Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1998-04-08
1999-07-06
Bell, Bruce F.
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204252, C25B 1300
Patent
active
059193441
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/NO96/00152 filed Jun. 19, 1996.
BACKGROUND OF THE INVENTION
The present invention relates to diaphragm elements in an electrolytic filter press assembly comprising anode and cathode compartments separated by diaphragms. The diaphragm elements comprise a frame, openings for the flow of gas and liquids, respectively, a diaphragm secured to the frame, sealing means and insulating means.
The electrolytic filter press assembly is primarily used for the production of hydrogen and oxygen from brines, usually aqueous alkali hydroxide solutions. Similar cells are used for the production of chlorine from sodium chloride solutions. Such cells can comprise steel frames or frames made of plastic materials. One advantage of using steel frames is that they are rigid, and large filter press assemblies can then be made. However, steel frames necessitate insulation and sealing devices between the frames. Corrosion is also a problem to be dealt with. One way of dealing with the corrosion problem is the nickel plating of, for instance, the surfaces of the diaphragm elements that are exposed to the brine or lye to be electrolyzed. But nickel plating is expensive and should be kept to a minimum.
Electrolyzers of the above type have been known for a long time and are described in numerous patens. In Norwegian patent No. 157024 there is described an electrolyzer of the filter press type for production of hydrogen and oxygen. Each cell consists of bipolar electrodes separated from each other by a diaphragm element. The cells are kept together between two end plates in such a way that the electrolytic cells are kept under constant pressure by longitudinal bolts between the plates. In the electrolyzer's longitudinal direction, and at its upper part, respective channels for hydrogen and oxygen, are made in the cells. At the lower part of the cells are channels for circulating lye.
From EP 0212240 A1 there is known an apparatus for electrolysis of solutions comprising bipolar elements made up of a conductive plate peripherally surrounded by an insulating frame provided with feeding and discharging channels along peripheral zones of the frame itself. Separating elements can be inserted between the bipolar elements, consisting of a porous diaphragm and an insulating frame also carrying feeding and discharging channels.
SUMMARY OF THE INVENTION
The main object of the invention was to arrive at a new diaphragm element construction comprising the application of steel frames such that large rigid dimensions could be achieved and at the same time attain a construction giving a simpler construction of electrolyzers having fewer elements than present ones.
Another object was to arrive at a common arrangement for sealing, electrical insulation and protection against corrosion.
The main problem the inventors had to solve was the corrosion of the steelparts of the diaphragm element and how new and improved sealing and insulating means could be applied without making more complicated and expensive elements. During the development of new solutions to the problem it was found that the corrosion problem could be solved by conventional nickel plating of only minor parts of the diaphragm element and then covering the remaining exposed parts with a corrosion resistant material, for instance plastic or rubber material. Keeping in mind that the diaphragm element also had to be electrically insulated along its circumference, the inventors started investigating the possibility of using the same material for corrosion protection, insulation and sealing. It was then found that not only could the same material be used, but by doing this it became possible to make a more simple and cheap diaphragm element. This was achieved by integrating the corrosion protecting coating of the steel parts of the element with the electrical insulation and the sealing of the diaphragm element.
Useful materials for making these integrated corrosion and insulating coatings were found to be vulcanizable rubber having the required electrical in
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d'Erasmo Pietro
Lysfjord Roger Mareno
Bell Bruce F.
Norsk Hydro ASA
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