JP4490879B2 - Repair material for magnesia dry spraying construction - Google Patents

Description

  The present invention relates to a magnesia dry spraying repair material used for spray repair of an industrial kiln.

  Spray repair methods for industrial furnace walls are roughly classified into dry methods and wet methods. In the dry method, a spray repair material made of a powder mixture such as a refractory raw material powder and a binder is conveyed by air, mixed with water supplied by a separate pipe at a nozzle, and sprayed onto a work surface. On the other hand, in the wet method, a spray repair material kneaded in advance is sent to a nozzle through a pressure feed pipe, and if necessary, a quick setting agent is added and sprayed at the nozzle portion.

  Compared to the wet method, the dry method has advantages such as no need for prior kneading work, nozzle clogging hardly occurring, and easy operation of the construction apparatus. However, the dry method has the following problems because water is added to the spray material at the nozzle.

1) The spray repair material is not sufficiently mixed with water, and dust generation is likely to occur, which is not preferable in the work environment.

2) Adhesion is inferior due to insufficient mixing of spray repair material with water. Therefore, it is necessary to add a large amount of water to ensure adhesion, and as a result, the structure of the construction body becomes porous. 3) Insufficient mixing of the spray repair material and water can cause rebound loss during spraying, It causes segmentation in the material transport piping and causes non-uniform construction body structure.

  In order to solve this problem in the dry spray method, a spray repair material in which the powder constituting the spray repair material is pre-granulated with a dispersant (surfactant) or a binder to eliminate fine powder has been proposed. ing. In the granulation method in this case, coarse particles of the refractory raw material are wetted with a liquid dispersant or a liquid binder, and the refractory raw material fine powder is adhered to the surface (Patent Document 1).

On the other hand, a method of adding silica sol or alumina sol to the refractory raw material powder, kneading and granulating has also been proposed (Patent Document 2).
Japanese Patent Laid-Open No. 5-4875 JP-A-9-48675

  In the conventional dry spraying method, dust generation is prevented by using a granulated spray repair material (hereinafter referred to as a granulated spray material). However, the adhesion and the compactness of the construction body are still not sufficient.

  This invention makes it a subject to improve adhesiveness and the compactness of a construction body in this granulated spray material used for the dry-type spray method.

  The feature of the present invention is that magnesia powder 60 to 90 mass% obtained by granulating magnesia powder containing at least 70 mass% of particles having a particle size of 0.5 mm or less to 3 mm or less with a liquid dispersant and then drying. And magnesia powder having a particle size of 5 to 1 mm and a magnesia dry-type repair material having a fireproof blend composition of 5 to 35% by mass and alumina cement.

  Further, magnesia powder containing at least 70% by mass of particles having a particle size of 0.5 mm or less, 10% by mass or less of particles having a particle size of 0.075 mm or less and more than 0.045 mm, and 30 to 60% by mass of particles having a particle size of 0.045 mm or less. Of magnesia particles obtained by granulating the powder to a size of 3 mm or less with a liquid dispersant and drying, magnesia powder containing 5 to 35 mass% of magnesia powder having a particle size of 5 to 1 mm, and alumina cement as a fireproof blend composition It is a repair material for quality dry spraying construction.

  The refractory raw material powder of the spray repair material is appropriately adjusted in particle size to coarse particles, medium particles, and fine particles in order to obtain a dense construction body. In the prior art, as described above, granulation is performed by attaching fine particles to coarse particles, or coarse particles, medium particles, and fine particles are collectively granulated to a specific particle size.

  On the other hand, the spray repair material of the present invention is obtained by granulating magnesia powder mainly composed of fine particles and combining it with magnesia powder having a particle size of 5 to 1 mm. The spray repair material of the present invention exhibits excellent effects in adhesion and the compactness of the construction body, and the reason is considered as follows.

