EP0563173A1

EP0563173A1 - Method of treating waste and improved press for implementing said method.

Info

Publication number: EP0563173A1
Application number: EP92901634A
Authority: EP
Inventors: Pierre Dumons
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-12-21
Filing date: 1991-12-12
Publication date: 1993-10-06
Anticipated expiration: 2011-12-12
Also published as: FR2670711A1; FR2670711B1; AU9128791A; ES2065162T3; US5400726A; EP0563173B1; WO1992011132A1; AU655620B2; JPH06504478A; DK0563173T3; DE69104500T2; ATE112519T1; CA2097832A1; DE69104500D1

Abstract

L'invention concerne un procédé de traitement d'ordures ou déchets consistant (a) à soumettre lesdits ordures ou déchets à une compression supérieure à 800 bars dans des conditions propres à en séparer la fraction fermentescible humide et la fraction combustible solide, (b) à valoriser ensuite chacune de ces deux fractions séparément, d'une part, pour la fraction fermentescible, par des traitements spécifiques tirant partie de sa nature de biomasse, d'autre part, pour la fraction combustible, par combustion en vue de la production d'énergie. Le procédé de l'invention permet de réaliser une valorisation des ordures ou déchets dans de remarquables conditions de rentabilité. L'invention s'étend à une presse perfectionnée réalisant l'opération de compression en deux phases successives: une phase de précompression jusqu'à une pression intermédiaire (200 à 300 bars) et une compression finale jusqu'à la pression finale supérieure à 800 bars.The invention relates to a method for treating garbage or waste consisting of (a) subjecting said garbage or waste to a compression greater than 800 bars under conditions suitable for separating therefrom the wet fermentable fraction and the solid combustible fraction, (b) then recovering each of these two fractions separately, on the one hand, for the fermentable fraction, by specific treatments taking advantage of its nature as biomass, on the other hand, for the combustible fraction, by combustion for the production of 'energy. The method of the invention makes it possible to recover garbage or waste under remarkable conditions of profitability. The invention extends to an improved press performing the compression operation in two successive phases: a precompression phase up to an intermediate pressure (200 to 300 bars) and a final compression up to the final pressure greater than 800. bars.

Description

PROCESS FOR TREATING GARBAGE OR WASTE AND IMPROVED PRESS FOR IMPLEMENTING IT

The invention relates to a method for treating garbage or waste, in particular household waste collected directly or indirectly by public authorities or assimilable industrial waste composed of a mixture of combustible and fermentable materials. The invention extends to an improved press suitable for implementing the above-mentioned method.

It is currently usual to receive raw garbage or waste in treatment centers after a simple compaction operation which facilitates transport. It is already known according to DE-OS 27 53 920, in addition to this first compaction, to carry out in a compression chamber, multiple compressions using a plurality of pistons inserted and then removed one after the other from the compression chamber. Each of the pistons is of smaller section than that of the chamber and only partially collects the garbage located in this chamber. To obtain correct pressing of the refuse, it is necessary to multiply the number of pistons and to control their action over time so that all the refuse located in the chamber is in turn compressed. Such a device is expensive and complex to implement.

Generally, in waste treatment centers, inert materials, such as metals, iron, etc. are extracted and the remaining waste is recovered, essentially by two types of technique.

A first type of recovery consists of incinerating garbage or waste in order to recover heat energy used for the production of pressurized water vapor (usable for district heating, for local industrial consumption, for the needs of communities ⁿ u li ^π ues ... or even for the production of electrical energy by turbo-generator groups). However, this incineration as it is currently practiced has several shortcomings. First, the overall yield of recovery is poor and generally results in a relatively high financial burden for local authorities, given the importance of the amortization of investments with regard to the low level of effective recovery of heat energy. In addition, raw garbage must be treated immediately and the recovery record is further deteriorated by the mismatch in time between the arrival of garbage and periods of high energy needs. In addition, the low profitability of this recovery means limiting costs and incineration is currently carried out in grate ovens: without superheaters it is not possible with this type of equipment to meet the recent pollution standards imposed in most industrialized countries, both for solid residues which must contain very little unburnt matter and be non-polluting as for gaseous discharges which must be clean (for example, for EEC standards, to be able to maintain a temperature of more than 850 ° C for more than two seconds).

