EP0426925B1 - Process and installation for the treatment of municipal and industrial wastes - Google Patents

Abstract

According to the process of the invention the waste to be treated is dehydrated beforehand in a closed drying enclosure (1), the gases (16) produced during the drying are recovered in a circuit closed to the atmosphere and these gases are subjected to a purification stage (17, 12), at least a part of the said purified gases (11) is reinjected into the plant as drying agents and the excess noncontaminating gases are discharged to the outside. In addition, the thermolysis reaction is conducted at low temperature, of the order of 400 to 450 DEG C, in an insulated and controlled thermolysis chamber (2), the gaseous products originating from the thermolysis reaction are recovered and treated in circuits (4, 33) which are closed to the atmosphere, in which the combustible gaseous components are separated from the tars in the gaseous state and the combustible gases are then purified with a view to their subsequent use in the said process. <IMAGE>

Description

It will find its application in particular in the field of urban and / or industrial waste disposal as well as in the field of recovery of this waste.

In the field of treatment of urban and / or industrial waste, various techniques are known to date, ranging from the simplest which consists of depositing garbage and waste in open landfills to the most sophisticated solutions using the reactions pyrolysis or thermolysis.

Pyrolysis consists of burning a solid with a certain lack of oxygen. Oxygen is used in this reaction to heat the product and to decompose the materials in combustible gases, smoke and combustible carbonaceous residues, such as charcoal.

The thermolysis reaction is even higher than that of pyrolysis because we are in the presence of a phenomenon of distillation of organic matter. During this reaction, the heat no longer comes from a direct flame but from radiation from a heating chamber.

When a thermolysis reaction is carried out on urban and / or industrial waste, we will somehow carry out a distillation of these to finally obtain carbonaceous solids recoverable and recoverable after sorting of inert, tars recoverable and recoverable in specific petrochemical plants, as well as clean combustible gases that can also be reused. So far, laboratory tests of thermolysis and some Experiments promise an interesting future for the treatment of urban and / or industrial waste, but no process or treatment facility has yet emerged, allowing certain economic industrial development.

In order to be usable, such an urban and / or industrial waste treatment installation must be efficient, economical, profitable and environmentally friendly.

The efficiency of the installation depends on the quality of the products obtained, that is to say the recoverable residual materials.

This efficiency is also linked to the time for implementing a treatment and consequently has repercussions on the cost price of the treatment. Indeed, since it is a question of treating urban and / or industrial waste, this treatment must be affordable in order not to be dissuasive.

Finally, the treatment installation must be safe in terms of its operation, i.e. it must not be dangerous for the personnel supervising the operations or polluting the environment with regard to possible clearances. that could happen.

• on déshydrate préalablement les déchets à traiter dans une enceinte fermée de séchage, dans laquelle ils sont soumis à un flux d'air chaud,
• on dirige les déchets ainsi déshydratés dans une enceinte fermée de décomposition dans laquelle ils sont soumis à une étape de décomposition thermique produisant au moins des produits gazeux,
• on récupère, en circuit fermé par rapport à l'atmosphère, au moins les gaz produits lors du séchage et on les traite en vue de leur réutilisation.

However, document FR 2,629,179 discloses a method for treating urban waste by which:

• the waste to be treated is previously dehydrated in a closed drying enclosure, in which it is subjected to a flow of hot air,
• the waste thus dehydrated is directed into a closed decomposition enclosure in which it is subjected to a thermal decomposition stage producing at least gaseous products,
• at least the gases produced during drying are recovered, in a closed circuit with respect to the atmosphere, and they are treated with a view to their reuse.

In this installation, drying and decomposition are carried out by sending hot gases directly into the waste to be treated. At the outlet of the drying and decomposition chambers, the gases obtained are collected and treated then transformed into combustible gases intended for the supply of the burners producing the drying and decomposition gases.

Furthermore, document FR 2 366 354 or DE 2 950 324 also discloses waste decomposition systems carried out in a decomposition enclosure allowing indirect heating of the waste.

The object of the present invention is to provide a method and an installation for treating urban and / or industrial waste in which a thermolysis reaction is used which is entirely suited to industrial requirements, namely efficiency, economy, pollution.

One of the aims of the present invention is to provide a method and an installation for treating urban and / or industrial waste, which allow continuous treatment of waste and which allow a lifetime. important installation mechanics, avoiding repetitive thermal shocks as much as possible.

