NO171952B - PELLETING PROCEDURE AND APPARATUS - Google Patents

Description

The invention relates to a method for pelletizing precursors, where the material or the material mixture to be pelletized is conditioned in a reaction vessel under elevated temperature before the pelleting, where the material in the reaction vessel is compressed under the influence of a conveyor element, so that at the outlet end of the reaction vessel a working pressure which is exerted against the material or material mixture, and where this pressure which is exerted against this amount of material, is then lowered by expansion to a reduced expansion pressure which is less than this pressure, especially atmospheric pressure.

It is known that dust and powdery and similar substances can be transferred to forms that are easier to store and better used by pelletizing them. For this purpose, the starting material is e.g. pressed through holes in matrices where it opposes the movement due to friction, so that the material is densified. After the review, the strings produced in this way are cut to the desired length by means of knives that move in relation to the matrix, so that pellets are obtained. In this way, e.g. mealy and powdered substances that are less suitable for feeding animals with are processed into pellets that are advantageous for use as feed.

Before pelleting, conditioning is often carried out. The main purpose of the conditioning is the beneficial effect on the physiological properties of the forage or its components, i.e. the digestibility for the animals. In order for the pelletizing process to be successful, conditioning must also usually be carried out in advance, which has a decisive influence on the densification process, the compressibility of the components, the firmness of the pellets and thus the preliminary quality (IFF report no. 1 "Das Pelletieren von Mischfutter", published by the Forschungsinstitut Futtermitteltechnik der Internationalen Forschungsgemeinschaft Futtermitteltechnik e.V. (IFF), Frickenmiihle, 3300 Braunschweig-Thune).

The conditioning or preparation must equalize different raw material moisture in the mixture, the elasticity of the particles must be improved, the resistance during shaping (densification) must be reduced, adhesion forces must be built up with the help of moisture bridges, the firmness must be partially changed and adhesive properties must be worked up.

The corresponding conditioning, which is also carried out for materials other than precursors, usually consists of a heating and a moisture supply. With the so-called short-term conditioning, the passage time for the fabric through the conditioning device is usually less than 1 minute, as the conditioning takes place e.g. in a mixing screw device. In the case of long-term conditioning, the mixing is done first, as the conditioning then takes place in a larger container in which the material is moved relatively little. The residence time for long-term conditioning is at least 10 minutes, but can also be a multiple of this. Then, a short-term conditioning is often also carried out before introduction into the pellet press.

In all of these cases, the conditioning process consists mainly of atmospheric pressure. Even when the material is physically compressed using screw presses or the like, the material is always more or less unhindered in connection with the surrounding atmosphere.

A further disadvantage of the previously known conditioning devices is that the amount of flow through the conditioning device cannot be easily adapted to the varying working speeds of the pellet press. In the event of a sudden higher performance of the pellet press, the flow rate through the conditioning device should also be increased, which results in less residence time for the material in it. However, this shorter residence time cannot easily be compensated for at a higher temperature or humidity, because the steam would partially escape with an increased steam supply before it penetrates into the material or can enter into an interaction with it.

The purpose of the invention is to provide a method which can be carried out more easily, and which produces pellets whose dimensions exactly correspond to the desired dimensions.

The solution according to the invention consists in the conditioning being carried out at temperatures of up to 170°C, especially 150°C, and the pelleting being carried out after the expansion.

The material is therefore compressed in the reaction container by means of the conveyor element, e.g. via a conveyor or press screw, so that a plug of material is formed. Enclosed steam that is either supplied from outside or that arises due to the trapped moisture during heating cannot or only with difficulty escape from this material plug. In this way, this vapor pressure can possibly become considerably higher than the atmospheric pressure. The temperature of the material can therefore be significantly higher than 100°, without the reaction container having to be hermetically closed, which would prevent or make impossible the continuous transport of material through this container. Below that, temperatures of 170°C can easily be achieved, especially up to 150°C. The conditioning is preferably carried out at temperatures of approx. 120°C.

The necessary heat can be obtained from the outside by external heating of the reaction vessel, by means of heating devices in the reaction vessel, by means of frictional heat during transport and/or by supplying the material in the compressed area with a fluid in gaseous or liquid form that is under pressure, especially water vapour. .

The material's moisture content during conditioning is appropriate at approx. 10-3 0 weight percent.

In the compressed region, the material has an essentially constant pressure.

