Fluidization Characteristics of a Pulsing Dense-Phase Gas–Solid Fluidized Bed for High-Density Separation of Fine Anthracite

Abstract

Coal is one of the most important primary energy sources worldwide that requires an economic, effective, and clean preparation method. As the shortage of water resources increases, the wet beneficiation technology became questionable. The air dense medium fluidized bed (ADMFB) is a good alternative for dry coal beneficiation processes that require no water. In this account, a pulsating air flow was introduced into the ADMFB system to generate a pulsing dense-phase gas–solid fluidized bed (PDGFB). The effects of the pulsating air flow on the minimum fluidization velocity, stability of the bed density, and motion of the heavy medium were investigated. The pulsating air flow is shown to reduce the minimum of the fluidization velocity, modify the stability of the bed density, and regularize the motion of the heavy medium. Fine anthracite of −6 + 1 mm size is cleaned using PDGFB at elevated separation densities with a true value of 2.03 g/cm3 and probable error (E) of 0.09 g/cm3. In comparison to vibrated fluidized beds, PDGFB has no mechanical vibration and, hence, is advantageous in terms of the mechanical structure, easy operation, and susceptibility to lower failure.

Deagglomeration of Ultrafine Hydrophilic Nanopowder Using Low-Frequency Pulsed Fluidization

“…The lowering of the U mf is a clear indication of deagglomeration due to flow pulsation. Previously reported U mf values were 118.3 and 30.5 mm/s for unassisted fluidization and 10-s pulsation, respectively [22]. This difference can be attributed to the removal of large agglomerates due to sieving of the nanopowder sample in the present experiments.…”

“…Strategies for improving fluidization hydrodynamics of powders are often known as assisted fluidization techniques. Examples are acoustics [9][10][11][12][13][14], particle-mixing [15][16][17][18][19][20], flow pulsations [21][22][23][24][25][26][27][28][29], and mechanical vibrations [30][31][32][33][34]. In some cases, a combination of two assisted fluidization technique has been suggested [20,35].…”

“…The bed is subjected to intense periodic turbulence without requiring any additional energy input because of the change in flow rate caused by pulsation. Consequently, it has been gaining significant attention in literature [21][22][23]. When used to dry pharmaceutical granules, this technique decreases the total time of drying while enhancing bed homogeneity as compared with unassisted fluidization [24].…”

Studies on Bed Density in a Gas-Vibro Fluidized Bed for Coal Cleaning

“…Dong previously used the 232 μm magnetite powder and reported the effect of the gas pulse frequency on density variations at a fluidization number, N , of 1.2. 20 Thus, for the former particles, data were collected from the previous study for comparison. For the 110 μm magnetite powder, the bed density was analyzed at different pulse frequencies and gas velocities.…”

Hydrodynamics of Pulsed Fluidized Bed of Ultrafine Powder: Fully Collapsing Fluidized Bed

“…The common strategy used to improve the fluidization hydrodynamics is the augmentation of extra energy to the bed of particles to overcome interparticle forces, thereby promoting de-agglomeration and eliminating bed non-homogeneities. Common assisted fluidization techniques are based on the use of acoustics [4][5][6][7][8], particle-mixing [9][10][11][12][13][14][15], flow pulsations [16][17][18][19][20][21][22][23][24][25][26], and mechanical vibrations [27][28][29][30][31][32][33]. The combination of two of assisted fluidization techniques has also been suggested in some cases [15,[34][35][36].…”