Darling Downs Power Station Australia
The 640 MW Darling Downs Power Station, one of the largest gas-fired combined-cycle power plants in Australia, is the centerpiece of Origin’s multibillion-dollar investment to provide cleaner electricity for Queensland. Constructed by a consortium including GE Energy and CH2M Hill, the plant was successfully commissioned in the second quarter of 2010.
GE supplied three Frame 9E gas turbines, three HRSGs and one C-7 combined-cycle steam turbine for the power island, which emits approximately half the greenhouse emissions of a conventional coal plant of similar size, according to the company. The 9E includes a dry-low NOx combustor system that helps to maintain emission compliance by extending the fuel flexibility.
CH2M Hill undertook engineering, procurement, construction and joint commissioning activities with GE, and provided a plant design that helps to decrease water consumption and is among the quietest in the world. The plant uses coal seam gas as fuel. Recognizing the water shortages during droughts that Queensland periodically faces, Origin Energy specified a plant that used air-cooled condensers, which help to decrease water usage. The CH2M Hill design enables the Darling Downs plant to use less than 3% of the water that would likely have been required by a conventional coal-fired plant. In addition to incorporating incorporating an ultra-quiet air-cooled condenser, CH2M Hill provided a one mega-liter/day reverse osmosis (RO) water treatment plant to produce ultrapure boiler feedwater.
To further help reduce environmental impacts, the design team utilized the ground water treatment system to recover both demineralizer RO reject and evaporative cooler blowdown wastewater streams, thus reducing fresh groundwater supply requirements. In addition, condensate from the air-cooled condenser was used as waste heat input to a wet surface air cooler (WSAC) to reduce off-site wastewater impact.
The WSAC, in combination with the wastewater recovery operations, is capable of reducing off-site wastewater trucking to less than 30% of the original design. CH2M Hill and GE coordinated an international team of in-house designers and engineers, which adapted industry-leading system designs into the highly regulated Queensland environment, with particular emphasis on the strict gas regulations and the grid interface. An analysis was performed on all major systems, and the design was enhanced for safety.
Origin required that the new plant achieve world-class noise limits. To achieve strict far-field noise limits at the plant boundary, GE provided ultraquiet combustion turbine-generator enclosures and CH2M Hill designed and constructed acoustically tight turbine halls in addition to specifying and procuring some of the quietest balance-of-plant equipment available.
The project is located in regional Queensland, a northeast state of Australia more than 200 km from Brisbane and 40 km west of Dalby, the closest town. A 550-bed construction camp was developed to attract a qualified workforce to the remote site. To help provide safe travel to and from the site, busing was provided to avoid the many hazards typical to bush driving, including flooding, heavy fog, dust storms and kangaroos. The project’s environmental stewardship extended through plant commissioning.
The commissioning team evaluated alternate approaches for cleaning the steam systems and settled on an evolutionary approach using in-situ hydro lasing, air blow and degreasing. By eliminating a steam blow, the team saved over 20 million liters of water, and an additional four mega-liters were saved by gaining acceptable steam quality within 48 hours of unit first-fire.
Source: Diesel and Gas Turbines Magazine