EP1470204A2

EP1470204A2 - Method and installation for gasifying combustible materials

Info

Publication number: EP1470204A2
Application number: EP03701367A
Authority: EP
Inventors: Virgil Corneliu Stanasila; Octavian Nicolae Stanasila
Original assignee: Nv Claves Consult
Current assignee: Nv Claves Consult
Priority date: 2002-01-29
Filing date: 2003-01-29
Publication date: 2004-10-27
Also published as: WO2003064562A3; AU2003203063A1; WO2003064562A2

Abstract

The invention relates to a method of gasifying raw materials comprising combustible components. The inventive method is characterised in that the heating of the raw materials and endothermic drying, pyrolysis and gasification reactions by vapour take place in at least a first compartment (4), or reactor, of a horizontal rotary cylindrical furnace (1). According to the invention, the thermochemical treatments, which are performed in the reactor, receive solely sensible heat which is conveyed by a solid heat-transfer medium (2) that is cooled in said reactor by between 40 and 70 °C to a temperature which is less than 900 °C and less than the melting temperature of the ash generated. The aforementioned solid heat-transfer medium (2) is itself heated by a part of the gaseous fuel, which is supplied by the reactor, in a second compartment (3) of the horizontal rotary cylindrical furnace, called the heater, said heat-transfer medium (2) being moved continuously between the two compartments (3, 4) during operation. The invention also relates to an installation that is used to carry out said method.

Description

PROCESS AND INSTALLATION FOR GASIFYING MATERIALS

FUELS

Subject of the invention

The present invention relates to a thermally autonomous process for gasifying raw materials cut into small pieces of grain size 5 to 10 mm, mixed in any proportions and containing combustible substances having a humidity of up to 25%, so as to obtain a gaseous fuel of superior quality (for example with a PCI of between 10 and 30 MJ / m ³ ) and free of nitrogen from the atmosphere. The raw materials can be coals of various qualities, sterile carboniferous washing or filter press, hospital and hotel waste, carcasses of used vehicles and tires, plastics, carpet waste, cellulose and paper, slaughterhouse waste, animal meal, plant waste such as bark, leaves, seeds, used oil, etc.

The invention also relates to the installation for the implementation of the method.

Technological background and state of the art Numerous methods and installations for gasifying solid fuels are known in the state of the art. For example, US-A-5,762,010 describes a solution for the pyrolysis and gasification of waste having a calorific value and any humidity. The heat transfer element, both for the drying of waste and for the pyrolysis of dried waste, is a granular mass, separable from said waste and with external recirculation by conveyor and lifting belts. The major drawback is constituted by the thermal shocks to which the granular mass is subjected, when it is brought into contact with the raw materials. During the endothermic process of pyrolysis and gasification, these shocks lead to breakage of the granules into small pieces, which are partially found in the ash, which requires continuous additions of granules which are expensive and damaging to technology. Another drawback lies in the horizontal and vertical transport of the granules among the tooling elements making up the installation, which limits the maximum temperature of the granules and multiplies the number of elevators and moving components of the installation. The SIEMENS process is also known, according to which pyrolysis is carried out at 450 ° C. of dry waste, by consuming a fuel coming from the outside, the heat being transferred by means of a recovery system, that is to say say through heating surfaces separating the different thermal agents

(heated and heated), by imposing very high temperatures (above 900 ° C) for the heating gases. The disadvantage of this process consists in the use of expensive refractory materials and in the subsequent recovery of the sensible heat from the combustion gases by expensive, large-volume installations.

Document US-A-5 311 830 proposes an ideal pyrolysis, but without gasification of the carbon contained in the coke from the pyrolysis of waste, admitting the heat input necessary for the process by means of rigid surfaces which separate the evolving raw materials from the gaseous heating agents. Such heat transfer requires a heavy investment, without solving the reduction in carbon of the coke caused by the pyrolysis.

US-A-4,718,358 proposes the use of microwaves, as a source of maintenance of pyrolysis and gasification of waste, while US-A-4,831,944 proposes the use of plasma as primary heat source. These two methods are prohibitively expensive and therefore devoid of economic interest. In US-A-5,678,496, the waste is loaded onto carriages moving in two parallel tunnels connected in a "U" shape. It is an expensive solution providing only low intensity heat exchange. The patents US-A-5,010,828 and US-A-6,067,916 use pure oxygen, which is economically prohibitive and causes the calorific value of the fuel gas produced to be reduced to a value between 30 and 80% of the PCI of pyrolysis gas and gasification by water vapor, under ideal conditions. The recent patent application US-A1-2001 / 0006 036 relates to the gasification of rubber car tires, introduced whole into a gasification chamber. The fact that large objects are gasified determines a very small specific surface for attacking the reagents (relative to the unit of mass), which generates significant periods of time for the progress of the processes. Aims of the invention

The invention aims to overcome the main drawbacks of the aforementioned state of the art. In particular, the invention aims to avoid the use of granules strongly affected by thermal shock and leading to the formation of ¹ bark. The invention has the additional aim of no longer requiring a displacement of solid coolant by horizontal conveyor belts, or by elevators, and without temperature limitation of the coolant.

The invention has the additional aim of avoiding heat transfer by recovery by means of partition walls.

The invention also aims to use as primary source of energy the raw material itself at the final stage of its development, which would reduce costs by several tens of times compared to the use of micro -waves or plasma.

The invention finally aims to produce a combustion of the residual carbon of the coke resulting from the pyrolysis and the partial gasification by water vapor of the raw materials, avoiding the use of oxygen as in the state of technique.

