Heat Treatment Apparatus with Fire-Resistant Envelope

Abstract

To design a heat treatment apparatus which is more suitable for extremely high temperature treatment.SOLUTION: There is provided an apparatus for heat-treating a product. This apparatus comprises: a housing 2; and a conveyer for transferring a product to a space between an inlet of the housing and an outlet of the housing which is provided with a screw 10 fitted so as to be rotated at the inside of the housing according to a geometric rotation axis and an actuator for rotating the screw according to the rotation axis with the ohm heating of the screw. According to this invention, the housing comprising an envelope 12 made of a refractory material through which the screw passes, the envelope is molded in the form of a tube, and the main inner face thereof follows the profile of the screw. Also there is provided the use of the above apparatus.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a heat treatment apparatus.

[0002] The invention also relates to the use of said device for subjecting materials to heat treatment at temperatures above 800°C. [Background technology]

[0003] Thermal processing equipment commonly used in industry includes a transport member and a heating means for carrying out the thermal processing.

[0004] Thus, a thermal treatment apparatus is known having an enclosure and conveyor means for transporting material between an inlet of the enclosure and an outlet of the enclosure, the conveyor means comprising a screw mounted for rotation about an axis of rotation inside the enclosure and means for driving the screw in rotation, the apparatus also having heating means for heating the screw by Joule effect.

[0005] The material for treatment is inserted into the inlet of the enclosure, usually in divided solid form. The screw drives the material continuously towards the outlet of the enclosure. Due to the temperature of the screw, the material is gradually heated as it advances, thereby undergoing a thermal treatment.

[0006] Nevertheless, such an arrangement does not necessarily make it possible to envisage processing at high temperatures.

[0007] In EP 2 218 300 the Applicant thus proposed to have an enclosure with an inner wall made of refractory material, the screw thus constituting the means for heating the inner wall, said inner wall itself constituting the heating means for radiative heating of the divided solids advancing inside said enclosure.

[0008] The above described apparatus facilitates radiant heat treatment of the divided solids.

[0009] However, this is still not sufficient to envisage processing the material at very high temperatures. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] European Patent No. 2218300 Summary of the Invention [Problem to be solved by the invention]

[0011] The aim of the present invention is to design a thermal processing apparatus that is more suitable for processing at very high temperatures.

[0012] Another object of the invention is to propose a use of the device described above. [Means for solving the problem]

[0013] To this end, an apparatus for heat treating a material is provided, the apparatus comprising: An enclosure; a conveyor for transporting the material between an inlet of the enclosure and an outlet of the enclosure, the conveyor having a screw mounted for rotation about an axis of rotation within the enclosure, and an actuator for rotating about the axis to drive the screw; and a screw Joule effect heating element.

[0014] In accordance with the invention, the enclosure comprises an envelope of refractory material having a screw extending therethrough, said envelope being shaped as a tube having an inner surface following the contour of the screw.

[0015] As a result, the envelope fits closely around the contour of the screw, thus limiting any space between the screw and the envelope, thereby allowing for increased heat exchange within the envelope through which the material is passing.

[0016] Thus, the present invention is capable of significantly increasing the temperature of a substance.

[0017] The invention thus allows operation at high temperatures, even very high temperatures: the inventors have thus found it possible to operate at temperatures higher than 800° C., or even higher than 1000° C., more preferably higher than 1300° C., 1500° C. or even 1800° C. (the above temperatures correspond to the maximum temperatures recorded in the enclosure, which are generally found in the envelope later and near the exit of the enclosure).

[0018] Of course, the invention can be used equally well for heat treatments at lower temperatures (thus below 800° C.) should that be desirable.

[0019] Optionally, the envelope is made from a refractory ceramic.

[0020] Optionally, the envelope is in the shape of a hollow cylinder.

[0021] Optionally, the inner radius of the envelope is greater than the outer radius of the screw by a value in the range of 1 millimeter (mm) to 20 mm.

[0022] Optionally, the inner radius of the envelope is greater than the outer radius of the screw by a value in the range of 5 mm to 15 mm.

