Method for sintering carbon bodies in a furnace

Abstract

The invention relates to a method for sintering carbon bodies (16) in a furnace comprising at least a first furnace chamber (11) for receiving the carbon bodies, which are accommodated in a packing material (23), the carbon bodies being arranged between lateral chamber walls (12, 13, 21) of the furnace chamber, and the furnace chamber serving to form a preheating zone V, a heating zone H provided with a heating device, and a cooling zone A, wherein a packing material (23) made, at least in part, of a highly heat-conductive material is used.

Claims

1. A method for sintering carbon bodies in a furnace comprising at least a first furnace chamber forming a preheating zone V, a heating zone H provided with a heating device, and a cooling zone A, comprising the steps of: accommodating each of a plurality of carbon bodies in a packing material made, at least in part, of a heat-conductive material, and arranging the carbon bodies between lateral chamber walls of the furnace chamber such that the packing material is in direct contact with the carbon bodies and the surface of the lateral chamber walls.

2. The method according to claim 1, wherein the packing material is made, at least in part, of a graphite material.

3. The method according to claim 2, wherein the packing material is a graphite material.

4. The method according to claim 1, wherein the graphite material comprises an artificial graphite.

5. The method according to claim 4, wherein the artificial graphite is granulated.

6. The method according to claim 3, wherein the graphite material comprises graphitized petroleum coke.

7. The method according to claim 2, wherein the graphite material comprises a recycled material made of the residue of spent electrodes.

8. The method according to claim 1 further comprising the steps of arranging the carbon bodies accommodated in the packing material in a first line and conveying the carbon bodies horizontally on a first conveyor through a furnace channel formed between the chamber walls of the furnace chamber in such a manner that the line of carbon bodies is successively conveyed through the preheating zone V, the heating zone H and the cooling zone A.

9. The method according to claim 8, further comprising the step of conveying a second line of carbon bodies on a second conveyor parallel to and against the conveying direction of the first conveyor the second conveyor conveying the second line of carbon bodies horizontally through a furnace channel of a second furnace chamber adjacent to the first furnace chamber, wherein a furnace channel of the first furnace chamber is separated from the furnace channel of the second furnace chamber by a heat-transferring chamber wall in such a manner that a preheating zone V of the first furnace chamber is arranged opposite a cooling zone A of the second furnace chamber and heat is transferred between the cooling zone A and the preheating zone V via the chamber wall.

10. The method according to claim 1 wherein wall elements of the chamber wall comprise a refractory material whose ceramic mass contains silicon carbide or graphite, and wherein heat is transferred via the refractory material.

11. The method according to claim 1, wherein the chamber wall further comprises a heat-conductive material core accommodated in a shell made of refractory material within the wall elements of the chamber wall, and heat is transferred via the heat conductive material core.

12. The method according to claim 11, wherein the material core made of graphite.

13. The method according to claim 11, wherein a defined heat conductivity is set by the shape of the material core.

14. The method according to claim 1, wherein to dissipate heat from the wall elements, a heat transfer medium is circulated through flow channels formed in the wall elements, the flow channels forming a meandering wall channel in the chamber wall.

15. The method according to claim 14, wherein air is used as the heat transfer medium.

Description

(1) Below, an embodiment of the method according to the invention and an embodiment of the furnace according to the invention are explained in more detail with reference to the drawing.

(2) FIG. 1: shows an isometric view of part of a furnace;

(3) FIG. 2: shows a cross-section view of the furnace illustrated in FIG. 1;

(4) FIG. 3: shows a schematic view of a furnace configured as a counter-travel furnace;

(5) FIG. 4: shows an illustration of an energy balance of a furnace operated as a counter-travel furnace;

(6) FIG. 5: shows a wall element of a chamber wall;

(7) FIG. 6: shows another embodiment of a wall element;

(8) FIG. 7: shows a chamber wall composed of multiple wall elements.

(9) FIG. 1 shows a section of a furnace channel 14 of a furnace 10 comprising a furnace chamber 11, whose lateral chamber walls 12, 13 form the furnace channel 14. The furnace chamber 11 has a chamber bottom formed by a conveyor 15, on which carbon bodies 16 are arranged in a line 17. In the case at hand, the conveyor 15 forming the chamber bottom is composed of a plurality of furnace cars 18, which are arranged one behind the other in the longitudinal direction of the furnace channel 14 and which form a chamber bottom surface that is substantially continuous in the longitudinal direction of the furnace channel 14 and each of which is guided in the furnace channel 14 in a rail guide 19 formed at the bottom for a longitudinal feed of the furnace car 18.

