Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
2000-01-20
2001-05-22
Bell, Bruce F. (Department: 1741)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S253000, C204S257000
Reexamination Certificate
active
06235168
ABSTRACT:
This invention relates to an electrolytic cell and in particular, but not exclusively, an electrolytic cell for the production of chlorine gas by electrolysis of hydrochloric acid.
BACKGROUND OF THE INVENTION
A known design of such a cell is a series of planar electrodes suspended in a circulating electrolyte across which a voltage is applied. A membrane is supported to cover each electrode to provide separation of the hydrogen and chlorine gas produced by the electrolysis of the electrolyte, which gases are then separately extracted from the cell.
The heat produced by the electrolysis process is removed from the cell by the circulation of the electrolyte but will still subject the cell components to a range of operating temperatures in a given work cycle.
Such a stack of electrode/membrane components has been formed by stacking a series of frames interposed between the electrodes and membranes to form sealed interfaces with them, and to form common manifolds for transporting the electrolyte to and from the electrodes and membranes of the cell sealing being obtained by applying pressure to the stack by clamping them together. A disadvantage of this approach is that all the seals are, in effect, fully formed at the same time as the pressure is applied to the stack and failure of one seal can mean having to reassemble a large part or all of the structure. Particular difficulty is associated with the formation of the manifold seals a construction requires the components to be manufactured to close dimensional tolerances. Thermal cycling also introduces physical stresses that can prejudice seal security during use of the cell.
Such cells include one or more large-area, thin membranes with no ability to support themselves which must be supported in the cell so as to allow flow through the membrane but not to by-pass it. Provision must also be made to provide flow paths for electrolytes to both sides of the membrane which ensure that the flow of the electrolytes is evenly spread across the area of the membranes and so the area of the electrodes of the cell.
SUMMARY OF THE INVENTION
The present invention seeks to provide a membrane-supporting frame assembly for an electrolytic cell which is readily assembled as part of an electrolytic cell, more easily and reliably sealable in the cell and with simplified electrolyte flow distribution arrangement. Accordingly, the present invention provides a membrane-supporting frame assembly including a frame which has an aperture having a stepped sidewall, including a peripheral sealing ledge in which is set a seal, a membrane whose periphery is urged against the seal by a sub-frame mounted in the aperture, the sub-frame being provided with vertically extending stand-offs at each corner so as to define a cavity partially bounded by the frame and sub-frame at the top of bottom of the aperture, the top and bottom edges of the sub-frame being provided with a plurality of through-holes, and at least one through-hole through the frame to provide fluid communication through the frame to the cavities.
On assembly of the membrane-supporting frame assembly in an electrolytic cell, electrode plates sandwich the frame assembly pressing the sub-frame onto the sealing ledge to seal the periphery of the membrane to the sealing ledge. At the same time the sub-frame defines cavities top and bottom for the collection and distribution of electrolyte with an even flow pattern with simple drillings in the sub-frame with the flow path through the frame being reduced to a single entry and exit port thereby providing savings in both material and machining costs compared to designs requiring multiple through-holes through the frame.
Conveniently, the sub-frame is provided with a plurality of membrane supports which are engagable with the membrane which suspend the membrane on the frame prior to mounting of the sub-frame in the aperture. Preferably, the sub-frame is engagable with the membrane supports to positively locate the sub-frame in the aperture.
The frame preferably includes a continuous seal circumscribing the outside of the aperture at the front and back of the frame, most preferably these continuous seals are aligned.
The sub-frame may include a vertical cross-beam to provide support to the membrane in the assembled cell.
REFERENCES:
patent: 4233146 (1980-11-01), Rothmayer et al.
patent: 4886586 (1989-12-01), Morris
patent: 4898653 (1990-02-01), Morris
patent: 4923582 (1990-05-01), Abrahamson et al.
patent: 6117287 (2000-09-01), Molter et al.
patent: 0056503 (1982-07-01), None
patent: 2280433 (1976-02-01), None
patent: 8100863 (1981-04-01), None
Routh Julian Dudley
Strutt Ivan
Bell Bruce F.
Capital Controls Ltd.
Engellenner Thomas J.
Nguyen Tram Anh T.
Nutter & McClennen & Fish LLP
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