Heating assembly for a sintering furnace and associated sintering furnace

Abstract

The present invention relates to a heating assembly (12) for a sintering furnace, comprising: - at least one support brick (18); and - a heater (20) comprising two elongated branches (28) cooperating with opposed sides (18A, 18B) of the or each the support bricks (18). The assembly (12) comprises a plurality of pins (22), each pin (22) passing through one of the elongated branches (28) of the heater (20) and being inserted in the or one of the support brick(s) (18) to fasten the corresponding support brick (18) to the heater (20).

Description

[0001] Heating assembly for a sintering furnace and associated sintering furnace

[0002] The present invention relates to the field of sintering furnaces, and in particular sintering furnaces used for the sintering of nuclear fuel pellets. The invention relates more specifically to the heating elements of these sintering furnaces and to their interfacing with the structure of the sintering furnace.

[0003] In sintering furnaces, and in particular in sintering furnaces used for sintering nuclear fuel pellets such as Uranium dioxide pellets, heating assemblies are used to heat the furnace to high temperatures that can reach up to 1780°C.

[0004] The heaters used in such heating assemblies have generally a W-shape, comprising two elongated branches, each branch cooperating with a corresponding side of at least one brick of the heating assembly.

[0005] In known assemblies, the assembly comprises brackets that allow cooperation between the heater and the brick, to ensure retaining the heater and the brick in the furnace.

[0006] However, such solution is not entirely satisfying. Indeed, the brackets commonly used do not resist well to the intense heat of sintering furnaces used for sintering Uranium dioxide pellets. Such brackets can get damaged in as little as one or two years, such that frequent repairs have to be operated on such a furnace.

[0007] One of the aims of the present invention is to solve such a problem, and in particular to provide a robust and reliable heating assembly for a sintering furnace.

[0008] To this end, the invention proposes a heating assembly for a sintering furnace, comprising:

[0009] - at least one support brick ; and

[0010] - a heater comprising two elongated branches cooperating with opposed sides of the or each the support bricks ; characterized in that the assembly comprises a plurality of pins, each pin passing through one of the elongated branches of the heater and being inserted in the or one of the support brick(s) to fasten the corresponding support brick to the heater.

[0011] Such pins are much more robust than the known brackets, in particular since they are subjected to shear strain rather than bending. Furthermore, since the pins are inserted in the bricks, they are protected from the heat, which further improves the stability of the heating assembly over time.

[0012] In other embodiments, the heating assembly comprises one or several of following features, taken individually or in any technically feasible combination:

[0013] - the heater is a w-shaped heater comprising a central part extending between the two elongated branches; - each pin is made of a material with a melting point superior to 1800 °C;

[0014] - the material of the pins comprises Tungsten;

[0015] - the or one of the support brick(s) is fastened to each elongated branch of the heater by at least one of the pins;

[0016] - the heating assembly comprises two support bricks;

[0017] - the heating assembly comprises, for each support brick, at least one metallic holder fixed to one of the elongated branches of the heater and configured to support the extremity of the corresponding support brick;

[0018] - the heating assembly comprises a holdup band cooperating with the support brick(s) and the heater;

[0019] - the holdup band wraps around the central part of the heater and the support brick(s);

[0020] - the heater is made in a material comprising molybdenum and / or in tungsten;

[0021] - each support brick is cylindrical or a rectangular cuboid;

[0022] - each support brick is refractory.

[0023] The invention also relates to a sintering furnace comprising at least one heating assembly of the aforementioned type.

[0024] In other embodiments, the sintering furnace comprises one or several of following features, taken individually or in any technically feasible combination:

[0025] - the two elongated branches of the heater extend according to an elevation direction of the sintering furnace;

[0026] - the sintering furnace is configured to be used for the sintering of nuclear fuel pellets, in particular Uranium dioxide pellets.

[0027] The invention and its advantages will be better understood on reading the following description given solely by way of non-limiting examples and with reference to the appended drawings, in which:

[0028] - Figure 1 is a schematic view of a sintering furnace according the invention comprising a heating assembly;

[0029] - Figure 2 is a schematic perspective view of the lower part of the heating assembly of Figure 1 (the upper structural bricks are not shown); and

[0030] - Figure 3 is a schematic perspective view of the heating assembly of Figure 1 .

[0031] Figure 1 shows a sintering furnace 10 comprising a heating assembly 12.

[0032] In a variant (not shown), the sintering furnace 10 comprises a plurality of heating assemblies 12.

[0033] The sintering furnace 10 for example defines an elevation direction Z, which is preferably vertical in a normal use of the sintering furnace. In the example shown in the figures, the sintering furnace 10 comprises a structure 11 defining an interior heating space 13 adapted to heat elements located in said heating space 13, and in particular configured for sintering said elements.

