JP2023161293A - Monolithic refractory for dry spraying and dry spraying construction method using the same - Google Patents

Abstract

[Problem] When used in a dry spray construction method, it is possible to increase the curing strength of the resulting construction body, and it is possible to maintain the shape of the construction body even in applications where it is subjected to impact or external force, which was difficult to use with conventional products. To provide a monolithic refractory for dry spraying with excellent versatility.
[Solution] A monolithic refractory for dry spraying used in a state containing a dry powder refractory material, a dry powder alumina cement, and a silica sol with a silica solid content concentration of 20% to 50%, the alumina cement in an amount of 1% to 5% based on 100% of the refractory material, and a silica sol in which the silica solid content contained in the silica sol is 3% based on 100% of the refractory material. % to 30%, and further contains dry powder hydraulic alumina in an external amount of 0.7% to 2.0% based on 100% of the fireproof material. A refractory and a construction method using the monolithic refractory.
[Selection diagram] None

Description

The present invention relates to technology for dry-sprayed monolithic refractories, and more specifically, silica sol, alumina cement, and hydraulic alumina are used as hardening agents, and these are used as binders for refractory materials to provide sufficient curing strength. The present invention relates to a monolithic refractory for dry spraying construction and a dry spraying construction method using the same.

In the construction of refractories, methods such as pouring, filling, and spraying of monolithic refractories are carried out. Among them, pouring construction is the mainstream, but pouring construction requires kneading work using a large mixer at the construction site, frame work, and frame removal work, making the work complicated and large-scale construction. On the other hand, spraying construction has the advantage of not requiring such complicated work.

Spraying construction is broadly divided into wet spraying construction and dry spraying construction. In wet spraying construction, the refractory material and water are sufficiently kneaded using a mixer, etc., and while the slurry-like mixture is pumped, air and quick-setting agent (hardening agent) are mixed at the tip of the spray nozzle. This is a construction method that involves introducing and spraying. On the other hand, dry spraying construction requires small and simple equipment and is relatively easy to work with since it does not contain water.After mixing the dry powder, the mixture is pumped with compressed air and turned into dry powder fireproof material at the tip of the spray nozzle. This is a construction method in which water is added, kneaded in a nozzle, and then sprayed to obtain a construction body. Therefore, dry spraying construction is a highly useful construction method as a simpler construction method. The monolithic refractories used in the above-mentioned spraying construction are required to undergo a good curing reaction after spraying, and as a result, a sprayed refractory (constructed body) with excellent durability can be obtained. For this reason, various proposals have been made regarding spray-on monolithic refractories with excellent performance, as listed below.

In Patent Document 1, 6 to 8 mass % of silica sol containing 15 to 25 mass % of SiO ₂ is added to a base material of alumina-spinel castable containing 0.05 to 1.0 wt % of ultrafine magnesia powder, and then sprayed. Refractories have been proposed. It is also described that by doing so, the alumina-spinel refractory can be made into a spray refractory with excellent durability and high adhesive strength. In addition, Patent Document 1 discloses that a sol-gel reaction is caused by silica sol and ultrafine magnesia powder, and this reaction is used to harden the refractory base material, thereby eliminating the need for binders and curing agents that are conventionally used. It is stated that he was able to invent spray-on refractories. Patent Document 1 describes that alumina-spinel spray refractories using alumina cement as a binder have poor workability and have not been used as spray refractories in the past.

In contrast to the above-mentioned Patent Document 1, Patent Document 2 points out the following and makes a new proposal that will be described later. "Here, the particle size of the ultrafine magnesia powder is important in order to accelerate the curing reaction of the refractory material. For example, if the particle size of the ultrafine magnesia powder is large, the amount of elution into the silica sol will decrease, The curing reaction is no longer carried out efficiently.Thus, although Patent Document 1 describes the use of ultrafine magnesia powder, it does not specifically describe the particle size of the ultrafine magnesia powder. For this reason, there is a possibility that the curing reaction of the refractory material will not be promoted. If the curing reaction is no longer promoted, the shape retention of the refractory material will deteriorate, leading to a decrease in the adhesion rate, and in other words, a decrease in durability.

