DE10003911A1 - Operating fine filter machine involves passing fluid, especially gas, through entire filter surface in alternating directions with defined range of ratio of fluid flow speeds in both directions - Google Patents

Abstract

The method involves passing a fluid, especially a gas, through the entire filter surface in alternating directions and the ratio of the fluid flow speeds in both directions is less than or equal to 5 and greater than or equal to 0.2. The frequency of alternation the flow direction is greater than or equal to 3 Hertz and the filter zones (3) of the filter surface are deformed by the fluid flow. Independent claims are also included for the following: a fine filter machine.

Description

The invention relates to a method for operating a Fine screening machine and a fine screening machine for Application of the procedure.

Fine screening machines are used for precise classification finely dispersed substances in the grain size range from 0.025 to 1 mm inserted. Step with decreasing grain size here two problems:

The specific screening performance decreases disproportionately and grains sticking together form agglomerates, which affects the selectivity.

The cause is that of the third power of the grain size dependent mass force and that of the first power dependent adhesion of the grains of the screened material.  

As the grain size becomes finer, the Adhesive force. Depending on the type of fabric, grain shape and Humidity is the balance of adhesive and Mass force between 1 and 0.1 mm. So it is not possible, smaller grains from the screenings quickly enough cut off. In particular grains smaller than 0.05 mm also stick to the sieve bottom and block the Stitches. Therefore, sifters are increasingly considered Alternative to screening machines used. Their disadvantage again there is inevitable spray grain in the fine material. The manufacture of an often required spray-free The product therefore still requires use sieving.

In the simplest case, to counter the problem the classic, mechanical screening all over An air flow can be superimposed on the sieve surface. It is but only sensible, a pressure difference less than approx. 1 mm WS should be used, otherwise the material to be screened is on the screen is pressed and loses its mobility. For this reason, this possibility becomes little Made use of.

The most common version of pneumatic screening machines is air jet screens. They are mostly used as test sieves in the grain size range from 1 to 0.01 mm (cf. DE 873 647). The use as a production sieve is also known (Aufaufaufung-Technik 29 ( 1988 ), 265-272, Chemie-Technik No. 4, ( 1991 )). What is essential here is a narrow slot nozzle, which is moved parallel to the screen surface at a short distance and from which the fluid flows against and through the screen at a speed of 50 to 150 m / s. Several such nozzles can also be present. Around or between these nozzles, the fluid flows in the opposite direction into the fine material space at a speed of approx. 1 m / s, ie at only approx. 1% of the nozzle speed. Because of the small slot width of 1 to 5 mm, the distance to the sieve must be about the same size so that the jet does not expand as much. However, this occasionally leads to streaking and damage to the sieve. Another disadvantage is the effect of the fluid jet loaded with fine material as a sandblasting blower, which can also damage fine screen mesh. A further disadvantage is that the dynamic pressure of the fluid jet is far from sufficient to free the clamping grain from the mesh. Finally, the finest grain causes the meshes to blow away as a result of adhesive forces.

Based on this state of the art Invention the task of a pneumatic To design and fine-tune the fine screen machine operate that the specific screening performance with decreasing mesh size decreases only slightly Selectivity and the deagglomeration of the screenings is satisfactory, damage to the fine Screen fabric is avoided, and in particular none Laying the stitches by clamping grain as well as by Blowing away occurs.

According to the invention, the task is procedural solved in that the entire screen area of one Fluid, especially gas, in alternating directions is flowed through, and that the ratio of Fluid flow rates in the two Directions less than or equal to 5 and greater than or equal to 0.2 is observed.

This procedural measure will Task essentially completely solved. On Ratio of the flow velocities of the two Directions that are less than 5 or greater than 0.2, allows flow against the screen Fluid flows in about an order of magnitude slower  leave than usual with the known solutions. Thereby the sandblasting effect is avoided and it also occurs no stitches blowing away.

It is preferably provided that the frequency of the Alternating flow directions greater than or equal to 3 Hertz is observed.

This measure ensures a high sieving capacity reached because otherwise the sieve is already would lay coarse material in a mono-grain layer.

It is also preferably provided that Flow through the screen area of the screen zones Screen surface to be deformed.