[0023] Optionally, the envelope is made up of a number of consecutive segments.

[0024] Optionally, the segments are shaped to engage with one another.

[0025] Optionally, the enclosure has an outer casing that surrounds the envelope and is at least inwardly shaped to conform to the shape of the envelope.

[0026] Optionally, the casing is shaped as a hollow cylinder.

[0027] Optionally, the enclosure has a blanket made of a thermally insulating material surrounding the enclosure.

[0028] The invention also relates to the use of the device described above for subjecting materials to heat treatment at temperatures above 800°C.

[0029] Optionally, the apparatus may also be used to thermally treat materials and gases associated with the materials that decompose at temperatures above 800°C.

[0030] Other characteristics and advantages of the present invention will become more apparent with reference to the following description of specific embodiments and the accompanying drawings.

[0031] With reference to the accompanying drawings, FIG. [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 is a schematic vertical cross-sectional view of a heat treatment apparatus according to a specific embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view of the envelope of the device shown in FIG. [Diagram 3] FIG. 3 is a perspective view of a segment of the envelope shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view of a portion of the apparatus shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] FIG. 1 shows a thermal processing apparatus in a particular embodiment of the invention and is given the general reference number 1.

[0034] In this example, the device 1 is applicable to gasify waste, for example vegetable waste or indeed polymeric waste, to produce gases, for example methane gas or indeed dihydrogen. Of course, this application is not limiting and the device 1 can be used for many other applications, to mention by way of example torrefaction, pyrolysis, vaporization, devolatilization, drying, etc. Similarly, the divided solids can be in the form of powders, granules, pieces, fibers, sheets, etc., but they can be of vegetable, mineral, chemical, etc. origin.

[0035] The apparatus 1 comprises an enclosure 2 which extends generally horizontally and is supported above the ground by a number of legs.

[0036] In this example, the enclosure 2 has an inlet 4 arranged in the cover of the enclosure 2 substantially at the first longitudinal end of the enclosure 2. In a particular embodiment, the device has an inlet pipe 5 sealed and connected to the inlet 4 of the enclosure. By way of example, the inlet pipe 5 is already connected to a device for grinding, compressing, extruding, melting or granulating the substance of interest into a divided solid, or in fact to a device for preconditioning the substance of interest in the form of a divided solid. The preconditioning device serves, by way of example, to heat and dry the substance to a certain value of temperature and relative humidity, to densify it, or to moisten it, or as otherwise to extract the interstitial air by melting it partially or totally.

[0037] The enclosure 2 also has a first outlet 6, which is arranged substantially at a second of the two longitudinal ends of the enclosure 2, in this example on the underside of the enclosure 2. In a particular embodiment, the device has an outlet pipe 7 connected in a sealed manner to the first outlet 6 of the enclosure 2. By way of example, the outlet pipe 7 is connected to a device for cooling the substance.

[0038] In this example, the enclosure 2 also has a second outlet 8, which is specifically arranged in the cover of the enclosure 2 substantially at the second of the two longitudinal ends of the enclosure 2, but which may be arranged further upstream. This second outlet 8 serves to recover gaseous by-products that may result from the thermal treatment of the divided solids. The nature of the gaseous by-products in question depends on the type of treatment in question. It may therefore be gases, fumes, steam, heavy metals, etc. In a particular embodiment, the device has an outlet pipe 9 that is hermetically connected to the second outlet 8 of the enclosure 2. By way of example, the outlet pipe 9 is connected to a device for post-treatment of the gaseous by-products, for example to purify said gaseous by-products.

[0039] A box (not shown) is fixed to each end of the enclosure 2 .

[0040] The apparatus 1 comprises a screw 10 of longitudinal axis X mounted for rotation about the longitudinal axis X inside the enclosure 2. In particular, the screw 10 is in the form of a helical coil having each of its two ends fastened to the tip of a respective shaft segment 11a, 11b, although it will be appreciated that this is merely an example and any other helical geometry can be used.

[0041] The screw 10 therefore does not have a shaft per se.

