Electrode boiler

An electrode boiler (jet type) is a type of boiler that uses electricity flowing through streams of water to create steam. The conductive and resistive properties of water are employed to carry electric current.

Technical Principle

The most common type of electrode boiler pumps water from the lower part of the vessel to an internal header that has nozzles that allow the water to flow to electrodes. Generally the working pressure is maintained at 10 bar. If more pressure is needed (more steam) the controls speed up the pump and flow more water through additional nozzles. As the needed pressure is reached the pump controls the flow of water to obtain the desired steam output (in kg per hour) at the desired pressure. On larger systems the pump can be controlled by a variable frequency drive (VFD) so energy is not wasted. This control system can also control de-aerator pumps and controls.

The electrodes are connected to a medium voltage (1-35 kV) AC source. Electrode boilers can work on both single phase and three phase supplies. If DC voltage is used, electrolysis of water occurs, decomposing water into its elements H2 at the cathode (negative electrode) and O2 at the anode (positive electrode). The electrode boiler is 99.9% efficient with almost all the energy consumed producing steam.[1] Losses are radiant heat from the vessel only.

During the operation of the boiler, it is fed with water which contains conductive substances like salts. Because the departing steam is free of these substances, conductivity of water increases. With cleaner water in the boiler, the conductivity decreases. When conductivity goes beyond certain limit, some of the water must be blown down and replaced with fresh water. The conductivity of the water and the voltage applied determine how much steam is generated in each stream of water.

Advantages

  • All electrical energy is converted to heat.
  • An electrode boiler has a very quick response time.
  • As it doesn't directly generate pollution, no pollution control system is needed.[2]
  • Electrode boilers are not directly polluting. They don't release any harmful gas like carbon monoxide which adversely affects human life and the environment.
  • No need for a chimney.
  • Unlike fossil fuel or conventional electric boiler, no component of electrode boiler is at high temperature except the water itself.
  • As compared to other boilers, there is little thermal stressing.[3]
  • Compact size of electrode boiler makes it easier to work with than other kinds of boiler like fossil fired boilers etc.
  • There is no requirement of low voltage transformer due to which a medium voltage (1-35 kV) grid connection can be established.
  • The number of components in an electric boiler is low, it is easy to control and maintain.
  • Limited quantity of water in the boiler does not allow current to flow. This stops the working of the boiler in a self-regulating manner.

Drawbacks

  • Due to the water serving as a conductor, the water becomes live at a significant portion of the input voltage. This can create a shock hazard when used, for example, to heat water for a bath or for tea making.
  • It leads to high operating cost due to increase in demand and energy charges.
  • Use of DC sources leads to electrolysis of water as a result, water gets broken down into its components hydrogen and oxygen, thus stops the working of boiler.[4]
  • If there is formation of scale, then it will insulate the electrodes electrically which results in reduction of current and boiler output.

Safety Measures

  • Water level should be maintained up to certain level and it should not be allowed to lower than that limit.

If water level falls below the limit level, current stops flowing as the circuit is not complete. This stops heating the water and producing steam.

  • Scale formation should be avoided by feeding clean water to the boiler.

Clean water does not leave any kind of ion in the boiler, when it gets evaporated into steam. Thus, the formation of scales is reduced.

References

  1. ↑
  2. ↑
  3. ↑ "emt-india.net". www.emt-india.net.
  4. ↑ "TLC Electrical Supplies". www.tlc-direct.co.uk.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.