It is preferably provided that the screen zones of the Screen area alternating on both sides of the Screen surface to be bent.

The corresponding deformation of the screen surface of the Sieve zones loosen the grit from the sieve meshes and cleans the wires or the like from the screen surface any adhesive grain. This deformation takes place sagging on both sides of the screen surface, see above  the cleaning effect increases.

A fine screen machine to apply the method according to one of claims 1 to 4 is characterized that the sieve surface is made of plastic.

A sieve surface, which consists of plastic, has lower compared to metallic screen surfaces Modulus of elasticity and is therefore lighter malleable as metal. Wear resistance too is higher.

It is also preferably provided that the screen surface has several screening zones.

It can preferably be provided that the Screening zones one behind the other in the conveying direction and / or are arranged side by side.

It may also be preferred that the sieve zones approximately are equal in area.

It may also be preferred that the sieve zones are the same Have mesh size.  

Alternatively, it can be provided that the screening zones have different mesh sizes.

A screen surface that consists of several screen zones, allows different classification at the same time composite screenings and thus an increase throughput and selectivity. Behind each other arranged screening zones lead to a Cascade connection, which leads to the desired behavior of an ideal tubular reactor can be realized. Screen zones arranged side by side increase the Sieving performance or throughput. Screen areas of equal area allow use standardized components. Screen areas of various Mesh sizes allow the adjustment of the Separation process to the grain composition of the Good tasks with regard to sieving performance.

It is also preferably provided that the screen surface is attached to a frame.

It may be preferred that the screen surface on Frame is clamped or glued.  

It can also be preferred that the screen surface between or attached to strips that are part of a Are removable frames.

It is also preferred that the strips are toothed or have wavy or soft end faces.

Fastening the screen surface by clamping and gluing are cheap training courses to connect the Screen area with the fine screening machine. It is advantageous an attachment between or on strips. Are the Last part of a removable frame, so is a change of the sieve surfaces easily by covering Removable frames can be exchanged. Toothed or corrugated end faces of the strips realize a greater length of the screen area than that of the associated Sieving zone and thus an enlargement respectively Deflection which results in better cleaning results.

In addition, it is preferably provided that the edge of the Screen area reinforced at the area of the bar arrangement, shrunk or rubberized.  

Reinforcing, shrinking and / or gumming the Siebrandes in the area of the last increases the Fatigue strength of the screen surface.

Furthermore, it is preferably provided that Flow deflection devices are provided by means of which is a fluid in alternating direction through the Screen surface is guided.

It may be preferred that the Flow deflection devices as flap sliders, Nozzles or fluidic switching elements are formed.

It may also be preferred that the Flow deflection devices relative to the standing Screen surface are movable.

It may also be preferred that the Flow deflection devices through mechanical, pneumatic, hydraulic or electromechanical Elements are movable.

It can also be provided that the Flow deflection devices are movable such that they are steady, discontinuous or inharmonic  It can also be provided that the flow deflection devices along the screen surface synchronously or are out of phase.

Flow deflection devices, designed as flaps, Slides, nozzles or fluidic switching elements are favorable training of flow deflecting device exercises. Flow deflection devices that are relative to the standing sieve surface are one constructive solution for changing the direction of Flow through the sieve zones. Mechanical, pneumatic, hydraulic or electromechanical Elements are useful drive elements for Flow deflection devices. A steady movement the drive elements result in a smooth run. An inconsistent or inharmonic movement of the Drive elements reduce dead time when turning the current. Synchronous movement of the switching elements simplifies control but causes Vibrations of the fine screening machine. Phase shifted Movement is more complicated for the transportation of coarse goods, but leads to smoother running of the fine screening machine.

It can preferably also be provided that the Screen area relative to standing or movable  Flow deflection device is movable.

It can be provided that the screen surface is continuous or can be moved continuously.

A screen surface that is relatively dormant Moving flow deflection devices can require simpler drive since only a single one Element to be moved. A steady movement enables easier mass balancing and realizes the transportation of the coarse goods intended speed and thus dwell time. A discontinuous movement uses the acceleration force in addition to the flow force to the screenings move.

It is also preferably provided that a device for conveying screenings and / or fluid from one Task on the screen area to one Coarse material deduction is provided.

