FR2778734A1 - Rotary furnace for domestic waste - Google Patents

Abstract

The rotary furnace has a filling hopper (17) with a fixed tube (18) having a horizontal axis coinciding with the treatment chamber (4). The tube contains a piston (20) which feeds a plug of waste material (38) towards the chamber.

Description

The present invention relates to a rotary type oven, in which

  conditions of temperature and pressure are maintained allowing the destruction of household and industrial waste, in particular household refuse and plastic waste, and more generally of organic products, by the process known under the name of "thermolysis". To carry out such a treatment, this rotary kiln operates, in particular, at a temperature of the order of 450 C, and under vacuum, under an absolute pressure of about 20 millibars, and it

  thus requires a seal vis-à-vis the outside.

  In a generally known manner, such a rotary kiln comprises - the rotary kiln proper, with its treatment tank of generally cylindrical shape and with a horizontal axis, rotatably mounted around its horizontal axis on support rollers, motorized means being provided for the rotary drive of this rotating part, about its horizontal axis; - At the top of the oven, a filling system having the function of introducing the products to be treated into the aforementioned tank, this system having to include sealing means, preventing the entry of outside air into the tank, during the treatment and when admitting into it products to be treated; - On leaving the oven, a system for extracting the treated solid products, as well as steam and / or gases from the treatment, also with air tightness means; - means for compensating for the longitudinal and / or radial expansion of the treatment tank; means for heating the treatment enclosure, delimited by the walls of the tank, this enclosure being

maintained in depression.

  To date, the filling systems of rotary ovens of this kind, whether of the continuous or discontinuous type, still pose serious problems of tightness, in particular for ovens with continuous feed, and problems of cycle time and time. energy for

  batch feed. However, it is important to ensure that

  presence of oxygen inside the rotary kiln; in fact, from this absence of oxygen, therefore from a good seal, depends the quality of the thermolysis phenomenon taking place inside the furnace, whether in

  continuous feed or discontinuous feed systems.

  In particular, in the case of a rotary furnace allowing continuous operation, to which case the present invention relates, the supply of the furnace with product to be treated is confronted with the sealing problems mentioned above, which then arise from as follows: since the feed is supplied via a loading hopper, the base of which is extended by a fixed feed tube, it is necessary to seal against the rotating part of the oven , in particular with respect to an inlet tube or sleeve, integral with the rear front wall of the treatment tank and rotating with the latter (the word "rear" designating, here and throughout the following, the side of the oven inlet, and therefore the word "before" will designate the side of the oven outlet). In this place, the seal is produced by means of a rotating annular seal, consisting of a fixed part mounted on the aforementioned fixed supply tube, and a movable part fixed on the tube or sleeve. entry of the tank. It can be a classic rotating joint,

  or a special gasket with a neutral gas "sweep" such as nitrogen.

  The installation of such sealing means remains very delicate, as well as their maintenance, in particular for joints with "sweeping" with neutral gas. In addition, the effectiveness of these seals is made very

  random by vertical and longitudinal dilations.

  The present invention aims, essentially, to improve the seal on the inlet side of the products to be treated in the rotary kiln,

  while reducing maintenance operations.

  To this end, the invention relates to a rotary furnace for the treatment by thermolysis of domestic and industrial waste, of the kind mentioned in the introduction, in which the filling system, located at the top of the furnace, comprises in combination: - a hopper loading, the base of which communicates with a fixed tube, with a horizontal axis coinciding with the axis of rotation of the treatment tank, - a sleeve and / or a rotating tube, located in the extension of the fixed tube and integral with the treatment tank, with connection to a central circular inlet opening, formed in the rear front wall of the treatment tank, - a filling piston, slidably mounted in the fixed tube, along its horizontal axis , between a retracted position set back from the communication between the loading hopper and this fixed tube, and an advanced position towards the treatment tank, but leaving space in front of the piston for the form ation of a "plug" of material, actuation means being provided for moving the filling piston forwards and backwards, between its

two extreme positions.