  That is, the granulated particles are crushed on the surface to be constructed, and improvement in adhesion and compactness of the construction body cannot be expected unless they become fine particles. However, the spray repair material of the present invention has a magnesia particle size of 5 to 1 mm together with the granulated particles. Due to the presence of the powder, the particles formed on the work surface are broken by the collision of coarse particles having a particle size of 5 to 1 mm, and the pulverization is promoted.

  In addition, the magnesia powder that composes the particles is instantly gelled by the reaction of the dispersant used for the granulation bond with the water supplied during spraying, and the particles form a viscous gel-like structure. . Coarse particles having a particle size of 5 to 1 mm are stabbed one after another into the gel-like fine powder structure simultaneously with pulverization of the granulated particles, thereby reducing rebound loss. As a result, the adhesion of the spray repair material is remarkably improved, and the relative segregation between fine particles and coarse particles is prevented, and the construction body has a uniform and tightly packed structure.

  Alumina cement is not granulated and exists only on the surface of the granulated and coarse particles in the spray repair material structure. As a result, the alumina cement comes into contact with the construction water quickly and reliably, the cement hydration reaction is promoted, and the construction body structure becomes high strength.

  On the other hand, when using granulated particles obtained by adhering fine particles to coarse particles as in the past, or using granulated particles with a specific particle size of coarse particles, medium particles, and fine particles, It does not break easily and it is difficult to obtain a uniform structure on the work surface. For this reason, both the adhesion and the compactness of the construction body are greatly inferior to the spray repair material of the present invention.

  In the present invention, the magnesia powder constituting the granulated particles contains at least 70% by mass of particles having a particle size of 0.5 mm or less. Further, the particle size of the particles is 3 mm or less. More preferably, it is 2 mm or less. If the particle size of the particles is too large, rebound loss increases during spraying. Further, when the ratio of particles having a particle size of 0.5 mm or less in the magnesia powder constituting the particle formation is less than 70% by mass, it is difficult to obtain particles having a particle size of 3 mm or less because the particle size is already large in powder units.

  The particle size of the magnesia fine powder constituting the particle-forming is within the above particle size range, and the particle size ratio of 0.075 mm or less and more than 0.045 mm is 10 mass% or less, and the particle size ratio of 0.045 mm or less is 30 to 60. In the case of mass%, it is easy to produce particles. This is because the granulation of fine powder goes through a process in which other particles are coated on the core particles, so that the intermediate particle size is reduced in the particle size structure of the fine powder portion, and the core particles are given by providing a gap between the particle sizes. This is because other particles are more easily coated.

  Due to the gap between the particle sizes in the particles, the particles are more easily broken by the collision of coarse particles, and are easily atomized to further improve the adhesion of the spray repair material.

  The spray repair material of the present invention provides excellent effects in adhesion and the compactness of the construction body, in addition to dust generation prevention and the like by using particles. As a result, the pre-kneading that the dry spraying method has is unnecessary, and the effects such as simple construction equipment can be sufficiently exhibited.

  The refractory raw material used for the spray repair material of the present invention is sintered or electrofused magnesia powder. In addition, examples of the sintered magnesia powder include seawater magnesia and natural magnesia. Magnesia powder is a high melting point material and exhibits excellent corrosion resistance against molten metal.

  The magnesia powder used for the production of the magnesia particles is assumed to contain at least 70% by mass of particles having a particle size of 0.5 mm or less. If particles with a particle size of 0.5 mm or less are less than 70% by mass, it is difficult to obtain particles with a particle size of 3 mm or less as mentioned above. The construction body of the organization cannot be obtained.

  The particle size of the magnesia powder constituting the particles is within the above particle size range, and the particle size ratio of 0.075 mm or less and more than 0.045 mm is 10 mass% or less, and the particle size ratio of 0.045 mm or less is 30 to 60 mass. % Is preferred. As a result, the ratio of the intermediate particle size region of the magnesia powder constituting the granulated particles is reduced, and a gap is generated in the particle size structure of the fine powder portion to be granulated and the fine powder portion to be granulated. The fine powder part is coated on the surface, making it easy to obtain particles. Further, due to the gap between the particle sizes of the particles, the particles are further broken by the collision of coarse particles, and are easily atomized to further improve the adhesion of the spray repair material.

