INVESTIGATION OF COOLING WATER CHEMICAL DOSING: THE OHAAKI GEOTHERMAL POWER STATION COOLING TOWER

Abstract

The Ohaaki power station is the only geothermal power station in New Zealand with a natural draft cooling tower. The concrete construction of the cooling tower influenced the locations vulnerable to attack from condensate/cooling water pH and from microorganism growth, and this altered the way chemical biocide was applied compared to forced draft cooling towers found in other flash steam power stations. Biocide was routinely sprayed directly onto the internal shell walls of the tower while the basin cooling water was only dosed seasonally. This work presents a review of the chemical dosing history at the Ohaaki cooling tower, investigation into the effectiveness of the dosing regime and improvements to the understanding and monitoring of the degradation and control mechanisms.