PNEUMATICALLY LINKED MULTIVIEWER

Description

[0001] The invention relates to a classifier for classifying granular material into at least one fraction of fine material and one fraction of coarse material, comprising a housing in which a stepped cascade permeable to screening gas is installed at an angle deviating from the horizontal, at least one inlet channel into the housing for screening gas, and at least one outlet channel from the housing for screening gas loaded with fine material, wherein opposite the stepped cascade and separated by a screening zone, screening flumes are arranged one above the other in a louver-like manner, and wherein above the screening zone on the top of the housing a screening material inlet opening and below the screening zone on the underside of the housing a discharge opening for the coarse material are arranged.

[0002] For separating fines from the material being separated, it is known to allow the material to fall in a closed chamber, through which air flows transversely, over a stepped cascade of baffles, thereby blowing the fine particles out with the air. The blown-out fines are then discharged from the chamber via an outflow duct along with the air, and in a further device, the fines are separated from the air stream. These classifiers described here are generally referred to as V-classifiers due to their external design.

[0003] The efficiency of V-classifiers is determined by their geometry. The cascades must not be too shallow to ensure sufficient flow of the material being separated, nor too steep, so that the classifying air has enough time to blow out the fines. A V-classifier should also not be arbitrarily wide, as very wide V-classifiers, wider than the pile cone that forms at a corresponding throughput, could lead to distribution problems across the width of the classifier. Therefore, there are geometric limits to the ideal shape of a V-classifier.

[0004] To increase the throughput of a material screening plant, it is possible to arrange many individual screeners side by side. These screener banks operate independently and in parallel. The total screening capacity of the screener bank configured in this way is equal to the sum of the screening capacities of the individual screeners. To supply the individual screeners with screening air, it is necessary to connect them to a central screening air supply. This presents challenges for pneumatic control, similar to those encountered on a much smaller scale in air conditioning systems. The screening airflow differs between the individual screeners because their distance from the central compressor varies. A screener located closer to the compressor reduces the pressure in the remaining line, so that the screeners located further away operate with a lower screening air pressure.This results in differences in separation efficiency, but also in the particle size distribution of the fines, between the various individual classifiers. While it is known to regulate the air supply to individual classifiers using airflow controllers, controlling multiple classifiers is no longer straightforward. This is because control oscillations can build up in the ductwork from the compressor to the individual classifiers. These oscillations can arise from dynamic air pressure fluctuations in the air flow rate. In addition to the actual control oscillation, which is generated by the timer between the actuator and the control element, an air pressure oscillation, which builds up within the system itself and can affect the grinding cycle, is superimposed on the control system.

[0005] European patent application EP 1 090 685 A1 discloses a compact recirculating milling system in which two cascades are located opposite each other within the same housing. These cascades are not decoupled and tend to operate with a greater pressure drop than the second, resulting in different separation efficiencies and different classifying results. A classifier according to the preamble of claim 1 is known from this document.

[0006] Chinese utility model CN ​​202 460 996 U depicts parallel-operating single classifiers that function with different interconnection configurations. Both serially connected and parallel-operated classifiers are shown with respect to the classifying air.

[0007] German patent DE 10 2015 013 892 B3 discloses a double classifier in which two successive cascades, each forming its own viewing zone, are arranged in a common housing. The two cascades are connected in series with respect to the viewing air.

[0008] European patent application EP 1 084 769 A1 describes a classifier combination consisting of a cascade classifier and a rod basket classifier in a common housing. The two classifiers are connected in series with respect to the classifying air.

[0009] International patent application WO 2013 / 079416 A1 also presents a classifier combination consisting of a cascade classifier and a rod basket classifier in a common housing. The two classifiers are connected in series with respect to the classifying air.

[0010] US patent 2,294,290 A describes a battery of parallel-connected classifiers supplied with classifying air via a common supply line. In this classifier battery, the last classifier operates at a significantly lower pressure than the classifiers located at the front of the classifying air supply line. The object of the invention is therefore to provide a scalable classifier that is not tall, thus saving lifting effort, and that does not tend to vibrate, so that it produces a uniform fines product with a consistent particle size distribution from the material being separated.