[0042] The other end of each shaft segment 11a, 11b is connected to a shaft that is coaxial and passes through the associated box.

[0043] Each box is provided with a means for rotating the screw 10 and a means for supplying electricity to the screw 10, which constitute a Joule effect heating means. In this way, the screw 10 constitutes a heat transfer means.

[0044] For this reason, most of the materials that make up the screw 10 are electrically conductive. The screw 10 has a high melting point, which is naturally chosen to have a melting point higher than the temperature at which the device will be used. It is therefore possible to have a screw made of a metal with a melting point higher than 800° C., preferably higher than 1500° C., more preferably higher than 2000° C., even more preferably higher than 2500° C., or even higher than 3000° C. It is therefore possible to have a screw 10 made of a high-melting (refractory) metal or high-melting metal alloy, such as a tantalum-based alloy, for operation at very high temperatures (the melting point of the screw 10 is substantially 3000° C.).

[0045] Moreover, if it is desired to carry out a heat treatment at high temperatures (typically higher than 800° C.) or very high temperatures (typically higher than 1500° C.), the boxes need to be arranged and connected to the enclosure 2 in such a way that the temperature present inside the boxes is compatible with the components they contain and is therefore significantly lower than 800° C. To this end, the boxes can be provided with thermal insulation and / or ventilation elements (for example cooling fins, one or more fans, which circulate a cooling fluid, etc.). Preferably, the shaft segment carrying the screw 10 is hollow, so that a cooling fluid can circulate inside the shaft segments.

[0046] For further details, reference may be made to EP 2 218 300, a patent document in the name of the present applicant, in which the drive and heating of the screw 10 and the cooling of the box and the shaft segments are also more fully described.

[0047] In accordance with the invention, the enclosure comprises an envelope 12 of refractory (high melting point) material through which extends the screw 10. In addition to the function of directly heating the material in contact with it and transporting that material longitudinally, the screw 10 also heats the envelope 12 and itself provides radiant heating to the bulk of the divided solids.

[0048] Since the majority of the screw 10 is made of electrically conductive material and is connected to at least one power supply, the envelope 12 must be made of a material that is both fire-resistant and electrically insulating. By way of example, it can be made of fire-resistant concrete or a fire-resistant ceramic material such as is commonly used to make furnace walls. Such materials have a very high melting point, in particular above 2000°C. For example, the envelope 12 may be based on alumina (Al2O3). Obviously, the envelope 12 is chosen to have a high melting point, naturally higher than the temperature at which the device will be used.

[0049] In this example, the tubes 5 , 7 , 9 likewise preferably consist of the same refractory material as the material of the envelope 12 .

[0050] With reference to the various figures, the envelope 12 is in the form of a longitudinally extending tube through which the screw 10 is disposed. The tubular envelope 12 thus circumferentially surrounds the screw 10.

[0051] In this example, the screw 10 is furthermore mounted on the underside of the envelope 12 .

[0052] The envelope 12 thus has the shape of a hollow cylinder.

[0053] The cross section of the envelope 12 matches the contour of the screw 10. The cross section of the envelope 12 is therefore in the shape of an annulus with its inside diameter surrounding the screw 10.

[0054] As a result, any gap between the screw 10 and the surrounding envelope 12 is limited.

[0055] Thus, the gas produced by partial or total pyrolysis of the substance passes through the center of the screw 10 and is forced into the corresponding helical space defined by the turns with the highest temperature, thereby making it possible to heat treat the gas coming from the substance at very high temperatures, as in the solid phase of the substance. Also, the gas is forced from the very beginning to pass through the helical space via the center of the screw 10, thereby maximizing the passage time of the gas in the center of the screw 10 while it passes through the enclosure.

[0056] To escape the envelope, the gas must travel along the spaces left between the heating turns of the screw 10, due to the very narrow approach between the screw 10 and the envelope 12. The gas completes its thermal treatment the distance it travels within the core of the screw.

[0057] This serves to limit the proportion of gas that enters the top plenum of the envelope 12, thereby increasing the period during which said gas is subjected to thermal processing.

