AT13181U1 - Process for producing fuel pellets - Google Patents

Abstract

The invention relates to a process for the production of fuel pellets from waste plastics and / or cellulosic fibers containing material, wherein the material to be processed is kneaded in several temporally successive extrusion processes, compacted and finally by a perforated die (3.4) is pressed. According to the invention it is provided to press the material more often than once by an extrusion process through a perforated die, preferably using from extrusion to extrusion process perforated dies, each with a reduced diameter of the holes.

Description

Austrian Patent Office AT 13 181 U1 2013-08-15

Description: The invention relates to a method for producing fuel pellets. The inventive method is particularly well applicable to form pellets from plastic waste and from plant containing cellulose fibers materials.

At present, most of the pellets used as fuel, which consist of vegetable raw material, formed in edge milling presses. Such a press has a die in the form of a perforated surface and a plurality of rolling elements, which roll on the die. The raw material to be pressed into pellets is arranged together with the rollers on a die side; it is pressed through the rollers through the holes in the die and thereby compacted. At the side of the die remote from the rollers, the strands of compressed material bulging out of the holes of the die are broken or cut into short pellets. The method is well applicable if the material properties relevant for the pressing process are reliable and if the requirements for strength and minimum size of the grains of the final product are not all that high.

In the writings EP 159989 B1, AT 401525 B, DE 19918815 A1, AT 406565 B, EP 1916288 A2, CN 101797814 A and CN 101367272 B proposed fuel pellets from biomass and / or paper and / or waste plastic granules and / or oils To form fats, paint residues, etc., by compacting the raw material mixture in an extruder (also called "screw press" or "extruder screw") and pressing it through a perforated die. It has been shown that there are considerable difficulties in reproducibly producing pellets. Very often, the result is not satisfactory because either the required pressing forces are too high or because the resulting pellets are too brittle and / or too small and too different among themselves.

According to DE 3412158 C2, EP 186766 B1, CN 201736452 U and KR 20110016760 A, plastic waste is recycled predominantly to briquettes or pellets intended for incineration, by juxtaposing the waste in several extruders in succession and partly also in the same pressing space can lie, kneaded and compacted finally pressed through a perforated die. The more intensive kneading on two or more extruders instead of just one extruder causes better flowability of the material mixture and ultimately better internal cohesion of the extruded pellets or briquettes. In addition, additional substances can be added between individual extruders in order to influence properties and material composition in a more targeted manner. The result is still not always satisfactory. However, there are always the problems that either the required pressing forces are too high or that the resulting pellets are too brittle and / or too small and too different among themselves.

For example, according to DE 19854533 A1 it is proposed to cool an extruder screw by water, which is pumped through cavities in the extruder screw, while the extruder screw works.

Starting from this prior art, the object of the invention is to provide a method by means of which materials and mixtures of materials which contain waste plastics and / or natural or artificial fiber materials and also liquid fractions can be compacted into pellets. Compared to the previously known method, it should be better possible to produce one another in size and material properties as similar as possible pellets with high mechanical strength without the addition of a noteworthy high proportion of finer granules or dust is obtained.

For solving the problem, it is assumed that those processes in which the material to be processed is kneaded and compacted in a plurality of extruders acting on the material in temporal succession and finally pressed through a perforated die. As an improvement according to the invention, it is proposed to press the material not only after the last extrusion process through a perforated die, but after at least one previous extrusion process. Preferably, in the last extrusion process through a hole die such a die is provided, in which the diameter of the holes is smaller than the diameter of the perforated dies through which the material has already been pressed through.

Due to the feature of the invention, namely the multiple extrusion through hole matrices through - preferably with decreasing from Extrudiervorgang to Extrudiervorgang hole diameter - to reach a much better connection of the individual components of the raw material to a homogeneous, ultimately solid substance than this without Feature would be possible.

The invention will be illustrated by means of a diagram: [0010] FIG. 1 shows, in a stylized manner in partial sectional view, an exemplary device for the implementation of the method according to the invention.

According to FIG. 1, pellets are produced in three process sections, which are each carried out on a separate pelleting device 1, 2, 3.

Each pelletizer 1, 2, 3 comprises an extruder 1.3, 2.3, 3.3, a drive driving them 1.1., 2.1, 3.1 and a hopper 1.2, 2.2, 2.3 thereto, through which the material to be extruded is fed to the respective extruder , In addition, each pelleting device comprises in each case a perforated matrix 1.4, 2.4, 3.4, which is typically designed as a flat, circular disc whose surface is often interrupted by a uniform hole pattern of holes with circular cross-sectional areas of the same diameter. Ideally, hole dies each having a smaller diameter of the holes are used from process step to process step. For example, the hole die 1.4 can have 15 mm diameter holes, the die hole 2.4 holes with 10 mm diameter and the hole die 3.4 holes with 6 mm diameter.

