptional simplicity and reliability compared with pressure electrolyzer valves generally, complete protection is given against all operating faults or accidents without the need for subsidiary quick-release governors or the like.
The unexpectedly good efliciency of the pressure equalization is explained by the fact that even gas losses of high atmospheric volume, causing an abrupt diminution of the absolute pressure by several atmospheres, only produce a small variation of the liquid levels in the gas separators, and such losses consequently produce only small variations of the electrolyte level and therefore of the pressure differences in the cells.
The control on the pressure-regulation side is effected by means of a sensitive differential valve, While on the side of the level-controlled gas separator, alternative possibilities of regulation are available; e. g., the discharge valve can be controlled by a float in the gas separator. Since, however, electrolysis under pressure requires high operational reliability, and it is desirable to exclude delicate control elements as far as possible, such level control can be operated also by an optical probe or scanner. Another method of controlling the liquid level consists in that-on the assumption of uniform current loading a finely-adjustable discharge valve is preset by hand to a predetermined output volume. In such case, the liquid level in the particular gas separator is continuously maintained at approximately the same height, and only requires to be checked occasionally and adjusted by fine setting of the valve.
Further security against exceptional operational disturbances is afforded if each of the two gas separators is equipped with a high-pressure or low-pressure limit switch, in such manner that when the preset maximum value is exceeded or not attained, the working current is immediately switched off; and if necessary, safety valves caused to act.
The control device is particularly suitable for pressureoperated water electrolyzers working at pressures between 5 and 50 atmospheres, suitably 30 atmospheres, and which are constructed in the manner of filter presses of an assembly of narrow cells, in such manner that the volume of contained electrolyte is small.
The system of intercommunicating gas separators is suitably arranged above the electrolyzer cell assembly and combined with the latter in a structural unit. In accordance with the invention the system can be arranged to act as a common controlling device for a number of connected pressure electrolyzers.
The invention is explained below with reference to drawings representing examples of suitable arrangements,
0 in particular:
Fig. 1 shows a diagrammatic cross-section through a pressure electrolyzer and gas separators with built-in control device.
Fig. 2 shows a perspective view of a pressure electrolyzer and a section of a builtin, separate control device.
Fig. 3 shows a diagrammatic vertical section through a gas separator with electro-optical level control.
In accordance with Fig. 1, the two gas separators 2 and 3 are arranged above the electrolyzer proper 1, and are of greater than normal capacity, e. g. correspondingly about l15% of the volume of electrolyte in the cells; the electrolyte reflux pipes and 51 opening into these separators. At equal pressure, the vessels 2 and 3 each are about half-filled with electrolyte. The hydrogen collector pipe 4 and the oxygen collector pipe 6 from the cells, lead into the gas separators 2 and 3, delivering continuously during operation of the unit, a spray consisting of a mixture of the particular gas with hot electrolyte. In accordance with the invention, the two large gas separators 2 and 3 are interconnected by a U-tube of correspondingly large bore, which enters below the level of the electrolyte, thus forming a system of intercommunicating vessels.
The gas space of the gas separator 2 is connected through a pressure-controlled valve 8 with the hydrogen delivery pipe 9. This valve 8 may suitably be so adjusted that an approximately constant pressure of 2426 atmospheres is maintained continously in the gas separator 2 during operation. The gas space of the gas separator 3 is connected through a float-controlled valve 10 with the oxygen delivery pipe 11. Obviously, the electrolyte level can only be the same in both vessels 2 and 3, if the pressure in both vessels is the same. Should the pressure-controlled valve 8 at any time release an excess of hydrogen, thus causing the total pressure to drop, e. g., from 26 to 24 atmospheres, then, by virtue of the large capacity of the vessels 2 and 3, a displacement of liquid through the pipe 7, corresponding to the hydrostatic pressure difference Ap will suffice to compress the hydrogen in the space 2 sufliciently, while simultaneously the oxygen contained in the space 3 expands correspondingly, to restore a pressure condition in disequilibrium only by the insignificant differential Ap. It is only this differential pressure of a value of a few centimetres water, which is operative in the anode and cathode spaces of the cells, and is in practice negligible. Simultaneously, however, the consequent difference in level causes the level-controlled valve 10 to open, by which then, the pressure difference is speedily equalized. Thus, neither the valve 8 nor the valve 10, require to act with any high precision.
