WO2014147434A1

WO2014147434A1 - Method and installation to produce graphite bodies

Info

Publication number: WO2014147434A1
Application number: PCT/IB2013/000486
Authority: WO
Inventors: Gerhard Hubweber
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-03-21
Filing date: 2013-03-21
Publication date: 2014-09-25
Anticipated expiration: 2015-09-21
Also published as: AT515863A5; DE112013006851B4; DE112013006851T5; AT515863B1; AT515863A2

Abstract

The present invention relates to a method and an installation to produce graphite bodies from high purity carbon containing granular material like petrol coke or coal tar pitch based coke and at least one binder which can be coked at elevated temperatures using puffing inhibitors, as well as a graphite body wherein said puffing inhibitor is present in a grain size of lower than 2 μm, preferably lower than 1 μm.

Description

METHOD AND INSTALLATION TO PROCUCE GRAPHITE BODIES Description of the invention Technical field:

The Invention concerns a method for producing graphite bodies from a granular solid carbon containing material and at least one liquid binder able to be coked at elevated temperatures and additives, comprising at least the steps mixing, forming, baking and graphitisation, wherein an additive to reduce the irreversible volume expansion at temperatures above 1400 °C is used, a graphite body produced by said method and an installation for executing the method.

Background of the invention:

Graphitized carbon bodies, in the following named graphite bodies, are commonly used in electrochemical and electro thermal processes due to their electrical and thermal conductivity and due to the ability to withstand extreme high temperatures. One of the main fields of application for carbon bodies are graphite electrodes for electric arc furnaces, used in steel plants to melt scrap or to refine molten steel as so called ladle furnaces. Furthermore, graphite bodies are used for furnace linings, for instance for the lower part of blast furnaces.

The production process for graphite bodies has been well known since many decades (Winnacker Kiichler, Chemische Technologie, Band 3 (Anorganische Technologie II), 4. Auflage, Carl Hanser Verlag Miinchen Wien 1983). Raw materials, which are used for the production of graphite bodies, are among others:

- high purity carbon containing materials in granular form, like petrol cokes or coal tar pitch based cokes, especially in the form of needle cokes and

- liquid binders which can be coked at elevated temperatures, like for example coal tar pitch or petrol pitch or other organic liquids like for example phenolic resins and

- additives.

The production process contains at least the steps of

- milling and sieving the coke,

- mixing of different fractions of the coke with a binder which can be coked at elevated temperatures and additives in a hot mixing step to get a so called green mass,

- forming of so called green bodies either by vibrating molding or by extrusion techniques,

- baking of the green bodies at temperatures up to 1000 °C to coke the binder and to get stable carbon bodies, and - graphitisation of the carbon bodies at temperatures of about 3000 °C using electrically generated heat.

One of the problems in the production process of the state of the art is the forming of cracks at elevated temperatures between 1400 °C and 2000 °C during the graphitisation step. The reason for the formation of these cracks is well known and described as so called puffing caused from sulfur, which sulfur is present as an impurity in the raw materials. The sulfur is exciting a volume expansion in the mentioned temperature range causing an increase in porosity of the graphite bodies. To control the puffing and to reduce the risk of forming cracks, a lot of different solutions are known. Most of these solutions result in the adding of metals or compounds of metals to the coke before or during the mixing step. The addition of these substances - named inhibitors - results in the advantage of controlling the puffing. However, these substances lead to an increase of the coefficient of linear thermal expansion of the graphite bodies. This increase causes a loss in thermo shock resistance and an increase in ash content. All in all, for the application of graphite bodies as electrodes for electric arc furnaces the negative effects of the inhibitor cause an increase of the consumption of graphite per ton of molten steel. If in the further description and the accompanying claims reference is made to a puffing inhibitor it is understood to include any substance reducing the irreversible volume expansion at temperatures above 1400 °C.

In practice, quantities of between 1 % and 2 % of the inhibitor referred to the total dry mass in the green mixture are used and described in the literature, as for example in DE 39 07 158. To minimize the negative impact of the substances used as inhibitor in the graphite bodies it is well known that it is necessary to minimize the needed quantity of the inhibitor. Additionally, a good distribution of the inhibitor in the carbon bodies which have to be graphitized is indispensable.

