EP0758931A1

EP0758931A1 - Reversing counterflow separator

Info

Publication number: EP0758931A1
Application number: EP95916577A
Authority: EP
Inventors: Wolfgang Krambrock
Original assignee: Zeppelin Schuttguttechnik GmbH
Current assignee: Zeppelin Systems GmbH
Priority date: 1994-05-13
Filing date: 1995-04-26
Publication date: 1997-02-26
Anticipated expiration: 2015-04-26
Also published as: DE59501453D1; EP0758931B1; DE4416757A1; US5788083A; WO1995031294A1; DE4416757C2

Abstract

The proposal is for a reversing counterflow separator (1) by means of which a pneumaticlaly fed stream of loose material can be separated into coarse (48) and fine material (49). In order to increase the separating efficiency of the separator there is, especially in the region of the acceleration path (21, 22) and the separation path (23) continuing below it, a wall contour (50) increasing the turbulence of the gas flows. This increases the air speed near the wall and thus produces a constant air speed over the cross-section.

Description

"Deflection-counterflow classifier"

The invention relates to a Uirtlenk countercurrent classifier according to the preamble of claim 1.

State of the art;

So-called classifiers are used for the dry classification of fine-grained solids. The distinguishing feature is the final falling speed of the grains in the air. In particular, such classifiers can also be used to clean a bulk material mixture which is essentially in granular form and contains particles of different sizes. Due to different manufacturing processes, bulk goods can have very different distribution spectra. There are plastics in the form of granules, which are mixed with abrasion or dust particles. If the size of the granulate particles is of the order of magnitude of approx. 2 to 5 mm for the diameter or the length of the granulate, the dust particles, on the other hand, have a size of, for. B. 50 microns. In the case of plastic granules, there are occasionally larger particles, which are also called angel hair or bird nests, which are disc-shaped, ball-shaped or spherical can and have a diameter of about 2 cm to 10 cm. Such substances occur particularly with pneumatic conveying. The granulate required by the pipeline rubs up along the pipe, heats up and forms adhering threads or foils that tear off or come off again and again.

A known filter for the treatment of such substances is described in DE 42 35 260 AI, stating further prior art.

For the treatment of such bulk goods, a so-called deflection counterflow sifter has become known from DE-OS 1 905 106, in which the bulk material to be treated is fed to a deflection sifter via a conveying gas flow. Here, in particular, the bulk material conveyed downwards in the conveying gas flow in the deflection sifter is detected by an oppositely directed separating gas flow, which deflects the conveying gas flow upwards and entrains the lighter, smaller and in particular dusty particles in the deflected conveying gas flow, while heavier particles due to the particle speed and inertia Penetrate the separation gas flow and be collected in the lower area of the classifier.

From the literature: Special print from vt

"Process engineering" 16 (1982) No. 7/8, pages 640 to 648, a diverting countercurrent sifter has become known, which also serves to treat a bulk material flow. The deflection counterflow classifier is described as a very efficient device for separating splinters, dust, threads or the like from plastic granules. Reference is hereby expressly made to the mode of operation of this deflection countercurrent sifter described in this reference. Already in this literature reference it is stated in the description of a further ascending pipe gravity classifier that the speed profile in the inside of the pipe varies over the pipe cross section, the air speed dropping towards zero in particular towards the wall. Fine particles that come close to the wall fall into the coarse material if they are not caught by the air turbulence and transported back into the pipe interior. This disadvantage is explicitly not mentioned in the deflection-countercurrent classifier described below in this reference, since in this case high particle acceleration occurs within the intended outlet channel of the bulk material conveying line, as a result of which particles above a certain size penetrate the line of sight in front of the outlet opening and in lower collecting container are separated and discharged. All smaller particles, as well as threads and strips are easily braked in the line of sight and carried away by the deflected air flow. The known deflecting sifter therefore solves the problem of sighting the parts to be separated to a satisfactory extent.

Advantages of the invention;

The invention has for its object to improve the state of the art known from the literature "process engineering" ... that an even more efficient separation between larger particles and in particular plastic granules and the associated impurities such as splinters, dust, threads or the like is possible.

This object is achieved on the basis of a diverting countercurrent classifier according to the preamble of claim 1 by the characterizing features of claim 1. Advantageous further developments and improvements of the counterflow classifier according to the main claim are specified in the subclaims.