Another way of recovering waste consists in taking advantage of the biomass they contain to produce, by fermentation, composts, organic fertilizers or gases. However, recovery processes of this type are ill-suited to the treatment of the above-mentioned raw refuse, composed of a mixture of fermentable and combustible materials, and this handicap increases every year in industrialized countries due to the sharp increase in the percentage of non-fermentable waste materials.

Consequently, there is at present no satisfactory solution which makes it possible to treat garbage or raw waste so as to both respect the pollution standards relating to discharges and to recover these materials under good conditions of profitability.

The present invention proposes to provide a solution constituting a considerable advance over the techniques which are implemented at present.

An object of the invention is thus to indicate a method for treating garbage or waste which allows better recovery of these with good profitability of the installations used and is compatible with compliance with anti-pollution standards. The process in accordance with the present invention applies after optional extraction of the inert materials and consists of:

- subjecting said refuse or waste to compression up to a final pressure (P ^) greater than 800 bars under conditions suitable for extracting a fermentable fraction in the form of wet pulp and in separating a solid combustible fraction, of moisture relative less than 20%; said compression of the refuse or waste being ensured in two successive phases in a chamber provided, on the one hand, with extrusion orifices for the fermentable fraction, on the other hand, with an outlet for the combustible fraction:

. a precompression phase operated by means of a long stroke piston moving in the chamber so as to exert a pressure (P ^) lower than the final pressure (P _f ) on all of the materials located in the chamber,

. a final compression phase, operated by means of a shorter stroke piston moving in the chamber opposite the first piston so as to exert the final pressure (P) on all the materials located in the chamber, and

- to then develop each of these two fractions separately, on the one hand, for the fermentable fraction, by specific treatments, known per se, taking advantage of its biomass nature with a view in particular to the production of organic products or gases , on the other hand, for the fuel fraction, by combustion for the production of energy, if necessary after a storage time.

It has been observed that the compression operation at the very high pressures mentioned above, in particular between 900 and 1050 bars, made it possible to separate the fermentable materials from the refuse with a yield greater than 95%, consisting essentially of biomass, and combustible materials of low relative humidity, in particular between 6% and 12%. After such compression, these combustible materials no longer have cohesion and tend to disintegrate by themselves into particles, which makes them particularly well suited for undergoing incineration (especially in kilns with fluidized bed circulating as indicated below).

After this separation, the incineration of combustible materials is carried out under optimal conditions of yield, since the considerable energy losses which encumber known processes are eliminated, losses resulting from the energy consumption brought about by the dehumidification of refuse and by the destruction of the biomass.

Because of its very low relative humidity and the absence of biomass, the combustible fraction collected at the end of the compression operation lends itself to profitable incineration in ovens of the circulating fluidized bed type, known per se, under conditions meeting standards, in terms of combustion discharges. These ovens, associated with steam-generating boilers, thus make it possible to produce superheated steam, by optimally exploiting the calorific value of the combustible fraction of garbage or waste.

In addition, this combustible fraction, free from humidity and biomass, can be stored for an indefinite period without any nuisance, in particular in heaps in open air areas, to be used by combustion during periods of very high energy demands.

Furthermore, the fermentable fraction freed from non-fermentable materials can, for its part, be treated under optimal conditions by known methods, in particular by biological seeding and fermentation in order to produce composts, organic fertilizers or gases capable of provide heat energy.

Advantageously, the method according to the invention is carried out in two successive phases, namely: precompression then final compression. The pre-compression phase can in particular be carried out so as to reach an intermediate pressure (P ^ between 200 and 300 bars, and the final compression phase so as to reach a final pressure

(P) between 900 and 1050 bars.

The implementation of compression in two phases as defined above makes it possible to easily reach very high final pressures (of the order of 1000 bars) with reliable equipment and of moderate cost; the long stroke piston is specialized for exerting moderate pressures (common pressures from 200 to 300 bars), while the reduced stroke piston is specialized for very high pressures (of the order of 1000 bars): due to its short stroke, the cost of this piston is compatible with a moderate overall price of the installation, while the other piston is achievable at low cost by current technologies.