Another object of the present invention is to provide a method and an installation for treating urban and / or industrial waste in which the temperature is obtained by the autothermal combustion of the residues produced during the reaction.

Another object of the present invention is to provide a method and an installation for treating urban and / or industrial waste in which the different stages are controlled sequentially, the control of each of these stages being carried out from the point of view of the temperatures set works, the atmosphere in which the reaction is carried out, to allow stable operation in temperature and pressure.

Another object of the present invention is to provide a process which allows the production of installations for treating urban and / or industrial waste, which are modular in their capacity and which can be easily adapted according to such or such uses.

Another object of the present invention is to provide a method and an installation for destroying urban and / or industrial waste which are advantageous in terms of the recovery of the material which can be stored and then checked before reuse.

Another object of the present invention is to provide a method and an installation for treating urban and / or industrial waste which are particularly advantageous from an ecological point of view and which make it possible to provide a solution to the problem of pollution of incinerators, well known to date.

In fact, thanks to the present invention, only gases or previously purified products are discharged into the atmosphere, that is to say in which all traces of pollution for the environment are eliminated and creation is particularly avoided. chlorinated compounds and pollutants that are difficult to remove, such as dioxide, at high temperatures.

Other objects and advantages of the present invention will appear during the description which follows which is however given only for information and which is not intended to limit it.

• on déshydrate préalablement les déchets à traiter dans une enceinte fermée de séchage dans laquelle ils sont soumis à un flux d'air chaud,
• on dirige les déchets ainsi déshydratés dans une enceinte fermée de décomposition dans laquelle ils sont soumis à une étape de décomposition thermique produisant au moins des produits gazeux et on soumet les gaz de réaction à une étape de purification,
• on récupère, en circuit fermé par rapport à l'atmosphère, au moins les gaz produits lors du séchage et on les traite en vue de leur réutilisation,
  est caractérisé par le fait que
• ladite décomposition s'effectue par thermolyse à une température de l'ordre de 400 à 450°C, dans une chambre de thermolyse isolée et contrôlée, dans laquelle on établit la température indirectement par rapport aux déchets à traiter, par circulation de gaz de chauffage haute température,
• on récupère cesdits gaz de chauffage en circuit fermé par rapport à l'atmosphère et on soumet ces gaz à une étape de purification, constituée par un brûleur et un système de soufflage,
• on soumet les gaz produits lors du séchage à une étape de purification, constituée par un brûleur et un système de soufflage,
• on réinjecte au moins en partie lesdits gaz purifiés dans l'installation comme agents de séchage et on évacue les gaz excédentaires non polluants vers l'extérieur.

According to the present invention, the process for treating urban and / or industrial waste, by which:

• the waste to be treated is previously dehydrated in a closed drying enclosure in which it is subjected to a flow of hot air,
• the waste thus dehydrated is directed into a closed decomposition enclosure in which it is subjected to a thermal decomposition step producing at least gaseous products and the reaction gases are subjected to a purification step,
• at least the gases produced during drying are recovered, in a closed circuit relative to the atmosphere, and they are treated with a view to their reuse,
  is characterized by the fact that
• said decomposition is carried out by thermolysis at a temperature of the order of 400 to 450 ° C., in an isolated and controlled thermolysis chamber, in which the temperature is established indirectly with respect to the waste to be treated, by circulation of heating gas high temperature,
• these heating gases are recovered in a closed circuit with respect to the atmosphere and these gases are subjected to a purification step, constituted by a burner and a blowing system,
• the gases produced during drying are subjected to a purification step, consisting of a burner and a blowing system,
• said purified gases are at least partially reinjected into the installation as drying agents and the non-polluting excess gases are discharged to the outside.

In addition, according to the present invention, the thermolysis reaction is carried out at low temperature, of the order of 400 to 450 ° C., in a thermolysis chamber, isolated and controlled, then the gaseous products obtained from the thermolysis reaction, in closed circuits with respect to the atmosphere, in which the combustible gaseous elements are separated from the tars in the gaseous state, then the combustible gases are purified with a view to their subsequent re-use in said process.

