AERIAL SEPARATOR (EN: air separator; DE: Luftscheider; FR: separateur pneumatique; ES: separador neumático; RU: воздушный сепаратор) is the device for the aerial classification. The separation within the aerial separator is performed within the turbulent two-phase streams, simultaneously according to the size, density, and shape of the particles, which are constituting the original mixture. According to the principle of the action, they distinguish the following classes of the aerial separators: centrifugal, gravitational, cascaded, and combined.
The types of the centrifugal aerial separators are: with the rotating plates; with the stationary zone of the separation; with the rotating zone of the separation, the aerial separators with the rotating plates (see the Figure # 1), namely, the apparatuses with the stationary zone of the separation, and with the internal circulation of the stream; the performance of these separators is up to 120 tonnes per hour, with the diameter of the casing of 5 metres; the disadvantage is the relatively low degree of the separation.
The aerial separators of this type with the external circulation have the higher performance, but are bulky, complicated in operation, and rarely used within the industry. The centrifugal aerial separators with the stationary zone of the separation are characterized by the existence of the flat or spatial rotating whirling stream of the air; the particles exist in the state of the dynamic equilibrium, during which the smaller particles arrive into the central drain, and the larger particles arrive onto the periphery; the performance is comparatively low (approximately 160 tonnes per hour), the effectiveness is average (the separation ability is approximately 0.4). There are most widespread the aerial separators with the rotating zone of the separation (for example, of the "Mikroplex" type, West Germany), which has the shape of the torus with the rectangular cross section. The zone is formed by the flat rotating walls. The original material arrives from the periphery through the gu iding channel into the working space. The tiny fractions, together with the air, are sucked out through the central drain, while the large fractions are thrown onto the periphery, and are removed from the apparatus using the auger conveyor. The performance is up to 5 tonnes per hour, the separation ability is approximately 0.6.
They sub-divide the gravitational aerial separators into the following groups: cross-streamed (deflecting); rotational, with the countercurrent (of the equilibrium type). Within the cross-streamed aerial separators of this class, the mixture is separated within the horizontal stream of the air, which is moving within the chamber with the special partitions. The aerial separators of this type ensure the significant performance (up to 200 tonnes per hour), but possess the extremely low separation ability (0.3-0.35). The classification of the material within the rotational aerial separators proceeds within the inclined rising streams. Such apparatuses are more effective, than the cross-streamed apparatuses, but they do not allow to achieve the high performance within the single aggregate (10 tonnes per hour); the separation ability of these apparatuses is 0.65. The principle of the countercurrent (equilibrium) classification within the gravitational field is implemented, as a rule, w ithin the hollow apparatus with the circular (rectangular) cross section, or within the analogous casing, which has been partitioned using the inclined grating. The apparatuses of this type have the average separation ability under the moderate loads. The maximal performance is 15 tonnes per hour, the separation ability is 0.75-0.8.
The peculiarity of the structures of the centrifugal separation chambers, and of the gravitational aerial separators, is such, that the material is, as a rule, subjected to the single-stage classification. The effectiveness of the separation increases significantly with the increasing of the multiplicity of this process. The realization of this principle is performed within the cascaded aerial separators, the apparatuses of which comprise the separation stages of the single type. The most effective structures (see the Figure # 2, and the Figure # 3) are the so-called aerial separators of the shelving type (USSR), and of the "zigzag" type (West Germany).
The performance of the aerial separators is up to 100 tonnes per hour per the single aggregate. These apparatuses possess the high separation ability, which increases with the increasing of the quantity of the stages within the cascade. There are yet more highly effective the apparatuses with the combined cascade, namely, the so-called combined aerial separators (see the Figure # 4).
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