Coal

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.