JPS6362471B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a CaO-based or CaO-MgO-based basic refractory that contains lime in a particularly stable state as a component of the fine particulate portion. CaO (lime), a basic refractory material, has a high melting temperature of over 2500℃, low dissociated oxygen pressure and vapor pressure, and is stable even in vacuum, making it a highly useful material as a refractory. be. Lime-based refractories based on this are used as furnace materials for melting low-oxygen, low-yellow, low-phosphorus steel, or so-called clean steel with few inclusions, especially in steel smelting. It is well known that it exhibits excellent properties. In this way, even though lime has excellent properties as a refractory, CaO is inherently highly hydration-reactive and easily reacts with moisture in the air to form hydroxides, a so-called digestion phenomenon. There were great difficulties in the manufacturing process, product storage means, use, etc., and production and use on an industrial scale had not yet been put to practical use. Therefore, in order to compensate for this drawback, for example, lime
1 to 10 sintering agents such as Fe ₂ O ₃ , TiO ₂ , Al ₂ O ₃ , SiO ₂ etc.
Various attempts have been made to obtain a hydration-resistant clinker by adding about %. Furthermore, attempts have been made to increase the digestion resistance by accelerating crystal growth by firing high-purity lime clinker at high temperatures. However, in these conventional methods, the former method adds impurities to the lime brick composition, which exacerbates the drawback of impairing the fire resistance and corrosion resistance of the refractory. former,
In either case, there is a problem in manufacturing technology that the clinker must be mechanically pulverized before use. In other words, when producing calcareous refractories, the raw material clinker is ground and the particle size is adjusted.
Usually, a small amount of non-aqueous organic binder such as pitch, tar, asphalt, paraffin, wax, oil, or resin is added to the mixture, and the product is kneaded and shaped into unfired bricks or fired bricks. In this case, in order to obtain a dense brick structure with good filling properties, fine particles with a particle size of 0.044 mm or less are added to
It is necessary to have a blend of about ~40%. However, even if a certain amount of impurities is added or a product calcined at a high temperature is used, when lime clinker is finely pulverized as described above, its specific surface area becomes large, so the digestion reaction rate becomes significantly faster, and its preservability increases. There was a noticeable tendency for the value to decrease. When partially digested fine particles are included in the mixture, the digested lime particles undergo a dehydration reaction during the firing of the molded body for fired bricks, or during use for unfired bricks, producing water vapor and evaporating, causing the bricks to form. This can lead to cracks in the structure and deterioration of the structure. In order to prevent this, if relatively coarse particles, such as pulverized particles with a small specific surface area of 0.3 mm or less or 1 mm or more, are blended as fine particles, the moldability will naturally be poor, resulting in a densely packed brick structure. cannot be obtained. In order to avoid the above-mentioned disadvantages, there are cases where magnesia, which does not cause a digestive reaction, is used in the particulate part of the refractory, but when this method is used, it is difficult to use magnesia, which does not cause a digestive reaction, because it lacks the particulate part of lime, which is said to be the matrix composition of lime bricks. Since the desulfurization and dephosphorization reactions that occur strongly in the fine particle portion during steel refining are not carried out, and the fine particle portion is converted into MgO, the metallurgical effect as in lime bricks is reduced. The present invention was created in consideration of the current situation,
The purpose of this project is to propose a method for making lime bricks with excellent properties by suppressing the digestion of the lime that makes up the matrix of calcareous bricks.Specifically, using slaked lime in the matrix composition of calcareous bricks, Conventional technology was applied by heating the compounded material to a temperature of 580°C or higher, where the dehydration reaction of Ca(OH) ₂ →CaO+H ₂ O occurs, and directly molding the compounded material while maintaining that temperature condition. The purpose is to provide a method for manufacturing calcareous bricks that eliminates problems. An example of the method of the present invention will be described in detail below.
Lime clinker manufactured by adding a small amount of sintering agent such as TiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ in advance or high purity lime clinker calcined at high temperature is pulverized into coarse particles of 4 to 1 mm, for example. diameter, as an intermediate particle 1
After sieving so that there is a diameter of mm or less, this
Mix 10-50% slaked lime. Next, salts such as CaCl ₂ , MgCl ₂ , and Ca(NO ₃ ) ₂ are added to the above mixture of clinker and slaked lime as an additive binder in a range of 1 to 15% of the amount to be added. Molding is carried out under heating conditions of 800℃. In conventional technology, a small amount of CaCl ₂ is added to lime to give it appropriate plasticity by utilizing the liquid phase transition of CaCl ₂ in a hot state of 400 to 800 degrees Celsius, and compression, extrusion, and centrifugal force methods are used. There is a known method for producing lime refractories that is molded using methods such as molding methods to provide hydration resistance. There were difficulties, such as the need for equipment suitable for the handling work. In the present invention, slaked lime is used as a particulate component of the mixed material, the mixed material is heated and molded directly in that state, and a substance that lowers the eutectic point is combined with the above-mentioned additive binder component during this time. , their liquid phase formation temperature is lowered so that the plasticity that allows for the required shaping is achieved in a substantially advantageous low temperature range. That is, for example, CaCl ₂ alone does not begin to form a liquid phase until the temperature reaches 772 °C, so below that temperature the CaO−CaCl ₂ mixture cannot exhibit plasticity, but CaCl ₂ lowers its eutectic point. It is a substance. NaCl, Ca( _NO3 ) ₂ , _CaCO3 , KCl,
