FR2947044A1 - Device for drying sludge waste containing solvent obtained from treatment industry and cooling towers of nuclear plants, comprises evaporation unit, temperature lowering unit, solvent vapor proof drying enclosure, and transporting unit - Google Patents

Abstract

The device comprises a unit for partially evaporating the solvent to obtain a solvent vapor, a unit for lowering a temperature of the evaporation of the solvent, a solvent vapor proof drying enclosure to collect the waste, a unit for transporting the waste between an inlet area and an outlet area of the enclosure, a recovery unit (10) of a fraction of the solvent vapor, a unit for increasing a temperature of the fraction of solvent vapor to obtain a vapor fraction of increased temperature, an injection unit (24) in contact with the waste for drying it, and a heat desorption device. The device comprises a unit for partially evaporating the solvent to obtain a solvent vapor, a unit for lowering a temperature of the evaporation of the solvent, a solvent vapor proof drying enclosure to collect the waste, a unit for transporting the waste between an inlet area and an outlet area of the enclosure, a recovery unit (10) of a fraction of the solvent vapor, a unit for increasing a temperature of the fraction of solvent vapor to obtain a vapor fraction of increased temperature, an injection unit (24) in contact with the waste for drying it, and a heat desorption device for treating sludge waste. The temperature lowering unit comprises a depression unit to reduce the pressure (100-500 mbar) in the device for lowering the temperature for solvent evaporation. The evaporation unit comprises a heating unit for increasing the temperature of the waste for evaporating the solvent and then drying the waste, where the heating unit is embedded in the transporting unit. The transporting unit is constituted of a hollow worm screw in which coolant flows, where the hollow screw is intended for conveying the waste from the inlet and outlet areas and heating the waste with the coolant so that the temperature of the waste rises uniformly throughout the waste. The temperature of the waste is 140[deg] C so that the waste undergoes sterilization. A conduction heating of the waste is combined with convection heating to obtain a final waste having dryness of greater than 90%. Independent claims are included for: (1) a process for drying a waste containing a solvent; and (2) a computer program to execute drying process.

Description

The present invention relates to the general technical field of waste drying devices intended in particular for mass and / or volume reduction of these wastes. SUMMARY OF THE INVENTION The present invention relates in particular to the technical field of devices for drying waste containing a solvent, for example sludge from sewage treatment plants, industries or cooling towers of nuclear power plants.

The present invention more specifically relates to a device for drying a waste containing a solvent, the device comprising an evaporation means designed to generate an evaporation, at least partially, of the solvent, so as to obtain a solvent vapor. The present invention also relates to a method of drying a waste containing a solvent, said method comprising a step of evaporating, at least partially, the solvent, so as to obtain a solvent vapor.

The present invention further relates to a computer program comprising computer program code means adapted to perform the steps of a method of drying a waste containing a solvent, said method comprising an evaporation step, at least partially , solvent, so as to obtain a solvent vapor, when said program is run on a computer.

The present invention finally relates to a computer-readable medium on which is recorded a computer program adapted to perform the steps of a method of drying a waste containing a solvent, said method comprising an evaporation step at least partially of the solvent so as to obtain a solvent vapor. It is well known that the cooling circuits of nuclear power plants are at the origin of the formation of waste, especially in the form of sludge from B090525 / FR mainly air-cooling towers. These sludges form a particularly bulky waste, difficult to store and transportable in the state. In addition, sludge from these cooling circuits is potentially contaminating to the extent that it is likely to contain pathogens, including amoebae and bacteria, for example Legionellae. These pathogens are particularly virulent and can have serious consequences. they come into contact with humans, for example by ingestion, or if they are disseminated in the environment. It is therefore conventional to treat these sludges before storage or their future use, in order to reduce their size and disinfect them. Indeed, one of the major issues in the treatment of these sludges is, in particular, to make the latter non-hazardous in terms of contamination by pathogens, including trying to eradicate the pathogens they may contain.

There are various methods which aim to reduce sludge mass and / or at least partial destruction of pathogens in order to make the sludge safe from a health and environmental point of view.

Among these methods, liming is known which consists of an addition of quicklime, generally using a hopper, in sludge from nuclear power plants, in order to destroy the pathogens. Lime has good pest and disinfectant efficacy. In addition, it does not pollute and has a significantly positive impact on soils. However, this method, despite some efficiency for the disinfection of sludge, has a number of disadvantages.

Indeed, liming does not allow lime to come into contact with all the sludge, whereas the destruction of the pathogens by the lime can only be done by a direct contact of the latter with the said pathogenic agents. In particular, sludge from cooling towers have a dryness often greater than 15% and a low average viscosity rendering them substantially solid and therefore not conducive to effective contact with lime. B090525 / EN In addition, sludge from nuclear power plants is essentially mineral and the mineral particles they contain have a fast deposition rate of a few seconds to a minute, which causes considerable difficulties in maintaining the sludge in the form of a constant fluid in view of effective contact with lime. Therefore, this method does not allow total eradication of the pathogens contained in such a sludge.

Finally, liming considerably increases the volume of sludge, generally about 70%, since it adds lime to the latter without causing a reduction in the volume of the sludge, therefore. a lime treatment leads to a final waste volume and mass greater than the initial waste, which obviously induces additional costs of storage and / or subsequent treatment of the sludge. In order to overcome some of the abovementioned disadvantages associated with liming, it is known to apply a heat treatment to sludge from nuclear power plants, for example by subjecting these sludges to a stream of steam.

Among the various known steam heat treatment methods, there is a drying process which consists in passing steam through a layer of sludge disposed on an endless belt circulating in a drying chamber. This method comprises injecting steam under the carpet through openings 20 in the carpet so that the steam reaches the sludge so as to lick the sludge to increase its temperature. In particular, steam, which is indicated in this process with a temperature of the order of 75 ° C, partially evaporates the water contained in the sludge and destroy some pathogens. Thus, such a method is of interest on the one hand to reduce the mass and the volume of the initial sludge by increasing the dryness of the latter, and on the other hand to partially disinfect the sludge.

However, this drying process, if it reduces the mass of the sludge and destroy some pathogenic organisms of the latter, nevertheless presents a number of disadvantages. B090525 / FR In the first place, this process uses an external vapor source which requires a large energy input to provide the steam necessary for carrying out the process. Indeed, to allow the crossing of the sludge, especially when the latter has a thickness of several tens of centimeters, this process uses a large amount of steam, without guaranteeing the integral and homogeneous crossing of the sludge at any point. Therefore, this process is particularly energy consuming.