• une chambre de séchage des déchets à traiter, constituée par une première enceinte fermée,
• des moyens pour créer une veine d'air chaud apte à circuler dans ladite enceinte de séchage,
• des moyens pour récupérer et traiter le fluide gazeux issu du séchage de l'enceinte de séchage,
• une deuxième enceinte fermée de décomposition des déchets déshydratés,
• un circuit pour purifier les gaz de décomposition,
  est caractérisée par le fait
• que la deuxième enceinte fermée se présente sous la forme d'une chambre de thermolyse, contrôlée et isolée, constituée par un réacteur double enveloppe présentant une enceinte primaire, dans laquelle sont introduits les déchets et une enceinte secondaire de chauffage, apte à élever au moins la température de l'enceinte primaire pour mener la réaction de thermolyse, par circulation de gaz de chauffage haute température,
• et qu'elle comporte :
  • des moyens pour récupérer lesdits gaz de chauffage,
  • des moyens pour réinjecter, au moins en partie, lesdits gaz, au niveau desdits moyens pour créer la veine d'air chaud de séchage,
  • un moyen pour purifier ledit fluide gazeux issu du séchage, et lesdits gaz de chauffage récupérés, ledit moyen étant constitué par le brûleur et le système de soufflage.

The installation allowing the implementation of the method of the invention comprises at least:

• a drying chamber for the waste to be treated, constituted by a first closed enclosure,
• means for creating a stream of hot air able to circulate in said drying enclosure,
• means for recovering and treating the gaseous fluid resulting from the drying of the drying chamber,
• a second closed enclosure for decomposing dehydrated waste,
• a circuit for purifying the decomposition gases,
  is characterized by the fact
• that the second closed enclosure is in the form of a thermolysis chamber, controlled and isolated, constituted by a double-envelope reactor having a primary enclosure, into which the waste is introduced and a secondary heating enclosure, capable of raising at least the temperature of the primary enclosure for carrying out the thermolysis reaction, by circulation of high temperature heating gas,
• and that it includes:
  • means for recovering said heating gases,
  • means for reinjecting, at least in part, said gases, at the level of said means for creating the stream of hot drying air,
  • means for purifying said gaseous fluid from drying, and said recovered heating gases, said means being constituted by the burner and the blowing system.

In addition, the installation includes means for recovering solid materials and for recovering and treating gaseous products resulting from thermolysis.

The present invention will be better understood on reading the following description, accompanied by the accompanying drawings which form an integral part thereof.

Figure 1 shows schematically the various elements constituting the treatment installation of the present invention.

FIG. 2 shows in detail the means of recovery and treatment of the gaseous products resulting from the thermolysis carried out in the installation of FIG. 1.

The invention relates to a method and an installation for treating urban and / or industrial waste, which in particular allow destruction of such waste in a non-polluting and economical manner using a thermolysis reaction.

Regarding pollution, it should be noted that the system developed allows treatment in closed circuits avoiding any communication with the outside.

With regard to the profitability of the installation, it should be noted that the products obtained by the implementation of thermolysis consist of carbonaceous solids recoverable and recoverable after sorting inert, tars also recoverable and recoverable in specific thermal or petrochemical installations as well as clean gases reusable in the process of the invention after inspection.

This recovery significantly reduces the costs of waste treatment, and the recovery of certain gases allows significant energy savings.

Thus, by the process of the present invention, the waste is subjected to a fully controlled thermolysis reaction, in which in particular the creation at high temperature of chlorinated compounds and stable pollutants difficult to remove, such as dioxide, is avoided, and then the products obtained by implementing different stages carried out successively and sequentially, without discharge polluting the atmosphere.

Prior to the thermolysis reaction, according to the present invention, the waste to be treated is dehydrated in order to eliminate a large part of the moisture contained in it.

This prior dehydration is carried out in a closed drying enclosure and this phase is completely controlled since all the gases produced during drying are recovered, in a closed circuit with respect to the atmosphere, and these gases are subjected to a purification step.

This is a very important point in terms of pollution and in terms of the economy.

In terms of economy, according to the treatment method of the invention, said purified gases are at least partially reinjected into the installation as a drying agent. However, it is necessary to evacuate the excess gases, because for example it is necessary to enter the installation of the combustion air. However, this discharge to the outside is carried out in a non-polluting way because the excess gases are not aggressive for the atmosphere.

In addition, according to the process of the present invention, the thermolysis is advantageously carried out at a temperature below 450 ° C. to avoid the formation of dangerous pollutants such as, for example, dioxide.

This thermolysis reaction is carried out in a thermolysis chamber, isolated and controlled, from which the gaseous products resulting from the thermolysis reaction are recovered, in closed circuits with respect to the atmosphere.

