EP0178316A1

EP0178316A1 - Cyclone.

Info

Publication number: EP0178316A1
Application number: EP85902020A
Authority: EP
Inventors: Hans Oetiker; Franz Reichmuth
Original assignee: Buehler AG
Current assignee: Buehler AG
Priority date: 1984-04-16
Filing date: 1985-04-15
Publication date: 1986-04-23
Anticipated expiration: 2005-04-15
Also published as: DE3576067D1; SU1484282A3; JPH0119942B2; US4721561A; UA6001A1; WO1985004823A1; DE3414344A1; DE3414344C2; JPS61501196A; EP0178316B1

Abstract

Un séparateur cyclone pour des fragments de graines, des enveloppes, de la poussière et d'autres impuretés de l'air possèdent une chambre de préséparation (2) avec une entrée tangentielle de gaz brut (1), dans laquelle sont disposés concentriquement un grillage déflecteur cylindrique (4) et une sortie de gaz pur (5) raccordée à celui-ci. Afin d'augmenter le degré de séparation de la poussière avec une faible perte de pression et une construction peu coûteuse et de permettre une utilisation dans des systèmes à circulation d'air en combinaison avec d'autres machines de traitement et de nettoyage de céréales, une chambre de préséparation (X) est prévue radialement à l'extérieur du grillage déflecteur (4) pour une circulation d'air, ainsi qu'un évent (Y) radialement à l'intérieur du grillage déflecteur (4), qui est en relation d'écoulement avec la chambre de préparation (X) grâce à des canaux de passage d'air (17) dans le grillage déflecteur (4).A cyclone separator for seed fragments, husks, dust and other air impurities has a pre-separation chamber (2) with a tangential raw gas inlet (1), in which a screen is concentrically arranged cylindrical deflector (4) and a pure gas outlet (5) connected thereto. In order to increase the degree of dust separation with low pressure loss and inexpensive construction and to enable use in air circulation systems in combination with other grain processing and cleaning machines, a pre-separation chamber (X) is provided radially outside the deflector screen (4) for air circulation, as well as a vent (Y) radially inside the deflector screen (4), which is in flow relationship with the preparation chamber (X) by means of air passage channels (17) in the deflector screen (4).

Description

-i-

Title: Flee Raitabscheider

i g Technical area

The invention relates to a centrifugal separator for broken grains, shells, dust and other contaminants from air, with a pre-separation chamber with tangential raw gas inlet, a cylindrical deflection grille arranged concentrically therein and a clean gas outlet axially adjoining the deflection grille.

State of the art

2 Centrifugal separators have been used successfully in the area of mills and feed mills for decades. The great advantage of traditional cyclone separators is their simple construction and their relatively low air resistance. As a rule, the cyclones are positioned with a vertical axis, in rare cases slightly inclined

25 used. The separated substances are collected in the lower area of the centrifugal separator and discharged via a product lock. The air enters the cyclone tangentially in the upper circumferential area and leaves it after several whirling movements centrally in the uppermost area through the so-called "immersion tube", which is somewhat into the

_O Q inside of the cyclone protrudes.

The main disadvantage of a cyclone lies in its relatively poor degree of efficiency for dust separation. In the cyclone a variety of overlapping secondary vortices that prevent along with a ₃₅ fluctuating air pressure and varying dust load in practice a substantial improvement in the degree of separation is created. On Another disadvantage is that, especially in the area of a mill or a feed mill, when using cyclones as separators, the exhaust air still has residual dust contents which are substantially above the legally permissible values. The exhaust air from the cyclones for industrial systems must therefore also be cleaned via filters before it can be discharged into the open.

To date, many suggestions for improving cyclone separators have already been made, but with a few exceptions, they have not been successful in practice. One of these exceptions is described in DE-B-1.078.859. A centrifugal separator with a horizontal axis is used there in the form of a double centrifugal separator or a primary and a secondary separator. The primary separator is of spiral and approximately circular construction, the raw gas entering being tangential. At the opposite end of the spiral space, the outermost air layer is, as it were, "peeled off" and introduced into a much smaller secondary separator, in which (similar to traditional cyclone separators) the clean air or dust is separated on both ends. One advantage of this separation system is the very low pressure drop, but its disadvantage is an insufficient degree of separation.

In recent times there has been a tendency to use individual cleaning machines that require very large amounts of air, e.g. to be used in a mill in recirculation mode (see e.g. GB-A-i.536.905). Air-circulation machines, however, require relatively clean air and this for two reasons: If too much dust is kept in circulation, there is a risk of permanent bacterial contamination of the goods, especially if it is raw material for human consumption. If there is a lot of dirt and dust in the circulating air, the whole machine will be clogged with dust in a short time. Either frequent breakdowns or a lot more cleaning work has to be done.

