Unit 1 Ch4 Electric Boilers

Electric Boilers Overview

Glossary

  • Electrode: A conductor through which electric current is passed, which may take the form of a plate or rod.

  • Furnace Explosion: An event occurring in a furnace due to the ignition of an accumulation of combustible gases, resulting in an explosion. A small-scale version of this is referred to as a furnace puff.

Steam Trap: A device installed on steam lines to remove condensate without allowing the loss of any steam; some types can also remove air.

Advantages of Electric Boilers

  • Compact Design: Electric boilers are compact and do not require ductwork or chimney systems, saving space in installations.

  • Fast Installation: They can be quickly installed, as there is no need for extensive setups typical of fuel-fired boilers.

  • High Efficiency: Approximately 98% of energy delivered as electricity is absorbed as heat in the boiler, leading to high operational efficiency.

  • Low Emissions: Electric boilers generate no pollution such as smoke, dust, etc., unless the source of electricity is non-renewable.

  • Silence and Safety: They operate silently and have a low risk for accidents such as furnace explosions, unlike their fuel-burning counterparts.

  • Temperature Management: Metal temperatures in electric boilers remain lower compared to fire-tube and water-tube boilers, reducing scaling. Deposited solids tend to remain as sludge rather than adhere to metal as damaging scale.

  • Low Water Level Safety: In electrode boilers, if water levels drop too low, electric current ceases to flow and consequently generates no heat, protecting against overheating.

Disadvantages of Electric Boilers

  • Operating Costs: The primary drawback is the typically high cost of electricity required for operation.

  • Pressure Limitations: Designs generally limit operating pressure to about 2100 kPa (304 psi) due to high temperatures affecting the electrodes or heating elements.

Types of Electric Boilers

Electrode Boiler

  • Design Components: Electrode boilers consist of two cylindrical chambers, with electrodes generating heat by passing electric current through water. The specific components include:

    • Power Supply: Flows through insulated adapters to electrodes outside of a shell.

    • Generating Chamber: Where the heat is generated.

    • Regulating Chamber: Manages steam pressure reducing it before it is sent for use.

    • Safety Features: Includes pressure regulators, safety valves, pressure gauges, and water level gauges.

Functioning of Electrode Boiler

  • Upon activation:

    • Water levels are balanced in both chambers.

    • Electric current passing from one electrode to another generates heat, turning water into steam.

    • Steam exits via the steam outlet for use in processes.

    • Steam pressure management is handled by the regulator that can be adjusted as per needs.

    • Automatic air vent eliminates trapped air on startup.

    • Responses to demand fluctuations:

    • High demand leads to pressure and current adjustments.

    • Conversely, reduced demand lowers pressure, resulting in more water covering the electrode, which maintains steam generation.

Immersion Heater Boiler

  • Operation: Control is managed by switching power on and off to manage either one or multiple heating elements as needed.

  • Components: Packaged immersion heater units may come with integrated controls, feed pumps, and condensate tanks for streamlined operation.

  • Maintenance: Arranged for easy access to heating elements for maintenance or replacement.

  • Challenges: High temperatures of heating elements can lead to scale formation, necessitating stringent water treatment protocols, which is more critical compared to electrode-type electric boilers.

Summary

  • Electric boilers offer compact solutions with high efficiency and low emissions, making them suitable for multiple applications despite some operational cost considerations and design limitations.