Refractory covering particle composition

Abstract

The present invention relates to a refractory covering particle composition. The refractory covering particle composition comprises from 0.5 to 10% by weight of calcium titanate, AI2O3 and MgO. The calcium titanate phase, present in the form of CaTiO3, reacts with AI2O3 to form complex calcium aluminates and / or hibonite-type phases during sintering / heat treatment in the presence of MgO. The particle composition is characterised in that the refractory covering after sintering is more resistant to slag penetration and has an increased modulus of rupture.

Description

[0001] COMPOSITION OF REFRACTORY COATING PARTICLES

[0002] FIELD OF THE INVENTION

[0003] The present invention relates generally to a refractory lining particle composition. More particularly, the present invention relates to a composition of a monolithic refractory particulate mixture for a metallurgical furnace lining, comprising a calcium and titanium oxide additive, such that post-sintering of the refractory lining provides improved resistance to slag penetration and increased mechanical strength.

[0004] BACKGROUND

[0005] Refractories are materials with properties that make them suitable for use in high-temperature applications. Unshaped refractory materials have the ability to form seamless linings and are often referred to as monolithic. These materials are used, for example, as linings for cupola hearths and siphons, blast furnaces, main, secondary, and inclined runners, and more generally for bowls or bowl spouts, ladles, tundishes, reaction chambers, and chutes that contain, direct the flow of, or are suitable for facilitating the industrial processing of liquid metals and slags, or any other high-temperature liquids, solids, or gases.

[0006] In general, the basic refractories available so far are magnesium oxide, commonly referred to as "magnesite." This magnesite usually takes the form of calcined magnesite (MgCCh), although electrically sintered magnesite is sometimes used. Typically, "magnesite" refractory material containing at least 80% MgO is prepared in granular form and then processed, alone or with other materials, to form furnace linings, such as bottoms, walls, orifices, etc., or to form bricks, crucibles, or other magnesite articles.

[0007] In particular, alumina-magnesia spinel is commonly used to form refractory linings, as it offers advantages in terms of lining performance and service life. A further improvement results from the ability of alumina-magnesia spinels to trap iron oxides, silicon oxide, manganese oxide, and other alkalis present in the slag within their crystal lattice, thus effectively preventing slag penetration into the lining and reducing wear through the chemical reaction between the refractory and the slag. Typically, refractory materials comprise or consist of relatively large and medium-sized grains and a finer-grained matrix that functions as a binder and largely determines the characteristics of the composite.

[0008] The decisive performance factors that determine the use of refractory particles or materials are in particular good resistance to corrosion by liquid metals and slags, as well as high thermal shock resistance, thermal fatigue resistance and modulus of rupture, abrasion resistance when loading heavy scrap and resistance to penetration by metals / slags at high temperatures.

[0009] When a magnesite-based refractory material is used for the formation of basic open-hearth steelmaking furnace bottoms, it is normally mixed with a large amount of slag, which binds the magnesite grains, but makes the lining less refractory and less basic. In addition, the time required to line the bottom of a furnace with a magnesite-slag composition is excessively long. When magnesite is used in lining the walls or orifices of a furnace, it is customary to provide some type of binder for the magnesite grains. Sometimes electrically sintered magnesite grains are mixed with a finely ground, moist slurry of the same material, which serves as a binder.However, although a kiln wall structure thus formed tends to become extremely hard on the inner surface thereof due to the heat of the kiln, the underlying material, being subjected to a lower degree of heat, tends to lose its cohesion due to dehydration. As a result, the material disintegrates and the shell-like structure that remains is generally unsuitable for the purposes of any kiln.

[0010] Another disadvantage of a magnesite-based brick / refractory material in the current state of the art is that it is extremely brittle before firing or requires the use of an external binder that is detrimental to the refractoriness. Such a refractory material also exhibits weakness between ordinary temperatures and the temperatures at which it is fired in the kiln. This requires an expensive firing process, since the brick cannot be stacked and must be surrounded with silica brick that carries the load. Magnesite crucibles generally made from electrically sintered magnesite also suffer from disadvantages, as these crucibles exhibit poor thermal shock resistance.

[0011] Generally, for an induction furnace, a dry vibration tamper or a monolith is used as a wear lining, and they are preferred over bricks. In addition, recently, an alumina / aluminum-magnesium spinel composite refractory has been used in an induction furnace as a wear refractory solution due to the chemical inertness of the alumina grains and the thermal shock resistance of the spinel structure. A silica tamper is usually used as a low-cost solution as an induction furnace wear lining refractory. US 2005 / 255986 A1 discloses monolithic refractory compositions used in furnace linings and describes a spray mix comprising 4.2 wt% organic binders in addition to alumina with different particle sizes and magnesia.