Main characteristic elements of the invention The process and the installation for the gasification of raw materials having combustible constituents, with the production of pyrolysis gas and water vapor, separately or in the form of a mixture, in accordance with the present invention , on the one hand carry out the heating of these raw materials and on the other hand, the endothermic reactions of drying, pyrolysis and gasification by water vapor in a first compartment of a rotary horizontal cylindrical oven, called "reactor". There are possibly two compartments in the case where it is desired to separate the gases and the water vapor. The aforementioned thermochemical treatments exclusively use sensible heat, given off by a solid heat transfer medium consisting of a mass of cylindrical Rashig refractory rings with a diameter equal to their length (8 to 10 mm) and a wall thickness of 1 to 1, 5 mm, preferably made of steel, resistant up to 900 ° C under a reducing or weakly oxidizing atmosphere. The invention advantageously makes it possible to overcome the negative effects usually caused by thermal shocks on the refractory granules, by ensuring a self-cleaning of the internal cylindrical surface of the furnace and offering a specific surface area for heat exchange which is clearly greater. The mass of metallic Rashig rings, hereinafter called "rings", is cooled from 40 to 70 ° C below 900 ° C and the melting temperature of the ash produced. This mass is heated by a part of the carbon supplied in another compartment of the horizontal rotary cylindrical furnace, called "heater". The reactor and the heater are therefore combined in a single furnace and arranged on a single axis, driven by a motor.

The invention relates to a process for the gasification of raw materials having combustible constituents, with the production of pyrolysis gas and water vapor, separately or in the form of a mixture, said process comprising at least the following steps: provide a horizontal rotary kiln, comprising at least a first compartment, called 'reactor' and at least one second compartment, called a 'heater', said oven being placed in a static carcass, introducing a solid heat carrier which is essentially a plurality of granules or the like of refractory material, into said oven, introducing raw materials into said reactor, to form a mixture of the coolant with the raw materials, continuously moving said coolant between the two compartments, during the rotation of the oven, establishing thermochemical treatments, that is to say heating the raw materials as well as endothermic drying reactions, pyrolysis and gasification by said vapor of the raw materials, said heating and said reactions taking place in said reactor, where said thermochemical treatments receive exclusively sensitive heat, ceded by said coolant, said coolant itself being heated in the heater, by at minus some of the coke supplied by the reactor, as a product of said thermochemical treatments.

According to a preferred embodiment of the invention, said heat transfer solid is cooled in said reactor, by 40 to 70 ° C at a temperature below 900 ° C and below the melting temperature ash generated in the heater.

Preferably, said heat transfer solid consists of a mass of metal Rashig rings, essentially cylindrical. Said rings preferably have a diameter and a length of 8 to 10 mm and a wall thickness of 1 to 1.5 mm, preferably made of refractory steel, and are resistant up to 900 ° C under a reducing or weakly oxidizing atmosphere.

According to a preferred embodiment of the method of the invention, the introduction into the furnace of raw materials is controlled by a lock, which pours with a variable frequency, said materials in a fixed toroidal channel preferably of section rectangular, integral with the static carcass of the furnace and preferably not thermally insulated from the reactor, the raw materials being collected therein by at least one scraper shovel disposed at the end of at least one duct integral with the reactor with an imposed axial curvature by the carcass of the oven, said scraper shovel directing the raw materials inside the duct, where these fall by gravity into the reactor to form a mixture with the coolant, with the help of at least one screw individualized pallets secured with a cable, preferably a flexible steel multi-wire cable, rotated by a gear motor. Preferably, the raw materials are cut into pieces with a particle size of less than 10 mm, preferably between 5 and 10 mm, before being introduced into the oven. According to a preferred embodiment of the method of the invention, the geared motor group has a power of about 100 and is supplied by fixed connections from a 24V reducer-accumulator group, by l 'through two insulated conductors, secured to the furnace and supplied via mobile contactors. According to a preferred embodiment of the method of the invention, to optimize the heat and mass transfer and to direct the circulation of the heat transfer mixture-raw materials in treatment in the two compartments of the oven, heater and reactor, provides two perforated cylinders, ie having orifices, said cylinders being located respectively inside said comparents, of the same horizontal axis as the oven and secured to the oven in its median zone, an axial displacement of the mixture from the inside of said compartments towards the outside taking place on one side of said cylinders, and an axial movement of the mixture from the outside of said compartments towards the inside taking place on the other side of said cylinders, as well as the vertical movement of gaseous products by the cylinder openings.

Preferably, to stir, stir and push the mixture of the coolant with the raw materials axially from the inside to the outside or vice versa, compartments in a space limited on the one hand by the mantle of said compartments and each of said perforated cylinders, pallets of refractory material are provided, secured to the coats of said compartments, arranged at equal distances or in groups and with inclinations such that said pallets advance said mixture axially from the inside of said compartments towards the outside of said compartments , during the rotation of the oven in a first direction of rotation.

