Samiksha Jaiswal (Editor)

Electrode boiler

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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. 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 as the cleaner the water, the lower the conductivity. When conductivity goes beyond certain limit, some of the water must be blown down and replaced with fresh water. 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. The electrodes are connected to a high voltage A.C. source, typically 6,600 volts to 13,800 volts. If D.C. 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)}. Electrode boilers can work on both Single phase and Three phase supplies. The electrode boiler is 99.9% efficient with almost all the energy consumed producing steam.

Contents

The conductivity of the water and the voltage applied determine how much steam is generated in each stream of water. 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 lbs 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.

Advantages

  • All electrical energy is converted to heat, and doesn't directly generate pollution nor needs a pollution control system.
  • Electrode boiler has very quick response time.
  • Compact size of electrode boiler makes it easier to work with than other kinds of boiler like fossil fired boilers etc.
  • Electrode boilers are not directly polluting, thus they don't release any harmful gas like carbon monoxide which adversely affects the environment.
  • No need of a chimney.
  • As compared to other boilers, there is little thermal stressing, so steam raises quickly.
  • Unlike fossil fuel or conventional electric boiler, no component of electrode boiler is at high temperature except the water itself, during the operation.
  • There is no requirement of low voltage transformer due to which High Voltage supply grid connection can be established.
  • The number of components in an electric boiler are at a minimum, so easy to control and maintain.
  • Absence or limited quantity of water in the boiler does not allow current to flow and hence electrode boiler cannot produce steam and this stops the working of boiler.

    • 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 D.C. 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.
  • 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 and this stops heating the water and producing steam as a result working of electrode boiler terminates.

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

    • Clean water, when gets evaporated into steam, it does not leave any kind of ion in the boiler and thus reduces the possibility of formation of scales.

    References

    Electrode boiler Wikipedia
    (Text) CC BY-SA