The recovered gaseous products, resulting from the thermolysis reaction, are then also treated in closed circuits in which the combustible gaseous elements are separated from the tars in the gaseous state, then the combustible gases are purified with a view to their subsequent use in said process, i.e. separating the droplets from the gas before storage.

It should be noted that the thermolysis reaction can be carried out at atmospheric pressure.

However, very good results have been noted in carrying out the thermolysis reaction under sweeping neutral gas for the reaction, in the thermolysis chamber, at a controlled pressure slightly higher than atmospheric pressure.

Good results have also been obtained by conducting the thermolysis reaction in an overpressure thermolysis chamber.

The gaseous products resulting from thermolysis are continuously removed from the thermolysis chamber and directed to the means for recovering and treating said gaseous products.

In the case where the reaction is carried out under neutral gas sweeping, such a gas is blown into the thermolysis chamber at a pressure slightly higher than atmospheric pressure, for example of the order of 1.6 bar, which continuously flushes out gaseous products from thermolysis.

In the case where the thermolysis reaction is carried out under overpressure, it is the pressure prevailing inside the thermolysis chamber which will drive the gases resulting from the thermolysis out of the enclosure as a function of a calibration pressure. predetermined.

• la thermolyse entre 400 et 450°C sous balayage de gaz carbonique CO2 à une pression intérieure de 1,6 bar,
• la thermolyse entre 400 et 450°C sous une pression absolue jusque 3 bars.

For your information, it should be noted that we carried out various experiments giving significant results by performing:

• thermolysis between 400 and 450 ° C while sweeping carbon dioxide CO2 at an internal pressure of 1.6 bar,
• thermolysis between 400 and 450 ° C under absolute pressure up to 3 bars.

As regards the thermolysis step proper, the temperature in the thermolysis chamber is established, indirectly with respect to the waste to be treated, by circulation of high temperature heating gas.

According to a characteristic of the present invention, these heating gases are recovered, in a closed circuit with respect to the atmosphere, and these gases are subjected to a purification step, in the same way as the gases produced during the preliminary drying.

Also, the purified gases are at least partially reinjected into the installation as a drying agent.

The purified excess gases, therefore non-polluting, can be evacuated outside the installation.

One of the advantages of the process of the present invention is to allow continuous treatment of the waste.

For this, the waste is dehydrated in a drying chamber, in which it is stirred and subjected to a flow of hot air, such that a movement of the waste from the inlet to the outlet of said said is defined. drying chamber.

The waste thus dehydrated is then introduced, gravitatively and sequentially, into said thermolysis chamber, isolated and controlled, in which the thermolysis reaction proper is carried out, as has been specified above.

When the waste to be treated has undergone the thermolysis phase, it is then removed by gravity and sequentially solids from thermolysis for recovery.

In this regard, it should be recalled that the gaseous products resulting from thermolysis are withdrawn continuously as has been specified above.

FIG. 1 shows an example of an installation for treating urban and / or industrial waste, capable of carrying out a thermolysis reaction and designed particularly for the implementation of the method of the invention which has just been described.

It comprises at least one drying chamber (1), controlled and isolated, waste to be treated, a thermolysis chamber (2) controlled and isolated, as well as means (3, 4) for recovering solid materials and gaseous products. from thermolysis.

In addition, to allow continuous processing of the waste and to allow the implementation of the different stages of the process sequentially, the drying chamber (1), the thermolysis chamber (2) and the means (3) for recovering the materials. solids are advantageously arranged successively in series in such a way as to allow a continuous, sequential gravity movement of the waste and the contained materials, from the inlet of the installation (5) to its outlet (6) and that the 'We can keep each chamber (1, 2, 3) stable operation in temperature and / or pressure.

Thanks to this succession of chambers, a continuous supply of the installation is allowed and by separating the different functions of the chambers, thermal shocks and sealing problems are avoided by stable operation of each of the chambers.

The first phase of the actual treatment therefore consists of a phase of drying or dehydration of the waste.

This phase is carried out in the drying chamber (1) in which the waste is stirred and subjected to a flow of hot air. In addition, an advance movement (7) of the waste is generated from the inlet (5) to the outlet (8) of said drying chamber (1).

In one embodiment of the present invention, the drying chamber (1) consists of an enclosure (9) closed, having an inlet (5) through which the waste to be treated is introduced and an outlet (8) from which the dehydrated product will drain out.