The invention is based on the basic idea that a sifting, ie a separation of different components, is only possible to a sufficient extent if all areas of a bulk material flow can be detected. It is known from the above-mentioned reference "process engineering" that the air speed of a flow in a conveyor pipe towards the wall drops towards zero. However, this technical effect is disregarded in a diverting countercurrent sifter insofar as the bulk material feed line penetrating into the sifter chamber from above is introduced concentrically, ie in the middle, so that the falling bulk material flow does not get into the wall area of the sifter anyway , because it is previously captured and treated by the rising separation gas stream. However, such an approach does not take into account that the bulk material flow is also subjected to a velocity profile inside the bulk material conveying line, which prevents the desired acceleration of the particles, at least in the respective wall area. The central tube used to form an annular acceleration channel in the bulk material conveying line results in a radially inner and a radially outer cylinder jacket surface, between which the described speed profile is established. Likewise, the central tube, which continues downward through the classifier, forms a desired ring cross section for the targeted supply of the upward separating gas stream to the mouth region of the bulk material conveying line. This ring channel for the separating gas flow also forms a radially inner and a radially outer cylinder jacket surface with a corresponding circumferential speed profile. According to the invention, a surface structure of the cylinder jacket surfaces is now chosen, in particular on the radially inner cylinder jacket surface both in the annular channel acceleration region of the bulk material conveying line and preferably in the annular flow channel of the separating gas flow, which should prevent the air speed towards the wall from dropping to zero to the previous extent. In other words, it should

Speed profile of the air speed within the specified ring channels are designed so that no dead zones form in the wall area of the respective ring channels, in which the granules can fall through. This is achieved, for example, in the prior art described in the reference "process engineering" by means of a zigzag-shaped sifter, i. H. the particles not caught in the wall area by the air flow of the separating gas flow are always directed back into the gas flow.

For this purpose, the present invention pursues another way of achieving this goal, in that the surface structure is formed in such a way that increased turbulence forms in the wall area, which leads to a velocity profile of the air flows that is as rectangular as possible. The zigzag shape of the air classifier itself, which is specified in the "Process engineering" reference, is applied, for example, as a surface structure to the cylinder jacket surfaces at a suitable point in order to lead to increased air turbulence, in particular in the wall area.

In this way, all larger particles in the bulk material conveying line are also accelerated in the wall area, so that they are able to penetrate the separation gas stream in the viewing zone. If such particles were not accelerated to the required extent, the separation gas flow would cause them to be too slow captured and carried upwards out of the classifier. This would lead to unnecessary losses of the granulate to be collected in the lower area of the classifier.

Furthermore, the speed profile achieved in the line of sight below the outlet opening of the bulk material conveying line also detects the lighter parts located in the wall area, which are to be discharged upwards from the classifier, since there are no more dead zones in the wall areas. The efficiency of the deflection counterflow classifier is considerably improved in this way.

Further details and advantages of the invention emerge from the drawings and from the exemplary embodiment described below. Show it

Fig. 1 is an overall view of a deflection countercurrent classifier in longitudinal cross section and

Fig. 2 is an enlarged view of the field of vision of the classifier, the left half of the figure represents the prior art and the right half of the figure represents an external formation according to the invention.

Description of the embodiment:

1 shows a deflection-counterflow classifier 1 according to the invention, which consists of a vertically oriented, cylindrical classifier cylinder 2 with a longitudinal axis 3 of symmetry. The entire deflection-counterflow classifier 1 has a height h, the classifier cylinder 2 has a height 1_2. In the upper opening 4 of the classifier cylinder 2, a bulk material conveying pipe 5 with a height 1.3 is concentrically embedded, which is located within the classifier cylinder 2 over a height h ^. The vertical bulk material conveying pipe 5 has an upper deflection flange 6, from which a connecting piece 7 leads laterally to a pneumatic bulk material feed line 8. The bulk material feed pipe 5 and / or the bulk material feed line 8 can also be referred to as a “bulk material feed line”.

A central tube 9 with a height hg is located within the classifier cylinder. The central tube 9 is fastened in the lower region of the classifier cylinder 2 by means of cross-shaped fastening webs 10. In the upper area, a conical tip 11 extends to the lower edge of the upper deflection flange 6.

In the lower area of the deflection counterflow classifier 1 there is a conical outlet funnel 12 with a height hg, which is extended upwards by a cylinder tube 13 with a height h ₇ . A gas inlet connector 14 is arranged on the side of the cylinder tube 13. The classifier cylinder 2 projects approximately into the cylinder tube 13 via the height η.

