FR2785835A1 - Reactor for incinerating waste has offset fixed plates, device for pushing waste across plates and indirect heating device for the waste - Google Patents

Abstract

The reactor comprises at least two fixed plates (10,11), offset relative to each other so the waste falls from the end of one plate onto the lower plate by gravity. A device for pushing the waste slowly across the plates has a chain conveyor driving a number of scrapers across the plates. An indirect heating device is placed below the plates to heat the waste. The reactor has inlets (3) and outlets (4) for the waste, and a device (5-9) for extracting the gases produced during incineration. The plates are trough-shaped and have raised and sloped side edges. The scrapers have a profile which fits that of the plates. Each chain conveyor drives the waste across two adjacent plates. The heat is provided by electrical resistance assemblies and the heating device is divided into several zones spread over the distance the waste travels. The reactor may contain three modules: an inlet and outlet module with inlets and outlets and one end of at least one of the chain conveyors; an intermediate module supporting part of the fixed plates, and a return module including the opposite end of the chain conveyor and the means of driving it.

Description

THERMOLYSIS REACTOR
Technical area
The invention relates to the field of the waste treatment industry, and more specifically to the treatment of waste by thermolysis. It relates more particularly to the structure of a thermolysis reactor allowing the optimization of the thermolysis of the waste to be treated.

Prior Techniques
As is known, thermolysis consists in treating waste comprising an organic fraction by exposing it to a very high temperature of the order of 500 C or higher.

 The Applicant has in particular described in document FR 2 725 643 a thermolysis installation including in particular a reactor of inside of which the decomposition takes place at high temperature.

 There are several families of thermolysis reactors, each operating on different principles.

 Thus, in a first family of reactors commonly called "semi batch", the waste is introduced and remains stationary inside the reactor throughout the duration of the treatment. This type of reactor, if it is very simple in design, on the other hand has the major drawback of not ensuring a core dissociation of the waste and of ensuring only a partial thermolysis of the waste.

 A problem which the invention proposes to solve is therefore that of the complete thermolysis of the waste, by ensuring total elimination of the organic fraction contained in the waste to be treated.

 Furthermore, a second family of thermolysis reactors is known which consists of a rotating enclosure inside which the waste is deposited. When the enclosure is rotated, like a drum, the waste is roughly stirred and heated.

 This type of installation has multiple drawbacks, in particular the generation of dust which is entrained by the gases formed during thermolysis, and which therefore pollute the gas phase coming from the reactor.

 In addition, the use of rotating enclosures requires special arrangements in terms of sealing, which make such an installation complex.

 Finally, with this type of installation, it is extremely difficult to treat waste with a sticky consistency, since the latter freeze on the wall of the reactor, preventing any mixing and therefore complete thermolysis.

 Another problem which the invention proposes to solve is that of entraining waste dust by the gases produced during the thermolysis process.

 Another problem which the invention proposes to solve is that of the adaptability of a reactor to many types of waste, and in particular sticky or clogging products.

 Another problem which the invention proposes to solve is that of the simplicity of a thermolysis installation.

 Another family of reactors is also known, such as in particular that described in the Applicant's document WO 96/11742. Such a reactor includes a plurality of endless screws ensuring a waste path along a path allowing almost complete thermolysis.

 Although satisfactory, such a reactor does not make it possible to treat waste of heterogeneous size, and moreover, presents certain risks of blocking of the drive system in the event that too much waste has accumulated in a localized area. a drive screw.

 Another problem which the invention proposes to solve is that of the adaptability of a reactor to waste of various sizes.

Statement of the invention
The invention therefore relates to a waste thermolysis reactor, comprising - waste inlet and outlet ports; a device for extracting the gases produced during thermolysis.

This reactor is characterized in that it comprises: at least two fixed trays on which the waste travels, the trays
being offset from each other in such a way that when the
waste reaches one end of a tray, it falls by gravity onto the
lower shelf; a device for driving waste on the trays comprising at least one
chain conveyor driving a plurality of doctor blades, rubbing on said
trays;
an indirect heating device arranged above and below said
trays, for heating waste.

