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Title:
METHOD AND INSTALLATION FOR PROCESSING WASTE
Document Type and Number:
WIPO Patent Application WO/2004/110634
Kind Code:
A1
Abstract:
The invention relates to a method for processing waste, comprising the steps of collecting the waste, separating the collected waste into at least one reusable fraction and at least one residual fraction, discharging the at least one reusable fraction for purposes of reuse, and incinerating the at least one residual fraction, wherein the at least one residual fraction is reprocessed for incineration purposes. The at least one residual fraction can be reprocessed by admixing thereto at least one combustible material and/or compressing thereof into granules. The invention also relates to an installation for performing this method, comprising an apparatus for collecting the waste, an apparatus connected to the collecting apparatus for separating the collected waste into at least one reusable fraction and at least one combustible fraction, at least one apparatus connected to the separating apparatus for discharging the or each reusable fraction, and at least one apparatus for reprocessing the at least one combustible fraction.

Inventors:
JANSEN ABRAHAM (NL)
Application Number:
PCT/NL2004/000424
Publication Date:
December 23, 2004
Filing Date:
June 14, 2004
Export Citation:
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Assignee:
SCHIMMELPENNINCK BEHEER B V (NL)
JANSEN ABRAHAM (NL)
International Classes:
B03B9/06; C10L5/46; F23G5/00; F23G5/02; (IPC1-7): B03B9/06; C10L5/46
Foreign References:
BE891875A1982-05-17
US4596584A1986-06-24
DE3128528A11983-02-03
US3848813A1974-11-19
GB2076013A1981-11-25
Attorney, Agent or Firm:
Bartelds, Erik (Sweelinckplein 1, GK The Hague, NL)
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Claims:
Claims
1. Method for processing waste, comprising the steps of: a) collecting the waste, b) separating the collected waste into at least one reusable fraction and at least one residual fraction, c) discharging the at least one reusable fraction for purposes of reuse, and d) incinerating the at least one residual fraction, characterized in that the at least one residual fraction is reprocessed for incineration purposes.
2. Method as claimed in claim 1, characterized in that the at least one residual fraction is reprocessed by admixing thereto at least one combustible material.
3. Method as claimed in claim 2, characterized in that at least one natural material is admixed as combustible material.
4. Method as claimed in claim 2 or 3, characterized in that at least one material with a high carbon content is admixed as combustible material.
5. Method as claimed in any of the claims 24, characterized in that at least one combustible binder is admixed.
6. Method as claimed in any of the claims 25, characterized in that dust released during separation of the waste is admixed as combustible material.
7. Method as claimed in any of the claims 26, characterized in that the mass ratio of the at least one residual fraction and the at least one combustible material is at least 1: 1.
8. Method as claimed in claim 7, characterized in that the mass ratio of the at least one residual fraction and the at least one combustible material lies between about 1.5 : 1 and 3: 1.
9. Method as claimed in any of the foregoing claims, characterized in that the at least one residual fraction is reduced in size for reprocessing purposes.
10. Method as claimed in any of the foregoing claims, characterized in that the at least one residual fraction is reprocessed by compressing thereof into granules.
11. Method as claimed in claims 2 and 10, characterized in that the at least one residual fraction is compressed into granules after at least one combustible material has been admixed thereto.
12. Method for reprocessing, for incineration purposes, of residual waste separated from a waste flow by admixing at least one combustible material to the residual waste and/or compressing the residual waste into granules.
13. Installation for processing waste, comprising an apparatus for collecting the waste, an apparatus connected to the collecting apparatus for separating the collected waste into at least one reusable fraction and at least one combustible fraction, and at least one apparatus connected to the separating apparatus for discharging the or each reusable fraction, characterized by at least one apparatus for reprocessing the at least one combustible fraction.
14. Waste processing installation as claimed in claim 13, characterized in that the reprocessing apparatus has means for admixing at least one combustible material to the at least one combustible fraction.
15. Waste processing installation as claimed in claim 14, characterized in that the admixing means comprise a system for supplying and admixing at least one natural material.
16. Waste processing installation as claimed in claim 14 or 15, characterized in that the admixing means comprise a system for supplying and admixing at least one material with a high carbon content.
17. Waste processing installation as claimed in any of the claims 1416, characterized in that the admixing means comprise a system for supplying and admixing at least one combustible binder.
18. Waste processing installation as claimed in any of the claims 1417, characterized in that the admixing means comprise a system for collecting and admixing dust released during separation of the waste.
19. Waste processing installation as claimed in any of the claims 1318, characterized by an apparatus for reducing the residual fraction in size which is placed prior to the reprocessing apparatus.
20. Waste processing installation as claimed in any of the claims 1319, characterized in that the reprocessing apparatus has means for compressing the residual fraction into granules.
21. Waste processing installation as claimed in claims 14 and 20, characterized in that the granule pressing means are placed downstream of the admixing means.
22. Reprocessing apparatus evidently intended for use in a waste processing installation as claimed in any of the claims 1321.
Description:
METHOD AND INSTALLATION FOR PROCESSING WASTE