Preferably, to stir, agitate and push the mixture of rings and raw materials axially from the outside towards the inside of the compartments in a space limited on the one hand by each of said perforated cylinders and on the other hand by the axis of the furnace, pallets of refractory materials are provided, secured to said perforated cylinders, arranged at equal distances or in groups and with inclinations such that said pallets advance said mixture axially from the outside of said compartments to the inside of said compartments, when the oven is rotated in a first direction of rotation. According to the preferred embodiment of the method of the invention, the two compartments, reactor and heater are joined in a single unit oven, arranged along the same axis, driven by a single motor, while a continuous circulation , without horizontal conveyors or mechanical elevators, is carried out between the reactor and the driver in such a way that the granules of the coolant never leave the entire unit oven. According to a preferred embodiment of the method of the invention, as soon as the raw material is brought into contact in the reactor with said coolant, preferably at a temperature of about 850 ° C, the coolant / material mixture raw materials is moved along the reactor, into the reactor, pushed by the pallets into the space between the reactor mantle and the perforated cylinder located in the reactor, near the outer axial end of the reactor, where the heat-transfer mixture of already dried and partially pyrolyzed raw materials changes direction to move in the opposite direction, then pushed by the pallets into the space between said perforated cylinder of the reactor and the axis of the furnace, to the end axial interior of the reactor, the raw material then being coked therein, completely pyrolyzed and the heat-carrying coke-residual unit, brought to around 800 ° C., being d poured out by a window, when this is below the level of the bulk, falling by gravity into a chamber, extended by a channel, preferably extending in an arc of about 225 °, in which a plug is formed of said ring-coke mixture poured under the bulk of the coolant into the heater; the coke burns in the heater, during its movement, pushed by the pallets in a space between the mantle of the heater and the perforated cylinder of the heater, up to the outer axial end of the heater, where it changes direction to move in the opposite direction, then pushed by the pallets in the space between the perforated cylinder of the heater and the axis of the oven, to the inner axial end of the compartment; - the carbon in the coke is burned completely, the coolant and the ashes resulting from this combustion arrive at the middle wall between the heater and the reactor, where, after having exceeded a threshold, the ashes are mainly removed by a grate, the granules of the relatively clean coolants are discharged through a window and fall into a chamber and then into a toroidal channel preferably extending in an arc of about 225 °, to be finally led under the bulk of the reactor, thus completing the functional cycle of the rings and raw materials.

According to a preferred embodiment of the method of the invention, the single circulation path defined by the cycles of the coolant and the raw materials under treatment is replaced by a plurality of circulation paths, preferably 3 or 4, evenly offset.

Preferably, the gases resulting from the pyrolysis of the raw materials and the gasification by water vapor of at least part of the carbon of the coke are collected by a pipe provided with perforations, after these gases have been generated. mostly under the bulk, i.e. the heat transfer mixture / raw materials and have necessarily crossed this bulk, before being directed to a gas treatment installation.

Preferably, in order to obtain more intense stirring of the mixture, a reduction in the angle of the slope naturally formed by the bulk, that is to say the heat transfer mixture / raw materials of the oven compartments and cleaning the layer of ash deposited on the walls, solid cylindrical bodies of the same shape as these rings and / or tetrahedra and prisms are introduced into the mass of rings, up to 10% by mass shape of parts used in deburring.

To produce the steam necessary to generate the degassing and reduction of the carbon of the coke resulting from the pyrolysis of the raw materials, as well as the steam necessary to carry out the steam cracking in the reactor, the raw materials are preferably admitted to a humidity up to 25%, said vapor being generated at the base of the heat transfer mixture / raw materials and brought to pass through the entire mixture, at the same time as the gases which move through the mass of coke whose carbon must be reduced.

Preferably in the process of the invention: to ensure the combustion, inside the bulk of the heater, of the combustion air preheated to about 800 ° C in a preheater / exchanger is introduced by a fixed duct provided thermal insulation and a window which provides access only to a fraction, preferably 9 out of 36, of a plurality of radial channels, limited by radial plates, access to the other channels being blocked by a bottom; along the radial channels are holes, preferably 0 5 mm, cleaned by the continuous stream of combustion air; the combustion air, in contact with the coke, causes the combustion of carbonaceous residues, generating the heat necessary to heat the coolant to a temperature rising from 800 to 850 ° C approximately; the gases of complete combustion are evacuated by a grid; - the combustion gases are returned to the exchanger, where they are cooled from approximately 880 to 180 ° C, while heating the combustion air from approximately 10 to 800 ° C.

The invention is also related to an installation for implementing the method according to any one of the preceding claims, characterized in that it comprises:

A rotary kiln having an axis of rotation which is essentially horizontal, said kiln being arranged in a static carcass and said kiln comprising at least two compartments, called respectively heater and reactor, for receiving a mixture of a coolant, i.e. -to say a plurality of refractory granules, with primary materials .; Means for introducing raw materials and / or granules of said coolant into the oven,

Means for circulating, during the rotation of the oven, said coolant between said compartments. Means for introducing combustion air into the heater. In the installation according to the invention, said means for introducing raw materials and / or granules of the coolant preferably comprise: - a fixed toroidal channel preferably of rectangular cross section, integral with said static carcass of the furnace and not thermally insulated from the reactor, for receiving the raw materials in the furnace, - inside said fixed toroidal channel, at least one conduit integral with the reactor with an axial curvature imposed by the carcass of the furnace, and a scraper shovel disposed at the end of said duct, for collecting raw materials and introducing them into said duct, - inside said duct, an individualized vane screw and secured with a cable, preferably flexible steel,

- a geared motor group, to put said cable in rotation. The gear motor group can have a power of about 100W and be powered by fixed connections from a 24V reducer-accumulator group, via two insulated conductors, secured to the furnace and supplied via mobile contactors. According to a preferred embodiment of the installation of the invention, said installation comprises two perforated cylinders, ie having orifices, said two cylinders being located respectively inside said two compartments, with the same horizontal axis as the oven and secured to the oven, ensuring an axial displacement of the mixture formed by the coolant and the primary materials, first outwards and then inwards of said compartments, as well as the vertical displacement of the gaseous products through the orifices of the cylinders.

According to a preferred embodiment of the installation of the invention, said installation comprises pallets of refractory material, secured to the compartments coats, arranged at equal distances or in groups and with inclinations such that said pallets advance said mixture axially from the inside of said compartments towards the outside of said compartments, during the rotation of the oven in a first direction of rotation. .

According to a preferred embodiment of the installation of the invention, said installation comprises pallets of refractory material, secured to said perforated cylinders, arranged at equal distances or in groups and with inclinations such that said pallets advance said mixing axially from the outside of said compartments towards the inside of said compartments, during rotation of the oven in said first direction of rotation.