[0034] In a preferred embodiment, the sintering furnace 10 is used for the sintering of nuclear fuel pellets and more particularly Uranium dioxide pellets.

[0035] More particularly, the sintering furnace 10 is part of a manufacturing line of nuclear fuel elements and in particular of nuclear fuel pellets.

[0036] For example, the sintering furnace 10 is used for the sintering at a controlled temperature of green pellets, the green pellets being for example formed by the pressing of powdered Uranium dioxide, to form dense and stable nuclear fuel pellets.

[0037] The sintering furnace 10 is preferably adapted to be heated to the controlled temperature by means of the at least one heating assembly 12.

[0038] The controlled temperature is for example higher than or equal to 1700°C, in particular between 1720°C and 1800°C, and more particularly between 1770°C and 1790°C.

[0039] As shown on Figures 1 and 3, the heating assembly 12 is divided into a lower part 14 shown in details on Figure 2 and an upper part 16, the upper part 16 being arranged above the lower part 14 according to the elevation direction Z.

[0040] Preferably, the lower part 14 is located inside the heating space 13 and the upper part 16 outside the heating space 13.

[0041] As shown on Figures 2 and 3, the heating assembly 12 comprises at least one support brick 18, and more particularly two support bricks 18, a heater 20 and a plurality of pins 22.

[0042] Advantageously, the heating assembly 12 comprises at least one upper structural brick 23, and for example two upper structural bricks 23 as shown on Figure 3.

[0043] In a preferred embodiment, the heating assembly 12 also comprises, for each support brick 18, at least one metallic holder 24.

[0044] In an advantageous embodiment, the heating assembly 12 also comprises a holdup band 26 cooperating with the support brick(s) 18 and the heater 20.

[0045] As shown on Figures 2 and 3, each support brick 18 is preferably located in the lower part 14 of the heating assembly 12.

[0046] In the embodiment where the heating assembly 12 comprises two support bricks 18, the support bricks 18 are arranged one above the other according to the elevation direction Z.

[0047] As shown on Figure 2, each support brick 18 is for example cylindrical, preferably extending according to an axis parallel to the elevation direction Z.

[0048] In a variant (not shown), each support brick 18 is for example a rectangular cuboid. Each support brick 18 comprises a first side 18A and a second side 18B opposed to the first side 18A, in particular according to a direction perpendicular to the elevation direction Z.

[0049] In an advantageous manner, each of the support bricks 18 comprises a groove defined in each of its side 18A, 18B and extending according to the elevation direction Z. Each groove preferably extends vertically.

[0050] More particularly, each support brick 18 has a height comprised between 10 cm and 20 cm.

[0051] In particular, each support brick 18 has a diameter comprised between 5 cm and 10 cm.

[0052] Each support brick 18 is preferably refractory, and is for example made of a refractory material such as terracotta, aluminum oxide or silicon oxide.

[0053] In particular, each support brick 18 remains chemically and physically stable at temperature above 1000 °C, and preferably above 1800 °C.

[0054] The heater 20 comprises two elongated branches 28.

[0055] As shown on Figures 2 and 3, the two elongated branches 28 preferably extend parallel to each other. In particular, each of the two elongated branches 28 extends in a direction parallel to the elevation direction Z of the sintering furnace 10.

[0056] The heater 20, and in particular the two elongated branches 28, extend partly outside the heating space 13. Each of the two elongated branches 28 defines for example an upper end 30, in particular located in the upper part 16 of the heating assembly 12, and a lower end 32, in particular located in the lower part 14 of the heating assembly 12. Each of the two elongated branches 28 extends linearly between these two ends 30, 32 according to the elevation direction Z of the sintering furnace 10.

[0057] Each of the two elongated branches 28 cooperates with one of the sides 18A, 18B of each the support brick 18.

[0058] Preferably, each of the elongated branches 28 is accommodated in one of the grooves defined in the corresponding side 18A, 18B of each support brick 18.

[0059] As shown on Figure 2, each of the elongated branches 28 is for example divided into a first portion 34 cooperating with the support brick(s) 18 and a second portion 36.

[0060] More preferably, the first portion 34 extends between the upper end 30 and an intermediate point 31 on the elongated branch 28. The intermediate point 31 is for example located in the lower part 14 of the heating assembly 12. As shown on Figure 3, the first portion 34 extends partly in the lower part 14 and partly in the upper part 16 of the heating assembly 12. In a preferred embodiment, the first portion 34 of each elongated branch 28 consists of a plurality of overlapping strips, and preferably of strips made of tungsten.

[0061] In the specific embodiment shown on Figure 2, the first portion 34 of each elongated branch 28 consists of three overlapping strips including an inner strip 35, a middle strip 39 and an outer strip 37.

