Binder system, refractory block composition and process for preparing a refractory block

Abstract

The invention relates to a binder system comprising: a) from 0.1 to 5% by weight inorganic binder selected from a group of polymeric silicates and / or a group of polymeric phosphates, or b) from 0.1 to 5% by weight organic binder, wherein the concentration of said components is calculated by weight based on the binder system. The invention also relates to a refractory block composition and to a process for preparing a refractory block, said refractory block composition being for use as a lining in high-temperature furnaces and comprising: 70 to 90% by weight electrofused and / or sintered magnesium oxide, 10 to 15% by weight spinel, and 0.1 to 5% by weight zirconium sources, the composition also comprising 0.1% to 5% by weight of the binder system.

Description

BINDING SYSTEM, REFRACTORY BLOCK COMPOSITION AND REFRACTORY BLOCK PREPARATION PROCESS

[0001] The present invention relates to an organic and / or inorganic binder system that, when used in a chromium-free refractory block composition, allows the integrity of the refractory block to be maintained after heat treatment at low temperatures. Furthermore, the present invention relates to the refractory block composition and a process for preparing a refractory block. Description of the state of the art

[0002] Currently, refractory blocks used in vacuum degassing furnaces, such as RH degassers, used in the steel refining process, include a lining made of electrofused magnesium oxide and chromium oxide. These refractory bricks undergo heat treatment (firing) at high temperatures, above 1500°C, during production, before being supplied to the customer and used as linings for these furnaces.

[0003] The heat treatment stage at high temperatures, above 1500°C, is a process that requires high consumption of gases (natural and / or nitrogen) and energy expenditure, generating emissions of greenhouse gases, such as carbon dioxide, that is, it contributes to increasing the carbon footprint.

[0004] Furthermore, the element chromium, which comes from chromium oxide, one of the raw materials used in the formulations currently used in refractory linings for RH degassers, can have negative impacts on the environment and human health. If the refractory lining is not properly disposed of after the RH degasser has finished operating, the chromium, when in the Cr valence, 6+ (hexavalent), can become toxic and harmful to the environment environment.

[0005] Alternatives to these products are being developed using refractories based on magnesium oxide and carbon, magnesium oxide and chromium not burned at high temperatures, only undergoing the curing stage, and spinel, as described in the following references: - Fajardo, GL; Melo, BLB; Pagliosa, C.; Martins , GG ; Ávila, HC “EVALUATION OF UNFIRED MAGNESIA CHROME BRICKS IN RH DEGASSERS: CUSTOMER PERFORMANCE”. Proceeding 26, XLII ALAFAR Congress, Foz do Iguaçu, Brazil, - Tianbin Zhu, Yawei Lia, Shaobai Sang, Shengli Jin, Heng Wang. “Formation of hollow MgO-rich spinel whiskers in low carbon MgO-Crefractories with Al additives”. Journal of the European Ceramic Society 34 (2014) 4425–4432. - GAN Feifang; GUO Zongqi; GAO Jianying; WANG Tao; WANG Zhaohui. “Innovative Lining of Unbumt A12O3-MgO Brick” for 300t Steel Ladle in Baosteel. China's Refractories, doi:10.19691 / j.cnki.1004-4493.2021.01.003.

[0006] There are also developments aimed at completely eliminating chromium from the composition of refractory blocks for use at high temperatures, such as in furnaces. In this regard, document CN105218116 refers to refractory bricks and the preparation method for these refractory bricks, specifically relating to a type of chromium-free brick for use in RH vacuum furnaces. This refractory block comprises magnesium oxide (MgO), calcium oxide (CaO), silicon oxide (SiO) in electrofused magnesite clinker, and aluminum-rich spinel powder for electric casting.

[0007] Document W02004087609 refers to a chromium-free amorphous refractory used for lining a waste melting furnace, such as a gasification melting furnace or a smelting furnace. ash fusion. The refractory formulation described in this document includes a specific amount of yttria-based material in the main raw material, alumina, to improve the durability of the refractory as a lining for the melting furnace.

