Rod cage classifier having improved separation sharpness
The rod basket classifier improves separation efficiency by using ventilation openings and guide plates to separate fine material from coarse material, reducing grinding passes and enhancing particle size distribution analysis.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- KHD HUMBOLDT WEDAG GMBH
- Filing Date
- 2025-11-26
- Publication Date
- 2026-06-04
AI Technical Summary
Existing rod basket classifiers face challenges in achieving high separation efficiency due to the carryover effect of fine material with coarse material, despite optimization measures.
The rod basket classifier is equipped with ventilation openings around the hopper circumference, connected to channels leading through the flow channel, which introduce transport air from below to separate coarse material from fine material by extending the fall path and using guide plates to direct falling particles away from vents, while channels are tapered to reduce resistance and equipped with shut-off flaps to manage airflow.
Enhances separation efficiency by effectively separating fine material from coarse material, reducing the number of grinding passes required and improving particle size distribution analysis.
Smart Images
Figure EP2025084255_04062026_PF_FP_ABST
Abstract
Description
[0001] KHD Humboldt Wedag GmbH EM2024012 November 26, 2025
[0002] H 24 / 008 PCT
[0003] Rod basket classifier with improved separation efficiency
[0004] The invention relates to a rod basket classifier for classifying granular material, comprising an outer housing which is divided into a first, upper part of the housing and a second, lower part of the housing, wherein the first, upper part of the housing has an outer annular chamber, a static rod basket arranged therein, and a dynamic rod basket driven to rotate within the static rod basket, wherein the dynamic rod basket is closed at the bottom with a closed bottom, and wherein an inner annular space, open at the bottom, is provided between the static rod basket and the dynamic rod basket, and the second, lower part of the housing has an outer flow channel connected to the outer annular chamber and a funnel, preferably conical, received therein, the upper edge of which projects up to the static classifier.so that the inner annular space is connected to the funnel via its lower opening, the funnel having a conduit to the outside.
[0005] The invention further relates to a circulating grinding system and a method using the rod basket classifier.
[0006] To separate granular material into fine and coarse fractions, it is known to disperse the material in conveying air and introduce it into a rod basket classifier. The rod basket classifier contains a rotating rod basket to which the conveying air containing the material is supplied tangentially. The rotating rod basket generates a circular flow in which the coarser particles of the material migrate outwards, while the finer particles flow through the spaces between the rod baskets along with the conveying air. [Inside KHD Humboldt Wedag GmbH EM2024012 26.11.2025]
[0007] H 24 / 008 PCT of the rod basket: The transport air is extracted, thereby removing the fines along with the extracted air from the rod basket classifier. The coarse particles that did not pass through the gaps of the rod basket fall into an annular channel in front of the basket and then into a hopper located below the bottom-sealed rod basket. The hopper leads to a conduit where the coarse material is collected.
[0008] Several methods are known to increase the separation efficiency of rod basket classifiers. One such method involves arranging a rotating rod basket inside a static rod basket. The rods of the static rod basket are either equipped with an airfoil profile or inclined to the vertical axis. The static rod basket slows down the coarser particles and causes a radial flow towards the rotating rod basket. This results in a sudden change in the flow direction from tangential to radial. During this deflection, some of the coarser particles fall out and collect in the annular gap between the static and dynamic rod baskets. While this increases the separation efficiency, it is also observed that the flow of coarser particles carries with it a gas stream containing dispersed fines.This carryover effect persists despite a multitude of optimization measures for separation efficiency in a rod basket classifier.
[0009] The object of the invention is therefore to provide a rod basket classifier in which the separation efficiency is also increased with regard to the fine material carried along with the coarse material.