 In this way, the routing of waste, during thermolysis, is carried out with a minimum of disturbances, which greatly limits the risks of seeing dust of waste entrained by the gases produced during thermolysis.

 In addition, the use of a chain conveyor associated with scrapers makes it possible to advance the waste at a very easily adjustable speed, while ensuring, thanks to the shape of the scrapers, mixing of the product and concomitantly self-cleaning of the trays on which move the waste.

 This therefore makes it possible to ensure the thermolysis of products of a large dimensional variety, only limited by the width of the plates.

 The use of a doctor blade also allows the treatment of waste having large varieties of consistency, which makes the reactor particularly suitable for the treatment of sticky or sticky waste.

 In addition, throughout the course of the waste on the trays, the heating is provided by a heat source causing heating of the product by radiation and by conduction.

 In addition, taking into account the course of the waste, the hot thermolysis gases provide additional heating of the materials to be thermolyzed by convection.

 In a particular embodiment, the fixed plates have the shape of a bucket, and have their raised and inclined lateral ends. In this way, the reactor according to the invention makes it possible to treat waste of very varied consistency, in particular sludge or more generally waste having a quasi-liquid consistency.

 In addition, the inclined profile of the lateral ends of the plates makes it possible to protect the drive mechanism of the chain conveyor and thus minimize the risk of fouling.

 Advantageously in practice, the doctor blades of the drive device have a profile complementary to that of the plate, and this to ensure permanent self-cleaning, even in the case where the conveyed waste is of almost liquid consistency.

 In an advantageous embodiment, each chain conveyor drives the waste on two adjacent trays. In other words, the doctor blades move the waste on a tray, for example the upper tray, and in their return journey, they entrain the waste on the directly adjacent tray.

 In this way, the structure of the installation is optimized by making the doctor blades active, including in their return path.

 Advantageously in practice, the heating device consists of a set of electrical resistors. However, without departing from the scope of the invention, a heating device using another source of energy, such as gas, could be used.

 Advantageously, the heating device is divided into several zones distributed along the path of the waste.

 In other words, thanks to this arrangement, it is possible to modulate the heating power during the routing of the waste in order to optimize the phenomenon of thermolysis, and in particular to ensure complete thermolysis.

In a particular form of construction, the reactor according to the invention consists of the assembly of at least three modules, namely:
an inlet and outlet module, including the inlet and outlet ports of the
waste, and comprising one end of at least one of the conveyors to
chain, as well as part of the trays on which the waste flows;
. at least one intermediate module supporting part of the plates
fixed;
. a turning module, comprising the opposite end of said
chain conveyor, and the associated flow tray part.

 In other words, in accordance with the invention, it is possible to produce thermolysis reactors of variable capacity by increasing the number of intermediate modules ensuring the actual heating, while retaining, for the same range of reactors, input modules / exit and turnaround identical.

 In other words, thanks to a unique design, it is extremely easy to vary the capacity of waste to be treated by adapting the number of modules to the treatment needs of the complete thermolysis installation. This variation in capacity is also possible by adapting the width of the modules as well as the drive speed of the chain conveyor.

 Advantageously in practice, the turning module further comprises means for driving the chain conveyor (s).

Brief description of the figures
The manner of carrying out the invention, as well as the advantages which ensue therefrom, will emerge clearly from the description of the embodiments which follow, with the support of the appended figures in which:
Figure 1 is a summary perspective view of a reactor according to the invention, in which the side wall has been removed to leave the interior of the reactor visible.

 Figure 2 is a side view of the reactor of Figure 1.

 FIG. 3 is a median cross section of the reactor of FIG. 1.

 Figure 4 is a schematic side view of the platens and the chain conveyor.