According to a preferred embodiment of the installation of the invention, the means for circulating said coolant from one compartment to another, comprise: - a wall between the two compartments, heater and reactor, said wall comprising a first window, and a second window, a first chamber, extended by a first channel, said first window giving access to said first chamber and to said first channel, said first channel giving access to the heater, a second chamber, extended by a second channel, said second window giving access to said second chamber and to said second channel, said second channel giving access to the reactor.

Preferably, the installation of the invention comprises a central pipe, provided with perforations, for evacuating gases from the reactor According to a preferred embodiment of the installation of the invention, said means for introducing combustion air comprise: a fixed duct, preferably provided with thermal insulation, leading the combustion air towards the inside the heater, a plurality of radial plates integral with the rotary kiln, forming a plurality of radial channels, which extend between the mantle of the oven and the mantle of the heater, said mantle of the heater being provided with orifices for admitting the combustion air inside said heater, between the fixed duct and the radial channels, a fixed bottom blocking access to part of the radial channels, and provided with a window, giving access to the other part of said radial channels, a grid to evacuate the ashes produced in the heater as well as the combustion gases. According to a preferred embodiment of the installation of the invention, said installation comprises

a hearth for burning external fuel, a heat exchanger provided with fans, a connection between one heat exchanger and the heater, for introducing oxidizing gases into the heater. According to a preferred embodiment of the installation of the invention, the rotary kiln is arranged on at least two bearings, a first bearing being on the heater side and a second being on the reactor side, and the fixed duct is provided with at least one shoulder, on which a plurality of helical springs bear, said springs being clamped on rods, linked to the fixed part of the bearing, to minimize the free spaces between the fixed combustion air supply duct and the oven.

Below, a preferred example of implementation of the invention will be given, in correlation with FIGS. 1 to 5. Brief description of the figures

Figure 1 shows an axial vertical sectional view of the installation of pyrolysis oven. Figure 2 shows a cross-sectional view of the two-way reactor.

Figure 3 shows a block diagram of the oven installation.

Figure 4 shows the unfolding in plan of the two-way assembly of fig. 2.

Figure 5 illustrates the evolution with the movement of the communication channels between the reactor and the heater, in a four-way assembly.

Detailed description of a preferred embodiment of the invention

A rotary oven 1, metallic, refractory, cylindrical and horizontal, has two compartments filled to 40% with Rashig rings 2, 0 8x1.25, length ≈ 8 mm, made of refractory steel and the temperature of which is between operating regime between 800 and 850 ° C. These rings are for example heated in a compartment 3, called "heating" or "heater". Said rings transfer the sensible heat which they have received into a second compartment 4, called "reactor". The two compartments are arranged one beside the other along the axis of rotation of the oven. The raw material, consisting of pieces of grain size 5 to 10 mm, is introduced by a curvilinear duct 5, integral with the oven, with a curvature imposed by the oven, where said raw material falls by gravity, with a flow rate controlled by a lock, first in a fixed toroidal space 6, of rectangular section, linked to the static external carcass 7 of the furnace.

The raw material is collected by a scraper 8 rigidly connected to the inlet head of the conduit 5, in which the load continues its gravitational fall during the rotation of the furnace (typically at 4-6 rotations per minute ), and pushed simultaneously by a screw 9 made up of individual pallets, joined together using a multi-wire cable 10 made of flexible steel, rotated by a geared motor 11 of approximately 100 W of power. The geared motor is supplied via fixed connections by a 24 V rectifier-accumulator group, and by means of two insulated conductors 12 secured to the oven, supplied by two contactors. The downstream end of the conduit 5 allows the introduction of the raw material into the compartment 4, by contacting the Rashig rings at 850 ° C, driven by the rotation of a continuous stirring movement. The mixture of raw material and rings moves along the internal wall of compartment 4, pushed by pallets 13 into the space between the jacket 100 of the reactor 4 and a perforated cylinder 14. The jacket 100 of the reactor 4 is identical to the mantle of the oven 1. The pallets 13 have an inclination such that these pallets push the mixture towards the outside of the reactor, during the rotation of the oven in a first direction of rotation. In the vicinity of the end of compartment 4, the mixture of rings and already dried, degassed and partially pyrolyzed raw materials changes direction and moves in the opposite direction to that mentioned above, being again pushed by a set of pallets 15. Up to the other end of compartment 4, the raw material is coked, completely pyrolyzed and the carbon of the coke thus product partially gasified by steam resulting from drying. The pallets 15 have an inclination such that they advance the mixture axially from the outside of the reactor 4 towards the inside during the rotation of the furnace in said first direction of rotation.

The set of rings and residual coke, at about 800 ° C, is then poured out through a window 16, when the latter is below the level of the bulk and falls into a chamber 17, extended by a channel 18, extending over an arc of approximately 225 °, in which a plug of ring and coke mixture is formed which is poured under the bulk 2 of rings from compartment 3. Thanks to the combustion air brought to 800 ° C, which enters through the orifices 19 of a set of channels 20 at the periphery of the compartment 3, the coke burns during its movement with its respective rings in a space 21, limited by the metal periphery of the heater compartment 3 , that is to say the mantle 101 of the heater 3, and a perforated cylinder 22. The coke is pushed there by a set of pallets 23 to the end of the compartment 3 where it changes direction of movement. At this time, the coke is pushed by another set of pallets 24. The carbon of the coke is then completely burned and the rings as well as the resulting ash arrive at the level of the essentially vertical middle wall 25, separating the compartments 3 and 4 , after crossing a threshold 26.

