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Engineered Chutes Reduce Dust and Maintenance

Posted on: Saturday, 1 April 2006, 03:02 CST

By Blankinship, Steve

The increasing trend to switch to or blend Powder River Basin (PRB) coal at plants designed for other fuels often requires coal yard upgrades to improve coal handling. An important element for improving the efficiency and safety of coal yards is the design of the coal chutes themselves. Today's coal handling chutes can incorporate technology far superior to chutes installed when a plant was first built. These chutes can handle dramatically higher volumes of coal and eliminate plugging that can lead to downtime, spontaneous combustion and high maintenance costs. Perhaps most importantly, engineered material transfer technology can significantly reduce health hazards posed by dust by keeping dust particles entrained in the fuel flow.

Crushed coal is transferred to a receiving belt at the point in the transfer chute where the spoon hails the coal. The pulverized coal maintains a defined, rigid structure producing little or no dust. Photo courtesy of Parramatta.

One company offering sophisticated chute technology is Parramatta. The company recently installed new chute systems at the Schaefer and Baily plants operated by NiSource subsidiary NIPSCO and at Ontario Power Company's Lampton plant.

"Our design for engineered transfer points evolved in Australia and was introduced into the U.S. market about three years ago," says Martin O'Neill, business development manager for Parramatta. "The idea of the engineered transfer point is to take the material from the discharge belt, deliver it to the receiving belt in the direction and speed of the receiving belt, do away with dust and eliminate the need for traditional dust suppression paraphernalia such as distilling boxes and skirting systems."

0'NeUl says the technology works for all coals and is especially beneficial for coals that tend to produce high levels of respiratory dust. He believes it will work with lignite too, although the company has not yet installed a system at a lignite-fired plant.

He explains how Parramatta's Flexco engineered chutes represent a completely different approach to traditional coal chutes. "The traditional transfer system is designed to contain material as it goes from one belt to the next belt. Typically, the coal comes off the head pulley at a certain velocity and bangs into a rock box designed to slow the material down. But it does not control the velocity and movement of the material. Our system controls the velocity and movement of the material as it comes off the head pulley and all the way through the chute system."

Coal dust represents a health hazard to plant workers. Both the Mine Safety and Health Administration (MSHA) and Occupational Safety and Health Administration enforce breathable dust level limits. "With the traditional transfer system, the material bangs into the interior surfaces of the chute causing degradation and dust," says John Winkelman, vice president of engineering for Flexco. "Our system uses an engineered chute configuration that eliminates direct impact, material degradation and dust generation." Parramatta reports that dust readings taken at several locations where Flexco systems have been installed was well below the MSHA requirements of 2 mg/cubic meter.

Winkelman explains how the proprietary shape and location of various elements of the system relative to the material flow stream allow the material to be collected off the discharge belt into what appears to be a solid block of material. "And we control that block of material until it is deposited onto the receiving belt"

Modem chute technology can also facilitate added throughput demand placed on coal yards. Plants originally designed to handle 600 tons per hour are likely to be handling 20 to 30 percent more today. Because the new chute technology retards blockage and build up, availability increases, maintenance is reduced and spontaneous combustion is less likely to occur. And because dust is all but eliminated, clean-up costs go down dramatically. Dave Gushing, site project technician for the Lampton plant, says estimated annual maintenance savings due to decreased cleanup is $25,000 at one transfer point alone.

Copyright PennWell Publishing Company Mar 2006

Source: Power Engineering

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