Classifying – separating – and assorting solids – Fluid suspension – Liquid
Reexamination Certificate
2002-10-01
2004-12-07
Walsh, Donald P. (Department: 3653)
Classifying, separating, and assorting solids
Fluid suspension
Liquid
C209S208000, C209S724000, C209S725000
Reexamination Certificate
active
06827221
ABSTRACT:
The invention relates to a mill classifier, particularly a roller mill classifier according to the preamble of claim
1
.
Roller mill classifiers, which can be arranged in integrated manner in or mounted on a roller and bowl mill or in a roller mill, e.g. in an air-swept mill, can be constructed as static or dynamic sifters or classifiers. Combinations of a static and a dynamic classifier, which is then referred to as a high effect classifier, are also known.
A high effect classifier is described in ZKG, vol. 46, 1993, No. 8, pp 444 to 550, FIG. 7. The classifier has a cylindrical strip rotor and a concentrically arranged guide flap or vane ring. The aim is to produce a very effective tangential flow between the static distributor and the strip rotor, so that the coarse particles cannot reach the rotor. The disadvantages are an increased pressure loss and an increasing wear to the guide vanes, particularly with high particle concentrations.
EP 204 412 B1 discloses a mill classifier, which has two superimposed guide vane rings. The guide vanes are adjustably arranged about vertical spindles, the guide vanes of the guide vane rings having independently mounted spindles. Between the guide vane rings is provided a stationary ring and the adjusting devices are located at opposite ends of the guide vanes.
FR 2 642 994 A1 discloses a classifier with a strip rotor and a concentrically arranged guide vane ring. In order to improve classification the guide vanes of the guide vane ring are adjustable about a vertical axis. The rotor strips are constructed in such a way that in each case channels are formed with a cross-section widening from the outside to the inside, so that the centrifugal and resistance forces acting on the particles of a predeterminable size, are in equilibrium over virtually the entire length of the channels. Thus, the equilibrium conditions are obtained via the profile of the rotor strips, the rotor speed and the setting of the guide vanes for different separating diameters.
The cylindrical strip or rod basket rotor used in the afore-mentioned mill classifiers generally has a number of strips, which is at least twice as high as in so-called standard classifiers, which leads to relatively high manufacturing costs. The suspension and mounting of a rod basket rotor also differs from the rotors of the standard classifier and contributes to higher manufacturing and assembly costs.
A known standard classifier is the LOESCHE centrifugal/basket classifier of the LKS design (ZKG, vol. 46, 1993, No. 8, p 446, FIG. 5). This dynamic classifier is constructed as a biconical or double cone strip rotor and has a double cone rotor with screwed on classifying strips. The sloping rotor strips correspond to the incident flow from below and lead to a weak deflection of the grinding material-fluid flow. In conjunction with a twisting flow caused by the setting of the blades of a blade ring of the mill and a conically upwardly widening classifier casing, a radial flow occurs at the strip rotor and increases from bottom to top and leading on the conically upwardly widening strip rotor to different centrifugal forces and to a relatively uniform classifying over the entire strip length.
DE 44 23 815 C2 discloses a high effect classifier, in which a static classifying precedes a double cone rotor of a LOESCHE centrifugal/basket classifier. By means of at least two axially superimposed and adjustably arranged guide vane rings and a directional deflection of the grinding material-fluid flow, part of the coarse material is separated, before a dynamic reclassifying takes place through the following conical strip rotor. The classifier has an improved separation efficiency and a lower energy consumption compared with standard classifiers, but does not in all cases meet the constantly increasing demands on efficiency and low manufacturing and maintenance costs.
The object of the invention is to provide a mill classifier, particularly a roller mill classifier, which in the case of particularly simple construction has very low production costs and simultaneously permits a high flexibility and optimization of sifting or classifying processes.
According to the invention the object is achieved by the features of claim
1
. Appropriate and advantageous developments appear in the specific description relative to the drawings and in the sub claims.
A fundamental idea of the invention is to retain the advantages of a strip rotor of a LOESCHE centrifugal/basket classifier and to achieve a purely dynamic classifying with the aid of at least one guide vane ring, the guide vanes and the rotor strips being so constructed and mutually oriented that the grinding material particles are not forced onto an orbit outside the strip rotor and are instead delivered into the strip rotor.
According to the invention the guide vanes are shaped and positioned in such a way that there is no so-called cyclone flow, but instead and without an upstream static classifying stage, a grinding material-fluid mixture is directly dynamically classified.
According to the invention a roller mill classifier with a strip rotor of a fundamentally known design and a guide vane ring arranged concentrically around the strip rotor is provided with flow-optimized guide vanes, which are adjustable about a vertical rotation axis and force a grinding material-fluid flow rising from the mill to a tangential to radial incident flow of the rotor strips of the strip rotor.
Preferably use is made of rotor strips, as are known in connection with LKS classifiers, but at least in the vicinity of the guide vanes are arranged vertically and therefore parallel to the guide vanes.
It is appropriate with respect to the production costs and efficient classifying to use as the strip rotor a double cone rotor, particularly of a LKS design LOESCHE centrifugal/basket classifier and to retool or reset the same in such a way that the known rotor strips are retained, but are perpendicular and no longer slope to a cylindrical rotor area. As the rotor strips have a radial dimensioning as with a LKS classifier, it is possible to significantly reduce the number of rotor strips compared with the cylindrical rod basket rotors of the high effect classifier. It has been found that the number of strips can be approximately one third of that of a rod basket classifier and can be max 50%.
A separation-efficient classifying without an upstream static classifying can be achieved by at least one guide vane ring with flow optimized guide vanes, which have a rounded leading edge and at least one guide plate and which are set with respect to the strip rotor in such a way that an imaginary extension of the guide plates does not extend past the strip rotor and instead leads at least tangentially to the outer edges of the rotor strips or radially into the rotor centre.
It is particularly advantageous to have guide vanes with a rounded leading edge and at least one guide plate located thereon in such a way that roughly parallel or widening flow channels are formed between in each case two guide vanes and the incoming and outgoing flows are approximately the same.
In conjuncation with the rounded leading edge there is a parallel flow without constriction during the outgoing flow and as a result of a particularly advantageous streamlined construction of the guide vanes there is an expanding outgoing flow with a diffuser effect, which is linked with a recovery of pressure energy and therefore a reduction of the through-flow resistance of the classifier. However, in the case of planar guide vanes a flow channel with a nozzle effect is formed between two guide vanes.
A cost-effective manufacture, assembly and simple adjustment of the flow-optimized guide vanes can be achieved in that the rounded leading edge is constituted by a cylindrical or tubular incident flow body, e.g. an incident flow tube, on which the guide plate is arranged, e.g. welded tangentially. It is also possible to indirectly fasten the guide plate, e.g. by means of an additional fastening plate to the incident flow tube. Wher
Brundiek Horst
Ruhkamp Winfried
D'Alessandro Ronald A.
Hoffman, Warnick & D'Alessandro LLC
Joerger Kaitlin
Loesche GmbH
Walsh Donald P.
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