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Pre-treatment, Concentration, and Enrichment of Precious Metals from Urban Mine Resources
Published in Sadia Ilyas, Hyunjung Kim, Rajiv Ranjan Srivastava, Sustainable Urban Mining of Precious Metals, 2021
Hyunjung Kim, Sadia Ilyas, Rajiv Ranjan Srivastava
Manual and automatic sensor-based sorting systems can be used for recycling of various material from urban-mined sources. Hand sorting is still a popular method in small-scale operations but mechanical sorting (using optical, electronic, and radioactive properties) is in common use for large-scale industrial applications. This is possibly due to the distinct contrast between the physical properties of valuable material and gangue material. The critical attributes are light reflectance, ultraviolet rays, magnetism, conductivity, and X-ray luminescence. The main objective of mechanical sorting is to reduce the bulk of the raw material by rejecting large volumes of waste material at an early stage. The process utilizes a two-stage separation process. The first stage involves primary crushing of feed to liberate pre-concentrate and barren rejects. In the second stage, re-crushing, grinding, and processing is performed to produce final concentrates and tailings. This two-stage operation substantially lowers the cost of large volumes of crushing and grinding, and the subsequent process of upgrading to produce marketable final concentrates. Fragments of desired size from urban-mined sources, preferably washed, move on a conveyor belt or vibrating feeders at uniform speed and are released, while the stream of feed material particles maintains a natural flow. Energy elements like light rays, laser beams, and X-rays converge from the source and reflect from the surface of the feed material passing through the sorting zone. The nature of the reflectance is sensed by the detector system, which sends signals to the computer. The amplified signal activates an air jet at the right instant and at the correct intensity to eject the particle from the stream. Accepted and rejected particles are dropped in separate stacks around a conical splitter. A fully automatic electronic sorting device comprises an integrated circuit of an energy source, a process computer, a detector, and an ejector (Fuerstenau and Han, 2003; Ammen, 1997; Wills and Finch, 2015; Kaya, 2018) (Figure 2.16).
Optical sorting of lignite and its effects on process economics
Published in International Journal of Coal Preparation and Utilization, 2018
Ergin Gülcan, Özcan Yıldırım Gülsoy
Considering the operational difficulties of wet lignite processing, automated optical sorting of lignite is a strong candidate to compete with HMS. X-ray transmission (XRT) and dual-energy XRT sorters (Kleine 2010), or laser-based sensing for coal processing (Feng et al. 2013) are proven dry alternatives for coal beneficiation and offer high recovery. Among known sensor-based sorting techniques, visible light-color (VIS, operating in 400–700 nm wavelength range) and near-infrared (NIR, operating in 700–3000 nm wavelength range) sorting are the most common and widely used methods (Daljmin et al. 2003; Wotruba and Riedel 2006). They are also fast and accurate, easier to use, and more economic in comparison with XRT and laser-based techniques. Although VIS and NIR sorting of minerals such as borate, carbonate, talc, etc., is successful, and industrial implementations are in process (Robben and Wotruba 2010), very rare studies have been performed to reveal the possibility of VIS/NIR sorting implementation on lignite processing to date (Gülcan and Gülsoy 2014).