The invention relates to a method for processing waste, comprising the steps of collecting the waste, separating the collected waste into at least one reusable fraction and at least one residual fraction, discharging the at least one reusable fraction for purposes of reuse and incinerating the at least one residual fraction. Such a method is known and has been in use for years in for instance Germany. Use is made herein for separation purposes of installations supplied by the company Herhof Umwelttechnik GmbH at D-35606 Soms-Niederbiel.

In the known method domestic refuse is collected and in the first instance reduced in size to particles of for instance less than 150 mm. The waste is then dried biologically, wherein the moisture escaping from the waste condenses and is drained. Organic constituents are also decomposed during this drying, which takes place in biological manner. The condensate is purified and can then be used as coolant, wherein it evaporates and is blown out into the environment. About 30% by weight is extracted from the waste during drying. The fraction remaining after drying, the so-called mixed, dry stabilate, thus forms only about 70% by weight of the original quantity of waste.

Not only is the quantity of waste decreased by the drying, but this waste is moreover biologically stabilized, since at a dry matter-content of more than 80% biological activity is no longer possible. The waste mass is hereby also hygienized and practically odourless owing to the absence of active bacteria. Finally, the drying has the result that the

material is no longer sticky, and can then be separated with high efficiency into different fractions using mechanical or physical techniques.

Separation takes place in the first instance between the non-combustible part of the waste and the fuel fraction thereof. The non-combustible fraction contains, among other things, metals, inert materials and glass. The fuel fraction, also referred to as RDF fraction (Refuse Derived Fuel), contains all other materials such as organic material, paper, plastics, fabrics, leather, rubber and the like. The non-combustible fraction, which amounts to about 20% by weight of the original waste quantity, is separated in a subsequent step into a light fraction and dust on the one hand and a heavy fraction on the other. The metal is then first separated from the heavy fraction, the metal in turn being separated again into ferrous metals, non-ferrous metals, and batteries and electronics scrap. The remaining fraction is then separated into glass and inert material, while the glass can be further separated into white, green and brown glass. The remaining inert or mineral fraction can be used as building material.

The proportion of the different fractions in the total waste quantity is shown in the table below.

Table 1

Fraction Percentage Condensate/organic material 30 Non-combustible material, of 20 which: - light fraction/dust 3 - ferrous metals 4 - non-ferrous metals 1 - battery/electrical 0.5 - white glass 2 - green glass 0.5 - brown glass 0.5 - minerals 9 Combustible material 50 In the known method the fuel fraction, which is released during the first separation after drying and which takes up about 50% by weight of the total quantity of waste, is eventually incinerated. During this incineration heat is released which is converted by turbines and generators into electrical energy. The ash or slag remaining after incineration can be further used, for instance as foundation material for roads.

The known method has a number of advantages relative to the conventional incineration of unsorted waste such as has been carried out heretofore in most waste incineration plants (WIPs). In the first place determined valuable materials are thus recovered instead of being lost through incineration. In addition, the quality of the incineration is better, and the energy output therefore higher, due to the greater homogeneity of the fuel fraction.