It can be provided that the device for Convey through a fixed or adjustable Inclination of the screen surface against the horizontal is.  

It can also be provided that the conveyor is designed as an injector conveyor.

A device for conveying screenings and / or Fluid along the screen surface makes it possible Set dwell time on the screen surface, and so to bring about a sharp separation. An easy one constructive measure is the inclination of the screen surface against the horizontal. The use of an injector Conveyor enables funding on a horizontal Screen area and at the same time the deagglomeration especially fine screenings.

It can also be provided that in the area of A sluice is provided at the feed point of the screened material is.

A lock makes it possible to screen material without Abandon fluid flow.

It is preferably provided that the lock as Cell wheel lock is formed.

If the lock is designed as a cellular wheel lock, so this is a simple and reliable  constructive solution.

Furthermore, it is preferably provided that a knock screen bottom on the passage side of the screen surface is provided.

It can also be provided that the knocking sieve bottom extends parallel to the screen surface.

It can also be provided that the knocking sieve bottom a distance of about 0.5 to 5 centimeters from the Has screen area.

It can also be provided that the knocking sieve bottom has a larger mesh size than the screen area.

It can also be provided that the knocking sieve bottom is swingably movable.

It is preferably provided that on the bottom of the tapping screen Tapping body with a diameter of about 0.3 to 2 Centimeters are provided.

It is also preferred that the tapping body made of plastic or elastomer.  

A knocking sieve bottom arranged on the passage side allows the use of tapping bodies that Remove the clamping grain from the stitches. Attaching the Knocking sieve bottom parallel at a distance of preferably 0.5 to 5 cm results in favorable operating conditions. If the knocking sieve bottom carries out an oscillating movement, see above is not throwing the tapping body alone on the Instructed fluid flow. Tapping body from approx. 0.3 to 2 cm diameter lead to a good cleaning of the Stitches. Tapping body made of plastic or Made of elastomer lead to an intense Jump movement off.

In addition, it can also be preferred that in the screen space Aprons are provided and / or the drop point for the screenings at one end of the screen area and the Discharge point for the coarse material at the opposite end the screen surface is provided and / or separator for Separation of fine and / or coarse material are provided and / or a blower for the fluid with a front or Throttle valve located behind the fan is provided and / or a gravity transport of the Coarse material over the screen surface in a coarse material container is provided.  

Aprons in the screen room support this Operating behavior of a cascade of stirred tanks. Moreover equalize the transition of the screenings-fluid Mix in the next screening zone or in the coarse material discharge.

A feed point for the screenings at one and one Discharge point for the coarse material at the opposite end the screen surface ensures optimal selectivity or minimal defective grain content in the coarse material.

Separator for separating fine and / or coarse material a high flow rate from the fluid flow speed and thus screening performance.

A throttle valve in front of or behind the fluid blower enables the volume flows of the Fine and coarse goods transport fluids and in addition the use of a single blower.

Gravity transport of the coarse material over the screen surface and into a coarse container low expenditure on apparatus for collecting the Gross good.  

The invention provides a fine screening machine several in series, for example sieve zones of the same area are available alternately in the opposite direction with approximately the same Flow rate can be flowed through. The The frequency of the flow change is greater than 3 Hertz. The screen surface has shrunk or is open at the edge Toothed or corrugated strips attached to the part of a removable frame. The screen area of the Sieve zones are generally made of plastic and undergoes a deflection. The change of Flow direction provide flow deflection device tungen, as swing or rotary flaps, slide or fluidic switching elements are formed. Your Actuation is carried out by mechanical, pneumatic, hydraulic or electromechanical drives, approximated in a rectangular mode of operation or by continuous driven slide, for example roller turning slide. The change in flow can also by moving the screen surface over stationary Flow deflection devices take place. The fine goods is transported pneumatically through the screen surface and deposited in a separator. The fluid flows then by a blower. Coarse material is on Screening pneumatically or by gravity into one  Coarse goods container removed. The credit can via a rotary valve. To promote an injector conveyor can be provided along the sieve his. Instead of moving fluid guides, too stationary with moving screen surface can be used.