[0008] Document US5559064 describes bricks that are also chromium-free in their formulation and are resistant to corrosion, penetration, and thermal spalling. The bricks are made primarily of a magnesia material and / or an alumina-magnesia spinel material and are suitable for use as lining materials on the internal surfaces of furnaces or vessels for steelmaking, cement furnaces, and glass melting furnaces, which are directly exposed to high temperatures. In this brick's formulation, titanium oxide and aluminum oxide are primarily used as matrix additives to accelerate reactions that occur at high temperatures for firing. In other words, although chromium has been removed from the formulation described in this document, the brick's heat treatment is still carried out at high temperatures.

[0009] Furthermore, the article "GUO, Zongqi et al. Bonding phase formation in eco-friendly periclase-spinel-Al bricks used in RH degassing process. Journal of the European Ceramic Society, v. 43, n. 6, p. 2663-2674, 2023" describes the formation of the bonding phase in bricks made of chromium-free periclase-spinel-aluminum used in the RH degassing process. The composition of this brick comprises metallic aluminum and carbon-based organic binders, and the heat treatment applied to this brick is not carried out at high temperatures.

[0010] Another important study is in the article “MANDAL et al. Designing environment-friendly chromium-free Spinel-Periclase-Zirconia refractories for Ruhrstahl Heraeus degasser. J Am Ceram Soc. 2020;00:l-20.”, which refers to refractory blocks for furnaces of the type RH degasser, whose composition does not contain chromium, but rather a combination of components that provide this refractory with corrosion resistance from contact with furnace slag and low crack propagation. However, this document does not specify the use of low temperatures in the heat treatment stage of the blocks, which leads us to assume that, although chromium is not used, the study does use high temperatures to cure the refractory blocks. Objectives of the invention

[0011] Thus, the present invention aims to provide an organic and / or inorganic binding system to be applied in a refractory block composition allowing the integrity of the refractory block to be maintained after it undergoes heat treatment at low temperatures, so that the refractory block has sufficient resistance to maintain its integrity during transportation and even its application as a lining for furnaces that work at high temperatures, such as, for example, an RH degasser.

[0012] Another objective of this invention is to provide a refractory block composition, free of chromium and with high corrosion resistance when in contact with slag during its application as a lining of an RH degasser.

[0013] It is also an objective of this invention to provide a process for preparing a chromium-free refractory block, comprising the heat treatment step carried out at low temperatures in order to obtain a refractory block cured in stages with low carbon dioxide emissions, and which is capable of maintaining its integrity until these refractory blocks are applied as lining of an RH degasser. Brief description of the invention

[0014] The present invention has as its object a binding system, comprising: a) from 0.1 to 5% by weight of inorganic binder selected from a group of polymeric silicates and / or a group of polymeric phosphates; or b) from 0.1 to 5% by weight of organic binder; wherein the concentration of said components is calculated based on the binder system by weight.

[0015] Also an object of this invention is a refractory block composition for use as a lining in high temperature furnaces, comprising 70 to 90% by weight of electrofused and / or sintered magnesium oxide; 10 to 15% by weight of spinel; 0.1 to 5% by weight of zirconium sources; the composition further comprising 0.1% to 5% by weight of the binder system.

[0016] Another object of the present invention is a process for preparing a refractory block, comprising: (a) Portioning of raw materials containing defined particle sizes, forming raw material particles; (b) Addition and mixing of a binding system to the raw material particulates resulting in a mixture; (c) Compaction of the mixture in pre-defined molds by means of pressing resulting in a plurality of pre-cured refractory blocks; and (d) Heat treatment of the plurality of pre-cured refractory blocks at temperatures between 150°C and 600°C resulting in cured refractory blocks. Brief description of the drawings

[0017] Figures 1a and 1b illustrate cross sections of a sample of burnt refractory block and Magnesia-Chromium 1 base subjected to lance corrosion test;

[0018] Figures 2a and 2b - illustrate cross sections of a sample of a burnt refractory block and the Magnesia-Chromium 2 base subjected to the lance corrosion test;

[0019] Figures 3a and 3b - illustrate cross-sections of a sample of the cured refractory block, object of the present invention, subjected to the lance corrosion test;

[0020] Figures 4a and 4b - are graphs illustrating the wear results of the test specimens of the burned refractory blocks 1 and 2 and of the cured refractory block, object of the present invention, when after corrosion test by slag F2 and C2, respectively, in a rotary kiln;

