363 Reflux classifier (RC)—one of the most recent developed separators that is widely utilized in coal cleaning for particle size, 2 +0.10 mm—is a combination of liquid fluidized bed, autogenous dense medium and lamella settler. RC consists of a set of parallel inclined channels located above a vertical section with fluidizing water added through the base. The FBS acts as the primary density-based separator whereas the lamella section acts the secondary separation zone in the RC. In the fluidization section, rising fluidization water keeps incoming coal particles in the fluidized condition and these particles settle against the fluidization water similar to the separators explained earlier. The fluidization section provides a uniform flow of particles to each inclined plate in lamella section. Laminar flow could be promoted by a closely spaced channel due to laminar-shear mechanism that make the segregation of fine high ash particles become packed in the fluidization chamber while light coals are transported upwards to the overflow. This phenomenon develops a reflux action because of fluidized particles segregating onto the inclined plates and returning to the fluidized zone below. This self-recycling effect eliminates the misplacement of materials, significant suppression of the effect of particle size, thus enhancing the product quality. RC has several advantages over other conventional FBS which includes higher separation efficiency, robust operation, less floor space requirement, consistency in product grade and high throughput. Inclined channels have a higher throughput capacity compared to a conventional FBS due to their increased effective settling area, so-called Boycott effect. According to the Boycott effect, segregation and sedimentation of solid particles can be improved using inclined channels. These inclined channels provide a larger effective settling area for solid particles and hence improve their settling rate compared to vertical channels [10]. Reflux Classifier (RC) is normally used to treat coal of -2.0 mm size and is effective down to 0.15 mm and generally targeted size fraction has a top-to-bottom ratio of 8:1. It exhibits significantly lower Ep values (0.05-0.1). The variation of Ep and cut-density with particle size range (PSD) and even fine particle size is very low. It can treat coal at lower cutdensity and at higher efficiency with lower ash, has led to widespread adoption among FBS for beneficiation of intermediate size coal. Therefore, in this process flowsheet Reflux Classifier has been used for beneficiating 1-0.25 mm coal instead of TBS. Figure 7- Column Flotation Schematic
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