Coal Beneficiation via the Tapered Fluidized Bed Using Magnetite with a Wide Size Range
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Coal Beneficiation via the Tapered Fluidized Bed Using Magnetite with a Wide Size Range Xuchen Fan 1 & Chenyang Zhou 1 & Liang Dong 1 & Chenlong Duan 1 & Yuemin Zhao 1 Received: 14 August 2019 / Accepted: 18 February 2020 # Society for Mining, Metallurgy & Exploration Inc. 2020
Abstract A gas–solid fluidized bed using magnetite particles is an effective methodology for coal beneficiation in the field of dry coal cleaning. Broadening the size range of magnetite used in the bed decreases medium preparation cost. In this study, a tapered fluidized bed was used to investigate a magnetite particle size range of −0.5 + 0.074 mm. The results showed that a tapered fluidized bed effectively strengthens mixing of magnetite with a wide size range (−0.5 + 0.074 mm). The results of beneficiation experiments indicated that with increasing tapered angle, separation efficiency increased and then decreased. The highest separation efficiency was obtained at a tapered angle of 10°. The optimal results showed that the ash content of the concentrate decreased from 31.82% to 12.33% with a probable error of 0.11, which indicated that a tapered fluidized bed was efficient to improve fine coal beneficiation performance. Keywords Coal beneficiation . Tapered fluidized bed . Dense medium . Bubble behavior . Size distribution
1 Introduction Coal plays a key role in energy consumption worldwide [1–3]. However, environmental issues associated with coal combustion, such as gas emissions and acid rain, require improvements in coal quality before direct usage [4, 5]. Traditionally, wet beneficiation technologies are widely used for coal cleaning, which consume a large amount of water [6]. However, water shortages are becoming a global problem. Thus, dry beneficiation methods have attracted increasing attention in recent years [7]. One of the typical dry beneficiation techniques is a gas–solid fluidized bed. In this process, a fluidized bed having pseudo-fluid properties with a stable density is created allowing different particles to float or sink based on the principle of density stratification [8–12]. Selection of the size range of magnetite plays an important role in density stability and bubble behavior. In general, the * Xuchen Fan [email protected] * Liang Dong [email protected] 1
Key Laboratory of Coal Processing and Efficient Utilization of Ministry of Education, School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China
magnetite bottom size should be not finer than 0.074 mm, and it is difficult to recycle fine (−0.074 mm) magnetite [13, 14]. When the size range of magnetite is very wide, particle segregation by size often occurs. These result in a large density distribution in the axial direction decreasing the coal separation efficiency. To decrease the magnetite cost, −0.15 + 0.074 mm magnetite was mixed with −0.3 + 0.15 mm magnetite. Although some researchers have found that −0.3 + 0.074 mm magnetite is suitable for providing a uniform mixture [15, 16], other researchers h
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