[0010] The problem according to the invention is solved by a rod basket classifier with the features of claim 1. Further advantageous embodiments are specified in dependent claims 2 to 6. Claims 7 and 8 claim a recirculating grinding plant with such a rod basket classifier, and claims 9 and 10 claim a method for comminuting material using such a classifier. KHD Humboldt Wedag GmbH EM2024012 26.11.2025
[0011] H 24 / 008 PCT
[0012] According to the invention, the hopper in which the coarse material is collected is ventilated. For this purpose, ventilation openings are provided that correspond to corresponding channels leading through the flow channel, through which the transport air is introduced from below to the rod basket. Thus, it is provided that ventilation openings are distributed around the circumference of a wall of the hopper, each connected to a corresponding channel that leads through the outer flow channel to an outer wall of the second, lower part of the housing.
[0013] In an advantageous embodiment of the rod basket sifter, the ventilation openings can be elongated slots with a vertical orientation during the intended use of the rod basket sifter. This vertical orientation allows the coarse material falling downwards, which carries the fine material with it, to be separated from the fine material by the ventilation openings over a longer fall path.
[0014] Since the channels run through the flow channel, through which the transport air containing the suspended material is guided from below to the rod basket, an advantageous embodiment of the rod basket classifier may provide that the channels taper downwards and upwards during normal use. This tapering on both sides acts like a wedge at the sides of the channels towards the ventilation openings, giving the channel a favorable profile with low flow resistance. This shape results in the incoming transport air and the suspended material encountering less resistance. Furthermore, no material particles are deflected from the channel crossing the flow channel to the ventilation openings.
[0015] It may be provided that the ventilation openings have guide plates arranged like louvers, inclined downwards towards the inside of the funnel. These guide plates ensure that falling particles are directed away from the vents. KHD Humboldt Wedag GmbH EM2024012 26.11.2025
[0016] H 24 / 008 PCT
[0017] The material particles should not fall into the channel leading to the ventilation opening and thus gradually clog the channel.
[0018] Furthermore, the channels on the outer wall of the second, lower part of the housing may be equipped with shut-off flaps. These flaps allow some of the ventilation openings to be deactivated, thus reducing the amount of false air flowing into the rod basket classifier. This is dependent on the fine-tuning of the flow conditions within the rod basket classifier, which, in addition to the geometry itself, also depends on the rotational speed of the rod basket and the pressure differential generated by a compressor downstream of the rod basket classifier in the direction of fines flow for extracting the fines stream.
[0019] The location of the ventilation openings can also influence the separation efficiency. Since rod basket classifiers vary in height and are operated with different parameters, the ideal position depends on the operating and geometric parameters. For a wide range of geometries and operating parameters, it has proven advantageous to position the ventilation openings approximately 1 / 5 (20%) to 1 / 2 (50%) of the hopper wall height, from the tip where a pipe branches off to the hopper's edge, extending into the upper third of the hopper wall. Lower ventilation openings often result in coarse material being blown onto the hopper's surface, preventing the fines from being blown away from the coarse material.
[0020] The rod basket classifier presented here is suitable for use in a recirculating mill. For this purpose, a recirculating mill can have at least one comminution device and a rod basket classifier as described above, with the coarse material falling from the hopper line being connected to the at least one comminution device via a line. Due to the increased separation efficiency after just one pass, the number of revolutions of the material to be ground in the recirculating mill is reduced. In addition to the reduced number of revolutions, KHD Humboldt Wedag GmbH EM2024012 26.11.2025
[0021] In H 24 / 008 PCT, the particle size distribution also changes, which can be illustrated by plotting the particle sizes in an RRSB diagram (Rosin-Rammler-Sperling-Bennett diagram). An RRSB diagram is often used to graphically represent the particle size distribution of powdered materials, especially when there is a continuous distribution from fine to coarse particles. In this diagram, particle size is plotted against the cumulative mass fraction of the particle sizes on a logarithmic scale. The linear representation allows for precise analysis and comparison of the distribution based on the slope and shape of the graph.
