METHOD FOR PRODUCE CARBON-BOUND REFRIGERANT FORMED BODY AND REFRIGERANT FORMED BODY

Description

TECHNICAL FIELD OF INVENTION

[0001] The invention relates to a method for producing carbon-bonded refractory products with improved thermal shock properties, the refractories obtained thereby, and the use of low molecular weight carbohydrates as binders in the production of the refractories. BACKGROUND OF THE INVENTION

[0002] Carbon-bonded refractory products are widely used as linings in metallurgical vessels, such as magnesia bricks in converters, or as key components like dip runners, slide plates, plugs, or casting channels in continuous casting. Carbon-bonded refractory products are also used in blast furnaces, in transport vessels such as ladles, in the chemical industry, in the waste incineration industry as temperature-resistant pipes, and in the cement industry as lining material.

[0003] Binders include, for example, synthetic resins, preferably phenolic resins (resoles or novolacs), as well as coal- or petroleum-derived binders. Synthetic resins offer the advantage of being processable at room temperature, while coal- and petroleum-derived binders require a hot mixing process. Synthetic resin binders form an isotropic carbon network through annealing followed by coking. This isotropic binder network is susceptible to oxidation, which is why carbon in the form of carbon black or graphite is usually included in the formulation. In addition to oxidation resistance, the addition of carbon also improves slag resistance.

[0004] WO 2011 / 093020 A1 describes a coating composition for a refractory material. This may contain a thermosetting resin such as phenolic resin, saccharides, and a thermoplastic resin. This document also mentions graphite, coke, and pitch as further components; the use of a thermosetting resin as a carbon carrier is mandatory. WO 94 / 10102 A1 describes a dry binder for refractory mixtures containing a sugar that may be selected from mono-, di-, and trisaccharides.

[0005] In DE 199 54 893 A1, graphitic structures are generated in situ below 1,000 °C by adding catalytically active additives from the group of readily reducible transition element compounds, in particular metallocenes, metallobenzoates, or metallonaphthenates of copper, chromium, nickel, or iron. High-melting-point carbonaceous powder resins (CARBORES®) with a coking residue of over 80% according to DIN 51905 and benzo[a]pyrene contents of less than 500 mg / kg according to EN 1014-3 (benzo[a]pyrene = BaP) are also added to phenolic resins to create bonding graphitic structures.

[0006] Resin-based binders require a crosslinking agent for hardening. The most common agent is hexamethylenetetramine. In addition to free phenol from the phenolic resin, crosslinking and coking release formaldehyde, ammonia, and other volatile substances. Formaldehyde is classified as carcinogenic.

[0007] Coal-derived binders form graphitic structures during coking, which are significantly more oxidation-stable than cross-linked structures. However, due to their polycyclic aromatic hydrocarbon (PAH) content, these binders are also classified as carcinogenic. A hot mixing process is necessary for their application. Only with the introduction of EP 1 704 128 A1 is a binder system provided that utilizes a powdered, graphitable coal tar pitch with a benzo(a)pyrene content of less than 500 mg / kg and a coking residue of at least 80 wt.% according to DIN 51905, and a room-temperature liquid graphitable binder with a coking residue of at least 15 wt.% and a benzo[a]pyrene content of less than 500 mg / kg according to EN 1014-3, thus permitting a cold mixing process. The binder, which is liquid at room temperature, contributes a small amount to the coke structure and thus also acts as a permanent binder.It acts, at least partially, as a temporary binder until coking occurs. The use of coal tar pitch, which is solid at room temperature, as a binder in a refractory mixture is also described in Ceramics International 39 (2013) 6695-6703. US 2010 / 319578 A1 describes a binder for refractory mixtures containing pitch and an anthracene oil to liquefy the pitch. Furthermore, the binder may contain another component such as a dextrin. SUMMARY OF THE INVENTION

[0008] The invention is based on the technical problem of finding a label-free temporary binder that, in combination with a graphitable binder, can be cold-processed in a mixer and yet forms an anisotropic coke structure. Shaping is to be achieved using conventional compaction methods and, for higher-quality products, by pressing. Furthermore, the replacement of conventional solvents with aqueous systems would be advantageous.