[0021] Figures 5a, 5b and 5c - illustrate the results of thermodynamic simulations performed in the FactSage 8.0 software considering the composition of the refractory in contact with the F2 slag under conditions similar to the slag test; and

[0022] Figures 6a, 6b and 6c - illustrate the results of thermodynamic simulations performed in the FactSage 8.0 software considering the composition of the refractory in contact with the C2 slag under conditions similar to the slag test; and

[0023] Figure 7 - is a schematic flowchart of the process of preparing a chromium-free refractory block, which is the object of the present invention. Detailed description of the invention

[0024] The present invention has as its object a binder system comprising from 0.1 to 5% by weight of inorganic binders selected from a group of polymeric silicates and / or from a group of polymeric phosphates; or from 0.1 to 5% by weight of organic binder; the concentration of said components being calculated based on the system binder by weight.

[0025] More specifically, the inorganic binder preferably consists of polymeric sodium or potassium silicates and / or polymeric sodium, aluminum or magnesium phosphates.

[0026] Inorganic binders are used as binders or deflocculants. Their function is to hold together the raw material particles contained in the refractory block composition, in addition to providing mechanical and chemical resistance and thermal stability to the refractory blocks, ensuring their integrity and strength after production and until they are assembled as furnace linings, especially RH degassing furnaces. Furthermore, inorganic binders enable a more sustainable refractory block, as they do not require high-temperature heat treatment before application in RH degassers.

[0027] The inorganic binders in the polymeric silicate group promote an increase in the degree of crosslinking of the refractory block matrix at temperatures between 150°C and 600°C by binding to the raw material particulates in the block's composition. At the same time, network-forming substances replace the network-modifying alkali ions to achieve chemical resistance. Thus, they allow the refractory block to maintain its integrity and strength during transport and until it is assembled as a furnace lining, after undergoing a low-temperature heat treatment step during its manufacturing process, as will be described in more detail below.

[0028] The inorganic binders of the polymeric phosphate group undergo additional bonding when subjected to temperatures in the range of 150°C and 600°C due to the bonding of the polymeric phosphates with the raw material particles of the composition of the refractory blocks, due to the formation of orthophosphate structures. When the refractory block This binder system is used as a lining for furnaces operating at high temperatures. The phosphate bond remains stable at relatively low temperatures, at least between 150°C and 600°C. As the temperature increases until it reaches its maximum during the operation of RH degassers, several phenomena occur with the raw materials present in the formulation. These phenomena include sintering, which promotes the agglutination of the refractory material's atoms; the formation of new phases through reactions and interactions between the particles of this refractory material, such as filling the material's porosity, forming strong bonds between these particles, called ceramic bonds, and creating a protective layer on the refractory blocks.

[0029] Organic binders are also used as binders or deflocculators as alternatives to inorganic binders or in addition to them. Organic binders consist of resin-based compounds such as Novolac resin, which is widely used as a binder in magnesium oxide-based refractory bricks because it provides the product with good mechanical strength properties.

[0030] The organic binder is thermosetting and improves green mechanical strength—the strength of the pre-cured refractory block (when it has not yet undergone the heat treatment stage)—and thermal shock resistance, while reducing porosity levels. Furthermore, it induces minimal emissions of polycyclic aromatic hydrocarbons and other toxic substances during pyrolysis during the heat treatment stage of the refractory blocks, providing greater environmental health benefits.

[0031] Furthermore, the degree of hardening of the organic binder can be controlled by the amount of hardener added, a hexamine type hardener. Normally, The amount of hexamine added is approximately 10% in relation to the liquid resin for it to harden completely.

[0032] During the heat treatment of refractory blocks, when blocks containing this organic binder are subjected to temperatures between 150°C and 600°C, the organic binder molecules react with each other, forming large, branched molecules that are joined by covalent bonds, creating a complex three-dimensional molecular network that holds the raw material particles in the refractory block together. Thus, this organic binder also allows the refractory block to undergo a low-temperature heat treatment stage while still maintaining its integrity and strength until it is assembled as a lining in furnaces.

