Abstract:
A method and apparatus is provided for the thermolysis of solid waste within an enclosed thermolysis chamber in the absence of free oxygen which produces a thermolysis off-gas. The thermolysis off-gas is removed from the thermolysis chamber and injected into a cyclone where it is washed with water and cooled. The washed and cooled thermolysis off-gas is divided into two portions. One portion of the washed thermolysis off-gas is further cooled in a heat exchanger and then injected into a burner and combusted, while the remaining portion of the washed thermolysis off-gas is passed into indirect heat exchange with the hot off-gas resulting from the combustion of the other portion of the thermolysis off-gas in the burner and recycled back into the enclosed thermolysis chamber. This in-situ recycling of hot thermolysis off-gas helps prevent the creation of hot spots in the thermolysis chamber and the possibility of an explosive reaction between oxygen and hydrogen. The catalytic radiant panels and burners can be replaced with the injection of hot thermolysis gas back into the thermolysis area.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention concerns a method and plant for treating by thermolysis solid waste products whose disposal is harmful to the environment. 
     2. Description of the Prior Art 
     Document EP-A-0 610 120 discloses a plant facility for treating solid waste products whose disposal is harmful to the environment including a dehydration area into which the solid products are fed, a thermolysis area downstream of the dehydration area, an outlet area in which the solid residues are cooled and a pumping station communicating via an extraction line with the thermolysis area to maintain it at a reduced pressure and to aspirate thermolysis gases from it. 
     The pump station communicate via a combustible gas feed line with a boiler for burning the thermolysis gases which are maintained at a temperature greater than the temperature of condensation of tars that can form in the gaseous state during thermolysis, before they are used as fuel in the boiler. The thermolysis gases are exploited directly to generate thermal energy that is transformed in the plant or fed to a turbine that converts it to electrical energy or used for any other function, possibly external to the plant facility. 
     The boiler can also use the fuel (coal) contained in the solid residues. 
     The flue gases from the boiler are used to heat the dehydration area. 
     To enable thermolytic transformation in the total absence of free oxygen the dehydration, thermolysis and cooling areas consist of chambers isolated from each other in a substantially airtight manner. 
     The dehydration and thermolysis chambers are provided with heating elements such as catalytic radiator panels or flame burners using the thermolysis gases and/or (low price) commercially available combustible gases. 
     In the case of burners the enclosures of the aforementioned chambers are heated by radiation from the inside wall of the chambers heated by the burner flames. In this case heating is also assured by convection of the gases in the charge of products to be treated which is assured by expansion of the gases generated in the corresponding chamber. 
     The catalytic radiant panels are fed with pure oxygen or with air and with thermolysis gases resulting from thermolytic decomposition. In this case the carbon dioxide and the steam generated by oxidation of the thermolysis gases in the catalytic radiant panels can contribute to heating by convection and radiation. 
     As mentioned above, the flue gases from the boiler can also be used to heat the aforementioned chambers. 
     Thus the temperature of the thermolysis chamber is maintained at around 600° C., for example, and that of the dehydration chamber is maintained at a lower temperature above 100° C., for example around 120° C. 
     The solution described in document EP-A-0 610 120 is satisfactory overall. However, the use of burners in the dehydration and thermolysis chamber generates hot spots exposing the chambers to non-negligible mechanical stresses. These mechanical stresses can give rise to sealing problems which can be particularly troublesome because the penetration of oxygen into the thermolysis chamber can cause an explosion in the presence of hydrogen in the thermolysis chamber. 
     This risk of explosion is also present when catalytic radiator panels are used because they employ oxygen as a combustion-supporting gas. 
     Moreover, heating the chambers consumes external energy when commercially available combustible gases are used. 
     Document U.S. Pat. No. 3,525,673 describes another method of treating organic waste and the corresponding plant facility. In this method the waste is reduced to basic carbon-containing products by superheated steam at a low positive pressure in a closed circuit. The steam recovered after passing through the waste is condensed and the uncondensed gases are separated from the water and the substances dissolved therein. 