Embodiments of the invention are in the Drawing shown and below in more detail described. It shows:

Fig. 1 shows a longitudinal section through a fine screening;

Fig. 2 u. 3 alternative embodiment, also seen in longitudinal section, in Fig. 3 with a detail enlargement;

Figure 4 shows the longitudinal section through a further embodiment of a fine screen machine.

Fig. 5 shows a longitudinal section and two cross sections through a fine screen machine with different cut and cut variants;

Fig. 6 shows a cross section, a plan view and a developed view and partial sectional views of a fine screening;

Fig. 7 shows a longitudinal and cross section of another embodiment of a fine screening;

Fig. 8 shows a longitudinal section and cross section of a fine screen machine;

Fig. 9 shows another variant in the same view.

Fig. 1 shows a longitudinal section through a fine screen swinging flap design with a housing 1 , a screen space 2 , a screen zone 3 of the screen surface, a web 4 , a serrated or corrugated edge strip 5 , a terminal strip 6 of a removable frame, a pendulum flap 7 , a push rod 8 for actuating the pendulum flap 7 , which is articulated on the pendulum flap 7 via a joint 9 and is driven by a drive 10 . Furthermore, the pendulum flap 7 is articulated via a flap joint 11 on the housing side and on the frame side.

Fluid entry is indicated at 12 . The fine material space is indicated by 13, the fine material discharge 14 , the fine material separator 15 and a blower 16 with a throttle valve 17 . A coarse material separator 18 , a coarse material discharge 19 and an apron 20 are also provided. In addition, a tapping screen bottom 21 with tapping bodies 22 is arranged. An injector conveyor 23 is arranged for material transport. The screenings A are carried out through a rotary valve 24 . The fine material is collected in the fine material container F. The coarse material is collected in the coarse material container G. The swing angle of the swing flaps 7 is indicated by α. At 2 e and f the vibration amplitude or the vibration frequency is illustrated.

In Fig. 2 a variant of a fine screening machine is shown in longitudinal section, which is designed in a rotary flap design. Matching components have the same reference numerals. In addition, the arrangement of rotary flaps 25 is provided here, each of which is equipped with a rotary flap shaft 26 and a drive element 27 in the form of an endless belt drive. Furthermore, a cover shell 28 is arranged in the region of the rotary flaps 25 below the latter. The rotary flaps rotate about an axis that penetrates perpendicularly through the drawing plane. The cover shell 28 covers approximately the lower quarter circle of the rotary flap 25 . A blower for the coarse material is also indicated at 29.

Fig. 3 shows the longitudinal section through a fine screening machine in a fluidic switching element design. Matching components are again provided with the same reference numerals. In addition, a Coanda web is indicated at 30. A control gas nozzle is shown at 31 and a control gas supply is shown at 32. The fluid jet is illustrated by a, while the control gas jet is illustrated by b. The limit of the fluid jet is indicated by c.

Fig. 4 shows the longitudinal section through a further embodiment of a fine screening machine with rotary flap design and gravity transport. Here too, matching components are provided with the same reference numerals. A possible gas recirculation is also indicated at 33. The acceleration of gravity is shown with g.

Fig. 5 shows a longitudinal and two cross sections through a fine screening machine with flow deflecting lines, which are designed as a rotary rotary valve. Here, too, matching components are again provided with the same reference symbols. Rotary valves are indicated at 34 . The cuts CC and DD show different versions of rotary slide valves in different positions.

Fig. 6 shows a cross section, a plan view and a development and partial sections of a fine screen machine, which is designed as a circular screen. The same components are again provided with the same reference numerals. In addition, rotating arms 35 with mechanical seals 36 and a bearing 37 are shown. The supply of flushing fluid is illustrated at 38 .

FIG. 7 shows a further embodiment of a fine sieve machine in longitudinal and cross section, which has a sieve surface that moves relative to the standing (frame-fixed) flow diversion devices. Here too, the same components are provided with the same reference numerals. The sieve frame is guided in a sieve frame guide 46 and can be moved (horizontally) transversely to the plane of the drawing by means of the drive ( 8 , 9 , 10 ).

Fig. 8 shows a fine screening machine in longitudinal and cross section. Here too, the same components are provided with the same reference numerals. Here, a crank 39, balancing mass 40 , is coupled to the oscillating frame 41 . Tubular elements are shown at 42 . At 43 , an injector delivery fluid is indicated.

