Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
2001-06-01
2003-04-29
Valentine, Donald R. (Department: 1741)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S270000, C204S279000
Reexamination Certificate
active
06554978
ABSTRACT:
The present invention concerns a high pressure electrolyser module of the filter-press type for the electrolytic production of gasses and further concerns an electrolyser comprising said module.
Electrolysers of the filter-press type comprise a so-called electrolyser module and a number of peripheric items such as degassing chambers, a water supply unit and possibly a transformer/rectifier and the necessary piping to connect the various parts of the electrolyser. An electrolyser module comprises a series of stacked electrolysis chambers, alternately cathodic and anodic. Each chamber holds either one or more anodes or cathodes. The electrolysis chambers are separated from one another by selectively permeable membranes or diaphragms. A combination of a cathodic and an anodic chamber form an electrolysis cell. In each chamber, the electrodes are mounted vertically, preferably in close contact with the membranes. This can be accomplished, for example, by pressing the membrane between the electrodes. Membranes that are particularly suited for this purpose have been described in EP-A-0 232 923.
The electrolysis chambers are hold together by a frame which forms the outer wall of the electrolyser and may take a variety of shapes, polygonal, eg. square, rectangular, or circular. In the latter instance the frame is in fact ring or cylinder shaped. The separating membrane is fixed to the frame together with the electrodes. The frames are made of a material that is inert to the electrolyte and can be made for example of metal, covered by a suitable non-conducting layer, or can be made of a suitable inert non-conducting material such as synthetic. A frame made of metal covered by a flexible vulcanizable material is known from WO-97/00979.
In each electrolysis chamber the electrodes have to be linked by a suitable conductor. In a particular embodiment this can be accomplished by contacting the electrode with a metal woven sheet which in turn is contacted with a metal plate that is mounted in the frame, said plate being referred to in the art as bipolar plate.
The gas that is generated is lead to a degassing chamber, usually placed above the electrolyser unit, where the gas is collected and separated off the electrolyte entrained with the gas. The de-gassed electrolyte is recycled back to the electrolysis chambers and the gas that is collected can be pressurized and stored in suitable pressure tanks. The electrolysis chambers may be connected to outer tubes leading to or coming from the de-gassing chamber for respectively the circulation of the generated gasses or of electrolyte.
Or the electrolysis chamber frames may have suitable conduits at their top side and at their bottom side. The top conduit is meant to evacuate the gas-electrolyte mixture that is generated during electrolysis and the bottom conduit allows the entrance of electrolyte. The gas-electrolyte mixture that is generated is pumped though the upper conduit to a tube leading to the de-gassing unit from which the de-gassed electrolyte is pumped back to the bottom conduit in the fame from which it enters the electrolysis chambers.
Filter-press electrolysers have been described in EP-A-137,936 and in EP-A-56,759. U.S. Pat. No. 5,139,635 for example describes gas electrolysers of the filter-press type comprising a vertical stack of electrolysis chambers connected to a degassing chamber.
Hence the art-known gas electrolysers of the filter-press type are complex arrangements involving several peripheral items such as pumps, tanks and piping, and therefore comprise a multitude of moving parts, requiring supervision, checking and maintenance. Thus, a more simplified arrangement with no or fewer moving parts would be a desirable goal to achieve in that it would require almost no or limited maintenance.
The high pressure electrolysers according to the present invention aim at avoiding moving parts and at the same time allowing the elimination of peripheral equipment resulting in a more simplified arrangement of the electrolyser, requiring less supervision and maintenance.
The present invention concerns an electrolyser which functions under high pressure thus yielding gasses that are under increased pressure and that can be stored directly, without the extra step of compressing. In a further aspect, the electrolysers according to the present invention allow circulation of the electrolyte in the electrolysers and the degassing chamber by spontaneous convection, i.e. without pumping. In still a further aspect, there is provided a supply system to replace the water that is consumed during the course of the electrolysis with minimal moving parts using the pressure of the gas that is liberated in the electrolyser module as driving force.
In addition to the above-mentioned advantages, the high pressure electrolysers of the invention can be allowed to cool to room temperature when they are not functioning. Art-known electrolysers typically function at elevated temperatures e.g. at 70° C., and show leakage when allowed to cool. Consequently, even when out of function, they have to be kept at this elevated temperature.
Thus in one aspect, the present invention is concerned with a high pressure electolyser module comprising a series of stacked electrolysis chambers and each chamber being held within two ring-shaped holding frames, said frames having openings that form conduits for the supply of electrolyte and the removal of gas that is generated, wherein
(1) the connecting surface of the ring-shaped frame has one or more elevations and/or one or more depressions in such manner that an elevation of a ring fits in a depression of a neighboring ring;
(2) a gasket is placed in between said elevation in a particular ring and said depression of a neighboring ring;
(3) the distance between the rim of said conduit and the outer wall of the opening forming the gas or electrolyte conduit, and the outer wall of the ring-shaped fine is such that the material can endure a pressure gradient of at least 200 bar.
In a further aspect the invention concerns an electrolyser comprising an electrolyser module as described herein.
The gasses that are generated in the electrolyser module contain electrolyte and typically a gas/electrolyte mixture is generated in the module usually forming a foam mixture. This is lead to a degassing chamber where gas and electrolyte are separated. As used herein, the term gas that is generated and similar terms, when used in relation to gas that is generated in the electrolyser module until it is separated in the degassing chambers, is meant to comprise the afore mentioned gas/electrolyte mixture.
The electrolysis clambers in the high-pressure electrolyser modules according to the invention contain one or more, preferably two electrodes placed vertically in the chamber. The electrodes are made of art-known materials that are inert to the electrolyte. The chambers arm separated by a semi-permeable membrane or diaphragm and where two electrodes per chamber are used, the electrodes are preferably pressed against the membrane or diaphragm and connected by a suitable conductor. In a preferred arrangement, a bipolar plate is placed between the two electrodes and electric contact is made by placing two metallic woven sheets between each electrode.
The various parts of each electrolysis chamber are held in a ring-shaped frame that forms the outer wall of the electrolysis chamber. The shape and dimensions of this frame are essential features to assure high pressure electrolysis on the one hand and spontaneous convection of the electrolyte on the other.
In a particular embodiment, the electrolysis chambers are placed between two flanges, preferably made of metal, mounted at each side of the stack of electrolysis chambers. The flanges are hold together with several tie rods placed at the outside of the electrolyser module and linking the flanges fitted with holds to turn tight to press the electrolysis chambers together.
In a further aspect, the present invention provides a ring-shaped frame wherein the connecting surface of said ring has one or
Valentine Donald R.
Vandenborre Technologies NV
Woodbridge & Associates P.C.
Woodbridge Esq. Richard C.
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