Patent Document 2 proposes the following in order to provide a dry-sprayed refractory that can ensure the miscibility of silica sol and refractory material, promotes the curing reaction, and has excellent durability as a result. That is, Patent Document 2 includes a refractory material and a silica sol, the refractory material contains a compound containing Mg or Ca with a particle size of 10 μm or less, and the compound containing Mg or Ca with a particle size of 10 μm or less in the refractory material. A proposal has been made for a dry spraying material in which the content is 0.02% or more based on the silica solid content in the total amount of silica sol. However, according to the studies of the present inventors, there is a possibility that a sufficient usable working life cannot be secured with silica sol-added spray-installed refractories that take advantage of the rapid setting caused by the reaction between the above-mentioned Mg or Ca compounds and silica sol. is high.

On the other hand, Patent Document 3 discloses a cement-free dry spraying construction in which a metal sulfate or metal halide salt is added as a coagulant to a fireproof material, silica sol, and a compound of Mg or Ca with a particle size of 1 mm or less. Monolithic refractories have been proposed. Patent Document 3 describes that by adding a specific coagulant, a monolithic refractory material for dry spraying construction can be obtained that has sufficient adhesion and working life.

Patent No. 3126003 Patent No. 5896515 Japanese Patent Application Publication No. 2020-1992

Important characteristics of dry-sprayed monolithic refractories include the curing strength of the cured body (constructed body), in addition to the adhesion and working life upon curing described in the above-mentioned prior art documents. The curing strength of a cured product is "mechanical strength in a state where it is cured at room temperature after being sprayed in a furnace," and is an important property in maintaining the shape of a construction product at room temperature. The above Patent Document 3 states that for dry-sprayed refractories using silica sol as a binder, a compressive strength of 1.0 MPa or more after curing is required as the curing strength required to remove the frame. .

However, according to the inventors' study, with a compressive strength of 1.0 MPa, the constructed body can be maintained in applications where relatively no external force is applied to the constructed body (cured body), but in applications where stress is applied or where unexpected impact occurs. There is a possibility that the construction structure will not be able to maintain its shape when Generally, dry-sprayed refractories using silica sol as a binder have lower curing strength than those using cement as a binder. Therefore, it is desirable that no external force be applied to the constructed body obtained by dry-sprayed monolithic refractories using silica sol as a binder. As mentioned above, the present inventors found that the dry-sprayed monolithic refractories using silica sol as a binder have a problem in terms of versatility that needs to be solved because the installation locations are more limited than with cement binder products. I realized that.

On the other hand, in the dry-sprayed monolithic refractories in the prior art documents listed above, adhesion and working life during curing are mentioned and discussed in detail, but the curing of the cured product (constructed product) There is no detailed mention or consideration of strength.

Therefore, an object of the present invention is to increase the curing strength of the resulting construction body when using a dry spray construction method using silica sol as a binder, and to improve the curing strength of the construction body, which has been difficult to use with conventional products. To provide a monolithic refractory for dry spraying which can maintain the shape of a constructed body even in applications where external force is applied and has excellent versatility without any problems in practical use.

The above object is achieved by the present invention as follows. That is, according to the present invention, the following monolithic refractory for dry spraying construction is provided.
[1] A monolithic refractory for dry spraying used in a state containing a dry powder refractory material, a dry powder alumina cement as a hardening agent, and a silica sol having a silica solid content concentration of 20% by mass or more and 50% by mass or less And,
Containing the alumina cement in an amount of 1% by mass or more and 5% by mass or less, based on 100% by mass of the refractory material,
The silica sol is contained within a range in which the silica solid content contained in the silica sol is 3% by mass or more and 30% by mass or less, multiplied by 100% by mass of the refractory material,
Further, the monolithic refractory for dry spraying is characterized in that it contains dry powder hydraulic alumina in an amount of 0.7% by mass or more and 2.0% by mass or less, based on 100% by mass of the refractory material. thing.

Preferred forms of the above-mentioned monolithic refractory for dry spraying include the following.
[2] The room temperature bending strength of the "room temperature curing cured product of monolithic refractories" which is a constructed body by dry spraying construction in which the monolithic refractory for dry spraying is sprayed from the nozzle tip is 1.0 MPa or more [1] Monolithic refractories for dry spraying described in .
[3] The refractory material has an alumina raw material as a main component, and has a fine particle component with a particle size of 0.075 mm or less within a range of 15% by mass or more and 50% by mass or less, according to [1] or [2] above. Monolithic refractories for dry spraying as described.
[4] Furthermore, based on 100% by mass of the refractory material, at least one compound selected from the group consisting of condensed phosphates, organic acids, and organic acid salts is added in an amount of 0.01% by mass or more to 0.01% by mass. The monolithic refractory for dry spraying according to the above [1] or [2], containing within the range of 3% by mass or less.