     BRIEF SUMMARY OF THE INVENTION 
     This method is limited to the treatment of organic waste and consumes large quantities of water. 
     The present invention aims to alleviate these drawbacks. 
     An underlying objective of the present invention is a method of treating solid waste products, whose disposal is harmful to the environment, that is self-sufficient from the energy point of view. 
     To this end the present invention proposes a method of treating solid waste products, whose disposal is harmful to the environment, including a step of thermolysis of the solid products in a thermolysis area, wherein: 
     the gases are aspirated from the thermolysis area; 
     at least a portion of the aspirated gases is cooled to a temperature less than approximately 80° C.; 
     the condensed products from cooling the uncondensed gases are separated from this cooling; 
     a portion of the aspirated gases is heated by combustion of at least a part of the uncondensed gases; and 
     the heated portion of the gases is recycled by feeding it back into the thermolysis area. 
     The invention also teaches replacing the catalytic radiant panels or burners with direct injection of a flow of hot gases including recycled thermolysis gases into the thermolysis area. 
     This prevents the creation of hot spots and any possibility of an explosive reaction between oxygen and hydrogen. 
     In situ recycling of the thermolysis gases also renders the treatment method of the present invention self-sufficient. 
     Thermolysis effected in this way, by forced circulation of a flow of hot gas resulting from feeding the flow into the thermolysis area, direct contact with the charge and then aspiration of the gases from the thermolysis area, is found to be particularly regular but most importantly significantly faster than thermolysis carried out in accordance with the teaching of document EP-A-0 610 120. 
     Moreover, a maximum of solid products treated by the method of the present invention is converted into energy. In particular, the tars obtained on cooling can be mixed with the fuel (coal) from the solid residues from the thermolysis area, for example, to constitute a fuel for subsequent exploitation. 
     Cooling at least some of the gases from the thermolysis area facilitates exploitation of the thermolysis products. Converting some of the gases from the thermolysis area into condensed products minimizes the volume of the means for storing the products (tars, etc). Furthermore, the uncondensed gases are advantageously reused to heat the flow of gas to be fed into the thermolysis area. 
     Finally, this cooling protects the treatment plant facility and in particular the pump utilized in the process. 
     To improve further the efficiency of thermal transfer of this thermolysis process, in a relatively simple manner, the heated portion of the gas is advantageously injected in the immediate proximity of a static charge of solid products to be treated. 
     In one preferred embodiment the portion of the gas to be heated is a second part of the uncondensed gases obtained by cooling. 
     Thus a fraction of the uncondensed thermolysis gases is burned to heat a second part of the uncondensed gases which are recycled and returned to the thermolysis area to be enriched with thermolysis gases and in particular with hydrogen and hydrocarbons (methane, ethane, ethylene, etc). 
     In another embodiment, a first fraction of the aspirated gases is heated to approximately 60° C. to approximately 80° C. and a second fraction of the aspirated gases is heated to approximately 230° C. to approximately 330° C., at least some of the uncondensed gases from the first fraction are burned, the uncondensed gases from the second fraction are heated by means of the gases resulting from this combustion, the heated second fraction of the gases constituting the heated gas portion, and the condensed products obtained by cooling the first and second fractions are recovered. 
     In this embodiment, the gas fraction to be heated and recirculated into the thermolysis area in the form of a flow of hot gas is maintained at a higher temperature than the fraction to be burned. The fraction to be heated therefore requires less heating before it is fed back into the thermolysis area. 
     In this case the solid products are dehydrated prior to thermolysis, in the thermolysis area and using some of the gases resulting from combustion. 
     In this case the combustion is carried out in a boiler equipped with fiber type burners. 
     Burners of this kind are able to burn relatively impoverished gases, and in particular the thermolysis gases from an area for thermolysis of waste products constituting the solid products to be treated. Moreover, this combustion method maintains a low concentration of NO X  in the flue gases. 
     To start the treatment process liquefied gas such as propane can be burned in the boiler. If required to assure correct combustion, a certain proportion of liquefied gas can also be added to the thermolysis gases to be burned. 
