Cutting device for a pellet press, pellet press with such a cutting device for biogenic fiber-containing pellets, method for producing biogenic fiber-containing pellets and use of a pellet press

Abstract

Cutting device (13; 14; 15; 16) for a pellet press (1) with at least one cutting means (19) for biogenic fibre-containing pellets (11) and at least one fastening area (17) in which the cutting device (13; 14; 15; 16) can be fastened to a fixed housing part (2) of the pellet press (1) in such a way that the cutting means (19) can be arranged in the radially outer area of ​​a rotatably mounted annular die (4) of the pellet press (1) and at a distance therefrom, wherein the cutting means (19) has a concave, arcuate contour (21) and can be mounted in the radially outer region of the ring die (4) by means of the fastening region (17), that the cutting means (19) with its arcuate contour (21) extends substantially helically over at least the area of ​​one of the radial through-bores (5) of the annular die (4), so that a pellet (11) which projects beyond the ring die (4) in its radial direction from the through-bore (5) with a length greater than the distance between the ring die (4) and the cutting means (19) comes to rest on the cutting means (19) in the region of its free end (20) and is able to move along it in the circumferential direction in such a way that the pellet (11) is deflected by the cutting means (19) by means of a force having an axial component, so that it bends in the region of the ring die (4), characterized by that the cutting device (13; 14; 15; 16) has a base body (25) with a concave circular arc-shaped radial guide surface (26), in the region of which the cutting means (19) is arranged.

Description

[0001] The present invention relates to two alternative cutting devices for a pellet press with at least one cutting device for biogenic fiber-containing pellets, in particular wood pellets, and at least one fastening area in which the cutting device can be fastened to a fixed housing part of the pellet press in such a way that the cutting device can be arranged in the radially outer area of ​​a rotatably mounted annular die of the pellet press, which has radial through-bores, and at a distance from this.The invention further relates to a pellet press for pressing biogenic fibrous pellets, in particular wood pellets, with a rotatable annular die having substantially radial through-bores and forming a pressing chamber inside it into which biogenic fibrous pressing material can be fed, with at least one roller arranged eccentrically to the annular die and capable of rolling on its inner circumference such that the pressing material is pressed through the through-bores to form the pellets, and with at least one cutting device having a cutting means which is fastened to a stationary housing part of the pellet press such that the cutting means is arranged in the radially outer region of the rotatably mounted annular die at a distance from the latter. The invention further relates to two corresponding alternative methods for producing biogenic fibrous pellets.Furthermore, the invention relates to the use of a pellet press for producing biogenic fiber-containing pellets.

[0002] The wood processing industry generates large quantities of sawmill by-products. These primarily include sawdust, shavings, and wood chips, which are typically used to make wood pellets. A rod-shaped wood pellet, for example, has a diameter of between 4 mm and 10 mm, a length of between 5 mm and 45 mm, and a bulk density of between approximately 1.1 and 1.3 kg / dm³. 3and has an energy density of approximately 5 kWh / kg. The pellets are produced in a conventional ring, round, or flat die press, in which rollers force the material through the holes or press channels of the die. Temperatures of over 120°C and very high pressures occur, with these being highest near the walls of the press channels. As a result, the cylindrical surface of the pellets is very smooth and has a very high density.

[0003] The press channels have a conical inlet chamfer a few millimeters deep on the inlet side. A closer look at an individual press channel reveals that the compaction of the fibrous and fine chip material occurs cyclically with each pass of a roller mill. The funnel-shaped chamfer creates a funnel-shaped fiber structure in the pellets. This is why pellets have a convex front surface and a concave rear surface. A pellet die for 6 mm thick pellets with a press channel bore of, for example, 6 mm diameter has a press channel length of approximately 40 mm and widens radially outwards in steps of 20 millimeters to 6.4 mm, 6.8 mm, and 7.2 mm.The reason for this is that the pressed fiber strand must be fed further after the actual 6 mm diameter extrusion channel section, and a certain thickness of the die is necessary for material strength. The end faces of the pellets have a very irregular, rough, and brittle surface. As a result, the end faces of the pellets are primarily responsible for the creation of disruptive fine particles and dust during any handling of the pellets.

[0004] Pellets are typically blown into storage bunkers using a silo pump truck. It has been shown that the long pellets in the blowpipes "fly" through the hoses at an angle of approximately 45° against the airflow direction, almost without contact.

[0005] Long pellets have better "flying characteristics" than short pellets. Therefore, during the blowing process, the short pellets, along with the fragments, are primarily located at the bottom of the blowing hoses, where they are essentially conveyed in a rolling motion. This causes them to come into contact with the underside of the hose and collide with the hose couplings, generating further fines. Short pellets, broken pellets, and dust have significantly poorer flow characteristics than evenly long pellets.

[0006] The end faces exhibit significantly higher friction in pellet beds than the smooth cylindrical surfaces. The percentage of end faces decreases linearly with increasing average pellet length. The ideal pellet length for small pellet furnaces is approximately 25-35 mm. The maximum length of wood pellets is defined by the European standard EN 14961-2 with the formula 7.5 x D (diameter). For the 6 mm diameter pellets commonly used for small furnaces, this translates to a maximum length of 45 mm.

[0007] The cutting techniques commonly used on the market have some weaknesses in this regard. In round dies, fixed cross bars made of flat steel are arranged at a distance from the die in the radial outer area. The pellet initially grows through the press channel out of the ring die, which rotates at high speed. As soon as a pellet is long enough, it strikes one of the cross bars during its rotation and is broken off by the ring die. The cross bars, designed as flat iron, are rotated 90° to the direction of rotation of the ring die. As a result, the pellets are suddenly decelerated when they hit the cross bar vertically. The pellets are still very hot (just under 100°C), mechanically unstable and still soft. The path speed of a round die is around 7.5 m / sec.When the pellets are struck, they are strongly accelerated and set into rotation by the cross bar, which is positioned at a 90° angle to the direction of rotation.

[0008] They then strike further crosspieces or other components of the pellet press at high speed. When separated from the ring die and / or subsequently impact other components of the pellet press, the pellets break uncontrollably into pieces of varying lengths. Furthermore, a significant amount of crushed material is generated. The fines fraction produced using the conventional cutting technique for a ring die with a 6 mm hole diameter is approximately 5%-8%.

[0009] From US 2,252,900 A a pellet press according to the preamble of claim 1 is known, in which a triangular cutting means is arranged at a radial distance from the ring die, on which means pellets are continuously deflected laterally on their way in the circumferential direction of the rotating ring die until they finally shear off at the die surface and are then guided out of the pellet press in free flight.

[0010] WO 2008 / 058956 A2, US 6,299,430 B1 and US 3,017,845 A each disclose a pellet press in which the pellets are cut off with a fixed knife on the surface of the ring die.

[0011] The object of the present invention is therefore to provide a cutting device, a pellet press with a corresponding cutting device and a corresponding method by means of which pellets of the most uniform length possible can be produced with, at the same time, low broken dust production.

[0012] The problem is solved by two alternative cutting devices and a pellet press having the features of independent patent claims 1, 10 and 13. The problem is also solved by two corresponding alternative methods having the features of claims 16 and 17. The problem is further solved by a use having the features of claim 18.

[0013] The first cutting device according to the invention for a pellet press has at least one cutting device for biogenic fiber-containing pellets, in particular wood pellets. Furthermore, the cutting device comprises at least one fastening area, in which the cutting device can be fastened to a stationary housing part of the pellet press such that the cutting device can be arranged in the radially outer area of ​​a rotatably mounted annular die of the pellet press, which has radial through-bores, and at a distance from it. The cutting device has a concave, arcuate contour, in particular an inner contour. The concave, arcuate contour is preferably compressed or stretched compared to a circular arc-shaped contour. Alternatively, however, it can also be designed as a circular arc-shaped contour.The cutting-to-length means can be attached by means of the fastening region in the radially outer region of the ring die such that the cutting-to-length means, with its arcuate contour, extends essentially helically over at least one region of one of the radial through-bores of the ring die provided for this purpose. The dimensions of this region - over which the cutting-to-length means extends over at least one of the radial through-bores of the ring die - are preferably greater than or equal to the diameter of the through-bore (D) in the axial direction of the ring die and greater than or equal to D / tan α in the circumferential direction of the ring die, where α is the pitch angle of the helically extending cutting-to-length means. The cutting-to-length means therefore has at least a length L greater than or equal to D / sin α.