[0012] Patent application CN111995409 A teaches the addition of 3-5 wt% calcium carbonate and 3-5 wt% titanium oxide into a magnesium-aluminum spinel reclaimed material. This document also teaches that low material cost, energy saving, environmental protection, high fire resistance, high mechanical strength and high volume stability are achieved. In addition, the document also teaches that with the introduction of calcium carbonate and titanium dioxide into the matrix (magnesium-aluminum spinel reclaimed material), calcium titanate is formed at high temperature, which improves the contact degree between calcium aluminate grains and increases the mechanical strength. In addition, titanium dioxide can improve the sintering performance of the magnesium-aluminum spinel reclaimed material and improve the density of the material.Boric acid is also added at 1-1.5%. This document is more concerned with a magnesium-aluminum spinel-based reclaimed material and the improvement of certain properties of the reclaimed material for reuse as a refractory material in an induction furnace. This document is not concerned with an alumina / magnesium-aluminum spinel composite refractory. Publication US 2010 / 0062386A1 teaches a composition containing magnesium orthotitanate and calcium titanate suitable for use in rotary kilns for the production of Portland cement or lime.

[0013] An alumina / aluminum-magnesium spinel composite refractory is known to perform better than a silica tamping compound. Alumina-magnesia products are more than ten times more expensive than a silica tamping compound. Even though the performance of alumina-magnesia is better than that of silica, to make a greater value proposition in terms of cost, the performance of existing alumina-magnesia materials needs to be improved. Therefore, there is a need to improve the performance-to-cost ratio of alumina-magnesia refractories still need to improve.

[0014] It is also known that refractory erosion occurs due to slag attack on the refractory. The penetration of molten metal and slag into the refractory weakens the refractory structure, resulting in the dissolution of the refractory into the molten metal. A refractory undergoes thermal shock, and as a result of thermal shock, micro- / macro-cracks are created inside the sintered refractory structure. These cracks allow the penetration of metal and slag and result in erosion. It is established that better resistance to slag penetration and thermal shock will generally improve the life of the refractory.

[0015] It is very important to design the content of corundum and spinel (alumina-magnesia spinel) phases of the refractory for optimum properties such as thermal shock resistance and slag penetration resistance.

[0016] The spinel structure provides thermal shock resistance and corrosion resistance. The corundum phase, consisting of larger alumina grains, provides chemical inertness against slag and metal attack. The density of the sintered structure also plays an important role in penetration, as well as thermal cracking. If the density is increased, the porosity is decreased, improving resistance to slag penetration. An increased spinel content in the matrix will improve thermal stability, leading to less cracking. Excess spinel content will also produce more expansion, amplifying cracking. Therefore, achieving an optimal spinel content in the matrix is ​​imperative to balance thermal stability and corrosion resistance.

[0017] It is very difficult to improve thermal shock resistance and slag penetration resistance without changing the spinel content and increasing the density. There is no simple solution to this problem in the current state of the art.

[0018] The inventors of the present application have discovered a solution to this problem by influencing the refractory structure during sintering. It is essential to note that a modification of the sintered structure can lead to deterioration of properties if the changes are not beneficial.

[0019] Therefore, it is necessary to find refractory coatings based on alumina-magnesia spinel with improved resistance to thermal shocks, measurable in particular via the modulus of rupture, and corrosion resistance, measurable in particular via the resistance to slag penetration.

[0020] The inventors of the present application have established that they have achieved an optimal balance of spinel and at the same time improved the slag penetration resistance and the modulus of rupture of the alumina / spinel alumina-magnesia composite refractory by adding calcium titanate in the form of a compound and not manufacturing calcium titanate in situ at higher temperature.

[0021] SUBJECT OF THE INVENTION

[0022] The object of the present invention is to provide a composition of refractory lining particles, in particular a refractory lining which after sintering is resistant to slag penetration and has increased mechanical strength.

[0023] Another object of the present invention is to provide a refractory lining particle composition (or particulate composition) that ensures an optimal aluminum-magnesium spinel content in the matrix that is fundamental to balance thermal stability and corrosion resistance. Yet another object of the present invention is to provide a method for manufacturing a refractory lining particle composition, which specifically contemplates a mixture in which a calcium titanate phase, preferably present in the form of CaTiO, reacts with AI2O3 to form complex calcium aluminates including a hibonite phase at the grain boundaries during sintering / heat treatment in the presence of MgO. The refractory lining is particularly intended for use in an alumina-magnesia spinel-based furnace refractory.