     To avoid dependence on the composition of the thermolysis gases, or even on their production, they are compressed and stored in a storage tank prior to combustion. 
     In a preferred embodiment, the aspirated gases pass through a heat exchanger, as the hot fluid, after which the gases pass through a fractionating system to obtain separated fractions respectively containing heavy hydrocarbons, light hydrocarbons, water and uncondensed gases at low temperature; a part of the uncondensed gases at low temperature is re-injected into the heat exchanger, as the cold fluid, to raise its temperature before it is heated by combustion of another part of the uncondensed gases at low temperature. 
     In this preferred embodiment the boiler is equipped with multi-fuel (gas and liquid) burners so that it can burn not only the uncondensed gases but also the light hydrocarbons, the organic substances dissolved in the water and separated therefrom, fuel oil or propane. 
     Furthermore, dehydration and thermolysis are carried out simultaneously. 
     To start the process an inert gas (nitrogen, etc) or uncondensed gases previously stored are heated by combustion by one of the fuels just mentioned, some of which would then result from earlier treatment. 
     For implementation of the method of the present invention there is also proposed a plant facility for treatment of solid waste products whose disposal is harmful to the environment, including an area for thermolysis of solid products by direct contact with hot gases, a line for feeding a flow of hot gases into the thermolysis area, a line for extracting gases from the thermolysis area, and means for cooling at least a part of the gases extracted from the thermolysis area to a temperature less than approximately 80° C. and separating the condensed products from cooling from the uncondensed gases from the same cooling, disposed on the extraction line, characterized in that it includes pump facility communicating via the extraction line with the thermolysis area for aspirating the gases therefrom, a boiler adapted to burn at least a part of the uncondensed gases and communicating via an incoming line with the cooling and separator means, and a line for recycling a part of the gases extracted from the thermolysis area, the recycling line being fluidically connected to the extraction line and to the feed line and passing through the boiler to heat the gases flowing in the recycling line. 
     The plant facility can further include a line for feeding liquefied gas, such as propane, into the boiler, enabling a mixture to be maintained at an acceptable net calorific value in terms of combustion performance and starting up the installation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other aims, features and advantages of the present invention emerge from the following detailed description given by way of non-limiting example and with reference to the appended drawings, in which: 
     FIG. 1 is a theoretical schematic of the plant facility constituting one embodiment of the present invention; 
     FIG. 2 is a schematic of another embodiment of this plant facility, and 
     FIG. 3 is a schematic of a preferred embodiment of this plant. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The plant facility shown schematically in FIG. 1 includes an airlock  1  into which the solid products are fed followed by a thermolysis area  2  in which the solid products are first partly or totally dehydrated and then heated to their thermal decomposition temperature (known and fixed in advance), for example around 600° C. 
     The thermolysis area is preferably followed by a cooling area  3  in which the solid residues of thermal treatment are cooled to room temperature, for example by water sprinklers. 
     The thermolytic conversion is advantageously carried out in the total absence of free oxygen. 
     As is also taught in the aforementioned document, the areas  1 ,  2  and  3  are preferably chambers isolated from each other in a substantially airtight manner, for example by guillotine doors (not shown) actuated by cylinders, the door between chambers  1  and  2  and the door between chambers  2  and  3  being mobile transversely in airtight housings (registers). Airtight doors are also provided at the entry to chamber  1  and at the exit from chamber  3 , so that the airlock and the cooling area  3  are intentionally isolated from the exterior and/or from the thermolysis area  2 ; they can be mobile vertically or horizontally or hinged, depending on the dimensions of the plant, the space available and the preference of the designer. 
     It will be realized that the seal provided by the entry and exit doors is between the outside and areas  1  and  3  at moderate temperatures, very much lower than that in the chamber  2 . 
     To prevent air entering the chamber  2  the products are fed in and the residues are extracted via airlocks which alternately and as required isolate the airlock  1  from the thermolysis chamber  2 , when the products are fed into the airlock  1 , and the thermolysis chamber  2  from the cooling chamber  3 , when the residues are extracted from this third chamber. 
