Coal

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 […]

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. […]

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. […]

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 […]

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 […]

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 […]

A systematic, performance-driven maintenance program for optimizing combustion can achieve great results. The challenge for an O&M staff is deciding which proven strategy and tactics for reducing NO_x and improving plant reliability to adapt and implement. The structured approach presented here has proven its worth at several plants that have wrestled with problems similar to yours.

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.

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.

DOE walks the clean coal talk / For Swedish nuke, a case of mistaken identity / Siemens completes big CHP plant / E.ON bets big on coal / BP Solar expands Maryland plant / GE scores big turbine deals / PSNH switches from coal to wood / EPRI tests solid-state current limiter / POWER digest

Forecasting the direction of the U.S. electric power industry for 2007, much less the distant future, is like defining a velocity vector; doing so requires a direction and speed to delineate progress. In this special report, POWER’s first stab at prognostication, the editors look at current industry indicators and draw conclusions based on their more than 100 years of experience. To borrow verbatim the title of basketball legend Charles Barkley’s book: I May Be Wrong but I Doubt It.

Following the money invested in projects is a viable way to compare growth trends for power projects using the four major generation types: coal, natural gas, nuclear, and renewable.

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. […]

To borrow shamelessly from Charles Dickens, one of my favorite authors, for coal in 2006, "It was the best of times, it was the worst of times." No Escape The year began in horror. On January 2, most likely a result of a severe lightning strike, methane gas in the International Coal Group’s Sago Mine […]

Over the past 17 years — dating back to the 1990 Clean Air Act Amendments and including the introduction of retail competition — coal-fired power plants have become much cleaner and more efficient. Utilities have spent many billions of dollars to install pollution controls for regulatory reasons, and only slightly less to upgrade turbine-generators and […]

When you receive a shipment, you don’t wait weeks to see whether you got what you paid for — do you? J.M. Stuart Generating Station doesn’t, but it used to. Since coming on-line in the early 1970s, the big plant, on the Ohio River near Aberdeen, Ohio, mechanically sampled coal shipments as they reached the […]

If coal leaving a pulverizer isn’t dry, it may plug up the coal pipes leading to the boiler. The coal-drying process in a pulverizer is similar to that used by flash dryers. Certain coals should be preheated to make them more combustible. Generally, preheating is done on higher rank coals — those with a low […]

Historically, cyclone-fired boilers have been characterized as big emitters of NOx due to the very high temperatures in their primary combustion zone. Uncontrolled levels from 0.8 to 1.9 lb/mmBtu have been typical. The design of cyclone-fired units makes them impossible to retrofit with standard low-NOx burners. Prior to 1997, the conventional wisdom was that cyclone […]

Layering NOx control technologies can reduce a coal-fired unit’s NOx emissions to levels achievable by selective catalytic reduction alone. Advanced Combustion Technology Inc. (ACT) (www.advancedcombustion.net) has demonstrated that using several in combination can cut emissions from boilers firing eastern bituminous coal or No. 6 oil to less than 0.15 lb/mmBtu. The following two case studies […]

Large-particle ash (LPA), also called popcorn ash (Figure 1), is a serious concern for many coal-fired utility boiler operators who have retrofitted their unit(s) with a high-dust selective catalytic reduction (SCR) system. LPA formed in the boiler can easily carry over into the SCR reactor (Figure 2), where it often causes catalyst erosion damage and […]

The February 1907 issue of POWER magazine reported on the construction of a new coal-fired steam engine plant on the Merrimac River outside of Lawrence, Mass. According to the plant’s owner, "the simplest and most flexible means for handling coal… to the furnace is by animal muscle… that brings the coal to the firing floor […]

Safeguarding coal-handling assets;
Giant wind turbine hard to bear

First live superconducting cable / Biggest CO2 storage project / Largest hydrogen-fueled plants / Record run for fuel cell cogen system / Largest PV plant still in Bavaria / Luz returns to U.S. / POWER digest

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.

Fuel flexibility isn’t free. Whether you’re equipping a new power plant to burn more than one type of coal or retrofitting an existing plant to handle coal blends, you’ll have to spend time and money to ensure that all three functions performed by its coal-handling system—unloading, stockout, and reclaim—are up to the task. The first half of this article lays out the available options for configuring each subsystem to support blending. The second half describes, in words and pictures, how 12 power plants—both new and old—address the issue.

Slagging and fouling of furnaces and boilers’ convective pass top the list of costly coal plant O&M problems. Although sootblowing is a tried and true solution, running sootblowers too often can erode boiler tubes. Lehigh University’s Energy Research Center has developed an "expert" sootblowing system that has outperformed experienced operators’ "seat of their pants" sootblowing procedures on two head-to-head field tests.

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.