  Thus, the filling system of the rotary kiln, object of the invention, is mainly characterized by a filling piston, which can be actuated by means of a double-acting cylinder located behind this piston. The displacement of the filling piston makes it possible to create, in front of this piston, a "plug" formed with the materials to be treated in the oven, the length of this "plug" being variable depending on the cohesion of the waste to be treated. The "plug" is pushed into the treatment tank of the rotary kiln, and renewed by the arrival and pushing forward of new materials, as the furnace is fed continuously (however with a reciprocating displacement of the filling piston). This "plug", formed by waste with a particle size of, for example, between 2 and 5 centimeters, makes it possible to obtain a seal much superior to conventional rotary joints, and requires practically no maintenance; maintenance is reduced to the occasional replacement of the filling piston, mounted at the end of the cylinder, which is used to push the products towards the tank

treatment of the rotary kiln.

  Preferably, in its advanced position, the filling piston penetrates, at least partially, into the sleeve and / or the rotating tube, integral with the treatment tank. Thus, the "plug" is formed in the rotating part only, and it is avoided that this "plug" is present at the joint between the fixed tube and the rotating part, which would cause a cut of said "plug" and a

  release of abrasive material at this joint.

  According to another aspect of the invention, the system for extracting the treated products, located at the outlet of the oven, comprises in combination: - inside the treatment tank, means for recovering the solid treated products, in particular carbonaceous products, -a rotating tube with a horizontal axis coinciding with the axis of rotation of the treatment tank, and integral with this tank, with connection to a central circular outlet opening, formed in the front wall of the treatment tank , - a receiving hopper, into which the aforementioned rotating tube ends, a powder joint box, such as alumina powder, being provided for sealing around said rotating tube, inside the receiving hopper , - a conveyor screw, disposed inside the aforementioned rotating tube, the helical turns of the conveyor screw being carried by a shaft centered on the axis of rotation of the treatment tank and linked to motorized rotation drive means, and these turns are interrupted, at the front, substantially

  at the outlet of the joint box.

  In an advantageous embodiment, the conveyor screw of the extraction system has a tubular central shaft, which is extended rearwards inside the treatment tank, and which extends forwards through part by part the receiving hopper, and leading to a condenser, so as to also ensure the extraction of steam or gases from the treatment. According to an additional provision, there is provided at the base of the receiving hopper another conveyor screw, which leads to an outlet for carbonaceous products, this conveyor screw describing an ascending path and its helical turns interrupting upstream of the outlet, so that

  create and maintain a "plug" of material.

  Thanks to the various arrangements previously defined, the seal is also effectively ensured on the outlet side of the rotary kiln. In particular, the use of a joint box, with alumina powder, achieves an effective sealing means, which can absorb expansions and is particularly resistant to high temperatures, of the order of 500 C, which can be here reached, and who does not undergo

hardening or cold setting.

  There is thus obtained, on the whole, a rotary kiln for the treatment by thermolysis of domestic and industrial waste which ensures a perfect seal, on the side of the entry as of the exit, by means having a great longevity and requiring only '' minimal maintenance, so that the invention provides a truly real achievement

  industrial, with optimized reliability and efficiency.

  The invention will be better understood anyway, and others

  characteristics will be highlighted, using the description which

  follows, with reference to the accompanying schematic drawing, showing, by way of example, an embodiment of this rotary kiln for the treatment of domestic and industrial waste: Figure 1 is an overall view, or longitudinal section, of a rotary kiln according to the present invention; Figure 2 is a cross-sectional view of this rotary oven, according to 11-Il of Figure 1; Figure 3 shows, on an enlarged scale, the detail of the system

extraction of treated products.

  The rotary kiln, shown as a whole in Figure 1, consists mainly of a filling system 1, the rotary kiln 2 itself, and an extraction system 3, which

  succeed in the longitudinal direction of the oven.