The quality of the remaining ash is also better, and the

waste gases are cleaner than in integral waste incineration.

The known method does however have the drawback that the energy content of the fuel fraction is considerably smaller than that of fossil fuels. This means that it must be incinerated separately, for instance in a WIP, and cannot be used as fuel in a power station. The efficiency of the incineration of this waste fraction is hereby limited because WIPs, which are after all intended to be multi-burners, generally operate less efficiently than power stations geared to a determined quality of fuel.

The invention therefore has for its object to provide a method of the above described type, wherein this drawback does not occur. This is achieved according to the invention in such a waste processing method in that the at least one residual fraction is reprocessed for incineration purposes. By reprocessing the residual fraction the energy content thereof is increased, and brought into line with that of conventional fossil fuels, such as for instance coal. In this manner the residual fraction can thus be used as fuel in a power station. Because the reprocessed residual waste is cheaper than the fossil fuel a cost-saving is hereby achieved, while in addition the finite supplies of fossil fuels will be exhausted less quickly. Furthermore, the emission of greenhouse gases, in particular CO 2, is decreased compared to energy generation based wholly on fossil fuel.

According to a first aspect of the invention, the at least one residual fraction is reprocessed by admixing thereto at least one combustible material. The addition of a combustible material is a very simple method of increasing the calorific value of the residual waste.

In order to further limit the consumption of fossil fuels, at least one natural material is preferably admixed as combustible material. Suitable natural materials can be found

on the so-called biomass list.

A considerable increase in the calorific value with only a relatively small quantity of added material is achieved when at least one material with a high carbon content is admixed as combustible material.

In order to make the residual waste functioning as fuel easier to handle, at least one combustible binder is preferably admixed.

Optimal use of the energy present in waste is achieved when dust released during separation of the waste is admixed as combustible material.

In order to obtain a readily combustible product with a minimal addition of other substances, it will suffice when the mass ratio of the at least one residual fraction and the at least one combustible material is at least 1: 1. The mass ratio of the at least one residual fraction and the at least one combustible material preferably even lies between about 1.5 : 1 and 3: 1.

With a view to the mixing, the at least one residual fraction is preferably reduced in size for reprocessing purposes.

According to a second aspect of the invention, the at least one residual fraction is reprocessed by compressing thereof into granules. This compressing is also a simple manner of increasing the calorific value per unit of volume of the residual waste.

Both of the above stated measures of admixing and compressing are preferably combined, and the at least one residual fraction is compressed into granules after at least one combustible material has been admixed thereto. An optimal fuel product is thus obtained.

The invention also relates to an installation for processing waste with which the above described method can be

applied. A known waste processing installation, such as is for instance supplied by the above mentioned company Herhof Umwelttechnik GmbH, comprises an apparatus for collecting the waste, an apparatus connected to the collecting apparatus for separating the collected waste into at least one reusable fraction and at least one combustible fraction, and at least one apparatus connected to the separating apparatus for discharging the or each reusable fraction. In order to make this installation suitable for performing the above described method, it is provided according to the invention with at least one apparatus for reprocessing the or each combustible fraction.

Preferred embodiments of the waste processing installation according to the invention form the subject- matter of the dependent claims 14 to 21.

Finally, the invention further relates to a reprocessing apparatus for use in a waste processing installation of the above described type.

The invention is now elucidated on the basis of a number of examples, in which reference is made to the annexed drawing, in which: Fig. 1 is a flow diagram showing schematically the most important steps of the method according to the invention, Fig. 2 is a schematic representation of a reprocessing apparatus for use in a waste processing installation according to the invention, and Fig. 3-6 show a detailed flow and installation diagram of an embodiment of the invention recommended at the present time.

The processing of waste in the manner proposed by the invention starts with collection of the waste (fig. 1, block 1) which is then separated into one or more reusable

fractions R, for instance metals, glass and/or minerals, and one or more residual fractions, for instance a heavy and a light residual fraction and compost and/or wood (block 3). In order to simplify the separation, in the shown embodiment the waste is dried before the separating step (block 2), for instance to a dry matter-content of more than 80%. Once the reusable fractions R have been separated from the residual fraction (s), they are discharged to enable reuse. Up to this point the processing is substantially conventional.