Way of realizing the invention
As already said, the invention relates to a thermolysis reactor intended in particular to be integrated into a waste treatment installation.

 The reactor according to the invention can be produced as illustrated in FIG. 1, in which it is shown without the cowlings constituting the side wall to leave the internal mechanism of the reactor (1) visible.

 Thus, this reactor essentially consists of an enclosure (2) inside which the thermolysis reaction takes place.

 The waste intended to be treated is brought into the enclosure (2) through the inlet orifice (3) located on the top of the enclosure (2). The waste, after its thermolysis is extracted from the enclosure (2) through the outlet orifice (4) located at the bottom of the enclosure (2).

The enclosure (2) has, in the upper part, a plurality of openings (5, 6, 7, 8) intended to be connected with an extraction manifold (9) of the gases produced during thermolysis.

 These openings (5-8) intended for extraction are located in the upper part of the enclosure to ensure extraction of the thermolysis gases with a minimum of dust.

 In known manner, the extraction manifold (9) is connected to a suction device which it is not necessary to describe further.

 The reactor is designed so as to be able to work optionally under reduced pressure, and can therefore be equipped, in an advantageous form, with inlet and outlet locks not shown upstream and downstream of the inlet and outlet orifices (3 , 4) waste.

 According to a characteristic of the invention, the reactor comprises at least two fixed plates (10,11) on which the waste travels.

 These trays (10,11) are arranged offset relative to each other so that when the waste reaches the end (12) of the tray (10), they fall by gravity onto the tray ( 11) located below.

 In this way, the waste performs a path substantially equal to twice the length of the reactor, which ensures sufficient passage time for complete thermolysis.

 Obviously, the invention is not limited to the form illustrated in FIGS. 1 and 2, in which the reactor comprises a single pair of plates, but on the contrary covers the variants in which several pairs of plates are present, it being understood that these plates are then arranged to ensure a routing of the waste with a transfer by gravity on the plates lower at the level of each end.

 More precisely, these plates (10, 11) are constituted by sections in the form of buckets with inclined ends (28), that is to say having a substantially trapezoidal shape, as illustrated in FIG. 3.

 Thanks to the use of this form of bucket, the reactor is capable of treating waste of very varied consistency, and in particular quasi-liquid waste such as sludge.

 The drive of the waste on the plates (10,11) is ensured by a chain conveyor (15) driving a plurality of doctor blades (16) rubbing on the two plates (10,11). The conveyor chain (15) is rotated by a conventional mechanism, which need not be detailed further.

 This mechanism rotates the axis (17) of the wheel (18) located in the example illustrated in Figure 2 opposite the inlet and outlet ports (3,4) of the waste. This wheel (18) is arranged so as to be able to drive the chain (15), and for example consists of a toothed wheel. The opposite end of the chain conveyor also has a gear wheel (19) also notched.

 It is quite obvious that the drive mechanism of the chain conveyor can be mounted either on one or the other of the ends (18, 19) of the conveyor, depending on the constraints of overall space requirement of the reactor.

 This chain (15) receives over its entire length a plurality of doctor blades (16) intended to rub the plates (10, 11) to entrain the waste.

 These doctor blades (16) have a geometry complementary to that of the plates (10,11) to ensure a drive of all the waste present on the plate, and also to ensure a self-cleaning of the plate during their passage.

 When the doctor blades (16) push the waste material, they cause a mixing effect of the waste layer, which allows thermolysis of the entire product, in particular avoiding the formation of crusts, and homogenizing the waste as they progress.

 In an advantageous form, to improve the mixing of the waste during the action of the doctor blade (16), the latter can have an optimized angle of attack. The materials chosen to make the plates as well as the doctor blades are metal alloys determined for their resistance to corrosion, in particular to chlorine fumes during thermolysis, as well as to erosion phenomena during the treatment of abrasive waste.