[0014] Due to this design and arrangement of the cutting device relative to the ring die provided for it, a pellet that protrudes beyond the ring die in its radial direction from the through-bore by a length greater than the distance between the ring die and the cutting device comes into contact with the cutting device in the region of its free end, in particular with its lateral surface. Furthermore, the pellet is initially able to move along the cutting device in the circumferential direction in such a way that the pellet is deflected by the cutting device by means of a force having an axial component, predominantly in the axial direction of the ring die, so that it bends in the region of the ring die.The pellet is therefore not braked abruptly, but guided circumferentially over a defined angular range of the ring die, which can be influenced in particular by the pitch angle of the helical cutting device. At the same time, it is increasingly deflected from its radial starting position until the pellet gently bends or is separated from the ring die. This prevents undefined breaking or cutting of the pellet into pieces of different lengths. As a result, the pellets advantageously have an essentially constant length or a length that varies within a spectrum, determined by the distance between the outer circumference of the ring die and the inner contour of the cutting device. This makes it possible to reduce the proportion of unwanted "short pellets" under 14 mm from an average of 60% to less than 10%.Furthermore, the amount of fine dust generated during separation can be reduced by up to 80%, which can lower production costs and increase throughput.

[0015] Furthermore, the separated pellets are guided in the axial direction of the ring die by means of the cutting device, which extends helically in the axial direction. This prevents the separated pellets from being thrown undefined into unintended areas of the pellet press, which could damage them or even break them into at least two shorter, undefined pieces. The cutting device is therefore shaped in such a way that the pellets are gently bent and guided in the axial direction to an ejection area of ​​the pellet press.

[0016] According to the invention, the first cutting device comprises a base body with a concave, in particular circular-arc-shaped, radial guide surface. The cutting means is arranged in the region of said base body. Preferably, the first cutting means is arranged on an inner surface of the radial guide surface facing the annular die. The cutting device is preferably arranged relative to the annular die provided for this purpose such that the annular die and the circular-arc-shaped radial guide surface are arranged concentrically to one another and / or spaced from one another, in particular by a first annular gap. For pellets already separated from the annular die as well as for pellets that have broken in the region of the through-bore of the annular die, the circular-arc-shaped radial guide surface acts as a radial guide means.As a result, pellets cut off by the cutting means and / or broken in particular by vibrations in the area of ​​the through-bore do not fly uncontrollably radially outwards, where they could collide with sharp-edged surfaces of the pellet press and break into fragments of undefined length. Instead, these pellets are guided by the circular arc-shaped radial guide surface at a defined distance from the outer circumference of the ring die in the radial direction of the ring die and / or are specifically guided into a collecting area of ​​the pellet press. Furthermore, the radial guide surface guides the pellets broken in the area of ​​the through-bore, in particular by vibrations, to the cutting means. The cutting means is spaced from the ring die by a second annular gap. The radial width of the second annular gap is in certain embodiments (see, for example, the embodiment of the . Fig. 5 and Fig. 6) greater than the radial width of the first annular gap. As soon as the pellets guided from the radial guide surface to the cutting device come into contact with the cutting device, they are gently bent by the cutting device. The radial width of the first annular gap thus defines the maximum length of the pellets.

[0017] It is advantageous if the radial guide surface is inclined at least in one region, in particular in the region of at least one of its two circumferential ends, toward at least one of its two axially facing end faces. This axially extending slope of the radial guide surface allows separated pellets to be quickly removed from the separation area of ​​the cutting device. Preferably, the radial guide surface is substantially gable-roof-shaped in cross-section, in particular in the axial direction. This allows the pellets to be removed toward their two axial end faces.

[0018] It is advantageous if the distance in the radial direction of the annular die between the cutting-to-length means and the annular die provided for this purpose is essentially constant, preferably in the region of at least one of the radial through-bores or over the length L of the cutting-to-length means required at least for bending a pellet. This ensures that the pellet to be bent, immediately after it reaches the region of the cutting-to-length means, comes to rest in particular laterally on the cutting-to-length means and / or in particular on the front side on the radial guide surface. The pellet is preferably guided by the cutting-to-length means, in particular a contact surface of the cutting-to-length means, over its entire bending length L.

[0019] If the cutting means is designed to be so long that it extends over the area of ​​at least two radial through-bores or two bore rings—which are formed by the through-bores arranged one behind the other in the circumferential direction—it is advantageous if the distance between the cutting means and the ring die is constant over the entire length. Thus, the pellets sheared in the area of ​​the first through-bore or the first bore ring have the same length as the pellets sheared in the area of ​​the second through-bore or the second bore ring.

[0020] Alternatively or additionally, the substantially arcuate contour of the cutting means can also be designed such that the distance between the cutting means and the annular die is variable, so that the distance between the cutting means and the annular die in the region of a first bore ring is greater or smaller than the distance between these two in the region of a second bore ring. For this purpose, the cutting means is preferably stepped in the region of the arcuate contour and / or is designed to slope downwards or upwards from one end of the cutting means to its other end, in particular linearly or undulating. Advantageously, the pellets are thus not all cut from the annular die at the same length, but within a length spectrum that can be influenced by the design of the arcuate contour.Accordingly, the pellets cut by the cutting means in the region of the first bore ring have a different length than those cut in the region of the second bore ring.

[0021] The length range, or the length spectrum, within which the distance between the cutting tool and the ring die varies determines the Gaussian length distribution curve of the pellets. Particularly long pellets with the smallest possible variation (steep and narrow Gaussian curve) are preferred, for example, for pellet gasification in combined heat and power (CHP) plants. Medium-length pellets with a somewhat wider distribution increase the volume weight and are often used in small-scale combustion applications, where energy density plays a key role.

[0022] It is advantageous if the helical cutting means has a pitch angle of less than ± 90°, preferably less than ± 60°, particularly preferably less than ± 45°. The cutting means is thus arranged obliquely with respect to the axial axis of the ring die. As a result, the pellets not yet cut can move along the cutting means in the circumferential direction of the ring die over at least a small angular range, so that they are not abruptly decelerated by the cutting means. Undefined breakage of the pellets can thus be avoided. The pellets are thus advantageously cut or bent from the ring die essentially at a constant length or within a length spectrum.

[0023] The pellets are bent particularly gently when the pitch angle of the helical cutting means is selected to be very small, in particular in a range between 1° and 15°, particularly preferably in a range between 5° and 10°.

[0024] Depending on the pitch angle sign and the rotation direction of the ring die, the axial feed direction of the separated pellets can be influenced. Preferably, the pitch angle sign of the pitch angle relative to the rotation direction of the ring die is selected such that the separated pellets are fed in one of the two axial directions of the ring die, in particular toward a fixed housing part of the pellet press designed as a cover. This prevents the separated pellets from flying randomly around in the pellet press and hitting the edges of the pellet press, which could cause the pellets to break into at least two pieces of undefined length.

[0025] To compensate for manufacturing tolerances and to be able to adjust the pitch angle for different biogenic fiber-containing press materials, it is advantageous if the pitch angle of the cutting device is adjustable. This allows it to be adjusted within the framework of an iterative optimization process to ensure an optimal, preferably essentially constant, pellet length.

[0026] It is advantageous if the cutting means has at least two adjacent regions with mutually different pitch angles. This allows the separation process of the pellet from the annular die to be optimally designed so that the pellets are always separated at a substantially constant length or within a defined length range, without the pellets or the remaining part of the pellet remaining in the through-bores of the annular die being additionally broken. Preferably, the pellet protruding radially beyond the annular die is initially deflected substantially slightly in a first region having a smaller pitch angle and is only completely bent in a subsequent second region having a larger pitch angle.

[0027] In an advantageous development of the invention, the helical cutting-to-length means has a contact edge and / or contact surface for axially guiding and / or deflecting the pellet. By means of the contact edge, the contact surface and the associated friction between the cutting-to-length means and the pellet can be reduced. This can prevent the pellet from breaking into two undefined long pieces due to frictional forces in the area of ​​the cutting-to-length means. If the cutting-to-length means has a contact surface, very good guidance of the pellet can be achieved when it is guided along the cutting-to-length means, but also in the already cut state. After cutting, the pellet is preferably guided by means of the contact surface in the axial direction of the ring die into the area of ​​an ejection opening of the pellet press.Preferably, the contact edge and / or contact surface is arranged at an angle relative to the radial guide surface such that the pellet rests with its end face against the radial guide surface, and the contact edge and / or contact surface rests against its cylindrical side surface. The radial guide surface is therefore preferably oriented in the radial direction of the annular die, and the contact surface in the axial and circumferential directions of the annular die.

[0028] It is advantageous if the cutting means extends essentially helically over at least one region of the circular-arc radial guide surface, particularly in the circumferential direction over its entire length. Thus, immediately after bending in the radially outer region of the ring die, or even if the pellets had already broken in the through-bore of the ring die before the defined bending, they are guided in the radial direction of the ring die by the circular-arc radial guide surface directly adjacent to the cutting means. This prevents the cut pellets from spinning around uncontrollably inside the pellet press.

[0029] Advantageously, the contact edge, contact surface and / or radial guide surface are smooth to reduce friction between the cutting device and the pellet. Additionally or alternatively, it is advantageous if the contact edge, contact surface and / or radial guide surface has at least one lubrication opening for a lubricant, in particular a natural vegetable oil. This ensures that the pellets protruding radially beyond the annular die are not suddenly braked due to frictional forces, which would cause them to be uncontrollably bent or broken off at different lengths. Instead, they can slide along the contact edge, contact surface and / or radial guide surface with as little friction as possible, guided by them in the radial and / or axial direction.