In addition, this drying process does not achieve a sufficient temperature of the sludge to eradicate with certainty all the pathogens contained therein. Indeed, the temperature of 75 ° C that it provides does not destroy all pathogens, for example helminth eggs resistant up to 100 ° C. Therefore, this process can not guarantee complete sterilization of sludge from cooling towers of nuclear power plants.

In addition, the presence of the carpet and the passage of steam through the latter do not allow effective and generalized contact of the steam with the sludge, especially if the thickness of the sludge on the carpet is important. Moreover, the spreading of the sludge on this carpet with a simple licking of the latter by the steam can hardly cause an increase in the temperature of the sludge in mass, especially at heart. Thus, this method provides no guarantee of a homogeneous rise in temperature, for a time and at a sufficient temperature, to eradicate all pathogens.

Finally, this process requires a long drying time, of the order of several tens of minutes, to allow the steam to pass through at least a portion of the sludge thickness disposed on the carpet.

The objects assigned to the invention therefore aim to remedy the various disadvantages listed above and to propose a new device for drying an energy-saving waste and ensuring a fast and efficient drying of the waste. Another object of the invention is to propose a new drying device using simple, inexpensive and easy to implement means that facilitate quick drying. Another object of the invention is to propose a new drying device which limits the energy losses.

Another object of the invention is to provide a new drying device for efficient and homogeneous core heating of the waste at any point.

Another object of the invention is to propose a new drying device which guarantees complete eradication of the pathogens contained in the waste.

Another object of the invention is to provide a new drying device for a temperature rise of the fast waste and low energy consumption. Another object of the invention is to propose a new drying device ensuring an effective reduction in the mass and volume of the waste.

Another object of the invention is to provide a new drying device that is adaptable quickly and simply to any type of waste and any waste storage area.

Another object of the invention is to provide a new drying device that allows the treatment of sludge of different origins, including sludge from purification plants and nuclear power plants.

Another object of the invention is to provide a new drying device that allows obtaining a waste easily recoverable or destructible at a lower cost.

Another object of the invention is to provide a new energy-efficient drying process and ensuring fast and efficient waste drying. Another object of the invention is to provide a new drying process comprising simple steps and quick to implement, and low energy consumption. Another object of the invention is to propose a new drying process which allows a fast and efficient reduction of the mass and the volume of the waste, while allowing a sterilization of the waste.

The objects assigned to the invention are achieved by means of a device for drying a waste containing a solvent, the device comprising an evaporation means designed to generate at least partial evaporation of the solvent, so as to to obtain a vapor of solvent, said device being characterized in that it comprises means for lowering the evaporation temperature of said solvent.

The objects assigned to the invention are also achieved by a method of drying a waste containing a solvent, said method comprising a step of evaporation, at least partially, of the solvent, so as to obtain a vapor solvent, said method being characterized in that it comprises a step of lowering the evaporation temperature of said solvent.

The objects assigned to the invention are furthermore achieved by means of a computer program comprising computer program code means adapted to perform the steps of a method of drying a waste containing a solvent, when said program is run by a computer. The objects assigned to the invention are finally achieved by means of a computer-readable medium on which is recorded a computer program adapted to perform the steps of a method of drying a waste containing a solvent.

Other objects and advantages of the invention will appear better on reading the description which follows, as well as with the aid of the attached drawings, given purely by way of illustration and without limitation, in which B090525 / FR - La figure 1 illustrates, in a schematic view, a drying device according to the present invention, according to a first preferred embodiment.

- Figure 2 illustrates, in a schematic view, a drying device according to the present invention, according to a second preferred embodiment.

The present invention relates to a device 1 for drying a waste containing a solvent, that is to say a machine or an installation designed to remove, at least partially, the solvent retained in the waste, so as in particular to reduce the mass and volume of said waste. In the sense of waste, advantageously means a product directly or indirectly derived from a production activity, for example an industrial process, and which is not usable as such. The waste is preferably intended to be processed for storage, recycling, reuse or subsequent destruction.

Preferably, the device 1 of the invention allows the drying of a waste whose composition varies between mostly mineral, for example a mud extracted from cooling towers of a nuclear power plant or a mud extracted from the recovery of rainwater called water satellite, and mostly organic, for example in the case of sewage sludge or from certain industries. The initial dryness of the sludge is advantageously substantially greater than 2%. The initial waste to be treated by the drying device 1 of the invention is therefore advantageously an at least partially organic waste, preferably a sludge. In the sense of sludge is advantageously meant a suspension of solid particles, for example inorganic or organic particles, in the solvent. Preferably, the drying device 1 of the invention allows the drying of any type of mud regardless of its shape, consistency, dryness, fluidity, viscosity, density, origin and / or its physical nature. -chemical. The device 1 advantageously makes it possible to treat sludges comprising a dryness substantially greater than 22%.

In the remainder of the description, mainly for the sake of clarity and brevity, it will be attempted to describe a preferred embodiment of the device 1 of the invention in which the latter constitutes a thermal desorption device 1 8090525 / FR intended the treatment of sewage sludge and / or sludge from industry and / or sludge from the cooling towers of nuclear power plants.

The thermal desorption device 1 of the invention is preferably designed to eliminate, at least in part, the solvent of the waste, here the sludge, in order to increase the dryness of the latter and thus to reduce the mass and the volume. The solvent contained in the sludge is advantageously water, present in greater or lesser amount. The invention is however not limited to water as the solvent of the waste and any other solvent, for example an oil, can also be envisaged without departing from the scope of the present invention.

The initial sludge intended to be dried by the drying device 1 are advantageously classified into three types: Type 1: fixed sludge, Type 2: loose sludge, so-called pellets, Type 3: liquid sludge.

The initial sludge is preferably retained in a storage means 6, prior to their pretreatment and / or drying. The drying device 1 advantageously comprises, as illustrated in FIG. 1, different storage means 6 depending on the type of sludge, for example a storage tank 6A for type 2 sludge, a tank 6B for sludge type 3, a 6C drum for type 1, 2 or 3 sludge, a 6D nuclear power plant cooling tower for type 3 sludge and a 6E skip for type 1 sludge.