The present invention extends to an improved press, suitable for carrying out, under good conditions, the compression operation defined above. This press has the following means, already known from patent FR No. 2,577,167:

means for loading materials into a loading chamber having two opposite lateral openings, one called the upstream opening, the other called the downstream opening,

an extrusion chamber located in the extension of the loading chamber and opening into the latter at its downstream opening, this extrusion chamber being provided with extrusion orifices on its periphery and an outlet located at opposite to the loading chamber,

- two coaxial pistons located, in the retracted position, respectively on one side and the other of the assembly formed by the loading cylinder and the extrusion chamber, the first piston being arranged to move between a retracted position where its end is located in the vicinity of the upstream opening of the loading chamber and an extreme deployed position where it passes through the loading and the extrusion chamber with its end situated in the vicinity of the outlet of the latter, while the second piston is arranged to move between a retracted position set back from the extrusion chamber so as to release the exit from it and an extreme deployed position,

- Hydraulic means for operating the pistons in a deployment movement directed respectively towards the loading chamber or towards the extrusion chamber, and in an opposite retraction movement.

The press according to the present invention is characterized in that:

. the second piston, of shorter stroke than that of the first piston, is adapted to be able to exert pressures higher than those of the first piston,

. the second piston is arranged so that, in its extreme deployed position, it enters the extrusion chamber over a determined length thereof in order to ensure final compression of the materials,

. mechanical locking means located upstream of the loading chamber are associated with the first piston in order to be able to prevent its recoil from an intermediate deployed position in which it passes through the loading chamber and partially penetrates into the extrusion chamber.

Thus, in the press according to the invention, the two pistons are specialized for fulfilling different specific functions, namely: for the first piston, a function of loading the extrusion chamber with shearing at the inlet thereof ci, then a function of precompressing the materials up to a moderate intermediate pressure P _i (in particular of the order of 250 bars), finally a function of ejecting the solid fraction compressed at the end of the cycle; for the second piston, a shutter function of the extrusion chamber and a final compression function from the intermediate pressure to a very high pressure (in particular of the order of 1000 bars). The migration and the extrusion of the liquid or semi-liquid fraction begin during the precompression phase; the compression phase The final which follows ensures a remarkably efficient extraction of this fraction (fermentable materials) until separation yields greater than 95% are achieved and a relative humidity of the remaining solid materials (combustible fraction) of less than 12%.

Before the implementation of the second piston, the first piston is mechanically locked so that the reaction forces are supported by mechanical members and not by the hydraulic members of this piston. It is thus possible to exert on the materials the very high final pressures mentioned above, without the hydraulic means of the first piston being subjected to the rigorous technical requirements that require pressures of this order. According to a preferred embodiment, these mechanical locking means comprise:

. at least one pincer with two jaws situated at the periphery of the first piston upstream of the loading chamber,. a fixed stop serving as a longitudinal support for the pincer jaws,

. a shoulder formed on the circumference of the first piston and arranged to come opposite the jaws when this piston reaches its intermediate deployed position,. means for operating the pincer jaws, adapted to ensure their opening towards a position set back relative to the circumference of said piston or to allow them to be closed behind the shoulder of the piston. According to another characteristic of the invention, the press advantageously comprises control means adapted to condition the following operating cycle, from an initial position where the pistons are in the retracted position and the pincer jaws in the open position:

. de p l o i e m ent part i e l du se c o n d p i s t on until the outlet of the extrusion chamber is closed,

. the materials being loaded, deployment of the first piston first in the loading chamber to push the mass contained therein towards the chamber extrusion, then in said extrusion chamber to ensure the precompression phase,

. stop of the first piston and closing of the pincer jaws when the pressure reaches the intermediate value (P ^), deployment of the second piston in the extrusion chamber until reaching the final pressure (Pf) in order to ensure the phase of final compression,. withdrawal of the second piston to its retracted position in order to free the outlet from the extrusion chamber,

. deployment of the first piston to its extreme deployed position to eject the compressed solid mass.

