Dominion Generation (DG) has installed selective catalytic reduction (SCR) systems on many of the large coal-fired generating units it operates. The catalyst used has an SO2 to SO3 oxidation rate of about 1%, which roughly doubles the SO3 concentration at the outlet of the boiler economizers. The magnitude of the increase was proportional to the […]
Flyash and condensed sulfur trioxide (SO3) are the major components of flue gas that contribute to the opacity of a coal plant’s stack emissions (stack opacity). Estimates are that 75% to 85% of bituminous coal-fired plants with selective catalytic reduction (SCR) and/or wet flue gas desulfurization (FGD) systems are likely to produce enough SO3 vapor […]
Using a selective catalytic reduction (SCR) system to reduce the emissions of nitrogen oxides (NOx) from a coal-fired power plant is rapidly becoming the norm, rather than the exception. But for many plants, adding an SCR system has unintended consequences: greater oxidation of sulfur dioxide (SO2) to sulfur trioxide (SO3), and a rise in stack […]
As gencos seek to improve plant reliability and availability, many are turning to on-line condition monitoring for help. Huge advances in the capabilities of on-line diagnostics have occurred over the past five years. By using this technology, plant personnel can spot early warning signs of impending equipment failure and take action to correct the underlying […]
In the last issue of COAL POWER, I urged readers to give coal handling the priority it deserves. The coal yard warrants as much attention as boilers and combustion systems, turbine-generators and auxiliaries, and postcombustion emissions control — the other three "zones" within the plant perimeter — because it is an equally valuable business unit. […]
The big buzz still echoing through world of coal-fired generation is the move by two big-bucks private equity investors to take TXU Corp. off the public market, including scuttling announced plans for eight new pulverized coal – fired plants. That leaves alive plans for three new units at TXU’s existing Sandow and Oak Grove sites. […]
Carbon capture and sequestration (CCS) have elbowed their way into the nation’s lexicon with the rise in concern over climate change. But few of the journalists who are hyping global warming have taken the trouble to learn the ins and outs of producing affordable electricity from coal. Citizens of the industrialized world now wring their […]
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.
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.
The welds on superheater and reheater headers are arguably the most stressed parts of a modern steam plant. For that reason, it’s surprising that they also may be the most under-inspected. Cracks are rare, but they can be repaired if found early. One plant avoided a long forced outage to replace a reheater outlet header by using the correct condition assessments and welding techniques.