Only at the outlet of the container does a reduction of the pressure exerted against the material located there take place. The pressure exerted against the material is thus reduced only by the material leaving or having left the reaction device, while the pressures in the reaction vessel retain their original values, so that the process takes place continuously.

According to a particularly simple embodiment, a reaction vessel with one or more outlet openings is used. The outlet opening can e.g. be one outlet opening of an extruder with a relatively small cross-section, so that at the outlet due to the material transport forms a plug, which, despite the continuous working method, enables the material here to be kept at a greater pressure and thus a higher temperature.

If it concerns an extruder and several outlet openings are desired, these can be bores in a matrix from which the material flows out.

If a reaction container with one or more outlet openings with a variable cross-section is used, the conditioning process can at the same time be optimally adapted to the pellet press's working speed and/or other working parameters. Such parameters are the power consumption for the operation of the press, the temperature, the degree of expansion, the pellet quality or other parameters.

Also when the outlet cross-section cannot be changed, e.g. with a normal extruder, control or regulation of the pellet quality can of course be achieved by varying other parameters.

The outlet cross-section can either be set by hand or regulated automatically, as the automatic regulation takes place depending on the above-mentioned parameters or other parameters.

In an advantageous embodiment, a so-called expander is used.

Such an expander has been made known in another connection (DE-PS 35 29 229, DE-OS 35 44 298), so that a further description of this expander's details is not necessary. The content of the above-mentioned Offenlegungsschrift describing the expander shall hereby expressly be made part of the description in connection with this patent application.

The previously known expander has two purposes, namely e.g. preparation of oil seeds or oil fruits for the extraction of edible oil. The expander's task is mainly the production of intermediate products, which are to be further processed only after intermediate storage and possibly for a long time. With the known expander, it is therefore first necessary to cool and dry the intermediate products. For subsequent further processing, the material must first be heated and moistened.

During this conditioning, densification is to be achieved to achieve a higher bulk weight and a better cell dissolution or. cell disruption to achieve a better extraction.

Surprisingly, the known expander can also be used for conditioning materials for pressing pellets, also immediately before pressing, although the purpose of the conditioning there is completely different. In the conditioning process that is carried out before the pressing by the method according to the invention, the strength must be changed by heat treatment, the raw fibers must be softened and the proteins must be partially dissolved to trigger binding forces. According to the invention, it was surprisingly found below that these purposes can also be achieved with the help of the known conditioning process. Namely, it is possible to achieve an optimal adaptation of the work speeds of the expander and the pellet press. If e.g. the speed of the pellet press increases, the throughput speed in the expander can also be increased. In order for good conditioning to still take place, at the same time, e.g. the hydrostatic pressure of the fluid is increased and more steam is supplied. Due to the higher temperature that can be achieved in this way, the desired conditioning then takes place more quickly.

A further surprising result is that infectious agents are killed at the same time and the precursor is thereby made hygienic or sterile by means of the conditioning process according to the invention. Nor is this surprising effect anticipated by the known method or in any way close to it.

The used expansion device according to the invention, which functions as an expander, thus has the advantage that the pressure as well as the temperature can be regulated. This is very important so that the conditioning effect, with which the physiological properties of the lining materials are to be purposefully changed and influenced, can be set precisely and purposefully. It is also possible to regulate the flow rate, which is not possible or at least not possible to a sufficient extent in connection with front-mounted pellet presses or extruders. The further advantage that the expansion device can be mounted immediately in front of the pellet press consists in that the material leaving the expander does not first have to be cooled and dried and then reheated and moistened, but that it can be immediately further processed without loss of time and quality deterioration .

The latter advantage and several of the above-mentioned advantages appear below not only in connection with an expander with an adjustable cross-section, but also in methods where constant cross-sections are used.

However, it is not absolutely necessary to use the above-mentioned expander in connection with the invention. As was already mentioned above, on the contrary, the steam supply lines can be omitted when the material is heated to sufficiently high temperatures in another way.

The conditioning can be carried out at temperatures of up to 170°C and controlled humidity. Here, the conditioning can be carried out selectively in such a way that harmful enzymes are destroyed or rendered inactive, but that the quality of valuable substances, e.g. proteins, however, are not reduced.