[0024] Furthermore, another object of the present application is to provide a method for preparing a refractory coating particle composition.

[0025] SUMMARY OF THE INVENTION

[0026] In one aspect, the present invention relates to a refractory lining particle. The refractory lining particle composition comprises from 0.1%, preferably from 0.5% to 10%, preferably to 5%, by weight of calcium titanate, the calcium titanate phase preferably present in the form of CaTiO, reacting with AI2O3 to form calcium aluminates including a hibonite phase, in particular phases such as CA or CA2 or CA6 or CAI 2 or CAI 7 or complex aluminates containing Mg / Al / Ca / Ti, during sintering in the presence of MgO. The refractory lining after sintering is resistant to slag penetration and has an increased modulus of rupture.

[0027] According to the invention, AI2O3, MgO and calcium titanate are present in said composition in proportions allowing the formation of a hibonite phase during the sintering of said particulate composition.

[0028] In another aspect, the present invention relates to a method for preparing a refractory lining composition. The method comprises the following steps: a) obtaining alumina-magnesia matrix precursors preferably in the form of fine particles of alumina and magnesia, in addition to grains, preferably grains of alumina and / or magnesia; b) preferably adding a binder to said matrix precursors; c) adding calcium titanate (CaTiO,) to the preceding refractory mixture and mixing manually or by means of mixing equipment. The refractory lining after sintering is resistant to slag penetration by at least 5% and has an increased modulus of rupture of at least 10%, compared to a refractory lining without CaTiO,.

[0029] Other features of the present invention will be described in detail in conjunction with the accompanying drawings and specific embodiments, but do not limit the present invention.

[0030] DEFINITIONS:

[0031] The following description, in combination with the figures, is provided to facilitate understanding of the teachings described herein. The following discussion focuses on specific implementations and embodiments of the teachings. The discussion is provided to facilitate description of the teachings and should not be construed as limiting the scope or applicability of the teachings.

[0032] It should be noted that not all of the activities described in the general description or examples are necessary, that part of a specific activity may not be necessary, and that one or more other activities may be performed in addition to those described. Furthermore, the order in which the activities are listed is not necessarily the order in which they are performed.

[0033] The specification and illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The specification and illustrations are not intended to serve as an exhaustive and complete description of all elements and features of systems that utilize the structures or methods described herein. Certain features, which for clarity are described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that, for brevity, are described in the context of a single embodiment may also be provided separately or in a subcombination. In addition, reference to values ​​indicated by a range includes all values ​​within that range.Furthermore, it will be understood that no limitation on the scope of the disclosure is thereby intended, the changes and other modifications in the composition, system, product and process described, and other applications of the principles of the disclosure herein, being contemplated as they would normally appear to a person skilled in the art for which the disclosure is intended.

[0034] As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having," or any other variation thereof, are intended to cover non-exclusive inclusion. For example, a method, article, or apparatus that includes a list of features is not necessarily limited to only those features, but may include other features not expressly stated or inherent in such method, article, or apparatus. Furthermore, unless expressly stated otherwise, "or" refers to an inclusive or and not an exclusive or.

[0035] The use of "a" or "an" is employed to describe elements and components illustrated herein. This is merely for convenience, and to give a general sense of the scope of the invention. This description should be read as including one or at least one and the singular also includes the plural, or vice versa, unless another meaning is clearly apparent.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which the invention is directed. The materials, methods, and examples are merely illustrative and not intended to be limiting. To the extent that certain details regarding specific materials and processing operations are not described, such details may include conventional approaches, which may be found in reference works and other sources within the manufacturing trades.

[0037] Throughout this specification, a reference to "an embodiment," "certain embodiments," "an alternative embodiment," or similar language means that a particular feature or structure described as part of the embodiment is included in at least one embodiment of the present disclosure. Thus, occurrences of these phrases throughout this specification may all refer to the same embodiment, but need not.

[0038] As used herein, the term "refractory lining" is very well known to a person skilled in the art and refers to a layer behind the wear lining in contact with the contents of the furnace. The term "refractory lining" may be used interchangeably with "refractory lining material", which refers to a material that resists decomposition by heat, pressure or chemical attack, and retains its mechanical strength and shape at high temperatures, and also serves as a thermal barrier between a hot medium, for example a molten metal, and the wall of a vessel or furnace serving as a container. The chemical composition, in particular the oxide content, is measured after calcination of the particle mixture, i.e. after water and organic binders or additives have been removed. Conventionally, the chemical composition is measured by a person skilled in the art after calcination at at least 750°C in air after half an hour.