     The thermolysis chamber  2  is thermally insulated to limit heat losses. 
     The chamber  2  is maintained at a constant pressure which can be in the range 200 mbars to 1.2 bars. The same set point pressure is preferably chosen in chambers  1 ,  2  and  3 . 
     The pressure is maintained, for example, by a pump station  10  communicating with the chamber  2  via an extraction line  11 . For simplicity FIG. 1 does not show the pump station in the cooling area and the airlock. 
     A cyclone  12  on the extraction line  11  supplied with water via a feed  13  divides the gases from the thermolysis chamber  2  into a fraction containing water and tars recovered in a pitch tank  14  and an uncondensed gas fraction. The uncondensed gas fraction is cooled in a cooler consisting of a tube type heat exchanger  15  through which a refrigerant flows downstream of the cyclone  12  on the extraction line  11 . 
     The thermolysis gases extracted from the chamber  2  are therefore cooled from a temperature of approximately 500° C. on leaving the chamber  2  to a temperature of approximately 80° C. in the cyclone  12  and then to a temperature of approximately 60° C. on leaving the heat exchanger  15 . 
     In particular, this separates the steam from the thermolysis gases, at least some of which are burned in a boiler  16  (see below). However, this cooling also has the advantage of protecting the conventional mechanical pump station  10  which would wear excessively if the gases they pump were at a temperature greater than approximately 80° C. 
     In this embodiment, a first part of the uncondensed gas fraction is burned in the boiler  16  and a second part of the uncondensed gas fraction is heated by means of the gases produced by combustion of said first part in the boiler  16 , this heated second part of the uncondensed gases being fed into the thermolysis chamber  2 . 
     To be more precise, in a first branch circuit, the first part of the uncondensed fraction is fed to the boiler  16  via an uncondensed thermolysis gas feed line  17  communicating with the first pump means  10  via a valve  18 . 
     A second thermolysis gas branch circuit consists of a recycling line  19  communicating with the extraction line  11  between the tube type heat exchanger  15  and the pump station  10 . The recycling line  19  is connected to the extraction line  11  via a distributor valve  20  at one end and a coil  21  in the flue of the boiler  16  at the other end. A second pump station  22  is also provided on the recycling line  19 , between the distributor valve  20  and the coil  21 , near the latter. 
     The outlet of the coil  21  communicates with a line  23  for feeding hot gas into the chamber  2 . The feed line  23  enables direct injection of the flow of hot gas heated in the boiler  16 , in the immediate proximity of the charge of solid products to be treated, by means of a hood  24  covering the wagon or wagons  25  in the chamber  2  during the thermolysis step. Note that in the conventional way the wagons are moved in the chambers  1 ,  2  and  3  by a mechanical rack and pinion type system A, for example, or an electromagnetic type drive system. The wagons are designed so that the solid residues—glass, debris, metals, for example—remain in the wagons  25  but are easily removable at the exit from the cooling chamber  3 . 
     Additionally, the feed line  23  also enables combustion gases to be fed into the boiler  16  or flue gases of the chamber  2  to dehydrate the charge of solid products to be treated prior to thermolysis. A dehydration line  26  provided for this purpose communicates with an exhaust line  27  for flue gases or combustion gases in the boiler  16 , via a regulator valve  28 , and with the feed line  23  via a connecting valve  29 . 
     The smoke leaving the boiler that is not used is sent via a fan  30  into a washer  31  for cleaning the flue gases before they are exhausted into the atmosphere. A second fan  32  is provided at the exit from the washer  31  to facilitate exhausting the clean flue gases into the atmosphere. 
     FIG. 1 also shows an exhaust line  33  for flue gases extracted from the chamber  2  during dehydration, connected at one end to the valve  18  and at the other end to the washer  31 . 
     To carry out the combustion the boiler  16  is equipped with fiber type burners  34 , which include a trellis of fibers. This type of burner is of special interest because it can burn gases that are relatively impoverished from the energy point of view. One such burner is the “BEKITHERM AC” type sold by ACOTECH. 