In order to make the residual fraction (s) suitable for incineration in efficient manner, and thus be able to serve as replacement or additional fuel in power stations, the invention proposes reprocessing of the residual fraction (s). This reprocessing of the residual fraction (s) begins with reducing thereof in size.

This size reduction is important since a first aspect of the invention provides an increase in the calorific value of the residual fraction (s) by admixing combustible material C thereto (block 5). Once the combustible material C has been mixed with the reduced residual waste, according to a second aspect of the invention this mixture is then compressed into granules or pellets (block 6), whereby the calorific value per unit of volume increases still further.

The materials which according to the invention can be mixed with the residual fraction (s) of the waste in order to increase the calorific value thereof are of very diverse nature. Materials with a high carbon content can in the first place be added, for instance in the form of ground coke or pure carbon powder. In addition, combustible natural materials in accordance with the biomass list, for instance surplus agricultural products, can be added so as to increase the available quantity of fuel at low cost. In order to make a manageable whole from the different stated components, a binder can further be added. The table below gives an example of a possible mixing ratio.

Table 2

Material Granule t/yr Density Proportion size (mm) (kg/m 3) (%) Waste,-109380-58. 8 of which: - RDF 8 93600 260 50.3 - Compost/wood 10 15600 624 8.4 - Dust 1 180 184 0. 1 Corn, broken 5 44820 320 24.1 Carbon 1 31200 720 16.8 Oil (liquid) 700 800 0.4 (binder) Total 186100 260 100 This example assumes two residual fractions left over after separating of the reusable fractions R, i. e. an RDF fraction and a fraction with compost and wood. The RDF fraction, which contains particles of a size varying from 0 to 20 mm after the separation, is first reduced to a maximum particle size of 8 mm for mixing purposes. The compost/wood fraction is also reduced, for instance to a maximum size of 10 mm. Powdered carbon is used here as material with a high carbon content, while oil is added as binder. In addition, broken corn is admixed as natural combustible material. This embodiment further shows that dust which is extracted during the pretreatment steps, particularly during drying, separating and reducing in size, is collected again and added to the mixture.

An apparatus 10 for reprocessing the combustible

fraction (s) F to a product which can be used as fuel, for instance in a power station, comprises means 11 for admixing combustible material C to combustible fraction (s) F, and means 12 for compressing a thereby created mixture M of combustible waste F and combustible material C into granules (fig. 2). In the shown embodiment the admixing means 11 comprise a system for supplying and admixing the different materials, as well as a system for collecting and admixing in dust released during the pretreatments.

The system for supplying and admixing the natural material here comprises a dumping pit (not shown here) and an elevator 13 connecting thereto which transports the natural material, here the broken corn, to a silo 14. This silo 14 has on the underside an outlet opening which is closed by a dispensing valve 17. From this opening a conduit 15 with a branch 15a runs to two mixing bunkers 16 respectively 16a.

In similar manner the system for supplying and admixing the material with a high carbon content comprises a pneumatic transport conduit 18 and a silo 19. This silo 19 also has a dispensing valve 20 in the outlet opening and is connected to mixing bunkers 16 and 16a via a conduit 21 with a branch 21a.

The system for collecting and admixing dust comprises a number of extractors (not shown here), which are for instance placed at a drying apparatus, a separating apparatus and a size-reducing apparatus. Connected to these extractors is a pneumatic transport conduit 22, which in turn debouches into a silo 23. Silo 23 has in turn an outlet opening which is closed by a dispensing valve 24 and onto which connects a conduit 25 with branch 25a leading to mixing bunkers 16,16a.

Finally, a system for supplying and admixing the binder comprises a filling conduit 26, a tank 27 and conduits

28,28a leading to spray nozzles (not shown here) arranged above mixing chambers 16 and 16a.