[0022] Such a closed-loop grinding plant can also be configured with two comminution units. Specifically, the plant can be equipped with two comminution units: a high-pressure roller press and a ball mill. These closed-loop grinding plants are suitable, for example, for comminuting raw meal for the production of cement clinker or for comminuting cement clinker after it has left the plant in a coarse-grained state. For this purpose, the material being ground can be conveyed to the rod basket classifier after passing through the high-pressure roller press. The coarse material is directed from the hopper of the rod basket classifier to a ball mill, and the fine material, along with the classifying air, is separated from the interior of the dynamic rod basket.The fines from the rod basket classifier differ in particle size distribution from the ground material as it leaves the ball mill. To achieve a specific particle size distribution, the fractions from the rod basket classifier can be mixed with the fraction from the ball mill in predetermined ratios.
[0023] The invention is explained in more detail with reference to the following figures. They show:
[0024] Fig. 1 shows a side view from the outside of a rod basket classifier, shown here without the mounted motor for the rod basket, KHD Humboldt Wedag GmbH EM2024012 26.11.2025
[0025] H 24 / 008 PCT
[0026] Fig. 2 shows a top view of the open-topped rod basket sifter, so that the individual elements, some of which are shown as perforated, are visible.
[0027] Fig. 3 shows a section through the rod basket sifter from Figure 1 along the plane BB in Figure 1 ,
[0028] Fig. 4 shows a section through a detail in Figure 3 along the section line PP,
[0029] Fig. 5 shows a perpendicular section through the rod basket classifier in Figure 1 / Figure 3 along the plane AA,
[0030] Figure 6 shows a circulating milling system with a rod basket classifier according to the invention in a first embodiment,
[0031] Figure 7 shows a circulating grinding system with a rod basket classifier according to the invention in a second embodiment.
[0032] Figure 1 shows a side view of a rod basket classifier 100, depicted here without a mounted motor for the internal dynamic rod basket 106. The housing 101 of the rod basket classifier 100 consists of a first, upper part 102 and a second, lower part 103. The first, upper part 102 of the housing 101 has an outer annular chamber 104 and a static rod basket 105 arranged therein. Furthermore, the static rod basket 105 arranged therein has a dynamic rod basket 106, which is driven to rotate within the static rod basket 105. The dynamic rod basket 106 is closed at the bottom by a closed base 107. Between the static rod basket 105 and the dynamic rod basket 106, there is an inner annular space 108, which is open at the bottom. These details are explained in more detail in the following figures.A pipe 113 protrudes downwards from the rod basket classifier, through which separated coarse material exits the rod basket classifier 100. On the outer wall 117 of the rod basket classifier 100, closing flaps 122 are visible on the right side, which close channels 116 to an internal hopper. On the left side, KHD Humboldt Wedag GmbH EM2024012 26.11.2025.
[0033] H 24 / 008 PCT
[0034] However, the channels 116 are open in the outer wall 117. A section along the plane BB is shown in Figure 3.
[0035] Figure 2 shows a top view of the open-topped rod basket classifier 100, revealing the individual elements, some of which are shown as openwork. Through the open top of the housing 101, the dynamic rod basket 106, which rotates within the static rod basket 105, is visible. The dynamic rod basket 106 has a bottom 107 that closes it off at the bottom. Only the upper parts of the dynamic rod basket 106 and the bottom 107 are shown here to provide a view below the dynamic rod basket 106. The dynamic rod basket 106 is arranged within a static rod basket 105, which encloses the dynamic rod basket 106. The individual rods or flumes of the static rod basket 105 are curved to create a flow-optimized flow during operation of the rod basket classifier 100.The static rod basket 105 is arranged within an outer annular chamber 104, which is itself bounded externally by the housing 101. Transport air containing suspended material to be screened flows from below into the outer annular chamber 104 and flows tangentially towards the static rod basket 105. The transport air with the material to be screened is drawn radially through the rods or channels of the static rod basket 105 by the negative pressure inside the dynamic rod basket 106. This change in direction from tangential to radial causes an initial portion of the coarse material within the screened material to fall downwards into the hopper 110. Coarse material that still passes through the bars or floods of the static bar basket 105 will fall downwards at the latest in the annular space 108 between the static bar basket 105 and the dynamic bar basket 106, because the coarse material cannot pass through the rotating bar basket.The centrifugal force generated during a passage through the bars of the dynamic bar basket 196 prevents the heavier grains of the material being screened from passing through the bar basket, and they therefore fall into the annular space 108, while the transport air with KHD Humboldt Wedag GmbH EM2024012 26.11.2025.