     Nevertheless, for situations in which the net calorific value of the thermolysis gases would be too low for correct combustion a feed line  35  for a liquefied gas, for example propane, is connected to the thermolysis gas feed line  17  via a feed valve  36 . 
     A storage tank  37  for storing thermolysis gas is connected to the feed line  17  between the valve  18  and the feed valve  36  via a connecting valve  38  so that combustion in the boiler  16  is not dependent on the instantaneous richness of the thermolysis gases from the chamber  2  or on the production of these gases with a net calorific value that is acceptable in terms of combustion performance. Compressor means (not shown) are also provided to compress the gases before they are stored in the storage tank  37 . 
     The combustion gases having a temperature of approximately 800° C., while dehydration is carried out at a temperature in the range 100° C. to 150° C., preferably around 120° C., a line  39  equipped with a heat exchanger to produce or to heat steam is connected to the feed line  23 . The heat energy recovered in this way can be fed in situ to a turbine (not shown) which converts it into electrical energy for driving the pump means  10  and  22  and the fans  30  and  32 , for example, or for any other purpose, possibly external to the plant. 
     A combustion-supporting oxygen line  40  is connected to the feed line  17  downstream of the liquefied gas feed line  35  via a connecting valve  41 . This line can carry pure oxygen or merely air. 
     The skilled person knows how to choose appropriate valves for use at the respective locations of the plant described with reference to FIG.  1 . 
     Note also that pressure and temperature control means, not shown, are installed on the various chambers  1 ,  2  and  3  and on the boiler  16 . Means for regulating the flow of gas to each burner on entering the boiler  16 , also not shown in FIG. 1, are provided at the input to the boiler  16 . The skilled person knows how to choose and use such control and regulation means and means for monitoring the quantity of oxygen in the boiler  16  or the quantity of hydrogen in the plant. 
     The valve  42  on the feed line  23  isolates and regulates the flow of gas from the lines  26  and  19 . 
     The solid residues leaving the cooling area  3  are wet treated to separate the fine minerals from the coal. The coal can be mixed with the tars recovered by settling out in the pitch tank  14  to make a combustible mixture. The combustible mixture can be burned in the boiler  16 , for example, or external to the plant, for example to produce electrical energy. 
     Operation 
     The treatment plant of the present invention, as shown diagrammatically in FIG. 1, operates in the following manner: 
     Solid products (for example domestic waste) contained in wagons  25  are passed in succession by means of any convenient conveying system A into and past the airlock  1  and into the thermolysis area or chamber  2 . 
     The boiler  16  is started up by combustion of liquefied gas only or, if thermolysis gases are present in the storage tank  37 , by combustion of the latter, or even by mixing the latter with liquefied gas in order to produce combustion or flue gases. The flue gases are sent via the dehydration line (via the feed line  23 ) into a chamber  2  for dehydrating the solid products, after they have been cooled in the line  39 . 
     The flue gases charged with steam and, where applicable, other gases produced by the corresponding heating, are aspirated through the exhaust line  11 , the cyclone  12  (essentially to condense the steam) and the tube type heat exchanger  15  by the pump station  10  and then sent at least in part via the exhaust line  33  into the washer  31  and finally discharged into the atmosphere. 
     In a second step of the treatment in accordance with the present invention, applied to the plant facility shown in FIG. 1, a flow of hot gas (at a temperature in the range 300° C. to 900° C.) is fed into the chamber  2  to thermolyze the solid products that have just been dehydrated, this thermolysis taking place at a temperature in the range approximately 250° C. to approximately 750° C. 
     The hot gases fed into the chamber  2  are enriched with hydrogen and hydrocarbons (methane, ethane, ethylene) on contact with the charge of solid products to be treated, which raises the net calorific value of these gases (in practise from 4 000 kJ/kg to 18 000 kJ/kg-19 000 kJ/kg), but also of other gases, in particular carbon dioxide, carbon monoxide, etc. 