  The particle size of the magnesia fine powder constituting the particles is 2 mm at maximum. When particles exceeding 2 mm are used, the kinetic energy of the particles is increased and the rebound loss is increased.

  As described above, the particle size of the particles is 3 mm or less, preferably 2 mm or less in order to reduce the rebound loss. The lower limit of the particle size of the granulated particles becomes a certain particle size by the granulating operation. Although it does not limit, a preferable minimum particle size is 0.5 mm.

  As a specific example of the dispersant used for granulation, a known dispersant for an amorphous refractory can be used. For example, condensed phosphates such as sodium hexametaphosphate, sodium tripolyphosphate, β-naphthalene sulfonate formalin condensate, melamine sulfonate formalin condensate, amino sulfonic acid and its salt, lignin sulfonic acid and its salt, polyacrylic acid And salts thereof, polycarboxylic acids and salts thereof, oxycarboxylic acids and salts thereof, and the like. Among them, those having a high water reducing effect such as polyacrylic acid and having a high viscosity in an aqueous solution are preferable.

  The solvent for making the dispersant liquid is preferably water. A liquid dispersant dissolved with 2 to 4 times as much water as the dispersant 1 in terms of mass ratio is used.

  The magnesia particles can be obtained by dropping about 5 to 10% by mass of this liquid dispersant on the outside of the magnesia powder and granulating it by a tilting method. Dry after granulation.

  As another granulation means, it is possible to use silica sol or alumina sol as a binder. However, when silica sol or alumina sol is used, the strength of the particles after drying is large, the particles are not crushed during spraying, and the rebound loss of the spray repair material increases, so that the adhesion effect of the present invention is obtained. I can't.

  The ratio of coarse particles (magnesia powder) having a particle size of 5 to 1 mm to be blended separately from the particles is 5 to 35% by mass. If it is less than 5% by mass, the particles are not sufficiently crushed at the time of spraying, or the effects of adhesion and denseness are inferior. If it exceeds 35% by mass, the proportion of coarse particles in the entire spray repair material becomes too large, and in this case, the effect of adhesion and denseness is also inferior. More preferably, it is 20-30 mass%.

  The magnesia powder blended separately from the granulated particles requires 5 to 35% by mass of coarse particles having a particle size of 5 to 1 mm as described above, but a combination of magnesia powder having a particle size of less than 1 mm is used as long as the effects of the present invention are not impaired. May be. For example, 5% by mass or less of magnesia powder having a particle size of less than 1 mm may be combined. If the proportion of magnesia powder having a particle size of less than 1 mm is too high, the effect of preventing dust generation cannot be obtained.

  Alumina cement serves as a binder for the entire spray repair material. The preferable ratio is 1 to 10% by mass.

  In addition to the above blend, the spray repair material of the present invention may further contain slaked lime, fibers, metal powder, aluminum lactate and the like as necessary. Specific examples of the fibers are vinylon, PVA, paper fiber, sepiolite and the like.

  The spray repair material according to the present invention can be used for repairing furnace walls of various industrial kilns such as steelmaking converters and vacuum degassing furnaces.

  Examples of the present invention and comparative examples thereof are shown below.

Table 1 shows the composition and granulation status of magnesia particles used in each example. A liquid dispersant in which polyacrylic acid was dissolved in 3 times water was dropped and granulated by a tilting method. The dripping amount of the liquid dispersant was set to 7% by mass based on the entire magnesia powder.

  The particle size was adjusted with a JIS sieve opening sieve. For example, since 1 mm or less usually includes a part of particles having a particle size of 0.075 mm or less, 0.075 mm or less, 0.075 mm or less to more than 0.045 mm, and 0.045 mm or less. Also shown.