In the state of the art, different propositions have been made to get a good distribution:

In GB 733,073 A it is described to use 1 to 5 % by mass of iron, chromium, copper or nickel as well as oxides thereof as puffing inhibitor. These substances are dosed to the coke, preferably at the grinding stage, to have an excellent distribution of the puffing controlling substance in the green carbon body.

FR 1 491 497 A describes the addition of chromium, nickel or cobalt or a mixture of said metals as catalyst to the mixture of coke and binder. ln the US 3 563 705 B it is described to use in the mixture of coke and binder in addition to conventional puffing inhibitors, like iron or calcium oxide, also low quantities of titanium and zirconium compounds to reduce the puffing.

US 3 338 993 B describes the use of fluorides of calcium, magnesium, strontium or barium or mixtures thereof for puffing reduction.

JP 62059511 A describes the use of an iron compound like iron oxide or iron hydroxide having≤ 3μ average particle diameter to be blended with coal tar needle coke and one or more compounds selected from Ca-compounds, Mg-compounds, Ce-compounds or La- compounds as inhibitors. With these substances, the coke is blended before being mixed with pitch to produce graphite electrodes. However, substances with a single corn diameter of lower than 3 pm always form agglomerates which cannot be destroyed in a mixing process, so that the actual diameter of the iron compound in the mixture with pitch is much higher than 3μ. Furthermore, if fine grained substances are brought into contact with liquids, the fine grains form agglomerates which are quite hard and cannot easily be destroyed by a mixer. Therefore, the actual diameter of the iron compound in the mixture is dictated by the diameter of the agglomerate but not the diameter of the single corn.

From DE 39 07 158 C1 it is known to use substances as inhibitor which are at least partially soluble in the liquid binder to create a good distribution of the inhibitor. The disadvantage is that the proposed substances from the class of metal sulfonates, metal caboxylates or metal phenolates are very cost extensive and risky for health.

Also from DE 39 07 155 C1 it is known to add the puffing inhibitor already in the coking plant into the feedstock to be coked, which inhibitor substances are at least partially soluble in the feedstock. Like in DE 39 07 158 C1 , the use of substances from the class of metal sulfonates, metal caboxylates or metal phenolates is proposed.

Summary of the invention:

The goal of the present invention is to ameliorate the effect of cost effective solid puffing control substances such as metals or metal compounds (preferably metal oxides) which are insoluble in binders like petrol pitch or coal tar pitch or phenolic resins. This amelioration will result in a reduction of the needed quantity of puffing control substance improving the quality of the graphite bodies produced following the method of the invention. Second goal of the present invention is to create a graphite body produced according to the method of the invention, which is characterized in the form of the puffing control substance being in the graphite body. A further, third goal of the present invention is to create an installation in which the proposed method can be used. It is not the intention of the invention to find new substances but to use the very well known ones in a better way.

According to the present invention, a method to produce graphitized carbon bodies from carbon containing granular material, like petrol coke or coal tar pitch coke, and at least one liquid binder which can be coked at elevated temperatures is provided, said method comprising at least the steps of mixing, coking and graphitizing, wherein a puffing inhibitor from the class of metals or metal compounds, preferably metal oxides, is added to the components before they are formed to green bodies, wherein the puffing inhibitor is used in a grain size of lower than 2 pm, preferably lower than 1 pm, and that the puffing inhibitor is dispersed in the liquid binder before the binder is mixed with the granular carbon containing material. Doing this, most of the particles of the fine grained puffing inhibitor are present in the liquid binder as single corns with an extremely high contact surface for the reaction with sulfur. This results in the possibility of a reduction of the needed quantity of puffing inhibitor down to nearly stoichiometric amounts. The mixture of liquid binder and dispersed puffing inhibitor is then mixed with solid carbon containing material, resulting in a very good distribution of the extremely fine particles of the puffing inhibitor in the mixture to form green carbon bodies. This excellent distribution is present up to the graphitization step and this is the unique micro structure of the inhibitor in the obtained graphite bodies, which is quite different to other carbon bodies due to having extremely good distribution of mostly single corns of the fine grained inhibitor.

According to a further preferred embodiment of the present invention, the method comprises the steps of

- dividing the quantity of the liquid binder for the mixing process into two parts of different size,

- preheating the puffing inhibitors to the temperature of the liquid binder,

- dispersing the puffing inhibitors in the smaller quantity of the binder in a content of solid material in the mixture of more than 50 % by mass, in particular of more than 70 % by mass,

- combining the small quantity of the liquid binder with the big quantity,

- homogenizing the dispersed puffing inhibitors in the whole liquid binder quantity and

- combining the liquid binder containing dispersed puffing inhibitors with granular solid carbon containing material.