  The rotary kiln 2, which constitutes the main part of the assembly, comprises a treatment tank 4, of generally cylindrical shape and with a horizontal axis 5, the sealed walls of which comprise a cylindrical side wall 4a and two circular front walls 4b and 4c, delimit a treatment enclosure 6. Towards its two ends, the tank 4 is provided externally with annular treads, respectively 7 and 8. As also shown in FIG. 2, each tread 7 or 8 rests and rolls on a pair of motorized support rollers, respectively 9 and 10, allowing the tank 4 to rotate about its horizontal axis 5. The motorized rollers 9 or 10 of each pair are themselves mounted on carriages 11, movable horizontally and symmetrically on a transverse slide 12, in particular by means of two motorized ball screws 13, coupled together by a shaft 14. These arrangements allow, in addition to the r otation of the tank 4, the automatic centering thereof with respect to a reference position of its axis 5, which can be its position at a temperature of 20 C, in order to compensate for the radial expansion of said tank 4. On the side rollers 10 located at the front of the tank 4, an axial stop is provided (not shown), while the longitudinal expansion of this tank 4 is absorbed from the rear side, where the raceway 7 has a sufficient width to maintain contact with the rollers 9

  despite the longitudinal expansion.

  The cylindrical side wall 4a of the tank 4 supports,

  internally, electric heating cartridges 15, mounted themselves

  same in heat dissipation elements, in order to obtain a

  maximum yield and ensure the longevity of said cartridges 15.

  The rear front wall 4b of the tank 4 has a central inlet opening 4d, of circular shape, delimited by a sleeve 16 of short length, integral with said tank 4 and provided with a flange. The filling system 1 of the oven, which will now be described, is connected

at this 4d entry opening.

  The filling system 1 comprises a fixed loading hopper 17, which surmounts a fixed tube 18, with a horizontal axis coinciding with the axis 5 of the tank 4, the bottom of the hopper 17 communicating with the interior of the tube 18. A rotating horizontal tube 19, located in the extension of the fixed tube 18, is connected to the flange of the sleeve 16

integral with the tank 4.

  In the duct formed by the fixed 18 and rotating tubes 19 is slidably mounted, along the horizontal axis 5, a filling piston, actuated by a double-acting cylinder 21 located behind this piston 20. The piston 20 is movable in translation along the axis, by means of the jack 21, between a retracted position (indicated in solid lines) in which this piston 20 is located behind the hopper 17, and an advanced position (indicated in dotted lines) in which the same piston 20 is introduced into the rotating tube 19, and can also be engaged in the

  sleeve 16 and thus practically reach the treatment enclosure 6.

  The extraction system 3 is shown in detail in FIG. 3. It comprises, inside the tank 4 of the rotary kiln 2, longitudinal pallets 22, leading at their front end to a recovery hopper 23, disposed at proximity of the front front wall 4a of the tank 4. This front wall has a central outlet opening 4a of circular shape, to which a horizontal tube 24, of axis coinciding with the axis 5 of the tank 4, is connected, and directed forward. The basis of

  recovery hopper 23 is thus extended by tube 24.

  Inside this tube 24 is arranged a conveyor screw, having several helical coils, mounted on a horizontal tubular shaft 26, centered on the axis 5 of the tank 4 and driven in rotation, around this axis 5, by drive means not shown. The tubular shaft 26 has a rear part which extends inside the tank 4, and a front part which extends, at the front of the tank 4,

to a condenser 27.

  This horizontal tubular shaft 26 passes right through a receiving hopper 28. A joint box 29 is mounted inside the

  receiving hopper 28, on the inlet side of the tubular shaft 26.

  The sealing of the joint box 29 is ensured by alumina powder, maintained between annular partitions, comprising rotating annular partitions 31, integral with the tube 24, and others

  fixed annular partitions 32, integral with the body of the joint box 29.

  The turns of the conveyor screw 25 are interrupted, at the front, at the level

  from the outlet of the joint box 29.

  Opposite this joint box 29, the horizontal tubular shaft 26 passes through the side wall of the receiving hopper 28, by means of a sealed bearing 33. Another similar bearing 34 is preferably provided at the front end of the tubular shaft 26, at the outlet of the latter in the condenser 27, therefore at the side wall

of this condenser 37.