The combustible residual fractions Fl, the RDF fraction and F2, the compost/wood fraction, are stored in trench silos (not shown here) after the drying, separating and reducing in size. Herefrom two supply/dispensing tanks 29,30 are filled using for instance a power shovel. The supply/dispensing tanks 29 respectively 30 are connected via conveyor belts 31 respectively 32 to weighing belts 33 respectively 39 which can be driven in two directions. The combustible residual fractions Fl, F2 are transported by means of these weighing belts 33,34 alternately to one of the two mixing bunkers 16,16a in the correct mixing ratio.

When one of the mixing bunkers 16,16a has thus been filled to a determined level with these combustible residual fractions Fl and F2, the other combustible materials are added from silos 14,19 and 23 in the desired ratios, whereafter the content of the relevant mixing bunker 16,16a is sprayed with binder from tank 27. While this is going on, the flows of material are directed to the relevant mixing bunker 16 or 16a by means of valves (not shown here) present at the position of the branches in conduits 15,21, 25 and 28.

When the relevant mixing bunker 16,16a has finally been filled in the correct ratio with the different materials, these are thoroughly mixed, for instance by means of a mixing gear (not shown here). Thus is created a determined quantity or batch of the mixture M of waste material and combustible materials to be used as fuel. When the batch has been fully mixed, the mixture M is carried by means of a discharge conveyor 35 respectively 35a to a collecting conveyor 36, for instance a chain conveyor. This carries the mixture M to one of three dispensing silos 37a-c,

from where it is divided in each case over two pellet presses 38a-f. In these presses 38 the mixture M is compressed into fuel granules or pellets, which are then discharged to a storage location (not shown here) by means of a discharge system 39, for instance a system of successive conveyors.

From here the fuel granules can be transported to a location of use, such as for instance a power station, where they can function as replacement or additional fuel.

During mixing of the material in the one mixing bunker 16 respectively 16a, the other mixing bunker 16a respectively 16 can already be filled again so that the method can ultimately be performed in practically continuous operation.

Another embodiment of the method according to the invention and the installation for performing thereof is shown schematically in fig. 3 to 6. Use is made here of three waste flows which are in principle combustible, i. e. wood (block 101), light domestic refuse such as paper and cardboard (PPK, block 201) and heavier domestic refuse (RDF, block 301).

The wood is reduced beforehand to an average size of about 200 mm and has a density of about 120 kg/m3 and a moisture content (after drying) of about 20%. It is supplied in loose form in containers. In this embodiment, which assumes a total waste supply of about 150,000 tonnes per year, the supplied quantity of wood amounts to about 20,000 tonnes per year, or 3.8 tonnes per hour.

The light (PPK) fraction of the waste has a density of about 150 kg/m3 and likewise a moisture content (after drying) of about 20%. This waste is also reduced beforehand to a size of about 200 mm. The supply of the light domestic refuse, which is supplied here in the form of compressed bales held together with wire or foil, amounts in this

embodiment to about 50,000 tonnes per year or 9.3 tonnes per hour.

Finally, the heavy (RDF) fraction of the domestic refuse has a density of about 200 kg/m3, a moisture content (after drying) of about 30% and is likewise reduced in size beforehand to pieces of about 200 mm. In the shown embodiment about 110,000 tonnes of this waste per year are supplied in loose form in pressing containers, or 21.2 tonnes per hour.

After being supplied by a chain conveyor (block 102 respectively block 202) the wood and the PPK waste are first further reduced in size; the wood such that 95% thereof is smaller than 40 mm and everything is smaller than 50 mm, and the PPK fraction until the size of 95% of the material is less than 150 mm and of all the material is less than 200 mm.

For this reducing step use is made of shredders from the firm Lindner-Recyclingtech in Spittal an der Drau (Austria), for the wood a Lindner Komet 1750 (block 103) and for the PPK fraction a Lindner Jupiter 2200 (block 203).

After the further size-reduction both the wood fraction and the PPK fraction are carried by a conveyor (block 104 respectively 204) to a station where ferrous metals are separated from the waste flow (block 105 respectively 205) by means of magnets placed above the conveyor. In the case of the wood fraction this is about 3% by weight of the waste flow, thus about 100 kg per hour, and in the case of the PPK fraction about 0. 5% by weight or 50 kg per hour. The separated ferrous metals are discharged (block 106 respectively 206) to a collection container (block 107 respectively 207).