[0036] H 24 / 008 PCT The fine material, still suspended within, passes through the bars of the rotating rod basket 106. Inside the dynamic rod basket 106, the transport air, along with the fine material, is drawn in by a suction blower. Coarse material falling into the hopper 110 exits the hopper 110 through the line 113. As it slides over the conical walls of the hopper 110, the coarse material is blown free of fine material by fresh air flowing in from the ventilation openings 115. The incoming fresh air suspends the blown-off fine material and flows upwards again through the suction of the suction blower to the dynamic rod basket classifier 106, where it passes through the bars of the dynamic classifier 106.
[0037] Figure 2 shows a plane AA that indicates a perpendicular section in the vertical direction through the stationary rod basket classifier 100. This section view is shown in Figure 5.
[0038] Figure 3 shows a section through the rod basket classifier from Figure 1 along plane BB in Figure 1. The section, which lies below the upper opening of the rod basket classifier, reveals the channels 116 that connect the ventilation openings 115 in the inner hopper 110 to the outer wall 101 of the rod basket classifier 100. The channels 116 are located in the annular chamber 104, through which the unseparated or unseparated material flows, dispersed in transport air. To better illustrate the channels, a section plane PP is shown in Figure 3, which is depicted in the following Figure 4 and runs perpendicularly through a vertical opening 115 in the wall 114 of the hopper 110.
[0039] Figure 4 shows a section through a detail in Figure 3 along section line PP. This section PP runs perpendicularly through a vertical ventilation opening 115 in the wall 114 of the hopper 110. The channel 116, which leads from the ventilation opening 115 to an outer wall 117 of the second, lower part 103 of the housing 101, is clearly visible. The ventilation openings 115 have guide plates 120 arranged like louvers, which are inclined downwards towards the inside 121 of the hopper 110. The purpose of these guide plates 120 is to direct coarse material falling downwards in the hopper 110, so that the material is carried away according to KHD Humboldt Wedag GmbH EM2024012 26.11.2025
[0040] H 24 / 008 PCT coarse material falling into the bottom of the hopper 110 does not clog or block the channel 116.
[0041] Figure 5 shows a vertical section through the rod basket sifter 100 in Figure 1 along the plane AA shown in Figure 3. The open static rod basket 105 is visible in the upper part 102, its rods arranged in a semicircle behind the plane of the paper. For better illustration of the details, the dynamic rod basket 106 is omitted from this sectional drawing. A preferably conical funnel 110 extends with its upper opening 111 to the static sifter basket 105, so that the inner annular space 108, formed between the static rod basket 105 and the dynamic rod basket 106 (not shown here), is connected to the funnel 110 via its lower opening 112. The ventilation openings 115 in the wall 114 of the funnel 110 are visible in this sectional drawing.In the section shown here, two channels 116 are located on the left and right sides of the rod basket classifier 100, connecting the ventilation openings 115 to the outer wall 117, allowing air to flow from the outside into the hopper 110. The air flows along the path indicated by arrows through the arrangement of guide plates 120 in the ventilation openings 115 and is drawn upwards by the suction of a suction fan to the annular space 108 between the static rod basket 105 and the dynamic rod basket 106. The incoming air picks up fines and separates the coarse material from any entrained fines.