[0033] Inorganic binders are in powder form and are mixed with the other components of the composition, as described below, and finally, all are mixed with water. The organic binder is in liquid form and is added to the coarse aggregates—that is, raw materials with particle sizes between 8.0 mm and 0.5 mm—before the addition of the fine aggregates that make up the refractory block's raw material particles.

[0034] Thus, it is understood that the function of the binding system is to enable the refractory blocks to be formed with a heat treatment stage at low temperatures, between 150°C and 600°C, which are already sufficient to activate this binding system so that, with this, the refractory blocks can maintain their integrity and resistance during handling, transportation and installation in furnaces.

[0035] The present invention also has as its object a refractory block composition for use as a lining in high temperature furnaces that is free of the element chromium in its composition. Thus, this refractory block composition, which is the object of the present invention, comprises: 70 to 90% by weight of electrofused and / or sintered magnesium oxide; 10 to 15% by weight of spinel; 0.1 to 5% by weight of zirconium sources; and 0.1 to 5% by weight of the binder system as described above.

[0036] Electrofused and / or sintered magnesium oxide is present in the composition in particle sizes smaller than 8.00 mm. This component, together with spinel, provides greater resistance to thermal shock in the refractory block due to the difference in their coefficients of thermal expansion. This difference generates microcracks between the grains during cooling, aiding in the release of thermal stress and disrupting the microstructure, hindering crack propagation.

[0037] Spinel is present in particle sizes smaller than 3.00 mm and, as described above, together with electrofused and / or sintered magnesium oxide, it has the function of providing greater resistance to thermal shock of the refractory block.

[0038] Zirconium sources come from the zirconium oxide and / or calcium zirconate group, or even from the zirconite group. They are present in particle sizes smaller than 3.00 mm and function to reduce the penetration of iron oxide (FeO) into the refractory block by reacting with calcium oxide (CaO) in the slag from the RH degasser furnace, making the slag more viscous and less fluid, making it more difficult to penetrate the refractory block structure. This creates a "slag barrier," making it difficult for the slag to react with and erode the refractory block.

[0039] The binding system, with the characteristics already described above, is present in the refractory block composition in a range of 0.1 to 5% and has the function of agglutinating the grains of the elements in this composition, hardening the refractory block during the heat treatment stage, as will be seen below, and also ensuring the resistance and maintenance of the integrity of this refractory block before the sintering reactions that will form the ceramic phases when the refractory block is exposed to high temperatures during its use.

[0040] The present invention also has as its object a process for preparing a refractory block, as illustrated in figure 7, which comprises the following main steps: (a) Portioning of raw materials containing defined particle sizes, forming raw material particles; (b) Addition and mixing of a binding system to the raw material particulates resulting in a mixture; (c) Compaction of the mixture in pre-defined molds by means of pressing resulting in a plurality of pre-cured refractory blocks; and (d) Heat treatment of the plurality of pre-cured refractory blocks at temperatures between 150°C and 600°C resulting in cured refractory blocks.

[0041] Step (a), the portioning of the raw materials, consists of combining the electrofused and / or sintered magnesium oxide, the spinel and the zirconium sources in the granulometries defined and described above, in order to form the raw material particulates containing the coarse and fine particulates.

[0042] The binding system is added to the raw material particles in quantities ranging from 0.1 to 5%. The binding system may comprise powdered inorganic binder or liquid organic binder. as detailed previously. Thus, the raw material particles and the binding system are mixed in a conventional mixer until the most homogeneous mixture possible is obtained. This mixture is then compacted, using presses, into molds with the desired shape for the refractory blocks.

[0043] Once the mixture is compacted in a plurality of molds, pre-cured molded refractory blocks are obtained. Due to the presence of the binding system in the composition of these plurality of pre-cured refractory blocks, the heat treatment step of these pre-cured refractory blocks can be performed at low temperatures, that is, at temperatures between 150°C and 600°C, which are substantially lower than the heat treatment steps for these types of refractory blocks known in the prior art. Thus, the pre-cured molded refractory blocks undergo the heat treatment step to remove possible volatiles from the organic binders and to activate the binding system and harden the pre-cured refractory blocks.

