Coal Age

JUN 2013

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coarse coal Dry Coal Sorting Next generation technology for coal preparation BY MICHAEL KISER, GERALD LUTTRELL AND CHARLES D. ROOS Electronic ore sorters were first introduced to the minerals processing industry in the late 1940s. Since that time, faster microprocessors, improved sensors and lower equipment costs have allowed this unique technology to evolve and become commercially attractive for a variety of applications. Recent estimates indicate that nearly 300 industrial-scale sorters are now used worldwide for ore concentration. Electronic sorters use specially-designed sensors to evaluate the quality of feed particles that are spread across the surface of a moving conveyor belt. High speed microprocessors use the sensor data to control pneumatic actuators located at the end of the conveyor. The pneumatic actuators are sequenced so that particles meeting the target quality are diverted into the product stream. This article describes the DriJet sorting technology, which has been designed specifically for coal cleaning applications. This system offers many benefits for coarse coal upgrading including mechanical simplicity, high capacity, low cost and minimal environmental impacts. Recent test data from both run-of-mine coal and waste coal upgrading applications will be presented. Mineral Separation Technologies Inc. The essential working features of this innovative technology are illustrated in Figure 1. During operation, coal is fed onto a conveyor belt as a thin layer. The bed of material passes through a proprietary dual energy X-ray analyzer that subjects the particles to hundreds of sequential X-ray scans. The X-rays transmit through the bed of solids in proportion to the atomic number of the components present in each particle. As shown in Figure 2, this phenomenon makes it possible to distinguish coal (organic matter composed mostly of carbon with a low atomic number) from rock (inorganic mineral matter composed of various elements such as silicon and aluminum with higher atomic numbers). The resolution and speed of the scanner and associated electronics is of sufficient quality so that a compositional profile of each particle can be reconstructed in fractions of a second. Once identified, controlled microbursts of compressed air from a horizontal array of pneumatically actuated jets divert unwanted particles of rock into the reject stream, while coal particles follow their normal trajectory into the clean coal product stream. Introduction Coal preparation offers may attractive benefits including lower transportation costs, improved utilization properties and reduced emissions of particulate and gaseous pollutants (Akers, 1996; Couch, 1995). However, the industry also faces several challenges associated with increased solid waste disposal requirements and higher demands for process water (Meenan, 2005, Couch, 2000; Ore, 2002; Gardner et al., 2003). To address these issues, several groups have begun to actively develop new technologies that are capable of upgrading run-of-mine coals without any water (Luttrell, 2008). One particularly promising process is electronic sorting. Electronic ore sorters were first introduced to the minerals processing industry in the late 1940s. Since that time, faster microprocessors, improved sensors and lower equipment costs have allowed this unique technology to evolve and become commercially attractive for a variety of applications. Recent estimates indicate that nearly 300 industrial-scale sorters are now used worldwide in the minerals industries for ore concentration. Electronic sorters use specially designed sensors to evaluate the quality of feed particles that are spread across the surface of a moving conveyor belt. High-speed microprocessors use the sensor data to control pneumatic actuators located at the end of the conveyor. The pneumatic actuators are sequenced so that particles meeting the target quality are diverted into the product stream. This system offers many benefits for coarse coal upgrading including mechanical simplicity, high capacity, low cost and minimal environmental impacts. Moreover, the compact size and low unit cost of sorter technology improves the viability of separating rock from run-of-mine coal as close to the working face as possible using a system that is integrated within the production process so that the surface disposal of wastes and water demands could be minimized. One of the newest and most highly advanced coal sorting technologies is the DriJet separator, which is marketed commercially by 48 www.coalage.com Figure 1: Schematic of the X-ray sorting process. Figure 2: X-ray images of run-of-mine feed, rejected material and clean coal. June 2013

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