[0030] It is advantageous if the cutting-to-length means, particularly in the radial guide surface, is designed as a shoulder, rib and / or groove. A cutting-to-length means designed as a shoulder has the advantage of being very robust and therefore has a very long service life. If the cutting-to-length means is designed as a rib, it can also advantageously be arranged in the area of ​​a roller mill of the pellet press, since the radially inner surface of the cutting-to-length means can then be kept very small in terms of area and consequently only a vanishingly small percentage of the pellets growing radially outwards in the area of ​​the roller mill hit the radially inner end surface of the cutting-to-length means or the rib with the front side of their free end against the radially inner end surface of the cutting-to-length means or the rib. Furthermore, with a cutting-to-length means designed as a rib, an adjustability of the pitch angle of the rib and / or adjustability of the rib relative to the radial guide surface can be implemented in a structurally simple manner.If the cutting means is designed as a groove, a targeted cutting of pellets can be carried out which have already broken in the area of ​​the through hole of the ring die and are pressed outwards into the groove due to their centrifugal force.

[0031] It is advantageous if the cutting device has at least a second cutting means which is arranged at a distance from or adjacent to the first cutting means in the axial and / or circumferential direction of the annular die. If the two cutting means are arranged at a distance from or adjacent to one another in the axial direction, the pitch angle of the two cutting means can advantageously be kept very small. As a result, the pellet has to travel a very long distance in the circumferential direction before it is bent over in the axial direction by one of the cutting means, so that this separation takes place very gently and carefully. If two cutting means are arranged at a distance from one another in the circumferential direction of the annular die, a free space can advantageously be formed in the area of ​​a roller so that the pellets growing radially outwards in this area are not hindered from their radial expansion by either cutting means.

[0032] Very low pitch angles of the cutting means and the associated gentle separation of the pellets from the ring die can be ensured if the two cutting means are arranged parallel or mirror-inverted to each other, preferably in such a way that they form a V-shape that diverges or converges in the direction of rotation of the ring die.

[0033] It is also advantageous if the cutting device is designed as a ring segment or a closed ring. For example, with a cutting device designed as a ring segment, several cutting devices can be arranged spaced apart from one another or adjacent to one another in the circumferential direction of the ring die. If the cutting device is designed as a closed ring, this cutting device can be replaced very quickly and cost-effectively, for example, to convert the pellet press.

[0034] It is also advantageous if the cutting device has a fastening device in the fastening area for detachable fastening to the stationary housing part of the pellet press and / or for adjustment, in particular continuously, relative to the latter in the radial direction. The fastening device is preferably designed as a rod element extending in the radial direction, which is rotationally and axially guided and fixable in a recess in the stationary housing part of the pellet press.

[0035] In order to avoid pellets of an undefined length protruding from the through-holes of the ring die being knocked off from pellets that have already been cut off and are flying around in the area between the outer circumference of the ring die and the radial guide surface, it is advantageous if the base body of the cutting device has at least one discharge opening and / or at least one discharge channel, in particular adjoining said discharge opening, for the defined bent pellets. The discharge opening is preferably designed and / or arranged in such a way, in particular in the area of ​​the radial guide surface and / or the cutting means, that the cut pellets can be guided radially outwards by centrifugal force, preferably directly, from the inside of the cutting device facing the ring die, in particular through the base body. After the bent pellets have been discharged from the annular gap, ieAny pellets that have escaped from the area between the ring die and the cutting device are guided to the ejection area of ​​the pellet press by means of the at least one discharge channel, particularly in the axial direction of the pellet press provided for this purpose. This advantageously prevents pellet jams in the area of ​​the cutting device, so that the cutting effect of the cutting device is not negatively influenced by the pellets that have already been cut to length.

[0036] To ensure the fastest possible removal of the separated pellets from the annular gap or annular gap segment, it is advantageous if the discharge opening is arranged adjacent to the cutting means, particularly directly and / or radially outwardly. In this regard, it is further advantageous if the discharge opening is formed, particularly in the radial direction of the annular die, between the radially inner cutting means and the radially outer guide surface.

[0037] The separated pellets can be removed quickly and gently from the annular gap if the discharge opening is arranged at an angle to the radial guide surface, in particular at 90°.

[0038] The second cutting device according to the invention for a pellet press has at least one cutting device for biogenic fiber-containing pellets, in particular wood pellets. Furthermore, the cutting device comprises at least one fastening area in which the cutting device can be fastened to a stationary housing part of the pellet press such that the cutting device can be arranged in the radially outer region of a rotatably mounted annular die of the pellet press, which has radial through-bores, and at a distance from the latter. The second cutting device has a base body with a concave, arcuate, in particular circular-arc-shaped, radial guide surface, which is designed as a cutting device.

[0039] For this purpose, the radial guide surface can be attached by means of the fastening area at a distance in the radially outer region of the annular die such that a pellet that protrudes beyond the annular die in its radial direction and / or is pressed radially outward in the region of a roller of the pellet press, in particular against the radial guide surface, comes to rest against the radial guide surface in the region of its free end, in particular its front side. The pellet is capable of moving along this radial guide surface, designed as a cutting means, in the circumferential direction such that the pellet is deflected by the radial guide surface by means of a friction force acting essentially in the circumferential direction of the annular die until it bends in the region of the annular die.

[0040] The pellet is therefore not abruptly decelerated, but guided circumferentially along the ring die with its end face facing the cutting device and pointing in the radial direction over a defined angular range. The pellet is increasingly deflected from its radial starting position in the circumferential direction of the ring die until it gently bends in the area of ​​the ring die or is separated from the ring die. This prevents the pellet from breaking or cutting into pieces of different lengths. As a result, the pellets advantageously have an essentially constant length determined by the distance between the outer circumference of the ring die and the inner contour of the cutting device or the radial guide surface designed for this purpose. This reduces the proportion of unwanted "short pellets" under 14 mm from an average of 60% to less than 10%.Furthermore, the amount of fine dust generated during separation can be reduced by up to 80%, which can lower production costs and increase throughput.

[0041] The second cutting device, in particular the radial guide surface designed as a cutting means, can preferably be arranged concentrically to the ring die provided for it. This allows the radial distance between the ring die and the radial guide surface to be kept constant over its entire length extending in the circumferential direction of the ring die. If the cutting device is arranged in an angular range of the ring die in which one of the roller mills of the pellet press is located, the pellets are pressed against the radial guide surface in the area of ​​their free ends due to the increase in length caused by the roller mill, so that the radial guide surface acts as a cutting means in this case. Accordingly, due to the resulting friction between the radial guide surface and the pellet end face, a force acts on the free end of the pellet, acting essentially in the circumferential direction, which force can gently bend the pellet essentially in the circumferential direction.

[0042] Alternatively, it can advantageously also be arranged eccentrically, so that the radial distance between the ring die and the radial guide surface changes in the circumferential direction. The second cutting-to-length device can thus advantageously be positioned such that a pellet arriving in the circumferential direction runs into the radial guide surface in the region of its free end and is thereby bent in the circumferential direction. For pellets already separated from the ring die as well as for pellets that have broken in the region of the through-bore of the ring die, the circular-arc-shaped radial guide surface also acts as a radial guide means. As a result, pellets cut off by the cutting-to-length device and / or broken in the region of the through-bore, in particular by vibrations, do not fly uncontrollably radially outwards, where they could impact sharp-edged surfaces of the pellet press and break into at least two fragments of undefined length.Instead, these pellets are guided through the arc-shaped radial guide surface at a defined distance from the outer circumference of the ring die in the radial direction of the ring die.

[0043] It is advantageous if the radial distance between the outer circumference of the annular die and the radial guide surface is constant in the circumferential direction. Alternatively, it is also advantageous if this distance decreases in the direction of rotation of the annular die, in particular from a first region to a second region of the radial guide surface by less than 5 mm, preferably by less than 2 mm. This promotes a gentle bending of the pellets.

[0044] It is also advantageous if the radial guide surface extends in the axial direction of the ring die over at least its entire width. Thus, each row of through holes can be covered by the radial guide surface.

[0045] It is advantageous if the radial guide surface is inclined at least in one area, in particular in the area of ​​at least one of its two ends pointing in the circumferential direction, in the direction of at least one of its two end faces pointing in the axial direction. By means of this axial gradient of the radial guide surface, separated pellets can be quickly removed from the separation area of ​​the cutting-to-length device. The radial guide surface is preferably designed to be inclined in cross-section, i.e. in the axial direction of the pellet press, at least in the direction of one of its end faces. It is preferably designed to be inclined towards both of its end faces, so that it is preferably essentially gable roof-shaped. As a result, the pellets can be quickly removed in the direction of their two end faces, so that any negative influence on the cutting-to-length process by the pellets that have already been cut to length can be avoided.

[0046] It is advantageous if the second cutting device is designed according to the above description of the first cutting device, wherein the features mentioned can be present individually or in any combination.

[0047] It is advantageous if the second cutting device is designed as a ring segment.