[0058] Thus, the envelope 12 is shaped to fit as closely as possible to the diameter of the screw 10. The inside radius of the envelope 12 is preferably the same as the outside radius of 10. Under these circumstances, the screw 10 also contacts the rest of the envelope 12 (not just the underside of the envelope). Thus, the screw 10 and the envelope 12 are concentric.

[0059] For reasons of ease of assembly, it may be preferable for the radius of the envelope 12 to be slightly larger than the radius of the screw. Under such circumstances, with the screw resting on the underside of the envelope 12, the screw 10 and the envelope 12 are not concentric but slightly off-axis. Thus, a plenum is present at the top of the envelope 12. Preferably, the envelope 12 is shaped so that this plenum occupies 1 mm to 20 mm, preferably 5 mm to 15 mm, more preferably 5 mm to 10 mm.

[0060] In any case, the envelope 12 becomes a genuine sheath for the screw 10 and is shaped so as not only to match the shape of the screw 10 but also to be in close proximity to it.

[0061] Of course, the envelope 12 surrounds the screw 10 over 360°. Moreover, the envelope 12 extends at least along the entire length of the screw 10.

[0062] The envelope 12 preferably extends along the entire length of the enclosure 2 .

[0063] As an example, the envelope 12 may be manufactured by molding.

[0064] As can be seen more clearly in figures 3 and 4, in this example the envelope 12 is not made in a single piece.

[0065] This serves in particular to facilitate the placement of the screw 10 inside the envelope 12. It also makes it possible to change only a portion of the envelope 12 in case one of the segments 13 breaks.

[0066] This also makes it easier to manufacture the envelope 12. In particular, each segment 13 can be manufactured by molding.

[0067] Preferably, all the various segments 13 are identical to one another.

[0068] The envelope 12 typically comprises 3 to 7 segments.

[0069] Preferably, the various segments 13 are connected to one another by screw fastening, adhesive, snap fastening, interengagement, sealing, or the like.

[0070] Preferably, the various segments 13 are shaped so that they can engage with one another.

[0071] This provides good continuity for the envelope 12. This serves in particular to provide good leak tightness for the envelope 12, which is particularly advantageous for keeping gaseous by-products inside the envelope 12.

[0072] Furthermore, the interengagement of the various segments 13 allows the various segments 13 to be automatically centered relative to one another, thereby facilitating assembly of the envelope 12.

[0073] In this example, each segment 13 is in the form of a cylindrical tube, with a first end of the segment 13 having a circular inner groove 14 and a second end of the segment 13 (opposite the first end) having a circular extension 15 suitable for insertion into the circular inner groove 14 of an adjacent segment 13.

[0074] This provides a stepped engagement between the various segments 13 and therefore provides a good overall leak tightness.

[0075] After the various segments 13 are interengaged (eg, by ceramic seals), they may be secured together.

[0076] As can be seen more clearly in FIG. 4, in certain embodiments, the enclosure 2 has an outer casing 16 that surrounds the envelope 12 and the screw 10 and is preferably shaped to match the shape of the envelope 12 and, therefore, the screw 10.

[0077] The casing 16 is thus shaped as a longitudinally extending tube in which the envelope 12 is engaged, the tube being closed by two end walls through which pass the shaft segments 11a, 11b carrying the screw 10.

[0078] The casing 16 therefore circumferentially surrounds the envelope 12. Naturally, the casing 16 surrounds the screw 12 over 360°.

[0079] The casing 16 is therefore concentric with the envelope 12 .

[0080] The cross section of the casing 16 follows the contour of the envelope 12. The cross section of the casing 16 is therefore in the shape of an annulus with its inner diameter surrounding the envelope 12.

[0081] As a result, any space between the casing 16 and the envelope 12 is limited.

[0082] In this example, the casing 16 comprises a single piece.

[0083] The casing 16 has the shape of a hollow cylinder.

[0084] The casing 16 is made of a metallic material. Typically, the casing 16 is made of steel, such as stainless steel, and is, for example, non-magnetic.