Then, the ashes descend for the most part and are evacuated by a grid 27, falling between the agitated rings above the grid 27 by the oven rotation. The rings, then relatively clean, are poured out through a window 28 and fall by gravity into a chamber 29 and then into a toroidal channel 30 which extends over an arc of 225 °. The rings are finally brought under the bulk of compartment 4, and thus complete their functional cycle.

To simplify the representation of the oven, the circulation of Rashig rings between the compartments has been presented for a single circulation lane in FIG. 1. Industrial ovens can however advantageously have 3 or 4 lanes of this type, offset, to standardize the distribution of the raw material within the mass of rings and coke, respectively in compartments 4 and 3. If there is only one supply mouth, the introduction of the raw material is done on a quarter of a complete rotation of the oven, and during the rest, there is no raw material introduced, which generates non-uniformity of evolution of the material. With two channels, feeding takes place over the duration of two quarter-turns, reducing the effect of non-uniformities. With four routes, food and material development are even more uniform. Figure 2 shows the two-way embodiment. The colors gray (or circles 'o') and white (cross 'x') indicate the path of the rings for the two chambers (gray and white) of the compartment on one side of the central wall 25. There are two chambers at the posterior part of the central wall. The rings entered into one of the 'view' chambers run more than a quarter of the oven's periphery in a channel adjacent to the central wall, then the channel being distant from the wall on another quarter of the circle, to make room for the channel from the other room, up to the exit of the rings and before meet the fresh raw materials entered into the oven. By the gray and white use in the drawing, we indicate the unity between the gray room and the gray channel and similarly, the unity of the white room and the white channel. For example, we see the unit between the chamber 29 and the conduits through which the rings collected in the chamber are moved. These conduits occupy two places: near the central wall of the oven or farther. In the embodiment of FIG. 2, there are two conduits 5, provided with two scraper shovels 8, and two screws 9. FIG. 4 shows the unfolding in plan of the two-way installation.

Figure 5 schematically illustrates the development in plan of a four-way assembly. It can be seen that the mixture of refractory rings and raw materials under treatment is taken only in the upper part of the bulk and it is introduced at the base or lower part of the bulk of the neighboring compartment, to optimize the processes. When contacting raw materials at 20-30 ° C and refractory rings at 850 ° C, they are vigorously dried and preheated, always brutally; the same is true of devolatilization and partial gasification. During this period, it is possible to obtain bonding of the evolving raw material, but the rapid heating, above 700 ° C. and the continuous agitation of the assembly ensure the cleaning of the rings. Likewise, before being poured out through the window 28, the ashes, the melting temperature of which is above 900 ° C., are slightly separated from the agitated rings.

To obtain more intensive stirring of the mixture, to reduce the slope of the spontaneous bulk slope in compartments 3 and 4 and to clean the ashes deposited on the walls, are introduced into the mass of rings, up to a maximum of 10% by mass, solid cylinders and / or tetrahedrons of the same shape as the parts used for deburring. Gases are obtained mainly by pyrolysis, but also by gasification by water vapor of part of the carbon of the coke. They are generated almost entirely under the bulk and are forced to pass through it, thereby heating up above 750 ° C, until they are collected by a pipe 31 having perforations, which leads them to a fixed pipe 32, to solid walls, with thermal insulation 33, from which they are directed to a gas treatment installation, known per se. The tars which are generated during pyrolysis are heated as long as the bulk which retains them is traversed by these gases, creating conditions for their vapocracking and therefore the reduction of the tar content.

The combustion air consumed in compartment 3 is brought by a fan 34 (fig. 3), which takes it from the atmosphere and sends it to a preheater 35 and from there to the rotary oven 1 at a temperature of 800 ° C, at the level of compartment 3, by a fixed duct 36 provided with thermal insulation 37 and an opening 38. This ensures the access of air only in one part, preferably 9 of 36 channels radial 20 limited by radial plates 39. Access to the other 27 channels is blocked by a bottom 40. The window 38 is made in this bottom 40 which is welded with the pipe 36. The existence of a small clearance between the bottom 40 and the edges 41 of the plates 39 ensures an almost perfect seal, which allows air to enter only 9 of the 20 channels mentioned above. Orifices 19 of 0 5mm are made along the channels 20, that is to say in the outer jacket 101 of the heater compartment 3. Said orifices are cleaned by the air current which passes through it periodically. The hot air, in contact with the coke, causes the combustion of the carbon residue generating heat, yielded above all to the refractory rings which are heated to 800-850 ° C, but also to the complete combustion gases which are formed and evacuated by the grid 27, especially in the areas free of rings. Via a connecting duct 42 (FIG. 3), the complete combustion gases are led to the exchanger 35 where they are cooled from ± 880 ° C to around 180 ° C, the temperature at which they are drawn in by a exhaust 43, while heating the combustion air from 10 to 800 ° C. The oven is supported on two bearings 44, by means of an axis 45, inside which is the conduit 36 for supplying the combustion air at 800 ° C. Still along this axis, from compartment 4, the conduit 32 for discharging the generated gaseous fuel leaves. For the protection of the bearings, there are provided two zones 46 for cooling the axis with water distributed by plates 47, and collected by a system 48. There is provision for one axial sealing of the conduit 36 of the parts 49 integral with the conduit and resiliently pushed back by helical springs 50, compressed by rods 51 connected to the bearing frame 44 on the side of the compartment 3.

The rotary oven is driven by an electric gear motor, which acts on the axis 45 on the side of the reactor 4, by means of a flywheel 52.