The cylinder tube 13 has a diameter d ^ which is greater than the diameter d2 of the lower part 15 with a height hg of the classifying cylinder 2. This results in an annular channel 16 within the cylinder tube 13, which has air guide plates 17 in its lower region Deflection of the air sucked in by the gas inlet connector 14, which flow into the classifier cylinder 2 from below according to the arrows 18. This air is guided upwards in the counterflow classifier and first reaches an annular channel 19 of the lower cylindrical part 15 of the classifier cylinder 2 with the height hg. This ring channel 19 is formed by the central tube 9, which projects into the cylindrical part 15 at a height hg. The ring channel cross-section results from the difference in diameter d2 of the cylinder section 15 minus the diameter d3 of the central tube 9.

Above the height hg or h, the lower cylindrical section 15 tapers over a first truncated cone 20 with the height h- _j and a second truncated cone 21 with the height hi ^ to a second cylinder section 23 with the height ^h 12 ^*

The air flow 18 drawn in in the lower part of the classifier cylinder 2 is consequently first compressed in the annular channel 19 to a smaller cross section (arrows 22) before it is further reduced in cross section via the two truncated cone sections 20, 21 and is thus greatly accelerated. This results in a strongly accelerated air flow in the annular channel 24 formed above the truncated cone 21, which serves as a separation gas stream 25. The two truncated cone sections 20, 21 therefore serve, with their narrowing cross section, to accelerate the separating gas flow 25. The annular channel 24 with the height h ** ^ consequently forms a cylindrical section 23 with a diameter d ^, which is used as a line of sight or separation distance for that from the Bulk material delivery line 5 coming bulk material is used.

The cylindrical section 23 for forming the annular channel 24 ends just above the lower edge 26 of the bulk material conveying pipe 5, ie. H. just above the mouth 26 of the bulk material flow in the classifier cylinder 2. This height difference is denoted by h * - ^.

The cylindrical section 23 is followed by an expanding third truncated cone 27 with the height h ₁₄ , which acts as an accelerating diffuser and which in turn is followed by a cylindrical section 28 with the height h ₁₅ and a diameter d ₅ . The cylindrical section 2 ^* 8 points an upper end region 29 through which the opening 4 is guided for the passage of the bulk material conveying pipe 5. Between the conveyor tube 5 and the cylindrical section 28, another ring channel 30 is formed, which opens laterally in a conveying material outlet connection 31.

Between the central tube 9 and the bulk delivery tube 5, a narrow annular channel 32 is formed, which has a height h ^ g, i. H. extends from the lower mouth 26 to the conical shoulder 33 of the conical tip 11.

The direction of inflow of the bulk material flow supplied to the deflection counterflow classifier 1 in the bulk material conveying line is indicated by arrow 34. The arrow 35 shows the supply of the sucked-in or blown-in air quantity, which is required as separation gas flow 25 for the sifting. The arrow 36 represents the outflow direction of the fine material sighted from the conveying material outlet nozzle 31. The coarse material cleaned from the fine material falls down through the line of sight in the countercurrent sifter and is shown schematically by arrow 37 in FIG. 1.

The lower outlet 38 of the conical outlet funnel 12 is closed by an outlet orifice 39. A cellular wheel sluice (not shown in detail) can also be provided. The decisive factor is the air flow of the supplied or sucked-in air through the counterflow classifier in the vertical direction.

The gas inlet connector 14 can also have a throttle element 40 in order to be able to regulate the separating gas stream 25 transported in the countercurrent classifier.

FIG. 2 shows the opening area of the bulk material conveying pipe 5 in the classifier cylinder 2 in a schematic representation and is explained in more detail below. there the left half of the figure shows an arrangement according to the prior art, while the right half of the figure relates to the innovation according to the invention. The same reference numerals as given in FIG. 1 have been used for the same parts. To simplify the illustration, the frustum 27 was not included. The left half of the figure in FIG. 2 is first explained as prior art:

The bulk material flowing into the bulk material conveying tube 5 is divided by the conical tip 11 of the central tube 9 and reaches the annular channel 32. The annular channel 32 is formed by the cylindrical outer surface 41 of the bulk material conveying tube 5 with the diameter, which is radially outer relative to the annular channel 32 dg and the cylinder jacket surface 42 of the central tube 9 with the diameter d ** - lying radially on the inside relative to the ring channel 32. This ring channel 32 forms an acceleration path for the bulk material flow supplied, i. H. the amount of air in the annular gap, including the entrained solid particles, is accelerated to a speed c, as is described in more detail in the "Process Engineering" reference on the deflection counterflow classifier. This shows the left half of the figure in FIG. 2