In many cases, a mixture of different substances is processed for lining. In this case, it may be appropriate to condition only part of the flow of the material to be pressed in the expander. This is e.g. the case when a partial flow must be conditioned or processed under high temperatures and pressure, to destroy e.g. harmful enzymes. Another part can be subjected to a more gentle, conventional conditioning, so that the fabrics of this part flow are not damaged. Thus, especially e.g. valuable proteins or vitamins are not passed through the separator. In many cases, a partial flow of the material does not need to be conditioned at all, if the material is already in a suitable form for pelleting or for addition to the main material.

Whether all the material or only a partial flow is to be led through the expander and conditioned there depends on the properties of the individual material components as well as whether these material components are present separately or have already been mixed in advance.

In an advantageous embodiment of a device for carrying out the method according to the invention, the conditioning device and the pellet press are directly built together, so that the conditioned material can flow directly into the pellet press, e.g. fall into this, when the conditioning device is arranged above the press. As an outlet opening, the conditioning device below can have an annular slot, a flat slot or other types of narrowed outlet openings. The pellet press can be a flat die press or a ring die press. If the conditioning device and the pellet press are separated in the room, a continuous conveyor is suitably arranged between the two devices, in particular a screw conveyor, a scraper conveyor, a pneumatic conveyor system, a belt conveyor or another, per se known conveyor. Several such conveyors can also be arranged one behind the other if the spatial location requires this.

Especially in the case where the material leaves the conditioning device in string form, a comminution device can be arranged between the conditioning device and the pellet press which comminutes the material in such a way that it can be advantageously processed in the press.

In the following, the invention will be described in more detail with reference to the drawing which shows advantageous embodiments.

Fig. 1 is a diagram showing the principle structure

of a pellet press known in and of itself.

Fig. 2 is a diagram showing an embodiment of a

device with a flat matrix press according to the invention.

Fig. 3 is a drawing showing another advantageous embodiment with a ring die press. - Fig. 4 is a diagram showing another type of connection between the conditioning device and the pellet press.

For a better understanding of the invention, the known structure of a pellet press 20 will first be described in more detail with reference to fig. 1.

On a machine stand 1, a flat matrix 2 with bores 3 is attached, through which a material compressed by means of edge runner rollers 4 is pressed. The starting material, such as e.g. may be in the form of dust, is also filled from above through the opening 5 in the housing 6. The housing 6 is likewise attached to the machine stand 1.

A turntable 7 is attached to the machine stand 1 in a manner not shown in the figure, which is in connection with a drive device also not shown. This turntable, together with a vertical shaft 8 connected to it, can be rotated about a vertical axis in fig. 1 using the drive device.

An edge runner head 9 is attached to the vertical shaft 8 in such a way that it cannot rotate relative to it (it can only rotate with it), but it can however be displaced axially

on the vertical shaft 8 and is adjusted in height by means of springs 10, a hydraulic nut 11 and spacer rings 12 by pressing in or draining hydraulic fluid via the line 13 into the resp. from the hydraulic nut 11. The edge runner rollers are attached to the edge runner head 9 on shafts 14, so that they can rotate freely about these shafts and thus can roll on the matrix or the material layer by turning the edge runner head 9 about its vertical axis. Furthermore, it is provided with rifles or material take-up track 15 to facilitate the pressing process.

The pressed material flows in string form through the holes 3 of the matrix 2 and is divided into pieces by means of interrupter devices 16 which rotate together with the edge runner head.

Fig. 2 shows an embodiment of the device according to the invention, where a conditioning device 40 is arranged above the pellet press 20. This conditioning device has a cylindrical housing 21 and a filling opening 22. In the housing 21, a screw conveyor 23 is arranged which can be driven by a motor 24 Into the wall of the housing 21 several lines 25 are led, through which steam can be introduced from a steam source 26. The supply of steam through the lines 25 can also be controlled or regulated via valves 27 using devices that are not shown in the figure.

At the outlet, the housing 21 has a constriction 28 which can be closed completely or partially with a cone-shaped valve plate 29. The cone plate 29 is then pressed against the opening 28 by means of a hydraulic piston 30 to provide a counter pressure against the material. The hydraulic pressure is generated by means of a device 31 which in turn is controlled by a control and regulation unit 32. This control and regulation unit 32 also affects the steam source 26. In the lower part of fig. 2 it is shown that the pellet press 20 is driven by a motor 17 which drives a worm gear 18, which in turn drives a gear ring 19, which is firmly connected to the vertical shaft 8.