[0044] More specifically, the heat treatment stage involves heating the pre-cured refractory blocks at a rate of between 40°C and 60°C per hour until reaching a temperature range of between 150°C and 600°C. The pre-cured refractory blocks remain in this temperature range for between 6 and 18 hours, depending on factors such as the gas permeability of the pre-cured refractory blocks, the size and quantity of the pre-cured refractory blocks, the positioning conditions in the oven, the circulation of heated air in the oven, among others.

[0045] Once the desired characteristics are achieved, the cooling stage of the heat treatment begins, at a cooling rate between 10°C and -50°C per hour. At the end of this stage, cured refractory blocks are obtained with the binding system activated so that remain intact during packaging, transportation, and even during the assembly of these blocks on the furnace walls. Additionally, when assembled in the furnaces and subjected to high temperatures, the atoms of the refractory material or new phases coalesce, with reactions and interactions between the particles of this refractory material forming strong bonds between these particles, called ceramic bonds, and creating a protective layer on the refractory blocks against corrosion due to contact with the slag formed inside the furnace, with which the refractory blocks have intense and prolonged contact.

[0046] In order to evaluate the performance of the cured refractory blocks obtained from the composition and process, objects of the present invention, and to understand certain behaviors after use, some corrosion tests were carried out to try to simulate the conditions in which the cured refractory blocks will be exposed during application in the field, that is, during their application as lining in furnaces that work at high temperatures and with slag.

[0047] In this case, two corrosion tests were conducted to simulate the extreme conditions to which the refractory block may be exposed during its application as a lining for an RH degassing furnace: 1) Spear Corrosion Test

[0048] The first test, conducted at the Shinagawa Research Center in Japan, involves passing oxygen gas through a steel lance to generate a very aggressive slag composed of iron oxide (FeO), due to the reaction ' ^2 * e which occurs at high temperatures (~2000°C). The lance remains in contact with the face of the refractory block or brick to be evaluated for 30 seconds so that, after cooling, the depth and volume of the wear caused can be determined.

[0049] For the test, two bricks identified as 1 were used and 2, fired and made with magnesia-chrome as a reference for comparison, with the first applied to areas of greater RH wear and the second to areas of lesser wear. The cured brick, identified here as 3, is the cured, chromium-free refractory block that has the composition subject to the present invention, with the characteristics described above and prepared by the refractory block preparation process, also subject to this invention.

[0050] The results of the lance test showed that the cured, chromium-free refractory block presented greater resistance to corrosion by iron oxide (FeO) slag, whose average wear volume was 10.7 cm 3 against 13.6cm 3 and 13.9cm 3 of burnt bricks 1 and 2, respectively.

[0051] Figures 1a, 2a, and 3a illustrate the contact region with the oxygen lance of bricks 1, 2, and 3, respectively, after the test. Figures 1b, 2b, and 3b illustrate the cross-sections of bricks 1, 2, and 3, respectively, evaluated in the test, showing the difference in wear between the pieces. Furthermore, the fired bricks of samples 1 and 2, as illustrated in Figures 1a, 1b, 2a, and 2b, presented cracks, further indicating low mechanical and thermal shock resistance when compared to the cured brick or cured refractory block of the present invention, illustrated in Figures 3a and 3b. 2) Rotary Kiln Corrosion Test

[0052] The second test, conducted at the Shinagawa Brazil Technical Department Laboratory, consists of internally lining a rotary kiln with the refractory brick samples to be studied and, with the aid of a blowtorch that emits a flow of gas rich in oxygen and natural gas, maintaining the internal temperature at around 1620°C±30°C, allowing the slag that will be in contact with the refractory block under study to melt.

[0053] As the RH Degasser type furnace contains different refining stages, including oxygen blowing and aluminum (Al) addition, among others, the slag composition undergoes changes throughout the cycle.

[0054] Thus, with the aim of trying to simulate the operating conditions, two synthetic slags were formulated whose chemical compositions are described in table 1 below, Table 1 - Chemical composition of synthetic slags used in rotary kiln corrosion testing.

[0055] The graphs in figures 4a and 4b illustrate the comparative wear results between the fired bricks and the cured refractory block of the present invention, when exposed to the two slags F2 and C2 respectively, in the rotary kiln test.