     These gases are recovered at a temperature of approximately 500° C. on the extraction line  11  and are then aspirated by the pump means  10  into the cyclone  12  and the tube type heat exchanger  15  where the separation processes mentioned below are carried out. 
     Part of the uncondensed thermolysis gases leaving the exchanger  15  is sent into the storage tank  37  or directly into the boiler  16  for combustion and a second part is sent into the recycling line  19  where, after being accelerated by the pump station  22 , this second part of the gases is heated by passing it through the coil  21  and then fed via the feed line  23  into the chamber  2 . 
     Note that if the hot gases to be fed into the chamber  2  are at a temperature above approximately 650° C. the heat exchange line  39  could be used to lower the temperature, as during dehydration. 
     Furthermore, at the beginning of the thermolysis step a part of the flue gases extracted from the chamber  2  during dehydration or the flue gases from combustion of the thermolysis gases stored in the storage tank  37  could be used for recycling, sent via the dehydration line  26  into the feed line  23  and cooled to the required temperature. Note that in other embodiments thermolysis gases from the storage tank  37  could be used for this recycling by providing an appropriate branch connection to the recycling line  19 . 
     It will be seen that this plant facility increases the net calorific value and the richness of the gases each time they pass through the charge. 
     The solid residues, tars and flue gases are treated as mentioned above during this process. 
     FIG. 2 shows another embodiment in which elements similar to those from FIG. 1 are designated by the same reference numbers. 
     The principal differences between this plant and that from FIG. 1 result firstly from the choice to carry out dehydration in a chamber  1  separate from the thermolysis chamber  2  and fed with combustion gas (flue gases) from the boiler  16  via a dehydration line  26  independent of the feed line  23  and connected to the line  27  via a valve  58 . The line  23  includes at the location of the valve  59  an inlet  50  for combustion gas that can be mixed in a certain proportion with the thermolysis gases to be recycled via the recycling line  19 . 
     The plant facility then includes cooling and separation or division means disposed in a specific manner. Here, these means include a cyclone  12  which cools the gas from the thermolysis chamber  2  to a temperature in the range approximately 230° C. to approximately 330° C. Part of these gases is used in the recycling line  19  (branch connection at the location of the valve  20 ′) and another part of the gases, to be burned in the boiler  16 , is sent via a cooling line  51  into the tube type heat exchanger  15  to be cooled to a temperature in the range approximately 60° C. to approximately 80° C. 
     Note that the pump station  22 , which consists of a vacuum pump in the FIG. 1 plant facility, have been replaced by a fan. 
     On leaving the tube type heat exchanger  15  the liquid hydrocarbons (tars) and the water are sent into the pitch tank  14  via the output line  52 . An uncondensed gas recovery line  60  communicates with the exchanger  15  and with the pump station  10 . There is no fan at the exit from the washer  31  or on the flue gases output line  57 . The solid pitch formed in the cyclone  12  is also sent to the pitch tank  14 . 
     The recycling line  19  is fed via a line  53  with impoverished and cooled gas leaving the pump means  10  communicating with the tube type heat exchanger  15 . 
     The gases from the line  53  are at a temperature of approximately 50° C. and are mixed with the gases from the recycling line downstream of the fan  22 , enabling the gas to be recovered at a temperature in the order of 230° C. 
     Moreover, before it is mixed with the impoverished and cooling gases, a part of the gas flowing in the recycling line  19  is sent to the tube type heat exchanger  15  via a line  54  at the location of the valve  63 . In practise these gases are at a temperature of approximately 150° C. in this line and reach the input of the tube type heat exchanger  15  at a temperature of approximately 120° C. 
     This handles the overflow of thermolysis gas to be partially condensed. 
     Here the steam is produced or heated for subsequent exploitation not only on the dehydration line  26  but also on the line  54  (cf. lines  39  and  39 ′ in FIG. 2) and at the exit from the boiler  16  by means of the flue gases sent to the washer  31  through a heat exchanger  55 . 