[0062] The second portion 36 of each of the elongated branches 28 preferably extends only in the lower part 14 of the heating assembly 12, thus inside the heating space 13 of the sintering furnace 10 in order to define an active heating zone.

[0063] The second portion 36 consists advantageously of only one strip.

[0064] In the specific embodiment shown on Figure 2, the strip forming the second portion 36 extends in the continuity of the middle strip 39, in order to achieve the highest electrical resistance in this second portion 36.

[0065] In a preferred embodiment illustrated on Figure 2, the heater 20 is a w-shaped heater comprising a central part 38 extending between the two elongated branches 28.

[0066] In particular, the central part 38 comprises two branches 38A, 38B joined by a bend 38C, and for example has the shape of an inverted U or of an inverted V.

[0067] More particularly, as shown on Figure 2, the end of each the two branches 38A, 38B of the central part 38 located opposite the bend 38C is connected to a corresponding end of a corresponding one of the two elongated branches 28, and in particular to the lower end 32 thereof.

[0068] The bend 38C of the central part 38 is for example located below the support brick(s) 18, and in particular facing the intermediate point 31 of each elongated branch 28.

[0069] The heater 20 is preferably made of a material with a melting point superior to 1800 °C.

[0070] Advantageously, the heater 20 is made of a metallic material comprising molybdenum and / or tungsten.

[0071] As shown on Figure 2, each pin 22 passes through one of the elongated branches 28 of the heater 20 and is inserted in one of the support bricks 18 to fasten the corresponding support brick 18 to the heater 20.

[0072] Preferably, each of the support bricks 18 is fastened to each elongated branch 28 by at least one of the pins 22.

[0073] More particularly, each pin 22 is inserted into one traversing hole defined in one of the elongated branches 28, in particular in its first portion 34, and one corresponding blind hole defined in one of the support brick 18, and in particular in one corresponding side 18A, 18B of said support brick 18. In the specific embodiment illustrated in Figure 2, one traversing hole is defined in each one of the strips 35, 37, 39 of the first portion 34 of the corresponding elongated branch 28, such that the corresponding pin 22 passes through all three strips 35, 37, 39.

[0074] For example, in the embodiment illustrated on Figure 2, the heating assembly 12 comprises eight pins 22 for the fastening of each of the support bricks 18 to the elongated branches 28 of the heater 20, and in particular four pins 22 for each elongated branch 28.

[0075] Preferably, each pin 22 extends in a direction perpendicular to the elevation direction Z.

[0076] Advantageously, two opposite pins 22, i.e. two pins 22, one on each side 18A, 18B of a same support brick 18 and facing each other, do not touch each other, in order to avoid the creation of an electrical short circuit.

[0077] More particularly, each pin 22 comprises a head 22A and a rod 22B extending with the rod axis perpendicular to the elevation direction Z.

[0078] For example, the head 22A of each pin 22 rests against the corresponding elongated branch 28, or against the corresponding reinforcing branch 37. The rod 22B passes through the elongated branch 28 and is inserted into the corresponding support brick 18.

[0079] The rod 22B of each pin 22 has for example a diameter comprised between 0.4 cm and 0.8 cm. The head 22A of each pin 22 has for example a diameter comprised between 1 .0 cm and 1 .5 cm.

[0080] Advantageously, each pin 22 is made of a material with a melting point superior to 1800 °C, and in particular a metallic material.

[0081] Preferably, each pin 22 is made of a material comprising Tungsten, and preferably consisting of Tungsten.

[0082] Alternatively, each pin 22 is made of a material comprising Molybdenum, and preferably consisting of Molybdenum.

[0083] Each upper structural brick 23 is preferably fixed to the structure 11 of the sintering furnace 10.

[0084] Each upper structural brick 23 are for example located in the upper part 16 of the heating assembly 12 and is preferably located outside the heating space 13.

[0085] In the embodiment shown on Figure 3 where the heating assembly 12 comprises two upper structural bricks 23, the upper structural bricks 23 are arranged one above the other according to the elevation direction Z.

[0086] The upper structural brick(s) 23 are preferably disposed above the support bricks 18 according to the elevation direction Z. Preferably, as shown on Figure 3, one of the upper structural bricks 23, in particular the one closest to the lower part 14, is laid on top of one of support bricks 18, in particular the one closest to the upper part 16.

[0087] In the particular embodiment of Figure 3, said upper structural brick 23 closest to the lower part 14 comprises preferably a blind hole 54 to receive an upper end of the holdup band 26.

[0088] For example, each upper structural brick(s) 23 is a rectangular cuboid as shown on Figure 3 or cylindrical.

[0089] The heater 20 is advantageously fixed to the upper structural brick(s) 23, so that the heater 20 is maintained in a vertical position, i.e. extending according to the elongated direction Z.