In a preferred kind of this embodiment, for dispersing the puffing inhibitor, a shear rate in the liquid binder of more than 1000 [1/sec], preferably of more than 10.000 [1/sec] is used and an energy input of more than 5 kWh per ton of dispersion within 10 minutes, preferably of more than 8 kWh per ton of dispersion within 10 minutes is done (in other words: if 50 kg of a mixture of liquid binder and puffing inhibitor is dispersed for 10 minutes, the power of the driving motor has to have minimal 1 ,5 kW or preferably minimal 2,4 kW to be able to bring an energy of 0,25 kWh, preferably of 0,4 kWh into the dispersion). This can be done with dispersing machines which work better with high solid content to create high shear rate in the mixture, like for example a dissolver disc which is known from the paint industry and can be worked in the method of the present invention with a rotation speed of more than 10 [m/sec], or a wet grinding mill or even an ultrasonic device as dispersing machine. To have the puffing inhibitors at the same temperature as the liquid binder, it is foreseen for binders like petrol pitch or coal tar pitch, which are commonly used at temperatures above 150 °C, in particular between 170 and 220 °C, to preheat the puffing inhibitors in a preheating furnace before introducing them into the liquid binder.

The installation to carry out the method according to the above preferred embodiments comprises a weighing vessel for binder and a mixer, wherein said binder weighing vessel is coupled via pipes and valves with a dispersing machine and that said binder weighing vessel is coupled with a preheating furnace 1 or 29 for preheating the puffing inhibitor to the temperature of the liquid binder. In other words, the idea is

- to preheat the puffing inhibitors to the temperature of the liquid binder and

- to mix the puffing inhibitors into the binder (avoiding swimming of the inhibitor on the surface of the binder) and

- to disperse the puffing inhibitors being in the binder with a dispersing machine preferably with a shear rate of more than 1.000 [1/sec], preferably of more than 0.000 [1/sec] and with an energy input of more than 5 kWh per ton of dispersion within 10 minutes, preferably of more than 8 kWh per ton of dispersion within 10 minutes and

- to introduce the homogenized mixture of the binder and dispersed puffing inhibitors into the mixer to mix the binder with the solid carbon containing material to get the green mass for forming green carbon bodies.

According to a further preferred embodiment, the binder weighing vessel is coupled via pipes and valves with a dispersing machine (27) with a rotor stator system and said binder weighing vessel is coupled with a preheating furnace (1) for preheating the puffing inhibitor to the temperature of the liquid binder.

It is also preferred that as dispersing machine an ultrasonic device is used. It is also preferred that as dispersing machine a wet grinding mill is used.

It is also preferred that as dispersing machine a dissolver disc is used.

It is also preferred that each mixer is connected to at least two of said binder weighing vessels, said dispersing machines 10, 27 or 35 and said preheating furnaces 1 or 29. The advantage of having two of said binder weighing vessels, two of said dispersing machines and two of said preheating furnaces is not to loose mixing time, if the mixing time is lower than the dispersing time including the loading and unloading time of the binder in the weighing vessel. Preferably, if two dispersing machines are used for one mixer both dispersing machines are of identical shape to have identical conditions during dispersing.

Preferably said weighing vessel for binder is coupled with pipes and valves with a self- aspirating dispersing machine with rotor stator system 35 and said self-aspirating dispersing machine with rotor stator system is coupled with pipes and valves with a preheating furnace 29 for preheating the puffing inhibitor to a temperature of the liquid binder.

In such an installation, the process according to the present invention can be carried out by

- having the whole binder quantity, which is used for one mixer charge to mix green mass, in a balanced insulated and heatable vessel and

- having the puffing inhibitors in a preheating vessel in the right quantity for one mixer charge to mix green mass in which preheating vessel the puffing inhibitors are preheated to the temperature of the liquid binder and

- sucking the weighed and preheated puffing inhibitors into the binder using a self aspirating rotor stator dispersing machine which disperses the fine puffing inhibitors - preferably with a shear rate of more than 10.000 [1/secJ and with an energy input of more than 5 kWh per ton of dispersion within 10 minutes, more preferably of more than 8 kWh per ton of dispersion within 10 minutes - immediately during sucking it into the liquid binder while the binder is pumped from the dispersing machine itself in a loop between the self aspirating machine and the vessel which pumping homogenizes the content of the vessel and- introducing the homogenized mixture of the binder and puffing inhibitors into the mixer to mix the binder with solid carbon containing material to get green mass and using the green mass to form green carbon bodies. Description of the drawings:

An installation to carry out the method following the invention is shown in the Figures 1 to 3. In Fig. 1 is named as 1 a preheating furnace for the puffing inhibitors 2, which furnace can be for example a rotating drum furnace or a pot furnace. A pot furnace can be emptied either by shifting the furnace or by opening a bottom valve. There are two possibilities for the dosing of the puffing inhibitors: either the preheating furnace gets weighed quantities of inhibitor necessary for one mixer charge of the mixer 24 to mix the green mass and the whole quantity of the inhibitor from the preheating furnace is dosed via a pipe 3 into a vessel 6, or the inhibitor in the preheating furnace is a big quantity from which the needed quantity for one mixer charge of the mixer 24 to mix the green mass is dosed into the vessel 6 using a balance 9 of this vessel. The first mentioned alternative gives the chance to be able to create directly a mixture of different metals or metal compounds as puffing inhibitors. If the second alternative is used and a mixture of different puffing inhibitors is desired, the mixture must be created in a separate step before the preheating furnace into which the mixture is dosed. For the kind of heating energy for the preheating furnace there is no limitation, it can be heated electrically 4 or with burning 5 fossil energy like for example oil or gas. In this preheating furnace the inhibitor in a grain size of lower than 2 pm, preferably of lower than 1 pm is preheated to have the same temperature as the liquid binder has. Liquid binders like petrol pitch or coal tar pitch are commonly used at temperatures above 150 °C, in particular between 170 and 220 °C. The vessel 6 is a balanced 8 and insulated 7 and heatable 8 vessel having a bottom valve 11 and a powermotor driven dissolving disc 10 which is known from the paint industry to create extremely high shear rate in the liquid. The liquid binder is dosed via a pipe 13 having a dosing valve 2 in such a quantity into the balanced vessel 6, that with the whole quantity of inhibitor for one mixer charge to mix the green mass, the content of solid material in the mixture in the vessel 6 is of more than 50 % by mass, in particular of more than 70 % by mass. If the solid content would be less, the dissolving disc 10 would not create enough shear rate in the mixture to destroy agglomerates and the energy input would not be sufficient. Alternatively instead of a dissolver disc a wet grinding mill coupled with pipes with the weighing vessel 6 (for example a Perl mill) or an ultrasonic device can be used, both are not expressed in the drawing. Named as 15 is a vessel which is balanced 16, insulated 17 and heatable 18 and having a bottom valve 19 and a motor driven agitator 20. Into this vessel 15 the binder is dosed with a pipe 22 having a dosing valve 21 in a quantity for one mixer charge of the mixer 24 to mix the green mass lowered of the weight of the binder quantity dosed into the vessel 6 for the same mixer charge of the mixer 24. After having dosed the right binder quantity into the vessel 15 (knowing the weight due to the balance 16 of the vessel 15) the bottom valve 11 of the vessel 6 is opened and the desagglomerated dispersion being in the vessel 6 flows in a pipe 14 from vessel 6 into vessel 15 while vessel 15 is agitated with the agitator 20 to homogenize the mixture completely. The homogenized mixture of binder and inhibitor is fed to the mixer 24 with a pipe 23 by opening the bottom valve 19 of the vessel 15 in which mixer 24 solid carbon containing granular material is fed and mixed with the liquid binder to green mass for forming green carbon bodies. The vessel 6 including its installations, including the dispersing machine 10, and including the preheating furnace 1 can be installed twice if the mixing time of the mixer 24 is so fast, that one installed installation for dispersing the solid inhibitor in the liquid binder would create a loss of capacity in the mixer 24.