Inside the closed enclosure (9) is provided a motorized drum (10) able to contain the waste to be dried and to brew it permanently, and also able to create said advance movement (7) for the waste from the inlet (5) to the outlet (8).

To obtain the dehydration of the waste, it is subjected to a flow of hot air, shown diagrammatically in (11) in the figure. Also, according to the invention, the installation comprises means (12, 13) for creating a stream of hot air able to circulate in said drying enclosure (9).

As the figure particularly shows, the preparation of this hot air is carried out in a treatment box (12) which comprises a gas burner (13) and a blowing system (47) placed upstream of the burner (13), and able to direct a gas flow towards the flame of said burner.

The drying circuit also includes means (48) for recovering the gaseous fluid resulting from the drying of the drying chamber (9) as well as means for purifying said gaseous fluid resulting from drying.

Thus, the hot dry air (11) introduced into the dryer absorbs, on contact with the stirred waste, the moisture contained in it and thus leaves charged with moisture in (16).

This moist air (16) recovered by the means (48) then passes through a condenser exchanger (17) in order to be dehumidified and before being recycled to the means (12, 13) to create said stream of hot air, at the inlet (15) of the air treatment box (12) so that it is purified.

In particular, according to the present invention, said means for creating the stream of hot air and for purifying the gaseous fluid consist essentially of the burner (13) and the blowing system (47).

A burner will be provided, the flame of which advantageously reaches at least 850 ° C. and a blowing system, the speeds of which will be such that the said gases will pass through the flame and will be maintained at this temperature for at least two seconds. Thus, a sterilization of the gases will be obtained which will therefore be purified and the aromatic essences which they contained will be burned.

It should be noted that to allow the combustion of the gas burner (13), an air supply (14) from the outside is provided. Also, since the dryer outlet gases are recycled to the box (12), via a gas supply (15) upstream of the burner, it will be necessary to evacuate part of the purified recycled gases outwards. These excess gases are non-polluting for the atmosphere.

In this regard, it should be noted that there will advantageously be a set of recovery batteries (18) installed on the discharge of high temperature excess gases (19) and the supply of outside air (20) in order to allow to heat this air before suction by the burner (13). This will also allow significant energy recovery.

A valve (50), installed on the discharge of high temperature excess gases (19), before the recovery battery (18), will allow the adjustment of the volume of air entering compared to the volume of air leaving.

In addition, to promote drying, according to the present invention, the direction of circulation of the hot air flow (11) is opposite to said advance movement (7) of the waste in the dryer. For this, the drum (10) is placed in said stream of hot air and provision is made for its rotation and its arrangement so that the hot air is introduced countercurrently into the dryer.

More specifically, said drum (10) is arranged horizontally with its inclined axis of rotation to allow movement (7) of the waste from the inlet (5) to the outlet (8) of the dryer. In addition, to promote this movement, the drum (10) will internally have blades (49) fixed on the latter.

However, following this drying phase, according to the present invention, the actual thermolysis reaction is carried out in the thermolysis chamber (2).

According to the illustrated embodiment, this thermolysis chamber (2) is constituted by a double jacket reactor having an internal primary enclosure (21), fixed, into which the waste is introduced, and by a secondary external heating enclosure (22), fixed, enveloping said primary enclosure (21).

Inside the reactor (2) is provided a motorized rotor (23) equipped with paddles (24) oriented and fixed on a central axis controlled by a motor (25).

The arrangement of the pallets as well as the rotation of these generate a displacement of waste or solid matter, shown diagrammatically by the arrow (26) from the inlet (8) of the thermolysis chamber (2) towards its outlet (27) .

In the proposed embodiment, the thermolysis chamber is horizontal; nevertheless, other arrangements could be envisaged, the rotor possibly being oblique, or even vertical. Likewise, a fixed enclosure and a rotating rotor are provided, but of course, one could imagine a reverse system in which the enclosure would turn.

The waste is heated up in particular by the combustion gases from a burner (28), of the mixed fuel oil - gas type for example, circulating in said secondary enclosure (22) which surrounds the primary enclosure (21).

This circulation of high temperature gas allows in particular the rise in temperature inside the enclosure (21) of the reactor of the order of 400 to 450 ° C.

At the outlet (29) of the secondary enclosure (22), the gases shown diagrammatically at (30) in the figure are reinjected into the drying circuit, as described above, thus participating in energy recovery. These gases are in particular reinjected at the inlet (15) of the box (12).