[0090] Advantageously, each upper structural brick 23 comprises two trough passages 52, in particular extending according to the elevation direction Z. Each elongated branch 28 of the heater 20 extends preferably inside the corresponding passage 52.

[0091] For example, the heater 20 is fixed to at least one of the upper structural brick 23 with at least one bracket 50, and preferably one bracket 50 for each elongated branch 28 as shown on Figure 3.

[0092] In the particular embodiment shown on Figure 2, each metallic holder 24 is fixed to one of the elongated branches 28 of the heater 20. Each metallic holder 24 is configured to support an extremity of the corresponding support brick 18, and in particular a lower extremity of the corresponding support brick 18.

[0093] In a preferred embodiment, the heating assembly 12 comprises, for each support brick 18, two metallic holders 24, i.e. one for each elongated branch 28 of the heater 20.

[0094] Each metallic holder 24 is for example a bracket defining a bearing surface for each support brick 18.

[0095] As shown on Figure 2, the holdup band 26 preferably cooperates with the support brick(s) 18 and the heater 20.

[0096] In particular, the holdup band 26 wraps around the central part 38 of the heater 20, and in particular, the bend 38C, and the support brick(s) 18.

[0097] The holdup band 26 is preferably made of a material with a melting point superior to 1800 °C, and in particular a metallic material such as tungsten or molybdenum.

[0098] Such a heating assembly 12 allows fastening the heater 20 inside the sintering furnace 10, in particular such that the lower part of the heater 20 is positioned in the heating space 13, in order to efficiently heat it to a determined temperature. Thanks to the pins 22, such a fastening is robust and reliable. Indeed, such pins 22 are much more robust than the known brackets, in particular since that they are subjected to shear strain, rather than bending.

[0099] Furthermore, since the pins 22 are inserted in the bricks 18 over a substantial part of their length, they are protected from the heat, which further improves the stability of the heating assembly 12 over time.

[0100] Thus, the heating assembly 12 according to the invention allows extending the lifetime of the heater 20, in particular up to ten years.

[0101] Therefore, the maintenance cost and the shutdown time needed to replace of the heater 20 can be reduced thanks to such a heating assembly 12.

[0102] Moreover, the pins 22 do not affect the performance of the heater 20.

Claims

CLAIMS1. Heating assembly (12) for a sintering furnace (10), comprising:- at least one support brick (18); and- a heater (20) comprising two elongated branches (28) cooperating with opposed sides (18A, 18B) of the or each the support bricks (18); characterized in that the assembly (12) comprises a plurality of pins (22), each pin (22) passing through one of the elongated branches (28) of the heater (20) and being inserted in the or one of the support brick(s) (18) to fasten the corresponding support brick (18) to the heater (20).

2. Heating assembly (12) according to claim 1 , wherein the heater (20) is a w-shaped heater comprising a central part (38) extending between the two elongated branches (28).

3. Heating assembly (12) according to claim 1 or 2, wherein each pin (22) is made of a material with a melting point superior to 1800 °C.

4. Heating assembly (12) according to claim 3, wherein the material of the pins (22) comprises Tungsten.

5. Heating assembly (12) according to any of the preceding claims, wherein the or one of the support brick(s) (18) is fastened to each elongated branch (28) of the heater (20) by at least one of the pins (22).

6. Heating assembly (12) according to any of the preceding claims, comprising two support bricks (18).

7. Heating assembly (12) according to any of the preceding claims, comprising, for each support brick (18), at least one metallic holder (24) fixed to one of the elongated branches (28) of the heater (20) and configured to support the extremity of the corresponding support brick (18).

8. Heating assembly (12) according to any of the preceding claims, comprising a holdup band (26) cooperating with the support brick(s) (18) and the heater (20).

9. Heating assembly (12) according to claims 2 and 8, wherein the holdup band (26) wraps around the central part (38) of the heater (20) and the support brick(s) (18).

10. Heating assembly (12) according to any of the preceding claims, wherein the heater (20) is made in a material comprising molybdenum and / or in tungsten.1 1. Heating assembly (12) according to any of the preceding claims, wherein each support brick (18) is cylindrical or a rectangular cuboid.

12. Heating assembly (12) according to any of the preceding claims, wherein each support brick (18) is refractory.

13. Sintering furnace (10) comprising at least one heating assembly (12) according to any of the preceding claims.

14. Sintering furnace (10) according to claim 13, wherein the two elongated branches (28) of the heater (20) extend according to an elevation direction (Z) of the sintering furnace (10).

15. Sintering furnace (10) according to claim 13 or claim 14 configured to be used for the sintering of nuclear fuel pellets, in particular Uranium dioxide pellets.

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