[0056] In this case, as can be seen in figures 4a and 4b, despite the result of relative wear (%) to corrosion by slag F2 having indicated a higher value for the cured refractory block of the present invention, -70% more wear when compared to the reference burnt bricks, the cured refractory block object of the present invention presented greater resistance to corrosion by slag C2 rich in aluminum oxide (A12O3) and calcium oxide (CaO).

[0057] Furthermore, to understand the phenomena that may occur During the corrosion process, simulations were carried out using thermodynamic calculations with the aim of predicting the behavior and interaction between the materials of the refractory blocks and the environment in which they are in contact.

[0058] For these simulations, FactSage 8.0 software was used, which, by minimizing Gibbs free energy, calculates equilibrium and estimates the possible final products in a reaction. Thus, the graphs illustrated in Figures 5a, 5b, 5c, 6a, 6b, and 6c indicate the simulation of the percentage formation of phases at different temperatures that the rotary kiln corrosion test can reach. Using the Equilib module and the Ftoxid and FactPS databases, assuming a pressure of 1 atm in an oxidizing atmosphere, simulations were performed for both the fired bricks of samples 1 and 2 containing chromium and for the cured brick or cured refractory block of the present invention (chromium-free), when in contact with the slags F2 and C2 containing the compositions shown in Table 1. 1) Slag F2

[0059] When evaluating the graphs illustrated in Figures 5a, 5b, and 5c, with the simulation of the % of phases formed throughout the operating temperatures of the F2 slag corrosion test in the rotary kiln, it is possible to notice a difference in the amount of CaCr2O4 alpha and beta phases in fired bricks 1 and 2, in which fired brick 1 presents a greater amount of them when compared to fired brick 2. According to Róg et al. (2007), calcium chromium (III) oxide CaCr2O4 is an important component of ceramic materials applied at high temperatures. Therefore, we can predict a greater corrosion resistance of brick 1 when compared to 2, as observed in the practical results.

[0060] Moving on to the evaluation of the cured brick simulation or cured refractory block of the present invention, we note that the amount of the MgO-periclase solid phase is greater than in both fired bricks 1 and 2, which justifies the corrosion resistance of the cured refractory block being relatively high, despite not presenting precipitation of phases containing chromium in its composition.

[0061] Furthermore, in all three bricks, the solid phase Ca2A12SiO7 precipitates at all temperatures analyzed, indicating that the reaction between the refractory brick and the slag, rather than forming a liquid phase, produces a solid phase, preventing the slag from further penetrating the microstructure of the bricks, explaining the low absolute wear value in the samples. Since the amount of precipitation of this phase in the cured refractory block of the present invention was lower than that observed in the fired bricks of samples 1 and 2, we can infer that the cured refractory block has lower resistance to corrosion by the slag evaluated, as shown in the practical results. 2) C2 slag

[0062] When comparing the simulations of the phases formed during the corrosion test by slag C2 illustrated in the graphs of figures 6a, 6b and 6c, it is possible to note a greater concentration and stability of the MgO-periclase phase in the cured brick or cured refractory block of the present invention than in the burnt bricks of samples 1 and 2, which may indicate the maintenance of the structure of the cured refractory block, whose majority composition is composed of magnesium oxide (MgO).

[0063] Furthermore, at lower temperatures, there was precipitation of the solid CaA12O4 phase, indicating that the reaction between the cured refractory block and the slag, in addition to not giving rise to a liquid phase, allowed the formation of a solid phase, increasing the viscosity of the slag and preventing the continuation of corrosion to the interior of the structure of the cured refractory brick or block of the present invention, while the fired bricks of samples 1 and 2 present a lower amount of precipitation of this phase, which increases only at higher temperatures. Thus, we can justify the high resistance to corrosion by the C2 slag of the cured refractory brick or block of the present invention.

[0064] In simulations considering the composition of the cured brick, the solid phase CaZrO3 also formed, indicating the reaction of the zirconium sources with the calcium present in the slag. Thus, we can infer that as this reaction occurs during the operation of the RH degasser, the cured refractory block subject to the present invention will be more resistant to a CaO-rich slag, as indicated in the rotary kiln corrosion test using C2 slag.