[0039] As used herein, the term "particulate composition or particulate refractory lining composition" refers to a mixture of refractory particles or materials that form a refractory lining for an induction furnace.

[0040] As used herein, the term "sintering" refers to a process of transforming fine bulk particles into a homogeneous solid mass by applying a high temperature treatment, between 1100 and 1800°C.

[0041] As used herein, the term "hibonite-based phase" or "hibonite phase" or "hibonite phases" refers to a refractory phase, which is a complex aluminate phase comprising the elements Al / Mg / Ca / Ti in different specific proportions, a typical chemical composition of which is generally designated as Ca(Al,Ti,Mg)i20i9.

[0042] As used herein, the term "spinel" refers to magnesium / aluminum aggregates having the general formula MgAbCh in the cubic crystal system. In all embodiments, the term "spinel" covers all other phrases formed with "Mg / Al oxide system".

[0043] As used herein, the term "alumina-magnesia matrix" refers to a matrix that binds the grains after sintering of the refractory lining particle. It may contain a majority of AI2O3. A matrix precursor is in the form of fine particles, preferably with a size less than 0.1 mm, which react during sintering to form at least one phase that binds the grains after sintering of the refractory lining particle. The alumina phase refers to a phase consisting essentially of AI2O3, preferably greater than 90% by weight. The magnesia phase refers to a phase consisting essentially of MgO, preferably greater than 90% by weight.

[0044] The calcium titanate phase is not necessarily limited to the CaTiCh form alone, which is the preferred stable form. Other forms such as CaTi2Os, Ca-iT Oio, Ca3Ti2O?, CaTi2C>4 may be used according to the present invention.

[0045] According to the present invention, a binder may be added to the particle composition to form aggregates of particles in the composition, the aggregates comprising a core formed of second metal oxide particles and having a coating comprising first metal oxide particles, and also adhering said particles by liquid / solid phases which are different from said first or second metal oxides.

[0046] DETAILED DESCRIPTION

[0047] The main aspect of the present invention relates to a particulate refractory lining composition. The particulate refractory lining composition according to the present invention comprises from 0.1% to 10%, preferably at least 0.5%, preferably at least 1%, preferably at most 7%, preferably at most 5%, or even less than 3%, by weight of calcium titanate. The inventors of the present application have surprisingly discovered that the calcium titanate phase preferably present in the form of CaTiO, when reacted with AI2O3 to form a hibonite phase and complex calcium aluminates at the ALCh grain boundaries during sintering / heat treatment in the presence of MgO, produces a refractory lining which after sintering is much more resistant to slag penetration and has an increased modulus of rupture.Furthermore, the refractory lining after sintering is advantageously resistant to slag penetration of at least 5% and has an increased mechanical strength of at least 10%, compared to a refractory lining without hibonite phase.

[0048] In one embodiment, the particulate refractory lining composition comprises 60-95 wt% ALOs, preferably 30-50%, having a particle size of 1 mm or greater; more preferably, 30-60%, having a particle size of 0.1 mm or greater. AI2O3 is present in the form of grains and fines of various sizes. In one embodiment, the alumina grain size is in the range of 0.01-16 mm. In another embodiment, the alumina fines size is in the range of 1-250 µm. In one embodiment of the present invention, 30-65 wt% of the particulate composition comprises particles having a particle size of 1 mm or greater. In another embodiment, 40 to 85% by weight of the particulate composition comprises particles having a particle size of 0.5 mm or greater.In another embodiment, 60 to 95% by weight of the particulate composition comprises particles having a particle size of 0.045 mm or greater.

[0049] The balance consists of a binder, in particular a mineral binder, at least a portion of the particles consisting of first particles of metal oxide selected from AI2O3, MgO, SiO? or all of these oxides and having a particle diameter of 0.075 mm or less, which are present in the particulate composition in the form of a coating of second particles of metal oxide selected from AI2O3, MgO, SiO2, CaO, TiO2 having a particle diameter of 0.075 mm or more.

[0050] The particle composition according to the present invention comprises 0 to 40% by weight of MgO, preferably 3 to 30%, having a particle size of 0.5 mm or greater; more preferably, 30 to 95%, having a particle size of 0.01 mm or greater. The MgO is present in the form of grains and fines of various sizes. In one embodiment, the size of the magnesia grains is in the range of 0.1 to 12 mm. In a preferred embodiment, the size of the magnesia grains is 0.5 to 1 mm. In another embodiment, the size of the magnesia fines is in the range of 30 to 1000 µm. In a preferred embodiment, the size of the magnesia fines is less than 500 µm.

