EP0293426A1

EP0293426A1 - Installation and process for the dry-grinding of granular foodstuffs and feedstuffs.

Info

Publication number: EP0293426A1
Application number: EP87907955A
Authority: EP
Inventors: Roman Mueller
Original assignee: Buehler AG
Current assignee: Buehler AG
Priority date: 1986-12-01
Filing date: 1987-12-01
Publication date: 1988-12-07
Anticipated expiration: 2007-12-01
Also published as: PL156517B1; ES2008362A6; CN1009620B; DE3771495D1; EP0293426B1; KR890700408A; US4971684A; WO1988004204A1; CH672440A5; UA6002A1; JPH0651176B2; ATE65194T1; AU8330687A; JPH01501531A; SU1641185A3; PL269157A1; CN87101243A; KR930008288B1

Abstract

PCT No. PCT/EP87/00747 Sec. 371 Date Sep. 22, 1988 Sec. 102(e) Date Sep. 22, 1988 PCT Filed Dec. 1, 1987 PCT Pub. No. WO88/04203 PCT Pub. Date Jun. 16, 1988.A size grading unit and a gravity grading unit in a grinding preparation installation form an oscillating unit and are arranged one above the other so that a V-shaped space exists between them. The product flow transfers as a carpet or veil falling from the size grading unit at the V apex to the gravity grading unit located below. Air flows through the V-shaped space but not through the size grading unit.

Description

Plant and method for the dry preparation of granular food and feed

Technical field:

The invention relates to a system for dry grinding preparation of grain-like food and feed, such as cereals, in particular for cleaning, separating into different fractions and preferably for reading out foreign material such as sand, stones, clods, etc., which have a size classification unit, e.g. . Eg sieves, as well as a weight classification unit, e.g. For example, as a stone reader, light grain reader, etc.

State of the art:

Recently, the number of special machines for dry grinding preparation, sometimes also called cleaning, of cereals has been greatly reduced in a mill system. In contrast, a group of standard units, such as

Sieve devices and stone readers, more and more also light grain readers, can be found in almost every new mill system. Each unit or device is designed for its specific task and provided with exhaust air, vibrators, etc. The very special Fish training allows both the required air and the vibration energy to be used in a targeted manner with the least possible expenditure for construction and operation, so that an increased throughput and a higher quality of work can be achieved with the lowest possible investment costs, compared with the still older practice .

The currently built mill systems mostly have four building complexes next to one another, a first one for the silo, a second one for the grinding preparation, a third one for the grinding or mill and a fourth one for the finished products.

The machines for preparing the grinding and for grinding are distributed over four or five floors. Depending on the desired storage capacity, the storage silos usually tower above the mill building. What is, as it were, the most natural thing about the storage silos, namely the discharge through openings in the floor with the corresponding downward movement of the product by gravity, has also been used in the machines for dry grinding preparation for many decades. Here, too, the product is fed into the machines of the top floor, in order to then move solely through the force of gravity, i.e. without technical use of additional energy for transport, from floor to floor or from machine to machine down z '.

Every milling specialist knows that the preparation for grinding, in particular the dry preparation (cleaning, separating, reading out, etc.) of the raw material should be given as much attention as the grinding itself. This manifests itself in the fact that in most There is sufficient space in the mill system for the grinding preparation / cleaning machines, so that no immediate need for further concentration is known.

A fundamental disadvantage of dry grinding preparation results from the floor-by-floor connection of the grinding preparation machines. For the sorting, classifying and separating process, the entire product or material flow in the respective machine is brought into a flat thin layer or a thin falling veil. The product stream is then bundled again for transfer to the next machine, in order then to be spread out again flat after the transfer.

A specially designed inlet section is required for the uniform planar formation of a product bed. This is to prevent the initial part of the machine from doing what it wants

Work, based on the area, is poorly used.

In many cases the idea was played that one machine would be lined up on the same floor. Judging by the quality of work, this would be an advantage. However, since each machine requires different optimal conditions, there would be structurally very complex transition pieces, in particular if the neighboring machines vibrate in a directed manner. Process engineering repeatedly shows that machines with a large surface area are difficult to control. Malfunctions are recognized late, so that often a small malfunction in the previous stage can adversely affect the next stage for a longer period. Presentation of the invention

The invention is concerned with the problem of improving the dry grinding preparation, preferably in such a way that it is possible to concentrate the work processes, but preferably while maintaining the manageability of each step, the possibility of influencing each step, particularly preferably under Achievement of at least the same throughput and work quality as before.

