Material Handling in Coal Plants” was Hot Topic Hour on February 10, 2011
Material handling is a critical component of the efficient operation of a modern coal-fired power plant. Power plants once handling basically coal and ash are now faced with handling all new types of liquids and solids to meet air and water quality requirements. The modern plant must now deal with the transportation, loading/unloading, storage, sizing, blending and injection of fuels including coal and various biomass products into the boiler as well as lime, limestone or gypsum and various others liquids such as ammonia or sulfuric acid and solids such as the various forms of activated carbon into the boiler and air pollution control equipment. Many of these materials utilize very different material handling equipment and have their own unique set of problems related to their transportation and use. With coal switching and coal blending frequently being used to take advantage of reduced fuel costs and to reduce air emissions, the pulverizer, conveyor and injection equipment must be capable of handling a wide range of coals with varying physical characteristics, moisture levels and ash properties. Getting the materials to the proper place in the plant in the proper configuration is only part of the problem. The plant also needs to collect, condition, transport and stockpile or load the waste products from the combustion process and air and water pollution control systems. Add to this mix the need to improve plant efficiency by reducing energy used for these material handling systems and issues such as shortages of water, zero effluent discharge regulations and the need to eliminate ash ponds and the material handling issue becomes critical to the efficient operation of the plant.
The following speakers addressed the various material handling systems and equipment available for all of the materials used in a coal-fired power plant, the advantages or disadvantages of each, their operating experience with the equipment, potential problems to avoid during design and operation and new technology available to improve performance while reducing energy consumed and maintenance requirements.
Bob Chase, Product Manager for Posimetric Feeders at Pennsylvania Crusher (K-Tron International Inc), described their Posimetric® Feeder. Pennsylvania Crusher’s Posimetric® Feeder is an example of how simplicity of design can lead to improved operational and maintenance performance. With a single moving part, the Posimetric feeds coal and other bulk materials by taking advantage of, rather than fighting, the material’s natural tendency to bridge over an opening. Its compact size makes it ideal for retrofit situations and because the basic feeder may be duplicated on a single shaft, it can be designed to match other equipment in the plant. Over 300 Posimetric Feeders are in service in the USA feeding pulverizers, crushers and takeaway conveyors. When utilities switch to PRB coal, the Posimetric Feeder becomes a way to solve the dust problem. It is also a solution when feeding a combination of coal and biomass.
Jim Patterson, Pneumatic Conveying Department FLSmidth, Inc. - Pneumatic Transport, described a pressure conveying system which utilizes air gravity conveyors and dry screw pumps to continuously convey ash to a dry silo destination. The system has proven to have very low maintenance requirements and avoids ash residence time in the hoppers of the primary dust collector. In order for many existing coal-fired power plants to remain in compliance with respect to future regulations on water usage and final placement of CCR’s, dry fly ash handling systems may need to be retrofit to existing ESPs and baghouses. The A2P system is also capable of handling combinations of sorbent and flyash. Adjustments to flow and pressure can allow the system to handle the new mix.
Geoff Conroy, President of Aumund Corporation, discussed the most up to date methods of coal handling for large stockpiles and multi-pile reclaim applications to achieve coal blending, both within the pile and from several piles. A large number of systems are installed in Europe but there are a growing number in the U.S. The gypsum stacking system, widely used in Europe, is also being installed on FGD systems in the U.S.
Charles (Charlie) S. Alack, President and CEO of Semi-Bulk Systems, Inc., discussed the FGD limestone slurry process. He compared new process technology to the traditional processes – pulverized limestone with Vacucam® ejector mixers versus crushed limestone and wet ball mills. The system is also flexible to incorporate other additives which must be converted from a dry to a slurry state. So if there needs to be activated carbon added to the limestone slurry to separate the mercury, it could be introduced to the system.
The Bios, Photos and Abstracts
are linked below.
BIOS, PHOTOS, ABSTRACTS - February 10, 2011