[0042] Figure 6 shows a recirculating grinding plant 200 with a rod basket classifier 100 according to the invention in a first embodiment. The recirculating grinding plant 200 has at least one comminution device 201, here in this example a high-pressure roller press, and a rod basket classifier 100 described above. The coarse material falling from the line 113 of the hopper 110 is connected to the at least one comminution device 201 via a line 202. The line 202 consists of the downpipe from the rod basket classifier 100, a conveyor belt, KHD Humboldt Wedag GmbH EM2024012 26.11.2025
[0043] H 24 / 008 PCT, which leads from the downpipe to a bucket elevator, and from the bucket elevator, as well as the conveyor belt, the raw material is fed onto the conveyor belt. The raw material is fed onto the high-pressure roller press, which falls out underneath it and is deagglomerated in a static V-classifier. Coarse slag residues are conveyed back to the high-pressure roller press, while fines from the static V-classifier are pneumatically transported to the bar basket classifier 100. In this classifier, the fines from the static V-classifier are separated into a fines fraction and a coarses fraction. The coarses from the bar basket classifier 100, which fall from line 113 of the hopper 110, are conveyed via line 202 to at least one shredding device 201, where they are subjected to further shredding.
[0044] Figure 7 shows a circulating mill 300 with a rod basket classifier 100 according to the invention in a second embodiment. The circulating mill 300 comprises at least one comminution device 201 and 210, in this example a high-pressure roller press and a ball mill, and a rod basket classifier 100 as previously described. The coarse material falling from the line 113 of the hopper 110 is connected via a line 302 to the at least one comminution device 210, the ball mill. Raw material is fed onto the high-pressure roller press, which falls out from under the high-pressure roller press and is deagglomerated in a static V-classifier. Coarse chaff residues are conveyed back to the high-pressure roller press, while fines from the static V-classifier are pneumatically transported to the rod basket classifier 100. There, the fines from the static V-classifier are separated into a fines fraction and a coarses fraction.The coarse material from the rod basket classifier 100, which falls from the line 113 of the hopper 110, is conveyed via a line 202 to at least one shredding device 210, the ball mill, where it is subjected to further shredding. Fine material from the rod basket classifier and fine material from the ball mill can then be used to adjust a KHD Humboldt Wedag GmbH EM2024012 26.11.2025.
[0045] H 24 / 008 PCT can be mixed with predetermined particle size distributions or used separately.
[0046] KHD Humboldt Wedag GmbH EM2024012 November 26, 2025
[0047] H 24 / 008 PCT
[0048] 100 rod basket classifiers 114 wall
[0049] 101 Housing 115 Ventilation opening
[0050] 102 upper part (housing) 116 channel
[0051] 103 lower part (housing) 117 outer wall
[0052] 104 Ring chamber 120 Guide plate
[0053] 105 Rod basket, static 121 Inside
[0054] 106 Rod basket, dynamic 122 Closing flap
[0055] 107 soil 200 recirculating mill
[0056] 108 annular space 201 shredding device
[0057] 109 Flow channel 202 Conduit
[0058] 110 Funnel 210 Crushing device
[0059] 111 Opening edge 300 Circular grinding system
[0060] 112 Opening 302 Line
[0061] 113 Management
Claims
KHD Humboldt Wedag GmbH EM2024012 November 26, 2025 H 24 / 008 PCT Rod basket classifier with improved separation efficiency PATENT CLAIMS 1. Rod basket sifter (100) for sifting granular material, having - an outer housing (101) which is divided into a first, upper part (102) of the housing (101) and a second, lower part (103) of the housing (101), wherein - the first, upper part (102) of the housing (101) - an outer annular chamber (104), - a static rod cage (105) arranged therein and - has a dynamic rod cage (106) driven in rotation within the static rod cage (105), wherein - the dynamic rod basket (106) is closed at the bottom with a closed bottom (107), and wherein - between the static rod cage (105) and the dynamic rod cage (106) there is an inner annular space (108) which is open downwards, and - the second lower part (103) of the housing (101) - an outer flow channel (109) connected to the outer annular chamber (104), and KHD Humboldt Wedag GmbH EM2024012 26.1 1.2025 H 24 / 008 PCT - having a funnel (110) included therein, preferably conical, which extends with its upper opening edge (111) to the static viewing basket (105), so that the inner annular space (108) is connected with its lower opening (112) to the funnel (110), wherein - the funnel (110) has a conduit (113) to the outside, characterized in that ventilation openings (115) distributed around the circumference are provided in a wall (114) of the funnel (110), each of which is connected to a corresponding channel (116) which leads through the outer flow channel (109) to an outer wall (117) of the second, lower part (103) of the housing (101).