  At the base of the receiving hopper 28, there is provided a conveyor screw 35, of inclined axis, which describes an ascending path and leads to an outlet orifice 36. Finally, a pipe 37 leads from the part

  high from the receiving hopper 28 to the condenser 27.

  During operation, household and / or industrial waste to be treated is introduced into the loading hopper 17 of the filling system 1, while the tank 4 of the rotary kiln 2 is rotated about the horizontal axis. 5, at a relatively low speed, for example of the order of 2 revolutions per minute. The filling piston 20 being initially held in the retracted position, the products to be treated fall into the fixed tube 18. Then, the jack 21 being actuated so as to move the piston 20 to its advanced position, the products to be treated are pushed forward in the revolving tube 19, integral with the tank 4, and they fall into this tank 4 through the sleeve 16 forming the inlet opening 4d. The waste pushed forward by the piston 20, but not fallen into the tank 4, forms in a part of the tube 19 and / or in the sleeve 16 a "plug" of material 38, of variable length, which ensures the tightness of the tank 4, on the side of its inlet opening 4d. At each back and forth movement of the piston 20, actuated by the jack 21, the "plug" 38 is renewed, that is to say it is replaced by the new products to be treated arriving in the fixed tube

  18, coming from the loading hopper 17.

  The organic waste fallen into the tank 4g is treated by thermolysis, and is transformed into carbonaceous products, which are recovered and evacuated by the extraction system 3. These products are first recovered, and extracted from the tank 4, by the pallets 22 and the hopper 23, which directs them towards the opening of the 4th outlet of the tank 4. Thus, the carbonaceous products reach, as indicated in 39, in the horizontal tube 24 where they are moved, forwards, by the conveyor screw 25 driven with the tubular shaft 26. Arrived at the front end of the conveyor screw, the carbon products 39 fall to the bottom of the reception hopper 28. The extraction of carbon products from the reception hopper 28 , is done by means of the conveyor screw 35, driven in rotation. It will be noted that the helical turns of this conveyor screw are interrupted sufficiently upstream of the outlet orifice 36, in order to create a "plug" of material 40 inside the tubular body 41

containing said screw 35.

  The products delivered by the outlet orifice 36 fall into a bucket 42, which once filled can be transported to a sorting station making it possible to separate the carbonaceous products, the ferrous metals and

  non-ferrous, and inert bodies (pebbles, glass, etc.).

  The tubular shaft 26 serves as a conduit for extracting the gases from the tank 4, and brings these gases to the condenser 27. The piping 37 also makes it possible to bring to the condenser 27 the gases extracted from the receiving hopper 28. To the condenser 27 are associated with a washer and an extractor, not shown, for the treatment and evacuation of gases. It goes without saying that the invention is not limited to the sole embodiment of this rotary kiln for the treatment of domestic and industrial waste which has been described above, by way of example; she in

  embraces, on the contrary, all variant embodiments and applications respecting the same principle, whatever their constructive details in particular.

Claims (10)