(10) The illustration of the furnace 10 in FIG. 1 merely shows a longitudinal section of the furnace channel 14 of the furnace, said section being a preheating zone 20 of the furnace channel 14 in the case at hand, the furnace channel 14 being divided into a preheating zone V, a heating zone H, and a cooling zone A, as illustrated in FIG. 3 in a schematic view of a furnace 10 configured as a counter-travel device. As FIG. 3 further shows, the furnace 10 has another furnace channel 20 in addition to furnace channel 14, furnace channel 20 being formed in particular by the addition of another chamber wall 21 to chamber walls 12, 13, another furnace chamber 40 thus being formed. The second furnace channel 20 is provided with a conveyor 22, which is configured as a counter conveyor and allows feeding the furnace cars 18 against the conveying direction of the first conveyor 15. Both furnace channels 14 and 20 are provided with a heating device opposite each other, corresponding heating zones H thus being formed opposite each other.

(11) Referring to the embodiment illustrated in FIG. 3, during operation of the furnace 10, the furnace cars 18 in furnace channel 14 are moved through furnace channel 14 from the right to the left, a starting section of furnace channel 14 thus forming the preheating zone V. Having passed the heating zone H, the carbon bodies 16 on the furnace cars 18 enter the cooling zone A and are ultimately conveyed out of the furnace channel 14. In furnace channel 20, which is parallel to furnace channel 14, the carbon bodies 16 are moved from the left to the right, which means that the preheating zone V of furnace channel 20 is formed opposite the cooling zone A of furnace channel 14 and that, having passed the heating zone H, the carbon bodies 16 enter the cooling zone A at the right-hand end of furnace channel 20.

(12) Operation of the furnace 10 with conveyors 15 and 22 conveying in opposite directions and the resulting arrangement of cooling zones A and preheating zones V opposite each other has the effect that the temperature gradient due to operation in the opposite zones allows effective cooling and heating of the carbon bodies 16 without requiring an external energy supply.

(13) The particular energy efficiency of the furnace 10 is additionally supported by the fact that, as the packing material 23, a packing material 23 that is made, at least in part, of a graphite material is used, which serves to accommodate the carbon bodies 16 and which, as is illustrated in particular in FIGS. 1 and 2, shields the carbon bodies 16 against the ambient air.

(14) As shown in particular in FIG. 2, the packing material 23, which is in immediate contact with both the carbon bodies 16 and the surface of the chamber walls 12, 13, allows heat transfer by heat conduction, the particular heat conductivity of the packing material 23, which is up to three times the heat conductivity of petroleum coke depending on the amount of graphite material, allowing a particularly good heat transfer between the chamber walls 12, 13, which are provided with flow channels 24 for conducting heating gases, and the carbon bodies 16.

(15) Using a material core 27 of isotropic graphite, the heat resistance of a wall element 25, which is illustrated in FIG. 5 and which has to have a thickness of about 400 mm for strength reasons, can essentially be reduced to the heat resistance of the ceramic shell.

(16) In order to achieve a particularly good heat transfer between the heating gases flowing in the flow channels 24 of the chamber walls 12, 13 and the packing material 23, the chamber walls 12, 13 are composed of wall elements 25 in which the flow channels 24, as illustrated by way of example in FIG. 5, are formed by inserting a material core 27 made of graphite into a cavity 26 of the wall element 25, the material core 27 dividing the cavity 26 into the flow channels 24. Thus, the wall element 25 illustrated in FIG. 5 is substantially formed by a graphite body inserted into a shell 28 made of refractory material.

(17) In this way, a very high recuperation rate of up to 80% is achieved. FIG. 4 shows, by quantity, the achievable energy balance of a furnace 10 operated with a packing material 23 formed by a graphite granulate and with a chamber wall composed of wall elements having a material core made of graphite. According to FIG. 4, heat recovery covers about 80% of the required heating energy, the heating device of the furnace being operated solely with volatile hydrocarbons from the carbon bodies as fuel. The outlet air temperature is high enough for it to also cover the heating energy for the carbon bodies 16, which may be formed by anodes, for example, i.e. for heating a kneading mixer, for example, which mixes the paste for the anodes, which consists of calcined coke and pitch. This means that the furnace does not require primary energy; it operates exothermically.

(18) FIG. 6 shows a wall element 30 that has a graphite material core 32 made of graphite and embedded in a shell 31 made of a refractory material. The refractory material consists of a ceramic mass that contains silicon carbide and/or graphite for increasing its heat conductivity. A flow channel 33 is formed in the refractory material of the shell 31.

(19) As shown in FIG. 7, multiple wall elements 30 arranged in a line can be combined to form a chamber wall in such a manner that the flow channels 33 of the individual wall elements 30 are connected to each other via bends 34 so as to form a meandering wall channel 34. Similarly to the flow channels 33, the bends, too, can be arranged in correspondingly formed wall elements, notwithstanding the simplified illustration of FIG. 7.