[0009] This problem is solved by a process for producing a carbon-bonded refractory product in which refractory raw materials (dry materials) are mixed with a binder using a cold-mix process, formed into a molded body, and the molded body is subjected to coking before or during its use as a refractory product. The binder contains coal tar or petropite pitch and a low-molecular-weight carbohydrate with up to six monosaccharide units or a molecular weight of up to 1,000 Da. The coal tar pitch contains less than 500 mg / kg benzo[a]pyrene with a coking residue according to DIN 51905 of at least 80 wt.%, and the petropite contains less than 300 mg / kg benzo[a]pyrene with a coking residue according to DIN 51905 of at least 70 wt.%. The binder according to the invention is free of thermosetting resins.Consequently, a carbohydrate or a mixture of carbohydrates possessing adhesive properties is used as a temporary binder that does not require labeling.

[0010] The petroleum pitch used as a binder component according to the invention preferably has a melting point (DIN 51920) of 245°C to 270°C. The coking residue (DIN 51921) of the petroleum pitch is preferably 68 wt.% to 78 wt.%. The benzo[a]pyrene content of the petroleum pitch used according to the invention is preferably less than 50 ppm.

[0011] The temporary binders used according to the invention are free of impurities that catalytically promote their combustion. The advantage of the refractory product obtained according to the invention compared to refractory products produced with the binder system of EP 1 704 128 B1 is that the workplace and environmental compatibility of the binder has been further increased.

[0012] The invention further relates to a refractory molded body obtained according to the inventive method and to the use of carbohydrates as a binder in the production of refractory products. The refractory molded body according to the invention exhibits a different pore size distribution, measured by mercury intrusion, compared to molded bodies produced analogously with resin as a binder. In particular, the refractory molded body according to the invention is characterized by one or more of the following characteristics: 30 vol% of the pore volume from pores with a pore diameter greater than 1.0 µm, in particular 1.3 µm, 50 vol% of the pore volume from pores with a pore diameter greater than 500 nm or 70 vol% of the pore volume from pores with a pore diameter greater than 200 nm.

[0013] The effects achieved according to the invention are surprising. The binders used are individually known as binders. However, the replacement of the resin system in the combination "resin system with the coal tar pitch according to claim 1" by a low-molecular-weight sugar is surprising to those skilled in the art. This is not self-evident and not readily comprehensible because (a) the resin system typically provides higher carbon content, lower porosity, and, in particular, smaller pore sizes after coking. Those skilled in the art would never consider weakening their system for functional components or key components such as plugs, dip spouts, or valve plates, since these components would significantly impair operation in a steel mill in the event of failure due to the higher porosity, larger pore sizes, and, in terms of the lower carbon content, weaker bonding due to the low-molecular-weight sugars.The failure of a plunger can not only lead to a power unit failure but is also life-threatening for the workers on site.

[0014] Surprisingly, it is only the interaction of low-molecular-weight sugar and the coal tar pitch used according to the invention that leads to a new binder system which, despite the generation of larger pores after coking, exhibits very good performance in laboratory and industrial applications. This is due to the fact that (a) CARBORES® melts at approximately 236°C and penetrates the pores that also form when the water dries from the low-molecular-weight sugar, thus compensating for the weaknesses of the temporary binder even at temperatures below 300°C. Furthermore, the already achieved and required high strengths, necessary for such key components and which could never be achieved with the exclusive use of saccharides, result in significantly more thermal shock-tolerant materials with larger pore sizes, which is of particular importance for the gating phase during use.This behavior, as well as the high strength level with this pore size distribution, is surprising to those skilled in the art. The pore formation in the dry sugar skeleton structure and the penetration of the synthetic pitch prior to coking are significant for this thermomechanical behavior after coking and during use. DETAILED DESCRIPTION OF THE INVENTION

[0015] The product of the process according to the invention can be an uncoked molded body after forming. This molded body can be used as a component, for example for lining purposes, and coked by thermal treatment before its first use. In this case, the coking therefore takes place at the point of application of the refractory mixture. However, the product of the process according to the invention can also be the coked refractory molded body that has been post-processed to its final dimensions.

[0016] The binder system used according to the invention preferably comprises a powdered, graphitable coal tar pitch, preferably with a benzo(a)pyrene content of less than 500 mg / kg according to EN 1014-3 and a coking residue of at least about 80 wt.% according to DIN 51905 as a so-called permanent binder. The production of such a powdered, graphitable coal tar pitch with a benzo(a)pyrene content of less than 500 mg / kg is described, for example, in EP 0 510 315 B1, and the pitch itself is known and commercially available under the trademark CARBORES®.

