EP0268703A1 - Sieve-walled press for pressing a fibrous material containing a fluid - Google Patents

Abstract

The press is particularly intended for draining extracted sugar beet chips. It has a preferably horizontal sieve wall (3) with associated filling shaft (9) and is equipped as a ram-type press having displacement rams (1 and 2 respectively) which are held in the two end regions of the sieve wall and can be driven separately. The one displacement ram is designed as filling ram (1) matched to the inner cross-section of the sieve wall, whereas the other, as pressing ram (2), has an end section (2a) dimensioned to be smaller than the sieve wall in cross-section and a section (2b) tapering from the end section (2a) towards the filling ram, forming an annular discharge opening (12). The filling ram (1) and the displacement ram (2) are equipped with drives, which can be actuated separately, in the form of piston-cylinder arrangements (6 and 7 respectively) (Fig. 1). <IMAGE>

Description

The invention relates to a screen jacket press for squeezing liquid-containing fibrous material to be pressed, in particular for dewatering extracted sugar beet pulp, with a screen jacket preferably arranged in a lying position and in the region of the one end opening in the screen jacket, a drivable pressing and conveying element guided in the screen jacket and one discharge opening provided at the other end of the sieve jacket and liquid collecting container arranged under the sieve jacket.

Presses of the aforementioned type are known (book "Technologie des Zuckers", Ferdinand Schneider, Verlag M.u.H. Schaper, Hanover, 2nd edition 1968, pages 222 to 227).

These screen jacket presses are designed as spindle presses, ie one or two helical press spindles are provided in the screen jacket as drivable pressing and conveying elements. When pressing this Known screen jacket presses compress the helical press spindles during their rotational movement by pressing between the helical gears and the screen jacket. The pressing pressure of such presses is essentially dependent on the internal friction angle of the material to be pressed. As a result, the pressing pressure is limited to relatively low values for pressed goods with low internal friction, such as, for example, extracted sugar beet chips, so that the degree of pressing and thus the increase in the dry matter content of the pressed material is likewise correspondingly low.

In addition, with one and the same material to be pressed, different internal friction conditions lead to correspondingly different pressing results.

Finally, the pressing time is limited to relatively small values by the necessary spindle speed and the press length.

The invention has for its object to design a screen jacket press of the type mentioned in such a way that a largely independent of the internal friction conditions of the material to be pressed, the pressure setting and a freely selectable setting of the pressing times is possible in order to achieve higher pressures and thus greater dry matter contents.

To solve the above problem, the screen jacket press mentioned in the introduction is characterized in that the press is designed as a piston press with separately driven displacer pistons held in the two end regions of the screen jacket, one of which is a filling piston adapted to the inner cross section of the screen jacket and the other as a press are designed piston, wherein the plunger to form an annular discharge opening has an end section with a smaller cross section than the screen jacket and a tapering section in the direction of the filling piston.

The separately driven two pistons, which perform different tasks, can be used to convey the wet material to be pressed through the filling shaft into the sieve jacket in the direction of the pressure piston and to press it against the material already in the press chamber. During this filling process, the newly introduced material is pre-dewatered by the pressure that builds up.

However, the actual dewatering is effected by the plunger opposite the filling plunger, which, like the filling plunger, can be driven back and forth and leads to a very considerable build-up of pressure in the pressing material during its respective insertion movement into the pressing material with a pressing chamber that is otherwise closed, while simultaneously building up the material to be pressed also causes a transverse movement of the material in the region of the tapered section of the plunger. Thus, during the pressing process, the insertion movement of the plunger simultaneously reduces the volume of the material to be pressed with a slight transverse movement, through which the drainage capability or the creation of new drainage paths is improved.

The pressure generated by the plunger in the screen jacket can be maintained over any period of time before moving together by moving the column of material located in the screen jacket is moved with the plunger in the ejection direction in order to discharge the material to be pressed located in the area of the annular gap between the plunger and the screen jacket.

The drive forces required to actuate the filling and plunger pistons are significantly lower than the drive forces for screw presses. In spite of the high pressing pressure which is generated with the new screen jacket press, destruction of the material to be pressed by grinding or by a flexing movement is avoided, so that the new press is particularly suitable for extracted sugar beet chips which tend to increase the formation of musts when pressed by means of screw presses.