[0051] The presence of fine particles of MgO and / or AI2O3 also brings the particles into close contact before spinel formation occurs, thus promoting the spinel formation reaction upon heating. This results in improved efficiency of the heating / sintering step in the formation of the final alumina-magnesia refractory product in the case of coarse AI2O3 particles surrounded or coated by fine particles of AI2O3 and MgO with a binder.

[0052] The refractory lining particle composition further comprises 0 to 20% by weight of binder. In a preferred embodiment, the binder is present at 1 to 10%. The binder according to the present invention is selected from the group consisting of SiO2, MgO, CaO, AI2O3, P2O5, TiO2 or a combination thereof, preferably from a metal oxide selected from SiO2, MgO, CaO, AI2O3, P2O5 Na2O, TiCh or a combination thereof. In a preferred embodiment, the binder is MgO. In another embodiment, the binder is a combination of MgO, SiCh, CaO, Na2O and TiO2, preferably MgO, SiO2, CaO and TiO2. Preferably the binder is a metal oxide selected from SiO2, CaO, Na2O, P2O5 or a combination thereof. In a preferred embodiment, the binder particle size is less than 0.1 mm.

[0053] According to one aspect of the present invention, the AbOs particles present in the particle composition are white fused alumina (WF A) particles and aggregates.

[0054] According to another aspect of the present invention, the refractory lining particle composition may also comprise a mineralizer, the mineralizer particles being selected from the group consisting of B2O3, V2O5, TiO2, Y2O3, Fe2O3, CaO, NaCl, AICI3, MgCl, LiF, ZnF2, BaF2, CaF2 or a combination thereof.

[0055] In one embodiment of the present invention, the refractory lining particle composition may also comprise one or more desiccants, for example, anhydrous magnesium sulfate (MgSO4), boron oxide (B2O3), amorphous silica gel (SiO2), xanthan gum, acrylic or methacrylic acids, two-component polymerization binders, mixtures of boric acid and phosphate.

[0056] In an illustrative embodiment of the present invention, the sintered microstructure of alumina-magnesia refractories is modified without hindering the spinellization reaction at a similar density of 2.5-3 g / cm 3. This modification surprisingly improved the slag penetration resistance as well as the modulus of rupture at room temperature. In a specific embodiment, according to the present invention, calcium titanate is added inside an alumina-magnesia mixture to modify the microstructure. Such addition of calcium titanate according to the present invention is less than 8 wt%. In a preferred embodiment, the calcium titanate is added in the range of 2 to 5 wt%. The calcium titanate added according to the present invention modifies after sintering the microstructure, thus providing improved properties. According to one aspect of the present invention, calcium titanate reacts with alumina at a temperature above 1300 °C to form complex calcium aluminates such as CA or CA2 or CA12 or CA17 or CA6 and / or a hibonite phase.

[0057] In a preferred embodiment of the present invention, the addition of calcium titanate is in the form of a compound and not by manufacturing calcium titanate in situ at higher temperature. In particular, the calcium titanate is provided in the form of a powder with a median diameter of less than 500 micrometers, preferably less than 250 micrometers, preferably less than 150 micrometers, preferably less than 100 micrometers. Therefore, the present invention makes it possible to obtain a spinel forming an alumina / spinel alumina-magnesia composite refractory lining particle, and not a preformed spinel-based refractory material. In an alternative embodiment, calcium titanate as an additive can be used for a refractory containing a preformed spinel.

[0058] According to one aspect of the present invention, the mass content of SiCh and / or Na2O of the particulate composition is less than 5%, preferably less than 3%.

[0059] According to one aspect of the present invention, the chemical reaction due to the addition of calcium titanate changes the composition of the phase at the grain boundaries, which in turn causes a reduction in slag attack. Calcium aluminates tend to saturate the slag at the micrometer level in the grain boundary region, which again tends to increase the viscosity, and therefore further penetration is stopped. Specifically, the reaction with the slag also forms different complex phases in the grain boundary regions, which act as a barrier layer against further slag penetration.

[0060] According to the present invention, after sintering at a temperature of 1600°C for about 3 hours, MgO and AI2O3 react to form an aluminum-magnesium spinel MgAbCh. Phase quantification studies by XRD clearly showed that the refractory coating particulate composition forming the alumina / aluminum-magnesium spinel composite comprises 30-40 wt% magnesium-aluminum spinel and 45-55 wt% corundum phase.