The commissioning of the installation begins with the loading of the Rashig rings by means of a system 53 for supplying raw materials

(figure 2). After 40% of compartment 4 has been filled with these rings, the excess rings are poured into the compartment 3, where it is accumulated until a similar filling rate of 40% of the compartment is obtained

3. When the two compartments are filled in the same way, the rings can move from one compartment to another. Then, a fireplace 54 is put into operation where an external gaseous fuel is burned, consumed only at (re) start of the installation (FIG. 3). Thanks to the fans 34 and 43 running at a reduced speed, the gases sucked in by the fan 43 are gradually heated by the gases from the hearth 54, which also gradually heat the air passing through the exchanger 35 and which enters the compartment 3 of the oven. The heating process continues up to the temperature of 750-800 ° C in the two compartments 3 and. At this time, the hearth 54 is turned off, the consumption of external gaseous fuel is completely stopped and the oven is prepared to be supplied with the raw materials and to operate in regime. To increase the energy efficiency of the furnace, the combustible gases generated will be cooled from 700 to 100 ° C and the combustion gases from 180 ° C to 100 ° C, by preheating the raw material.

The main advantages of the pyrolysis oven according to the invention are as follows: the process can be adapted for the energy recovery of various secondary raw materials produced in the industry such as sawdust, lower carbon, sterile carboniferous filter -press, etc., as well as various waste presenting combustible constituents; - The method relates to phenomena with high energy release and the complete separation of the combustible gases produced from those of combustion, with the absence of volatile ash; the installations according to the invention are highly ecological, reducing C0 emissions by 30% compared to those of existing similar installations, while producing as ash only minimal quantities of ash, concentrated and not dispersed by gases; the installations which apply the method of the invention are reliable, completely automated and compact, occupying small areas (for example, the surface of a plot for an installation which processes 10 tonnes / hour of raw materials is estimated at approximately 150 m ² , not including any storage); the gasification installations according to the invention can be placed in isolated places, using a small electric group, little water and fuel only for start-ups, while on the other hand ensuring good quality gaseous fuel, from raw materials obtained locally; said installations have a low consumption of electrical power, for example below 150 kW for an installation which processes 10 tonnes / hour of raw materials, with practically zero consumption of external fuel, and with a limited operating workforce (maximum 2 workers in successive teams); the efficiency of the installation according to the invention exceeds 86%; the return on investment of an installation according to the invention can be achieved in 5 months maximum. The invention greatly attenuates the mentioned disadvantages of the state of the art: the granules are replaced by refractory metal rings, preferably of the Rashig type, practically unaffected by thermal shock, with clearly superior scraping properties, while preventing the formation of bark; the displacement of the solid coolant no longer requires neither horizontal conveyor belts, nor elevators and no temperature limitations, the displacement being carried out by the rotary kiln itself, with optimized sampling and dumping, in a continuous back-and-forth flow, - the heat transfer is not done by recovery by means of partition walls, but by means of a mass of refractory rings alternately heated and then used as sensible heat source by direct contact with the raw materials in treatment, which intensifies the heat transfer by several hundred times compared to the other known solutions; the primary source of energy is the raw material itself in its state at the end of its treatment, which reduces the costs by several tens of times compared to the use of microwaves or plasma; the combustion of the residual carbon of the coke, resulting from the pyrolysis and the partial gasification with steam of the raw materials, is carried out with air strongly preheated by the exhausted combustion gases, without any contact with the fuel gaseous generated, preserved after a thermochemical treatment and avoiding the use of oxygen.

Claims

1. Process for the gasification of raw materials having combustible constituents, with the production of pyrolysis gas and water vapor, separately or in the form of a mixture, said process comprising at least the following steps: providing a horizontal rotary kiln (1) , comprising at least a first compartment, called the “reactor” (4) and at least a second compartment, called the “heater” (3), the said oven being placed in a static carcass (7), introduce a solid coolant (2) which is essentially a plurality of granules or the like of refractory material, in said furnace, - introducing raw materials into said reactor (4), to form a mixture of the coolant with the raw materials, continuously moving said coolant between the two compartments (3,4), during the rotation of the furnace, - carry out thermochemical treatments, that is to say a heating of the raw materials as well as endot reactions hermetic drying, pyrolysis and gasification by said vapor of the raw materials, said heating and said reactions taking place in said reactor 4), where said thermochemical treatments receive exclusively sensitive heat, ceded by said coolant (2), said coolant (2 ) being itself heated in the heater (3), by at least part of the coke supplied by the reactor (4), as a product of said thermochemical treatments.

2. Method according to claim 1, characterized in that said heat-transfer solid (2) is cooled in said reactor (4), by 40 to 70 ° C at a temperature below 900 ° C and below the melting temperature of the ash generated in the heater (3).

3. Method according to claim 1 or 2, characterized in that said heat transfer solid (2) consists of a mass of metallic Rashig rings, essentially cylindrical.

4. The method of claim 3, wherein said rings have a diameter and a length of 8 to 10 mm and a wall thickness of 1 to 1.5 mm, preferably of refractory steel, and are resistant up to 900 ° C under a reducing or weakly oxidizing atmosphere.

5. Method according to claim 1, 2 or 3, characterized in that the introduction into the furnace of the raw materials is controlled by a lock, which pours with a variable frequency, said materials into a fixed toroidal channel (6) preferably of rectangular section, integral with the static carcass of the furnace and preferably not thermally insulated from the reactor (4), the raw materials being collected therein by at least one scraper scraper (8) disposed at the end of at least one duct (5) integral with the reactor with an axial curvature imposed by the carcass of the furnace, said scraper scraper (8) directing the raw materials inside the duct

(5), where these fall by gravity into the reactor (4) to form a mixture with the coolant (2), with the help of at least one screw (9) with individualized pallets and secured using a cable (10), preferably a multi-wire flexible steel cable, rotated by a gear motor (11).

6. The method of claim 5, wherein the raw materials are cut into pieces of particle size less than 10 mm, preferably between 5 and 10 mm, before being introduced into the oven.