The solution according to the invention is characterized in that the size classification unit and the weight classification unit form a vibration group in the grinding preparation systems mentioned at the outset, and are arranged one above the other in a fork or V shape, so that a fork or V-shaped space is created; Means are provided for transferring the product flow in the manner of a product carpet or veil falling from the size classification unit at the fork point to the heavy classification unit located below? and finally means for generating an air flow through the fork or. V-shaped space, but not due to the size classification unit.

It is often the case with new inventions that you no longer understand why, as it were, the simplest and most optimal solution was not used long before. One looks for reasons why others working in the field did not come up with the idea of the inventor. Heavy class requires a very strong ventilation to form a fluid bed. In contrast, the actual sieves may now be slightly aspirated, since otherwise parts would easily stand out and on the Float the surface of the flowing bulk layer. The fork-shaped arrangement of the size classification unit and the weight classification unit results in two decisive advantages. The product transfer from the upper size classifier (sieve) to the underlying heavy classifier takes place evenly over the entire width of the sieve; This means that the multiple change between the flat product flow and the tubular product flow described above is now within all (three) basic functions, ie

- that of size classification (screening)

- the severity classification, here

- the division of light and heavy and

- the stone reading

completely disappears. A flat, uniform product layer only has to be produced at the (first) entry point of the product into the "compact device" according to the invention. After that, it just has to be maintained.

The invention thus enables an impressive solution to the problem mentioned with the simplest measures and, in addition, even better use of the work surfaces.

In principle, a separate oscillating drive can be provided for the ^* size classification unit and for the weight classification unit. However, the oscillation group formed from the size and weight classification unit preferably has a common oscillation drive, so that an identical oscillation (identical direction, frequency and amplitude) is impressed on both units. In front- The oscillating drive is preferably arranged on both sides, for example on a horizontal center of gravity, of the oscillating group in such a way that a throwing vibration for upward conveyance is generated for the weight classification, while a throwing oscillation for downward conveying is generated for the size classification. All work surfaces therefore carry out an optimal swinging movement. Experiments have confirmed that the new idea enables a sharp separation process even at high throughputs.

In a further advantageous embodiment, the means for generating air flow have a bottom which closes the size classification unit (sieve device), a suction fan preferably being connected to the expanded side of the aspiration space between the size classification unit and the weight classification unit. By placing the closed bottom underneath the sieve, the sieve section can easily be separated from the fluidized bed in relation to the air.

The aspiration space widened on one side is very particularly preferably divided into at least two exhaust chambers, namely an upper and lower exhaust chamber, with adjustable air throttles being assigned to each exhaust chamber.

This allows the air distribution to the gravity classifier to be regulated in a very simple manner with any desired accuracy, without any negative influence on the size classification unit located above it. In this way, each individual function can be set to the desired maximum requirement. However, the idea according to the invention allows various further very advantageous configurations. So z. B. open the lower end of a light grain reader directly into a vertical aspiration channel in order to be able to read a light fraction from the rejection of the gravity classifier.

This combination shows the advantages of the invention particularly well, since the product is brought into a flat layer when it enters the compact device according to the invention. This flat product layer is now on the entire processing path through the compact device, ie on its way from the screen of the size classifier over the concentrator and finally over. maintain the stone picker without interruption. Correspondingly, the dust air can also be routed via a duct into the aspiration duct, which also works flatly. For the viewer, an image is created as if a textile web was pulled through a printing press and the corresponding work processes were carried out step by step on the belt.

As a particularly interesting further development idea, the invention allows the aspiration space, which widens on one side, to be provided with an air suction device which, via a dust separator, leads the air back to the suction side of the stone reader in recirculation mode.

This idea brings great progress in many applications, especially in small and medium-sized milling plants. The invention thus enables the plant for dry grinding preparation, which previously consisted of several individual machines, in which each individual machine a good aspiration for intensive ventilation and the whole system needs a central air filter system, now to build as a closed, compact machine.

The new invention allows all work steps to be operated in one unit, in many cases without a filter, with circulating air.

The gravity classification unit very particularly preferably consists of two classification tables arranged one above the other and through which the same air flows. It is possible that the upper classification table as a concentrator. Light grain reader or as a stone reader and the lower classification table is designed as a stone reading table. Furthermore, however, it is also possible to form the size classification unit from two identical sieve tables arranged one above the other (two parallel runs) or to use two or more different sieve tables one above the other. In addition, the classification tables are preferably arranged parallel to one another in the same classification unit.

