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New Classifier Patented

LP Amina announces new patent for Coal-Fired Power Plants

 

Many coal-fired power plants including a large number of plants in the USA and China use external classifiers to segregate coal particles exiting the pulverizers to a size that optimizes combustion and unit efficiency. In March 2010, LP Amina filed a patent in China and then in July 2010 the US for an improved external classifier that increases classification efficiency by 20% and reduces pressure loss across the classifier by 50%, thus providing significant plant efficiency improvements.

Coal-fired power plants are carefully designed to ensure that fine coal particles flow through the boiler and are completely combusted at just the right location to insure that maximum energy is released; increasing energy efficiency and making the combusted coal ash easier to remove and more valuable for industrial processes such as cement production. A high percentage of large particle-sized coal released from the pulverizer pass through the boiler to be insufficiently combusted, wasting a valuable resource and making ash handling more problematic and costly. The classifier also need to be designed in such a manner that pressure loss is minimized, allowing the FD fans to work more efficiently providing air needed for coal combustion and producing megawatts, while minimizing fan load and reducing fan motor power consumption.

With these issues in mind LP Amina identified an opportunity to improve the traditional external classifier design in use at many coal-fired power stations. Many power plants make use of an external Spindle top type classifier (figure 1). Due to physical limitations inherent in this device and the inability ofthe device to be adapted to different pulverizer configurations the deficiencies inherent in this type of classifier result in a large percentage of oversized coal particles and less than ideal particle uniformity. The Spindle top classifier design also restricts air flow, creating excessive air pressure drop and often forcing the plant’s fans to waste unnecessary kilowatts trying to push air through the classifier and into the boilers while providing less than optimum combustion air. All of these factors add cost and reduce power plant reliability.

LP Amina developed computational fluid dynamics (CFD) based modeling techniques to analyze the limitations of conventional external classifiers and design a retrofit program for classifier improvement that can be adapted to existing spindle top classifiers. This new classifier design is an attractive option to those plants with external classifiers. The LP Amina retrofit program offers the prospect of increasing the proportion of coal pulverized to correct particle size (fineness) and reducing fan pressure losses. These benefits improve the operability of many coal fired-power plants, increase energy efficiency and reduce costs.

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