The operation of the device is as follows: The material to be pressed is introduced into the filling opening 22 in the direction of the arrows 3 3 and including by the screw 23 which is driven by the motor 24, pressed to the right against the opening 28. Steam is introduced through the steam lines 25 to heat the material. As a plug of material forms near the outlet of the screw, the pressure here is higher than atmospheric pressure, so that material temperatures of over 100°C can be produced, whereby the material is conditioned.

The thus conditioned material then falls in the direction of the arrows 34 into the pellet press 20, is compressed there and leaves this in the direction of the arrow 35. Excess steam that flows out of the conditioning device 40 together with the material can leave the device through a steam opening 36 in the direction of arrow 37.

In the one in fig. 3 embodiment, the pellet press 20 is a ring matrix press, where edge runner rollers 4 roll off on an annular matrix 3. In this embodiment, an external heating device 3 8 is also shown with which the conditioning device 4 0 can be heated from the outside by means of an energy source 39. The heating can include happen by means of steam, inductively, by means of resistance heating or in another known way. Of course, heating elements can also be arranged inside the conditioning device 40. If such heating elements 38 are arranged, the steam supply lines 25 can optionally also be looped.

At the one in fig. In the embodiment shown in 4, the conditioning device 40 and the pellet press 20 are arranged at a distance from each other. Between both devices there is a belt conveyor 60 which is driven by a motor not shown. In fig. 4, a comminution device 41 is also indicated with which the string-shaped material flowing out of the conditioning device 40 can be comminuted, so that it can flow into the pellet press 20 in a condition that enables optimal pressing.

As already mentioned, the conditioning speed can be adapted to the processing speed of the pellet press 20 by regulating the speed of the motor 24 of the conditioning device 40. In order for the conditioning to still take place under favorable conditions, the supply of steam to the conditioning device can be regulated accordingly.

During comparison trials, different precursors were pressed with and without the conditioning device. The residence time in the conditioning device 40 was 2 seconds, the temperature of the housing 21 was 122°C, while the steam pressure in the conditioning device 40 (the expander) was 30 bar. The results were as follows:

As can be seen from the table, the pellets produced using the expander are not only significantly more resistant to wear or rubbing, but also have a higher Kahl hardness. Furthermore, the number of bacteria is also drastically reduced. In this way, e.g. Salmonella bacteria contained in the raw material are effectively killed.

In summary, it can be said that the method according to the invention enables a better and simpler conditioning as well as a cheaper execution of this. In another embodiment according to the invention, a new application is provided for a known expander which, in a surprising and very advantageous way, enables a good conditioning of materials for pellet presses, which leads to a better use of value.

Claims (8)

1. Method for pelletizing precursors, where the material or material mixture to be pelletized is conditioned in a reaction vessel under elevated temperature before pelleting, where the material in the reaction vessel is compressed under the influence of a conveyor element, so that a working pressure is set at the outlet end of the reaction vessel which is exerted against the material or material mixture, and where this pressure which is exerted against this amount of material is then lowered by expansion to a reduced expansion pressure which is less than this pressure, especially atmospheric pressure, characterized in that the conditioning is carried out at temperatures of up to 170°C, especially 150° C, and that the pelleting is carried out after the expansion. 2. Method as stated in claim 1, characterized in that the material in the compressed area is supplied with a fluid in gas or liquid form, the fluid being under pressure. 3. Method as stated in claim 2, characterized in that water vapor is used as fluid. 4. Method according to one of the preceding claims, characterized in that the conditioning is carried out at temperatures of approx. 120°C. 5. Method according to one of the preceding claims, characterized in that the material during conditioning has a moisture content of approx. 10-30 percent by weight. 6. Method according to one of the preceding claims, characterized in that only a partial flow of the material to be compressed in the reaction vessel is conditioned. 7. Method as stated in one of the preceding claims, characterized in that a reaction apparatus is used which is characterized by a valve element which is designed as a back pressure head, which closes or at least narrows the outlet opening of the reaction vessel during the build-up phase of the working pressure (P), and which is connected to a back pressure element. 8. Method as stated in claim 7, characterized in that a back pressure element is used, whose pressure effect <p1>' is exerted against the container pressure P until the requirement P > P'" is met, so that the back pressure head moves away from the container outlet opening, and the back pressure head , after setting this requirement or after the relationship P < P<11> occurs for the first time, is again brought to the closed position due to the back pressure P'• which is now greater than P, and an equilibrium P = P<11> is established, which results in a constant outflow of material via the outlet gap formed between the retracted back pressure head and the container end flange.