The invention further comprises a method for dry grinding preparation of a product stream from grain-like foods and feedstuffs, such as cereals, namely for cleaning, separating in different fractions and, preferably for reading out foreign material such as sand, stones, clumps, etc., the product stream using

Vibrating resp. Air forces are promoted via at least one size classification (screening) and then via at least one weight classification (stone reading, light grain reading). According to the invention, the product stream is without from entry into the size classification Constriction (spread out like a carpet) until the fraction that has been read out emerges from the respective classification unit, at the latest from the gravity classification unit.

The flow direction and the inclination direction of the size classification unit are preferably selected in the opposite direction to the flow direction and the inclination direction of the gravity classification unit.

However, the new invention not only allows a very strong further concentration of the work functions while maintaining controllability, but also an optimization of the individual process steps, since the next work step before the previous one takes advantage of the extensive handover. A product transfer by means of a short free fall as a product veil or carpet also helps to loosen up the good parts, so that parts that stick together are released again.

Brief description of the drawing

Fig. 1 shows the basic structure of a solution according to the

Invention;

FIG. 2 essentially shows the structure according to FIG. 1, however, combined with an aspiration stage;

FIG. 3 essentially shows a solution corresponding to FIG. 2, but with recirculation mode and an additional separator; FIG. 4 essentially shows a solution according to FIG. 1, but with two stone reading tables arranged one above the other and a parallel run for the screening;

FIG. 5 shows a further embodiment variant for the weight classification with an upper concentrator or. Light grain reader and a lower stone reading table.

WAYS OF CARRYING OUT THE INVENTION:

The invention will now be explained in more detail with reference to the drawing using the exemplary embodiments shown there:

In the following, reference is now made to FIG. 1. The entire system consists of a compact machine which contains a screening device 2 as a size classifying unit and a concentrator 3 and a stone reader 4 as a weight classifying unit. An arrow 5 symbolizes a vibration exciter. Whose direction of oscillation is aligned at an angle to both the sieve device 2 and the concentrator 3 and the stone reader 4 in accordance with the setting angle o to the horizontal plane of gravity 6. The direction of oscillation is simultaneously parallel to the plane of the drawing in FIG. 1 or parallel to the main product flow direction. The machine 1 is supported on vibration bearings 7 via a frame 8 on the floor 9. A product feed line 10 is attached above the screening device 2 and is fixedly connected to the non-vibrating ceiling 12 via a suspension 11. Between the product feed line 10 and the screening device 2 there is a flexible one Cuff 13 attached, which serves as a transition from the non-vibrating parts of the machine 1 to the vibrating parts. The area of product entry into the screen box 2 is designed as a distribution box 14, so that the product stream bundled in the tube in the product feed line 10 is spread out as a fluffy, uniform product carpet on the top screen layer or the coarse screen 15. The coarse sieve 15 preferably serves to remove coarse additives and disruptive, large foreign bodies, such as cords, pieces of wood, etc., which are removed from the product stream via an outlet 16. The space above the coarse screen 15 is completely closed off from the outside by a sheet metal casing 17, so that no dust escapes to the outside and also no dust

Air exchange takes place. At a distance below the coarse sieve 15 there is a selection sieve 18. This has a relatively fine sieve mesh in order to obtain fine constituents such as fine sand, grain fragments, etc. as sieve diarrhea. The sieve diarrhea is led away via a closed, essentially air-impermeable bottom 19 and a sand outlet 20 adjoining it, ie it is separated from the product stream. The screen rejection from the reading screen 18 flows directly over the entire table width through a discharge channel 21 and continues to be distributed evenly over the entire width onto the concentrator 3 through which the air flows heavily. The discharge from the reading screen 18 and the subsequent reversal of the flow direction for the main product stream in the fluidized bed - or fluidized bed on the 'concentrator 3 has a double function. On the one hand, the product parts are loosened, for example dirt or shell parts only slightly adhering to a grain, which facilitates the subsequent division into fractions. The other advantageous function is that - unlike previously - the product carpet is retained in its entirety, but the significantly different physical effects or forces required for the respective treatment of the product carpet sections before and after the transfer point can still be used in full:

- in front of the transfer point in a product layer on a non-air flow _. Screen area (selection screen 18)

- After the transfer point in a classic fluidized bed with high air flow (concentrator 3).

