ELECTROLYSER

Field of the Invention

This invention relates to an assembly for securing and compressing a stack electrolysis cell.

Background of the Invention

Electrolysis cells have long been used to generate hydrogen from water, generally in the form of an electrolyte solution.

In a particular electrolysis cell, porous anode and cathode plates are arranged in a stack with an electrolyte permeable-gas impermeable membrane placed between each anode and cathode pair (for example as described in PCT Publication No.

WO2004/020701 and Canadian Patent Application No. 2,400,775 ELECTROLYZER, Helmke et al., both of which are incorporated herein by reference). By providing separate channels to each of the anodes and cathodes, the product gases generated at each of the anodes and cathodes may be separately output from the cell. Electrolyte is circulated through the porous anodes and cathodes. In order to circulate the electrolyte and provide an outlet for the product gases, the channels are created by cutting holes or slots in each plate that align when the plates are stacked. The aligned holes and slots form the channels to circulate electrolyte and provide for output of the product gases.

An advantageous method of manufacturing such a cell has been to stack the anode plates, cathode plates and membranes and encase the resulting stack in an electrolyte impermeable-gas impermeable membrane such as epoxy resin. The epoxy is used to assist in sealing the edges of the plates and to secure the plates in an aligned stack. The resultant electrolyser may thus be comprised of multiple electrolysis cells encased in an epoxy resin casing. Ports may be provided through the epoxy casing to permit circulation of electrolyte and output of the product gases. Electricity may be provided to the cells via an electrical connection that extends out of the epoxy.

While this method of creating an electrolyser from a stack of anode and cathode plates has been successful, it does suffer from some limitations. The resulting electrolysers

are limited in their gas output rate as elevated internal pressures cause the epoxy to swell and allow the plates to separate. Once the plates separate, even by a relatively small amount, the channels may no longer be completely separate. Even a small breakdown in channel integrity may result in co-mingling of product gases and electrolyte, reducing output from the electrolyser.

It would be advantageous to provide for a stack cell and a method of manufacturing such a stack cell that alleviates these limitations.

Brief Description of the Drawings

In drawings which illustrate embodiments of the invention by way of example only:

Figure IA is an exploded perspective view of a stack of electrolysis plates.

Figure IB is a perspective view of the assembled stack of electrolysis plates of Figure Ia.

Figure 2 perspective view of an assembled electrolyser according to an embodiment of the invention.

Figure 3 is a cross-sectional elevation of the electrolyser of Figure 2.

Detailed Description of the Invention

The invention provides an electrolyser comprising a stack of electrolysis plates, the plates being maintained in substantially parallel alignment, and a press for applying a compressive force transversely to the stack, to compress the stack between opposed faces of the cell, the press comprising a front face, a compression support plate fixed in position relative to the front face and spaced from the front face, a moving platen, the stack being disposed between the platen and the front face, and a compression member for applying a compressive force to the platen such that the platen applies a transverse compressive force substantially uniformly over a face of the stack, whereby the press maintains the electrolysis plates in substantially parallel alignment when the electrolyser is in operation.

In farther embodiments of the electrolyser of the invention: The compression member comprises a spring bearing against the platen; the spring is actuated by a disk threadedly secured to the compression support plate and bearing against the spring; the spring is disposed in a recess disposed on a face of the platen; the spring surrounds a hub disposed in the recess; the hub surrounds a key; the front face is formed by a jacket; the front face is formed integrally with side faces of the jacket; and/or the compression support plate is affixed to the side walls.

The invention further provides a method of stabilising an electrolyser comprising a stack of electrolysis plates, the electrolysis plates being in substantially parallel alignment, the method comprising the steps of: a. locating the stack of electrolysis plates in a press comprising a front face and a compression support plate fixed in position relative to the front face; and b. rotating a threaded compression member to apply a compressive force to a platen bearing against the stack, such that the platen applies a transverse compressive force substantially uniformly over a face of the stack; whereby the press maintains the electrolysis plates in substantially parallel alignment when the electrolyser is in operation.

Figure IA illustrates an exploded view of a stack 10 of electrolysis plates 12 comprising alternating porous anode and cathode plates with an electrolyte permeable- gas impermeable membrane 12a between each anode-cathode pair.

The electrolysis plates 12 may be assembled into the stack 10 having positive and negative terminals 11, 13, respectively, as illustrated in figure IB, and encased in a sealant such as epoxy, a silicone compound or any other suitable sealant, to seal the edges of the plates and, in conjunction with the compression member described below, maintain the plates 12 in the stack 10 in precise parallel alignment within the electrolysis cell 20.

As more fully described in WO2004/020701 and CA2,400,775, which are incorporated herein by reference, slots in the plates align when stacked to form channels through the stack 10. The channels permit circulation of electrolyte through the stack 10 and output of the product gases from the cell 20. A first product gas (in

the case of the electrolysis cell shown, one of hydrogen and oxygen) is output from one or more first gas output ports 22, a second product gas (in the case of the electrolysis cell shown, the other of hydrogen and oxygen) is output from one or more second gas output ports 24, electrolyte is input through one or more electrolyte input ports 28, and electrolyte is output through a set of one or more electrolyte output ports 26, as illustrated in Figures IB and 2. As will be appreciated, the placement and number of ports may vary from the embodiment illustrated in Figures IB and 2. Also shown is an output 29 for a thermocouple, for monitoring the temperature of the electrolysis cell 20.