In Fig.2 an installation is shown wherein 1 designates a preheating furnace which can be for example a rotating drum furnace or a pot furnace. A pot furnace can be emptied either by shifting the furnace or by opening a bottom valve. There are two possibilities for the dosing of the inhibitor: either the preheating furnace gets weighed quantities of inhibitor necessary for one mixer charge of the mixer 24 to mix the green mass and the whole quantity of the inhibitor from the preheating furnace is dosed via a pipe 3 into a vessel 15 or the inhibitor in the preheating furnace is a big quantity from which the needed quantity for one mixer charge of the mixer 24 to mix the green mass is dosed into the vessel 15 using the balance 16 of this vessel 15. The first mentioned alternative gives the chance to create directly a mixture of different puffing inhibitors. If the second alternative is used and a mixture of different puffing inhibitors is desired, the mixture must be created in a separate step before the preheating furnace into which the mixture is dosed. As to the type of heating energy for the preheating furnace there is no limitation, it can be heated electrically or with burning fossil energy like for example oil or gas. In this furnace the inhibitor in a grain size of lower than 2 μπι, preferably of lower than 1 μιτι is preheated to have the same temperature as the liquid binder has. Liquid binders as petrol pitch or coal tar pitch are commonly used at temperatures above 150 °C, in particular between 170 and 220 °C. Named as 15 is a vessel which is insulated 17 and heatable 18 and has a balance 16 to know the weight of its content and two bottom valves 25 and 26 and a motor driven agitator 20. With a pipe 23 the vessel 15 is connected with an inlet of a motor driven rotor/stator dispersing machine 27, the outlet of the motor driven rotor /stator dispersing machine 27 is connected with the vessel 15 via a pipe 28 to form a loop in which the binder is pumped continuously while the high shear rate in the dispersing machine disperses the puffing inhibitors to single corns in the mixture with binder, which mixture is at the same time homogenized in the vessel 15 with the agitator 20. The homogenized mixture of binder and inhibitor is feed to the mixer 24 with the pipe 23 by opening the bottom valve 25 of the vessel 15. In the mixer 24 solid carbon containing granular material is feed and mixed with the homogenized mixture of binder and inhibitor to green mass for forming green carbon bodies. The vessel 15 including its installations and the dispersing machine 27 and the preheating furnace 1 can be installed twice if the mixing time of the mixer 24 is so fast, that one installed installation for dispersing the solid inhibitor in the liquid binder would create a loss of capacity in the mixer 24.

In Fig.3 an installation is shown with a preheating pot furnace 29 having a balance 30 to get the weight of its content and having a bottom valve 31 to empty the furnace with a pipe 32. Into this preheating furnace the puffing inhibitors 2 are dosed in the right quantity for one mixer charge to mix green mass. The heating of the puffing inhibitors is done using either electrical heating 33 or fossil energy burner 34. Liquid binder is dosed via a pipe 22 having a dosing valve 21 into a vessel 15 which is insulated 17 and heatable 18 and has a balance 16 to get the weight of its content. The quantity of binder dosed into the vessel 15 is the right quantity for one mixer charge of the mixer 24 to mix green mass. The liquid binder is pumped in a loop using a pipe 23 and a bottom valve 26 direction to a self-aspirating rotor/stator dispersing machine 35, the outlet of the self-aspirating rotor/stator dispersing machine 35 is connected with a pipe 36 with the vessel 15. While the liquid binder is pumped in the loop, the emptying valve 31 of the preheating furnace 29 is opened and the preheated inhibitor 2 having the temperature of the liquid binder is sucked from the preheating furnace with the self-aspirating dispersing machine into the liquid binder and dispersed while destroying agglomerates using high shear rate in the rotor/stator machine. In the weighing vessel 15 an agitator 20 can be used, but it is not a must to have it because the pumping effect of the self- aspirating rotor stator dispersing machine is sufficient due to the fact, that no puffing inhibitor can swim on the surface of the binder After the preheating furnace 29 is detected from its balance 30 as empty, the emptying valve 31 is closed and the liquid binder is pumped further on in the loop to homogenize the content of the vessel 15. The homogenized mixture of binder and inhibitor is fed to the mixer 24 with the pipe 23 by opening the bottom valve 25 of the vessel 15. In the mixer 24 solid carbon containing granular material is fed and mixed with the homogenized mixture of binder and inhibitor to green mass for forming green carbon bodies. The vessel 15 including its installations and the dispersing machine 35 and the preheating furnace 29 can be installed twice if the mixing time of the mixer 24 is so fast, that one installed installation for dispersing the solid inhibitor in the liquid binder would create a loss of capacity in the mixer 24. The present invention is now illustrated by the following example, to which it should not be limited.