[0011] The problem according to the invention is solved by pneumatically connecting at least two opposing individual classifiers via a common pressure equalization chamber, through which the classifying gas flows into the respective inlet channels of the individual classifier. Further advantageous embodiments are specified in the dependent claims to claim 1.

[0012] According to the invention, a pressure equalization chamber is provided between more than one individual classifier, through which the more than one classifier is interconnected. The pressure equalization chamber eliminates the need for individual airflow control because it ensures that each classifier is supplied with the same air pressure. The common, central pressure equalization chamber is geometrically identical to each classifier, preventing any air pressure fluctuations that may occur due to differing airflow paths between the individual classifiers. This design allows a single large classifier to be replaced by a multiple arrangement of interconnected, smaller classifiers, as described in the invention.

[0013] In a preferred embodiment of the classifier according to the invention, the classifying gas resistance, which describes the pressure drop of the classifying gas from the inlet channel to the outlet channel at a given classifying gas flow rate, is approximately equal in at least two individual classifiers. The classifying gas resistance is determined by the cross-sectional area through which the classifying gas can flow in the respective individual classifier, the length of the air path that the classifying gas must travel within the individual classifier, and the airflow. The airflow describes whether the classifying gas is deflected multiple times or whether it flows in an ideal cylindrical tube. The effects of the geometric shape of a device on its flow resistance are well known to those skilled in the art, although predictability is not trivial.By comparing the air resistance between the different individual classifiers, the tendency towards control oscillations and the tendency towards air pressure oscillations in the supply line with classifying air is reduced, and the classifying efficiency becomes more uniform.

[0014] In a preferred embodiment of the invention, the more than one individual classifier is arranged as mirror images of each other, so that they are opposite each other and exhibit the same reaction to an inflow of classifying air. It is advantageous if the more than one individual classifier is always arranged in pairs as mirror images of each other. It is irrelevant whether the individual classifiers themselves exhibit mirror symmetry or are not mirror-symmetrical, meaning they do not have a plane of symmetry. The pressure equalization chamber of the classifier according to the invention can be constructed differently. It has proven advantageous if the pressure equalization chamber is directly connected to the classifying air inlet openings of the more than one individual classifier. It is possible that material being separated may also enter the pressure equalization chamber. This can occur due to unintended malfunctions during operation, deviations from ideal behavior, or a brief overload of an individual classifier.In order to be able to discharge the material being separated from the pressure equalization chamber, it is provided that in a preferred embodiment of the classifier the pressure equalization chamber has its own discharge opening for the material being separated.

[0015] In a further embodiment of the classifier according to the invention, the at least two individual classifiers can have, in addition to a discharge opening for fines, a further discharge opening for a medium fraction. The composition of the fines can be controlled quite precisely by the discharge of the medium fraction.

[0016] To ensure that the pressure equalization chamber distributes the pressure evenly across the multiple individual classifiers, it is connected to the inlet channels of at least two individual classifiers via a perforated or grille wall. The perforated or grille wall exhibits low airflow resistance. During equalization, the airflow resistance of an individual classifier acts as a passive control element, providing a small but noticeable equalization of the airflow. This ensures that the pressure in the pressure equalization chamber results in a virtually identical airflow across the multiple individual classifiers.

[0017] To ensure a uniform flow to more than one individual classifier, a preferred embodiment of the classifier may provide that the classifying gas, which flows via the pressure equalization chamber into the inlet channels of the at least two individual classifiers, flows into the pressure equalization chamber exactly in the center between the at least two individual classifiers. This geometric center results in a lower tendency for air pressure fluctuations, which have different effects on the different individual classifiers.

[0018] In a first specific embodiment of the invention, it is provided that pairs of opposing classifiers are arranged as a classifier battery, which are positioned one behind the other in pairs and connected to each other via the same pressure equalization chamber. To further divide the separated fines, the outflow channel from the housing of each individual classifier for fines can be connected to a separate rod basket classifier assigned to that individual classifier, or the outflow channels from the housing of more than one individual classifier for fines can be connected in a common rod basket classifier.

