Electrode boiler
The electrode boiler is used to generate warm water, hot water or steam directly from electrical energy. It is characteristic that it is operated with alternating current and the current is introduced directly into the water without resistance heating elements in the electrode boiler by means of mostly three electrodes.
Types of construction and regulation
Water heating
As in electrolysis , electrodes that are under voltage are brought into direct contact with water, but these are not charged with direct voltage, but with alternating voltage. This prevents the actual electrolysis and there is no electrolytic decomposition of the water into hydrogen and oxygen . The water is heated purely by electrical resistance. In the past, certain types of systems were controlled by adding conductivity-increasing substances such as salts and adding demineralized water in order to reduce performance; however, these processes can only be regulated slowly.
The alternative, more common method is the regulation by varying the electrode coverage by changing the water level, either by mechanical elements (overflow top, drain flap) or by the vapor pressure, which pushes the liquid level down when the temperature rises and the electrodes are no longer covered. This requires water to be able to enter and exit below. Correspondingly shaped electrodes support the regulation.
Steam generation
In the Sulzer design , electrodes are hit by a downward jet of water from a higher-level distributor chamber. The current flows through the water jets and part of the water evaporates. Movable interception devices are installed in the vessel to intercept the water jets at partial load.
In a further design, jets of water emerging from the lower electrodes hit the counter-electrodes above. The higher the water delivery rate, the more steam is generated. When the steam pressure increases, the delivery rate is reduced.
Power supply
Medium voltage (1 kV to 35 kV ) is usually applied directly to the boilers .
power
The electrode boilers are built for a power range from 0.5 MW to 90 MW. Several systems are connected in parallel for larger capacities. When the systems are in operation, they always have a minimum output of around 5 to 10% and can be adjusted to 100% output in a few seconds.
Power-to-heat
In addition to the significantly more efficient heat pumps, which are also more expensive to install, electrode boilers represent an option for implementing power-to-heat systems in local and district heating networks. In contrast to heat pumps, their efficiency is limited to almost 100%, but they are higher Temperatures and build more compact.
Trivia
Very simple immersion heaters worked with an identical functional principle, but with significantly lower power , which directly heated the water with two electrodes immersed in the water due to its specific resistance. Improvisations used in the NVA were colloquially known as Atomino . The principle of water resistance was also used to start slip-ring motors by immersing electrodes in water. See liquid starter .
See also
Individual evidence
- ↑ hannovermesse.de .
- ^ German patent: Electrode boiler December 23, 1987, Patentblatt 1987/52.
- ↑ Electric steam generator patent: US 4109137 A.
- ↑ Electric boiler with a device for controlling steam generation Patent: US 4314139 A.
- ↑ High-voltage electrode kettle. VAPEC AG, accessed on January 29, 2018 .
- ^ Carl Züblin: The electric boilers of the company Sulzer Brothers AG Winterthur. In: Polytechnisches Journal . 343, 1928, pp. 77-81.