[0048] According to the invention, the pellet press for pressing biogenic fiber-containing pellets, in particular wood pellets, comprises a rotating ring die, a roller mill, and a cutting-off device. The rotatable ring die has essentially radial through-bores and forms a pressing chamber inside it into which biogenic fiber-containing pressing material can be fed. The at least one stationary roller mill is arranged eccentrically to the ring die and is capable of rolling along its inner circumference in such a way that the pressing material can be pressed through the through-bores to form the pellets. The cutting-off device comprises at least one cutting-off means and is fastened to a stationary housing part of the pellet press in such a way that the cutting-off means is arranged in the radially outer region of the rotatably mounted ring die at a distance from the latter.This advantageously creates an annular gap between the outer circumference of the annular die and the inner circumference of the cutting device. According to the invention, the pellet press comprises at least one first cutting device configured as described above and / or one second cutting device configured as described above. The aforementioned features may be present individually or in any combination in both the first and second cutting devices.

[0049] It is advantageous if the first and / or second cutting device is designed as a ring segment. This allows the cutting device to be specifically adapted to the conditions prevailing in the respective angular range. It is particularly suitable for the first cutting device to be arranged in the circumferential direction of the ring die in the area, particularly the angular range, between two adjacent rollers and / or for the second cutting device to be arranged in the area, particularly the angular range, of the respective roller.

[0050] To prevent the separated pellets from flying around uncontrollably inside the press housing, it is advantageous for the cutting devices, in particular at least some of their radial guide surfaces, to form a closed ring. For this purpose, they are advantageously arranged directly adjacent to their neighboring cutting devices and / or at least partially overlapping.

[0051] It is advantageous if the cutting means of the first cutting device extends over the area of ​​at least one of the through holes in the axial and circumferential direction of the ring die in such a way that a pellet which projects beyond the ring die in its radial direction with a length greater than the distance between the ring die and the cutting means comes to rest on the cutting means in the area of ​​its free end and is able to move along it in the circumferential direction in such a way that the pellet is deflected by the cutting means by means of a force having an axial component, so that it bends in the area of ​​the ring die.The pellet is therefore not abruptly decelerated, but guided circumferentially over a defined angular range of the ring die, which can be influenced in particular by the pitch angle of the helical cutting device. In the process, it is increasingly deflected from its radial starting position until the pellet gently bends or is separated from the ring die. This prevents undefined breaking or cutting of the pellet into pieces of different lengths. As a result, the pellets advantageously have a length that is essentially constant or varies within a length spectrum, determined by the distance. This allows the proportion of unwanted "short pellets" under 14 mm to be reduced from an average of 60% to less than 10%. Furthermore, the proportion of fine dust generated during separation can be reduced by up to 80%, thereby lowering production costs and increasing throughput.

[0052] Furthermore, the separated pellets are guided in the axial direction of the ring die by means of the cutting device, which extends helically in the axial direction. This prevents the separated pellets from being thrown undefined into unintended areas of the pellet press, which could damage them or even break them into at least two shorter, undefined pieces. The cutting device is therefore shaped in such a way that the pellets are gently bent and guided in the axial direction to an ejection area of ​​the pellet press.

[0053] It is advantageous if the distance in the radial direction of the annular die between the cutting device and the annular die provided for it is essentially constant in the area of ​​at least one of the radial through-bores, or at least over the length L of the cutting device required for bending a pellet. This ensures that the pellet to be bent rests against the cutting device immediately after it enters the area of ​​the cutting device and is guided by it over its entire bending length L.

[0054] If the cutting means is designed to be so long that it extends over the area of ​​at least two radial through-bores or two bore rings—which are formed by the through-bores arranged one behind the other in the circumferential direction—it is advantageous if the distance between the cutting means and the ring die is constant over the entire length. Thus, the pellets sheared in the area of ​​the first through-bore or the first bore ring have the same length as the pellets sheared in the area of ​​the second through-bore or the second bore ring.

[0055] Alternatively or additionally, the substantially arcuate contour of the cutting means can also be designed such that the distance between the cutting means and the annular die is variable, so that the distance between the cutting means and the annular die in the region of a first bore ring is greater or smaller than the distance between these two in the region of a second bore ring. For this purpose, the cutting means is preferably stepped in the region of the arcuate contour and / or is designed to slope downwards or upwards from one end of the cutting means to its other end, in particular linearly or undulating. Advantageously, the pellets are thus not all cut from the annular die at the same length, but within a length spectrum that can be influenced by the design of the arcuate contour.Accordingly, the pellets cut by the cutting means in the region of the first bore ring have a different length than those cut in the region of the second bore ring.

[0056] The distance between the annular die and the cutting-to-length means is preferably essentially constant. However, it is also conceivable for the distance to vary in the circumferential direction, in particular to increase or decrease. Furthermore, the cutting-to-length means can be designed into different regions with different distances from the annular die. This can achieve a length distribution of the pellets cut from the annular die, determined by the distance of the cutting-to-length means or the cutting-to-length means region from the annular die. Accordingly, it is advantageous for the flow properties of the pellets if they do not all have the same length, but rather their length is within a range of a length spectrum.

[0057] It is advantageous if the cutting device, designed as a ring segment, extends between two adjacent rollers in the circumferential direction of the ring die essentially over an angular range of 120° or 180°. This allows multiple ring segments, particularly with two or three rollers, to be arranged in the region of the outer circumference of the ring die in such a way that they do not extend into the region of the rollers where the pellets grow radially outward as they are forced through the through-bores. Furthermore, the ring segments thus have a sufficiently long length in the circumferential direction of the ring die to enable the smallest possible pitch angle for the helical cutting device.

[0058] It is also advantageous if at least two cutting devices designed as a ring segment and / or as a closed ring are arranged spaced apart from one another or adjacent to one another in the axial and / or circumferential direction of the ring die.

[0059] Advantageously, the cutting means of a first cutting device is designed as a shoulder or rib, and the cutting means of a second cutting device, circumferentially spaced from or adjacent to it, is designed as a groove. Thus, the pellets that extend radially beyond the annular die are initially bent by the first cutting device, causing them to detach from the annular die. Due to vibrations, pellets that have not yet reached the desired length may break in the through-bore. Once they break, they are carried radially outward by centrifugal force and come into contact with the radial guide surface, which guides them in the radial direction.When the broken pellets reach the area of ​​the second cutting device formed with the groove, they penetrate into the groove and, due to their helical shape, are deflected axially in such a way that they bend at a predefined length in the area of ​​the ring die.

[0060] It is advantageous if the cutting device is positioned at a distance of 18-22 mm from the ring die. Tests have shown that a distance of 18 mm is particularly suitable, as this results in a pellet length of approximately 22-26 mm, which essentially corresponds to the ideal pellet length.

[0061] It is advantageous if the contact surface is beveled near the contact edge. This largely prevents pellets that rise over the rear bending edge when bending and from sticking out of the free end.

[0062] For the groove depth, values ​​of 0.5 to 1 x D (pellet diameter) have proven advantageous. For the groove width, approximately 1.5 x D to 3 x D are recommended.

[0063] Further advantages of the invention are described in the following exemplary embodiments. It shows: Fig. 1 a schematic representation of a pellet press in cross section, Fig. 2 a perspective view of a first cutting device with a cutting means designed as a rib, Fig. 3 a perspective view of a first cutting device with a cutting means designed as a shoulder, Fig. 4a-4c show a sequential representation of the bending process in a cutting means designed as a rib of a first cutting device, Fig. 5 a perspective view of an alternative embodiment of the first cutting device with a cutting means designed as a groove, Fig. 6a-6d a sequential representation of the bending process for a cutting device designed as a groove, Fig. 7 a perspective view of a further embodiment of the first cutting device with two cutting means arranged in a V-shape relative to each other, Fig. 8 a perspective view of a further embodiment of the first cutting device with two cutting means spaced apart from each other in the axial direction and running parallel, Fig. 9 a detailed view of a pellet press in the area of ​​a first and / or second cutting device, Fig. 10 a perspective view of an alternative embodiment of a first cutting device with discharge opening, discharge channel and a cutting means designed as a shoulder, Fig. 11 an alternative embodiment of the first cutting device in cross section with a cutting means designed as a rib and a gable roof-shaped radial guide surface, Fig. 12 a second cutting device to be arranged in the circumferential direction of the ring die in the area of ​​a roller with a radial guide surface designed as a cutting means and Fig. 13 an alternative embodiment of the second cutting device in cross section with a gable roof-shaped radial guide surface designed as a cutting means.

[0064] In the following description of the figures, two alternative cutting devices are described, namely a first cutting device 13 and a second cutting device 14. These can both be used simultaneously in a pellet press 1, wherein they are arranged in different angular ranges to one another in the circumferential direction of the pellet press 1 (cf. Fig. 1). The first cutting device 13 is preferably arranged in the area between two rollers 7, 8. It is available in different versions in the Fig. 2, Fig. 3, Fig. 5, Fig. 7, Fig. 8, Fig. 10 and Fig. 11. In all embodiments, the cutting device 13 has a radial guide surface 26, on whose concave inner surface a cutting means 19 is arranged. According to the embodiments, the cutting means 19 can protrude in the radial direction beyond the radial guide surface 26, in particular in the form of a shoulder or rib (cf. Fig. 2, Fig. 3, Fig. 7, Fig. 8, Fig. 10, Fig. 11) and / or is formed as a recess, in particular as a groove and / or slot, in this (cf. Fig. 5).