In the example shown, a crusher 1.5, 2.5, 3.5 is arranged behind each perforated die, which breaks off the material strands emerging from the holes of the perforated die, so that pellets of reasonably defined length, for example about 10 mm in length, are formed. A crusher can be formed for example by a propeller-like rotating arrangement of strips.

It has been found that it is better to break off the material strands bulging out of the perforated dies at a small distance from the perforated dies, instead of cutting them off directly at the piercing dies by a cutting edge. Compared to cutting off, the energy and maintenance costs are lower when breaking because the material strands are "natural". Fracture lines fall apart into pellets.

Really important is the breaking or cutting of coming from a perforated material strands only after the last part of the process, so at the pelletizer 3. For the extrusion in the second and third process section, it does not matter whether short pellets or longer extruded products are supplied ,

In the individual Pelletiervorrichtungen it comes by internal friction to considerable heating of the processed material and parts of equipment. It may be useful to cool the extruder screws and / or the jacket.

The automatic heating of the processed material is almost always an advantageous effect, because it flowability and connectivity is improved and because water content, which is contained in the processed material, well wegtrocknet if the material from the individual hole matrices 1.4, 2.4, 3.4 swells. The drying is accelerated by the breaking of the material strands swelling out of the perforated dies, since this increases the surface area.

To enhance the drying, it is advantageous to keep the air in the area after the outputs from the hole matrices by a fan in motion and possibly constantly exchange. By the way, it is not necessary that, as shown, the material coming from a process section be further processed very soon in the next process section. For example, if necessary, the intermediate product coming from the first or second stage can be allowed to dry for a longer time and then be taken to the next stage of the process.

It has been found that the drive power to be applied by the drives 1.1, 2.1, 3.1 can be approximately the same size per processed material weight in each process section, if the hole matrices in the individual process sections have the same external dimensions. Thus, it is quite possible, instead of the illustrated three complete pelletizing devices 1, 2, 3, each performing exactly a process section to provide only a single pelletizer and to use them for the same material three times in succession and before the individual process sections the respectively appropriate Insert perforated matrix.

That is, you can process a lot of raw material in the first part of the process by the pelletizer 1, wherein the hole die 1.4 is used, in which the diameter of the holes of the breadboard, for example, is 15 mm.

The intermediate product obtained is temporarily stored. Then, the perforated die 1.4 is replaced at the pelleting device 1 by the Lochmatrize 2.4, wherein the diameter of the holes of the perforated grid, for example, 10 mm and the intermediate product from the first process step is processed once more in the pelletizer 1. Finally, the process step is carried out a third time on the pelletizing device 1, using the perforated die 3.4, in which the diameter of the holes of the breadboard is, for example, 6 mm. In this mode of operation, it is only possible to produce in batch mode and with a somewhat higher set-up effort, but it can cope with very low system costs.

In advantageous aspects which are achieved beyond the fulfillment of the underlying task of the invention, are briefly listed: By the method according to the invention not only for pelleting usual materials and material mixtures are better processed into pellets, there are also Such materials and material mixtures can be processed into pellets, which were previously - not pelletable - typically because of excessive brittleness or because of low flowability.

You will find per processing stage with relatively low drive power Auslangen, which reduces the cost of equipment. Taking into account the energy requirements for drying the material, the total energy requirement is comparatively low.

By using the waste heat in the individual processing stages saves you a separate drying of the raw material, since the residual moisture escapes during processing. The multi-stage kneading and compacting process is comparatively gentle on the material to be processed and on the individual plant components.

In the raw material fines, impurities and areas with segregated material fractions hardly disturb at all. This means that you can also process relatively poorly prepared raw material into high-quality pellets.

Since the raw material does not need to be pre-dried, and after the first stage of processing is already relatively compact, there is little risk of fire in the system. 3.5

Claims (6)

Austrian Patent Office AT 13 181 U1 2013-08-15 Claims 1. A method for producing fuel pellets from plastic waste and / or cellulose fiber-containing material, wherein the material to be processed is kneaded in a plurality of extrusion processes taking place in succession, compacted and finally conveyed through a perforated die ( 3.4) is pressed, characterized in that the material is pressed more often than once by an extrusion process through a Lochmatrize. 2. The method according to claim 1, characterized in that are used by extrusion process through a perforated die to Extrudiervorgang by a Lochmatrize, Lochmatrizen each with a reduced diameter of the holes. 3. The method according to claim 2, characterized in that three Extrudiervorgänge are carried out with each different in respect of perforated dies, that the diameter of the holes of the Lochmatrize is reduced from extrusion to extrusion process. 4. The method according to any one of claims 1 to 3, characterized in that by means of an extruder (1.3) a plurality of extrusion processes are carried out in succession through each different hole matrices. 5. The method according to any one of claims 1 to 4, characterized in that the swelling in a previous extrusion process by a perforated material strands are mechanically broken into pellets of limited length before the intermediate product is fed to the next extrusion process. 6. The method according to any one of claims 1 to 5, characterized in that the intermediate product obtained from a previous extrusion is dried before it is fed to the next extrusion process. 1 sheet of drawings 4/5