 Advantageously, a single conveyor is used for the pair of trays (10,11). Thus, the doctor blades (16) which drive the waste onto the upper plate (10), when they pass the wheel (18), turn over and ensure the drive of the waste onto the lower plate (11).

 In other words, when passing over the upper plate (10), the edge (22) of the doctor blade is active, while when the doctor blade (16) cooperates with the plate (11), the opposite edge (23) of the doctor blade is look of the plate (11).

 Thus, in the illustrated form, the doctor blade has a symmetrical shape imposed by the identical shape of the plates (10, I 1).

 According to another characteristic of the invention, the reactor is equipped with indirect heating means, arranged above and below the plates (10, 11).

 In an advantageous form, these heating means are constituted by electrical resistors (30,31,32). In this way, optimized heating is provided by using different types of heat transfer.

 Thus, the resistors (30) located above the plate (10) provide heating of the waste which passes through it by radiation. The resistors (31) located below the plate (10) ensure, in addition to the radiant heating of the material circulating on the plate (11), a conduction heating of the material moving on the plate (10). In addition, thanks to the thermolysis gas suction device, a flow of hot gas traverses the plate (11) against the current, ensuring heating by convection.

 Indeed, the location on the top of the reactor of the extraction device (9) obliges the thermolysis gases produced on the plate (11) to travel countercurrently in the small volume located above the plate (11). The waste arriving at the end of thermolysis on the lower plate, and which is relatively pulverulent can give rise to entrainments of dust by the thermolysis gases.

 The grouping of these gases in the restricted volume located above the plate (11) greatly limits the risk of the dust reaching the extraction device (9).

 Thus, a complete thermolysis is ensured, until completely treated products are obtained while greatly limiting the risks of pollution of the extracted gases.

 According to another characteristic of the invention, the heating device is divided into several zones distributed along the path of the waste.

 In other words, the various electrical resistances distributed along the plates (10, 11) can be supplied independently to ensure modular power distribution along the path of the waste.

 In practice, it may be advantageous to provide moderate heating at the start of the waste route to avoid too rapid degradation of the latter, and also to remove the residual moisture in the first treatment phase.

 Subsequently, it may be advantageous for certain waste to increase the heating power in the second part of the upper plate (10) to induce most of the rise in temperature and cause the emanation of thermolysis as close as possible to the extraction device (9).

 As regards the lower plate (10), in the same way the heating device can be regulated according to several zones, according to the thermal requirements.

 The different heating powers are calculated and optimized to possibly ensure that at the time of the fall (F 1) of the waste from the tray (10) to the tray (11) as illustrated in FIG. 4, this waste is not too much pulverulent, to limit the risk of dust entrainment.

 In an advantageous form, the heating powers can be dynamically adapted by temperature probes (38, 39) present in the reactor.

 According to another characteristic of the invention, the reactor according to the invention consists, in a modular manner by the assembly of at least three modules, determined so as to allow easy adaptation of the reactor to several capacities according to the treatment facility needs.

 Thus, in practice, the reactor as illustrated in FIG. 2 comprises a first input / output module (50) including the waste inlet and outlet ports (3,4), as well as the freewheel ( 19) of the chain conveyor.

 At the opposite end of the reactor, there is a turning module (51) in which the driving function of the chain conveyor is ensured by the wheel (18) and the rotation mechanism (not shown).

 Between these two end modules (50 and 51), is arranged at least one intermediate module in which the thermolysis process itself is carried out. These modules (51, 52,53) three in number in the illustrated variant, each include a fraction of the upper and lower plates (10,11) as well as orifices (5,6,7,8) for extracting gases thermolysis.

 Thus, as a function of the desired capacity, that is to say of the volume or of the weight of the material to be thermolyzed, in a given duration and a given flow speed, the reactor comprises an optimal number of intermediate modules.

 In practice, the reactor according to the invention makes it possible to treat waste of a wide variety, and which may have a high heterogeneity.