[0065] In contrast to the first cutting device 13, the second cutting device 14 is preferably arranged in the circumferential direction of the pellet press 1 in the area above one of the roller mills 7, 8. The second cutting device 14, like the first cutting device 13, has a radial guide surface 26. However, this is designed as a cutting means 19. For this purpose, it is arranged in particular in the area above a roller mill 7, 8. The second cutting means 14 is in the Fig. 12 and Fig. 13 in various embodiments. Here, the cutting device 13 has, as a cutting means, exclusively the radial guide surface 26 designed for this purpose. As a variant, this can be designed in the shape of a gable roof.

[0066] Fig. 1 shows a schematic cross-section of a pellet press 1. The pellet press 1 has a substantially round housing part 2, which is stationary and has an ejection opening 3 in its lower region. A motor-driven, rotatably mounted annular die 4 is arranged inside the stationary housing part 2. The annular die 4 has radial through-bores 5 distributed over its entire circumference, which extend radially outwards from a pressing chamber 6 formed within the annular die 4. Two spaced-apart rollers 7, 8 are arranged within the pressing chamber 6. The two rollers 7, 8 are arranged eccentrically to the annular die 4 and roll on the inner circumference 9 of the annular die 4.

[0067] Biogenic, fibrous pressing material 10 is introduced into the pressing chamber 6 by a conveying device (not shown here). Due to centrifugal force, the pressing material 10 adheres to the inner circumference 9 of the rapidly rotating annular die 4. In the area of ​​the two rollers 7, 8, the pressing material 10 is pressed radially outward through the through-bores 5 of the annular die 4. This forms pellets 11 that extend essentially the entire length of the through-bore 5 and partially project radially beyond the outer circumference 12 of the annular die 4. For the sake of clarity, only one of the pellets 11 is provided with a reference symbol.

[0068] In the radially outer region of the annular die 4, four cutting devices 13, 14, 15, 16 are arranged at a radial distance from the latter. The cutting devices 13, 14, 15, 16 each have a fastening region 17 in their radially outer region, in which a fastening device 18 is formed. For the sake of clarity, only one of the cutting devices 13, 14, 15, 16 is provided with a reference numeral here. The cutting devices 13, 14, 15, 16 are fixedly connected to the housing part 2 by their respective fastening device 18. The fastening device 18 comprises an adjustment device (not shown here), by means of which the cutting devices 13, 14, 15, 16 can each be adjusted or displaced in the radial direction, preferably continuously. Using the adjustment device, the distance between the outer circumference 12 of the ring die 4 and the respective cutting device 13, 14, 15, 16 can be adjusted.The length of the pellets 11 to be separated in the respective area can be adjusted based on the distance between the annular die 4 and the respective cutting device 13, 14, 15, 16. The cutting devices 13, 14, 15, 16 each have a radial guide surface 26 for radially guiding the pellets 11. The distances of the radial guide surfaces 26 of the four cutting devices 13, 14, 15, 16 from the outer circumference 12 of the annular die 4 are essentially the same and / or constant in the present exemplary embodiment. Together, the radial guide surfaces 26 thus form a circumferential, in particular essentially closed, radial guide surface. The cutting devices 13, 14, 15, 16 are preferably spaced apart from one another by a small distance of preferably less than 60 mm. This prevents them from colliding with each other and blocking each other when adjusting in the radial direction.Alternatively, they can also be directly adjacent to one another or partially overlap at their ends. It is also conceivable for the cutting devices 13, 14, 15, 16 to be arranged at different distances from the ring die 4.

[0069] The cutting devices 13, 14, 15, 16 have, in their radially inner region, a cutting means 19 with a concave, arcuate contour 21. As explained in detail later, the cutting means 19 are designed as a first cutting means, so that they extend essentially helically in the axial direction of the annular die 4.

[0070] A pellet 11 pressed radially through one of the through-bores 5 by the two rollers 7, 8 therefore comes into contact with one of the first cutting-to-length devices 13, 14, 15, 16 if it projects further in the radial direction than the set distance between the outer circumference 12 of the annular die 4 and the cutting-to-length means 19 arranged at a distance therefrom. As the annular die 4 continues to rotate, the pellet 11 comes to rest in the region of its free end 20 on the helically designed cutting-to-length means 19, in particular in the region of its essentially cylindrical side surface, and moves along it in the circumferential direction of the annular die 4 over a defined angular interval. Due to the cutting-to-length means 19 extending helically in the axial direction of the annular die 4, the pellet 11 is deflected in the region of its free end 20 essentially in the axial direction of the annular die 4.The force from the cutting means 19, which essentially has an axial component, causes the pellet 11 to bend to a defined length in the area of ​​the outer circumference 12 of the ring die 4 (cf. . Fig. 4a-4c and Fig. 6a-6d). This bending process is very gentle, so that the pellets 11 produced with this device have a substantially constant length.

[0071] The cutting devices 13, 14, 15, 16 are designed as ring segments in this case. They are distributed at different angular intervals around the circumference of the ring die 4. Two adjacent cutting devices 13, 14, 15, 16 are each spaced apart from one another in the circumferential direction. In an alternative embodiment, however, these can also be directly adjacent to one another, forming a multi-part, circumferentially closed ring segment comprising the first, second, third, and fourth cutting devices 13, 14, 15, 16.

[0072] In the Fig. In the embodiment shown in Figure 1, the cutting devices 14, 16 arranged in the area of ​​the two rollers 7, 8 have a cutting means 19 designed as a groove 22 (cf. Fig. 5). In contrast, the cutting devices 13, 15 arranged adjacent to or spaced from the rollers 7, 8 in the circumferential direction have a cutting means 19 designed as a rib 23 and / or shoulder 24 (cf. Fig. 2 and Fig. 3). The two cutting devices 14, 16 arranged in the area of ​​the rollers 7, 8 are spaced a greater distance from the outer circumference 12 of the annular die 4 than the other two cutting devices 13, 15. Thus, the pellets 11 growing radially outward in the area of ​​the rollers 7, 8 are not hindered from growing in length by the second and fourth cutting devices 14, 16. Once they have reached the correspondingly set length, they are bent in a defined manner in the area of ​​the first and / or third cutting devices 13, 15 by the helical cutting means 19.

[0073] In contrast, the second and fourth cutting devices 14, 16, which are formed with a groove 22, essentially serve to separate broken pellets 11 in the through-bore 5 from the annular die 4 to a defined length. Thus, these broken pellets 11 are pressed radially outward against the second and fourth cutting devices 14, 16 due to centrifugal force, engaging in the groove 22 and being bent essentially in the axial direction.

[0074] Alternatively, the two cutting devices 14, 16 arranged in the area of ​​the rollers 7, 8 can also be designed without this groove 22. In this case, these cutting devices 14, 16 essentially only comprise the radial guide surface 26 for guiding and cutting the pellets 11. Accordingly, the concave and / or arcuate, in particular circular arcuate, radial guide surface 26 is designed as a cutting means 19. For this purpose, the radial guide surface 26 is arranged concentrically with the annular die 4 provided for it, so that the radial distance between the annular die 4 and the radial guide surface 26 is constant over its entire length extending in the circumferential direction of the annular die 4.In order to act as a cutting-to-length means 19, the radial guide surface 26 is further attached by means of the fastening region 17 at a distance in the radially outer region of the annular die 4 such that a pellet 11, which projects beyond the annular die 4 in its radial direction and is pressed radially outwards against the radial guide surface 26 in the region of a roller 7, 8 of the pellet press 1, comes to rest with its front side on the radial guide surface 26 in the region of its free end. As the annular die 4 rotates, the pellet 11 moves along this radial guide surface 26 designed as a cutting-to-length means 19 in the circumferential direction such that the pellet 11 is deflected by the radial guide surface 26 by means of a friction force acting essentially in the circumferential direction of the annular die 4 until it bends in the region of the annular die 4. The pellet is therefore not braked abruptly, but gently separated from the ring die 4.This prevents undefined breaking or cutting of the pellets 11 into pellet pieces of different lengths.

[0075] Alternatively, the radial guide surface 26 can also be arranged eccentrically, so that the radial distance between the annular die 4 and the radial guide surface 26 changes in the circumferential direction, in particular, decreases in the direction of rotation of the annular die 4. As a result, a pellet 11 arriving in the circumferential direction continuously runs onto the radial guide surface 26 in the region of its free end, causing it to bend in the circumferential direction. This alternative embodiment could also be used, for example, in the angular range between the two roller mills 7, 8.