Fig. 9 shows a fine screening in disc rotary valve embodiments in longitudinal and transverse section and in a front view with the housing 1, the screening space 2, screening zone 3 of the screen surface, web 4, drive 10, fluid acres 12, fluid egress 13, fines separator 15, blower 16, Coarse material separator 18 , coarse material extraction 19 , disc rotary valve 44 , fluid flow 45 , screen feed A, fine material container F, coarse material container G, opening a for fluid / fine material and opening b for fine material / fluid.

A typical fine screening machine according to the invention has a screening area of 0.5 × 0.5 m, which is divided into 10 screening zones of 5 × 50 cm. The screen surface is a thermoset plastic screen with 50 µm square mesh and a length of 5.5 cm per screen zone. Two opposite edges of the screen surface are glued on toothed edge strips 5 of 1 to 2 mm tooth pitch. Alternatively, the sieve surface can also be shrunk at the edges by connecting it to an elastic, previously stretched edge strip. An approx. 5 mm wide rubber coating of the screen fabric can also be provided in this area, which also means an impregnation with an elastomer. The flow rate of air as fluid is 5 m per second based on the free cross-section. It requires a pressure difference of approx. 25 mm WS on the free screen. The back and forth flow of the sieve covered with screenings requires about 100 mm water pressure difference. Including the separator, a pressure difference of around 300 mm water is required. The frequency of the change in the flow direction is preferably 10 to 50 Hertz. Flaps ( 7 ) used for this purpose can be designed as swinging or rotating swinging flaps. Linear, disc and roller slides ( 34 ) are also suitable for this. Favorable mechanical elements for actuating the flaps or slides are cams, backdrops, Maltese crosses, elliptical or quasi-elliptical gear pairs, unbalance vibrators with harmonic synthesis for approximating a rectangular or trapezoidal vibration. Pneumatic and hydraulic elements are based on the piston or rotary piston principle, the electromechanical elements on the electromagnetic principle. Separators for fine and / or coarse material can be cyclones and / or filters.

Instead of moving flow guides, stationary flow guides with a moving screen surface can also be used. The latter carry out a reciprocating or circular plan movement, with about 1000 rpm with a vibration range of 2 to 5 cm. An unbalanced mass ( 40 ) is provided for mass balancing.

The good feed can take place via a lock, designed as a cellular wheel lock 24 . Gravity and / or pneumatic conveying, which is designed as an injector conveyor 23 , can be used to convey the material to be screened and the fluid over the screen surface.

The invention is not based on the embodiment limited, but often within the scope of the disclosure variable.  

All new, in the description and / or drawing disclosed individual and combination features regarded as essential to the invention.

Claims (36)

