Environmental

Part I of this three-part series (POWER, October 2006) explored the negative impacts of sulfur trioxide (SO₃) on the operation and maintenance of back-end plant equipment. In this issue, we list and quantify the likely and potential benefits of limiting the concentration of SO₃ in flue gas to 3 ppm at the entrance to the air heater. Part III—to appear in the April 2007 issue—will describe the characteristics of an optimal SO₃ removal technology and present the technical details and operating experience of one patented process that has worked successfully at a half-dozen plants for up to three years.

Environmentally benign disposal of coal combustion products/by-products (CCPs) such as flyash and bottom ash has been a problem since the first coal-fired power plant went on-line. In recent years, ways have been developed to recycle CCPs into useful commercial products like bricks and roadbase. This article describes an innovative State of Maryland program that is putting CCPs to yet another use: stabilizing abandoned mines to permanently sequester acids and harmful metals.

As emissions caps drop, technological solutions must become increasingly effective and efficient. Researchers, equipment vendors, and plant operators are exploring alternatives to SCR and SNCR, with a view to reducing the overall costs of NO_x reduction. They’ve also achieved 95% to 99% removal of SO₃, with no visible plume opacity.

When Charles Dickens began A Tale of Two Cities with, "It was the best of times, it was the worst of times," he was referring to the French Revolution of the late 18th century. But Dickens’ words apply equally well to the American generation industry of the late 20th century. A decade of overbuilding U.S. […]

Renewables require rethinking just about everything/Torque-splitting drive train improves wind turbine reliability/Waste gas–burning engines reach milestone/Hybrid power plant targets pipeline losses/Power from paint/Gulf Coast Power Association conference report/Pat Wood talks about the challenges facing ERCOT

  What’s in a name? Plenty, if the word is "renewable." Intuitively, most people outside the energy industry consider hydroelectric power "renewable." The dictionary defines the word as follows: "capable of being replaced by natural ecological cycles." Accordingly, rainwater should indisputably qualify as renewable. Yet since the early days of renewable portfolio objectives, most hydro […]

The visible consequences of sulfuric acid aerosol emissions—opaque stack emissions called “blue plumes”—are merely the tip of an iceberg. In sufficient concentration, SO3 also can increase corrosion and fouling of equipment and components downstream of the furnace while decreasing their efficiency and penalizing overall plant heat rate.

The O&M staff of AES Westover Station wisely took a holistic approach to optimizing combustion within Unit 8’s boiler in order to reduce its NO_x emissions while maintaining acceptable levels of carbon-in-ash content. The results of major modifications—centered on the addition of a fan-boosted overfire air system—were a 60% reduction in NO_x levels, improved unit reliability, and a project payback period measured in months rather than years. As this project proved, the whole is more than the sum of its parts.

For some gencos, the dearth of operating experience for integrated gasification combined-cycle plants adds too much uncertainty to the risk/reward equation for new-capacity technology options. For others, the possibility of being able to comply with air pollution limits as far out as 2018, as well as to meet all-but-certain CO₂ caps, makes IGCC well worth investing in—now.

Concerns about global climate change have prompted interest in reducing or eliminating the carbon dioxide (CO₂) emissions of fossil fuel-fired power plants. Here’s a guide to the technology and economics of three CO₂ capture methods: postcombustion separation of CO₂ from flue gas (applicable to existing plants), and oxygen-fired combustion and precombustion capture (suitable for new coal-fired capacity, including IGCC plants).