[0076] The present invention is not limited to the Fig. 1, the spatial arrangement of the four cutting devices 13, 14, 15, 16 and their respective design, in particular of the respective cutting means 19, is limited. Thus, in particular, the number of cutting devices 13, 14, 15, 16 spaced apart in the circumferential direction from the annular die 4 and the angular range encompassed by them can vary as desired. Furthermore, the cutting means 19 of the respective cutting devices 13, 14, 15, 16 can be designed differently according to the following description. Accordingly, the cutting devices 13, 14, 15, 16 can be designed as first cutting devices according to the exemplary embodiment described above (cf. Fig. 2, Fig. 3, Fig. 5, Fig. 7, Fig. 8, Fig. 10 and Fig. 11). Alternatively, all or only some of the cutting devices 13, 14, 15, 16 can be designed as second cutting devices, which then essentially only have one radial guide surface designed as a cutting means (cf. Fig. 12 and 13). In a preferred embodiment, the cutting devices 14, 16 arranged in the area of ​​the rollers 7, 8 of the Fig. 1 as a first cutting-to-length means. For this purpose, the radial guide surface 26 can be attached by means of the fastening region 17 at a distance in the radially outer region of the annular die 4 such that a pellet 11 which projects beyond the annular die 4 in the radial direction and / or is pressed radially outwards in the region of a roller 7, 8 of the pellet press 1, in particular against the radial guide surface 26, comes to rest against the radial guide surface 26 in the region of its free end, in particular its front side. The pellet 11 is capable of moving along this radial guide surface 26, designed as a cutting-to-length means 19, in the circumferential direction such that the pellet 11 is deflected by the radial guide surface 26 by means of a frictional force acting essentially in the circumferential direction of the annular die 4 until it bends in the region of the annular die 4.The pellet 11 is thus not abruptly decelerated, but is guided along its end face facing the cutting means 19 and pointing in the radial direction in the circumferential direction over a defined angular range of the annular die 4. In this process, the pellet 11 is increasingly deflected from its radial starting position in the circumferential direction of the annular die 4 until the pellet 11 gently bends in the area of ​​the annular die 4 or is separated from the annular die 4.

[0077] Fig. Figure 2 shows a first embodiment of the cutting device 13 with a base body 25, which has a concave, circular-arc-shaped radial guide surface 26 on its side facing the ring die 4. The cutting means 19 is formed in the region of the radial guide surface 26. The cutting means 19 is helical. It therefore extends as part of a screw surface in the axial direction of the ring die 4 (not shown here) (see Figure 4). Fig. 1) or substantially helical over at least a portion of the circular arc-shaped radial guide surface 26. The cutting means 19 has a pitch angle α.

[0078] The cutting means 19 of the cutting device 13 is designed as a rib 23. The rib 23 rises radially inward from the radial guide surface 26 in the direction of the ring die 4 provided for this purpose (see Fig. 1). The cutting means 19, designed as a rib 23, comprises a contact edge 27 and a contact surface 28 extending substantially over its entire length.

[0079] The cutting device 13, which is designed as a ring segment in the present case, has a feed opening 29 in the region of one of its two ends, from which the pellets 11 (not shown here) enter the region of the cutting device 13. During their further movement in the circumferential direction of the cutting device 13, the pellets 11 slide along the contact surface 28 and / or the contact edge 27, wherein, due to the helical design of the contact edge 27 or contact surface 28 of the cutting means 19, they are deflected in the axial direction in such a way that they bend in the region of the ring die 4.

[0080] The Fig. The first embodiment of the cutting device 13 shown in Figure 2 has the advantage that, due to the rib 23, it has only a small area that protrudes beyond the radial guide surface 26. Accordingly, this embodiment is very well suited for placement in the area of ​​the rollers 7, 8 (see Figure 2). Fig. 1), since this only prevents a negligible proportion of the pellets 11 from their radial growth.

[0081] In the Fig. 3, Fig. 5, Fig. 7 and Fig. Figure 8 shows further embodiments of the cutting device 13, with the same reference numerals being used for the same features. Unless explained in detail again, their design and mode of operation correspond to the features already described above.

[0082] This shows Fig. 3 shows an alternative second embodiment of the cutting device 13 in which the cutting means 19 is designed as a shoulder 24. The cutting device 13 is thus very robust, so that the contact surface 28 cannot bend relative to the radial guide surface 26.

[0083] The Fig. 4a to 4c illustrate in a sequential representation the mode of action of the Fig. 2 as a rib 23 formed cutting means 19. The function of the Fig. The second alternative embodiment shown in Figure 3, in which the cutting means 19 is designed as a shoulder 24, is identical to this.

[0084] The pellets 11 are according to Fig. 4a are pressed radially outward through the through holes 5 by means of the rollers 7, 8 (not shown here), so that they protrude beyond the outer circumference 12 of the annular die 4 to varying lengths. However, the pellets 11 are only to be separated from the annular die 4 once they have reached a predetermined length. This length is determined by the distance between the outer circumference 12 of the annular die 4 and the arcuate contour 21 of the cutting means 19. Thus, the pellets 11 in the area of ​​the feed opening 29 reach the area of ​​the cutting means 19 as the ring die 4 continues to rotate relative to the cutting device 13. If the pellets 11 protrude beyond the ring die 4 in its radial direction with a length greater than the distance between the ring die 4 and the cutting means 19, they come to rest in the area of ​​their free ends 20 on the contact edge 27 and / or the contact surface 28 of the cutting means 19.

[0085] As the ring die 4 continues to rotate, the pellets 11 move along the cutting means 19, resting against it. Due to the helical design of the cutting means 19, it moves in the axial direction of the ring die 4 at a constant distance from it, from one of its two end faces to the other (see FIG. Fig. 4a-4c). The pellets 11, which have a certain minimum length, are deflected by the cutting means 19 by a force introduced essentially in the axial direction to such an extent that they are bent in the area of ​​the outer circumference 12 of the annular die 4 (cf. Fig. 4b).

[0086] As soon as the pellets 11 are Fig. 4b are separated from the annular die 4, they are guided in the radial direction by the radial guide surface 26. This prevents the separated pellets 11 from being thrown at high speed against the stationary housing part 2 of the pellet press 1, which could cause them to break into smaller pieces (see Fig. 1).

[0087] In a Fig. In the third embodiment of the cutting device 13 shown in Figure 5, the cutting means 19 is designed as a groove 22. Based on the Fig. 6a-6d, it can be seen that the cutting means 19 designed as a groove 22 is designed to cut off pellets 11, which have already been broken in the through-bore 5, from the annular die 4 to a defined length.

[0088] According to Fig. 6a, initially none of the pellets 11 in the area of ​​its free end 20 touches the radial guide surface 26. However, due to vibrations, it may happen that individual pellets 11 break in the area of ​​the through-hole 5 and are moved radially outwards due to the centrifugal force. In this case, they are Fig. 6b are prevented from uncontrolled radial ejection by the radial guide surface 26. Thus, these broken pellets 11 adhere to the radial guide surface 26 in the region of their free end 20, which then guides them in the radial direction.

[0089] Due to the helical design of the cutting means 19 designed as a groove 22, the groove moves in the direction of the pellet 11 as the ring die 4 rotates further in the axial direction. As soon as the cutting means 19 is in accordance with Fig. 6c comes into the area of ​​the pellet 11 resting against the radial guide surface 26, the pellet 11 penetrates into the groove 22 due to the centrifugal force. In this case, the pellet 11 comes into contact with the contact edge 27 and / or the contact surface 28 in the area of ​​its free end 20 and moves at least partially along it in the circumferential direction.

[0090] The cutting means 19, with its contact edge 27 and / or contact surface 28, exerts a force having an axial component on the pellet 11 in the region of its free end 20. As a result, the pellet 11 is cut according to Fig. 6d is deflected until it bends in the area of ​​the outer circumference 12 of the annular die 4 and detaches from it. After separation, the separated pellet 11 rests with its longitudinal side against the radial guide surface 26. The radial guide surface 26 thus prevents the separated pellet 11 from being thrown uncontrollably with great force against the housing parts of the pellet press 1, which could cause the pellet 11 to break into smaller pieces.

[0091] Fig. Figure 7 shows a further embodiment of the cutting device 13, which has a first and second cutting means 19, 30. The two cutting means 19, 30 are designed as ribs 23a, 23b in this case. Furthermore, they are arranged relative to one another in such a way that they form a converging V-shape in the direction of rotation of the annular die 4. The two cutting means 19, 30 are therefore arranged mirror-inverted to one another, with the first cutting means 19 having a positive pitch angle α and the second cutting means 30 having a negative pitch angle β. The pellets 11 (not shown here) reach the area of ​​the two cutting means 19, 30 via the common feed opening 29.

[0092] The cutting device 13 can also be arranged relative to the annular die 4 such that the two cutting means 19, 30 form a diverging V-shape. Accordingly, the pellets would enter the area of ​​the second cutting means 30 via a first feed opening 29a and the area of ​​the first cutting means 19 via a second feed opening 29b.

[0093] In an embodiment not shown here, the pitch angles can also be of different sizes, so that an inclined V-shape is formed.