By coexisting one type or a combination of two or more of BaCl ₂ , MgCl ₂ , CaSO ₄ , CaF ₂ , etc., the liquid phase formation temperature can be substantially lowered, making handling of the material extremely easy. That's what I did. The formation temperature of the liquid phase when CaCl ₂ and each salt coexist is as shown in Table 1. For example,
By adding NaCl to _CaCl2 , its melting point can be lowered to 500 °C. The temperature shown in Table 1 is the lowest melting temperature of the system, and the composition ratio is the ratio that indicates the state, and the addition ratio in the present invention does not need to be limited to this.
It may be lower than 772°C, and it is particularly desirable to select a mixing ratio that provides a eutectic point that is closer to the dehydration temperature of slaked lime, 580°C. Lowering the liquid phase formation temperature lowers the heating temperature of the material mixture, which can be used to reduce the thermal expansion of molds in molding machines for commercialization, improve product accuracy, and other weighing-related matters. It contributes to energy saving in terms of heat balance, such as being extremely easy to handle, and has great benefits as well as great effects. These salts combined with CaCl ₂ may be premixed with slaked lime or mixed directly with aggregate particles, and in both cases the same effect can be achieved. Looking at the behavior of each composition due to temperature changes in the method of the present invention, when a predetermined temperature is reached, slaked lime first dehydrates and changes to quicklime CaO. Since the CaO produced at this time starts from ultrafine particles of slaked lime, it is in an extremely fine and active state with a particle size of about 1 to 2 μm. As mentioned above, if you try to mechanically crush lime clinker, there is a crushing limit and it is extremely difficult to reduce the entire size to less than a few microns in diameter. However, in the method of the present invention, heating is a necessary condition and it is produced from slaked lime. It contains ultra-fine particles of quicklime, and the same effect as mixing large amounts of such fine quicklime particles can be obtained, and there is no concern that such ultra-fine lime particles will be digested. be. At the same time that the brick particulate part becomes CaO, the added salt also melts and a liquid phase is generated, giving the mixed material appropriate plasticity.If it is molded under pressure at that temperature, it has good filling properties. This results in a dense brick structure. Although the refractories obtained in this way contain CaO in the fine particles, they are dense and have low porosity, so they have a small specific surface area.
It has extremely high resistance to the intrusion of atmospheric moisture and maintains stable properties. The binder component used in the production method according to the invention is not limited to CaCl ₂ or substances forming a eutectic thereof with CaCl ₂ , but includes MgCl ₂ or
By using salts such as Ca(NO ₃ ) ₂ alone or in combination with substances that lower the eutectic point, basic refractories containing lime in the fine grains can be obtained with stable properties. . The melting points of the salts in these cases are also as illustrated in Table 1. Example 1 Lime clinker having the chemical composition shown in Table 2 is crushed and sieved into particles with a diameter of 4 to 1 mm and a diameter of 1 mm or less to obtain aggregate. Apart from this, Nos. 1 to 11 in Table 3
The salts shown in the table below are mixed in a diameter of 0.3 mm or less with slaked lime at the mixing ratio shown in Table 3. Add and mix the lime clinker aggregates with a diameter of 4 to 1 mm and less than 1 mm to this mixture, and the final mixed mixture is heated to the temperature shown in Table 3, so that the whole becomes uniform. It was held for 3 hours. Looking at the products obtained by molding, as shown in Table 4, bricks No. 1 to No. 9 of the present invention were well densified compared to the conventional products, but No.
If the slaked lime blending ratio is low as in No. 11, or the opposite No.
When the slaked lime blending ratio exceeds 50%, as in No. 10, the filling properties deteriorate and a dense refractory cannot be obtained. In addition, Nos. 1 to 9 will remain undigested for two weeks if left in the atmosphere, and for three months if kept in a tin can, and will not be affected by transportation or storage, and will be sufficient for practical use. Stability was confirmed. In addition, when No. 2 bricks were laminated in a large ladle at a steel factory and tested, they showed superior durability to conventional bricks, and the use of high alumina bricks with 85% Al ₂ O ₃ was equivalent or better. showed that. Example 2 Bricks were trial-produced in exactly the same manner as in Example 1, except that all or part of the lime clinker used in Example 1 was replaced with magnesia clinker having the composition shown in Table 2. The blending ratio in this example and the physical properties of the obtained product are shown in Table 5, and the MgO
By adding , the corrosion resistance was increased compared to that of pure lime.