[0061] According to the present invention, when 2% calcium titanate is added, after sintering at 1600°C for 3 hours, XRD phase quantification studies have shown that the particulate refractory lining composition forming the alumina / aluminum-magnesium spinel composite comprises 30-40% by weight of magnesium-aluminum spinel. The corundum phase content is reduced because the alumina grains have started to react with the calcium and titanium oxide to form a hibonite phase. In one embodiment, about 16% hibonite has thus formed as a result of the reaction and about 40% corundum phase has been measured.

[0062] The inventors also found that elemental microstructure mapping showed that calcium and titanium were present in the alumina grain boundary region. The calcium and titanium had formed a kind of ring structure around the alumina grains, which is one of the most significant microstructural changes that improve the modulus of rupture and resistance to slag penetration.

[0063] In all embodiments according to the present invention, the alumina phase is present at less than 95% by weight, in the form of corundum AI2O3, and the magnesia phase is present at less than 40% by weight, in the form of periclase MgO, before sintering or reaction takes place. In another embodiment, the alumina and magnesia phases are present at less than 80% by weight, in the form of a combined aggregate containing an aluminum-magnesium spinel MgAbCh, after sintering.

[0064] In addition, the alumina and sodium phases are present at less than 10% by weight, in the form of a combined aggregate containing diaoyudaoite AlnNaOn, after sintering. The alumina, magnesium and sodium phases are present at less than 10% by weight, in the form of a combined aggregate containing a sodium-magnesium-aluminum oxide AhoMg4Na2050, after sintering.

[0065] In one embodiment, the refractory particle composition also contains impurities in a total amount of less than 3% by weight, based on the total weight of the refractory composition. Impurities in the refractory particle composition of the present invention include SiCh, P2O5, K2O, Na2O, ZnO, Q12O, FeO / Fe2O3.

[0066] It was surprisingly found that the refractory lining according to the present invention exhibits a resistance to slag penetration depth of up to 27%. Slag penetration was observed at 8 mm for a refractory matrix with an addition of 2 wt% calcium titanate which forms a ring-like morphology around the larger alumina grains with complex calcium aluminates / titanates. Comparatively, a slag penetration depth of 11 mm was observed for a refractory lining without hibonite and complex calcium aluminates / titanates around the larger alumina grains. The slag penetration depth is limited to 10,000 μm in a refractory wall with a thickness of 25,000 μm.In addition, the refractory lining exhibits an increase in modulus of rupture of up to 150% compared to a refractory lining without hibonite phase, and the modulus of rupture is in the range of 5 to 150 kg / cm. 2 , evaluated by means of a UTM machine with the three-point bending method. Furthermore, more advantageously, the refractory lining according to the present invention can withstand high temperatures, up to 1800 °C.

[0067] The slag composition against which the refractory lining exhibits resistance according to the present invention is an acidic slag with a B2 basicity of less than 1 including more than 10% MnO and more than 20% FeO / Fe2O3. At 1600°C for a residence time of 3 hours, the ratio of slag to refractory is 1:2 minimum. In all embodiments of the present invention, for the same slag-refractory reaction conditions, an addition of excess slag will cause greater penetration. If the slag is more acidic, it will induce a greater reaction, MnO will cause greater penetration. In a cup slag corrosion test, when 14 g of crushed slag is used, by making a hole in the refractory cup, where the slag replaces 33-34 g of refractory mass by weight.The cup slag corrosion conditions according to the present invention are: a reaction taking place at 1600°C for 3 h, 14 g of crushed slag used, a hole of 25 mm diameter made inside the refractory block and a depth of 25 mm. The dimensions of the refractory block are 50*50*50 mm. The thickness of the refractory wall is 25 mm. The refractory mass that may have filled the hole is about 34 g with a density of 2.8 g / cm. 3 .

[0068] The present disclosure also relates to a method for preparing a refractory lining particle composition on a laboratory test scale. The method comprises the steps of taking appropriate proportions of alumina and magnesia grains and mixing a binder with said grains to form a binding aid. In addition, calcium titanate (CaTiCh) is added to the formed refractory mixture and mixed by means of mixing equipment, usually by hand. Distilled water is added at 3% to the mixed material and stirred manually for about 5 minutes to form a refractory mixture which can be used to press the material into different dimensions / shapes.

