| JP61011547 | HOT-WATER RESERVING TYPE ELECTRIC WATER HEATER |
| WO/1990/012988 | HOT WATER HEATERS |
| JP55165441 | HOT WATER BOILER |
LØVLAND, Martin (Allegaten 8, Flekkefjord, N-4400, NO)
| C l a i m s 1. Ail electrode boiler including a container (5) holding water, a number of electrodes (7a - f) submerged in said water, a source of AC electric power connected with said electrodes, means for supplying water to said container, means for removing hot water or steam from said container, means for holding the water in said container at a pre-defined level, c h a r a c t e r i z e d i n that the electrodes are even in number and are arranged in a circle, wherein electrodes (7a - 7d; 7b - 7e; 7c - 7f) that are located at 180° distance along said circle are connected to each other and to one phase of electric power from said source. 2. An electrode boiler as claimed in claim 1, said boiler including six electrodes forming three pairs of opposing electrodes. |
Field of the invention
The present invention relates to an electrode boiler for providing hot water or steam.
Background
An electrode boiler includes a number of electrodes, one for each phase, that are immersed in a water bath. Heat is generated by passing an AC electrical current from an electrode to a counter electrode using the water as conductor. The boilers are designed for low voltage ((230 - 400 V) and high voltage (5 - 20 kV) supply and with heat ratings from about 2 - 100 MW. Electrode boilers have many advantages, such as an efficiency approaching 100%, easy control of output range and a fast startup. They are environmentally friendly as well, failsafe as to low water level; this only preventing current from flowing, and there is no danger of catastrophic failures. However, up to now electrode boilers have only been used in stationary arrangements, i.e. mounted in buildings. Existing electrode boilers are not regarded as suitable for use in e.g. marine environments, as the heaving and rolling of a vessel will affect the water level and thus the electric path between the electrodes.
An AC electrode water heater with a circular electrode pattern has been proposed in Swiss patent no 1 486 346. The described principle is intended for use in a static environment. The water heater described uses a central shaft with mechanical operation for regulating the output.
A water heating apparatus using electrodes connected to DC current is described in EP 1 703 225 A2. As the boiler uses Direct Current the problem with inclination is much less complicated.
An electrode boiler using 3-phase AC current is described in DE 3421807 Al. This concept utilizes a center electrode and is designed for a step-regulation of the output. The described boiler is not intended for operation with roll and pitch motions.
An electrode boiler using 3-phase AC current is described in MD 2366 Bl 2004.01.31. This boiler is not applicable for operation in moving environments with roll and pitch motions. Summary of the invention
Thus, it is an object of the present invention to provide an electrode boiler that is adapted for being installed in a non-stationary environment.
This is achieved in a boiler as defined in the appended claims. In particular, the inventive electrode boiler includes an even in number of electrodes that are arranged in a circle, wherein electrodes that are located at 180° distance along said circle are connected to each other and to one phase of AC electric power.
Brief description of the drawings
The advantages of the invention will become apparent by reading the following detailed description in reference to the appended drawings, in which
Fig. 1 is a general overview of a boiler installation showing its main components,
Fig..3. is a sectional view of a boiler according to the present invention,
Fig. iis a section along the line D - D in fig. 1.
Detailed description
The invention relates to an electrode boiler, and the embodiment of the invention described in the following paragraphs is intended to supply hot water. As shown in Fig. 1 the boiler 1 is connected in a closed water loop to a circulation pump 2 and a heat exchanger 3. The pump circulates water continuously through the boiler, in which it is heated, the produced heat being removed in the heat exchanger 3 whereupon the now colder water is sent back to the boiler for reheating, m a corresponding embodiment for steam generation, the heat exchanger will be omitted and the steam delivered directly to a pipe network.
Fig. 2 shows the inner workings of the boiler 1. The boiler includes a boiler drum 4. Inside the drum 4 there is mounted an inner container 5 on electrically insulated brackets 6. A number of electrodes 7 are suspended from the roof of the drum, in conductive rods 8 passing through insulated bushings 9. The rods 8 are connected to a source of AC electric power by means of conductors 10. The inner container 5 holds water at a predefined level. The water level is controlled by a valve 11, from readings from a level gauge (not shown). Alternatively, the water level may be controlled by a overflow channel. The production from the boiler may be controlled by changing the water level or by changing the conductivity of the water.
The arrangement of the electrodes 7a- f is illustrated in Fig. 3. The electrodes are connected in a star arrangement, with opposing electrodes being connected together in pairs and fed from the same phase, e.g. electrode 7a is tied together with the opposing electrode 7d, electrode 7b is tied to electrode 7e and electrode 7c is tied to electrode 7f. Said in another way, each phase is split and acts on two symmetrically placed electrodes. The water/container forms an insulated neutral point in the star connection between the electrodes. The current will flow from the two electrodes of one phase, through neutral, to an electrode pair of another phase, the water acting as conductor. The conductivity of the water is governed by mineral content and temperature.
If the boiler is installed in a marine environment, such as a ship, heaving of the vessel will tilt the boiler causing an inclination of the water surface. However, due to the symmetrical arrangement of electrodes depicted in Fig. 3, a lower water level at one electrode will be compensated for by a higher water level at the other electrode in the pair. In this way tilting of the boiler will not give uneven power production on the three phases.
In a more general way, the special features of the invention are enabled when an even number of electrodes is arranged in a circle, and two and two opposing electrodes are connected in pairs, and each pair again is connected to one phase of AC power supply. That the electrodes are opposing means that they are located with 180° distance along the circle. In the embodiment of the invention described above, there is a total of six electrodes, wherein two and two are connected to each other and to one electric phase. However, larger patterns of electrodes are possible, such as twelve electrodes arranged in a circle. Then, two and two opposing electrodes are again connected in pairs, but in addition two and two of the pairs are also connected to each other (and to a common phase). Any combination of electrode pairs may be connected together provided that all sets of electrodes show identical patterns in the circle.