Other characteristics, objects and advantages of the invention will emerge from the description which follows with reference to the appended drawings, which illustrate the process of the invention and present, by way of nonlimiting example, an embodiment of an improved press. for its implementation; on these drawings which form an integral part of this description:

FIG. 1 is a diagram illustrating the method of the invention, FIG. 2 is a vertical section of an improved press according to the invention,

- Figure 3 is a schematic view showing said ^* press and its control means and detecting means, - Figure 4 is a sectional detail of one of said press members (means of mechanical lock)

FIGS. 5a and 5b are detailed front views showing said locking means in the closed position and in the open position respectively,

- Figures 6, 7 _> 8, 9, 10 and 11 are schematic views showing the essential steps of the press operating cycle. Figure 1 illustrates the implementation of the process of the invention which applies in particular to the treatment of household waste but also to any assimilable waste comprising combustible materials and fermentable materials, in particular certain industrial waste. These materials will be referred to below as "raw waste".

This raw waste is collected (COLLECT) and delivered to the treatment center at rates imposed by the outside environment, for example daily for household waste.

Conventionally, when the waste contains inert materials such as metals, glasses, etc., these are extracted by a pre-treatment (EXTRACT). The waste is then subjected to a compression operation (PRESS) until it undergoes a final pressure of the order of 1000 bars, having the effect of separating:

. a pulp composed of biomass (BIO), moist and fermentable, expelled under the effect of high pressure through extrusion orifices of the press (symbolized by -Ex-),

. a dry residue (COMB) of relative humidity of less than 12% (between 6 and 12%), very fragmented, composed of shreds of combustible materials of very low cohesion.

The fermentable fraction can be shipped or kept on site to be processed within the time required to take advantage of its relatively pure biomass quality; it is subjected to specific treatments (T.S.) known per se, which become economically profitable due to the absence of combustible solid materials, such as:

- organic seeding and fermentation to make composts, - pre-drying, organic seeding, maturation, drying, granulation to make organic fertilizers,

- biological treatment in a gasometer to manufacture gaseous hydrocarbons with a view in particular to energy production by combustion. The combustible fraction (COMB) can either be directly and immediately incinerated in a furnace-boiler, or stored outside in indefinitely thick thick layers (STOCK) to be then taken up and incinerated during periods of high energy demand.

The characteristics of these combustible materials (very low humidity, absence of biomass, particulate form without cohesion) make it possible to incinerate them in the best conditions in a furnace-boiler of the circulating fluidized bed furnace type (F) associated with a boiler (CH) steam generator. This type of oven is known per se and is characterized in that the support of the mass to be burned consists of a bed of fluidized sand; it is thus possible to reach (without superheaters) very high smoke temperatures (above 850 ° C) and to achieve clean combustion with excellent efficiency. The parceled heavy ashes (C-i) can be used as filling material (road foundations, inert fillings, etc.). The high temperature fumes pass through the steam producing boiler (CH) and are subjected to a treatment to separate the fly ash (C2). The steam produced (VAP) can be used for all purposes depending on economic interest and the industrial or urban environment (direct use or production of electrical energy).

Thus the method of the invention leads to an optimal recovery of garbage or waste thanks to a thorough separation of two fractions of different nature, allowing to exploit the specific characteristics in the best conditions.

Figures 2, 3 _. 4, 5a and 5b represent an improved press intended to ensure this advanced separation of the two fractions.

This press rests on a frame 1 and comprises conventional chassis elements (such as tie rods,.,) Which hold the functional members relative to one another (cf. patent FR n ° 2.577.167 already mentioned). A loading hopper 2 equipped with a conventional gland system 3 ensures that the waste is compacted and introduced into a chamber 4, called the loading chamber. This axis chamber horizontal and of cylindrical section has two opposite lateral openings: an upstream opening 4a and a downstream opening 4b. A chamber 5, called the extrusion chamber, coaxial with the loading chamber 4 opens into the latter at its downstream opening 4b; a cutting edge situated in the plane of this opening ensures shearing of the materials in the event of partial penetration into the extrusion chamber.