[0017] The amount of pitch used as a binder, based on the mass of the dry materials, can be, for example, 2 to 20 wt.%, preferably 3 to 8 wt.%.

[0018] The binder used according to the invention also contains a temporary binder. According to the invention, a temporary binder is understood to be a binder that decomposes during coking but contributes significantly to the stickiness required for cold mixing and shaping, and to the strength of the uncoked product required for transport purposes after shaping.

[0019] The dry materials of a refractory mixture do not include the binders and additives of the refractory mixture. The amount of carbohydrate used as a temporary binder according to the invention, based on the mass of the dry materials, can be, for example, 3 to 15 wt.% anhydrous, preferably 5 to 10 wt.% anhydrous.

[0020] Suitable temporary binders according to the invention are low-molecular-weight carbohydrates that can be present in an aqueous mixture and / or as an aqueous solution and that exhibit a sticky or adhesive effect, comprising up to six monosaccharide units or a molecular weight of up to 1,000 Da, preferably up to 500 Da. Particularly suitable saccharides are therefore mono-, di-, and oligosaccharides with up to six monosaccharide units, as well as mixtures thereof. The carbohydrates can be added to the dry matter in the form of a syrup.

[0021] Suitable temporary binders include glucose, fructose, sorbitol, mannose, xylose, arabinose, and galactose. Suitable disaccharides include maltose, sucrose, cellobiose, and lactose. Suitable oligosaccharides are dextrins, raffinoses, oligofructoses, and combinations thereof.

[0022] The binder according to the invention is free of thermosetting (thermoset) synthetic resins such as those commonly used as binders in refractory products. The binder according to the invention can therefore preferably consist essentially of a temporary low-molecular-weight carbohydrate adhesive and a high-melting-point coal tar and / or petroleum pitch.

[0023] The term cold mixing is usually understood by the relevant expert to mean the mixing of the dry materials, binders and additives of a refractory mixture at a temperature of ambient temperature up to 50 °C.

[0024] For highly concentrated carbohydrate solutions, it is more economical to moderately increase the mixing temperature when mixing the dry ingredients, binders, and additives to reduce the viscosity of the carbohydrate solution than to lower the viscosity by diluting it with water. Removing the water would then be more energy-intensive.

[0025] Binders containing hydroxyl groups, such as phenolic resins, typically contain 10% w / w crosslinking agents, usually hexamethylenetetramine. Surprisingly, it has been found that with carbohydrates, the amount of crosslinking agent can be significantly reduced or even omitted entirely. This further reduces emissions during the process and, due to reduced gas formation, decreases porosity and increases the density of the coked material.

[0026] In addition to the aforementioned binders, additional carbon carriers can be added to the refractory mixture. These can be selected from graphite, carbon black, coke, graphene, carbon fibers and / or carbon nanotubes (CNTs).

[0027] Refractory raw materials are dry materials commonly used in refractory mixtures. The particle sizes used can be oxide, non-oxide, natural or synthetic, carbon, or metallic. These refractory raw materials range in size from 30 nm to 30 mm. They include fine- and coarse-grained materials, with or without added carbon. Fine-grained raw materials are defined as natural or synthetic materials with a particle size of up to 100 µm. Coarse-grained raw materials are defined as natural or synthetic materials with a particle size greater than 100 µm.

[0028] Examples of oxide aggregates that can be used include calcium oxide, magnesium oxide, dolomite, chromium oxide, aluminum oxide, mullite, zirconium mullite, zirconium dioxide, magnesium aluminate spinel, bauxite, yttrium oxide, titanium dioxide or combinations of these substances.

[0029] Silicon carbide, silicon nitride, boron nitride, boron carbide and carbon can be used as non-oxide granules in the dry material.

[0030] To achieve high strengths after thermal shock and for oxygen protection, an additional 0.05 to 20 wt.% of finely powdered silicon-based metals or alloys, based on the mass of the dry materials, can be added.

[0031] Furthermore, 0.05 to 10 wt.%, based on the mass of the dry materials, of finely ground flux selected from sodium and potassium water glass, various frits, boron trioxide, sodium tetraborate (borax), boric acid, feldspar and mixtures of these materials may be added.

[0032] Also, 0.05 to 20 wt% fine silicon dioxide, fused silica, quartz glass, silica and their mixtures, each based on the mass of the dry materials, can be added.