The wood fraction which remains after separation of the ferrous metals, about 3.7 tonnes per hour, is carried to a further size-reducing station (block 112) by a sloping conveyor (block 108). Here the wood is reduced by means of a

Lindner Komet 2500 shredder to a particle size of a maximum of 10 mm, whereafter it is transported (block 113) to a drum dryer. In this drum dryer the moisture content is decreased to less than 5% (block 114), wherein about 15% by weight of the flow of wood waste, thus about 600 kg per hour of water, is separated. The flow of waste at the outlet of the drum dryer thus amounts to about 3.0 tonnes per hour.

After separation of the ferrous metals, the PPK fraction is carried by a vibrating trough to a subsequent separating station (block 208), where PVC is separated therefrom (block 209) by optical means by a negative NIR ("Near Infra Red") technique. The separated quantity of PVC, about 2% by weight or 185 kg per hour, is discharged (block 210) to a collection container (block 211). The remaining PPK fraction, still about 9.1 tonnes per hour, is further reduced in size until 95% thereof is smaller than 40 mm and the whole fraction is smaller than 50/60 mm, wherein use is once again made of a Lindner Komet 2500 (block 212). The further reduced PPK fraction is then also transported (block 213) to a drum dryer, where it is dried to a moisture content of less than 5% (block 214). The amount of water released here likewise amounts to about 15% by weight of the waste flow, or 1.4 tonnes per hour, so that after drying a quantity of about 7.7 tonnes per hour of PPK waste leaves the drum dryer.

The RDF fraction is carried from the pressing containers to a vibrating trough (block 308) using a chain conveyor (block 302), and then passes through a separating station where undesired material is separated from the RDF fraction (block 309) using a positive NIR technique. This undesired material, about 25% by weight of the RDF fraction or 6 tonnes per hour, is discharged (block 310) to a collection container (block 311). The remaining RDF fraction is divided into two flows of about 8.1 tonnes per hour each,

which are reduced in Lindner Komet 2500 shredders which are connected in parallel until 95% of the waste is smaller than 30 mm and the entire flow is smaller than 40/50 mm (block 312a, 312b). The reduced RDF fraction is then transported (block 313) to a drum dryer, in which it is dried to a moisture content of less than 5% (block 314). The water released therein, about 25% by weight of the waste flow, or 4 tonnes per hour, flows away and the dried RDF fraction is discharged from the drum dryer at about 12.2 tonnes per hour.

The dried wood, PPK and RDF fractions coming from the drum dryers are each transported further (block 115,215, 315) to a subsequent separating station, where even more ferrous metal is separated by making use of a neodymium magnetic drum (block 116,216, 316 respectively). Another 2% by weight or 100 kg per hour of ferrous metal is released from the wood fraction, 0.5% or 50 kg per hour from the PPK fraction, and 0. 1% or 120 kg per hour from the RDF fraction.

This separated ferrous metal is transported (block 117 217, 317 respectively) to a collection container (block 118,218, 318 respectively).

From the magnetic drum the wood, PPK and RDF fractions are carried by sloping conveyors (block 119,219, 319 respectively) to a subsequent separating station where the non-ferrous metals are separated by means of eddy-current techniques (block 120,220, 320 respectively). In the case of the wood fraction about another 1% of the remaining 3 tonnes per hour, thus about 30 kg per hour, is separated here. For the PPK fraction this is 2% of the remaining 7.65 tonnes per hour, thus about 150 kg per hour, and for the RDF fraction this is 0. 05% of the remaining 12 tonnes per hour, thus about 60 kg per hour. The thus separated non-ferrous metals are transported (block 121,221, 321) to collection containers (block 122,222, 322 respectively).

The remaining wood fraction, still about 3 tonnes per hour, is carried to a silo for intermediate storage (block 124) by a sloping conveyor (block 123). The PPK fraction, still about 7.5 tonnes per hour, and the RDF fraction, still about 12 tonnes per hour, are also discharged by sloping conveyors (block 223,323 respectively) to silos for intermediate storage (block 224,324 respectively).