When the sludge to be treated has a dryness substantially less than 22%, which is the case for example type 2 and 3 sludge, they advantageously undergo a pretreatment in the device 1, in particular by separation of at least a portion of the solvent . For this pretreatment of the sludge, the device 1 advantageously comprises a means for increasing the dryness 2 of said sludge (see FIG. 2) designed to separate and then remove at least a part of the solvent from the sludge, in particular in order to facilitate the subsequent drying of the latter. Preferably, the means for increasing the sludge dryness 2, preferably for the type 3 sludge,

B090525 / ffl comprises a centrifuge 2A fed directly from the storage means 6 (see references 6C and 6D of Figure 1) or by means of a screw pump 32. During this separation, a certain amount of water is advantageously introduced at the level of the centrifuge 2A, from the water of a local network 45 of water supply and with the aid of a water supply pump and flocculant 46, said water and said flocculant participating in the centrifugation of the sludge.

Alternatively, the means for increasing the dryness 2 of the sludge comprises a hydrocyclone 2B (see FIG. 1), advantageously used to pretreat the type-2 sludge. In the case of the use of the hydrocyclone 2B, the device drying device 10 preferably comprises a mixing means 40 designed to ensure a homogeneous mixture of the sludge, in particular of type 2, coming from the storage tank 6A. The mixing means 40, which is preferably a static mixer, is preferably supplied with water by a water storage means 41, for example a water holding tank, the water being transmitted from the storage means water 41 by means of mixture 40 by a feed pump 42 separated by a section valve 43 from the water storage means 41. The mixing means 40 of the sludge with water allows the hydration said sludge so as to facilitate the subsequent separation of the solid and liquid phases using the hydrocyclone 2B. Once out of the static mixer, the hydrated sludge is conveyed to the hydrocyclone 2B preferably using a feed pump 44.

Preferably, the pretreatment with the hydrocyclone, used when the dryness of the initial sludge is substantially less than 15%, preferably substantially between 7 and 15%, therefore first of all leads to hydration of the sludge with the addition of water in the mixing means 40 and then a mechanical separation of the solid and liquid phases in the hydrocyclone 2B.

It is also conceivable, without departing from the scope of the present invention, that the means for increasing the dryness 2 is alternatively any other means of mechanical separation of the solvent and solid particles of the waste, for example a filter press or a table drip. The means for increasing the dryness 2 of said sludge is thus advantageously designed to promote the production of a sludge having a dryness substantially greater than 22%, preferably substantially between 25 and 30% when the sludge is dry. use of the centrifuge and substantially between 50 and 60% with the hydrocyclone. Preferably, the waste that is pre-treated in the device 1 thus has a dryness substantially greater than 25%, preferably substantially greater than 50% before its main drying. Thus, irrespective of the initial dryness of the sludge in the storage means 6, the latter is easily treated by the device 1, such pretreatment further contributing, in addition, preferably to reducing the mass and the volume of the initial waste. .

Preferably, the water separated from the sludge during pretreatment, for example using the centrifuge 2A or the hydrocyclone 2B, is intended to be recovered and then treated so that the water obtained is clean, disinfected and compatible. with its reuse in a water system or with its release into the environment. For the treatment of the recovered water, the device 1 comprises a water retaining means 50 designed for the recovery of the water separated by the centrifuge 2A or the hydrocyclone 2B and transfer means 51, 52 ensuring transporting at least a portion of the water recovered from the means for increasing dryness 2 of the sludge to a means for storing and disinfecting the water 53 in which the water undergoes disinfection; storage and disinfection of water 53 advantageously comprises a storage unit 54 of at least one water disinfectant. Preferably, the disinfectant, which is advantageously a biocide that respects the environment and human health, is introduced, for example by means of an injection metering pump 55, into the storage and disinfection means of water 53, to disinfect the water before it is discharged by a disinfected water discharge pump 56 and a disinfected water discharge shut-off valve 57.

Preferably, the drying device 1 of the invention comprises, moreover, a drying chamber 3 intended to receive the waste and in which takes place, at least in part, the drying of said waste. The drying chamber 3 advantageously corresponds to a substantially closed chamber in which the main operation of drying the waste takes place. Preferably, the slurry, in the state or having undergone the aforementioned pretreatment, is introduced into the drying chamber 3 at a zone B090525 / FR of entry 3A of the drying chamber 3, at the using an introduction means 4, for example a hopper or an automatic feeder (see Figures 1 and 2).

Thus, the type 1 sludge is advantageously directly transported from the storage means 6, in this case 6E skips, in the direction of the drying chamber 3, in particular using a conveying means 60, for example a vacuum-proof conveyor (see reference 60 of FIG. 1), and a pump 61, for example a feed-through transfer pump (see reference 61 of FIG. The type 2 and 3 sludge, which has been pre-treated, is recovered at the outlet of the means for increasing dryness 2 and driven by means of a pump 62, for example a feed-through pump, to the medium 4 to be introduced into the drying chamber 3. The depression of the sealed conveyor 60 advantageously avoids any suspension in the air pathogens likely to be contained in the sludge and therefore the dispersion of these last, especially in case of rupture of the seal of said sealed conveyor 60.

The drying chamber 3 is preferably the main place for drying the sludge in order to obtain, at the outlet of the drying chamber 3, a final dried waste compatible with recycling, destruction or reuse. At the level of the drying chamber 3, the drying device 1 advantageously makes it possible to increase the sludge dryness very significantly, preferably by more than 30% with respect to its dryness value at the inlet, at the level of the the inlet zone 3A, in the drying chamber 3, so as to significantly reduce the volume of the initial sludge.

For this purpose, the drying device 1 comprises an evaporation means 5 designed to generate an evaporation, at least partially, of the solvent, so as to obtain a solvent vapor. In other words, the evaporation means 5 allows the solvent, which consists for example of water, to pass from a liquid phase to a gaseous phase, preferably in the form of water vapor, in order to dry said waste.

In an advantageous embodiment, the evaporation means 5 is mounted in the drying chamber 3 and the latter is substantially impervious to solvent vapor, that is to say that all the solvent vapor emitted during the drying of the sludge can not be discharged freely from the drying chamber 3. Preferably, only a central zone 3C of the drying chamber 3 is advantageously formed, which advantageously constitutes the drying zone as such , is vapor-tight. Thus, the drying device 1 comprises a drying chamber 3 intended to receive the waste and in which takes place, at least in part, the evaporation of the solvent produced by the evaporation means 5, for drying the sludge .