Also, such an arrangement allows recovery heating gases which heat the thermolysis chamber, recovery which takes place in a closed circuit with respect to the atmosphere. Then these gases are also subjected to a purification step as it was for the drying gases.

Part of these purified gases is reinjected into the installation, as a drying agent, and the non-polluting excess gases are discharged to the outside.

In addition, according to the invention, the drying (1) and thermolysis (2) chambers are superimposed, as shown in particular in FIG. 1, so that loading can occur by gravity. However, one could consider placing the chambers (1) and (2) side by side and carry out the loading by means of elevating conveyors.

Between the outlet of the drying chamber (1) and the inlet of the thermolysis chamber (2), there is an airlock (31) capable of connecting the two chambers in a sealed manner, so the waste can be introduced into the chamber thermolysis (2) continuously via said airlock (31) in order on the one hand to balance the pressures between the two enclosures and on the other hand, to authorize a neutralization of the incoming product, in particular by injection of nitrogen or pressure balance before opening the interior door of the airlock, or other.

Similarly, at the outlet (27) of the thermolysis chamber, there is another airlock (32) also sealingly connecting the thermolysis chamber and the means for recovering solid materials (3).

The purpose of this second airlock (32) is similar to the first with regard to the evacuation of solids from thermolysis.

However, during the thermolysis phase, the waste is stirred inside the enclosure (21) of the reactor by the rotor (23-25). In addition, the blades (24) define an advance movement (26) of the material contained in the chamber (2), from its inlet (8) to its outlet (27).

Throughout the thermolysis, according to the process of the present invention, the gaseous products resulting from the thermolysis reaction are recovered and treated in closed circuits (33) relative to the atmosphere as particularly illustrated in FIG. 2 .

The closed circuit (33) substantially constitutes said means (4) for recovering gaseous products resulting from thermolysis and are capable of separating the fuel elements from the tars in the gaseous state, by washing the combustible gases, with a view to their subsequent use. in said method.

More precisely, these means (4) consist of a closed circuit (33) comprising at least one device for circulating said gaseous products such as a mechanical extraction device (34), a separator (35) "gaseous element fuel - tar in gaseous state ", of sprayer type, a gas purification circuit (36) in which the gas droplets are separated before its storage, as well as a circuit (37) for treating liquid effluents .

At the outlet of the thermolysis reactor (2), taking into account the temperature at which the reaction is carried out, there is a mixture of the combustible gaseous elements and of the tars in the gaseous state. These gases are removed under pressure or by sweeping the gas. In addition, certain powdery solid elements can also be entrained.

As shown in FIG. 2, the principle of separation of combustible gases and tars leaving the reactor is carried out by the wet method using the separator (35) of the sprayer type generally known under the name of "quench at the water".

In this separator, under the effect of spraying at low temperature and against the current, the gaseous part is separated and the tars are condensed in the lower part (38) of the separator.

On the other hand, the gaseous elements produced by the thermolysis reaction escape through the top (39) of the separator, the extraction device (34) making it possible to overcome the pressure drops in the circuit. These gases are combustible and are then purified and stored in pressure tanks before being reused by the installation's burners.

As regards the treatment of liquid effluents, condensed at the lower part (38) of the separator (35), it comes in two components, namely an aqueous phase and tars themselves.

To separate these two elements, one operates by decantation given their very different density, for example 0.99 and 0.77 respectively.

This decantation is carried out in the treatment circuit (37) in which the light phase is continuously recovered by an oleophilic drum, then detached from the drum using a scraper which sends it in a small buffer capacity (40) , heated by an internal coil, in order to lower the viscosity of the organic mixture.

This mixture is then taken up by a gear then stored in a tar storage tank (41) before being redirected or treated.

The heavy aqueous phase is taken up at the bottom of the settling tank (37) by a centrifugal pump (42) then clarified on filters (43) intended to remove solid particles such as dust. The decantation purge is then purified of any organic compound by passage over active carbon (44) and then discharged into the wastewater basin.

In addition, during the treatment of the liquid effluents, the washing liquid, used in the separator (35) of the sprayer type, is recycled, kept at low temperature on the loop. The on-line neutralization of the chlorine contained in the gas circuit is done by injection of soda (45) in the water of the "Quench". The circuit is purged regularly to be sent to the settling tanks (37).