Speed profile 43, ie on the lateral surfaces 41, 42 the parabolic speed profile approaches zero. As a result, heavier solid particles 48 lying in the wall areas are not accelerated up to the maximum speed c _ιnaχ> , but for example only to a speed c ^ on the wall section 41 and C2 on the wall section 42, these speeds c * ^, C2 not sufficient, that from below to penetrate coming separation gas stream 25. Consequently, the coarse particles 48 falling in the edge region of the walls 41, 42 will not, contrary to their intended purpose, reach the countercurrent sifter downwards, but rather as losses upwards into the outer ring channel 30 for the removal of the fine material 49 arrive (arrow 44). These losses of the coarse material 48 discharged with the fine material 49 are shown schematically by arrow 45.

Furthermore, the separating gas stream 25 coming from below also forms a speed profile 46, which is established in the annular channel 24 below the mouth 26. Here, too, the flow velocity V _{G of} the separation gas flow in the wall areas approaches zero, since the flow profile 46 drops sharply in the direction of the wall sections. The result of this is that there is only a slight upward flow of the separating gas stream 25, in particular on the radially inner cylinder jacket surface 42 in the annular channel 24, which is indicated by the speed arrow 47. As a result, fine material falling down in this near wall area of the radially inner cylinder jacket surface 42

49 can penetrate the insufficiently present separation gas flow 25 almost unhindered and undesirably reaches the lower area of the counterflow classifier.

In order to counter this disadvantage, according to the illustration on the right in FIG. 2, both the radially outer lateral surface 41 and the radially inner lateral surface 42 with a surface structure are initially in the annular channel 32

50 provided, which leads to strong turbulence of the air flow in these wall areas. As a result, the speed profile 43 'is not designed to drop sharply towards the wall areas, but rather is designed in the manner of a rectangle with almost equally large speed vectors c also in the respective edge areas. The result of this is that the total amount of conveying gas, including entrained solid particles, is brought to the required high speed in the acceleration section in the ring channel 32, so that the coarse material 48 also has the required speed c in the wall _area! has the bottom up to penetrate directional separation gas stream 25. This means there is less loss of coarse material.

The wall section 42 of the central pipe 9 lying below the mouth 26 of the delivery pipe 5 also has a corresponding surface structure 50 ′, which corresponds to the surface structure 50 lying above it. This also results in a speed profile 46 ′ in the annular channel 24, which has a substantially steeper profile, in particular in the region of the radially inner wall section 42, which is generated by corresponding turbulence. As a result, a higher separation gas flow velocity ^V _G -W is present in this wall area, which prevents fine material 49 from falling. 2, on the right half of the figure, both a discharge of coarse material 48 with the fine material 49 into the ring channel 30 and a discharge of fine material 49 into the lower region of the classifier are avoided. This increases the effectiveness and efficiency of such a classifier considerably.

The surface structure 50, 50 'can be designed as a zigzag-shaped surface structure. The distance a between two adjacent tips 52, 52 'is selected such that it is generally smaller than the diameter D or the particle length of the solid particles 48 forming the coarse material.

The surface structure 50 can also be roughened or formed by other suitable measures, so that corresponding eddies for generating turbulence arise. This can be, for example, a surface formed by a hammer blow with indentations in the form of spherical segments or a wave structure with a pointed wave crest or the like. Other swirling edges can also be provided. The surface structuring 50 within the ring channel 32 preferably extends over a height section h- ^ ₇ which covers the entire acceleration distance, ie the entire ring channel 32. As a result, all particles are subjected to the acceleration required in order to achieve a desired final speed, even in the edge region.

In the annular channel 24 for the upward separating gas stream 25 there is essentially a turbulence-generating surface structure 50 'on the radially inner wall section 42, i. H. on the outer cylinder surface of the central tube 9 is necessary, since this area is influenced by the flow of material to be conveyed from the ring channel 32 lying above it. The height h- ^ g of the roughened surface structure 50 'for generating turbulence is therefore chosen in a similar order of magnitude as the height section h ^.

As can further be seen from the illustration according to FIG. 1, the gas inlet connection 14 is arranged as far as possible in the lower region of the circulation countercurrent sifter 1 in order to obtain the largest possible distance for the ascending separation gas flow 18, 22, 25. Furthermore, this distance can be used to generate an acceleration of this separation gas flow due to a diffuser effect. Finally, a long distance of the separation gas flow can have the effect of inspecting fine material, i.e. H. Fine material, which has nevertheless penetrated the separation section in the annular channel 24, can still be detected in a lower section due to the ascending counterflow.