On the non-air-flowed screen surface there are pure mechanical impact forces from particle to particle. The vibrated product layer, similar to the process of concrete vibration, looks for the greatest possible bulk density, the smallest parts immediately having a tendency to move into the cavities in the bottom layer of larger grains. However, since the sieve bottom is permeable to the small particles, they fall through and are screened off. Large parts, including large parts, strive for the surface of the product layer. The main forces or effects that are used on the sieve result from the different size of the particles.

In contrast, the air forces are used as the main forces in the fluidized bed. Accordingly, a very stressed stratification takes place within the fluidized bed according to the gravity. Grain grains move within a fluidized bed upwards, stones downwards, provided similar sizes.

Due to the vertical discharge from the selection screen 18 onto the concentrator 3 and the reversal of the flow direction, the shifting from the pure shake seal into a fluidized bed stratification takes place quickly, i.e. on a very short distance instead. Neither short-term increases in output nor fluctuations in throughput have a negative influence on the quality of the shifting, even within relatively large limits. This is an essential point of the surprising success of the new invention.

As can easily be seen from FIG. 1, the fork-like (or V-shaped) arrangement of sieve device 2 and concentrator 3 creates an expanding space 22 which is connected to an aspiration line 24 via a suction connection 23. The desired amount of air for the operation of the machine 1 can be set by an adjusting flap 25. The expanding space 22 is divided into sections 22 ', 22 *' by at least one wall 26. This allows throttle valves 27 and 28 in one or the other sector 22 'or 22' 'to adjust more or less large air flows as required (either in the upper or in the lower part of the fluidized bed). A flexible sleeve 29 is in turn attached between the suction nozzle 23 and the aspiration line 24.

The 'Concentrator 3' has the task of layering the product stream and concentrating the specifically heavy parts in the area immediately above its table surface. Shortly before the lower end of the 'concentrator table surface, which is air-permeable up to this point, but is impermeable to the product, there is a section 30 with large product openings. Through this section, the lower layer, enriched with the heavy parts, in particular with stones, is drained directly onto a slide 31 extending underneath and from there onto a central area of the stone reader 4. With an adjustable product storage bar 32, the percentages of the product flow - portion of the gravity concentrate on stone reader 4 and portion of the light fraction - can be determined according to the particular task. The fraction of the light fraction is fed directly to a corresponding outlet 33. It is still possible to add a medium-weight fraction via the additional diarrhea openings symbolized by arrow 34 at the very bottom of the 'concentrator 3' to an outlet 35 for the heavy goods, that is to say to the good, heavy 'particles.

The stone reader 4 has a rough surface, usually a mesh. The heaviest parts lying directly on the table surface of the stone reader 4 are conveyed to the upper left end of the table by the rough table surface and the throwing vibrations of the vibration exciter and then fed to a stone outlet 36. In contrast to the stone reader 4, the concentrator 3 has a table with a smooth surface (sheet with one perforation), so that the

In spite of its vibration identical to the stone reader 4, the concentrator table surface only exerts a conveying effect on the heavy product layer closest to the table surface. Due to the fluidized bed effect, the product flows downward like a liquid. The one 'Concentrator 3 and the rock reader 4 common vibration direction is also correct for the screening device 2. The product is conveyed downwards by the vibration of the sieve table surface.

This shows that all three 'classifying units, that is to say the screening device 2, the' concentrator 3 and the stone reader 4, can be provided as one oscillating unit with the same oscillating drive 5 and nevertheless each work process can be carried out optimally. However, only the stone reader 4 and the concentrator 3 are aerated with the same air.

All three machine parts 2, 3 and 4 are in accordance with the

Invention arranged directly one above the other. By fully utilizing the many combinatorial effects of the invention, the entire machine 1 is only about man-height, so it can be installed in any room of normal height. The experts involved judge the surprisingly successful interplay between the screening device 2 and the concentrator unit 3 as particularly advantageous.

However, the invention permits further design ideas.

2, the embodiment of machine 1 shown in FIG. 1 can also be used in combination with a vertical aspiration channel 40. In the widening space 22, the wall 26 is preferably designed to be adjustable, so that both the air volume distribution on the concentrator surface is set within certain limits, but in particular the air required in the aspiration channel 40 is set separately by means of a throttle 41 can. The amount of air that is extracted from the higher part of the room 22 can be adjusted by a control flap 42.