[0065] Thus, the cured refractory block, obtained from the composition and process that are objects of the present invention, is free of the chromium element, however, it comprises the binding system that allows this refractory block to be obtained with a heat treatment step at low temperatures and, when in use, achieves a corrosion and crack resistance performance similar and / or superior to bricks or blocks fired at high temperatures and containing chromium in their composition, which are known in the state of the art and currently applied in RH furnace linings.

[0066] Having described a preferred embodiment example, it should be understood that the scope of this object encompasses other possible variations, being limited only by the content of the appended claims, including possible equivalents.

Claims

CLAIMS 1. Binder system for refractory block, characterized by the fact that it comprises: a) from 0.1 to 5% by weight of inorganic binder selected from a group of polymeric silicates and / or from a group of polymeric phosphates; or b) from 0.1 to 5% by weight of organic binder; in which the concentration of said components is calculated based on the binder system by weight.

2. Binder system according to claim 1, characterized in that the inorganic binder preferably consists of polymeric sodium or potassium silicates and / or polymeric aluminum, sodium or magnesium phosphates used as binders or deflocculants.

3. Binder system, according to claim 1 or 2, characterized by the fact that the polymeric silicates promote an increase in the degree of crosslinking of a matrix of the refractory block at a temperature in the range of 150°C and 600°C and bind to particulates of the raw material of the refractory block.

4. Binding system, according to claim 1 or 2, characterized by the fact that the polymeric phosphates undergo an additional bond with the raw material particulates of the refractory block when subjected to temperatures in the range of 150°C and 600°C due to the formation of orthophosphate structures.

5. Binder system, according to claim 1, characterized by the fact that the organic binder is preferably composed of a resin and about 10% by weight of a hardener, being used as a binder or deflocculant.

6. Binder system according to claim 1 or 5, characterized by the fact that when subjected to temperatures in the range of 150°C and 600°C, molecules of the organic binder react with each other, forming large branched molecules that are joined by covalent bonds and creating a three-dimensional molecular network uniting particles of raw material from the refractory blocks.

7. Composition of refractory block for use as lining in high temperature furnaces, comprising 70 to 90% by weight of electrofused and / or sintered magnesium oxide; 10 to 15% by weight of spinel; 0.1 to 5% by weight of zirconium sources; the composition being characterized by the fact that it further comprises from 0.1% to 5% by weight of the binder system as defined in claims 1 to 3.

8. Composition according to claim 7, characterized in that it is free of chromium.

9. Composition, according to claim 7, characterized by the fact that the electrofused and / or sintered magnesium oxide is present in the form of grains with particle sizes of less than 8.00 mm, the spinel is present in the form of grains with particle sizes of less than 3.00 mm and the zirconium sources are present in the form of grains with particle sizes of less than 3.00 mm.

10. Composition according to any one of claims 7 to 9, characterized in that the binder system binds the electrofused and / or sintered magnesium oxide grains, the spinel grains and the zirconium source grains and hardens the refractory block.

11. Composition according to any one of claims 7 to 10, characterized in that when subjected to At temperatures above 1,500°C inside a furnace, atoms clump together and sintering reactions occur, forming ceramic bonds with reduced porosity and the creation of a protective layer on the refractory blocks.

12. Process of preparing a refractory block, characterized by the fact that it comprises: (a) Portioning of raw materials containing defined particle sizes, forming raw material particles; (b) Addition and mixing of a binding system to the raw material particulates resulting in a mixture; (c) Compaction of the mixture in pre-defined molds by means of pressing resulting in a plurality of pre-cured refractory blocks; and (d) Heat treatment of the plurality of pre-cured refractory blocks at temperatures between 150°C and 600°C resulting in cured refractory blocks.

13. Process, according to claim 12, characterized by the fact that in step (b) the binder system can comprise the powdered inorganic binder or the liquid organic binder or a mixture of the two.

14. Process, according to claim 12, characterized by the fact that the heat treatment of the plurality of pre-cured refractory blocks is carried out at a heating rate between 40°C and 60°C per hour until reaching a temperature level between 150°C and 600°C, remaining at this level for between 6 hours and 18 hours followed by cooling at a temperature rate between -10°C and -50°C per hour.

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