Rock Products

JUL 2017

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22 • ROCK products • July 2017 www.rockproducts.com HANDLING DUST R espiratory issues associated with limestone extraction and processing are among the oldest recognized work- place safety hazards. Modern limestone handlers often take a number of safety measures, including masks, respirators, enclosed processing systems, sprinklers, hoses and/or fre- quent cleaning schedules. Beyond potentially increasing the cost of operation, cumber- some equipment and unpleasant cleaning procedures all add to processing costs and can take a toll on staff morale. How- ever, some operators, like those at the Singleton Birch Ltd. quicklime production facility in east central United Kingdom, are turning to solutions that address the dust at the point of emission to reduce risk and enhance workplace safety. "Plant safety is one of our chief concerns," said Chris Smith, lime maintenance leader at Singleton Birch. "We strive to balance productivity with a good working environment, and addressing dust emissions is a high priority." The Process Established in 1815 at the Melton Ross Quarry outside of Bar- netby, UK, Singleton Birch has grown into a global provider of quicklime, chalk products and services for steel produc- tion, land stabilization, acid neutralization, water treatment and building renders/mortars. The addition of modern kilns and equipment to the existing infrastructure of the plant has allowed the organization to provide quicklime and other products to many new and emerging markets. The company currently produces 1.5 million mtpy (1.65 mil- lion tpy) of processed limestone and chalk, as well as 300,000 mtpy (330,700 tpy) of calcium oxide products. The limestone is quarried from Melton Rose a short distance away and transported to the facility, where it is crushed to 150-mm minus (6-in. minus) and transferred to the kiln. For approximately 16 hours the aggregate is passed through the twin-shaft parallel-flow regenerative kiln running at about 1,000 C (1,832 F) using natural gas as the fuel source. The calcined soft-burned lime (slowly heated limestone with small cracks where CO2 has escaped during the calcination process) is discharged into another crusher and reduced to 50-mm minus (2-in. minus), and then either deposited into hoppers for bulk delivery or transferred to the GLC1 con- veyor. This system transports the limestone to conveyors leading to either the crushing and screening operation or the milling plant. "We've found soft burned material will produce more fines than harder burned material," Smith pointed out. "The increased production volume has naturally resulted in more dust, and this is very apparent on GLC1." Dusty Drop The dual transfer chute system that loads the GLC1 con- veyor is a 7- to 8-m (approximately 25-ft.) dead drop onto a troughed 600-mm (24-in.) wide belt. Supported by heavy- duty cradles with polyurethane impact bars, the loading zone was surrounded by an unsealed chute with no settling zone, but had two top-mounted mechanical dust filtration systems. Running at 2 mps (393 fpm) and transporting 100 mtph (110 tph) of dry calcined aggregate, the impact caused dust to billow out the sides of the chute and fill the area. Doing Away With Dust A Singleton Birch Quarry Took Control of Fugitive Dust Emissions With a Combination of Experience and Technology. By Mark S. Kuhar Piled high enough to encapsulate the tail pulley and belt, the dust was a serious problem.

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