In the solutions according to FIGS. 1 and 2, the bottom of the stone reader 4 is permeable to air, so that the air can flow in and through the stone reading table freely from below. Both solutions work in the so-called suction mode, which is also a very big advantage for easy control of the air flows.

The solution of FIG. 3 has the structural elements of the solution according to FIG. 2, but is further developed in a basic function. It enables machine 1 to be operated completely with circulating air and has a light-weight separator for this purpose.

The exhaust air from the aspiration channel 40 is led directly into a circular section 50. In the rotary cutter, dust and shell parts are separated from the air with a very high degree of separation and can be discharged via a dust lock 51. The working air is fed back into the classifying section through an anal 52 and a return line 53. For this purpose, the space below the stone reader 4 is completely closed to the outside by an air distribution box 54. The air distribution box 54 is part of the vibrating unit and is connected to the return line 53 via a flexible sleeve 55. The stone reader is constructed in the sandwich construction known per se, which at the bottom has a plate 56 with very fine perforations, so that there is a guarantee of good air distribution on the table surface of the stone reader 4. If there is no aspiration system available, the machine can also be assigned a small filter (not shown) behind an extraction nozzle 61. With a fan 58, which is preferably arranged after the rotary cutter 50, the desired pressure distribution in the system can be regulated via corresponding air flaps 59 and 60, as indicated by the + and - signs in circles as symbolic pressure values.

If the machine 1 is not to be operated with circulating air, the corresponding parts are not required. The round cutter 50 can nevertheless be used, and the exhaust air can be sucked off, for example, by means of an aspiration system (not shown) via the suction nozzle 61.

4 shows a very particularly advantageous combination of the new invention. For the size classification, two parallel sieve runs 70 and 71 are provided, the sieve diarrhea (very fine sand and grain fragments) via the outlets 16 and. 20 are led away from the corresponding closed floors.

For the classification, especially for the

Stone selection, two stone selection table surfaces 72, 73 are provided, each of which has a good support in the form of a mesh. The swinging movement gives the directly on the upper resp. lower table surface 72, 73 heavy goods lying on top have a strong conveying effect after the higher table end. The light material is lifted from the two table surfaces by the strong, evenly distributed air flow, floats in the direction of the lower table ends and is discharged via the outlets 33 or. 35 carried out. It is interesting now that on the upper of the two stone reading tables 72, 73 a heavy fraction, e.g. For example, 30 to 60% of the total amount of goods flows under an inlet plate 74, and from there flows into a transfer point 75, in order to then fall directly onto the lower table surface 73. The upper table surface 72 only produces a mixture with all heavy goods, which, for. For example, as 50% of the total amount is transferred to the lower table near the upper end of the table. Experts' concerns that feeding the goods close to the upper table end of the gravity classification automatically leads to poor stone selection could be refuted by tests. It is shown that the very strong stratified flow indicated by circulation lines 76 achieves a stone selection quality which has hitherto hardly been achieved. In the area near the table there is a strong upward flow, but above that a strong downward flow.

The actual stone secretion takes place only between the lower table surface 73 and a guide plate 77 provided above the upper end of this table. Because of the air flow in this area which runs counter to the movement of material, the stones are transferred here with only a small fraction of the grain and are finally discharged through the rubber hose lock 36.

A particularly great advantage of the embodiment variant according to FIG. 4 is that the throughput through the different process zones can be adapted very precisely to the specific requirements of the individual machine parts. Since all tables have roughly the same working area, the screen area is doubled and the actual stone reading area doubled, as the lowest one Table area only receives a subset of the total. This allows a very high screening and stone selection quality with high product throughput.

5 shows a further advantageous idea compared to FIG. 1. The lowest table surface is used for stone selection. An overlying table 81 has a slightly less rough table surface, so that a part of the stones can be conveyed upwards with a small amount of grain and fall directly onto the stone reading table 4 via a passage opening 80. The upper table 81 of the weight classification primarily serves as a shift table and has a "good swamp" 82 in the lower part, i.e. a trough-shaped depression, in which the entire heavy goods (heavy grains) collect together with the stones. The gravity fraction from the manure sump 82 is discharged through the bottom openings 30 and fed to the stone reading table 4 via the chute 31.

The great advantage of this variant lies in addition to the very high stone selection quality here, in a very good separation, e.g. For example, in a heavy grain that is discharged through the outlet 35 and in a light cereal that is discharged through the outlet 33.

