Boiler types electrode boilers

There are two principal types of electric boiler, the electrical resistance boiler and the electrode boiler. 

Variable Water Level, Submerged Electrode Boilers These boilers include both low- and high-voltage types and regulate steam by varying the amount of water in contact with the electrodes. As the water quantity increases, more current flows and more heat (and steam) is generated. When the water level drops below the bottom of the electrodes, no current flows and no steam is produced. 

Free caustic alkalinity usually is not recommended for jet-type electrode, as foaming conditions may develop rapidly because of the high recirculation rate. Where high alkalinity is present and FW contamination from colloidal or organic matter takes place, the foaming that develops quickly causes the boiler to be shut down. 

The quality of steam produced in electrode boilers is greatly affected by the quality of the electrolyte. For jet steam boilers, the BW should be demineralized water, with conductivity provided by adding an electrolyte. For other types of electrode boilers, the FW supplied should be fully softened, as a minimum. 

A type of boiler that produces heat via electric resistance coils or electrodes. 

The ABMA Commercial BW Requirements gives water condition guidelines for electrode-type boilers, both low voltage (LV) and high voltage (HV) ... 

Values in the table for electrode, high-voltage, forced circulation jet-type boilers assume the existence of a mechanical deaerator. ASME recommends that chemical deaeration be provided in all cases, especially if mechanical deaeration is nonexistent or inefficient. 

Enoch et al. [90] used electrodialysis reversal (EDR) to prepare boiler makeup water for Dutch power stations from several types of surface waters. EDR uses automatic reversal of electrode polarity at regular time intervals to minimize membrane scaling. The EDR unit contained 200 anion and cation exchange membrane pairs, each with a surface area of 0.47 m. Polarity reversal occurred every 15, 20, or 25 min. Samples of surface water were desalted by 96% at an energy consumption of 1 kWh/m of product water and at a current density (8.3 A/cm ) that was 80% of the limiting current density (current density when the surface water cation concentration at the membrane surface drops to zero). 

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