7. Method according to claim 5, characterized in that the geared motor group (11) has a power of about 100 W and is supplied by fixed connections from a 24 V reducer-accumulator group, by l 'Intermediate of two insulated conductors (12), secured to the oven and supplied via mobile contactors.

8. Method according to any one of claims 1 to 7, characterized in that, to optimize the heat and mass transfer and to direct the circulation of the heat-transfer mixture-raw materials in treatment in the two compartments (3,4) of the oven , heater and reactor, two perforated cylinders (22,14) are provided, ie having orifices, said cylinders being located respectively inside said compartments (3,4), with the same horizontal axis as the oven and secured to the oven ( 1) in its central zone, an axial displacement of the mixture from the interior of said compartments (3,4) towards the exterior taking place on one side of said cylinders (22,14), and an axial displacement of the mixture of the outside of said compartments (3,4) towards the inside taking place on the other side of said cylinders (22,14), as well as the vertical movement of gaseous products through the orifices of the cylinders (22,14).

9. Method according to claim 8, characterized in that to stir, stir and push the mixture of the coolant with the raw materials axially from the inside to the outside or vice versa, compartments (3,4) in a limited space firstly by the mantle of said compartments (3,4) and each of said perforated cylinders (22,14), pallets (23,13) of refractory materials are provided, secured to the mantles said compartments (3,4), arranged at equal distances or in groups and with inclinations such that said pallets (23,13) advance said mixture axially from the inside of said compartments (3,4) towards the outside of said compartments , during the rotation of the oven in a first direction of rotation.

10. Method according to claim 7, characterized in that to stir, agitate and push the mixture of rings and raw materials axially from the outside towards the inside of the compartments (3,4) in a limited space on the one hand by each of said perforated cylinders (22,14) and on the other hand by the axis of the oven (1), pallets (24,15) of refractory materials are provided, secured to said perforated cylinders (22,14), arranged at equal distances or in groups and with inclinations such that said pallets (24,15) advance said mixture axially from the outside of said compartments

(3,4) towards the inside of said compartments, during rotation of the oven in a first direction of rotation.

11. Method according to any one of claims 6 to 8, characterized in that the two compartments, reactor (4) and heater (3) are joined in a single unit oven (1), arranged along the same axis, driven by a single engine, while a continuous circulation, without horizontal conveyors or mechanical elevators, is carried out between reactor and driver so that the granules of the coolant (2) never leave the entire unit oven.

12. Method according to any one of the preceding claims, characterized in that: as soon as the raw material is brought into contact in the reactor (4) with said coolant, preferably at a temperature of about 850 ° C, the mixture coolant / raw material is moved along the reactor, in the reactor (4), pushed by the vanes (13) into the space between the reactor jacket (4) and the perforated cylinder (14) located in the reactor, near the end axial outside of the reactor (4), where the heat transfer mixture - already dried and partially pyrolized raw materials changes direction to move in the opposite direction, then pushed by the pallets (15) into the space between said perforated cylinder (14) from the reactor and the axis of the furnace, up to the internal axial end of the reactor (4), the raw material then being coked there, completely pyrolyzed and the heat-coke residual assembly, brought to around 800 ° C., being poured out through a window (16), when this is below the level of the bulk, falling by gravity into a chamber (17), extended by a channel (18), preferably extending along an arc of about 225 °, in which a plug of said melan is formed ge coke rings poured under the bulk of the coolant (2) into the heater (3); the coke burns in the heater (3), during its movement, pushed by the pallets (23) into a space (21) between the mantle (101) of the heater (3) and the perforated cylinder (22) of the heater, to the outer axial end of the heater (3), where it changes direction to move in the opposite direction, then pushed by the pallets (24) into the space between the perforated cylinder (22) of the heater (3 ) and the axis of the oven, up to the internal axial end of the compartment (3); the carbon in the coke is burned completely, the coolant (2) and the ashes resulting from this combustion arrive at the middle wall (25) between the heater and the reactor, where, after having exceeded a threshold (26), the ashes are mainly evacuated by a grate (27), the relatively clean coolant granules are poured out through a window (28) and fall into a chamber (29) and then in a toroidal channel (30) preferably extending in an arc of about 225 °, to be finally led under the bulk (2) of the reactor (4), thereby completing the functional cycle of the rings and raw materials .

13. Method according to claim 12, characterized in that the single circulation path defined by the cycles of the coolant and the raw materials being treated is replaced by a plurality of circulation paths, preferably 3 or 4, offset uniformly.

14. Method according to any one of the preceding claims, characterized in that the gases resulting from the pyrolysis of the raw materials and the gasification by water vapor of at least part of the carbon of the coke are collected by a pipe ( 31) provided with perforations, after these gases have been generated mainly under the bulk, that is to say the heat transfer mixture / raw materials and have necessarily passed through this bulk, before being directed to a gas treatment installation .

15. Method according to any one of the preceding claims, characterized in that, in order to obtain a more intense stirring of the mixture, a reduction in the angle of the slope naturally formed by the bulk, that is to say the heat transfer mixture / raw materials from the oven compartments (3,4) and a cleaning of the layer of ash deposited on the walls, bodies are introduced into the mass of rings (2), up to 10% by mass full cylindrical, of the same shape as these rings and / or tetrahedrons and prisms in the shape of the parts used in deburring.

16. Method according to any one of the preceding claims, characterized in that, to produce the steam necessary to generate the degassing and reduction of the carbon of the coke resulting from the pyrolysis of the raw materials, as well as the steam necessary to perform the steam cracking in the reactor, the raw materials are admitted at a humidity of up to 25%, said steam being generated at the base of the heat transfer mixture / raw materials and brought to pass through the entire mixture, at the same time as the gases which move through the mass of coke whose carbon is to be reduced.