The extrusion chamber 5 is delimited by a perforated jacket which has a plurality of extrusion orifices 5a on its periphery; these orifices have in particular a diameter between 4 and 40 mm, in particular of the order of 10 mm, and open out into a collector 6 which delivers the liquid and semi-liquid extruded materials to a conveyor 7.

In addition, the extrusion chamber 5 has, opposite the loading chamber, an outlet 5b of the solid fraction, of diameter substantially equal to that of said extrusion chamber. A conveyor 8 receives the solid material at the outlet and routes it out of the press.

In addition, in the example, a guillotine 9 is located at the outlet of the extrusion chamber; this guillotine associated with maneuvering means such as vertical cylinder, can be brought to sweep the exit plane of said chamber in order to clean by friction said exit and, if necessary, to disaggregate the compact blocks.

Furthermore, the press comprises two coaxial pistons 10 and 11 which, in the retracted state, are arranged on one side and on the other of the assembly formed by the loading chamber 4 and compression chamber 5; these pistons are guided in a conventional manner by bodies and sleeves such as 10a and 11a, and associated with hydraulic means (symbolized in 12 and 23) with a view to their displacement in a rolling movement along the common horizontal axis of the two bedrooms 4 and 5.

The first piston 10 is of the long-stroke type (of the order of 220 cm) capable of transmitting current pressures of the order of 250 bars; he can be operated by the hydraulic means 12 between an extreme retracted position where its end is located at the upstream opening of the loading chamber (Figure 2) and an extreme deployed position where its end is located at the outlet of the chamber extrusion (Figure 11).

This piston 10 has on its circumference a shoulder 13 delimiting a front section of section larger than its rear section. This shoulder is arranged to come to cooperate with mechanical locking means 14 adapted to allow the recoil of said piston to be prevented from an intermediate deployment position in which this piston crosses the loading chamber and partially penetrates into the extrusion. These locking means are shown in detail in Figures 4, 5a, 5b; they comprise a succession of pincer jaws such as 15, which are juxtaposed close to each other and articulated around a fixed axis 16. The two jaws of each pincer 15 are extended by branches 17 whose rounded ends 17a come lodge in support troughs formed at their base by two plates 30; these plates are coupled to two actuating cylinders 18. In the deployed position of these cylinders 18 (FIG. 5a), the jaws close by their weight towards the piston 10, while, in the retracted position of these cylinders (FIG. 5b) , said jaws are raised and open, that is to say set back relative to the cylindrical surface of the piston 10.

A fixed stop 19 is located at the rear of the jaws 15 to serve as a longitudinal support for the latter in order to support the reaction forces transmitted by the jaws. This annular stop is arranged so as to allow the passage of the piston 10 in its largest section, while serving as longitudinal support for the closed jaws; the last jaws (jaws located in contact with said stop) are subjected to high shear and bending forces and are provided with an appropriate thickness greater than that of the others.

The shoulder 13 is positioned along the piston 10 so that it comes opposite the jaws 15 when the piston 10 having entered the extrusion chamber

5 is between two predetermined deployment positions

(penetration into the extrusion chamber over a predetermined depth range).

As shown schematically in Figure 3, the piston 10 are associated with longitudinal position detection means 20, which deliver a position signal S _j when said piston is located between these two deployment positions (which correspond to the passage of the shoulder 13 at the locking jaws 14). This position signal is delivered to control means symbolized at 21, adapted to condition the operating cycle of the press, which will be described later. In addition, pressure detection means symbolized at 22 are associated with this first piston 10 (and more precisely with its hydraulic means 12) with a view to delivering to the control means 21, a pressure signal S _i when the pressure applied on said first piston reaches a predetermined intermediate value P. _j _ (of the order of 200 to 300 bars, for example equal to 250 bars); this signal is intended to trigger a stop command for said piston when the latter is subjected to this intermediate pressure.