【table】

【table】

【table】

【table】

【table】

【table】

【table】

[Table] In the present invention, by adjusting the additive binder component, it is possible to improve productivity by lowering the working temperature range and speeding up the process, while also enabling stable product supply. It goes without saying that in accordance with the spirit of the invention, the invention is not limited to the above embodiments, and any applications, diversions, etc. derived therefrom are encompassed within the technical scope of the invention.

Claims (1)

[Scope of Claims] 1. One or more types of lime clinker, dolomite clinker, or magnesia clinker are crushed and adjusted to have an appropriate particle size distribution as aggregate, and 10 to 15% of slaked lime is added to this, and Addition of 1 part of CaCl ₂ , MgCl ₂ or Ca(NO ₃ ) ₂ as a binder
Mix ~15% and heat the resulting material mixture to 580~800℃
After the dehydration reaction of the slaked lime in the formulation is completed by holding it in a heated state of A method for producing a basic refractory containing the same. 2 Add binder components in the material mixture to CaCl ₂ or CaCl ₂ with NaCl, Ca(NO ₃ ) ₂ , CaCO ₃ , KCl,
One or two of BaCl ₂ , MgCl ₂ , CaSO ₄ , CaF ₂
2. A method for producing a basic refractory containing lime in the fine particulate portion according to claim 1, characterized in that it is a combination of two or more kinds of refractories. 3 Add binder component in the material mixture to MgCl ₂ or MgCl ₂ with one or more of KCl, NaCl, BaCl ₂ .
2. A method for producing a basic refractory containing lime in the fine particulate portion according to claim 1, characterized in that it is a combination of two or more kinds of refractories. 4 The additive binder component in the material mixture is
(NO ₃ ) ₂ or Ca(NO ₃ ) ₂ in combination with BaCl _2. The production of a basic refractory containing lime in the fine particles as set forth in claim 1. Method.