Classifying – separating – and assorting solids – Fluid suspension – Gaseous
Patent
1996-10-22
1998-08-04
Terrell, William E.
Classifying, separating, and assorting solids
Fluid suspension
Gaseous
209145, 209154, 209716, B07B 400, B07B 700
Patent
active
057880832
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an elbow/countercurrent classifier according to the preamble of claim 1.
PRIOR ART
So-called air classifiers are used for the dry classification of fine-grained solids. The separating characteristic is the final velocity at which the grains fall in the air. In particular, classifiers of this type may also be used for cleaning a quantity of bulk material which is present essentially in the form of granules and contains particles of different sizes. As a result of different production processes, bulk materials may have very different size distribution ranges. Plastics are provided in the form of granules which are mixed with abraded particles and/or with dust particles. If the size of the granule particles is in the order of magnitude of from approximately 2 to 5 mm for the diameter or the length of the granules, then, in contrast, the size of the dust particles is only, for example 50 .mu.m. In the case of plastics granules, larger particles, which are also referred to as angel hair or streamers, are also present from time to time, and these may be in the form of disks, coils or spheres and have a diameter of from approximately 2 cm up to 10 cm. Such materials occur, in particular, in the case of pneumatic delivery. The granules delivered through the tube conduit rub along the tube, heat up and form adhering filaments or films which repeatedly tear away or become detached.
A known air classifier for treating such materials is described in DE 42 35 260 A1, further prior art being given in this document.
In order to treat such bulk materials, DE-OS 1 905 106 has disclosed a so-called elbow/countercurrent classifier in which the bulk material to be treated is fed to an elbow classifier via a delivery-gas stream. Here, in particular, the bulk material delivered downward in the delivery-gas stream in the elbow classifier is taken up by a separating-gas stream which is oriented in the opposite direction, deflects the delivery-gas stream upward and, in the process, carries along the lighter, smaller and, in particular, dustlike particles in the deflected delivery-gas stream, while heavier particles pass through the separating-gas stream, on account of the particle velocity and mass inertia, and are collected in the lower region of the classifier. engineering! 16 (1982) No. 7/8, pages 640 to 648 has disclosed an elbow/countercurrent classifier according to the preamble of claim 1 which likewise serves for treating a bulk-material stream. In this reference source, the elbow/countercurrent classifier is described as a very efficient means for separating off splinters, dust, filaments or the like from plastics granules. You is therefore expressly referred to the mode of operation, described in this reference source, of said elbow/countercurrent classifier.
It is already specified in this reference source, in the description of a further riser tube/gravity classifier, that the velocity profile in the interior of the tube varies over the tube cross section, the air velocity dropping toward zero, in particular, in the vicinity of the wall. Fine particles which pass into the vicinity of the wall thus drop into the coarse material if they are not picked up by the air turbulence and not transported back into the interior of the tube. This disadvantage is not stated explicitly in the elbow/countercurrent classifier described subsequently in this reference source since, in this case, high particle acceleration occurs inside the provided opening duct of the bulk-material delivery conduit, as a result of which particles above a specific size pass through the classifying section located upstream of the outlet mouth and are separated off in the bottom collecting container and discharged. All the smaller particles and filaments and strips are slowed down without any difficulty in the classifying section and discharged by the deflected air flow. The known elbow classifier thus solves to a satisfactory degree the problem of classifying the elements to be separated off.
ADVANTAGES OF THE INVENTION
The o
REFERENCES:
patent: 3441131 (1969-04-01), Gebauer
patent: 4872973 (1989-10-01), Ikebuchi et al.
patent: 5201422 (1993-04-01), Ihara et al.
W. Krambrock: "Moglichkeiten zum Abtrennen von Splittern Staub und Faden aus Kunststoffgranulat". In: vt verfahrenstechik, 16, (1982), No. 7/8, pp. 640-648.
Nguyen Tuan N.
Terrell William E.
Zeppelin Schuettguttechnik GmbH
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