     Finally, before entering the washer  31 , the flue gases from the dehydration circuit pass through a secondary washer  31 ′ and pump station  10 ′ maintaining the required pressure in the dehydration chamber  1  disposed on the dehydration flue gases line  56 . This prevents damage to the pump means  10 ′ and liquid hydrocarbons (tars) that can be exploited are recovered at the exit from the washer  31 ′ (arrow  57 ). 
     Because of these arrangements at least a part of the gases to be recycled is maintained at a temperature in the range approximately 230° C. to approximately 330° C., subject to the circuit being slightly more complex. 
     Otherwise, the operation of this plant is substantially to that described with reference to FIG.  1 . 
     FIG. 3 represents a preferred embodiment in which elements similar to those from FIG. 1 are designated by the same reference numbers. 
     The main differences of this plant relative to that from FIG. 1 are as follows: 
     The feed line  23  communicates directly with the interior of each of the wagons  25  via a coupling member or fluid connection  70 . 
     Each of the wagons  25  has a perforated bottom adapted to carry the charge of products to be treated and to transmit the hot gases to the charge. 
     The coupling member  70  can be a telescopic device moving a bellows fitted to one end of a tube to a connection area on the bottom of the wagon  25 , for example. 
     The wagon  25  can carry a grid to receive solid products to be treated, for example, or a tank with regularly distributed nozzles discharging onto the bottom of the tank and fluidically connected to the connection area by a system of tubes. 
     In this way the hot gases can be injected directly into the charge of waste to be treated, which in particularly reduces the risk of unburned waste due to intimate contact of the hot gases with the charge of waste to be treated, with no preferential pathways. 
     FIG. 3 shows guillotine doors  71  for isolating the chambers from each other. 
     To obtain areas as inert as possible at the doors  71 , steam is fed to these locations via the circuit  72 . 
     An area  4  for unloading the wagons  25  is provided after the cooling area  3 . The residues are tipped into a pool  73  from which they are then extracted and then sorted. 
     During the thermolysis step the gases in the chamber  2  are aspirated via the extraction line  11  at a temperature which in this preferred embodiment is approximately 330° C. 
     They are then passed through a tube type heat exchanger  75  as the hot fluid. 
     They leave it at a temperature in the order of 200° C. and are then fed via the recycling line  19  into various units of a fractionation system. 
     First the gases flow in a cooling circuit for separating heavy hydrocarbons. This circuit includes a contact cooling device  76 , known to the skilled person as an oil quench, a pump  77  and a heat exchanger  78 . 
     The recycling line  19  discharges into the bottom of the cooler  76 . 
     The pump  77  and the heat exchanger  78  are on a branch connection  19 ′ from the recycling line  19  which leaves the bottom of the cooler  76  and returns to the top of the cooler  76 . An offtake line  79  for heavy hydrocarbons is connected to the branch connection  19 ′ between the pump  77  and the heat exchanger  78 . The cold fluid of the heat exchanger  78  is water fed via the line  80 . This water is converted into steam which leaves via the line  81  connected to a steam exploitation unit (not shown). 
     The gases entering the cooler  76  are cooled by sprinkling heavy hydrocarbons previously recovered from the bottom of the cooler  76 , aspirated by the pump  77 , cooled in the heat exchanger  78  to a temperature in the range approximately 120° C. to approximately 130° C. and re-injected into the top of the cooler  76 . Thus heavy hydrocarbons are formed continuously and in part taken off via the line  79  and in part recirculated to the cooler  76 . The uncondensed gases leave the cooler  76  at a temperature of approximately 150° C. and are fed via the recycling line  19  into a condenser  82  which cools them to a temperature of approximately 45° C. 
     The condenser  82  is fed with a refrigerant flowing in a cooling circuit including a pump  83  and a fan  84 . 
     In other embodiments it can be replaced by a water quench. 
     The condensed products accumulate at the bottom of the condenser  82  and are extracted from the latter and fed into a separator  85  (of the lamellar settling tank type) to separate the light hydrocarbons from the water and the organic substances dissolved therein. 