The invention is not restricted to the exemplary embodiment described and illustrated. Rather, it also encompasses all professional further training within the framework of intellectual property rights claims. Deflection-countercurrent classifier cylinder symmetry longitudinal axis opening bulk material feed pipe deflecting flange connecting piece bulk material feed line central tube short fastening webs conical tip outlet spout / funnel cylinder tube glass insert neck lower part of 2 ring channel air guide plates air / arrow ring channel 1. truncated cone 2. conical flow channel separating ring / arrow Bottom edge / Reduction 3rd truncated cone cylindrical section End area Ring channel Conveying material outlet connection Ring channel cone shoulder Arrow Arrow Arrow Arrow Outlet outlet orifice Throttle element radially outer lateral surface radially inner lateral surface Speed profile arrow Bulk material conveying line Bulk material conveying line Bulk material conveying line coarse material fine surface structure arrow Point

Claims

Claims:

1. Deflection-countercurrent sifter with a cylindrical, vertically oriented sifter cylinder (2) in the upper area concentrically immerses a bulk material conveying pipe (5) which, at least in its lower mouth area (26), has an inner, annular channel-shaped acceleration section (32) for the has bulk material flow transported by means of a conveying gas, the conveying gas flow having a separating gas flow directed from bottom to top, which serves to separate the bulk material flow into lighter and heavier constituents, and the lighter constituents (fine material 49) through a bulk material conveying pipe (5) surrounding annular channel (30) can be transported upwards out of the classifier cylinder (2), while heavier bulk material parts (coarse material 48) penetrate the separating gas stream (25) and get down into the classifier cylinder (2), characterized in that at least the radially inner cylinder jacket surface ( 42) the ring channel shaped acceleration path (32) at least in the lower mouth region (26) of the bulk material conveying pipe (5) and / or at least the radially inner cylinder jacket surface (42) of the ring channel (24) guiding the separating gas flow (25) each has a surface structure (50, 50 ') has, which leads to increased turbulence and thus to a

Speed increase of the respective air flow leads to the respective wall section.

2. Deflection-countercurrent classifier according to claim 1, characterized in that the radially inner (42) and the radially outer (41) cylindrical jacket surfaces of the annular acceleration channel (32) in the bulk material conveying pipe (5) is a surface structure (50) designed as a surface roughening. have, which leads to increased turbulence of the bulk material conveying gas in the wall area.

3. Deflection-countercurrent classifier according to claim 1 or 2, characterized in that the annular acceleration section (32) in the bulk material conveying pipe (5) and the annular channel flow section (24) for the separating gas flow (25) concentrically by a in the classifier cylinder (2) arranged central tube (9) is formed in particular with a conical tip (11).

4. deflecting countercurrent classifier according to claim 3, characterized in that the central tube (9) at least in the region of the mouth (26) of the bulk material conveying tube (5) in the classifier cylinder (2) extending up and down Wall portion (42) with the height h ** ^, h ^ g, which comprises a surface structure (50, 50 ') for generating increased air flow turbulence and thus increased particle speeds.

5. Deflection-countercurrent classifier according to one of the preceding claims, characterized in that the surface structure (50, 50 ') for generating increased air flow turbulence is designed as a zigzag-shaped surface roughening, the distance a between two adjacent tips ( 52, 52 ') is smaller than the largest diameter D or particle length of the coarse material portion (48).

6. Deflection countercurrent classifier according to one of the preceding claims 1 to 5, characterized in that the surface structure is formed in cross section as a wave structure with a pointed wave crest.

7. Deflection countercurrent classifier according to one of the preceding claims, characterized in that the surface structure has swirling edges.

8. Deflection-countercurrent sifter in particular according to claim 1, characterized in that the radial inlet opening (14) for the separating gas flow (25) is arranged in the lower region of the countercurrent sifter to form a viewing section.

9. deflecting countercurrent classifier according to one of the preceding claims, characterized in that the classifier cylinder (2) has in its lower region an outlet funnel (12) with an upwardly continued cylinder section (13) which laterally has a radially entering gas inlet connection (14) for the separating gas flow and that the separating gas flow can be deflected into the classifier cylinder (2) via air guide plates (17).

10. Deflection-counterflow classifier according to one of the preceding claims, characterized in that the conical outlet funnel (12) has a closable outlet opening (38).

11. Deflection countercurrent classifier according to one of the preceding claims, characterized in that the gas inlet connection (14) is associated with a throttle member (40).