The compliance clock is ticking / First-class maintenance in a developing country / Bypass losses squander big bucks / Revised operating procedures
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.
Safety issues related to the use of gaseous chlorine for disinfecting cooling water are pushing plant operators to examine other alternatives. Two units of Cardinal Generating Station recently switched to a liquid chlorination system, with pumpless vacuum injection, that was easy to install and has proven reliable. That switch has resulted in one less safety headache for the operations staff and one less invitation to regulatory scrutiny.
Ongoing maintenance is critical to the performance and longevity of underwater structures such as cooling water intake tunnels. Commercial divers or robotic vehicles can do the needed inspections, but such manual methods require a costly plant shutdown and provide only qualitative results. ASI Group Ltd. has designed and built an advanced, dual-axis sonar system that works in fast-moving water and can deliver quantitative data about the extent and location of debris buildup on submerged assets.
Mandatory standards advance / To drain or not to drain / Practical aspects of burning landfill gas / Time management
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 […]
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 […]
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 […]