  The granulated particle diameter indicates the particle diameter of the finally obtained granulated particles by combining raw materials of various particle sizes. The degree of granulation is the result of confirming whether granulated particles are produced by combining granulated raw materials with various particle sizes, ○ is easy to produce, Δ is easy to granulate It shows that it took considerable time to obtain particles.

  A to E are magnesia particles suitable for the present invention. Among these, C to E are examples in which the proportion of the intermediate particle size of the magnesia powder constituting the particles is reduced. The particles C to E can be formed in a shorter time than the particles A to B, which is preferable in the productivity of the particles. In addition, F has a small proportion of about 50% by mass of a particle size of 0.5 mm or less with respect to magnesia powder constituting the particle-forming. G has a large particle size of magnesia powder constituting the particle-forming.

Table 2 shows the blending composition of the spray repair material blended with each of the particles shown in Table 1 and the test results. Each example was sprayed by a dry method using a piccola gun, and each physical property value was measured. The spraying conditions were a powder conveying air pressure of 0.2 MPa, a spraying repair material of 30 kg was sprayed at a distance of 300 mm between the work surface and the nozzle tip, and a construction body having a thickness of about 50 to 100 mm was obtained. The construction surface was made of an alumina castable refractory assuming repair of the kiln refractory.

  The amount of construction water was appropriately adjusted for each spray repair material in each example. If the amount of moisture is small, it will not adhere to the construction surface, and if it is too much, it will flow down after attachment.

  In the dust prevention test, the degree of dust generation was determined by visual inspection. Adhesion was determined from the adhesion rate.

  In the test of the strength of the construction body, the apparent porosity, and the bulk specific gravity, the construction body was cut out and measured as a test piece. The construction strength was measured by bending strength. The strength of the construction body is affected by the uniformity and the denseness of the construction body structure together with the apparent porosity.

  In the spray construction using the embodiment of the present invention, not only the effect of preventing dust generation but also the construction body strength and adhesion are excellent. In addition, a compact and uniform construction body having a low apparent porosity was obtained.

  On the other hand, in Comparative Example 1, since the ratio of the particle size exceeding 0.5 mm in the granulated particles is large, the effect of the granulated particles is not sufficiently exhibited and the adhesion is deteriorated. Since Comparative Example 2 has a large proportion of the particle size exceeding 0.5 mm in the particle-forming, and there is no combination with magnesia aggregate, it is inferior in any of adhesion, construction strength, and apparent porosity. Since Comparative Example 3 has a small proportion of particles, it has poor adhesion. Comparative Example 4 has no combination of magnesia aggregates and is inferior in adhesion and apparent porosity. In Comparative Example 5, since the magnesia aggregate has a large particle size, the adhesion is poor. In Comparative Example 6, since the magnesia aggregate has a small particle size, the construction moisture is increased, dust is generated, and the particles are not easily broken in the construction. Therefore, the adhesion, construction strength, and apparent porosity are inferior.

Claims (2)

  Magnesia powder containing at least 70% by mass of particles having a particle size of 0.5 mm or less is granulated to a size of 3 mm or less with a liquid dispersant and then dried to obtain 60 to 90% by mass of magnesia particles and 5 to 1 mm of magnesia powder. Repair material for magnesia dry-type spraying construction having 5 to 35% by mass and alumina cement as a fireproofing composition.   Liquid magnesia powder containing at least 70% by mass of particles having a particle size of 0.5 mm or less, 10% by mass or less of particles having a particle size of 0.075 mm or less and more than 0.045 mm, and 30 to 60% by mass of particles having a particle size of 0.045 mm or less. A magnesia dry type having a refractory blending composition of 60 to 90% by mass of magnesia particles obtained by granulating to 3 mm or less with a dispersant and drying, 5 to 35% by mass of magnesia powder having a particle size of 5 to 1 mm, and alumina cement. Repair material for spray construction.