From here these latter two fractions are carried to weighing belts (226,326) by screw conveyors (225,325), from where these flows are brought together in a buffer silo with mixing apparatus 400. The total supply to this silo thus amounts to about 19.5 tonnes per hour.

From buffer silo 400 the mixed PPK and RDF fractions are divided over two discharge screws 401a, 401b, which each discharge about 9.75 tonnes per hour to a pneumatic transporting and dividing system 402. The combined waste flow is there divided into six sub-flows, each of 3.25 tonnes per hour, which are first compressed in agglomerators 403a-f and then reduced to a very fine particle size of less than 5 mm in shredders 404a-f. From these shredders the sub- flows are brought together in a pneumatic transporting system 405, whereby they are transferred to an intermediate silo 406.

The PPK and RDF fractions which have been reduced in size so much and are stored in silo 406 and the reduced wood fraction in silo 124 are then reprocessed by admixing combustible material and binder and compression into pellets.

For this purpose a quantity of about 7.5 tonnes per hour of ground green coke is carried to a silo 502, while a quantity of about 300 kg per hour of binder is transported to a silo 602 from another supply (block 601).

From this silo 602 the binder, with a density of about 750 kg/m3 and a particle size of a maximum of 1 mm, is

carried by a discharge screw 603 to a weighing and dispensing apparatus 700. From silo 502 the reduced green coke, with a density of about 400 kg/m3 and a particle size of a maximum of 2 mm, is likewise carried by a discharge screw 503 to weighing and dispensing apparatus 700. The reduced wood from silo 124, with a density of about 250 kg/m3, is also carried to weighing and dispensing apparatus 700 by a discharge screw 125, just as the mixed PPK and RDF fraction with a density of 300 kg/m3, which runs through a discharge screw 407 to weighing and dispensing apparatus 700.

This weighing and dispensing apparatus 700, with a capacity of about 5 m3, can process about 30 tonnes or 100 m 3 per hour. On the underside of weighing and dispensing apparatus 700 is arranged a valve 701 which closes an outlet opening. By operating the valve 701 a quantity or batch is delivered to a mixing apparatus 702, with a mixing volume of also 5,000 litres. This mixing apparatus can mix 20 batches per hour.

From mixing apparatus 702 the mixed batches are transferred to a delivery silo 703, and from here divided via conveyors 704a, 704b between two intermediate silos for mixed half-finished product 705a, 705b. From these silos 705a, 705b the mixture is divided by discharge screws 706a, 706b over six pellet presses 707a-f, which are connected in parallel and each have a pressing or pelletizing capacity of about 5 tonnes per hour. The fuel pellets or granules are then carried further by a pneumatic transporting system 708 and divided over three cooling apparatuses 709a-c, each with a capacity of 10 tonnes per hour, in which the pellets are cooled. The cooled pellets are then carried further by a pneumatic transporting system 710 and divided over four silos 711a-d for the finished product, i. e. the cooled fuel pellets. From these silos 711a-d the fuel pellets are

transported by means of trucks to the final locations of use.

The composition of the mixture compressed into fuel granules according to this embodiment is shown in the table below.

Table 3 Material Granule t/h Density Proportion size (mm) (kg/m 3) (o) Waste,-22. 5-74. 3 of which: - PPK + RDF 5 19.5 300 64.4 (PPK) 7.5 (24.8) (RDF) 12.0 (39.6) - wood 10 3.0 250 9.9 green coke, 2 7.5 450 24.8 ground binder 1 0. 3 750 1.0 Total 30.3 100 Using relatively simple means the method and installation according to the invention thus enable the reprocessing of non-reusable, low-grade waste into a high- grade fuel which can be used in power stations. The invention thus contributes toward solving three increasingly urgent problems, i. e. the problem of processing waste not suitable for reuse, the problem of the imminent shortage of fossil fuels, and the problem of climate changes resulting from the emission of greenhouse gases.

Although the invention is described above on the basis of a number of embodiments, it will be apparent that the invention is not limited thereto. The scope of the invention is defined solely by the following claims.