Furthermore, the second piston 11 is of the type with reduced stroke (of the order of 50 to 60 cm) capable of transmitting very high pressures, of the order of 1000 bars. This piston and its hydraulic means require special manufacture, but its reduced stroke makes the cost compatible with good economic profitability of the press. This second piston 11 can be maneuvered by the hydraulic means 23 between an extreme retracted position where its end is set back relative to the extrusion chamber 5 so as to release the outlet from the latter (FIG. 2) and a position extreme deployed where it enters the extrusion chamber over a predetermined length (FIG. 10) in order to ensure the final compression of the materials at the final pressure Pf ( ^of the order of 900 to 1050 bars, for example equal to 1000 bars ).

As shown in FIG. 3, at the second piston 11 (and more precisely at its hydraulic means), are associated with pressure detection means, symbolized at 24, adapted to deliver to the control means 21 a stop signal S _f when the pressure applied to said second piston reaches the final value P ^.

The control means 21 are in the example constituted by a programmable automaton which is programmed to send control signals to distributors 25, 26, 27 and 28, with a view to ensuring the running of the operating cycle, by a power supply appropriate hydraulic means for operating the first piston 10, actuators for operating the locking jaws 15, hydraulic means for operating the second piston 11 and the actuating cylinder for the guillotine 9. The controller 21 is in particular programmed to condition the operating cycle illustrated in Figures 6 to 11 and described below.

The press is assumed to be in the following initial position: first piston 10 and second piston 11 in the fully retracted state, locking jaws 15 open, guillotine 9 raised.

First, the second piston 11 is partially deployed until the outlet 5b of the extrusion chamber is closed (FIG. 6). With the hopper 2 loaded, the raw materials are compressed in the loading chamber

4 by the gland system 3.

The first piston 10 is deployed in the loading chamber 4 and pushes the mass contained therein towards the extrusion chamber (Figure 7). The first piston 10 continues to advance and its end reaches the level of the downstream opening 4b; the materials are sheared by the cutting edge located around this opening (figure 8).

The first piston 10 enters the extrusion chamber 5 and provides a material precompression phase between its end and that of the second piston 11 which closes the outlet 5b of the extrusion chamber. When the first piston arrives between the two deployment positions mentioned above, the detection means 20 deliver the position signal S- _j _ to the control means 21; the shoulder 13 is then located opposite the locking jaws 15; in the absence of an incident and for materials of normal consistency, the intermediate pressure? is exerted on the piston 10 when the latter is between these two deployment positions and the pressure signal S. _j _ is delivered by the detection means 22. In the presence of the pressure signal S ^ and the position signal Sη_, the automaton controls the stopping of the piston 10 and the deployment of the jacks 18 which release the locking jaws 15 and allow them to close (FIG. 9). The recoil of the first piston 10 is then blocked by the jaws which have closed at the rear of the shoulder 13 (the reaction being transmitted to the fixed stop 19). The second piston 11 is then deployed in the extrusion chamber 5 in order to ensure the final compression phase (Figure 10). When the final pressure P _f is reached, a stop signal S ^. is delivered and the automaton 21 controls, on the one hand, the stopping of the second piston, on the other hand, maintaining said second piston in its stopped position for a predetermined period, for example of the order of 2 seconds. The expulsion of liquid and semi-liquid materials thus becomes final, without risk of aspiration of these materials towards the solid mass by the effect of phenomena of relaxation of this mass.

The withdrawal of the second piston 11 is then controlled to its retracted position in order to release the outlet 5b from the extrusion chamber, then the first piston 10 is caused to deploy fully to eject the compressed solid mass (FIG. 11) . Guillotine 9 can be operated during or after this ejection.

Furthermore, the control automaton 21 is programmed to trigger an alarm 29 (FIG. 3) and the stopping of the first piston 11, in the event of an incident during the precompression phase determining the premature application of the intermediate pressure P _j _ on the first piston (appearance of the pressure signal Si before that of the position signal S- ^). An operator can thus examine the cause of this anomaly (jamming of an object ...) and remedy it. On the contrary, if the extrusion chamber 5 is insufficiently charged or if the consistency of the materials is lower than normal, the position signal S _j disappears while the pressure signal S _i has not appeared: the control automaton 21 is programmed to generate in this case a retraction of the first piston 10 when the position signal S _j disappears, then the course of a new operating cycle, and this, until simultaneously obtaining the position signal S ^ and the pressure signal S _j _. This avoids performing unnecessary final compression phases (slow phases, consuming energy and causing higher wear); moreover several round trips of the first piston 10 carry out successive precompressions and relaxations of the materials and increase the separation efficiency of the two fractions, combustible and fermentable.