[0033] To optimize the oxidation resistance of the binder system according to the invention, further fine-grained additives such as Al, Si, Mg, Fe or carbides, such as SiC, B₄C, TiC, or nitrides, such as Si₃N₄, AlN, TiN, or borides such as BN or TiB₂, can be added to the dry materials. The amount of this additive can be 0.05 to 10 wt.%, based on the mass of the dry materials.

[0034] Surfactants can increase the affinity of the aqueous carbohydrate for the solid components of the mass. Their proportion can range from 0.01 to 1 wt%, based on the mass of the dry materials. Furthermore, additives can be used that form a self-glaze at temperatures within the liquid steel and are therefore capable of healing any stress cracks that may develop.

[0035] According to the invention, for example, 0.05 to 5 wt% alkylene glycols such as ethylene glycol can be added as a shaping aid during the preparation of the mass in a mixer. According to the invention, the addition of titanium dioxide to the mass can increase the thermomechanical properties of the carbon-bonded refractory molded parts and masses. Release agents such as magnesium stearate can be used to improve the flowability of the granules after the granulation process.

[0036] The binder system used according to the invention, in combination with a refractory dry material mixture, is particularly suitable for shaping refractory masses by extrusion, pressing, and especially for uniaxial and cold isostatic pressing.

[0037] After shaping, the components are coked at a temperature of 400 °C to 1,600 °C in a reducing atmosphere, for example, an argon or nitrogen atmosphere. Alternatively, coking can also take place directly at the point of use before the first application as a refractory material.

[0038] According to one embodiment of the inventive method, a thermal treatment can be carried out after coking at a temperature of 800 °C to 1,600 °C and, for example, with a heating rate of 10 K / min to 40 K / min in an air atmosphere. This thermal heat treatment can also take place when heating refractory components or refractory linings in metallurgical units directly before application to minimize thermal stresses.

[0039] The refractory components can be coated with an external glaze and thus protected against oxygen. According to an embodiment of the invention based on WO 2011 / 020832 A1, carbon-bonded refractory products can be obtained by adding silicon and borax. After oxidative thermal treatment following coking, these products exhibit a glazed surface, a so-called self-glaze. This provides additional protection against oxygen attack on the carbon of the refractory component at high operating temperatures.

[0040] Figure 1 shows a photograph of coked refractory components (molded bodies) produced according to the inventive method.

[0041] Figure 2 displays the geometry and dimensions of a component made of Figure 1 .

[0042] Figure 3compares the pore size distributions of the refractory molded bodies produced according to the invention (Example 1 Recipe 1-7) with those of analogously produced but resin-bonded molded bodies (Example 1 Recipe 8).

[0043] Surprisingly, when determining the pore size distribution using mercury porosimetry according to DIN 66133 from June 1993, it was found that the primary pore sizes (pore diameters) in the molded parts produced according to the invention are significantly larger when coked at the component's service temperature than the pores in an analogous production process using a resin as a binder. A comparison of the pore size distribution is shown in the example formulations. This reveals the potential of the new carbon-bonded material based on the new binder system. The combination of coal tar or petropite and a carbohydrate with special additives results in a microstructure that tolerates larger pores while maintaining similar strengths. This allows crack propagation to be mitigated with a higher probability at the larger pores. Those skilled in the art consider this a contribution to the system's increased thermal shock resistance.

[0044] The following examples (manufacturing and application examples and testing examples) serve to further explain the invention. EXAMPLES Example 1 Recipes 1-8 - Production of refractory components

[0045] Plug components are manufactured according to Figure 1 produced using the binder according to the invention based on Al 2 O 3 -C materials.

[0046] After weighing the dry materials according to Table 1 below, the mixing process takes place in two stages in an Eirich intensive mixer (300 rpm): (I) Mixing for two minutes, manually agitating the mixture, (II) Mixing for five minutes. The dry material mixture is granulated by adding the liquid binder. The liquid binder is added in three stages, with mixing lasting five minutes in each stage. The mixture is then granulated three times for five minutes each. Depending on the example formulation, the wetting agent Gypsperse® XL3 (a water-soluble salt of naphthalenesulfonic acids condensed with formaldehyde) and / or the additive titanium dioxide are added to the liquid binder and then added to the dry material mixture. After granulation is complete, the release agent magnesium stearate is added to the mixture and mixed in within two minutes.

[0047] The shaping process takes place after a 48-hour storage period (soaking) by cold isostatic pressing at pressing pressures of 100 MPa. The green bodies are then coked in a reducing atmosphere (coke bed) at a heating rate of 3 K / min and a holding time of five hours at 1400 °C.