Experience has shown that screw presses, for example, can be used to extract extracted sugar beet chips up to approx. 30% dry matter, while values of up to 40% dry matter can be achieved with the object of application. This increased dry matter content is of particular importance if the pressed material subsequently has to be subjected to a thermal drying treatment, for which very considerable amounts of energy are required.

It is particularly expedient if the tapering section of the plunger is conical or pyramid-shaped. The length of the tapered section of the plunger can be chosen so that it extends into the vicinity of the plunger in its inserted position.

The two displacement pistons are expediently connected to separate piston-cylinder drives, it being favorable if the one connected to the plunger Drive is equipped with a pressure relief valve that can be switched on and off. As a result, the column of material and the plunger can be displaced for the purpose of discharging the pressed-out material, but the plunger remains loaded with an ejection back pressure during the ejection movement.

It has proven to be particularly expedient if the two displacement pistons are hollow and their walls which interact with the material to be pressed are designed as sieve walls. This enables an additional discharge of the liquid from the pressed material. In the area of the conical section of the plunger, a reduction in the path of the liquid from the material to be pressed is achieved at the same time, thereby reducing the necessary pressing time.

In a further expedient embodiment, the screen jacket is designed to be flared in the direction from the filling piston to the pressing piston. This achieves a reduction in the filling pressure required to push the cake and the plunger further.

Due to the further design described in claim 6, at the beginning of the return of the filling piston, a secure closure of the pressing chamber against uncontrolled movements of the pressing material can be achieved by the filling piston transferring the newly supplied material back into the actual pressing chamber.

In order to avoid an unwanted discharge of material during the movement of the filling piston or the plunger in its insertion direction, an annular check valve can optionally be closed in the region of the discharge end of the screen jacket and releasing the annular gap between the plunger and the screen jacket can be provided.

The embodiment described according to claim 8 is used to achieve extremely long pressing times, only a single filling piston with associated drive device being required for the filling.

The process steps for pressing liquid-containing fibrous pressed material by means of the new screen jacket press are specified in claim 9 in detail.

The drawing shows exemplary embodiments of the invention in a purely schematic representation.

• Fig. 1 einen Längsschnitt durch eine Siebmantelpresse gemäß der Erfindung,
• die Fig. 2 bis 5 in weiter vereinfachten Darstellungen die verschiedenen Positionen des Füll- und Preßkolbens während eines Preßzyklus,
• Fig. 6 einen Längsschnitt durch eine um eine Längs­achse rotierbare Anordnung mit mehreren Sieb­mantelpressen,
• Fig. 6a eine Stirnansicht in Richtung der Schnitt­ebene VI-VI der Anordnung nach Fig. 6.

Show it:

• 1 shows a longitudinal section through a screen jacket press according to the invention,
• 2 to 5 in further simplified representations the different positions of the filling and plunger during a press cycle,
• 6 shows a longitudinal section through an arrangement rotatable about a longitudinal axis with a plurality of screen jacket presses,
• 6a shows an end view in the direction of the sectional plane VI-VI of the arrangement according to FIG. 6.

1 shows a filling piston 1 in the left part and a displacement piston 2 in the right part, which extend from opposite ends into a pressure-stable screen jacket 3.

The filling piston 1 is adapted in its cross section to the inner cross section of the screen jacket 3. In the example shown, the filling piston 1 is in the starting position in a section 3a of the Siebman 3 included, which is not designed as a sieve, but has a closed, imperforate wall. The cross section of the screen jacket 3 is round in the example shown and also in the other figures, but can also have a square, rectangular or other polygonal cross section.

The plunger 2 has an end portion 2a, which is adapted in its cross-sectional shape to the screen jacket 3, but is kept smaller compared to this, so that between the end section 2a and the screen jacket 3 an annular space 12 remains, which serves as a discharge opening for the material to be pressed.

The plunger 2 also has a section 2b which tapers from the end section 2 in the direction of the filling plunger and which is conical in the example shown and extends into the vicinity of the filling plunger 1 when it has reached its insertion position.

The section 2b of the plunger 2 can also be pyramid-shaped or polygonal in its cross-section or also have a concave or convex design.

In the example shown, the screen jacket 3 is arranged horizontally and in the region of the end in which the filling piston 1 engages in the screen jacket is equipped with a filling shaft 9 through which the material to be squeezed out is introduced into the filling shaft 3.

The filling piston 1 and the plunger 2 are with separately acting piston-cylinder drives 6 and 7 respectively connected. The cylinder of the piston-cylinder arrangement 7 of the press cylinder 2 is also equipped with a pressure relief valve 8 which can be switched on and off.