If the gaseous products resulting from thermolysis are taken continuously from the reactor core, according to the present invention, the solids resulting from thermolysis are removed by gravity and sequentially. This evacuation is, let us recall, carried out by means of the airlock (32) which makes it possible to maintain a controlled atmosphere inside the reactor (2).

As shown in particular in Figure 1, in the case of the installation described, the thermolysis chamber (2) and the recovery means (3) are superimposed, the latter being in particular constituted by a container (46) adapted under said airlock (32). However, it could also be possible to place them side by side with a lifting conveyor between them.

In this container (46) a phase of cooling of solid residues from thermolysis, such as coals or inert materials, these being recovered from below the reactor (2) via the airlock (32), in particular neutralized by nitrogen injection.

Advantageously, a mobile, sealed, double-envelope container (46) is used, in which cold water is circulated in order to accelerate the cooling of the product.

As soon as the temperature inside the container (46) reaches about 50 ° C, it can then be opened without risk of explosion to recover the products it contains.

Advantageously, there will be a handling device with a magnetic drum to remove ferrous materials and a vibrating screen to isolate the inert parts of the carbon. All of this equipment will be provided in particular under a sealed hood in order to limit carbon dust and its expansion in the atmosphere.

Furthermore, as regards the supply of the installation of the present invention, at the level of the waste inlet (5), this will be carried out by traditional means and known in the field of treatment of urban and / or industrial waste.

For example, urban waste is supplied in a main pit with an autonomy of several days of operation, but without however being exaggerated so as to minimize the release of odors.

In addition, the air volume located above the repository is maintained in depression by a mechanical ventilation assembly.

There will also be an overhead crane equipped with a grapple to transfer waste from the main pit to a hopper from which a set of conveyor belts will distribute the waste to a grinding set.

On this transport chain, for example, provision is made, on the one hand, for sorting for removing bulky objects and, on the other hand, for tearing apart plastic bags, in particular by metal comb, located in a tunnel ensuring a first burst of the whole gross product.

The waste thus prepared is then conveyed on a crusher allowing the ultimate physical transformation of the raw product before treatment. Grinding will shred household waste into sufficiently small elements to facilitate the drying technique described above.

Finally, a belt conveyor assembly takes up the waste thus treated from the mill outlet to store it in a hopper with a capacity such that it can continuously supply the drying chamber (1) of the present invention.

The means for treating the gaseous products resulting from thermolysis which have just been described will in particular be adapted as a function of the conditions under which the thermolysis reaction is carried out, namely under atmospheric pressure or under CO 2 sweeping or under overpressure particularly to allow in the different processing circuits the circulation of the different products.

Claims (16)

1. Method for processing urban and/or industrial waste, by which:

   - the waste to be processed is previously dehydrated in a closed drying vessel (1, 9) in which it is subjected to a hot air flow,

   - the so dehydrated waste is directed into a closed decomposition vessel (2, 21, 22) in which it is subjected to a thermal decomposition step producing at least gaseous products (4) and the reaction gases are submitted to a purification step.

   - into a closed circuit with respect to the atmosphere are recovered at least the gases (16) produced during drying and they are processed with a view to being re-used,
   characterized in that

   - said decomposition occurs by thermolysis at a temperature in the range of 400 to 450°C in an insulated and controlled thermolysis chamber (21, 22) in which the temperature is indirectly set with respect to the waste to be processed by high-temperature heating-gas circulation,

   - these said heating gases (30) are recovered into a closed circuit with respect to the atmosphere and these gases (30) are submitted to a purification step (12) comprised of a burner (13) and a blowing system (47),

   - the gases (16) produced during drying are subjected to a purification step (17, 12) comprised of a burner (13) and a blowing system (47),

   - at least part of said purified gases (11) is re-injected into the plant as drying agents and the non-polluting excess gases are discharged to the atmosphere.
2. Processing method according to claim 1, characterized in that the gaseous products resulting from the thermolysis reaction are processed in closed circuits (4, 33) with respect to the atmosphere in which the combustible gaseous elements are separated from the tars in gaseous state, then the combustible gases are purified with a view to their later being used in said method.
3. Processing method according to claim 1, characterized in that the waste to be processed is stirred up during the drying step, so as to detine a waste feed motion (7) from the inlet (5) to the outlet (8) of said drying vessel (1).
4. Processing method according to claim 1, characterized in

   - the so dehydrated waste is sequentially introduced by gravity into the thermolysis chamber (2),