During operation of the cell 20, a current supplied to electrodes 11, 13 results in hydrogen and oxygen gas being generated in the electrolysis plates 12 of the cell 20. The generation of these product gases increases the internal pressure of the cell 20, causing the product gases to egress through the first and second product gas ports 22, 24. In order to increase the gas output of the cell 20, a higher electrical input may be supplied to the electrodes 11, 13. The higher electrical input results in the product gases being generated more quickly, the internal pressure of the cell 20 increasing and a higher flow rate of product gases from product gas ports 22, 24.

However, the higher electrical input increases the temperature of the stack 10 with attendant increased thermal expansion of the stack 10. Any separation of the plates 12 within the stack 10 (either by spreading or by loss of parallel alignment) consequent to thermal expansion causes loss of output gases and therefore reduces the efficiency of the cell 20.

It has been found that the electrolysis cell 20 may be operated at higher levels of gas output, and consequent higher internal operating pressures, if a substantially even compressive force is applied to opposite faces of the cell 20 and maintained during operation, hi the preferred embodiment the compression member accommodates thermal expansion of the encased stack 10 while under the compressive force.

In the embodiment illustrated, the invention provides a press for securing the electrolyser containing the stack 10 of electrolysis plates 12, comprising a

compression plate for compressing the encased stack 10 against the jacket 30 of the cell 20, and a disk spring 50 which can be adjusted to set a rest compression and which allows the compression plate to move as the stack 10 expands while maintaining a relatively constant pressure against the encased stack 10 as the cell 20 heats up.

As illustrated in Figures 2 and 3, the stack 10 is contained within a jacket 30 constructed of a sturdy, rigid material such as stainless steel, carbon fibre, plastic (for example polyetheretherketon (PEEK), PVC, CPVC), or other suitable material. As shown the jacket 30 is bent to form the front face 30a and sides 30b, however these may be formed as separate components if desired. The electrodes 11, 13 protrude through one end plate 30c and another end plate 30d seals the opposite end of the cell 20. The ends 30c, 30d may be bolted or otherwise suitably affixed to the front face and sides 30a, 30b of the jacket 30.

A compression platen 32 is movably disposed opposite to the face 30a, preferably nested within the jacket 30 as shown in Figure 3. The compression platen 32 is similarly formed from a sturdy, rigid material and spans the length and width of the stack 10.

A compression member comprising a disk spring 50 is disposed generally centrally along the platen 32, for applying a compressive force to the stack 10. The disk spring 50 may be mounted in a recess 32a in the outer face of the platen 32, and surrounds a hub 52 and key 54 which interlocks with a rotatable disk 56 threadedly engaged to an opening 42 through a compression support plate 40, the hub 52 maintaining the spring 50 in axial alignment beneath the disk 56.

The compression support plate 40 is in turn bolted to the jacket 30 (as seen in Figure 2). The compression support plate 40 and jacket 30 thus form a press frame containing disk spring 50 in contact with moving platen 32.

Optionally an elastomer layer 46 may be positioned between the stack 10 and the face 30a of the electrolysis cell 20, serving as a thermal insulator and allow for any imperfections between face 30a and the facing side of the electrolysis cell 20. The elastomer layer 46 may for example be composed of Ethylene Propylene Dieene Monomer, but any suitable thermal insulating material may be used if desired.

The cell 20 is assembled by inserting the encased stack 10 into the jacket (after inserting a thermally insulating layer 46, if desired), and inserting the platen 32 over the stack 10. The disk spring 50 is mounted in the recess 32a about the hub 52 and key 54, and the support plate 40 (with disk 56 threaded into opening 42) is bolted to the jacket 30.

After assembly of the cell 20, the disk 56 can be tightened to a desired torque, forcing platen 32 toward stack 10 and thus applying a uniform compression over the face of the stack 10 (the opposite face of the stack 10 bearing against the interior of face 30a of jacket 30, applying a uniform compression over the opposite face of the stack 10). This manner of compression is superior to conventional compression means such as corner bolts, because a single member can be adjusted to apply even compression over the entire face of the stack. Moreover, even if corner bolts could be tightened to supply an initial uniform compression, through constant expansion and contraction the compression will eventually become non-uniform and allow the plates 12 to come out of parallel alignment. Even the slightest loss of parallel alignment between the plates 12 will result in reduced efficiency of the cell 20, and substantial loss of parallel alignment will result in catastrophic failure of the cell 20.

In operation, as described in WO2004/020701 and CA2,400,775, which are incorporated herein by reference, slots in the plates 12 form channels (not shown) through the stack 10 which permit circulation of electrolyte through the stack 10 and output of the product gases from the cell 20. A current supplied to electrodes 11, 13 results in hydrogen and oxygen gas being generated in the electrolysis plates 12 of the cell 20 via electrolysis, as is well known. The generation of the product gases increases the internal pressure of the cell 20, causing the product gases to egress through the first and second product gas ports 22, 24. hi the case of the electrolysis

cell shown, hydrogen is output from first gas output port 22, and oxygen is output from second gas output port 24. Electrolyte is circulated through input port 28 and output port 26, ensuring a constant supply of electrolyte solution.

Increasing the electrical input results in the product gases being generated more quickly, the internal pressure of the cell 20 increasing and a higher flow rate of product gases from product gas ports 22, 24. However, it also results in greater thermal expansion of the stack 10. As the stack 10 expands transversely (relative to the plane parallel to the plates 12) the disk spring 50 yields to maintain a substantially constant compression against the stack 10. This not only prevents misalignment of the plates 12, but also reduces the risk of cracking of the epoxy encasement material. The compression remains uniform, because the pressure from disc spring 50 is applied generally centrally to the platen 32 over the area of the disk spring 50.

Various embodiments of the present invention having been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention. The invention includes all such variations and modifications.