Spring training is when rookies and veterans alike are drilled on baseball’s fundamentals—throwing, catching, and hitting—regardless of the number of games or titles won in past years. Similarly, superior power plant performance is only achieved by a motivated plant team that’s well-schooled in the fundamentals of power plant operations and maintenance (O&M). One of those fundamentals is optimizing combustion.
The cost of fuel is by far the largest variable cost of operating a power plant. The typical coal-fired plant strives for the lowest possible heat rate for a given fuel supply in order to keep retail rates low. To lower their overall fuel costs, some utilities have adopted a fuel supply strategy based on spot market fuel purchases rather than the more conventional practice of hedging future costs with long-term fuel purchase contracts. This strategy makes more sense to accountants than to plant operators, and here’s why.
Purchasing lower-quality fuels will decrease fuel costs only if your plant is capable of reliably and economically burning the wide range of fuels available on the spot market. Some less-desirable fuels will increase boiler slagging and fouling and cause other serious operational and reliability problems. The decision to increase spot market purchases must be carefully considered, because it will add more operating risk to a plant already stressed by an aging infrastructure, workforce reductions, and a stagnant O&M budget. Using spot market fuels might lower fuel costs, but if a plant isn’t carefully optimized to handle a wider range of fuel types than were originally anticipated, the resulting increase in O&M costs could forestall lower power prices at the busbar.
Fuel flexibility consequences
Orlando Utilities Commission’s (OUC’s) Stanton Energy Center (SEC), located about 13 miles southeast of Orlando, features two 450-MW coal-fired plants and a 656-MW natural gas–fired combined-cycle plant (Figure 1). SEC has elected to fire spot market fuels with an extremely wide variation in quality over the past few years while attempting to maintain historic levels of plant reliability.
1. Fuel flexibility required. The Orlando Utilities Commission (OUC), Florida’s second-largest municipal utility, owns the two coal-fired plants at the Stanton Energy Center (SEC), commissioned in 1987 and 1996. A consortium of OUC, Southern Company, Florida Municipal Power Agency, and Kissimmee Utility Authority developed a third, gas-fired combined-cycle plant. SEC is a zero-water-discharge facility using about 10 million gallons of water a day from a nearby wastewater treatment plant. Courtesy: Orlando Utilities Commission
The plant’s challenge was to improve its systems and procedures to become fuel flexible enough to reliably burn a wide variety of fuels purchased on the spot market. This required SEC staff to quickly deal with the inevitable fuel-related problems—such as waterwall wastage, tube exfoliation and failures in the secondary superheater, and slagging and fouling in the furnace and convection section—before they became critical. The key to eradicating these problems, or at least making them manageable, has been SEC’s long-term plant improvement program to optimize the performance and life of the boiler and key components for lower-quality fuels.
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