It is obvious that a control device of this nature can only be effective if the total volume of electrolyte circulating through the system is maintained constant, i. e. when the quantity of water expended in the electrolysis, is continuously renewed. It is in this regard possible to employ the control device according to the invention also for regulating the feed-water supply, in such manner that, as shown in Fig. 1, the gas separator 2 with the pressurecontrolled valve 8 is further equipped with a float-controlled feed-valvee. g. the float-controlled feed valve 12.
Instead of arranging the valves and their controlling elements directly inside the gas separators, it is similarly possible to fit them in a separate, e. g. water-filled, system of intercommunicating vessels, the gas spaces of which are connected with the gas spaces of the gas separators, by suitable pipes. An arrangement of this nature is shown in Fig. 2, in which identical elements are denoted by identical distinguishing numbers, as in Fig. 1.
The gas spaces of the two gas separators 2 and 3 are connected by pipes 13 and 14 to the control device, represented on a larger scale, and consisting of a U-tube 15, filled to the level cd with a liquid, e. g. water. The left-hand leg of this U-tube 15 is connected to the pressure-controlled valve 8, which delivers hydrogen into the pipe 9 as soon as the pressure in the communicating gas separator 2 exceeds a predetermined value depending on the previous setting or adjustment of the valve. The right-hand leg of the U-tube 15 is connected to the levelcontrolled valve 10, which is pressure relieved and controlled by a float, and which therefore discharges oxygen into the pipe 11 as soon as the liquid level in the right leg of the U-tube 15 falls owing to a pressure difference forming between the gas separators 2 and 3. The valve 10 can further be equipped with a spring-loaded warning contact 16, which it closes when the level of the liquid in the right leg of the U-tube 10 rises above a criti- 'valve 10a.
cal level (e. g. above the level e-f). The action is in all other respects identical with that of the example shown in Fig. 1.
The operational control obtainable with the regulating device according to the invention is particularly smooth and uniform if the valves are given a certain amount of lag or if a constant gas flow is caused to discharge from the gas separators 2 and 3 through by pass valves, approximately corresponding to the amount of gas evolved,
and the regulating valves therefore only have to deal with a residual gas volume. In such case, if the apparatus is suitably adjusted, the level-controlled valve will require to operate so seldom (as little as hourly), that it can even be manually actuated.
The liquid level in the gas separator 3 and the communicating right leg of the U-tube 15 can only rise if the valve 10 should stick when open, or if there should be a leak in the gas separator 3 or its communicating spaces and pipes, the gas loss from which exceeds the total gas output of the electrolyzer. In such exceptional circumstances, the warning contact 16 will be closed, and may simultaneously be arranged to switch off the working current.
A further rise in the liquid level of the gas separator 2 can only take place if the valve 10 should fail to close by the action of its float. This can be prevented, however, by suitably over-dimensioning the float in question, or also by the interposition of a second float valve set to a slightly higher level.
The decisive factor ensuring high operational reliability is, however, the buffer effect of the large capacities of the two gas separators 2 and 3, between which the electrolyte experiences the same fluctuations of level as the liquid in the U-tube 15: since in this system, already small pressure differences give rise to corresponding movements of the liquid, in such manner that without large fluctuations of the levels, relatively considerable gas volumes can be balanced. It is in practice, therefore, immaterial if the one or the other valve (8, 10) should occasionally blowoff too much or too little gas, since already a small difference of level in these capacious intercornmunicating vessels, will suffice to compensate such a loss.
In practice it is advisable to avoid fitting movable floats and systems of levels inside the gas separators filled with hot, highly-concentrated lye. For this purpose, the mechanical controls can be replaced, e. g. by the electrooptical level control system shown diagrammatically in Fig. 3, which in turn controls the valves.