Preferably, the evaporation means 5 comprises a heating means 7 designed to raise the temperature of the waste so as to cause the evaporation of the solvent it contains and therefore the drying of said waste. In other words, the heating means 7 is advantageously mounted in the device 1, in particular in the drying chamber 3, to contribute to an increase, preferably in mass and in a homogeneous manner, of the temperature of the sludge. a level sufficient to cause evaporation of the solvent contained in said sludge. The heating means 7 thus makes it possible to supply the mud solvent with the vaporization energy necessary for its evaporation under predetermined conditions, that is to say at a given temperature and pressure. Preferably, the drying device 1 further comprises a transport means 8 of the waste in said drying chamber 3 between an inlet zone 3A and an outlet zone 3B of the latter. The transport means 8 is advantageously a worm mounted in the drying chamber 3 to convey the sludge during drying. In a particularly preferred embodiment, the heating means 7 is embedded in the conveying means 8, the conveying means 8 constituting a hollow worm 9 in which circulates a coolant, said hollow worm 9 being intended for part to convey said waste between the inlet zone 3A and the outlet zone 3B, and secondly to heat the latter with heat transfer fluid, so that the temperature of said waste rises from substantially homogeneous manner in any point of said waste.

The particular configuration of the invention in which the heating means 7 is directly associated with the transport means 8 advantageously has the advantage of moving the mass of sludge through the drying chamber 3, so that said mass B090525 / EN of sludge undergoes drying on the one hand on substantially the entire path separating the inlet zone 3A from the outlet zone 3B and on the other hand throughout its mass. The hollow worm 9 heated thus promotes a sufficiently long residence time of the sludge in the drying chamber 3, preferably substantially between 2 to 20 minutes, preferably substantially between 5 to 10 minutes, preferably at least equal to 7 minutes, to ensure drying of the latter compatible with a subsequent reuse of the sludge or with a destruction of the latter.

The hollow worm 9 preferably comprises a hollow core (not shown), that is to say a central empty part, in which is transported a fluid capable of transmitting a certain amount of heat to the sludge. In other words, the hollow worm 9 is heated by the heat transfer fluid and allows an increase in the temperature of the sludge in the drying chamber 3, by conduction, to allow evaporation of the solvent. The hollow worm 9 thus favors, preferably, a transmission of heat gradually to the mud, without displacement of material. The coolant used for the worm 9 is advantageously a heat conducting fluid having a high heat capacity and good chemical stability, which is non-corrosive and inexpensive. The heat transfer fluid advantageously transmits its heat energy to the sludge and has the advantage of being readily available and of having a viscosity at least equal to that of water, so as to come into prolonged contact with the walls of the sludge. the worm auger 9, to improve the speed and efficiency of heating the sludge. The coolant is for example an oiled. Alternatively, it is also conceivable that the coolant is of another nature, for example water vapor, without departing from the scope of the present invention.

The hollow worm 9 thus brings by conduction of heat to the heart of the mud, in the complete mass of the latter, the mud being advantageously conveyed in mass by said hollow worm 9. The latter, internally heated by the oil, therefore contributes, preferably, to a regular and harmonious rise in the temperature of the entire mass of the sludge, at a level sufficient to cause the evaporation of the solvent it contains and therefore the drying of said sludge. The screw without 8090525 / FR end hollow 9 is therefore preferably intended firstly to convey said waste, here the sludge, between the inlet zone 3A and the outlet zone 3B, and secondly to heat at heart last, preferably during its passage through the central zone 3C of the drying chamber 3, with the aid of the coolant, so that the temperature of said waste rises substantially homogeneously at any point of said waste.

Advantageously, the hollow worm 9 is mounted in the device 1 to raise, by conduction, the temperature of the waste to a value at least substantially equal to 100 ° C, preferably at least substantially equal to 140 ° C, so that said waste undergoes sterilization. In other words, the heating of the sludge by the device 1 ensures that said sludge reaches, at any point in its mass, for a sufficiently long time, preferably substantially between 2 to 20 minutes, preferably substantially understood. between 5 to 10 minutes, preferably at least 7 minutes, a temperature value incompatible with life or with a possible revivification of any pathogen, including Legionella, amoebae and helminth eggs, which are particularly dangerous and sometimes found in sludge from cooling towers of nuclear power plants.

In addition, the hollow auger 9, in addition to its role in heating and conveying the sludge, kneading, flattening and smoothing said mud, to break the clumps and to emote the latter . The hollow worm 9 thus provides, in a preferred manner, self-smoothing of the sludge which optimizes the exposure of said sludge to the heat flow. Advantageously, it also avoids any risk of jamming of the sludge in the drying device 1, substantially improving its conveying relative to prior drying devices 1 with a conveyor belt. Thus, unlike the state of the art in the field, the drying device 1 of the invention allows both a homogeneous and generalized heating of the sludge, the sterilization of the latter as well as its mechanical treatment, particularly by slicing . The device 1 of the present invention also comprises a means for lowering the evaporation temperature of said solvent, that is to say a means for reducing the temperature at which the solvent evaporates, under conventional conditions. that is to say at atmospheric pressure. In other words, the drying device 1 advantageously comprises a means for decreasing the boiling point of the solvent, so that the latter undergoes evaporation at a temperature below the evaporation temperature determined at the atmospheric pressure, that is to say at a pressure of 1 atm. Preferably, the means for lowering the temperature of the evaporation of the solvent comprises a vacuum means 27 (see FIGS. 1 and 2) intended to reduce the pressure prevailing in the drying device 3, in order to lower the temperature. evaporation of the solvent. Thus, the depression means 27 by reducing the value of the pressure that prevails in the drying chamber 3 preferably makes it possible to lower the boiling temperature of the solvent, so that the latter evaporates at a temperature less than its conventional boiling point at atmospheric pressure. The depression means 27 allows in particular to lower the vaporization energy, that is to say that it reduces the energy required for the solvent for evaporation of the latter.

Preferably, it is in the drying chamber 3 that the lowering of the evaporation temperature of the solvent produced by the means 26 for lowering the evaporation temperature of the solvent takes place, at least in part, and the evaporation of the solvent carried out by the evaporation means 5. Advantageously, the depressurizing means 27 acts together with the evaporation means 5, in the drying chamber 3, on the same quantity of sludge to be dried, preferably during the entire duration of the drying carried out in the drying chamber 3, that is to say during the entire duration of the transport of the sludge between the inlet zone 3A and the outlet zone 3B of the drying chamber 3.