[0019] The invention is explained in more detail with reference to the following figures. They show: Fig. 1 a cutaway view of a V-classifier from the prior art, Fig. 2 a sectional view of a classifier according to the invention, Fig. 3 the classifier from Figure 2with additional rod basket classifiers, Fig. 4 an embodiment of the classifier according to the invention with a battery arrangement, Fig. 5 a top view of the classifier according to Figure 2 with section line shown, Fig. 6 a top view of a classifier according to the invention in a cross arrangement, Fig. 7 a top view of a classifier according to the invention in a star arrangement.

[0020] In Figure 1 is a vertical section through a V-visor 1For classifying granular material into at least one fraction of fines and one fraction of coarses, a V-classifier from the state of the art is shown. This known V-classifier has a housing G in which a stepped cascade 8, permeable to screening gas, is installed at an angle α to the horizontal. In the drawing, to the right of the stepped cascade 8, there is an inlet channel 3 through which screening gas can flow into the housing G. Granular material to be classified falls onto the stepped cascade via a screening opening 2 located above the screening zone SZ on the top of the housing G, where it trickles over the cascades and is thereby permeated by the screening gas flowing in laterally from the right. The screening gas flowing into the V-screener 1, namely air or hot exhaust gas, leaves the housing G via at least one outflow channel 5a, 5b, wherein the screening gas is loaded with fines which are themselves suspended in the screening gas.Opposite the stair-step cascade 8 and separated by a viewing zone SZ, the superimposed, louvered viewing channels 7 direct the viewing flow in a vertical direction, where the material to be viewed is separated into fractions of different particle sizes by gravity and the upflowing viewing gas. The fine material suspended in the viewing gas exits the V-classifier 1 via the discharge channels 5a and 5b. The coarse material, which falls downwards in the viewing gas within the viewing zone, falls into a coarse material discharge opening 4 located below the viewing zone SZ on the underside of the housing G, and exits to the outside below the V-classifier. To scale the performance of classifiers, the prior art provides for operating several classifiers and supplying the inlet channels 3 of the different V-classifiers with viewing gas via a Y-line 6 as a supply line, or generally via a line with branches.This can lead to problems in maintaining an optimal operating condition for each individual V-classifier if the sight gas pressure at the individual V-classifiers in the supply line is already slightly different.

[0021] In Figure 2 is a cross-sectional drawing along the in Figure 5The section line shown is through a classifier 100 according to the invention. According to the present invention, at least two opposing individual classifiers 100', 100" are pneumatically connected to each other via a common pressure equalization chamber (PAC), through which the classifying gas flows into the respective inlet channels 103', 103" of the at least two individual classifiers 100', 100". In the exemplary embodiment shown here, two individual classifiers 100' and 100", both of which are components of the classifier 100, are connected to each other via the pressure equalization chamber (PAC), with the entire opening of the grid wall 109, 109' in the inlet channels extending freely to the pressure equalization chamber. This ensures that the free cross-section of the inlet channels 103, 103' is not reduced by the cross-section of a supply line.This has the advantage that pressure fluctuations cannot build up, allowing the individual 100' and 100" classifiers to operate synchronously. The pressure equalization chamber located between the at least two classifiers is bounded by a roof D, a bottom B, and a rear surface R (. Figure 4) and a front wall not shown here by the section line. An inlet channel 103 leads into the pressure equalization chamber and is arranged as centrally as possible between the individual classifiers 100' and 100". The individual classifiers 100' and 100" are constructed similarly to the V-classifier from the prior art. These classify coarse material into one fraction of fine material and one fraction of coarse material. Both individual classifiers 100', 100" have a continuous housing G in which a stepped cascade 108, 108', permeable to inspection gas, is installed at an angle α to the horizontal. In the drawing, an inlet channel 103 is located between the two stepped cascades 108 and 108', through which inspection gas can flow into the pressure equalization chamber DAK.Granular material to be screened falls through a screening opening 102, 102" located above the respective screening zone SZ, SZ' of each individual screener 100', 102" on the top of the housing G onto the respective stepped cascade 108, 108', where it trickles over the cascades and is thereby permeated by the centrally flowing screening gas. The screening gas flowing into the respective individual screener, namely air or hot exhaust gas, leaves the housing G via at least one outlet channel 105a, 105a', 105b and 105b', the screening gas being laden with fines which are themselves suspended in the screening gas. The sighting streams 107, 107' opposite each stair cascade 108, 108' and separated by a sighting zone SZ, SZ', are arranged one above the other in a louver-like manner and direct the sighting stream in a vertical direction, where the material being sighted is separated into fractions of different grain sizes by gravity and the upflowing sighting gas.The fine material suspended in the screening gas exits the respective individual classifier 100', 100" via the discharge channels 105a, 105a' and 105b, 105b'. The coarse material falling downwards in the screening gas within the screening zone, on the other hand, falls into a screening discharge opening 104, 104' located below the screening zone SZ, SZ' on the underside of the housing G, for the coarse material to the outside, below the respective individual classifier 100', 100".