     The light hydrocarbons are extracted via the line  86  and the aqueous phase is fed via the line  87  into another separator  88 , such as a distillation unit, to separate the water from the organic substances dissolved in it. 
     The water leaving the separator  88  is fed via a line  89  to water treatment plant and the soluble organic substances leaving the separator  88  via a line  90  can be fed from the line  90  to the boiler  16  to be burned in it. 
     In a similar manner, the light hydrocarbons can equally be fed from the line  86  to the boiler  16 . 
     The uncondensed gases leaving the condenser  82  at a temperature of approximately 45° C. are fed via the recycling line  19  into a water sprayer device  91  also known to the skilled person as a water quench. The device  91  washes the uncondensed gases to remove acids from them, such as hydrochloric acid. 
     To this end, water is circulated in the device  91  by means of a circuit  92  incorporating a pump  93 . The circuit  92  includes a branch connection  94  which feeds the spent water to water treatment plant, for example the plant mentioned above. 
     A first part of the uncondensed gases leaving the device  91  at a temperature in the order of 45° C. is re-injected into the heat exchanger  75  through a blower  95  which raises its temperature to approximately 100° C. 
     This part of the gases passes through the heat exchanger  75  as the cold fluid and leaves it at a temperature in the order of 300° C., after which it passes through a coil  21  in which the gases of this part of the uncondensed gases are heated to a temperature in the order of 650° C. by combustion gases from the boiler  16 . 
     On leaving the coil  21  the heated gases enter the feed line  23 . 
     Another part of the uncondensed gases is fed via the input line  17  to the boiler  16  in which it is burned to heat the part of the gases passing through the coil  21 . The gases are circulated in the line  17  by a fan  96 . 
     A third part of the uncondensed gases at a low temperature (approximately 45° C.) is injected into the cooling area  3  via an injection line  97 , to which a blower  98  is connected. 
     The hot gases recovered from this cooling area  3  are equally recovered on the extraction line  11 . 
     The hot gases in the offloading area  4  are also recovered and fed into the bottom of the cooler  76  via a recovery line  99 . 
     The combustion gases or flue gases produced by the boiler  16  are fed via a line  100  to a gas/gas heat exchanger  101  for heating the combustion-supporting air used by the boiler  16  and arriving via the line  102  entering the heat exchanger  101 . 
     Finally, natural gas or any other fuel (fuel oil, etc) for starting up the boiler reaches the latter via the line  103 . 
     To be able to burn all of the products mentioned above, the chamber  16  is equipped with multi-fuel burners. 
     In this plant facility, dehydration and thermolysis are carried out simultaneously and the treatment process is started by heating an inert gas (nitrogen, etc) or previously stored uncondensed gas. 
     Of course, the plant facility can be provided with uncondensed gas storage means for this purpose. 
     FIG. 3 does not show the pressure and temperature control means and other regulator valves. 
     A flue gases evacuation circuit similar to that from FIG. 1 can be provided for the FIG. 3 plant. 
     The gases escaping from the chamber  2  towards the airlock  1  on opening the door  71  can equally be recovered and fed into the line  99 . 
     These features protect the plant facility from the risk of coking resulting from the condensation of the tars, the risk of clogging by dust and the risk of corrosion by acidic gases. 
     A plant facility of this kind is particularly energy efficient and generates little pollution. 
     It goes without saying that the foregoing description has been given by way of non-limiting example only and that many variants can be proposed by the skilled person without departing from the scope of the invention. 
     In particular, the cyclone  12  and the tube type heat exchanger  15  can be replaced by a cyclowasher, i.e. a washer operating by sprinkling of water adapted to fulfill the functions assigned to the cyclone and to the tube type heat exchanger in the above description of the invention and in particular to lower the temperature of the uncondensed gas fraction to approximately 60° C. to approximately 80° C. 
     The coil  21  can be replaced by any equivalent gas/gas heat exchange means. 
     The coal extracted from the solid residues and the tars can be exploited separately.