The quality requirements for the recirculated air do not have to be as high as the legal requirements for the quality of industrial exhaust air to the outside, but experience has shown that the quality requirements for the recirculated air are still much greater than the performance ability of known centrifugal separators or cyclone separators could be guaranteed.

Disclosure of the invention

Proceeding from this, the object of the invention is to develop a centrifugal separator for broken grains, shells and dust as well as other contaminants from cereals, which, with only a slight pressure loss, has a significantly increased degree of dust separation, is not very complex, and is particularly suitable in combination with others Grain cleaning and processing machines are suitable for use in circulating air systems.

According to the invention, this object is achieved in a centrifugal separator of the type mentioned at the outset in that a pre-separation space for air circulation is provided radially outside the deflection grille and an air extraction is provided radially inside the deflection grille, which is in flow connection with the pre-separation space via air passage channels in the deflection grille. The invention creates two spaces that are precisely defined and controllable in terms of flow technology, as a result of which very extensive separation of impurities from the air can be achieved.

In an advantageous development of the invention, the pre-separation area is circular in cross-section and is arranged directly above a funnel-shaped collector which is separated from the pre-separation area by a curved deflecting wall in such a way that air circulation openings remain on both outer sides of the pre-separation area.

The centrifugal separator according to the invention was first tested in connection with an aspiration channel with a preselected dust load, with surprisingly good results.

The tangential raw gas inlet preferably has an inlet arranged in the same direction as the pre-separation chamber. In this very particularly preferred embodiment of the centrifugal force ^* - The effect of centrifugal force is well prepared in the inlet of the pre-separation area. Disturbing "superimposed" vortices are avoided as soon as they enter the pre-separation area, especially if the tangential raw gas inlet extends essentially over the entire length of the pre-separation area.

The best solution has so far been found to be a raw gas inlet in the upper area of the pre-separation room, in which the direction of the air flow in the pre-separation room is clockwise, the air from the raw gas inlet

- ^{* <} - ⁾ flows into the pre-separation area from bottom left to top. This results in a particularly undisturbed flow and a remarkably effective separation of the contaminants from the air if the deflection grille has an upper, air-impermeable section. The air is surprisingly clearly enriched in the course of one

- ^* * - ^■ half circle in the pre-separation area in the zone close to the wall with the foreign substances present in it, so that this outer fuel-enriched partial flow can release all foreign substances upon passage into the funnel-shaped collector. Two main effects occur in the collector itself: on the one hand, the foreign substances fall as a result

20 gravity down; secondly, the centrifugal force acts again, since all the air flowing into the collector can flow back into the pre-separation channel on the side of the collector opposite the inflow point. It cannot be avoided that individual dust or shell parts are entrained again.

- 'S However, as tests show, the probability that these parts will still settle down in the collector in a subsequent run is very high.

The inner partial flow largely freed of foreign matter enters the space between the curved deflection wall and the deflection grid on the inside. Unfortunately, it is unavoidable that a small amount of dust particles and spray particles are entrained with the inner partial flow. In order to also clean the internal partial flow of these foreign parts, various further 35 advantageous configurations of the invention have proven themselves:

In a particularly preferred further development, the inventor fertilize the deflecting grille only in its lower section of air passage channels. Furthermore, the air passage channels are preferably arranged in the deflecting grille in the region thereof which faces the circularly curved deflecting wall or is opposite. Furthermore, the deflection grating has, with particular advantage, essentially guide vanes arranged radially, that is to say transversely to the rotational flow of the air, wherein, again preferably, air passage channels between the guide vanes form a deflection angle for the air flow of more than 90. Furthermore, the air passage channels are preferably designed such that the extracted air quantity enters the clean gas outlet without swirl.

In a centrifugal separator according to the invention, it is also particularly advantageous if a channel for returning the air to the pre-separation space is provided in front of the funnel-shaped collector in the region of the raw gas inlet. The space between the deflecting grating and the circularly curved deflecting wall is particularly preferably formed in a spiral taper and opens, again preferably, into the air return duct.

For air circulation free of transverse vortices, the deflection grille is preferably closed at an angle of more than 180 in its upper region. In addition to the advantageous embodiment of the invention, it is proposed to have the circularly curved deflection wall begin in the region of the horizontal central plane of the deflection grille and to execute it over an angle in the range between 90 and 180.