The filling piston 1 and the plunger 2 are designed as hollow pistons. Your walls interacting with the material to be pressed, i.e. the end wall of the filling piston 1 facing the material to be pressed and the walls of section 2b of the pressing piston 2 are designed as sieve walls 4 and 5 respectively. The liquid entering the plunger 2 is discharged through a discharge line 21, while an outlet opening 22 is provided in the outer end wall thereof for the liquid entering the filling piston 1 to exit.

Below the sieve jacket 3 extends over the entire length of the sieve jacket and also of section 3a, a liquid collecting container in the form of a trough 20, which is equipped with drainage openings 23 for the discharge of the press liquid reaching into the trough.

Seen in the feed direction of the filling piston 1, a periodically drivable gate valve 16, which is connected to a piston-cylinder arrangement 17 and extends through a slot 24 of the screen jacket, is arranged behind the filling shaft and, in the example, just before the end of section 2b of the pressure piston 2 3 extends so that it can be transferred transversely to the longitudinal direction of the screen jacket between a blocking position filling the cross section of the screen jacket and a position releasing this cross section.

At the end cooperating with the plunger 2 of the screen jacket 3 there is an annular shut-off valve 25 which can be transferred via a further piston-cylinder drive 19 between a position closing and releasing the discharge opening 12 formed by the annular gap.

The mode of operation of the screen jacket press according to FIG. 1 is explained below in connection with the purely schematic FIGS. 2 to 5:

2 to 5, only the filling piston 1 and the plunger 2 of the blocking slide 16 and the annular blocking valve 25 are shown in their different positions relative to one another or in the screen jacket.

2 shows the starting position of the filling piston 1, which is also shown in FIG. 1, and the plunger 2 in its inserted position with the ring valve 25 closed. In this position, the material to be pressed can pass through the filling shaft 9 into the interior of the screen jacket 3. The locking slide 16 is in the locked position. The filling piston 1 presses in the now following feed movement in the direction of the arrow shown in FIGS. 1 and 2, the wet pressed material introduced into the screen jacket in the direction of the press piston 2. In the course of the feed movement of the filling piston 1, the piston-cylinder arrangement 17, the locking slide 16 in the release position shown in FIG. 3, so that the pressure of the filling piston 1 is transferred to the material to be pressed in the screen jacket 3. The action of the filling piston 1 on the material to be pressed already results in considerable drainage of this material. During the feed movement of the filling piston 1, the piston-cylinder-on order 7 of the plunger in its position shown in Fig. 2 held with a pressure, the height of which can be changed by the setting of the pressure relief valve 8.

In the course of the further feed movement of the filling piston 1, the admission pressure of the plunger 2 is overcome, so that the plunger 2 together with the annular shut-off valve 25 is transferred into the position shown in FIG. 3. As a result of this, and also due to the further advancing movement of the filling piston into the position shown in FIG. 4, part of the pressed material located in the annular space 12 between the section 2a and the screen jacket 3 is discharged in the direction of the arrows shown in FIG. 3.

When the filling piston 1 has reached the position shown in FIG. 4, the locking slide 16 is transferred to the locking position shown in FIG. 4 and transferred to the locking position shown in FIG. 4 by means of the piston-cylinder drive 19.

The filling piston 1 now initially remains in its inserted position according to FIG. 4, while the piston-cylinder arrangement 7 now advances the pressing piston 2 in the direction of the arrow shown in FIG. 4. This advance of the plunger 2 results in a volume reduction of the space available to the material to be pressed in the press cylinder 3, combined with a radial displacement movement of the material to be pressed, so that a very high pressure is built up inside the screen jacket 3 with a small movement of the material to be pressed. In this way, with the generation of a high pressure, new drainage channels for the outflow of the liquid are created.

When the plunger 2 has reached the position shown in FIG. 5, the filling piston 1 can be returned to its starting position shown in FIG. 2. After filling new wet pressed material through the filling shaft 9 into the sieve casing 3, the movement sequence described above is repeated and as a result a gradual further conveying of the pressed material through the sieve casing 3 is repeated with each cycle until it is discharged through the annular gap 12.

In order to reduce the filling pressure required for moving the material to be pressed and the plunger, the screen jacket 3 can be slightly conically expanded in the direction of movement of the material to be pressed.