[0094] In a Fig. In the further embodiment of the cutting device 13 shown in Figure 8, the two cutting means 19, 30 are at a constant distance from each other in the axial direction of the ring die 4. The two pitch angles α, β of the two cutting means 19, 30 are therefore both positive or negative. The pellets 11 (not shown here) reach the respective cutting means 19, 30 via the two feed openings 29a, 29b. The two cutting means 19, 30 thus divide the pellets 11 projecting radially beyond the ring die 4 into two areas in the axial direction. Advantageously, the pitch angle α, β of the two cutting means 19, 30 can thus be adjusted in comparison to the Fig. The embodiment of the cutting device 13 shown in Figure 2 can be designed to be flatter. The flat pitch angle α, β makes it possible to bend the pellets gently and much more slowly, without the high accelerations that previously occurred.

[0095] The Fig. 2, Fig. 3, Fig. 5, Fig. 7 and Fig. The exemplary embodiments of the cutting device 13 shown in Figure 8 can alternatively also extend over the entire circumference of the annular die 4. Accordingly, the cutting device 13 would be designed as a closed circle. Furthermore, several cutting devices can of course also be arranged adjacent to one another or spaced apart in the axial direction of the annular die 4 in the pellet press 1. Any combination of cutting means 19 designed as grooves 22, ribs 23 and / or shoulders 24 is also conceivable. Furthermore, the respective end of the cutting device in the region of the feed opening 29, from which the pellets to be separated are fed, must be designed to be very thin in order to prevent the pellets 11 from running against the end of the cutting means 19 and being abruptly braked. This can be achieved additionally or alternatively by axially positioning the ends outside the region of the annular die 4.

[0096] Fig. 9 shows a detailed view of the pellet press 1 from Fig. 1 in the area of ​​the fourth cutting device 16. As already described in the description of Fig. 1, the cutting devices 13, 14, 15, 16 are spaced apart by a small distance of preferably 10 mm. This advantageously prevents them from colliding with one another and blocking one another during radial adjustment. The disadvantage here is that, due to manufacturing tolerances and / or inaccurate adjustment of the radial distances, pellets 11 impact an end of one of the cutting devices 13, 14, 15, 16 that is higher in the radial direction, which would cause them to be abruptly decelerated. To prevent this, at least one of the cutting devices 13, 14, 15, 16 has an inlet surface 32 adjacent to the radial guide surfaces 26. In the present exemplary embodiment, the inlet surface 32 is arranged at the end of the radial guide surface 26 of the fourth cutting device 16 that faces opposite the direction of rotation of the pellets 11.

[0097] Accordingly, for example, a pellet 11 broken in the area of ​​the third cutting device 15 in the through-bore 5 of the annular die 4 (not shown here) is pressed by centrifugal force with its free end 20 against the radial guide surface 26 of the third cutting device 15 and guided radially by the latter. As soon as the pellet 11 reaches the area of ​​the fourth cutting device 16, it can move slightly radially outwards due to the beveled entry surface 32. This prevents the pellet 11 from impacting the end of the fourth cutting device 16 and being suddenly decelerated. The entry surface 32 then guides the pellet 11 to the radial guide surface 26, which guides the pellet 11 further in the circumferential direction.

[0098] In the detailed view of Fig. 9 shows that the cutting means 19 or the rib 23 of the first cutting device 13 extends circumferentially into the area of ​​the fourth cutting device 16 arranged adjacent thereto. The projecting area of ​​the cutting means 19 thus forms a radial stop 31 for the fourth cutting device 16. When the distance between the first cutting device 13 and the annular die 4 is adjusted, the fourth cutting device 16 can be displaced radially inward until its radial guide surface 26 abuts the stop 31 of the first cutting device 13. The radial guide surfaces 26 of the two cutting devices 13, 16 are then at essentially the same distance from the annular die 4.

[0099] The Fig. The embodiment shown in Figure 10 essentially corresponds to the one shown in Fig. 3, wherein the cutting means 19 is designed as a shoulder 24. In addition, however, the cutting device 13 has a discharge opening 33. A discharge channel 34 adjoins this discharge opening 33. This prevents pellets 11 protruding from the through-bores 5 of the annular die 4 from being knocked off in an undefined length by pellets 11 that have already been cut off and are flying around in the area between the outer circumference of the annular die 4 and the radial guide surface 26.

[0100] The discharge opening 33 is designed and / or arranged in the region of the radial guide surface 26 and / or the cutting means 19 in such a way that the separated pellets 11 can be discharged radially outwards by centrifugal force from the inside of the cutting device 13 facing the ring die 4, in particular through the base body 25. After the bent pellets have emerged from the annular gap, i.e. from the area between the ring die 4 and the cutting device 13, via the at least one discharge opening 33, they are guided by means of the at least one discharge channel 34 to the ejection area of ​​the pellet press (not shown here).

[0101] The outlet opening 33 is arranged directly adjacent to and / or radially outwardly from the cutting means 19 - in this case to paragraph 24. According to Fig. 10, the outlet opening 33 is formed in the contact surface 28.

[0102] Fig. Figure 11 shows an alternative embodiment of the first cutting device 13, in cross-section. The key difference from the previous embodiments is that the radial guide surface 26 has a first 35 and a second bevel 36. As a result, the radial guide surface has a gable-roof shape in cross-section. Advantageously, separated pellets 11 can be removed very quickly from the area of ​​the cutting means 19, 30.

[0103] Fig. 12 shows a, preferably in the circumferential direction of the ring die 4 in the area of ​​a roller 7, 8 (cf. Fig. 1), attachable second cutting device 14 with a radial guide surface 26 designed as a cutting means 19. Furthermore, the second cutting device 14 comprises at least one fastening area (not visible due to the interior view), in which the second cutting device 14 can be fastened to a stationary housing part of the pellet press 1 such that the cutting means 19 or the radial guide surface 26 designed therefor can be arranged in the radially outer region of the rotatably mounted annular die 4 of the pellet press 1 and at a distance from it. The second cutting device 14 has a base body 25, which has on its inner surface the concavely curved radial guide surface 26, which acts as the cutting means 19.For this purpose, the radial guide surface 26 can be attached by means of the fastening region 17 at a distance in the radially outer region of the annular die 4 such that a pellet 11 which projects beyond the annular die 4 in its radial direction and / or is pressed radially outwards in the region of a roller 7, 8 of the pellet press 1, in particular against the radial guide surface 26, comes to rest against the radial guide surface 26 in the region of its free end, in particular its front side. The pellet 11 is capable of moving along this radial guide surface 26, designed as a cutting means 19, in the circumferential direction such that the pellet 11 is deflected by the radial guide surface 26 by means of a frictional force acting essentially in the circumferential direction of the annular die 4 until it bends in the region of the annular die 4.The pellet 11 is thus not abruptly decelerated, but rather guided in the circumferential direction along its end face facing the cutting means 19 and pointing in the radial direction over a defined angular range of the annular die 4. In this process, the pellet 11 is increasingly deflected from its radial starting position in the circumferential direction of the annular die 4 until the pellet 11 gently bends in the area of ​​the annular die 4. This prevents undefined breaking or cutting of the pellets 11 into pieces of different lengths.

[0104] Fig.Figure 13 shows a cross-sectional view of the second cutting device 14 in an alternative embodiment. The key difference from the previous embodiment is that the radial guide surface 26 has a first 35 and a second bevel 36. As a result, the radial guide surface 26 has a gable-roof shape in cross-section. Advantageously, this allows separated pellets 11 to be removed very quickly.

[0105] Of course, it is also conceivable that the alternative cutting devices explained above also have such a discharge opening 33 and / or a corresponding discharge channel 34.

[0106] The present invention is not limited to the illustrated and described embodiments. Modifications within the scope of the patent claims are possible, as are combinations of features, even if they are illustrated and described in different embodiments. List of reference symbols 1 pellet press 2 Housing part 3 Ejection opening 4 ring die 5 through holes 6 Press room 7 first Koller 8 second Koller 9 inner circumference 10 Press material 11 pellets 12 Outer circumference 13 first cutting device 14 second cutting device 15 third cutting device 16 fourth cutting device 17 Mounting area 18 Fastening device 19 first cutting device 20 free end 21 arched contour 22 grooves 23 rib 24 paragraph 25 basic bodies 26 Radial guide surface 27 contact edge 28 contact surface 29 Feed opening 30 second cutting device 31 stop 32 entrance area 33 Exit opening 34 Exit channel 35 first slope 36 second slope α first pitch angle β second pitch angle