8 g of iron oxide pigment "Bayferrox 110M" having a grain size of lower than 1 pm are dispersed 10 minutes in 200 g hot binder pitch (180 °C) using a rotor stator laboratory dispersing machine (IKA Ultra Turrax). The hot dispersion is given to a preheated (150 °C) petrol coke mixture of 1 kg containing 50 % of a coke fraction with a grain size of lower than 200 pm and 50 % of a coke fraction with a grain size between 1 and 3 mm. Mixing is carried out for 10 minutes with a planetary kneader, which vessel is heated with a gas burner to hold the temperature at about 150 °C to get a homogeneous mass. A part of the mass is transferred into a preheated (115 °C) metal shaping die of 5 cm diameter and 25 cm length, which is brought to a hydraulic press with which a stamp is pressed onto the mass with 10 tons on it. The pressure is hold till the temperature of the shaping die and the mass is lower than 50 °C. The green body is pressed out from the shaping die and baked in a laboratory furnace while being in a covered metal can having the green body in a packing media of petrol coke (grain size 1 mm). The temperature increase is 8 °C per hour till 800 °C are reached. Thereafter, heating is stopped and the furnace cools down over night. The carbon body is brought into an electrically heated argon flooded carbon tube furnace and heated up to 3000 °C for 5 hours to give a body according to the present invention.

For comparison, a sample is created by adding 14 g of a commonly used milled natural iron ore as inhibitor with a grain size of about 90 % between 10 to 40 pm to a preheated (150 °C) petrol coke mixture of 1 kg containing the same fraction as mentioned above. After adding of 200 g of hot binder pitch (180 °C) the same process was carried out as described above. Both samples have comparable values for density and specific electrical resistivity, the ash content of the first sample (following the inventive process) is 30 % lower as the ash content of the second sample.

Claims

Claims:

1. A method to produce graphitized carbon bodies from carbon containing granular material like petrol coke or coal tar pitch coke, and at least one liquid binder which can be coked at elevated temperatures, comprising at least the steps of mixing, coking and graphitizing, wherein a puffing inhibitor from the class of metals or metal compounds, preferably metal oxides, is added to the components before they are formed to green bodies, characterized in that the puffing inhibitor is used in a grain size of lower than 2 μιτι, preferably lower than 1 μιτι, and that the puffing inhibitor is dispersed in the liquid binder before the binder is mixed with the granular carbon containing material.

2. The method of claim 1 , characterized in that said puffing inhibitor is dispersed in the liquid binder after preheating to the temperature of the liquid binder.

3. The method of claims 1 or 2 characterized in that said puffing inhibitor is dispersed in the liquid binder using a shear rate in the liquid binder of more than 1000 [1/sec], preferably of more than 10.000 [1/sec] and with an energy input of more than 5 kWh per ton of dispersion within 10 minutes, preferably of more than 8 kWh per ton of dispersion within 10 minutes.

4. The method of any of claims 1 to 3, characterized in that the method comprises the steps of

- preheating the puffing inhibitors to the temperature of the liquid binder,

- combining the small quantity of the liquid binder with the big quantity,

5. An installation to carry out the method according to any of claims 1 to 4, characterized in that said binder weighing vessel 15 is coupled via pipes and valves with a dispersing machine 10, 27, 35 and that said binder weighing vessel is coupled with a preheating furnace 1 , 29 for preheating the puffing inhibitor to the temperature of the liquid binder.

6. Installation according to claim 5, characterized in that as dispersing machine a rotor/stator dispersing machine is used.

7. Installation according to claim 5 or 6, characterized in that as dispersing machine a self-aspirating rotor/stator dispersing machine is used.

8. Installation according to claim 5, characterized in that as dispersing machine an ultrasonic device is used.

9. Installation according to claim 5, characterized in that as dispersing machine a wet grinding mill is used.

10. Installation according to claim 5, characterized in that as dispersing machine a dissolver disc is used.

11. Installation according to any of claims 5 to 10, characterized in that each mixer is connected to at least two of said binder weighing vessels, said dispersing machines and said preheating furnaces.

12. A graphitized carbon body containing a puffing inhibitor, characterized in that said puffing inhibitor is present in a grain size of lower than 2 μιτι, preferably lower than 1 pm and said puffing inhibitor is distributed predominantly as single corns in the graphite body.

13. A graphitized carbon body according to claim 12, characterized in that said puffing inhibitors are distributed to more than 70 % by mass, preferably of more than 80 % by mass, most preferably than 90 % by mass as single corns in the graphite body.