In order to achieve the longest possible pressing times, several sieve jackets 3 with associated plungers 2 can be arranged in a turret-like manner as pressing units around a common axis, of which only one unit is exposed to the filling and pressing process described in connection with FIGS. 2 to 5, while the others Units are dewatered while maintaining the pressure in the other turret stations.

An arrangement of the aforementioned type is shown schematically in FIGS. 6 and 6a.

An axis of rotation 28 connected to a drive 29 is mounted in a support frame 25. On the axis of rotation 28, turntable-like support disks 26 and 27 are arranged, which receive press cylinders 3 arranged revolver-like around the axis of rotation 28 with press pistons 2 associated therewith and drives 7 connected therewith, and the annular blocking valves 25 interacting with the press piston and the screen jacket.

In the embodiment shown, a total of eight screen jackets 3 are held in the support disks 26 and 27, as can be seen in FIG. 6a.

Only the screen casing 3, which is in the upper position, is located in the station in which the supply of new filling material and the pressing of this material takes place by the advance of the plunger 2. In all other stations of the press jackets 3, drainage takes place over time while maintaining the press pressure.

It can be seen that in this arrangement only a filling piston with an associated filling section 3a of the screen jacket and a filling shaft 9 are required, just as only one liquid collecting container in the form of a collecting channel 20 is necessary for the entire arrangement.

Claims (9)

1. Sieve jacket press for pressing off fibrous pressed material containing liquid, in particular for dewatering extracted sugar beet chips, with a sieve jacket (3) preferably arranged in a lying position, and in the area of one end of the filling duct (9) opening out in the sieve jacket, a drivable pressing device guided in the sieve jacket and conveying element and a discharge opening provided at the other end of the sieve jacket and a liquid collecting container (20) arranged under the sieve jacket, characterized in that the press is designed as a piston press with separately drivable displacement pistons (1; 2) held in the two end regions of the sieve jacket one of which is designed as a filling piston (1) adapted to the inner cross section of the screen jacket and the other as a press piston (2), the press piston forming an annular discharge opening (12) having an end section (2a) with a smaller cross section than the screen jacket and one yourself from this em in the direction towards the filling piston tapering section (2b). 2. Press according to claim 1, characterized in that the tapered section (2b) of the plunger (2) is conical or pyramidal. 3. Press according to claim 1 or 2, characterized in that the two displacement pistons (1; 2) are connected to separate piston-cylinder drives (6; 7), and that the drive (7) connected to the plunger (2) is equipped with a pressure relief valve (8) that can be switched on and off. 4. Press according to one of claims 1 to 3, characterized in that the two displacement pistons (1; 2) are hollow and their walls interacting with the material to be pressed are designed as screen walls (4; 5). 5. Press according to one of claims 1 to 4, characterized in that the screen jacket (3) in the direction from the filling piston (1) to the plunger (2) is flared. 6. Press according to one of claims 1 to 5, characterized in that seen in the feed direction of the filling piston (1) behind the filling shaft (9) and outside the stroke of the filling piston, a periodically driven locking slide (16) is provided, which through a slot ( 24) transversely to the longitudinal direction of the screen jacket (3) between a blocking position filling the cross section of the screen jacket and a position releasing this cross section. 7. Press according to one of claims 1 to 6, characterized in that the cooperating with the plunger (2) end of the screen jacket (3) has an annular discharge opening (12) between the plunger and the screen Sheath periodically closing or releasing, drivable, annular check valve (25) is provided. 8. Press according to one of the preceding claims, characterized in that a plurality of screen jackets (3), each having a plunger (2) and associated drive (7) in the longitudinal direction parallel to each other about a common axis (28) rotatable in a support frame (25) are arranged, and that a cylinder section (3a) cooperating with all press cylinders is held in the support frame with the filling shaft (9) and filling piston (1) guided in this section. 9. A method for squeezing liquid-containing fibrous material to be pressed, in particular for dewatering extracted sugar beet chips with a screen jacket press according to one of claims 1 to 8, characterized in that the material to be pressed is pressed by means of the filling piston in the direction against the plunger held in its insertion position with a form is that the material to be pressed is moved through the filling piston while overcoming the pre-pressure of the pressing piston with the latter in the feed direction of the filling piston and the pressed material is discharged from the annular discharge opening between the pressing piston and the pressing cylinder, and that subsequently the pressing piston against the pressing material held in the pre-pressed state Direction against the filling piston to generate the full pressure in the material to be pressed.

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