The present invention provides the following dry spraying construction method as another embodiment.
[5] A construction method in which the dry spraying monolithic refractory described in [1] or [2] above is sprayed onto the construction surface from a spray nozzle to perform dry spray construction,
A dry powder mixture obtained by pre-mixing the dry powder refractory material, the dry powder alumina cement, and the dry powder hydraulic alumina is sent to the spray nozzle, the silica sol is added and kneaded, and the kneaded material is sprayed. A dry spraying construction method characterized by spraying the monolithic refractory for dry spraying onto a construction target surface from the tip of a nozzle.

Preferred embodiments of the above dry spraying construction method include the following.
[6] The dry spray construction method according to the above [5], wherein the silica sol is added at the tip of the spray nozzle.

According to the present invention, in a monolithic refractory for dry spraying using silica sol as a hardening agent (binder) in addition to dry powder alumina cement, by adding a specific amount of dry powder hydraulic alumina, the product can be obtained by dry spraying. A highly versatile dry method that can be used in a wider range of construction areas without any practical problems, increasing the curing strength of the construction body and maintaining the shape of the construction body even in applications where it is subject to impact or external force. A sprayable monolithic refractory can be provided. Furthermore, according to the present invention, by using the above-mentioned excellent dry-sprayed monolithic refractories, it can be used in applications and parts where it was difficult to apply monolithic refractories, such as waste incinerators, cement manufacturing equipment, and rotary kilns. It is also possible to provide a construction method that allows for good dry spraying construction.

Hereinafter, the present invention will be explained by citing preferred embodiments. Alumina cement is generally used as a binder for dry-sprayed monolithic refractories. On the other hand, as mentioned earlier, by causing a sol-gel reaction with silica sol and ultrafine magnesia powder, and using this reaction to harden the refractory base material, spray-on fireproofing can be achieved without using conventional binders and hardeners. There are suggestions for things and things that can be done. In addition, when this technology is used to include a refractory material and a silica sol, and the refractory material contains a compound containing Mg or Ca with a particle size of 10 μm or less, the content of the compound can be set to a specific amount. Proposals have been made to accelerate the reaction or to further use a specific coagulant to secure the usable working life necessary for adjusting the construction thickness of the sprayed construction body.

Under the above-mentioned circumstances, the present inventors used dry powder alumina cement and silica sol together as components that harden and function as a binder for the base material, and also added dry powder hydraulic properties. It has been discovered that by using alumina, it has sufficient adhesion and pot life, and it is possible to increase the curing strength of a construction body obtained by dry spraying, which is the objective of the present invention, without impairing workability. This led to the present invention. Hereinafter, the structure of the monolithic refractory for dry spraying of the present invention will be explained.

The monolithic refractory for dry spraying of the present invention is characterized by containing a dry powder refractory material as a base material, and alumina cement, silica sol, and hydraulic alumina within a specific range for the refractory material. do.

The type of refractory material is not particularly limited, and includes, for example, sintered alumina, fused alumina, bauxite, banded shale, mullite, andalusite, chamotte, lowite, silica, sintered spinel, fused spinel, chromite, Examples include chromium oxide, zircon, zirconia, silicon carbide, graphite and pitch. In the present invention, one type or a combination of two or more types of materials selected from the group consisting of these materials can be used. At that time, it is preferable to use a refractory material whose particle size has been adjusted to have a particle size composition suitable for spraying. Further, in addition to the above-mentioned materials, refractory ultrafine powder selected from refractory clay, calcined alumina, silica flour, carbon black, etc. can also be used in combination.

The monolithic refractory for dry spraying of the present invention uses the above-described refractory material as a base material, and contains silica sol, alumina cement, and hydraulic alumina, all of which function as a binder for the refractory material. It is characterized by The roles of these components will be described later.