In a further preferred embodiment of the invention, the raw gas inlet is designed as the upper end of a vertical aspiration channel, the clean gas outlet preferably being connected to a lower inlet arranged on the aspiration channel in such a way that the aspiration channel operates in recirculation mode. The best results for a targeted selection of a desired grain material fraction in the aspiration channel and for a subsequent separation of the remaining grain material fractions or shells or dust parts in the centrifugal separator can be achieved if, in the case of a centrifugal separator according to the invention, a rear wall of the aspiration channel is inclined as well as in its horizontal direction is adjustable (thus in two respects).

The centrifugal separator according to the invention has proven surprisingly well when used in combination with an aspiration channel for grain. In this application, all good and heavy cereal grains are to be freed of any foreign material (ie shell parts, dirt, dust, also broken and languid grains or the like) through the aspiration channel. In the past, the complete and economical separation of the relatively large amount of foreign material from the air has proven to be a major problem, the solution of which has so far not been satisfactorily possible. Here, for the first time, the use of a centrifugal separator according to the invention showed a completely satisfactory separating effect, which could not even be achieved to date.

Brief description of the figures

The invention is explained in more detail below in principle with reference to the drawing. Show it:

Figure i shows a basic section through a centrifugal separator according to the invention;

Figure 2 shows the section II - II of Fig. I;

FIG. 3 the combination of an aspiration channel with a centrifugal separator according to the invention;

Figure shows the section IV-IV of Fig. 3, and

Figure 5 shows a further embodiment of the air and dust guidance in a centrifugal separator according to the invention.

Detailed description of the figures

As can be seen from Figure 1, the essential basic structure of the centrifugal separator consists of a tangential raw gas inlet 1, a pre-separation chamber 2 and a funnel-shaped collector 3. Within the essentially circularly extending pre-separation chamber 2, a preferably fixed deflection grid 4 is provided, at its inner axial end a clean gas outlet 5 is arranged. The pre-separation Room 2 is delimited at the bottom by a circularly curved deflecting wall 6, air circulation openings η and 8 remaining on both sides. The baffle 6 starts (in Figure i: right) approximately at the level of the horizontal center plane of the deflector 4 and extends over a range of more than ⁰ to 90 on the left side image over.

The deflecting wall 6 consists of a curved steel sheet, the same radius of curvature being present on both sides in the direction of the pre-separation space 2 as towards the collector 3. For a greater deflection of the air flow into the collector 3, the lower boundary of the deflection wall 6 can e.g. be carried out according to the line 10 shown in broken lines. The collector 3 has a conical funnel 11 and at the bottom a rotary lock 12 for the airtight dust discharge.

It has proven to be advantageous if a straight duct section 13 is connected directly upstream of the raw gas inlet so that the flow in the area of the raw gas inlet 1 is as far as possible calmed down. The raw gas inlet 1 is separated in a sector of almost 90 from the pre-separation room 2 via a wall section 14.

The upper part of the deflection grid 4 is air-impermeable as a cylindrical jacket 15. The deflection grating 4 has a plurality of radially oriented guide vanes 16 only in its lower part, an air passage opening 17 being formed between each two guide vanes 16. The outer section of the guide vanes 16 is inclined at an angle, so that the incoming flow, in order to penetrate there into the space between two guide vanes 16, must deflect by more than 90. Reference is expressly made here to the graphic representation of this bending of the outer sections of the guide vanes 16 in FIGS. 1, 3 or 5. This measure forces the air to undergo a relatively strong change in direction when it enters the clean gas outlet 5. Even finer dust particles cannot take part in this change in direction due to their inertia and are torn by the rotational flow into a separating channel 18 into the area of the air circulation openings 7 and 8 and reach the zone of the raw gas inlet 1 again. In a second or repeated run these foreign 1 parts in the collector 3 worn and deposited.

The air passage openings 17 are oriented radially inwards, so that a swirl-free flow is created in the interior and any 5 approach of one-sidedness in the flow play within the pre-separation chamber 2 is avoided.

1 shows a Vortrennzone X is shown hatched, in which a strong circulation of air takes place, so that dust particles repeatedly opportunity _Q are integrated, to precipitate in the collector 3 in a zone D. The inner area enclosed by the pre-separation zone X, which is not hatched in FIG. 1, is referred to as "swirl-free air extraction" Y, in which a controllable separation of clean air and residual dust takes place which is unaffected by the air circulation in the pre-separation zone X. 5

FIGS. 3 and 4 show a further exemplary embodiment of a centrifugal separator according to the invention, which works in a sensible manner with a vertical aspiration channel. The solution shown here enables a particularly effective selective separation of _{Q of} good quality from the grain and the rest of the poorer grain qualities (such as broken grain and sluggish grain) and the other undesirable dirt and solids still present in the grain by means of air possible.