[0069] EXAMPLES

[0070] The following examples are provided to explain and illustrate various embodiments of the refractory lining particle composition of the present invention and in no way limit the scope of the invention as described and claimed:

[0071] COMPARATIVE EXAMPLE 1 (reference refractory material sample):

[0072] Reference refractory mix: A reference refractory material was prepared by mixing different grains and powders in their respective weight percentages:

[0073] Table 1

[0074] The ingredients of the reference refractory material sample were taken in their respective weight percentages and dry mixed for 30-45 minutes in a drum mixer or Hobart mixer. This material can be cast by dry vibration, it is also called neutral tamper, and it is sintered in situ during melting operations in an induction furnace.

[0075] Generally, the pouring temperature for steel melting is around 1600 °C, and therefore this 1600 °C is considered as the sintering / service temperature. To achieve homogeneity in the sintering structure, the residence time at 1600 °C was kept at 3 hours.

[0076] EXAMPLES OF THE INVENTION

[0077] EXAMPLE 1:

[0078] Step 1: The reference recipe material according to Comparative Example 1 was prepared by taking the above ingredients in their respective weight percentages and dry mixing them for 30-45 minutes in a drum mixer or Hobart mixer.

[0079] Step 2: 300g of the above reference material was taken and an additive (calcium titanate) was added at 0.5-5% by weight and mixed manually for 15-20 minutes.

[0080] Assessment tests:

[0081] Modulus of rupture (MOR):

[0082] Step 1: A reference material from Comparative Example 1 or a new material that is already mixed is taken for sample preparation.

[0083] Step 2: The required amount of mixed material is taken and 1% by weight dextrin (1 g / 100 g) is added as a raw binder. It is then mixed manually for 5 minutes.

[0084] Step 3: 3% by weight distilled water (3 ml / 100 g) is then added and mixed well manually for 5 minutes.

[0085] Step 4: The mixture formed in step 3, consisting of refractory, dextrin and water, is then poured into a metal mold. After filling the entire volume of the mold, it is pressed under a load of 50 tons for 1-2 minutes. Samples in the form of bars with dimensions of 150*25*25 mm are prepared for the MOR test.

[0086] Step 5: After pressing, the sample is taken out and dried in a convection oven for 1 hour at 100°C.

[0087] Step 6: After drying, the green sample is placed inside a muffle furnace for sintering. Step 7: The sintering cycle observed is as follows for all samples: a. from room temperature to 1100 °C at a heating rate of 300 °C per hour b. from 1100 °C to 1600 °C at a heating rate of 100 °C per hour c. holding for 31600 °C d. cooling from 1600 °C to room temperature at < 300 °C per hour inside the furnace

[0088] Step 8: The sintered samples are removed from the furnace.

[0089] Step 9: The modulus of rupture is measured for the samples sintered with a UTM machine at a loading rate of 1 mm / min without any preloading. The MOR was tested for Invention Example 1 and Comparative Example 1 at room temperature after sintering.

[0090] Sample condition: Samples were mixed with 1% dextrin and 3% water to prepare raw samples and then dried for 3 h.

[0091] Sintering: The samples were sintered at 1600 °C for 3 h. Bars of 150*25*25 mm were prepared.

[0092] The following table gives the results of the MOR test:

[0093] Table 2 Conclusion :

[0094] The average cold rupture modulus of an alumina-magnesia composite refractory which is taken as a reference is 31 kg / cm 2 The modulus of rupture of the new material with calcium titanate increased significantly. The values ​​are 62, 55 and 43 respectively for the addition of 4.5%, 2% and 1% calcium titanate in the alumina-magnesia matrix. It is clear that the MOR increased by more than 35%.

[0095] Cup corrosion:

[0096] Step 1: A reference material mentioned above or a new material already mixed is taken for sample preparation.

[0097] Step 2: The required amount of mixed material is taken and a 1% by weight (1 g / 100 g) dextrin-based raw binder is added. It is then mixed manually for 5 minutes.

[0098] Step 3: 3% by weight distilled water (3 ml / 100 g) is then added and mixed well manually for 5 minutes.

[0099] Step 4: The mixture formed in step 3, composed of refractory, dextrin and water, is then poured into a metal mold which has an accessory to make a hole of 25 mm in diameter and 25 mm in height in a cube of 50*50*50 mm, and pressed under a load of 50 tons for 1-2 minutes.

[0100] Step 5: After pressing, the sample is taken out and dried in a convection oven for 1 hour at 100°C.

[0101] Step 6: Slag is collected from an induction furnace for steel melting and crushed into fine powder. After drying, a raw sample is taken and the hole is filled with 14 g of crushed slag. The refractory samples with the 14 g of slag are then placed in a muffle furnace for sintering.

