Articles & Case Studies

Hanovia UV Ensures Low TOC Levels In Boiler Feedwater At Kaeng Khoi 2 Power Plant In Thailand

Posted: Monday 18th August 2008

Hanovia's medium pressure UV technology has been chosen for TOC (total organic carbon) reduction in boiler feedwater at the newly constructed Kaeng Khoi 2 power plant in Saraburi, Thailand.

TOC can cause corrosion in the boiler systems of power plants so its reduction is essential. Most plants set maximum limits for TOC in boiler feedwater, the level depending on the pressure of the boiler the lower the pressure, the lower the purity requirements. The majority of organic compounds found naturally in water can be removed by physical processes like ultrafiltration or by ion exchange. Some organic compounds, however, require additional steps for their removal or destruction.

Hanovia's medium pressure UV systems are specially designed to achieve extremely high degrees of TOC reduction. They achieve this with special UV lamps that break down TOCs and other low level organics in two ways: firstly, by dissociating their molecular bonds; and secondly, by generating aggressive hydroxyl radicals from water molecules, which also break down TOCs.

The Hanovia UV system at Kaeng Khoi 2 is integrated into a demineralisation plant supplying water for the boiler feedwater system. Following softening and clarifying pre-treatment, the water passes through fine sand filters and then undergoes reverse osmosis to remove TDS (total dissolved solids) before passing through two Hanovia chambers. Positioned in series, each chamber contains six medium pressure UV lamps. Following UV treatment the water undergoes polishing in a mixing bed prior to use.

The two Hanovia UV chambers treat a combined water flow of up to 400m3/. Actual TOC input to the UV chambers is 183ppb and output is 58ppb a 68% reduction and well below the required minimum required concentration.

The contractors who supplied the demineralisation plant decided to use Hanovia UV technology because of the company's international reputation for reliability and customer service. Other important factors were the low pressure drop through the UV chambers and the system's overall ease of use compared with competitors' equipment.

All Hanovia UV units can be easily integrated into plant control systems. Maintenance requirements are minimal typically the UV lamps only need replacing once a year, an easy operation which can be carried out by on-site personnel.

Kaeng Khoi 2 is a gas-fired thermal power plant situated in Saraburi province north of Bangkok. The plant has two combined cycle power generators with an output of 724MW each.

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