Claims

CLAIMS 1 / - Method for treating garbage or waste, after possible extraction of inert materials, characterized in that it consists:

- subjecting said refuse or waste to compression up to a final pressure (P ^) greater than 800 bars under conditions suitable for extracting a fermentable fraction in the form of wet pulp and in separating a solid combustible fraction, of moisture relative less than 20%; said compression of garbage or waste being ensured in two successive phases in a chamber (5) provided, on the one hand, with orifices (5a) for extruding the fermentable fraction, on the other hand, with an outlet (5b ) of the combustible fraction:

. a precompression phase operated by means of a long stroke piston (10) moving in the chamber so as to exert a pressure (P _^ ) lower than the final pressure (P _f ) on all the materials located in the bedroom,

. a final compression phase, operated by means of a shorter stroke piston (11) moving in the chamber opposite the first piston so as to exert final pressure (P ^) on all of the materials located in the room, and

2 / - Method according to claim 1, characterized in that, at the end of the precompression phase, the long-stroke piston (10) is stopped and it is mechanically locked so as to prevent its recoil, then the the movement of the shorter stroke piston (11) is controlled to operate the final compression phase. 3 / - Method according to claim 2, characterized in that the stop and the mechanical locking of the long-stroke piston (10) are ensured when the pressure applied to said piston reaches a predetermined intermediate value (P_) lower than the value of the final pressure (P _f ) .

4 / - Method according to claim 3, characterized in that the precompression phase is carried out so as to reach an intermediate pressure (P _i ) between 200 and 300 bars, and the final compression phase so as to reach a final pressure (P ^.) Between 900 and 1050 bars, the combustible fraction having a relative humidity between 6% and 12%.

5 / - Method according to one of claims 1, 2, 3 or 4, characterized in that the compression is carried out in a chamber (5) having extrusion orifices (5a) of diameter between 4 and 40 mm and an outlet (5b) of combustible fraction of diameter substantially equal to that of said chamber. 6 / - Method according to one of claims 1 to 5, wherein the combustion of the combustible fraction is carried out in an oven of the circulating fluidized bed type, known per se.

7 / - A method according to claim 6, wherein the combustion of the combustible fraction is used to produce superheated steam, the circulating fluidized bed furnace being associated with a steam generating boiler.

8 / - Method according to one of claims 1 to 7 for the treatment of garbage and waste collected and delivered at rates imposed by the external environment, characterized in that the compression of said garbage or waste is carried out as and deliveries, the fuel fraction being stored for recovery by combustion during periods of high energy demand, while the fermentable fraction is recovered within the time required by the specific treatments to which it is subjected.

9 / - A method according to claim 8, wherein the combustible fraction is stored in heaps in open air areas. 10 / - Press for the treatment of materials, in particular garbage or waste, comprising:

means (2, 3) for loading materials into a loading chamber (4) having two opposite lateral openings, one said upstream opening (4a), the other called downstream opening (4b),

an extrusion chamber (5) located in the extension of the loading chamber (4) and opening into the latter at its downstream opening (4b), this extrusion chamber being provided with extrusion orifices ( 5a) on its periphery and an outlet (5b) located opposite the loading chamber,

- two coaxial pistons (10, 11) located in the retracted position, respectively on one side and the other of the assembly formed by the loading chamber and the extrusion chamber, the first piston (10) being arranged to move between a retracted position where its end is located in the vicinity of the upstream opening (4a) of the loading chamber and an extreme deployed position where it passes through the loading chamber (4) and the extrusion chamber (5 ) with its end located near the outlet (5b) of the latter, while the second piston (11) is arranged to move between a retracted position located back from the extrusion chamber (5) so to release the outlet (5b) from the latter, and an extreme deployed position,

- hydraulic means (12, 23) for operating the pistons in a deployment movement directed respectively towards the loading chamber or towards the extrusion chamber, and in an opposite retraction movement, said press being characterized in that:

. the second piston (11), of shorter stroke than that of the first piston (10), is adapted to be able to exert pressures higher than those of the first piston,

. the second piston (1 1) is arranged so that, in its extreme deployed position, it enters the extrusion chamber (5) over a determined length thereof in order to ensure final compression of the materials, . mechanical locking means (14) located upstream of the loading chamber (4) are associated with the first piston (10) in order to prevent its recoil from an intermediate deployed position in which it passes through the loading and partially enters the extrusion chamber.

