The HCO system allows for fast ramping. In cold start-up, the clearance gaps between the turbine blades and casing are wider than in hot conditions. During the engine start-up regime, the rotor disk expands. When stable op- eration is reached, the gaps open again. This means the rotor can be hydraulical- ly adjusted to minimize the gaps during steady operation.
At full load, the gas turbine provides exhaust gas at a temperature of 630°C and a mass flow of 640 kg/s to the HRSG. This exhaust energy is delivered to a three-pressure drum SMART design HRSG by Vogt Power International, for 165 bar and 565° C (2400psi and 1050°F) steam cycle conditions.
High-pressure steam from the HRSG is fed to a steam turbine, which has a combined HP/IP section and double- flow LP section. The steam turbine uses steam from the HRSG to generate approximately one third of the plant’s output, giving each train an output of around 415 MW.
The plant is also designed to keep emis- sions to a minimum. Like the SGT5- 8000H, the SGT6-8000H uses an ultra- low NOx combustion system. Although the system is not a direct scale of the SGT5-8000H combustion system, there is a common platform approach.
The combustion system consists of 12 low-NOx burners and baskets with air-cooled transitions. The annular ar- rangement provides excellent uniformity of exhaust gas temperature field.
The ultra-low NOx combustion sys- tem combined with the plant’s high ef- ficiency serves to ensure extremely low emissions from the facility. It has an integrated selective catalytic reduction (SCR) system as well as a CO catalyst. According to Siemens, this helps the plant to not only operate within permit- ted emission limits, but also is represen- tative of Best Available Control Tech- nology (BACT) levels, i.e. 2 ppm NOx and 2 ppm CO.
With the high efficiency of the plant and the use of shale gas, CO2 emissions are expected to be among the lowest in the country. “The emissions are so low, they actually test the accuracy of the in- struments, which were not originally de- signed to measure such low ppm,” com- mented Porter.
The plant is also environmentally friendly from a water-use point of view; it uses air-cooled condensing to mini- mize the consumption of local water re- sources. The Patriot plant does not draw water from, or discharge water into, the Western Branch of the Susquehanna River – eliminating potential impacts to species in the Susquehanna watershed.
Good for the community
The introduction of this new, clean, generating capacity is the culmination of a 30-month project construction pe- riod that started in December 2013, fol- lowing the receipt of the air permit in August that year.
During its construction, Patriot cre- ated more than 1000 jobs, with approxi- mately 650 at the peak of construction – work that was executed without loss of time due to injury.
Further, the plant will continue to benefit the community during operation. Twenty seven full-time employees cur- rently operate the facility, and 45 indirect jobs are expected to be created within the community to support the plant during operations. According to an economic impact study conducted by Impact Data Source of Austin, Texas, the Panda Pa- triot plant will contribute an estimated
$5.85 billion to the area’s economy dur- ing the now post-construction phase and the facility’s first 10 years of operation.
Patriot, like Liberty, is an important project for Pennsylvania, Panda and the wider US gas fired power generation sector. “These projects are extremely important when you think about the con- version from coal to gas and, being the first two plants built to use Marcellus shale, are already a model for the indus- try,” said Porter. “You are seeing devel- opments right now that look similar to these projects.”
Pentak added: “They are certainly a model for Pennsylvania. What we’ve learned as we’ve done business in Penn- sylvania, is that there is this tremendous amount of shale gas that is essentially trapped – there isn’t the pipeline infra- structure that’s needed to get this gas to market. We’re taking the gas and con- verting it to electrons and shipping it out to the area through the transmission lines – we call it gas-by-wire.”
As pressure continues to deliver pow- er in the cleanest and most cost-effective manner, these projects highlight the advantages that clean gas fired power plants can bring, not just in the PJM area but throughout the country.
Pentak concluded: “As the transition from coal fired plants to natural gas con- tinues, plants like these are the tip of the spear in terms of that transition.”
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