[0022] In Figure 3An extension of the classifier 100 is shown, in which a rod basket classifier 200, 200' is mounted on each of the outflow channels 105a, 105a' to further separate the fines suspended in the classifying gas. The size relationships shown here between the individual classifiers 100', 100" and the rod basket classifiers 200, 200' are not to scale. The diagram primarily illustrates the interconnection. It is possible that each outflow channel 105a, 105a' has its own dedicated rod basket classifier. Alternatively, it is also possible that the outflow channels 105a and 105a' connect and direct the classifying gas, along with the suspended fines, into a common rod basket classifier.

[0023] A particular embodiment of the classifier according to the invention is in Figure 4This is shown as classifier 300. In this classifier, three pairs of individual classifiers are arranged in a battery-like configuration such that a central pressure equalization chamber DAK supplies the six individual classifiers with classifying gas. The pressure equalization chamber DAK is delimited by a bottom B, a roof D, a rear wall R, and a front wall (not shown here). The coarse material falling out of the individual classifiers is transported via conveyor belts 150 and 150 to be returned to a classifying or grinding circuit.

[0024] In Figure 5 is the sifter from Figure 2shown in a top view. In this embodiment of the invention, the pressure equalization chamber (DAK) is comparatively large in volume compared to the volume of the individual classifiers, thereby preventing pressure fluctuations between the two individual classifiers. The large volume of the pressure equalization chamber (DAK) also makes it possible to pneumatically couple more than two individual classifiers (100', 100") via a common pressure equalization chamber (DAK). Figure 6 Two pairs of individual classifiers 100', 100", 100‴, 100ʺʺ are pneumatically coupled via a cross arrangement and a common pressure equalization chamber to form a classifier 400. This variant can be further expanded, so that, as in Figure 7 As shown, even 8 individual classifiers are coupled together in a star-shaped arrangement to form a classifier 500. REFERENCE MARK LIST 1 V-visor 103" Inflow channel 2 Visible material entry opening 104 Visible material discharge opening 3 Inflow channel 104' Visible material discharge opening 4 Discharge opening 104" Visible material discharge opening 5a Outflow channel 105a Outflow channel 5b Outflow channel 105a' Outflow channel 6 Y-cable 105a" Outflow channel 7 Visibility flood 105a"' Outflow channel 8 Staircase cascade 105b Outflow channel 9 Lattice wall 105b' Outflow channel 105b" Outflow channel 100 Sighter 105b"' Outflow channel 100' Single viewer 107 Visibility floods 100" Single viewer 107' Visibility floods 102 Visible material entry opening 108 Staircase cascade 102' Visible material entry opening 108' Staircase cascade 102" Visible material entry opening 109 Lattice wall 102"' Visible material entry opening 109' Lattice wall 103 Inflow channel 150 conveyor belt 103' Inflow channel 150' conveyor belt 200 rod basket sifter D Roof 200' rod basket sifter R back panel 300 Sighter G Housing 400 Sighter SZ field of vision 500 Sighter DAK Pressure equalization chamber B Floor