11 / - Press according to claim 10, characterized in that the mechanical locking means (14) comprise:

. at least one pincer with two jaws (15) situated at the periphery of the first piston (10) upstream of the loading chamber (4), a fixed stop (19) serving as longitudinal support for the pincer jaws, a shoulder ( 13) formed on the circumference of the first piston (10) and arranged to come opposite the pincer jaws (15) when this piston reaches its intermediate deployed position,. means (18) for maneuvering the pincer jaws, adapted to ensure their opening towards a recessed position relative to the circumference of said piston, or to allow their closing at the rear of the shoulder (13) of the piston. 12 / - Press according to claim 11, characterized in that:

. the locking means comprise a succession of juxtaposed pincer jaws (15),

. pressure detection means (22) associated with the first piston (10) for delivering a pressure signal (S ^ when the pressure applied to said first piston reaches a predetermined intermediate value (P ^), control means being provided for causing said first piston to stop when said pressure signal appears 13 / Press according to one of claims 11 or 12, characterized in that it comprises control means (21) adapted to condition the cycle of following operation, from an initial position where the pistons (10, 11) are in the retracted position and the pincer jaws (15) in the open position: . partial deployment of the second piston (11) until the outlet (5b) of the extrusion chamber is closed,

. the materials being loaded, deployment of the first piston (10) first in the loading chamber (4) to push the mass contained therein towards the extrusion chamber (5), then in said extrusion chamber to ensure a precompression phase,

. stop of the first piston (10) and closing of the pincer jaws (5) when the pressure has reached the intermediate value (P. ^),

. deployment of the second piston (11) in the extrusion chamber (15) until a predetermined final pressure (Pf) is reached in order to ensure a final compression phase,

. withdrawal of the second piston (11) to its retracted position in order to release the outlet (5b) from the extrusion chamber,

. deployment of the first piston (10) to its extreme deployed position to eject the compressed solid mass.

14 / - Press according to claims 12 and 13 taken together, characterized in that:

- Longitudinal position detection means (20) are associated with the first piston (10) to deliver a position signal (S- ^ when, after penetration into the extrusion chamber, said first piston is located between two positions of predetermined deployment,

- the control means (21) are adapted to stop the first piston (10) and cause the jaws (15) to close in the presence of the pressure signal (S _j _) AND the position signal (S ^), and for generate a retraction of said first piston, then the course of a new operating cycle if the pressure signal (S. :) has not appeared when the position signal (S _j ) disappears.

15 / - Press according to claim 14, characterized in that the control means (21) are adapted to trigger an alarm (29) and the stop of the first piston (10) when the pressure signal (S _) appears before appearance of the position signal (Si). 16 / - Press according to one of claims 13, 14 or 15, characterized in that:

. pressure detection means (24) are associated with the second piston (11) for delivering a stop signal (S _* -) when the pressure applied to said second piston reaches a predetermined final value (Pf),

. the control means (21) are adapted to generate, on the one hand, the stopping of the second piston (11) when the stop signal appears, on the other hand, keeping said second piston in its stopping position for a predetermined period.

17 / - Press according to one of the claims

10 to 16, characterized in that it comprises a guillotine (9) located at the outlet from the extrusion chamber (5) and operating means associated with said guillotine in order to cause it to sweep the outlet plane from said room.

18 / - Press according to one of the claims

10 to 17, characterized in that the first piston (10) is adapted to be able to exert on the materials a pressure (P _i ) of the order of 250 bars, and the second piston (11) a pressure

(P _f ) of the order of 1000 bars.