   - the solid material resulting from the thermolysis is sequentially discharged by gravity and the gaseous products resulting from the thermolysis are continuously removed.
5. Processing method according to claim 4, characterized in that the waste is stirred up during the thermolysis reaction, so as to define a feed motion (26) for the material contained in the thermolysis chamber (2) from the inlet (8) to the outlet (27) of said chamber.
6. Processing method according to claim 1, characterized in that the thermolysis reaction is conducted under sweeping of neutral gas for the reaction at a controlled pressure slightly higher than the atmospheric pressure.
7. Processing method according to claim 1, characterized in that the thermolysis reaction is conducted under overpressure.
8. Plant for processing urban and/or industrial waste, capable of implementing a thermolysis reaction, designed for implementing the method according to claim 1, comprising at least:

   - a drying chamber (1) for the waste to be processed, comprised of a first closed vessel (9),

   - means (12, 13, 47) for creating a jet of hot air capable of circulating in said drying vessel (9),

   - means (48) for recovering and processing the gaseous fluid (16) resulting from the drying in the drying vessel (9),

   - a second closed decomposition vessel (2) for the dehydrated waste,

   - a circuit for purifying the decomposition gases,
   characterized in that:

   - the second closed vessel is in the form of a controlled and insulated thermolysis chamber (2) formed by a double-walled reactor having a primary vessel (21) into which is introduced the waste and a secondary heating vessel (22) capable of raising at least the temperature of the primary vessel (21), to conduct the thermolysis reaction, by high-temperature heating-gas circulation, and

   - it includes:

   - means for recovering said heating gases (30),

   - means for re-injecting, at least partly, said gases (16, 30) at the level of said means (12, 13, 47) to create the jet of drying hot air,

   - a means (12) for purifying said gaseous fluid (16) resulting from the drying and said recovered heating gases (30), said means being comprised of the burner (13) and the blowing system (47).
9. Processing plant according to claim 8, characterized in that the drying room (1) includes, inside the vessel (9), a motor-driven drum (10) capable of containing the waste to be dried and stirring same up permanently and of creating a feed motion (7) for the waste from the inlet (5) to the outlet (8), said drum (10) being arranged in said jet of hot air.
10. Processing plant according to claim 9, characterized in that said drum (10) includes, inside, blades (49) fixed onto this latter and is horizontally arranged, its axis being inclined in order to authorize a moving (7) of the waste from the inlet (5) to the outlet (8).
11. Processing plant according to claim 8, characterized in that it includes means (3, 4) for recovering the solid materials and recovering and processing the gaseous products resulting from the thermolysis.
12. Processing plant according to claim 11, characterized in that the drying chamber (1), thermolysis chamber (2) and the recovering means (3) are superposed and successively arranged in series so that a sequential continuous moving under gravity of the waste is authorized from the inlet (5) of the plant to its outlet (6) and that a temperature- and/or pressure-stable operation can be maintained at each chamber (1, 2, 3).
13. Processing plant according to claim 11, characterized in that the thermolysis chamber includes a motor-driven rotor (23) equipped with oriented blades (24) provided for inside said primary vessel (21) in order to authorize a moving of the waste and/or the solid material from the inlet (8) to the outlet (27) of the reactor.
14. Processing plant according to claim 11, characterized in that it furthermore includes at least two lock chambers (31, 32), one (31) connecting the drying chamber (1) and the thermolysis chamber (2), the other one (32) connecting the thermolysis chamber (2) and the solid-material recovering means (3), in order, on the one hand, to balance the pressures and, on the other hand, to authorize a neutralization of the incoming and outgoing product.
15. Processing plant according to claim 11, characterized in that the means (4) for recovering the gaseous products resulting from the thermolysis are comprised of a closed circuit (33) including circulation means (34) for said gaseous products, a sprayer-type "combustible gaseous elements - gaseous-state tars" separator (35), a gas purification circuit, a liquid-effluent processing circuit (37).
16. Processing plant according to claim 8, characterized in that said means (12, 13, 47) for creating a jet of hot air in said drying vessel and said means (12, 13) for purifying the gaseous fluid resulting from the drying are substantially comprised of a burner (13) the flame of which reaches at least 850°C and a blowing item (47), located upstream with respect to the burner, capable of directing a gas flow towards the flame the speed of which is such that said gases will pass through the flame for at least two seconds.

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