The removal of very coarse additives that are larger than cereal grains is carried out using classifying sieves; Stones are removed by stone readers. These two operations should preferably be carried out in a previously performed operation.

_Q The separation achieved by the centrifugal separator according to the invention takes place in principle in four spatially separate zones:

A first zone A in the initial area of the aspiration channel 21 represents the pre-sorting zone known per se. Here, the unpurified grain material is fed in and well ventilated by an air jet. All heavy grains fall down; Both a medium fraction and the undesirable light additions are caused by the air Current continues into the aspiration channel 21, namely carried into an adjoining zone B. This zone B allows the middle fraction to be divided into a fraction that still belongs to the heavy, good grains, and a lighter fraction, which is mixed with the rest of the admixtures by the air flow into a subsequent zone C, which consists of Pre-separation zone X and the swirl-free air extraction. Y exists, is promoted.

In a fourth zone D, which is in collector 3, the remaining stock of air (such as dust etc.) is finally separated.

The division in the aspiration channel 21 also takes place here in that the flow profile in the aspiration channel 21 can be specifically adapted to the particular separation task. Depending on their rate of descent, the individual particles are thrown into the canal by the air flow at uneven heights and fall down again. This process may be repeated several times until the particle either finds its way up or all the way down.

Di ^e zones A and B flow smoothly into one, since the air flow must develop its Wirkkxaft. This is where the grain is introduced into the air, the grain is cleaned of foreign material and the fraction to be separated is removed by the air.

The function in zones C and D is fundamentally different:

The main idea here is that the entire foreign material to be separated is concentrated in a specially created room, namely Zone C, in an outer boundary layer of the air flow. Only this concentrated boundary layer is introduced via a defined channel, namely via the air circulation openings 7, into zone D, ie into the collector 3, where almost all of the foreign material can be excreted. Due to the interaction of the two zones C and D, but now a completely new advantage comes into play, which is that individual spray particles or randomly by the air flow from the manifold 3 again broken into the zone C particles ^■ a second, third or repeated time the sequence zone C-zone D can run through until they are finally deposited in collector 3 (Zone D). Zone C is of such great effectiveness that only a negligibly small proportion of dust through the deflection grid 4 with the

Clean air is entrained. This very low dust level is now completely negligible in the entire system, which preferably works as a recirculation system, as tests have shown.

Such a system is shown in FIGS. 3 and 4:

The raw grain is fed through a feed or metering device 20 into an aspiration channel 21, from where it enters a small feed chamber 23 via a feed pipe 20. An eccentric drive 24 shakes them over a correspondingly elastically mounted dining table 25, as a result of which a uniform product curtain of approximately the same length enters the aspiration channel 21. The air is led from a circulating air duct 26 through the product curtain into the aspiration duct 21. There, a wall 28 is arranged to be doubly adjustable, so that the aspiration channel 21 can be adjusted both in terms of the flow cross section and in terms of its shape in the direction of flow. For the aspiration channel 21, an approximately constant cross-section or a V-shaped cross-section (i.e. a cross-section that increases or decreases in the direction of flow) can be set from bottom to top. In the air circulation system shown in FIGS. 3 and 4, a radial fan 30 is installed directly in the area of a clean gas outlet 29, which ensures the necessary air circulation for the air circulation. The entire amount of air is returned via the air recirculation duct 26. The cleaned grain is passed over an outlet funnel 32 for further transport, flap locks 33 are also provided here to avoid malfunctions in the false air and undesirable air vortices. The separated admixtures are also transferred to the correspondingly determined further transport via the rotary lock 12. The required amount of air can be set via the speed of the radial fan 30.

Of course, the solution according to FIGS. 3 and 4 can also only work partially as a recirculation system. In this case, a corresponding aspiration port 34 with air adjustment flaps 35 is on -I I- Aspiration system connected and the whole device can be put under slight negative pressure.

With a corresponding structural redesign, it would also be conceivable to rotate the deflection grid 4 as such. In such a solution, the upper part of the deflection grating 4, which is designed as an air-impermeable jacket 15, would preferably be constructed to be stationary.

In the sections in which there is no fear of the occurrence of spray particles, the jacket 15 could have openings for the air to enter. It has been shown that the jacket 15 should remain closed at least at the point at which the raw gas inlet 1 enters the pre-separation chamber 2 and at the beginning of the deflection wall 6.