  1 - Rotating oven for the thermolysis treatment of household and industrial waste, of the type comprising: - the rotary oven (2) proper, with its treatment tank (4) of generally cylindrical shape and horizontal axis (5), rotatably mounted around its horizontal axis (5) on support rollers (9, 10), motorized means being provided for the rotary drive of this rotating part, around its horizontal axis (5), - at the head of the oven, a filling system (1) for introducing the products to be treated into the aforementioned tank (4), this system (1) comprising sealing means preventing the entry of outside air into the tank (4) , - at the outlet of the oven, an extraction system (3) of the treated solid products, as well as steam and / or gases resulting from the treatment, also with air-tightness means, - means for compensation for the longitudinal and / or radial expansion of the treatment tank (4), - means for heating of the treatment enclosure (6), delimited by the walls of the tank (4), this enclosure (6) being maintained in vacuum, characterized in that the filling system (1), located at the top of the oven, comprises in combination: - a loading hopper (17), the base of which communicates with a fixed tube (18), with a horizontal axis coinciding with the axis of rotation (5) of the treatment tank (4), - a sleeve (16) and / or a revolving tube (19), located in line with the fixed tube (18) and integral with the treatment tank (4), with connection to a circular inlet opening central (4d), formed in the rear front wall (4b) of the treatment tank (4), - a filling piston (20), slidably mounted in the fixed tube (18), along its horizontal axis, between a position set back from the communication between the loading hopper (17) and this fixed tube (18), and an advanced position towards the treatment tank (4), May s leaving a space in front of the piston (2a) for the formation of a "plug" of material (38), actuation means (21) being provided for moving the filling piston (20) towards the front and back, between its two extreme positions.   2- rotary oven according to claim 1, characterized in that the means for actuating the filling piston (20) are constituted by a double-acting cylinder (21), located behind this piston o10 (20).   3 - Rotating oven according to claim 1 or 2, characterized in that, in its advanced position, the filling piston (20) penetrates, at least partially, into the sleeve (16) and / or the rotating tube (19),   integral with the treatment tank (4).   4 - rotary kiln according to any one of claims 1 to   3, characterized in that the extraction system (3) of the treated products, located at the outlet of the oven, comprises in combination: - inside the treatment tank (4), recovery means (22, 23 ) solid treated products, in particular carbon products (39), a rotating tube (24) with a horizontal axis coinciding with the axis of rotation (5) of the treatment tank (4), and integral with this tank ( 4), with connection to a central circular outlet opening (4e), formed in the front front wall (4c) of the treatment tank (4), - a receiving hopper (28), into which the rotating tube ( 24) mentioned above, a powder seal box (29), such as alumina powder (30), being provided for sealing around said rotating tube (24), inside the receiving hopper (28 ), - a conveyor screw (25), disposed inside the aforementioned rotating tube (24), the helical turns of the conveyor screw (25 ) being carried by a shaft (26) centered on the axis of rotation (5) of the treatment tank (4) and linked to rotation drive means, and these turns are interrupted, at the front, noticeably at the outlet from the joint box (29).   - Rotary oven according to claim 4, characterized in that the means for recovering the solid treated products (39) comprise, inside the treatment tank (4), longitudinal pallets (22), terminating at their front end to a recovery hopper (23), disposed near the front front wall (4c) of the tank (4).   6 - rotary kiln according to claim 4 or 5, characterized in that the conveyor screw (5) of the extraction system (3) has a tubular central shaft (26), which is extended rearwardly inside the treatment tank (4), which extends forwards by crossing right through   share the receiving hopper (28), and leading to a condenser (27).   7 - Rotating oven according to claim 6, characterized in that opposite the joint box (29), the tubular shaft (26) passes through the side wall of the receiving hopper (28) via a sealed bearing (33), another similar bearing (34) preferably being provided at the front end of the tubular shaft (26), at the outlet of the latter in the condenser (27).   8 - rotary kiln according to claim 6 or 7, characterized in that there is provided a pipe (37) which leads from the upper part of   the receiving hopper (28) to the condenser (27).   9 - rotary kiln according to any one of claims 4 to   8, characterized in that there is provided, at the base of the receiving hopper (28), another conveyor screw (35), which leads to an outlet orifice (36) for carbonaceous products (39), this screw conveyor (35) describing an upward path and its helical turns interrupting upstream of the outlet orifice (36), so as to create and maintain a "plug" of material (40).   10 - Rotating oven according to any one of claims 1   to 9, characterized in that the means for compensating for the expansion   radial of the treatment tank (4) include a mounting of the rollers-   supports (9, 10) of said tank (4) on carriages (11), horizontally and symmetrically movable on a transverse slide (12),   in particular by means of motorized ball screws (13).   11 - Rotating oven according to any one of claims 1   to 10, characterized in that the means for heating the treatment enclosure (6), delimited by the walls of the tank (4), consist of   electric heating cartridges (15), internally supported by the cylindrical side wall (4a) of the tank (4), and mounted themselves in heat dissipation elements.