17. Method according to any one of the preceding claims, characterized in that: to ensure the combustion, inside the bulk of the heater (3), of the combustion air preheated to about 800 ° C in a preheater / exchanger (35) is introduced by a fixed duct (36) provided with thermal insulation (37) and a window (38) which provides access only to a fraction, preferably 9 out of 36, of a plurality of radial channels (20), limited by radial plates (39), access to the other channels being blocked by a bottom (40); along the radial channels (20) there are orifices (19), preferably 0.5 mm, cleaned by the continuous stream of combustion air; the combustion air, in contact with the coke, causes the combustion of carbonaceous residues, generating the heat necessary to heat the coolant (2) to a temperature rising from 800 to 850 ° C approximately; the gases of the complete combustion are evacuated by a grid (27); the combustion gases are returned to the exchanger (35), where they are cooled from approximately 880 to 180 ° C, while heating the combustion air from approximately 10 to 800 ° C.

18. Installation for implementing the method according to any one of the preceding claims, characterized in that it comprises:

A rotary kiln (1) having an axis of rotation which is essentially horizontal, said kiln being arranged in a static carcass (7) and said kiln (1) comprising at least two compartments (3,4), called respectively heater and reactor, to receive a mixture of a heat carrier (2), that is to say a plurality of refractory granules, with primary materials .;

Means for introducing raw materials and / or granules of said coolant (2) into the oven (1), Means for circulating, during the rotation of the oven (1), said coolant between said compartments (3,4) .

Means for introducing combustion air into the heater (3).

19. Installation according to claim 18, in which said means for introducing raw materials and / or granules of the coolant comprise:

- a fixed toroidal channel (6) preferably of rectangular section, integral with said static carcass (7) of the furnace (1) and not thermally insulated from the reactor (4), for receiving the raw materials in the furnace, - at the inside said fixed toroidal channel (6), at least one duct (5) integral with the reactor (4) with an axial curvature imposed by the carcass of the furnace, and a scraper scraper (8) disposed at the end of said duct (5 ) to collect raw materials and introduce them into said conduit (5),

- inside said conduit (5), a screw (9) with individualized pallets and secured using a cable (10), preferably made of flexible steel,

- a geared motor group (11), for putting said cable in rotation.

20. Installation according to claim 19, characterized in that the geared motor group (11) has a power of approximately 100 W and is supplied by fixed connections from a 24 V reducer-accumulator group, by l 'Intermediate of two insulated conductors (12), secured to the oven and supplied via mobile contactors.

21. Installation according to any one of claims 18 to 20, comprising two perforated cylinders (22,14), ie having orifices, said two cylinders being located respectively inside said two compartments (3,4), likewise horizontal axis as the oven and secured to the oven (1), ensuring an axial displacement of the mixture formed by the coolant and the primary materials, first outwards and then inwards of said compartments (3,4), thus that the vertical displacement of the gaseous products through the orifices of the cylinders (22,14).

22. Installation according to claim 21, comprising pallets (23,13) of refractory material, secured to the mantle (100, 101) of the compartments (3,4), arranged at equal distances or in groups and with inclinations such as said pallets (23,13) advance said mixture axially from the inside of said compartments (3,4) towards the outside of said compartments, during rotation of the oven in a first direction of rotation.

23. Installation according to claim 21, comprising pallets (24,15) of refractory material, secured to said perforated cylinders (22,14), arranged at equal distances or in groups and with inclinations such as said pallets (24,15) advancing said mixture axially from the outside of said compartments (3,4) towards the inside of said compartments, during rotation of the oven in said first direction of rotation.

24. Installation according to any one of claims 18 to 23, in which the means for circulating said coolant (2) from one compartment to the other, comprise: a wall (25) between the two compartments, heater (3 ) and reactor (4), said wall comprising a first window (16), and a second window (28), a first chamber (17), extended by a first channel (18), said first window (16) giving access to said first chamber (17) and said first channel (18), said first channel (18) giving access to the heater (3), a second chamber (29), extended by a second channel (30), said second window (28) giving access to said second chamber (29) and to said second channel (30), said second channel (30) giving access to the reactor (4)

25. Installation according to any one of claims 18 to 24, comprising a central pipe (31), provided with perforations, for evacuating gases from the reactor (4).

26. Installation according to any one of claims 18 to 25, in which said means for introducing combustion air comprise: a fixed duct (36), preferably provided with thermal insulation (37), leading the combustion air towards the interior of the heater (3), a plurality of radial plates (39) integral with the rotary kiln (1), forming a plurality of radial channels (20), which extend between the mantle (100) of the oven and the mantle (101) of the heater (3), said mantle (101) of the heater (3) being provided with orifices ( 19) to admit the combustion air inside said heater (3), between the fixed duct (36) and the radial channels (20), a fixed bottom (40) blocking access to part of the radial channels ( 20), and provided with a window (38), giving access to the other part of said radial channels (20), a grid (27) for discharging the ash produced in the heater (3) as well as the combustion gases.

27. Installation according to any one of claims 18 to 26, comprising: - a hearth (54) for burning an external fuel, a heat exchanger (35) provided with fans (34,43), a connection (36) between the heat exchanger (35) and the heater (3), for introducing oxidizing gases into the heater (3).

28. Installation according to claim 26, in which the rotary kiln is arranged on at least two bearings (44), a first bearing being on the heater side and a second being on the reactor side, and in which the fixed duct (36) is provided at least one shoulder (49), on which a plurality of helical springs (50) are supported, said springs being clamped on rods (51), linked to the fixed part of the bearing (44), to minimize the free spaces between the fixed duct (36) for supplying combustion air and the furnace (1).