2. Rod basket classifier according to claim 1, characterized in that the ventilation openings (115) are elongated slots with a vertical orientation in the intended use of the rod basket classifier (100).
3. Rod basket classifier according to claim 1 or 2, characterized in that the channels (116) are tapered downwards and upwards in the intended use of the classifier (100). - 15 - KHD Humboldt Wedag GmbH EM2024012 26.1 1.2025 H 24 / 008 PCT 4. Rod basket classifier according to one of claims 1 to 3, characterized in that the ventilation openings (115) have guide plates (120) arranged in a louver-like manner, which are inclined downwards towards the inside (121) of the hopper (110).
5. Rod basket classifier according to one of claims 1 to 4, characterized in that the channels (116) on the outer wall (117) of the second, lower part (103) of the housing (101) have closing flaps (122).
6. Rod basket classifier according to one of claims 1 to 5, characterized in that the ventilation openings (115) have approximately 1 / 5 to 1 / 2 the height of the wall (114) of the hopper (110), wherein the ventilation openings (115) extend into the upper third of the wall (114) of the hopper (110).
7. Circulation grinding plant (200), comprising at least one comminution device (201 ) and a rod basket classifier (100) according to one of claims 1 to 6, wherein the coarse material falling from the line (113) of the hopper (110) is connected to a line (202, 302) to the at least one comminution device (201 , 210s). - 16 - KHD Humboldt Wedag GmbH EM2024012 26.1 1.2025 H 24 / 008 PCT 8. Circulating grinding plant according to claim 7. characterized in that the circulating grinding plant (300) contains two comminution devices (201 , 210), wherein a first comminution device (201 ) is a high-pressure roller press and a second comminution device (210) is a ball mill.
9. Method for comminuting grinding material in a circulating grinding plant (200, 300) according to one of claims 7 or 8, wherein fine material is separated from the interior of the dynamic rod basket (106) together with the classifying air.
10. Method according to claim 9, wherein coarse material is conveyed from the line (113) of the hopper (110) to the at least one comminution plant (200, 210).
11. Method for increasing the separation efficiency of a classifier for classifying granular material, comprising - an outer housing (101) which is divided into a first, upper part (102) of the housing (101) and a second, lower part (103) of the housing (101), wherein - the first, upper part (102) of the housing (101) - an outer annular chamber (104), - a static rod cage (105) arranged therein and - 17 - KHD Humboldt Wedag GmbH EM2024012 26.1 1.2025 H 24 / 008 PCT - has a dynamic rod cage (106) driven in rotation within the static rod cage (105), wherein - the dynamic rod basket (106) is closed at the bottom with a closed bottom (107), and wherein - between the static rod cage (105) and the dynamic rod cage (106) there is an inner annular space (108) which is open downwards, and - the second lower part (103) of the housing (101) - an outer flow channel (109) connected to the outer annular chamber (104), and - having a funnel (110) included therein, preferably conical, which extends with its upper opening edge (111) to the static viewing basket (105), so that the inner annular space (108) is connected with its lower opening (112) to the funnel (110), wherein - the funnel (110) has a conduit (113) to the outside, characterized by Ventilation openings (115) distributed around the circumference are provided in a wall (114) of the funnel (110), each of which is connected to a corresponding channel (116) that leads through the outer flow channel (109) to an outer wall (117) of the second, lower part (103) of the housing (101).