FIG. 5 shows a further variant for a centrifugal separator according to the invention.

A vertical duct section 40 works as an aspiration duct as in the illustration according to FIG. 1, however, unlike in FIG. 1, a relief space 41 is directly associated with it, so that in the event of a circulation of air from the pre-separation space 2 or a corresponding circulation duct 26 (FIG. 4 ) Part of the air can circulate in the duct section 40 and part of the air in the relief space 41. The optimum air volume or air speed can be set via an adjustment flap 42 which acts as a throttle, as indicated by the two arrows 43 and 44 in FIG. 5.

Furthermore, a division of the flow in the pre-separation chamber 2 by a further flap 45 is possible in such a way that the greater part of the circulating air is deflected into the pre-separation zone X or into the inner swirl-free air vent Y. In this way, the amount of air that flows out as clean air through the clean gas outlet 5 is not influenced, but the local air velocities in the separating space 18 and in the air circulation opening 7. The two working spaces X and Y can be targeted in this way, even for very delicate separating tasks, such as in the separation of corn fractions.

Claims

5 patent claims

i. Centrifugal separator for broken grains, shells, dust and other --0 impurities from air, with a pre-separation chamber (2) with tangential raw gas inlet (1), a concentric cylindrical deflection grille (4) and a clean gas outlet axially adjoining the deflection grille (4) (5), characterized in that a pre-separation chamber (X) for air IS circulation and radially inside the deflection grid (4) an air vent (Y) is provided radially outside of the deflection grid (4), which is connected to the pre-separation chamber (X) Air passage channels (17) in the deflection grille (4) are in flow connection.

2. Centrifugal separator according to claim 1, characterized in that 20 of the pre-separation chamber (2) is circular in cross-section and is arranged directly above a funnel-shaped collector (3) which is on its top by a curved peripheral wall (6) from the pre-separation chamber (2 ) is separated in such a way that air circulation openings (7, 8) remain on both outer sides of the pre-separation space (2). 25

3. Centrifugal separator according to claim 1 or 2, characterized gekennzeich¬ net that the tangential raw gas inlet (1) has an inlet arranged in the same direction to the Vortrenn¬ space (2).

30 4. Centrifugal separator according to one of claims 1 to 3, characterized in that the deflection grid (4) has an upper air-impermeable section.

5. Centrifugal separator according to one of claims 1 to 4, characterized 35 indicates that the deflection grille (4) has air passage channels (17) only in its lower section.

6. Centrifugal separator according to one of claims 2 to 5, characterized in that the air passage channels (17) are arranged in the deflecting grille (4) in the region thereof facing the circularly curved deflecting wall (6).

7. centrifugal separator according to claim 5 or 6, characterized gekennzeich¬ net that the deflection grid (4) has substantially radially arranged guide vanes (16).

8. centrifugal separator according to claim 7, characterized in that the air passage channels (17) between the guide vanes (16) form a deflection angle for the air flow of more than 90.

9. centrifugal separator according to claim 8, characterized in that the air passage channels (17) are designed so that the extracted

Air volume swirl-free opens into the clean gas outlet (5).

10. Centrifugal separator according to one of claims 2 to 9, characterized ge indicates that in front of the funnel-shaped collector (3) in the region of the raw gas inlet (1) a channel (8) is provided for returning the air into the pre-separation chamber (2) .

11. Centrifugal separator according to one of claims 2 to 10, characterized in that the space between the deflection grating (4) and the circularly curved deflection wall (6) is designed to be spirally tapered.

12. Centrifugal separator according to claim 11, characterized in that the space between the deflection grid (4) and the circularly curved deflection wall (6) opens into the air return duct (8).

13. Centrifugal separator according to one of claims 1 to 12, characterized in that the deflection grid (4) is closed in its upper region over an angle of more than 180.

14. Centrifugal separator according to claim 2, characterized in that the circularly curved deflection wall (6) in the region of the horizontal Middle plane of the deflection grid (4) begins and extends over an angle between 90 ⁰ and 180.

15. Centrifugal separator according to one of claims 1 to 14, characterized in that the raw gas inlet (1) has the upper end of a vertical

Aspiration channel (21) forms.

16. Centrifugal separator according to claim 15, characterized in that the clean gas outlet (5) with a lower on the aspiration channel (21) arranged inlet is connected such that the aspiration channel (21) works in recirculation mode.

17. Centrifugal separator according to claim 15 or 16, characterized gekenn¬ characterized in that a rear wall (28) of the aspiration channel (21) is adjustable both in its inclination and in the horizontal direction.