Thursday, 08 March 2012 10:30

Dosing Systems for Power Stations

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For the operators of power stations reliability and process security of the dosing equipment are critical factors

In 2010 and 2011 Alltech equipped several power stations in the UK with dosing systems. Dosing systems are used in several applications like for cooling water, feed water, waste water treatment, flue gas cleaning. For acid or caustic dosing the dosing stations were equipped with the robust piston diaphragm metering pumps of the FKM series. All materials used for dosing heads and diaphragms are chemical resistant. All metering pumps of the FKM type are equipped with an integrated pressure relief valve certified by the Technical Control Board. Another security feature is the diaphragm rupture signalization. Pump performance is adjusted remotely by the SERVOSET stroke length positioning system. The dosing systems are housed in chemical resistant cabinets to comply with the special security requirements which have to be considered especially in the dosing of concentrated acids and caustics.

Alltech provides pump sets for the following power station applications:

Acid and caustic dilution and dosing skids for ion exchange plant regeneration
Concentrated chemicals (typically 96% sulphuric acid and 47% caustic soda) are drawn in from bulk tanks by dosing pumps and diluted to a concentration of around 5% by an inline mixer. For acid skids, PVDF is typically used as material as it has excellent chemical and heat resistance properties. Caustic soda skids are made of polypropylene. Every skid is designed to specifically suit the client's process requirements. This system replaces vacuum ejectors, measure, and dilution tanks, which are complicated and cannot guarantee the same accuracy. Pump dosing systems are also the best option regarding operation and maintenance safety.

Ammonia dosing for large coal fired power stations
Ammonia dosing sets for boiler chemistry positioned close to individual boilers at large coal fired station provide a minimum delay in chemical correction of boiler feedwater. The system is controlled by the customer's DCS system.

Ammonia & Hydrazine dosing at gas fired power stations
This system replaced the complicated dilution and injection system and works directly from IBCs in a building that was especially planned for this purpose. The system is controlled by the customers DCS system. (Rye House)

Sodium Hypochlorite dosing for cooling tower circuits
Hypochlorite is dosed proportionally based upon feedback of free residual chlorine within the circuit. (Deeside)

Acid and Caustic dosing for pH correction
Acid or caustic is diluted from concentrated chemicals stored in bulk tanks (Ferrybridge) to around 10% strength and dosed proportionally based upon feedback of pH.

Polymer dosing (Fiddlers Ferry)
Dosed as a flocculating agent to a water clarifier.

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