Plant Design

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 […]

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 […]

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 […]

In early 2003 the United States announced its plans to build a zero-emission prototype of the fossil fuel power plant of the future called FutureGen. It is one of the boldest steps toward a pollution-free energy future ever taken by the U.S. It has the potential to be one of the most important advances in […]

New flue gas desulfurization (FGD) units are being installed at utilities in many parts of the U.S. and a large percentage of the new scrubbers are of the wet limestone type. Although wet limestone scrubbing is a well-developed technology, it may be unfamiliar to employees at plants that have previously not required scrubbers. This article […]

Design techniques and operating experience with Powder River Basin (PRB) coals have advanced significantly over the past 35 years for boilers that were originally designed for this fuel. Today, boiler installations looking to effectively utilize PRB coals fall into two primary categories: units that were initially designed for bituminous or other coals and units that […]

The University of Iowa (UI) Biomass Fuel Project has produced significant reductions in greenhouse gas emissions, regulated boiler stack emissions, and purchased energy costs. The project utilizes a renewable, biomass fuel source and provides an opportunity for UI to partner with a local industry. UI was approached by Quaker Oats Co., Cedar Rapids Facility in […]