Advantageously, the vacuum means 27 is intended to reduce the pressure in the drying device 3 from substantially 100 mbar to 1 bar, preferably from substantially 100 to 500 mbar. A slight reduction in pressure, of the order of a few hundred mbar, is advantageously sufficient to significantly reduce the boiling point of the solvent and thus improve the drying of the sludge. Preferably, the depression of the drying device 1 is carried out at the level of the drying chamber 3, in which the lowering of the evaporation temperature of the solvent and the drying of said waste takes place, at least in part. . Preferably, the depression of the drying chamber 3 thus reduces the temperature of the heat transfer fluid since the solvent evaporates at a lower temperature and / or 8090525 & FR to accelerate the evaporation of said solvent and therefore the drying mud, if the initial temperature of the coolant is maintained, since the solvent reaches its evaporation temperature more quickly. The vacuum means 27 preferably comprises a vacuum pump 28 connected to the drying chamber 3 by an orifice (not shown) and a pipe 29, said vacuum pump 28 being intended to perform a vacuum, at least partially, in the drying chamber 3, in particular in the central zone 3C, so as to contribute to a depression of said drying chamber 3. The drying chamber 3, in particular its central zone 3C, thus forms a decompression chamber designed to lower the evaporation temperature of the solvent and thus to accelerate the drying of the sludge.

The vacuum pump 28 is for example a piston pump, paddle or membrane. Alternatively, it is also conceivable, without departing from the scope of the present invention, that the vacuum means 27 is any means for reducing the pressure in the drying chamber 3 and other than the vacuum pump 28.

Such a vacuum means 27 allows for example, with a coolant temperature substantially equal to 85 ° C to cause evaporation of the solvent of the sludge when the latter reaches a temperature substantially equal to 45 ° C. Depression thus advantageously makes it possible to considerably reduce the temperature of the coolant fluid and thus to reduce the energy cost of operating the drying device 1. In a particularly preferred embodiment, the device 1 of the present invention further comprises a means for recovering at least a fraction of the solvent vapor, means for increasing the temperature of said solvent vapor fraction to obtain an increased temperature vapor fraction and an injection means waste of at least a portion of said increased temperature vapor fraction, so that the latter comes into contact with the waste to contribute to the drying of the latter.

Preferably, the recovery means 10 comprises a steam extractor 11 mounted at the drying chamber 3, preferably at the vapor-tight zone 8090525 / FR central 3C, to recover the solvent vapor released by the sludge during its heating by the worm 9. Preferably, the recovery of the steam by the steam extractor 11. is by suction and the recovery means 10 comprises a steam anti-return means 11A, for example a non-return valve, intended to prevent the steam captured by the extractor 11 to return to the drying chamber 3. The fraction of the extracted solvent vapor, for example sucked from the drying chamber 3 is then intended to be advantageously filtered by a filtration means 12 which is for example an absolute filter.

Preferably, the drying chamber 3, in particular its central zone 3C, is delimited by walls to form a substantially closed chamber. The solvent vapor created in the drying chamber 3 is advantageously sucked, at at least a first orifice formed in one of the walls of the drying chamber 3, by a suction means (not shown) belonging to the extraction means 10, then conveyed through a pipe also preferably part of the extraction means 10, to the means 13 for increasing the temperature.

The solvent vapor fraction is raised in its temperature increase means 13 which advantageously comprises an overheating means (not shown) for applying to said vapor superheat so that it has a substantially higher temperature. at the boiling point of the solvent, preferably substantially greater than 140 ° C, preferably substantially between 150 and 320 ° C, preferably substantially equal to 250 ° C.

Advantageously, the means 13 for increasing the temperature comprises a means 14 for compressing said solvent vapor, which makes it possible, by raising the pressure of the condensable fraction of the vapor recovered, to increase its temperature. Preferably, the steam is compressed so as to have a pressure of the order of several bars, preferably substantially greater than 2 bars.

Before the steam undergoes an increase in its temperature by compression, the drying device 1 advantageously comprises a means for separating the condensable fraction and the non-condensable fraction of the vapor. The non-condensable fraction B090525 / FR is preferably extracted from the drying device 1, in particular by means of a non-condensable vapor extractor 16, the said vapor fraction being subsequently washed by means of a washing means 17, for example a sprinkler. 'water. Once washed, said fraction of non-condensable vapor is preferably separated from its washing water by means of a water separation means 18, then filtered and finally discharged into the atmosphere, for example by means of a Extraction and discharge venturi 19. The water resulting from the washing of the non-condensable vapor is, for its part, preferably passed through a moisture extractor 20, then filtered, for example by means of a activated carbon filter 21, and finally discharged from the device 1, in particular using a reject pump 22 and a shutoff valve 23, in particular to reintegrate the water network of the site in which the drying takes place mud. The recovery and treatment of wastewater, which do not participate in the drying of the sludge itself or which are extracted from certain stages of the implementation of the drying device 1, and non-condensable vapor from the device of drying 1 contributes advantageously to make this drying device 1 clean, water-saving and environmentally friendly.

Once the vapor fraction is superheated using the compression means 14, it is introduced by the injection means 24 into the drying chamber 3, at the level of the vapor-tight central zone 3C, in direction of the sludge to participate in the drying of the latter, especially by convection. In fact, the steam injected by the injection means 24, because of its high temperature and its pressure, licks the sludge, that is to say that it comes against the sludge, in contact with the surface of the sludge. the latter, by convection, to participate in the evaporation of the solvent. The injection means 24 advantageously comprises an injector 24A through which the superheated steam is introduced into the drying chamber 3, the injector 24A comprising a steam circulation duct and a flap type non-return means intended to to prevent the return of the steam injected by the injection means 24.

The injected vapor, which has a temperature substantially greater than that of the sludge, preferably causes the temperature of said sludge to be raised to allow evaporation of the solvent and thus improves the drying of the latter already partly 8090525 Caused by the worm 9 heated. The hollow worm 9 advantageously plays a role of initiator of the evaporation of the solvent and drying of the sludge, the injection of steam into the drying chamber 3 after recovery and overheating, contributing, in turn, to the drying sludge by evaporation of the solvent and eradication of all pathogens from the sludge.

Advantageously, the injection means 24 is therefore intended to ensure an increase in the temperature of the latter by convection. Thus, the solvent vapor created in the drying chamber 3 is advantageously reinjected into the latter after having undergone recovery, separation and overheating treatment, preferably by at least a second orifice. By this reinjection, the drying device 1 is particularly energy efficient since it does not use an external source of steam production used for drying the sludge, unlike devices of the prior art.

Preferably, the fraction of superheated steam injected into the drying chamber 3 is saturated with water. The saturation of the steam is advantageously carried out using a saturation means 25, for example a superheated steam saturator including in particular a water sprinkler operating by steam spraying with water supplied by a cane of water. water supply 47 connected directly to the water storage means 41, so that the steam saturates with water. The water saturation of the steam makes the drying device 1 more safe and more effective, in particular by limiting the risk of explosion or auto-ignition and by making the efficiency of convective drying of the solvent vapor optimal reinjected.

