Diamantina is based on the Siemens SGT-800 gas turbine in combined cycle configuration. The plant comprises two identical CCGT blocks each having two by 40MW gas turbines, 2 by 2twin pressure heat recovery boilers and a single steam turbine. Each block is capable of generating ~125MW at >50% efficiency. To maximise the client’s ability to meet their power purchase obligations and also to achieve the highest plant output GT inlet chilling was added.
The use of chilling allows the gas turbines T2 temperature to be lowered to 15 DegC for ambient up to 40 DegC. This allows the plant owner to sell more output for the duration of the year instead of having the plant capped at the lowest output of the hottest day.
Another key feature in this plant is the interconnection of the two blocks and addition of supplementary gas firing. Each boiler is capable of another 33% output if required. Therefore, when a GT is out of service with its matching boiler. If required, the remaining boilers can be fired to raise the output of the steam turbines back to full capacity (remembering 1 GT and its boiler are out of service).