Overall, the invention encompasses both a method and a machine (1) for the dry cleaning of grain-type foods and animal feed, such as cereals. The separation of the goods to be cleaned into the different

Fractions carried out in a single vibration group. This has an upper size classification (2), which can consist of any sieve combination (15, 18; 70, 71), preferably has a closed lower floor and directly above a weight classification (3,4; 72,73; 81) is arranged, preferably in such a way that the two classification units are forked or. Are arranged in a V-shape. The weight classification (3, 4; 72, 73; 81) can also be combined in different variants, for example as a single or double layer table, as an upper layer and lower stone reading table. The fork-shaped space (22) is used to guide the air for the heavy class tables. An essential idea is that the goods to be cleaned from entering the

Machine 1 is guided flatly to exit without interruption in the manner of a spread textile web and is transferred from machine part to machine part (classifying unit to classifying unit). In contrast to the concept of the known cleaning systems or systems for dry grinding preparation, which are constructed from individual machines, a single compact machine without bundling of goods is provided according to the invention.

Claims

1. Plant for the dry preparation of granular food and feed, namely for

Cleaning, separating into different fractions and in particular reading out foreign material such as sand, stones, rolls, etc., with a) a size classification unit (2) (e.g. sieve (15, 18;

70,71)) b) a gravity classifier (e.g. stone reader (4;

72.73) due to the fact that c) the size classification unit (2) and the severity classification unit c.l) form an oscillation group and c.2) fork or V-shaped one above the other, so that between them a fork or. V-shaped space (22) arises, d) means for transferring the product flow in the manner of a product carpet or veil falling from the size classification unit (2) to the weight classification unit underneath, and e) means for generating an air flow through the fork or. V-shaped space (22), but not through the size classification unit (2).

2. Machine according to claim 1, characterized in that the means for generating air flow have a bottom classifying the size classification unit (2) below.

3. Machine according to one of the preceding claims, characterized in that the vibrating group has a vibratory drive (5) common to the size classifying unit (2) and the severity classifying unit.

4. Machine according to one of the preceding claims, characterized in that the gravity classification unit consists of two stacking tables arranged one above the other and through which the same air flows.

5. Machine according to one of the preceding claims, characterized in that the upper classification table as a concentrator (3; 81) respectively. Light grain reader or as a stone reader (72) and the lower classification table as a stone reading table (4; 73).

6. Machine according to one of the preceding claims, characterized in that the size classification unit (2) consists of two identical sieve tables arranged one above the other (two parallel runs (70, 71)).

Machine according to one of the preceding claims, characterized in that the classifying tables are arranged parallel to one another in the same classifying unit.

8. Machine according to one of the preceding claims, characterized in that the oscillating drive (5) is arranged on both sides, for example on a horizontal plane of gravity (6) of the entire oscillating group, in such a way that a throwing oscillation with upward component for the heavy-duty classification tables and with a downward component for the size-classification tables.

9. Machine according to one of the preceding claims, characterized in that the means for air flow generation have a suction fan which is connected to the extended side of the space (22) located between the closed floor and the gravity classification table.

10. Machine according to claim 9, characterized in that the aspiration space (22) widening to one side is divided into at least one upper (22 '') and one lower (22 ') extraction chamber and each extraction chamber (22 *', 22 ') adjustable air throttles (27, 28) are assigned.

11 • Machine according to claims 9 or 10, characterized in that the lower end of the 'concentrator table for reading a light fraction from the repulsion of the' concentrator deck opens directly into a vertical aspiration channel (40).

12. Machine according to one of the preceding claims, characterized in that the space widening to one side (22) has an air extraction system which, via a dust cutter (50, 51), the air in recirculation mode back to the suction side of the

Stone reader (4) leads.

13. Process for dry grinding preparation of a product stream of granular food and feed, such as grain, namely for cleaning, separating 1 in different fractions and in particular reading foreign material, such as sand, stones, rolls, etc., in which the product flow by means of vibrating or. 5 air forces over at least one size classification

(Screening) and then conveyed via at least one weight classification (stone reading, Leichtkornaus¬ reading), characterized in that 0 the product flow from entry into the size classification (2) without constriction (carpet-like area-spread) until the exit of the respectively read out Fraction from the respective classification unit, at the latest from the severity classification 5.

14. The method according to claim 13, characterized in that the flow direction and the inclination direction of the size classification (2) opposite the flow direction and 0 inclination direction of the gravity classification is selected.

5

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