Advantageously, the combination of a conductive drying provided by the hollow worm 9 and a convection drying provided by the injection means 24 of the solvent vapor makes it possible to obtain, preferably at the level of the outlet zone 3B, a final waste having a dryness substantially greater than 50%, preferably substantially greater than 30%, preferably substantially greater than 90%. In addition, the vacuum means 27 advantageously makes it possible to accelerate the drying of the sludge, in comparison in particular with prior drying devices which do not use a means for recovering and reinjecting the solvent vapor into the sludge. drying chamber 3. 8090525 / FR The drying device 1 therefore preferably allows a substantially complete drying and sterilization of the initial waste entering said device 1, thanks in particular to the use of temperature-time pairs defined according to the type of waste . Thus, advantageously, the sterilization that takes place within the drying device 1 is based on raising the temperature of the total mass of the sludge to a regulated value, at least equal to 120 ° C., for a period of time. defined by a correspondence chart for determining the sterilizing value of the waste to be treated. In other words, the drying device 1 makes it possible to establish the temperature and the necessary duration of drying according to the type of waste entering the device 1, the establishment of the temperature-time couples ensuring drying and sterilization of the products. waste, whatever the waste, while guaranteeing an energy saving. Preferably, the drying device 1 comprises a means for cooling the dried sludge (not shown), disposed at the outlet zone 3B of the drying chamber 3 or outside thereof. The cooling means advantageously makes it possible to reduce the temperature of the sludge so that the latter has, at the outlet of the drying device 1, a temperature compatible with its manipulation by man, for example substantially less than 45 ° C. Advantageously, the cooling means is mounted near or on the hollow worm 9 and comprises a sled-cooler of the sludge at the end of drying.

In a preferred embodiment, the final waste comprises sterility and dryness characteristics, preferably substantially greater than 90%, preferably substantially equal to 99%. The final waste advantageously has the form of thin dry rods, for example elongated granules conventionally referred to as pellets, the length of which is substantially between 1 and 2 cm. Alternatively, the dried sludge has a rounded granular shape or any other shape, geometric or not, without departing from the scope of the present invention. In an advantageous embodiment, the drying device 1 also comprises a grinding means 71 for the dried sludge, in particular granules 70, designed to reduce the granulometry of the sludge, in particular as a function of its subsequent use. Finally, the drying device 1 preferably comprises a bagging means 72 of the granules 70, designed to facilitate the transport, storage, use or subsequent marketing (e) of the granules 70.

Thus, the final waste, preferably granules 70, exhibits sterility characteristics with a total absence of pathogens and very high dryness, preferably substantially greater than 90%, which makes it compatible with use in a feedstock material. construction and / or as fuel and / or as agricultural fertilizer. The granules 70, bagged or not, are thus preferably used as is, or with certain adjuvants and / or fertilizers in agriculture, or incorporated in compositions for construction material. In addition, depending on the nature of the initial sludge, especially if it is particularly organic, the final dried sludge obtained by the device 1 is used as a fuel.

In a particularly advantageous embodiment of the present invention, the constituent elements of said drying device 1, for example the vacuum means 27, the heating means 7 and the drying chamber 3, are mounted independently of one another. other, so that the device is a drying device adaptable to any type of sludge drying. Preferably, the drying device 1, each of the main components of which is removable, removable and displaceable relative to the others, ensures the drying and sterilization of any type of sludge, closer to the place of production of said sludge . Indeed, whatever the conformation of the drying zone, whatever the place where the sludge drying must take place, whatever the type of sludge to be dried and whatever the size of the storage means 6 or the amount of sludge to be dried, the mobile drying device 1, removable, removable and easy to handle, guarantees a reduction in the mass and volume of the sludge and its sterilization, so as to be efficient, fast, economical in energy and respectful of the environment. Advantageously, the drying device 1 is shaped such that none of its constituent elements exceeds a footprint of more than 10 m 2. Such a mobile drying device 1 also advantageously avoids dangerous transport of sludge potentially infected with pathogens, without risk of diffusion and aerosolization of the pathogens they may contain.

The drying device 1 of the invention advantageously comprises a measuring means 80 of different parameters making it possible to know at any time the value of these parameters within said device 1. Preferably, the measuring means 80 comprises probes (cf. references 81, 82, 83, 84 in FIG. 1) intended to measure the pressure and the temperature prevailing in the drying chamber 3. It is also conceivable that the measuring means 80 comprise sensors and probes placed in different places of the drying device 1, for example in the centrifuge 2A and the hydrocyclone 2B.

Such measuring means 80 advantageously makes it possible to know certain values of several parameters (temperature, pressure, hygrometry, etc.), at any time, in important, dangerous and / or strategic locations of the drying device 1, so as to exercise a permanent control of the evolution of these parameters with a view in particular to operate an optimal and secure drying.

The drying device further comprises an electric power supply and control system 85 which preferably comprises a power source 86, a voltage regulator 87, a generator 88 and a control cabinet 89 for distribution, control and maintenance. regulation and security. Said cabinet 89 advantageously provides permanent control of the electrical distribution in the drying device 1 in order to optimize the use of electricity and to limit electrical risks as well as unnecessary electrical losses.

Advantageously, the drying device 1 comprises a computer system (not shown) designed to ensure, on the one hand, automated management of the operation of the drying device 1, in particular of its various constituent elements, and on the other hand a control permanent operation of said drying device 1. Preferably, the computer system centralizes the measured data by the measuring means 80 and makes it possible to establish flow charts of the various parameters to facilitate the monitoring and control of the drying of the sludge , for B090525 / FR a manipulator. The computer system also allows, preferably, to be able to trigger an alarm or an alert when one or more of the measured parameters has (have) exceeded a critical threshold value.

The drying device 1 of the present invention therefore advantageously allows a complete treatment of the sludge from their handling at their place of storage to their output in the form of dry granules and sterile. This drying device 1 makes it possible to advantageously ensure both the pretreatment of sludge, drying to reduce their size and sterilization, effectively, safely, energy-saving, environmentally friendly and secure in terms of manipulation and human health. The present invention also relates to a method of drying a waste containing a solvent. This drying process is advantageously carried out using the drying device 1 described above. Preferably, the drying process of the invention allows the drying and sterilization of any type of sludge, especially those types 1, 2 and 3 referred to above. According to a particularly advantageous embodiment, this drying process is a thermal desorption process for the treatment of sewage sludge and / or sludge from industry and / or sludge from cooling towers of nuclear power plants.