The silica sol may have a silica solid content concentration of 20% by mass to 50% by mass, and any commercially available silica sol that satisfies this requirement can be used as appropriate. When the concentration of silica solid content is less than 20% by mass, a sol-gel reaction occurs with the silica sol, and the silica sol cannot sufficiently contribute to curing of the refractory material that is the base material. Specifically, if the sol-gel reaction is not carried out sufficiently, the refractory material will run off the successful surface due to poor curing, resulting in decreased adhesion and adhesion. On the other hand, when the concentration of silica solid content exceeds 50% by mass, the viscosity of the silica sol becomes excessively high, the miscibility of the silica sol and the refractory material decreases, and nozzle clogging occurs during construction.

The sol-gel reaction of the silica sol used in the present invention occurs with the Ca component contained in the alumina cement, and in the present invention, this reaction is utilized as one of the means for curing the refractory base material. A Mg compound may be added as a curing agent for the silica sol. The amount of Ca component used in the above-mentioned sol-gel reaction is, for example, 1.0% by mass to 5.0% by mass with respect to the solid content of silica in the silica sol constituting the monolithic refractory for dry spraying of the present invention. % should exist. On the other hand, since the amount of alumina cement constituting the dry-sprayed monolithic refractory of the present invention contains Ca components within this range, there is usually no need to separately add Ca components or Mg components. . When the Ca component is less than 1.0% by mass based on the silica solid content in the silica sol, the amount of Ca ions eluted into the silica sol will decrease, the curing reaction will not be promoted, and sufficient curing strength will be obtained. I can't do it. On the other hand, if the amount is more than 5.0% by mass, the curing reaction is extremely fast and an appropriate working pot life cannot be obtained. When the Mg component is added separately, for example, seawater magnesia, fused magnesia, heavy burnt magnesia, light burnt magnesia, carbonated magnesia, hydroxide magnesia, etc. can be used. Moreover, as the Ca component, in addition to alumina cement, for example, slaked lime, calcium carbonate, quicklime, etc. can be used separately, if necessary.

The dry powder alumina cement constituting the monolithic refractory for dry spraying of the present invention is used as a Ca component that causes a sol-gel reaction with silica sol as described above, but it also has rapid hardening, early strength, and fire resistance.・As a hydraulic cement with features such as heat resistance, acid resistance, and chemical resistance, it also functions as a useful binder for refractory base materials. Dry powder alumina cement hardens by reacting with the moisture in the silica sol. The monolithic refractory for dry spraying of the present invention must contain alumina cement in an amount of 1% by mass or more and 5% by mass or less based on 100% by mass of the refractory material.

The monolithic refractory for dry spraying of the present invention contains, in addition to silica sol and dry alumina cement, dry powder hydraulic alumina as a hardening agent at an external rate of 0.7% to 2% by mass relative to 100% by mass of the refractory material. It is characterized by containing within the range of .0% by mass. Hydraulic alumina is ρ-alumina, which is a type of intermediate alumina, and when water is added, a rehydration reaction occurs, causing particles to coagulate and harden. According to studies by the present inventors, dry powder hydraulic alumina is cured by reacting with moisture in silica sol, and can increase curing strength at room temperature after dry spraying. For example, in rotary kilns and the like where relatively stress is applied to the construction object, it is said that room temperature bending strength is required to be 1.0 MPa or more. On the other hand, when the amount of hydraulic alumina added to the dry powder is less than 0.7% by mass, for example, 0.6% by mass or less, the room temperature bending strength of the constructed body obtained using the dry sprayed monolithic refractory is is 1.0 MPa or less, making it difficult to use under the high stress conditions that the present invention aims at.

In addition to the above-described dry powder refractory material, dry powder alumina cement, silica sol, and hydraulic alumina that function as a binder for the refractory material, the dry-sprayed monolithic refractory of the present invention may contain, as necessary, appropriate materials. Flocculants, hardening modifiers, thickeners, fibers, etc. can be added. Examples of the curing regulator include at least one compound selected from the group consisting of condensed phosphates, organic acids, and organic acid salts. The curing modifier is preferably used in an amount of 0.01% by mass to 0.3% by mass based on 100% by mass of the refractory material. As the condensed phosphate, for example, sodium tripolyphosphate, sodium tetrapolyphosphate, sodium pyrophosphate, sodium hexametaphosphate, etc. can be used. For example, fireclay, bentonite, etc. can be used as the thickener.