[0085] In a preferred embodiment, the casing 16 and the envelope 12 do not contact each other.

[0086] The enclosure 2 therefore has an intermediate blanket 17 of thermally insulating material extending between the envelope 12 and the casing 16. By way of example, the blanket 17 is made of rock wool.

[0087] In this example, blanket 17 is positioned such that the outside of envelope 12 contacts the inside of blanket 17 and the inside of casing 16 contacts the outside of blanket 17 .

[0088] Thus, the blanket 17 likewise matches the shape of the enclosure 2 and the shape of the envelope 12 .

[0089] The blanket 17 is thus in the form of a longitudinally extending tube in which the envelope 12 is engaged, the blanket 17 itself extending through the casing 16 and having two end walls closing the tube, the two end walls being the walls carried by the two ends of the envelope 12 and also having the shaft segments 11a, 11b carrying the screw 10 passing therethrough, which end walls are themselves pressed against the corresponding end walls of the casing 16. The blanket 17 thus extends over the entire length of the casing 16 and is adapted to abut at both ends against the end walls of the casing 16.

[0090] Thus, the blanket 17 circumferentially surrounds the envelope 12. Naturally, the blanket 17 surrounds the envelope 12 over 360°.

[0091] Thus, the blanket 17 is concentric with the envelope 12 .

[0092] The cross section of blanket 17 follows the contours of casing 16 and envelope 12. Thus, the cross section of blanket 17 is in the shape of an annulus having its inner circle surrounding envelope 12 and its outer circle surrounded by casing 16.

[0093] The blanket 17 is in the shape of a hollow cylinder.

[0094] In this example, the blanket 17 is a single piece.

[0095] Due to its generally tubular shape with multiple layers (casing, blanket, envelope, screws) that are in close proximity or actually in contact with each other with respect to the casing 16 and blanket 17, and with respect to the blanket 17 and envelope 12, the enclosure 2 has small dimensions.

[0096] In this way, it is possible to produce a high or very high temperature heat treatment device 1 which is capable of carrying out a wide variety of processes and which is simple, versatile, compact and has low energy consumption.

[0097] The invention is not limited to the embodiments described above; on the contrary, it extends to any variant, using equivalent means, for reproducing the essential characteristics described above.

[0098] In particular, it is possible that only the envelope adapts to the shape of the screw. Thus, the casing of the enclosure may have some other shape. It would also be possible to have a casing whose inner surface only adapts to the shape of the envelope, while its outer surface is different. The casing and the blanket and / or the blanket and the envelope do not need to be in contact over the entire length of the casing, blanket and / or envelope.

[0099] The blanket does not have to be a single piece, but can consist of several elements fastened to each other and / or to the envelope and / or to the casing. It is possible to omit the blanket.

[0100] Likewise, the casing need not be a single piece.

[0101] The envelope may be in a single piece. Only the inner surface of the envelope conforms to the shape of the screw, while its outer surface can have some other shape. Thus, the envelope may be a tube, i.e. an elongated hollow member with a non-cylindrical outer shape.

[0102] The envelope and the screw can be concentric even if the inner radius of the envelope is larger than the inner radius of the screw, in which case the screw does not abut the underside of the envelope. In this example, the substance is inserted into the enclosure in the form of a divided solid, but the substance could be inserted in some other form, for example as a liquid or indeed as a gas. In the same way, one or more substances at the outlet can be recovered in the form of a gas, liquid, oil, solid, etc. The number of inlets and outlets of the enclosure must be adjusted according to the circumstances.