In practice, the sludge is stored preferentially in a storage means 6, for example a storage tank 6A, a tank 6B, a drum 6C, a cooling tower 6D nuclear power plant or a bucket 6E, depending on the origin and the nature of the mud. The drying process advantageously comprises a preliminary step of conveying said sludge from the storage means 6 to the drying device 1, in the drying chamber 3. If the nature of the sludge does not allow its drying in the state, the process advantageously comprises, before the conveying step, a pretreatment step in the course of which part of the solvent contained in the sludge is separated and removed from the sludge, for example using a centrifuge 2A or a hydrocyclone 2B, the operation of which has been described above. B090525 / FR The drying process of the invention comprises a step of at least partial evaporation of the solvent, so as to obtain a solvent vapor. This evaporation step advantageously takes place in the drying chamber 3, preferably in the central zone 3C of the latter, after the conveying step, that is to say once the sludge is introduced into the chamber. enclosure 3.

Preferably, the step of evaporating the solvent comprises a core heating operation by conduction, so that the temperature of the waste reaches a temperature substantially greater than 100 ° C, preferably substantially greater than 140 ° C, so to sterilize said waste. This heating step is preferably carried out using a hollow worm 9 heated by a heat transfer fluid.

In an advantageous embodiment of the process of the invention, the evaporation step comprises a convection heating operation which comprises a sub-step of recovering at least a fraction of said solvent vapor, then a sub-step of step of increasing the temperature of said solvent vapor fraction to obtain an increased temperature vapor fraction and a sub-step of injecting waste of at least a portion of said increased temperature vapor fraction, so that the latter comes into contact with the waste to contribute to the drying of the latter. The sub-step of recovery is carried out preferably by an extraction means 10. Preferably, the injection sub-step, advantageously implemented by injection means 24 of the injector 24A type, makes it possible to introduce the steam which has undergone an increase in its temperature in the drying chamber 3 near the waste.

The evaporation step therefore advantageously comprises a convection heating operation during which said at least a portion of said increased temperature vapor fraction comes into contact with the surface of the waste to promote a rise in the temperature of the mass. waste, preferably sludge, and thus contribute to the evaporation of the solvent.

In other words, the sludge introduced into the drying chamber 3 is dried both by conduction in its mass by means of the heated auger 9 and by convection thanks to a licking of the sludge operated by the reinjection into the drying chamber 3 B090525 / FR of the solvent vapor after the recovery and the raising of the temperature of the latter. Preferably, the heating step initiates the evaporation of the solvent which provides a solvent vapor subsequently used for the convective heating step. The combination of these two forms of heating ensures an optimal and fast drying of the sludge as well as an optimization of the energy consumed by recycling the manufactured solvent vapor, while guaranteeing the complete eradication of the pathogens and thus a sterilization of mud.

The drying process further comprises a step of lowering the evaporation temperature of said solvent, so as to accelerate the drying of the sludge and / or to reduce the energy supply necessary for drying said sludge. The step of lowering the evaporation temperature of the solvent advantageously comprises a vacuum operation of the drying device 1 in which takes place, at least in part, the drying of said waste, said depression operation being intended to reduce the pressure of drying device 1, preferably of a drying chamber 3 in which the evaporation of said solvent is predominantly carried out.

Advantageously, the depression operation of said drying device comprises a substep of pumping air and / or any other gas contained in said device, so as to reduce the pressure from substantially 100 mbar to 1 bar, preferably from substantially 100 to 500 mbar.

This step allows the heating chamber 3 to be depressurized, preferably of its vapor-tight central zone 3C, so as to accelerate the drying of the sludge by lowering the evaporation temperature of the solvent. Preferably, the depressurization step is concomitant with the heating step and particularly promotes the speed of the latter. The pressure of the central zone 3C is advantageously lowered during the entire duration of the drying of the sludge in the drying chamber 3.

Preferably, the evaporation step makes it possible to obtain a final waste comprising sterility and dryness characteristics, preferably substantially greater than 90%, which make the final waste compatible with use in a building material and / or in as fuel and / or as an agricultural fertilizer. The evaporation step, in particular thanks to the heating of the sludge, allows B090525 / FR thus to obtain a dried sludge of reduced and sterile volume that can be used in various fields. The initial sludge thus preferably becomes a valuable waste by the drying process of the present invention.

After the evaporation step, the process advantageously comprises a cooling operation to reduce the temperature of the sludge to facilitate subsequent handling. The method finally finally comprises a step of grinding the dried mud obtained, for example in the form of granules, and bagging thereof. The dried sludge resulting from the drying process, bagged or not, is then transported to its subsequent recovery point.

In a particularly preferred embodiment, the process of the invention also comprises an operation for recovering wastewater or non-condensable vapors, with a view to their treatment and their disinfection for their own evacuation into the environment or into a network. 'water. This drying process thus advantageously comprises means for recycling, recovery, treatment and disinfection, intermediate or final products, preferably water and water vapors, created during the implementation of said process, in such a way that to respect the environment and human health.

All the steps of the drying process are substantially automated and controlled by the computer system set forth in the foregoing. Preferably, the drying process of the invention requires little human manipulation, a single agent can perform all of the steps from the evaporation step.

This method advantageously allows a substantially complete drying as well as the sterilization of the initial waste, in a manner that is both environmentally friendly, energy efficient, fast and efficient. In addition, it considerably reduces the mass and the volume of the initial waste since it can make it possible to obtain a dryness of the sludge of more than 90%, preferably substantially equal to 99%. Indeed, this process has the advantage of not generating a final waste and intermediate by-products whose mass and volume are in total greater than the mass and the volume of the initial waste, which is particularly the case with the liming. B090525 / FR This method therefore allows a positive mass balance, producing a final waste whose mass and volume are as small as possible compared to the initial waste.

This process also advantageously has an optimized energy balance, especially through the reuse of steam, the depression of the drying chamber 35 and the supersaturation of the reinjected vapor. The present invention finally relates to a computer program comprising computer program code means adapted to perform the steps of a drying method according to the above when said program is executed on a computer. The computer program of the present invention is designed to manage all stages of the sludge drying process from the storage of the sludge until it is fully dried. The computer program advantageously provides the implementation of the computer system, so as to ensure automated and secure operation of the drying device 1, for optimum drying of the sludge. Finally, the present invention relates to a computer-readable medium on which is recorded a computer program adapted to perform the steps of a drying process and in accordance with the above-mentioned method.