By applying the dry spraying monolithic refractory of the present invention to the dry spraying construction method of the present invention as described below, it is possible to obtain a constructed body with higher curing strength than conventional products. Therefore, the monolithic refractory for dry spraying of the present invention can be suitably used for surfaces to be constructed that are subject to impact or external force, which have conventionally been difficult to apply by dry spraying. The dry spraying construction method of the present invention is characterized in that it is configured as follows when performing dry spraying construction by spraying the monolithic refractory from a spray nozzle onto the surface to be constructed. Specifically, the construction method of the present invention involves the use of refractory materials, alumina cement, and hydraulic alumina, all of which are dry powder, which are sent to a spray nozzle and which constitute the monolithic refractory for dry spraying of the present invention. By adding the silica sol defined by the present invention to the mixture, the monolithic refractory made of the above-mentioned material defined by the present invention is sprayed onto the work surface from the tip of the spray nozzle. do. More specifically, in the dry spraying construction method of the present invention, dry powder refractory material, alumina cement, and hydraulic alumina, which constitute the dry spraying monolithic refractory of the present invention, are mixed in advance and the mixed dry powder material is used. is sent to the spray nozzle. By adding the silica sol specified in the present invention to the dry powder mixture sent to this nozzle, the dry powder mixture and silica sol are kneaded in the nozzle, and the kneaded material is mixed with the silica sol. By spraying, a construction body made of the monolithic refractory for dry spraying of the present invention is formed.

In the dry spraying construction method of the present invention, silica sol is added to a dry powder mixture such as a fireproof material at the tip of the spray nozzle used to obtain the construction body of the dry spraying construction. Preferably, the kneaded product of the monolithic refractory for dry spraying is obtained within the tip of the nozzle. In this way, after obtaining the kneaded product of the monolithic refractory of the present invention, it becomes possible to immediately spray the monolithic refractory from the tip of the spray nozzle onto the surface to be constructed. The following curing reaction can occur in better conditions during the formation of the body. That is, as described above, by using the monolithic refractory for dry spraying of the present invention, adding silica sol to the dry powder materials in the nozzle, and then preferably spraying immediately after that, the following can be achieved. effect can be obtained. The resulting construction body is adhered by the hydraulic reaction caused by the water constituting the silica sol that occurs in dry powder alumina cement and hydraulic alumina, and by the hardening that occurs due to the rapid setting reaction between the silica sol and the calcium in the alumina cement. In addition to improving the properties and pot life during curing, the curing strength of the constructed body can be increased. As a result, by using the dry-sprayed monolithic refractories of the present invention, the shape of the construction body can be maintained even in applications where impact or external force is applied, which was difficult to use with conventional dry-sprayed monolithic refractories. Therefore, its versatility is improved and it is extremely useful industrially.

EXAMPLES Hereinafter, the present invention will be explained in more detail by giving Examples and Comparative Examples of the present invention. Tables 1 and 2 show the raw material formulations of Examples and Comparative Examples of the monolithic refractories for dry spraying of the present invention. Also shown in each table are the evaluation results obtained by evaluating each dry-sprayed monolithic refractory as described below. Hereinafter, "%" is based on mass unless otherwise specified.

[Examples 1 to 4, Comparative Examples 1 to 3] - Examination of the amount of silica sol added As the basic composition, dry powder, refractory material, alumina cement, and hydraulic alumina were used in the amounts shown in Table 1. The refractory material used as the base material is alumina having the particle size distribution shown in Table 1, mullite with a size under 0.075 mm that has been classified using a sieve with an opening of 0.075 mm, and silica flour with a size under 0.075 mm. there was. The alumina cement and hydraulic alumina used as hardening agents are hydraulic materials, and are hardened by the water content of the added silica sol to function as a binder for the refractory material. In the example in Table 1, the solid content concentration of the silica sol added to the above-mentioned dry powder basic formulation was changed as shown in Table 1, and each of the obtained monolithic refractories was used for dry spraying. This figure shows the evaluation results for each construction body formed.

Dry spraying is performed using a spray nozzle. The dry powder mixture obtained by pre-mixing the dry powder ingredients in the basic composition described above is sent to the nozzle, and silica sol is added at the tip of the nozzle. The kneaded mixture was then sprayed onto similar surfaces to be constructed to form construction bodies. As a result, as shown in Table 1, in the case of Comparative Examples 1 and 2 in which the solid content concentration of the silica sol used was 10% or 15%, in the case of Comparative Examples 1 and 2, in which the solid content concentration of the silica sol used was 20% or more, Examples 1 to Unlike the case of No. 4, the applied body was washed away and sufficient adhesion was not obtained. The reason for this is thought to be that when a silica sol with a solid content of less than 20% was used, a sufficient sol-gel reaction did not occur. In addition, when using the monolithic refractories of Comparative Examples 1 and 2 using silica sol with a solid content of less than 20%, the room temperature bending strength of the resulting construction body was 1.0 MPa or less, and Examples 1 to 2 were used. 4, it was found that the obtained constructed body did not exhibit sufficient curing strength as the objective of the present invention.