1. A method of operating a fine screening machine with a screen surface, characterized in that the entire screen surface is flowed through by a fluid, in particular gas, in alternating directions, and in that the ratio of the flow velocities of the fluid in the two directions is less than / equal to 5 and greater than / is equal to 0.2. 2. The method according to claim 1, characterized in that that the frequency of the change of Flow directions greater than or equal to 3 Hertz is observed. 3. The method according to claim 1, characterized in that through the flow through the sieve surface Sieve zones of the sieve surface are deformed. 4. The method according to claim 3, characterized in that the sieve zones of the sieve surface alternate to on both sides of the screen surface.   5. Fine screening machine for applying the method according to one of claims 1 to 4, characterized in that that the screen surface is made of plastic. 6. Fine screening machine for applying the method according to one of claims 1 to 4 or according to claim 5, characterized in that the screen surface has a plurality of screening zones ( 3 ). 7. Fine screening machine according to claim 6, characterized in that the screening zones ( 3 ) are arranged one behind the other and / or side by side in the conveying direction. 8. Fine screening machine according to claim 6 or 7, characterized in that the screening zones ( 3 ) are approximately the same area. 9. Fine screening machine according to one of claims 6 to 8, characterized in that the screening zones ( 3 ) have the same mesh size. 10. Fine screening machine according to one of claims 6 to 8, characterized in that the screening zones ( 3 ) have different mesh sizes. 11. Fine screening machine for applying the method according to one of claims 1 to 4 or according to one of the Claims 5 to 10, characterized in that the Screen surface is attached to a frame. 12. Fine screening machine according to claim 11, characterized characterized that the screen surface clamped to the frame or is glued. 13. Fine screening machine according to claim 11 or 12, characterized in that the screen surface is fixed between or on strips ( 5 , 6 ) which are part of an interchangeable frame. 14. Fine screening machine according to claim 13, characterized in that the strips ( 5 , 6 ) have toothed or corrugated or soft end faces. 15. Fine screening machine according to claim 13 or 14, characterized characterized in that the edge of the screen surface on Reinforced, shrunk area of the strip arrangement or is rubberized. 16. Fine screening machine for applying the method according to one of claims 1 to 4 or according to one of the  Claims 5 to 15, characterized in that Flow deflection devices are provided by means of which a fluid in an alternating direction is passed through the screen surface. 17. Fine screening machine according to claim 16, characterized in that the flow deflection devices are designed as flaps ( 7 , 5 ) slide ( 34 ), nozzles or fluidic switching elements. 18. Fine screening machine according to claim 16 or 17, characterized characterized in that the flow deflection devices are movable relative to the standing screen surface. 19. Fine screening machine according to claim 18, characterized characterized in that the flow deflection devices by mechanical, pneumatic, hydraulic or electromechanical elements are movable. 20. Fine screening machine according to claim 18 or 19, characterized characterized in that the flow deflection devices are so movable that they are a steady one Carry out discontinuous or inharmonic movement. 21. Fine screening machine according to one of claims 18 to 20, characterized in that the flow deflection devices  along the screen surface synchronously or are out of phase. 22. Fine screening machine according to one of claims 16 to 21, characterized in that the screen surface relative to standing or moving Flow deflection device is movable. 23. Fine screening machine according to claim 22, characterized characterized in that the screen surface is steady or is continuously movable. 24. Fine screening machine for applying the method according to one of claims 1 to 4, or according to one of the Claims 5 to 23, characterized in that a Device for conveying screenings and / or fluid from a task to the screen area to one Coarse material deduction is provided. 25. Fine screening machine according to claim 24, characterized characterized in that the device for conveying through a fixed or adjustable Inclination of the screen surface against the horizontal is formed.   26. Fine screening machine according to claim 24 or 25, characterized in that the conveying device is designed as an injector conveyor ( 23 ). 27. Fine screening machine according to one of claims 24 to 26, characterized in that in the area of A sluice is provided at the feed point of the screened material is. 28. Fine screening machine according to claim 27, characterized in that the lock is designed as a cellular wheel lock ( 24 ). 29. Fine screening machine for applying the method according to one of claims 1 to 4 or according to one of claims 5 to 28, characterized in that a knocking screen bottom ( 21 ) is provided on the passage side of the screen surface. 30. Fine screening machine according to claim 29, characterized in that the tapping screen bottom ( 21 ) extends parallel to the screen surface. 31. Fine screening machine according to claim 30, characterized in that the tapping screen bottom ( 21 ) is at a distance of about 0.5 to 5 centimeters from the screen surface. 32. fine sieve surface according to one of claims 29 to 31, characterized in that the tapping sieve bottom ( 21 ) has a larger mesh size than the sieve surface. 33. fine sieve surface according to one of claims 29 to 32, characterized in that the knocking sieve bottom ( 21 ) is swingably movable. 34. Fine screen surface according to one of claims 29 to 33, characterized in that on the tapping screen bottom ( 21 ) tapping body ( 22 ) are provided with a diameter of about 0.3 to 2 centimeters. 35. Fine screening machine according to claim 34, characterized in that the tapping body ( 22 ) consist of plastic or elastomer. 36. Fine screening machine for applying the method according to one of claims 1 to 4, or according to one of claims 5 to 35, characterized in that aprons ( 20 ) are provided in the screening area and / or the feed point (A) for the screenings at one end the sieve surface and the extraction point ( 19 ) for the coarse material is provided at the opposite end of the sieve surface and / or separators are provided for separating fine and / or coarse material and / or a blower ( 16 ) for the fluid with one in front or behind the Throttle valve ( 17 ) arranged in the blower is provided and / or gravity transport of the coarse material is provided in a coarse material container (G) via the screen surface.