Claims

[1] Cutting device (13; 14; 15; 16) for a pellet press (1) with at least one cutting means (19) for biogenic fibre-containing pellets (11) and at least one fastening area (17) in which the cutting device (13; 14; 15; 16) can be fastened to a fixed housing part (2) of the pellet press (1) in such a way that the cutting means (19) can be arranged in the radially outer area of ​​a rotatably mounted annular die (4) of the pellet press (1) and at a distance therefrom, wherein the cutting means (19) has a concave, arcuate contour (21) and can be mounted in the radially outer region of the ring die (4) by means of the fastening region (17), that the cutting means (19) with its arcuate contour (21) extends substantially helically over at least the area of ​​one of the radial through-bores (5) of the ring die (4), so that a pellet (11) which projects beyond the ring die (4) in its radial direction from the through-bore (5) with a length greater than the distance between the ring die (4) and the cutting means (19) comes to rest on the cutting means (19) in the region of its free end (20) and is able to move along it in the circumferential direction in such a way that the pellet (11) is deflected by the cutting means (19) by means of a force having an axial component, so that it bends in the region of the ring die (4), characterized by , that the cutting device (13; 14; 15; 16) has a base body (25) with a concave circular arc-shaped radial guide surface (26), in the area of ​​which the cutting means (19) is arranged. [2] Cutting device according to the previous claim, characterized by that the distance in the radial direction of the ring die (4) between the cutting means (19) and the ring die (4) provided for this purpose is essentially constant. [3] Cutting device according to one or more of the preceding claims, characterized by that the helical cutting means (19) has a contact edge (27) and / or contact surface (28) for axially deflecting the pellet (11). [4] Cutting device according to one or more of the preceding claims, characterized by that the cutting means (19) extends substantially helically over at least one region of the circular-arc-shaped radial guide surface (26), in particular in the circumferential direction over its entire length. [5] Cutting device according to one or more of the preceding claims, characterized by that the cutting means (19), in particular in the radial guide surface (26), is designed as a shoulder (24), rib (23) and / or groove (22). [6] Cutting device according to one or more of the preceding claims, characterized bythat the cutting device (13; 14; 15; 16) has at least one second cutting means (30) which is arranged at a distance from or adjacent to the first cutting means (19) in the axial and / or circumferential direction. [7] Cutting device according to one or more of the preceding claims, characterized by that the base body (25) has at least one discharge opening (33) and / or at least one discharge channel (34), so that separated pellets (11) can be guided radially outwards by the centrifugal force from the radially inner radial guide surface (26), in particular through the base body (25). [8] Cutting device according to one or more of the preceding claims, characterized by that the discharge opening (33) is arranged directly adjacent to the cutting means (19). [9] Cutting device according to one or more of the preceding claims, characterized bythat the outlet opening (33) is arranged at an angle to the radial guide surface (26), in particular by 90 °. [10] Cutting device (13; 14; 15; 16) for a pellet press (1) with at least one cutting means (19) for biogenic fibre-containing pellets (11) and at least one fastening area (17), in which the cutting device (13; 14; 15; 16) can be fastened to a fixed housing part (2) of the pellet press (1) in such a way that the cutting means (19) can be arranged in the radially outer region of a rotatably mounted annular die (4) of the pellet press (1) and at a distance from it, characterized by , that the cutting device (13; 14; 15; 16) has a base body (25) with a concave circular arc-shaped radial guide surface (26) which is designed as a cutting means (19), wherein the radial guide surface (26) can be mounted by means of the fastening region (17) at such a distance in the radially outer region of the annular die (4), that a pellet (11) which projects beyond the annular die (4) in its radial direction and / or is pressed radially outwards in the region of a roller (7; 8) of the pellet press (1), comes to rest on the radial guide surface (26) in the region of its free end (20) and is able to move along it in the circumferential direction in such a way that the pellet (11) is deflected by the radial guide surface (26) by means of a friction force acting in the circumferential direction of the annular die (4), so that it bends in the region of the annular die (4). [11] Cutting device according to the previous claim, characterized bythat the radial distance between the outer circumference of the annular die (4) and the radial guide surface (26) is constant in the circumferential direction or decreases in the direction of rotation of the annular die (4), in particular from a first region to a second region of the radial guide surface (26) by less than 5 mm, preferably less than 2 mm. [12] Cutting device according to claim 10 or 11, characterized by that the radial guide surface (26) extends in the axial direction of the ring die (4) over at least its entire width. [13] Pellet press (1) for pressing biogenic fibrous pellets (11), with a rotatable ring die (4) which has essentially radial through-bores (5) and forms a pressing chamber (6) in its interior, into which biogenic fibrous pressing material (10) can be fed, at least one roller (7; 8) which is arranged eccentrically to the annular die (4) and is capable of rolling on its inner circumference (9) in such a way that the pressing material (10) is pressed through the through holes (5) to form the pellets (11), and at least one cutting device (13; 14; 15; 16) having a cutting means (19) which is fastened to a fixed housing part (2) of the pellet press (1) in such a way that the cutting means (19) is arranged in the radially outer region of the rotatably mounted annular die (4) at a distance from the latter, characterized by , that the pellet press (1) has at least one first cutting device (13; 14; 15; 16) according to one or more of the preceding claims 1 to 9 and / or at least one second cutting device (13; 14; 15; 16) according to one or more of the preceding claims 10 to 12. [14] Pellet press according to the previous claim, characterized bythat the first cutting-off device (13; 15) is arranged in the circumferential direction of the ring die (4) in the region between two adjacent rollers (7; 8) and / or the second cutting-off device (14; 16) is arranged in the region of the roller (7; 8). [15] Pellet press according to one or more of the preceding claims, characterized by that the first and / or second cutting device (13; 14; 15; 16) is designed as a ring segment and / or that the radial guide surfaces (26) of at least two cutting devices (13; 14; 15; 16) designed as a ring segment form a closed ring. [16] A process for producing biogenic fibre-containing pellets (11) by means of a pellet press (1), the process comprising the following steps: Feeding biogenic fiber-containing press material (10) into a press chamber (6) formed in the interior of a rotatable ring die (4) of the pellet press (1), wherein the ring die (4) has substantially radial through-bores (5); Pressing the pressing material (10) to form the pellets (11) through the through holes (5) by rolling at least one roller (7; 8) arranged eccentrically to the ring die (4) on the inner circumference (9) of the ring die (4); Bending a pellet (11) by means of a cutting device (13; 14; 15; 16) having a cutting means (19) for biogenic fiber-containing pellets (11), wherein the cutting device (13; 14; 15; 16) is fastened to a stationary housing part (2) of the pellet press (1) in at least one fastening area (17) such that the cutting means (19) is arranged in the radially outer area of ​​the rotatably mounted annular die (4) at a distance from the latter, wherein the cutting device (13; 14; 15; 16) has a base body (25) with a concave circular arc-shaped radial guide surface (26), in the area of ​​which the cutting means (19) is arranged, wherein the cutting means (19) has a concave arcuate contour (21) and is mounted by means of the fastening region (17) in the radially outer region of the ring die (4) in such a way that the cutting means (19) with its arcuate contour (21) extends substantially helically over at least the region of one of the radial through-bores (5) of the ring die (4), wherein the pellet (11) is bent over by the pellet (11), which projects beyond the ring die (4) in its radial direction from the through-bore (5) with a length greater than the distance between the ring die (4) and the cutting-off means (19), coming to rest on the cutting-off means (19) in the region of its free end (20) and moving along it in the circumferential direction in such a way that the pellet (11) is deflected by the cutting-off means (19) by means of a force having an axial component and thus bends over in the region of the ring die (4), wherein the radial guide surface (26) acts as a radial guide means for pellets (11) cut off by the cutting means (19) and / or broken in the region of the through holes (5). [17] A process for producing biogenic fibre-containing pellets (11) by means of a pellet press (1), the process comprising the following steps: Feeding biogenic fiber-containing press material (10) into a press chamber (6) formed in the interior of a rotatable ring die (4) of the pellet press (1), wherein the ring die (4) has substantially radial through-bores (5); Pressing the pressing material (10) to form the pellets (11) through the through holes (5) by rolling at least one roller (7; 8) arranged eccentrically to the ring die on the inner circumference (9) of the ring die (4); Bending a pellet (11) by means of a cutting device (13; 14; 15; 16) of the pellet press (1) having a cutting means (19) for biogenic fiber-containing pellets (11), wherein the cutting device (13; 14; 15; 16) is fastened to a stationary housing part (2) of the pellet press (1) in at least one fastening area (17) such that the cutting means (19) is arranged in the radially outer area of ​​the rotatably mounted annular die (4) at a distance from the latter, wherein the cutting device (13; 14; 15; 16) has a base body (25) with a concave circular arc-shaped radial guide surface (26) which is designed as a cutting means (19), wherein the bending of the pellet (11) takes place in that the radial guide surface (26) is attached by means of the fastening region (17) at such a distance in the radially outer region of the annular die (4) that a pellet (11) which projects beyond the annular die (4) in its radial direction and / or is pressed radially outwards in the region of a roller (7; 8) of the pellet press (1) comes to rest on the radial guide surface (26) in the region of its free end (20) and moves along it in the circumferential direction in such a way that the pellet (11) is deflected by the radial guide surface (26) by means of a frictional force acting in the circumferential direction of the annular die (4) and thus bends in the region of the annular die (4). [18] Use of a pellet press (1) according to one of claims 13 to 15 for producing biogenic fibre-containing pellets (11).

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