 The particle size of the waste capable of being treated by such a reactor extends over a very wide range, ranging from dust with a diameter of less than a millimeter to large pieces reaching several tens of centimeters.

 The use of a chain conveyor in combination with very long plates makes it possible to obtain residence times ranging from 15 min to 2 h for a reactor comprising only one intermediate module, and which can rise up to 'at 4 h or more for reactors such as that illustrated in Figure 2 comprising three intermediate modules.

 The linear speed of the waste on the tray, equal to that of the doctor blades, and of the order of a few meters per hour.

 The treatment capacity of a reactor according to the invention is very variable, and can vary from 100 kg per hour to more than 5 tonnes per hour.

 By design, the reactor according to the invention can adapt to any capacity value by simply modifying the dimensional parameters of the plates, that is to say by increasing or decreasing their length by adding intermediate modules. , or else by increasing or decreasing the width of the plate.

It appears from the above that the reactor according to the invention has multiple advantages and in particular the:
-It allows control of the flow of waste as well as the time of
waste stay in the reactor, to obtain complete thermolysis;
-the regularity of the flow and the sizing of the equipment
conveying greatly eliminates the risk of material jamming during
their journey;
-the use of heating means distributed along the path of
waste allows optimal control of heat transfers, and allows
to guarantee complete thermolysis, the flow mode and its profile
allow a significant reduction in dust entrainment;
-the drive blades ensure, thanks to the stirring effect, a
core thermolysis of waste;
- the design of the drive by chain conveyor ensures
adaptability to many types of waste, including products
difficult to thermolyze such as sticky or clogging materials;
-the modular design of the reactor allows adaptation to a large
range of processing capacities;
thermolysis as carried out inside the reactor in accordance with
the invention is particularly complete and optimized;
-the reactor has a simple mechanical design giving it a
robustness and significant reliability.

Industrial applications
The reactor according to the invention is particularly suitable for the treatment by thermolysis of a large number of wastes comprising an organic fraction such as biomass, sludge, in particular from treatment plants, automobile grinding residues, meat-and-bone meal, waste hospitals, electric accumulators as well as industrial by-products such as in particular metal sludge from rolling mills, scrap from the production of plastic films, paper or aluminum, etc.

Claims (8)

 trays (10,11), to heat the waste.  an indirect heating device arranged above and below said  said trays (10,11);  chain conveyor (15) driving a plurality of doctor blades (16), rubbing on  fall by gravity onto the lower plate (11); a device for driving waste on the trays comprising at least one  that when the waste reaches one end (12) of a tray (10), it  plates (10,11) being offset from each other in such a way  CLAIMS 1 / Reactor (1) for thermolysis of waste,: - inlet (3) and outlet (4) orifices for waste; a device for extracting (5-9) the gases produced during thermolysis; characterized in that it further comprises:. at least two fixed trays (10,11) on which the waste travels, the 2 / Reactor according to claim 1, characterized in that the plates (10,11) have a bucket shape, and have their lateral ends (28) raised and inclined. 3 / Reactor according to claim 1, characterized in that the doctor blades (16) of the drive device have a profile complementary to that of the plates (10,11). 4 / Reactor according to claim 1, characterized in that each chain conveyor (15) drives the waste on two adjacent plates (10,11). 5 / Reactor according to claim 1, characterized in that the heating device consists of a set of electrical resistors (30-32). 6 / Reactor according to claim 1, characterized in that the heating device (30-32) is divided into several zones distributed along the path of the waste. 7 / Reactor (1) according to claim 1, characterized in that it consists of the assembly of at least three modules, namely:  an input and output module (50), including the inlet (3) and  waste outlet (4), and comprising one end (19) of at least one of the  chain conveyors;  . at least one intermediate module (52-54) supporting part of the  fixed plates (10, 11);  . a turning module (51), having the opposite end (18)  of said chain conveyor. 8 / Reactor according to claim 7, characterized in that the turning module (51) further comprises drive means due to the chain conveyors.