The drying device as well as the drying method and the computer program of the present invention have the advantage of ensuring optimized drying and sterilization, respectful of human health and the environment, efficient and secure of a waste, in order to obtain a final waste reduced in mass and volume, sterile and recoverable in different fields. 8090525 / EN

Claims (19)

CLAIMS1 - Device for drying (1) a waste containing a solvent, the device (1) comprising an evaporation means (5) designed to generate an evaporation, at least partially, of the solvent, so as to obtain a vapor of solvent, said device (1) being characterized in that it comprises means for lowering (26) the evaporation temperature of said solvent. 2 - drying device (1) according to claim 1 characterized in that the means for lowering (26) the solvent evaporation temperature comprises a vacuum means (27) for reducing the pressure in the device of drying (1), in order to lower the evaporation temperature of the solvent. 3 - drying device (1) according to claim 2 characterized in that the depression means (27) is intended to reduce the pressure in the drying device (1) from substantially 100 mbar to 1 bar, preferably from substantially 100 at 500 mbar. 4- Drying device (1) according to one of claims 1 to 3 characterized in that it comprises a drying chamber (3) for receiving the waste and in which take place, at least in part, the lowering the evaporation temperature of the solvent produced by the lowering means (26) of the evaporation temperature of the solvent and the evaporation of the solvent carried out by the evaporation means (5), said drying chamber (3) being substantially impervious to solvent vapor. 5 - Drying device (1) according to claim 4 characterized in that it comprises a means of transport (8) of the waste in said drying chamber (3) between an inlet zone (3A) and an exit zone (3B) of the latter. 6 - drying device (1) according to one of claims 1 to 5 characterized in that the evaporation means (5) comprises a heating means (7) designed for B090525 / FR elevate the temperature of the waste so as to cause evaporation of the solvent that it contains and thus the drying of said waste. 7 - drying device (1) according to claims 5 and 6 characterized in that the heating means (7) is embedded in the transport means (8), the conveying means (8) constituting a hollow worm ( 9) in which circulates a heat transfer fluid, said hollow worm (9) being intended firstly to convey said waste between the inlet zone (3A) and the outlet zone (3B), and secondly to heat the latter with the heat transfer fluid, so that the temperature of said waste rises substantially homogeneous in any point of said waste. 8 - drying device (1) according to claim 7 characterized in that the hollow worm (9) is mounted in the device (1) for raising, by conduction, the temperature of the waste to a value at least substantially equal to 100 ° C, preferably at least substantially equal to 140 ° C, so that said waste undergoes sterilization. 9 - Drying device (1) according to one of claims 1 to 8 characterized in that it comprises a means for recovery (10) of at least a fraction of said solvent vapor, a means of increase (13 ) the temperature of said solvent vapor fraction to obtain an increased temperature vapor fraction and an injection means (24) to the waste of at least a portion of said increased temperature vapor fraction, so as to that the latter comes into contact with the waste to contribute to the drying of the latter. 10 - Drying device (1) according to claims 8 and 9 characterized in that the combination of a conductive drying provided by the hollow worm (9) and a convection drying provided by the injection means (24) solvent vapor provides a final waste having a dryness substantially greater than 50%, preferably substantially greater than 80%, preferably substantially greater than 90%. 11 -Dispositif drying (1) according to claims 2, 4 and 6 characterized in that the constituent elements of said device (1), for example the means of 80905251FRdepression (27), the heating means (7) and the enclosure dryer (3), are mounted independently of each other, so that the device (1) is a drying device (1) adaptable to any type of sludge drying. 12 -Dispositif drying (1) according to one of claims 1 to 11 characterized in that it allows the drying of a waste whose composition varies between mostly mineral and mostly organic, and whose initial dryness is substantially greater than 2%. 13 -Dispositif drying (1) according to one of claims 1 to 12 characterized in that it constitutes a thermal desorption device (1) for the treatment of sludge treatment plant and / or sludge from the industry and / or sludge from cooling towers of nuclear power plants. 14 -Dispositif drying (1) according to claims 8 and 10 characterized in that the final waste comprises characteristics of sterility and dryness, preferably substantially greater than 90%, which make it compatible with use in a building material and / or as a fuel and / or as an agricultural fertilizer. A method of drying a waste containing a solvent, said method comprising a step of evaporating, at least partially, the solvent, so as to obtain a solvent vapor, said method being characterized in that it comprises a step lowering the evaporation temperature of said solvent. 16 - Drying method according to claim 15 characterized in that the step of lowering the evaporation temperature of the solvent comprises a vacuum operation of a drying device (1) in which takes place, at least in part drying said waste, said vacuum operation being intended to reduce the pressure of the drying device (1), preferably of a drying chamber (3) in which the evaporation of said solvent is predominantly carried out. B090525 / EN 17 - Drying method according to claim 16 characterized in that the depression operation of said drying device (1) comprises a substep of pumping air and / or any other gas contained in said device (1) , so as to reduce the pressure from substantially 100 mbar to 1 bar, preferably from substantially 100 to 500 mbar. 18 -Drying method according to one of claims 15 to 17 characterized in that the solvent evaporation step comprises a core heating operation by conduction, so that the temperature of the waste reaches a substantially higher temperature at 100 ° C, preferably substantially greater than 140 ° C, to sterilize said waste. 19 - Drying method according to one of claims 15 to 18 characterized in that the evaporation step comprises a convection heating operation which comprises a substep recovery of at least a fraction of said solvent vapor then a sub-step of increasing the temperature of said solvent vapor fraction to obtain an increased temperature vapor fraction and a sub-step of injecting at least a portion of said vapor fraction into the waste of increased temperature, so that the latter comes into contact with the waste to contribute to the drying of the latter. -Drying method according to one of claims 15 to 19 characterized in that it constitutes a thermal desorption process for the treatment of sludge treatment plant and / or sludge from industry and / or sludge from cooling towers of nuclear power plants. 21 -Drying method according to one of claims 15 to 20 characterized in that the evaporation step provides a final waste comprising characteristics of sterility and dryness, preferably substantially greater than 90%, which make final waste compatible with use in a building material and / or as a fuel and / or as an agricultural fertilizer. 22 - Computer program comprising computer program code means adapted to perform the steps of a drying method according to B090525 / FRa one of claims 15 to 21 when said program is run on a computer. 23. A computer-readable medium on which is recorded a computer program adapted to perform the steps of a drying process and according to claim 22. B090525 / FR