[0102] Step 7: The sintering cycle observed is as follows for all samples: a. from room temperature to 1100 °C at a heating rate of 300 °C per hour b. from 1100 °C to 1600 °C at a heating rate of 100 °C per hour c. holding for 31600 °C d. cooling from 1600 °C to room temperature at < 300 °C per hour inside the furnace

[0103] Step 8: The sintered and slag-reacted samples are then removed from the furnace and diamond-cut to check slag penetration under a stereoscope and microscope.

[0104] Cup Slag Corrosion Test: The test was conducted to evaluate the slag corrosion resistance of Invention Example 1 against an existing alumina-magnesia spinel composite refractory, which is the reference sample. Steel mill furnace slag was used for this test. The following table shows the chemical composition of the slag used for the test:

[0105] Table 3

[0106] Conclusion :

[0107] It was found that the slag penetration resistance of the new product with 2% calcium titanate is improved by ~27%. The slag penetration depth observed for the reference sample is around 11 mm, while for the sample with 2% calcium titanate, the depth is around 8 mm. In the case of the addition of 4.5% calcium titanate, the resistance is improved by 45%. The results clearly suggest that the addition of calcium titanate improves the slag penetration resistance of the refractory.

Claims

Claims 1. A particulate refractory lining composition, comprising from 0.1% to 10% by weight of calcium titanate, AI2O3, MgO and preferably a mineral binder, wherein the calcium titanate phase is preferably present in the form of CaTiO,, said calcium titanate phase reacting with AI2O3 to form a hibonite phase during sintering in the presence of MgO.

2. A particulate refractory coating composition according to claim 1, comprising: - 0.5 to 10% by weight of calcium titanate, the calcium titanate phase preferably being present in the form of CaTiO , ; - 60 to 95% by weight of AI2O3 present in the form of grains in the range of 0.25 to 16 mm and fines in the range of 1 to 250 pm; - 0 to 40%, preferably 3 to 30% by weight of MgO in the form of grains in the range of 0.5 to 1 mm and fines having a particle size of less than 500 μm; - 0 to 20%, preferably 1 to 10% by weight of binder, preferably a mineral binder chosen from the group consisting of SiO2, MgO, CaO, AI2O3, P2O5, Na2O, TiO2 or a combination thereof, the binder particle size being preferably still less than 0.1 mm.

3. A particulate refractory lining composition according to any preceding claim, wherein the addition of calcium titanate is less than 8% by weight, preferably in the range 2 to 5% by weight.

4. A particulate refractory lining composition according to any preceding claim, comprising a mineralizer, wherein the mineralizer particles are selected from the group consisting of B2O3, V2O5, TiO2, Y2O3, Fe2O3, CaO, NaCl, AICI3, MgCl, LiF, ZnF2, BaF2, CaF2 or a combination thereof.

5. A particulate refractory lining composition according to any preceding claim, comprising one or more desiccants, for example sodium sulfate. anhydrous magnesium (MgSC), boron oxide (B2O3), amorphous silica gel (SiCh), xanthan gum, acrylic or methacrylic acids, two-component polymerization binders, mixtures of boric acid and phosphate.

6. A particulate refractory lining composition according to any preceding claim, wherein 30 to 50% by weight of AbCh is present in the form of particles having a particle size of 1 mm or greater.

7. A method of preparing a refractory coating composition, the method comprising the steps of: 1) preparing a refractory particulate composition of any one of the preceding claims by: a) adding alumina-magnesia matrix precursors; b) preferably adding a binder to said matrix precursors; c) adding calcium titanate (CaTiCh) to the formed refractory mixture and mixing manually or by means of mixing equipment; 2) sintering said refractory coating particle at a temperature of 1000 to 1800°C, preferably above 1300°C, to form complex calcium aluminate and / or hibonite phases, and preferably at a temperature of 1600°C to form an aluminum-magnesium spinel MgAbC.

8. Refractory coating composition obtained by the process according to claim 7, in which: - the alumina and magnesia phases are present at less than 80% by weight, in the form of a combined aggregate containing an alumina-magnesia spinel MgAbC, preferably in the range of 30-40%; and / or - the alumina, magnesium and sodium phases are present at less than 10% by weight, in the form of a combined aggregate containing a sodium-magnesium-aluminium oxide AhoMg4Na205o; and / or - the content of impurities SiCh, P2O5, K2O, Na2O, ZnO, Q12O, FeO / Fe2O3 in total quantity is less than 3% by weight, relative to the total weight of the refractory.

Images