The gas separator 3a, which is of the usual drum shape, is provided at one end with a pressure and lye-tight window 17. On to this window a narrow beam of light is projected from a source 18 at an angle of about 15 degrees, which impinges on the window immediately above the electrolyte level a-b which it is required to maintain. As long as the illuminated area of the window is above the level of the electrolyte, this light ray is totally reflected at the boundary between the window and the gas space, and is thus thrown back in the direction shown by broken lines on to a photo-electric cell 19. If, however, the level of the electrolyte rises sufficiently to cause the electrolyte to cover the illuminated area of the window 17, the ray penetrates in the direction shown by broken lines into the gas separator, and the illumination of the photoelectric cell is consequently interrupted. A relay 20 controlled by the photoelectric cell 19, acting through the conductors 21, then closes the level-controlled The feed-Water pump can be controlled analogously by a similar electro-optical control device arranged on the other gas separator 2.
The use of remote-controlled valves introduces the advantage that such valves can be sufficiently separated by pipes and liquid traps, from contact with the electrolyte spray, and any choking of the valves thus reliably avoided. As experiments have shown, the control device according to the present invention is in such conditions continuously and completely reliable.
If a number of pressure electrolyzers is required to be operated in a single plant or installation, their gas separators may be directly connected in parallel by separate pipe lines for hydrogen and oxygen, and if desired, a combined control device provided, suitably of the form shown in Fig. 2. .In such case the attainable pressure equalization is particularly uniform, since the effect of the electrolyte level displacements in the individual, communicating gas separator systems is summated and consequently pressure fluctuations occurring at one or the 5 other point in the combined system, are most efiectively compensated. In such case it is possible, for reasons of overall economy, to make the capacities of the individual gas separator systems somewhat smaller than would otherwise be necessary.
The above examples describe pressure electrolyzers for water. The pressure-equalization device according to the invention is, however, equally suitable for pressure electrolyzers of any other kind, e. g. for chlorine-alkali electrolyzers.
To the extent that in such case it is required to maintain some given pressure differential between the two gas spaces, the level control in the system of intercommunicating vessels may be so adjusted that any required pressure difference Ap is maintained.
What I claim is:
1. A pressure-operated electrolyzer apparatus comprising a plurality of pressure-resisting cells, each cell being separated by a diaphragm into an anode chamber and a cathode chamber; receptacle means defining two gas chambers adapted to be partially filled with a liquid, a tube system interconnecting the lower portions of said chambers, a first gas delivery tube system for delivering gas from said anode chambers to one of said gas chambers, and a second gas delivery tube system for delivering gas from said cathode chambers to the other of said gas chambers; a one way gas outlet valve connected to one of said gas chambers above said interconnecting tube system biased to release gas therefrom at pressures exceeding a predetermined value, and an independent second gas outlet valve connected to the other of said gas chambers above said interconnecting tube system; and liquid level actuated means for closing said second valve when the liquid level within its associated gas chamber exceeds a predetermined value and opening said second valve when the liquid level within its associated gas chamber falls below a predetermined value.
2. Apparatus as defined in claim 1, wherein the sum of the total volume of said two gas chambers exceeds 10% of the total volume of the electrolytic cells connected therewith, and wherein said liquid level actuated means has a floating portion and is mounted in said associated gas chamber with its floating portion arranged approximately at one half the height of said associated gas chamber.
3. Apparatus as defined in claim 1, wherein a reflux tube system communicating with said gas chamber is connected to the bottoms of the associated anode chambers and cathode chambers.
4. Apparatus as defined in claim 1, wherein a liquid inlet containing a float controlled valve is connected to the same said gas chamber which is connected to said pressure operated gas outlet valve.
5. Water electrolyzing apparatus as defined in claim 1 wherein said one way gas outlet valve is connected to the collecting gas chamber communicating with said cathode chambers and wherein said independent gas outlet valve is connected to the collecting gas chamber communicating with said anode chambers.
6. An apparatus as defined in claim 1, wherein an intermediate gas collecting container is arranged between each of said gas chambers and said anode and cathode chambers, respectively, and above said cells, and wherein said receptacle means and interconnecting tube system form parts of a U-shaped vessel arranged remote from said cells.
References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,094,728 Levin Apr. 28, 1914 1,230,803 Sebille June 19, 1917 1,273,357 Gougnard July 23, 1918 FOREIGN PATENTS Number Country Date 864,256 France Jan. 13, 1941