[0048] Table 1 presents the example formulations 1 to 7 and the comparative formulation 8 according to the invention. The analytical data for the examples and the comparative formulation are shown in Table 2. The raw materials, such as aluminum oxide and graphite, are used in commercially available fractions. According to the invention, binders and additives are added during the mixing process. Table 1: Inventive formulations Components 1 2 3 4 5 6 7 8 % by weight % by weight % by weight % by weight % by weight % by weight % by weight % by weight Drying agents Aluminum oxide 70 70 70 70 70 70 70 72 graphite 20 20 20 20 20 20 20 20 silicon 4 4 4 4 7 4 4 4 silicon dioxide 4 4 4 4 4 4 4 4 Sodium tetraborate 2 2 2 2 2 2 2 - Fastener CARBORES ®< P 4 6 4 4 4 4 4 - liquid binder Aqueous. Fructose syrup (70%) 8-9 8-9 7-8 7-8 7-8 - - - aqueous. Invert sugar syrup (72%) - - - - - 8-9 7-8 - Phenolic resin (Momentive PF 7280 FL 01) - - - - - - - 10 Harder Hexamethylenetetramine (Hexa) 0,3 0,3 0,3 - - 0,3 0,3 1 Release aids Mg stearate 0,5 0,5 0,5 0,5 0,5 0,5 0,5 0,5 Pressing aids Zusoplast - - - - - - - 1 wetting agent Gypsperse ®< XL3 0,1 - - 0,1 - 0,1 - - Additive titanium dioxide - - 0,7 - 0,7 - 0,7 - Table 2: Analytical data of the formulations according to the invention 1 2 3 4 5 6 7 8 Open porosity according to DIN EN 993-1 in [%] 20,5 20,6 18,3 21,1 18,5 19,4 18,9 21,1 Cold bending strength according to DIN EN 993-6 in [MPa] 9,0 10,2 10,2 5,1 9,2 8,7 11,6 3,9 Bulk density according to DIN EN 993-1 in [g / cm³< ] 2,6 2,4 2,5 2,6 2,5 2,5 2,5 2,5 Pore ​​size analysis according to DIN 66133 in [µm] 30% by volume 2,1 3,0 3,2 2,1 2,4 1,6 2,0 0,6 50% by volume 1,0 1,8 1,9 1,1 1,1 0,7 1,1 0,2 70% by volume 0,5 0,8 1,1 0,6 0,5 0,3 0,6 0,1

[0049] The sum of the dry materials listed in Table 1 equals 100%, as is standard practice in the refractory industry. All percentage values ​​for binders and additives refer to the mass of the dry materials.

[0050] A comparison of the pore size analysis of the refractory components 1 to 7 according to the invention with a component produced analogously using resin as a binder shows that, for the same relative pore volume, the pore size of the refractory components 1 to 7 according to the invention is shifted to higher values ​​compared to the resin-bonded system 8. 30% of the pore volume of the refractory components 1 to 7 according to the invention has a pore diameter of 1.6–3.2 µm, whereas a pore diameter of 0.6 µm was found in the phenol-resin-bonded system 8. At 50% and 70% of the pore volume of the refractory bodies 1 to 7 according to the invention, pore diameters of 0.7-1.9 µm and 0.28-1.05 µm respectively were found, which are larger than the comparable measured values ​​of 0.2 µm and 0.1 µm respectively of the phenol resin-bonded system 8. Example 2 - Immersion tests with the plugs of recipes 1 and 3 in an industrial steel melt.

[0051] The molded parts are immersed in a steel bath under near-industrial conditions. The molten steel has a temperature of 1,700 °C and is covered with an acidic slag. The immersion process is carried out twice for two minutes each time, with a five-minute cooling phase at room temperature in between. After the two thermal shock cycles without preheating, the molded parts exhibit high residual strength (Table 3). Table 3: Thermal shock stress on the molded bodies of formulations 1 and 3 Example recipe KBF [MPa] before KBF to [MPa] Δ [MPa] [MPa] [%] 1 9,0 5,5 -38,9 3 10,2 9,8 -3,9

[0052] The table shows the values ​​of the cold bending strength (CBF) according to DIN EN 993-6 before and after thermal shock treatment.

