CN115667797A

CN115667797A - Electrode boiler

Info

Publication number: CN115667797A
Application number: CN202080101159.6A
Authority: CN
Inventors: 弗雷德·斯特罗姆兰德
Original assignee: Parat Halvorsen AS
Current assignee: Parat Halvorsen AS
Priority date: 2020-05-22
Filing date: 2020-05-22
Publication date: 2023-01-31
Also published as: FI4153910T3; EP4153910A1; DK4153910T3; EP4153910B1; WO2021235938A1

Abstract

The invention relates to an electrode boiler comprising a container (5) for containing water; a plurality of electrodes (7), each electrode comprising a first upper end connected to a power source and a second lower end immersed in water; and means for controlling the water level in the container. The device comprises a circulation pump (2) for supplying water to the container (5) through a supply line (16) and a throttle valve (14). Additionally, the boiler comprises an arc extinguisher (15) located below the second lower end of each electrode (7), the arc extinguisher comprising a receptacle made of an electrically insulating material, wherein an upper edge of the receptacle is positioned flush with or only above the second lower end of the associated electrode (7).

Description

Electrode boiler

Technical Field

The present invention relates to an electrode boiler for providing hot water or hot steam and a method for operating the same.

Background

The electrode boiler comprises a plurality of electrodes, one for each electrode, immersed in a water bath. Heat is generated by conducting AC current between the electrodes or conducting current to the counter electrode using water as a conductor. The boiler is designed for low voltage (230-690V) or high voltage (1-36 kV) power supplies and has a thermal power of about 0-100 MW. Electrode boilers have many advantages such as near 100% efficiency, easy control of output range and fast start-up.

The output of the boiler can be controlled by the water level covering the electrodes more or less. The output can be turned off by a switch or by lowering the water level to be inaccessible to the electrodes. Each method has its advantages. Because the switches must handle large currents, they are subject to wear. By lowering the water level below the electrodes, switching off and turning off the boiler can be completely avoided. However, when water is drained and reaches under the electrode tip, an arc may be created. The arc may reach the other electrode directly or via a metal piece of the boiler. This situation may lead to a dead short.

From GB 472,479 a steam generating electrode boiler is known, in which the bottom of the electrodes terminates in an "arc deflection boiler". In the event that the water level in the boiler drum drops below the electrode, the pan ensures that the tip of the electrode is still surrounded by water to prevent current interruption that could cause the formation of an arc.

Disclosure of Invention

An object of the present invention is to provide an electrode boiler which can be shut down by lowering the water level without generating an arc to short-circuit a power supply.

This is achieved in a boiler as defined in the appended claim 1. In particular, the electrode boiler of the present invention comprises a container for containing water; a plurality of electrodes, each electrode comprising a first upper end connected to a power source and a second lower end submerged in water; and means for controlling the water level in the container. The device comprises a circulation pump for supplying water to the container through a supply line and a throttle valve. Furthermore, the supply line is connected to an arc extinguisher located below the second lower end of each electrode, the arc extinguisher comprising a receptacle made of an electrically insulating material, wherein the upper edge of the side wall is positioned flush with or only above the second lower end of the associated electrode.

Operating an electrode boiler using the method according to claims 2 and 3. In particular, the presence of the insulating arc extinguisher will effectively prevent the formation of electric arcs when the boiler is shut down by lowering the water level inside the vessel.

Drawings

The advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:

fig. 1 is a general overview of a boiler plant, showing the main components of the boiler plant,

fig. 2 shows a detail of the boiler according to the invention.

Detailed Description

The present invention relates to an electrode boiler, and embodiments of the invention described in the following paragraphs are intended to supply hot water. As shown in fig. 1, a boiler 1 is connected to a circulation pump 2 and a heat exchanger 3 in a closed water circuit. The pump continuously circulates the water through the boiler where it is heated, the heat generated is removed in the heat exchanger 3, and the now cooler water is then returned to the boiler for reheating. In a corresponding embodiment for generating steam, the heat exchanger will be omitted and the steam is delivered directly to the pipe network.

The boiler comprises a boiler drum 4. Inside the barrel 4, an inner container 5 is mounted on an electrically insulating support. A plurality of electrodes 7 are suspended from the top of the barrel on conductive rods passing through insulating sleeves. The rod is connected to an AC power source by conductor 10.

Further, the boiler system comprises: a three-way throttle valve 6 controlling the flow in a closed water circuit comprising a circulation pump 2 and a supply line 16 supplying the container 5 with water; a liquid level safety meter 8 and a liquid level control system 9; a pressure relief valve 11; a throttle valve 14 for discharging water from the inner vessel 5; a treated feedwater inlet 12 and a blowdown outlet line 13.

The inner container 5 contains a predetermined level of water. The water level is controlled by the throttle valve 14 based on readings from the level gauge. The production of the boiler can be controlled by varying the water level. The water is supplied through a supply line 16 which branches into a plurality of small tubes into the bottom of the inner vessel 5.

Figure 2 is a schematic illustration of the present invention. An arc extinguisher 15 is installed below each electrode 7. Each arc extinguisher comprises a receptacle of an electrically insulating material, such as a ceramic material (e.g. porcelain), glass or PFTE. The arc extinguisher may be positioned at the bottom of the vessel 5. The arc extinguisher is mounted to ensure that the top edge of the receptacle is positioned flush with or preferably slightly above the lower end of the associated electrode 7. In the bottom of each arc extinguisher there is an opening connecting the receptacle to the water supply line 16.

When it is desired to stop production, the water in the inner container 5 is drained via the throttle valve 14. The water outside the arc extinguisher 15 will be completely drained and the water inside the arc extinguisher will remain level with the upper edge of the receptacle and in contact with the electrodes 7. Then, the circulation pump 2 supplying water through the supply line 16 is stopped, whereby the water level inside the arc extinguisher 15 will also drop. At some point, the water will lose contact with the electrode 7. This is the moment when an arc may occur. However, the presence of an arc extinguisher means that the arc must climb up an insulating barrier to reach the other electrode or the metal part of the surrounding container 4. This will effectively prevent the formation of an arc.

Claims

1. An electrode boiler comprising a container (5) for containing water; a plurality of electrodes (7), each electrode comprising a first upper end connected to a power source and a second lower end immersed in water; and means for controlling the water level in the container (5), wherein the means comprise a circulation pump (2) for supplying water to the container (5) through a supply line (16) and a throttle valve (14),

characterized in that the supply line (16) is connected to an arc extinguisher (15) located below the second lower end of each electrode (7), the arc extinguisher (15) comprising a receptacle made of an electrically insulating material, wherein the upper edge of said receptacle is positioned flush with or only above the second lower end of the associated electrode (7).

2. A method for operating an electrode boiler according to claim 1, wherein the production of the electrode boiler is started and stopped by controlling the water level outside and inside the arc extinguisher (15).

3. A method according to claim 2, wherein production is stopped by first draining water from the container (5) and then draining water from the arc extinguisher (15).