Electrolysis: processes – compositions used therein – and methods – Electrolytic material treatment – Water – sewage – or other waste water
Reexamination Certificate
2001-03-19
2003-03-04
Phasge, Arun S. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic material treatment
Water, sewage, or other waste water
C205S746000, C205S755000, C204S228600, C204S275100, C204S276000
Reexamination Certificate
active
06527942
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a conditioning system and to a method for reducing the oxygen content of water carried in a subsystem of an industrial plant.
Subsystems in which water is carried are provided in a multiplicity of industrial plants, for example, in chemical production workshops or in nuclear or fossil-fuel power plants. Such a subsystem may be, for example, a cooling circuit or a circulating circuit for the working medium.
In such a context, a high oxygen concentration in the water carried in the subsystem may lead to a corrosion of fittings or of pipes of the subsystem. To avoid damage to the subsystem or else to the entire industrial plant reliably, therefore, it may be necessary, as required, to reduce the oxygen content of the water carried in the subsystem. The requirement may arise, in particular, when the water is subjected continuously to oxygen for operational or conceptual reasons.
For example, it may be necessary for the intermediate cooling circuit of a nuclear plant to have a compensating tank for the water carried in the intermediate cooling circuit, the water coming into contact with ambient atmosphere in the manner of an open configuration in the interior of the tank. The continuous introduction of oxygen into the intermediate cooling circuit caused thereby may lead to an oxygen concentration in the water carried there of, for example, up to 8 ppm (parts per million). For reasons of corrosion protection, however, it may be necessary, in spite of the continuous introduction of oxygen, to keep the oxygen content in the water carried in the intermediate cooling circuit permanently at a value of less than 20 ppb (parts per billion).
For such a purpose, in an intermediate cooling circuit of a nuclear plant, there normally is a provision for an on-demand feed of the water carried there with hydrazine (N
2
H
4
). The hydrazine reacts with the oxygen contained in the water to form nitrogen (N
2
) and water (H
2
O), so that the oxygen content of the water is lowered significantly. However, precisely in the case of a plant with continuous oxygen introduction, a more or less permanent addition of hydrazine is necessary, so that more and more nitrogen is formed in the water. The additional formation leads to a continuous rise in the conductivity of the water and, therefore, to a permanent change in the water chemistry. At the same time, for operational reasons, when predetermined conductivity limits are exceeded or when a predetermined PH value is exceeded, a complete exchange of the water carried in the respective subsystem of the industrial plant is necessary. Precisely where complex industrial plants are concerned, a complete water exchange is highly complicated and, moreover, entails undesirably long standstill times of the plant.
Alternatively, on-demand vacuum degassing of the water may be provided to set a low oxygen content in the water. Such a concept, however, involves a high outlay, particularly in terms of the components required.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a conditioning system and method for reducing the oxygen content of water carried in a subsystem of an industrial plant that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that makes it possible, at particularly low outlay in structural and technical terms, to have a reliable on-demand setting of the oxygen content in the water below a predeterminable limit value.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a conditioning system for reducing an oxygen content of water carried in a subsystem of an industrial plant, including an electrolysis unit having a hydrogen side, an anode, and a cathode, the anode and the cathode connected to the subsystem to decompose water into hydrogen and oxygen, and a hydrogen/oxygen recombination catalyst connected to the subsystem, the hydrogen/oxygen recombination catalyst following downstream the anode and the cathode on the hydrogen side.
The invention relates to a treatment system for reducing the oxygen content of the water that is guided in a subsystem of a technical installation. The aim of the invention is to provide a reliable way of adjusting the oxygen content of the water below a predetermined limit value, as required. The invention strives to be as simple as possible in constructional and technical terms. To such an end, an electrolysis unit for decomposing a portion of the water into hydrogen H
2
and oxygen O
2
is connected to the subsystem. A hydrogen-oxygen recombination catalyzer that is connected to the subsystem is connected downstream of the electrolysis unit on the hydrogen side.
The invention achieves its objectives, with respect to the conditioning system, by connecting an anode and cathode of an electrolysis unit to the subsystem to decompose water into hydrogen and oxygen. They are followed downstream on the hydrogen side by a hydrogen/oxygen recombination catalyst connected into the subsystem.
The invention proceeds from the notion that a reliable setting of a low oxygen content in the water is possible at particularly low outlay by subjecting the oxygen to a reaction, the products of which not adversely changing the water chemistry. Oxygen is recombined with hydrogen, in which the sole final product is water. Feeding with hydrogen as a reaction partner for the oxygen takes place on demand through the electrolysis unit, followed by the hydrogen/oxygen recombination catalyst to ensure a complete conversion of the hydrogen fed therein.
Expediently, the electrolysis unit is provided for decomposing a partial quantity of the water carried in the subsystem and, for such a purpose, is likewise connected on the inlet side to the subsystem. Water from the subsystem can be supplied to the anode and cathode of the electrolysis unit. The terms “anode” and “cathode” as used herein also refer to a plurality of anodes and cathodes. The electrolysis unit may, at the same time, particularly for compensating volume losses, be capable of being fed additionally with water from a separate water reservoir in which the water can be kept, for example, as deionized water.
At the same time, in a particularly advantageous refinement, the hydrogen/oxygen recombination catalyst includes, as catalytically active components, a number of polymer beads provided with a palladium layer, such as are described, for example, in a prospectus from the Bayer company titled “Katalytische Entfernung von gelöstem O
2
aus Wasser” [“Catalytic removal of dissolved O
2
from water”], No. OC/I 20 377, October 1995.
In accordance with another feature of the invention, the electrolysis unit includes a number of membrane-type electrolysis cells. In such a membrane-type electrolysis cell, the functional principle of a fuel cell, such as is disclosed, for example, from the paper “Brennstoffzellen für Elektrotraktion” [“Fuel cells for electrotraction”], K. Stra&bgr;er, VDI-Berichte [VDI Reports], No. 912 (1992), page 125 ff., is reversed. Water is supplied to a membrane disposed between an anode and a cathode. By applying a supply voltage between the anode and the cathode, the water is decomposed electrolytically into hydrogen and oxygen. Such a membrane-type electrolysis cell is distinguished by a particularly compact form of construction, so that an electrolysis unit with a number of membrane-type electrolysis cells can be accommodated in a particularly confined space. Consequently, the an electrolysis unit can be connected into the subsystem in a particularly flexible way and so as to be adapted to the specific needs of the subsystem.
In an advantageous refinement, a discharge system for oxygen is connected to the electrolysis unit. Particularly, the electrolysis unit has an oxygen side, and the oxygen discharge system is connected to the oxygen side of the electrolysis unit. Thus, the oxygen generated during the decomposition of the p
Greenberg Laurence A.
Mayback Gregory L.
Phasge Arun S,.
Siemens Aktiengesellschaft
Stemer Werner H.
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