[0053] Comparative tests in industrial steelmaking with a resin binder based on phenolic resin instead of fructose have shown strength losses of 40 to 60% after thermal shock stress, and thus similar (example recipe 1) and / or higher strength losses than with example recipe 3. Example 3 - Changing the steel composition through immersion tests

[0054] The effects of immersion treatment with refractory components produced according to the invention on a steel composition were investigated. For this purpose, the refractory components were immersed in a molten steel, as described above. Subsequently, the concentration of certain substances listed in Table 4 in the molten steel was determined and compared with the concentrations of these substances determined before immersion. The steel compositions before and after six 15-minute immersion cycles are shown in Table 3. Table 4: Steel composition according to immersion tests in wt.% C Si Mn P S Cr previously 0,203 0,377 0,768 0,011 0,009 0,136 afterward 0,210 0,373 0,736 0,012 0,008 0,149 Ni Mon Cu Al Co V previously 0,080 0,028 0,058 0,004 0,008 0,007 afterward 0,081 0,028 0,058 0,002 0,008 0,007

[0055] The results in Table 4 show that repeated immersion of a refractory body in the molten steel does not result in any impurities. This also supports the good bonding effect of the binder system used according to the invention.

[0056] Computed tomographic images of the test specimens obtained according to the invention (recipes 1 and 3) showed a structure free of cracks larger than 50 µm after immersion tests.

Claims

1. Method for preparing a carbon-bonded refractory product, in which refractory raw materials are mixed with a binder in a cold mixing process, transferred into a shaped body and the shaped body is subjected to coking before or during use as a refractory product, characterized in that the binder contains coal tar pitch or petropitch and has a low-molecular-weight carbohydrate with up to six monosaccharide units or a molecular weight of up to 1,000 Da and is free from a thermosetting resin, and the coal tar pitch has less than 500 mg / kg benzo[a]pyrene with a coking residue according to DIN 51905 of at least 80% and the petropitch has less than 300 mg / kg benzo[a]pyrene with a coking residue according to DIN 51905 of at least 70 wt.%.

2. Method according to claim 1, characterized in that the coal tar pitch contains less than 300 mg / kg benzo[a]pyrene and the petropitch contains less than 100 mg / kg benzo[a]pyrene.

3. Method according to claim 1, characterized in that the carbohydrate is present in an aqueous mixture or in an aqueous solution.

4. Method according to claim 1, characterized in that the carbohydrate is selected from mono-, di- and / or oligosaccharides.

5. Method according to claim 4, characterized in that the carbohydrate is selected from trioses, tetroses, pentoses and hexoses.

6. Method according to claim 5, characterized in that the carbohydrate is selected from glucose, fructose, sorbitol, mannose, xylose, arabinose, galactose and mixtures thereof and / or is selected from maltose, sucrose, cellobiose, lactose and mixtures thereof as well as from mixtures of carbohydrates from both of the aforementioned lists.

7. Method according to any of claims 1 to 6, characterized in that as functional additives in grain sizes smaller than 100 µm such as Al, Mg, Si, Fe, B or oxides such as SiO2, TiO2, B2O3 or borax or carbides such as SiC, B4C, TiC or nitrides such as Si3N4, AIN, TiN or borides such as BN, TiB2 are added.

8. Method according to any of claims 1 to 7, characterized in that for partial crosslinking of the carbohydrates, 0 to 50 wt.% of the amount of a crosslinking agent, in particular hexamethylenetetramine, that is customary for crosslinking phenolic resins is added.

9. Refractory shaped body obtainable by a method according to claims 1 to 8 having one or more drying agents selected from oxidic grains, non-oxidic grains, metal grains, mixtures thereof, and a binder that contains coal tar pitch or petropitch and a low-molecular-weight carbohydrate with up to six monosaccharide units or a molecular weight of up to 1,000 Da and is free from a thermosetting resin, with the coal tar pitch and the petropitch being as defined in claim 1, characterized in that the material, after coking to operating temperature, has a pore volume distribution, measured by mercury intrusion according to DIN 66133 of June 1993, with the following characteristic values: - 30 vol.% of the pore volume consists of pores with a pore diameter greater than 1 µm, - 50 vol.% of the pore volume consists of pores with a pore diameter greater than 500 nm and - 70 vol.% of the pore volume consists of pores with a pore diameter greater than 200 nm, the particle size of the dry substances being 30 nm to 30 mm, the coal tar or petroleum based binder being used in an amount of 2 to 20 wt.%, based on the mass of the dry matter.