On the other hand, as in Comparative Example 3, when a silica sol with a high solid content of 60% is used as a component of a monolithic refractory for dry spraying, as shown in Table 1, a usable level of silica sol is used. Although a constructed body with adhesive properties can be obtained, the resulting constructed body has a short pot life, and during construction, the spray nozzle is likely to become clogged, resulting in a product with impaired workability. This means that if the solid content of the silica sol used exceeds 50%, the rapid setting will become too rapid and the workability will be poor, making it undesirable for practical use as a monolithic refractory for dry spraying. means. In addition, in this case, the room temperature bending strength of the constructed body obtained has sufficient curing strength of 1.0 MPa or more, as in the case of the example.

Each evaluation shown in Table 1 was performed by the following method and evaluated based on the following criteria.
<Room temperature bending strength of construction body>
After construction, the room temperature bending strength of the constructed body after curing for 24 hours was measured in accordance with JISR2575, and the curing strength of the constructed body was also determined. For dry sprayed refractories, it is said that the compressive strength after curing is 1.0 MPa or more as the curing strength necessary for de-framing, so the bending strength after 24 hours curing measured above ( Mpa) was 1.0 Mpa or more, it was considered as a pass. In the table, "○" indicates a pass, and "x" indicates a fail.

<Dry spraying workability>
1. Adhesion A spraying test was conducted using actual spraying equipment, and judgment was made based on whether a construction body with a predetermined thickness could be formed. If the adhesion is poor, the construction object will fall off or wash away before reaching the predetermined thickness. The results of the adhesion test of the construction body using the actual machine conducted as described above were evaluated based on the following criteria.
(Evaluation criteria)
◎: A construction body that reached a predetermined thickness was stably formed over the entire surface of the construction.
○: A construction body that reached a predetermined thickness was formed on the entire surface of the construction without causing any practical problems.
△: It was observed that the construction body fell off on a part of the construction surface before reaching the predetermined thickness.
×: The construction object fell off or washed away before reaching the predetermined thickness.

2. Pot life A spraying test was conducted using actual spraying equipment, and judgment was made based on whether the surface of the formed construction object could be shaped using a trowel or the like for a desired specified period of time. The pot life is determined as appropriate in consideration of the work involved, but in the above test, the pot life was set to the working time that is normally performed. The pot life test results for the construction bodies formed using the actual machine as described above were evaluated based on the following criteria.
(Evaluation criteria)
◎: The pot life of the formed construction body was necessary and sufficient for the specified time, and the shaping work could be performed in good condition.
○: The pot life of the formed construction body was sufficient for the specified time, and the shaping work could be performed without any practical problems.
△: Although the pot life of the formed construction body was sufficient for the specified time and the shaping work could be carried out without any practical problems, it was recognized that there were parts of the construction body with a short pot life. It was done.
×: The pot life of the formed construction body was short compared to the specified time, and the shaping work could not be performed sufficiently.

3. Nozzle clogging A spraying test was conducted using actual spraying equipment, and the clogging status of the spray nozzle was observed and judged based on the following criteria.
(Evaluation criteria)
○: Spraying was possible without clogging the nozzle.
Δ: Spraying work was carried out without any practical problems, but slight nozzle clogging was observed.
×: The nozzle was clogged and good spraying could not be performed.

[Examples 5 to 7, Comparative Examples 4 to 7] - Examination of the use and blending amount of hydraulic alumina As a basic blend, the amount of dry powder, refractory material and alumina cement, and the amount of silica sol added to these dry powder materials were similar. By changing the amount of hydraulic alumina externally added to the refractory material, various monolithic refractories for dry spraying were made. Specifically, as shown in Table 2, the same types of materials as in the example shown in Table 1 were used for the dry powder, refractory material, and alumina cement, and the same formulations were used. As for dry powder hydraulic alumina, it was not blended in Comparative Example 4, and in the other examples, it was used in a stepwise manner from 0.7% to 4% of the refractory material.