Claims

1. Separator (100, 300, 400, 500) for separating granular material to be separated into at least one fraction of fine material and into one fraction of coarse material, having - a housing (G) in which a stepped cascade (108, 108') which is permeable to separating gas is installed at an angle ( ) deviating from the horizontal; - at least one inflow duct (103) into the housing (G) for separating gas; and - at least one outflow duct (105a, 105a', 105b, 105b') out of the housing (G) for separating gas charged with fine material; wherein separating slats (107, 107') which are disposed on top of one another in the manner of Venetian blinds are disposed opposite the stepped cascade (108, 108') and separated by a separating zone (SZ); and wherein a material inlet opening (102, 102', 102", 102‴) is disposed above the separating zone (SZ) on the upper side of the housing (G); and a material discharge opening (104, 104') for the coarse material is disposed below the separating zone (SZ) on the lower side of the housing (G), wherein at least two mutually opposite individual separators (100', 100", 100‴, 100ʺʺ) are pneumatically interconnected by a common pressure equalization chamber (DAK) by way of which the separating gas flows into the respective inflow ducts (103', 103") of the at least two individual separators (100', 100", 100''', 100ʺʺ), characterized in that the pressure equalization chamber (DAK) is delimited by a roof (D,) a base (B) and a rear face (R), as well as by a front wall and wherein the pressure equalization chamber (DAK) is connected to the inflow ducts (103) of the at least two individual separators (100', 100", 100‴, 100ʺʺ) by way of a perforated panel wall or mesh wall (109, 109').

2. Separator according to Claim 1, characterized in that the separating gas resistances of the at least two individual separators (100', 100", 100‴, 100ʺʺ), the former defining the pressure drop of the separating gas from the inflow duct (103, 103') to the outflow duct (105a, 105a', 105a", 105a"', 105b, 105b', 105b", 105b‴) at a predefined separating gas flow in an individual separator (100', 100", 100''', 100ʺʺ), are approximately identical.

3. Separator according to Claim 1, characterized in that the at least two individual separators (100', 100", 100‴, 100ʺʺ) are constructed so as to be mirror-inverted and, with the exception of the mirror-inverted construction, are of identical construction.

4. Separator according to one of Claims 1 to 3, characterized in that the pressure equalization chamber (DAK) has a dedicated material discharge opening material discharge opening (104') .

5. Separator according to one of Claims 1 to 4, characterized in that the at least two individual separators (100', 100", 100‴, 100ʺʺ), next to an outflow duct (105a, 105a') for separating gas with fine material, have a further outflow duct (105b, 105b') for a medium material fraction.

6. Separator according to one of Claims 1 to 5, characterized in that the separating gas, which by way of the pressure equalization chamber (DAK) flows into the inflow ducts (103, 103') of the at least two individual separators (100', 100", 100‴, 100‴), flows into the pressure equalization chamber (DAK) so as to be exactly centric between the at least two individual separators (100', 100", 100‴, 100‴).

7. Separator according to one of Claims 1 to 6, characterized in that pairs of mutually opposite individual separators (100', 100", 100‴, 100‴) are constructed as a bank of separators which lie behind one another in pairs and are interconnected by the same pressure equalization chamber (DAK).

8. Separator according to one of Claims 1 to 6, characterized in that pairs of mutually opposite separators are disposed in a circle, wherein the different pairs of individual separators (100', 100", 100‴, 100‴) are disposed in a cruciform or radial geometry.

9. Separator according to one of Claims 1 to 8, characterized in that the outflow ducts (105a, 105a') of the at least two individual separators (100', 100", 100‴, 100‴) for separating gas charged with fine material are in each case connected to one rod-cage separator (200) or to a common rod-cage separator.