[0103] It should also be understood that among the possible applications of the present invention, the thermal treatment device can be installed downstream from a conventional pyrolysis installation to treat the charcoal coming from the pyrolysis in order to undergo post-treatment. The present disclosure also includes the following inventions. The first aspect is 1. An apparatus for subjecting a material to a heat treatment, said apparatus comprising: An enclosure (2); a conveyor for transporting said material between an inlet of said enclosure and an outlet of said enclosure, said conveyor having a screw (10) mounted for rotation inside said enclosure about an axis of rotation, and an actuator for driving said screw in rotation about said axis of rotation, said screw itself having no rotating shaft; and a Joule effect heating section of the screw, The enclosure comprises an envelope (12) of refractory material having the screw extending therethrough, the envelope being shaped as a tube having a major inner surface following the contour of the screw. The second aspect is The device according to a first embodiment, wherein the envelope (12) is made of refractory ceramic. The third aspect is The device according to the first or second embodiment, wherein said envelope (12) is in the form of a hollow cylinder. The fourth aspect is The device according to any one of the first to third aspects, wherein the inner radius of the envelope (12) is greater than the outer radius of the screw (10) by a value in the range of 1 mm to 20 mm. The fifth aspect is The device according to a fourth embodiment, wherein the inner radius of the envelope (12) is greater than the outer radius of the screw (10) by a value in the range of 5 mm to 15 mm. The sixth aspect is The device according to any one of the first to fifth aspects, wherein the envelope (12) is composed of a plurality of continuous segments (13). The seventh aspect is 6. The device of claim 6, wherein the segments (13) are shaped to engage with one another. The eighth aspect is The enclosure (2) is an apparatus according to any one of the first to seventh aspects, comprising an outer casing (16) that surrounds the envelope (12) and is molded at least on the inside to conform to the shape of the envelope. The ninth aspect is 13. The apparatus of an eighth embodiment, wherein the outer casing (16) is shaped as a hollow cylinder. A tenth aspect is The apparatus of any one of the first to ninth aspects, wherein the enclosure (2) has a blanket (174) of thermally insulating material surrounding the envelope. An eleventh aspect is Use of the apparatus according to any one of the first to tenth aspects for heat treating a material at a temperature above 800°C. A twelfth aspect is The use according to an eleventh aspect, wherein the apparatus is used to apply a thermal treatment to a substance and a gas associated with the substance that decomposes at a temperature above 800°C.

Claims

1. 1. An apparatus for subjecting a material to a heat treatment at a temperature above 800° C., said apparatus comprising: An enclosure (2); a conveyor for transporting said material between an inlet of said enclosure and an outlet of said enclosure, said conveyor having a screw (10) mounted for rotation inside said enclosure about an axis of rotation, and an actuator for driving said screw to rotate about said axis of rotation, said screw itself having no rotating shaft; and a Joule effect heating section of the screw, The enclosure comprises an envelope (12) of refractory material having the screw extending therethrough, the envelope being shaped as a tube having a major inner surface following the contour of the screw; The apparatus of claim 1, wherein the screw is mounted on a lower surface of the envelope, and the screw and the envelope are not concentric such that a plenum exists above the envelope.

2. The apparatus of claim 1, wherein the envelope (12) is made of refractory ceramic.

3. 3. Apparatus according to claim 1 or 2, wherein said envelope (12) is in the shape of a hollow cylinder.

4. The device according to any one of the preceding claims, wherein the inner radius of the envelope (12) is greater than the outer radius of the screw (10) by a value in the range of 1 mm to 20 mm.

5. The device according to claim 4, wherein the inner radius of the envelope (12) is greater than the outer radius of the screw (10) by a value in the range of 5 mm to 15 mm.

6. The device according to any one of the preceding claims, wherein the envelope (12) is made up of a number of consecutive segments (13).

7. 7. The device of claim 6, wherein the segments (13) are shaped to engage with one another.

8. The device according to any one of the preceding claims, wherein the enclosure (2) comprises an outer casing (16) which surrounds the envelope (12) and is shaped at least on the inside to conform to the shape of the envelope.

9. 9. The apparatus of claim 8, wherein the outer casing (16) is shaped as a hollow cylinder.

10. Apparatus according to any one of the preceding claims, wherein the enclosure (2) comprises a blanket (17) of thermally insulating material surrounding the envelope.

11. Use of an apparatus according to any one of claims 1 to 10 for heat treating materials at temperatures above 800°C.

12. 12. Use according to claim 11, wherein the device is used to apply a thermal treatment to a substance and gases associated with said substance that decompose at a temperature above 800°C.

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