Using each of the monolithic refractories with the above formulations, the dry powder materials with the different formulations described above were kneaded in advance in the spray nozzle in the same way as in the previous study on silica sol. A mixture of dried powder was sent, and a silica sol having a similar concentration of silica solids was added at the nozzle tip to form a monolithic refractory, which was then sprayed onto the same surfaces to obtain construction bodies. The curing strength and workability of each of the obtained construction bodies were evaluated using the same method and criteria as in the previous study regarding the amount of silica sol. The results obtained are shown in Table 2.

As shown in Table 2, as a result of changing the amount of hydraulic alumina used in stages, the constructed body of Comparative Example 4, in which no hydraulic alumina was used, was compared to the constructed body of Comparative Example 5, in which 0.5% hydraulic alumina was used. It was confirmed that the adhesion was clearly inferior to that of the constructed body, and in this respect it was not suitable for practical use. Furthermore, from a comparison of the room temperature bending strength measured for the construction bodies obtained in Comparative Examples 4 and 5, it was found that even if the amount of hydraulic alumina used is small, the curing strength of the construction bodies tends to improve. I found out. However, as shown in Comparative Example 5, when the amount of hydraulic alumina externally added to the base material of the fireproof material is as small as 0.5% or less, it cannot be said that the amount used is sufficient, and the room temperature bending strength is increased. The strength was 1.0 MPa or less, and it was confirmed that the sufficient curing strength targeted by the present invention could not be achieved. On the other hand, as shown in Comparative Examples 6 and 7, when the external addition amount of hydraulic alumina is increased to 3% or more, a construction body with sufficient curing strength can be obtained, but the workability may be significantly impaired. Understood. This is considered to be because when the amount of externally added hydraulic alumina is increased to 3% or more, the curing speed becomes too fast, resulting in a significant decrease in workability.

The monolithic refractory for dry spraying of the present invention is useful as a monolithic refractory for dry spraying during new construction and repair within the range where all monolithic refractories can be applied to waste incinerators, cement manufacturing equipment, rotary kilns, etc. It is expected that it will be utilized.

Claims (6)

A monolithic refractory for dry spraying used in a state containing a dry powder refractory material, a dry powder alumina cement as a hardening agent, and a silica sol having a silica solid content concentration of 20% by mass or more and 50% by mass or less, ,
Containing the alumina cement in an amount of 1% by mass or more and 5% by mass or less, based on 100% by mass of the refractory material,
The silica sol is contained within a range in which the silica solid content contained in the silica sol is 3% by mass or more and 30% by mass or less, multiplied by 100% by mass of the refractory material,
Further, the monolithic refractory for dry spraying is characterized in that it contains dry powder hydraulic alumina in an amount of 0.7% by mass or more and 2.0% by mass or less, based on 100% by mass of the refractory material. thing. The dry method according to claim 1, wherein the room temperature bending strength of the "room temperature curing cured product of a monolithic refractory" which is a construction body obtained by dry spraying construction in which the monolithic refractory for dry spraying is sprayed from the tip of a nozzle is 1.0 MPa or more. Monolithic refractories for spraying. The dry spraying material according to claim 1 or 2, wherein the refractory material has an alumina raw material as a main component and has a fine particle component with a particle size of 0.075 mm or less in a range of 15% by mass or more and 50% by mass or less. Shaped refractories. Furthermore, based on 100% by mass of the fireproof material, at least one compound selected from the group consisting of condensed phosphates, organic acids, and organic acid salts is added in an amount of 0.01% by mass or more to 0.3% by mass. The monolithic refractory for dry spraying according to claim 1 or 2, comprising within the following range. A construction method in which dry spraying is performed by spraying the monolithic refractory for dry spraying according to claim 1 or 2 onto a construction target surface from a spray nozzle,
A dry powder mixture obtained by pre-mixing the dry powder refractory material, the dry powder alumina cement, and the dry powder hydraulic alumina is sent to the spray nozzle, the silica sol is added and kneaded, and the kneaded material is sprayed. A dry spraying construction method characterized by spraying the monolithic refractory for dry spraying onto a construction target surface from the tip of a nozzle. The dry spray construction method according to claim 5, wherein the addition of the silica sol is performed at the tip of the spray nozzle.