Heat insulation lining, heat insulation lining construction method, and skid pipe

Abstract

To provide a heat insulation lining, a heat insulation lining construction method, and a skid pipe which can reduce a rebound loss without deteriorating constructability upon spraying.SOLUTION: There is disclosed a heat insulation lining which covers an outer face of a cooling member and comprises a sprayed refractory layer formed by spraying a granulated substance obtained by adding moisture to a refractory raw material, a flocculant and a curing accelerator and granulating the same toward the cooling member. The granulated substance preferably has a moisture content of 5 or more to 10 pts.mass or less to 100 pts.mass of the refractory raw material in outer percentage. Further, the refractory raw material preferably includes one or more kinds selected from Al2O3, SiO2, MgO, and CaO. The grain size of the refractory raw material is preferably less than 5 mm. In the granulated substance, a contact angle evaluating the wettability of the granulated substance is preferably less than 90°.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an insulating lining for covering a cooling member, a method for applying the insulating lining, and a skid pipe. [Background technology]

[0002] In the hot rolling process in steelworks, a heating furnace is used to heat steel slabs and roll them to produce thin plates. In the heating furnaces used in the hot rolling process, a platform called a skid is installed to carry the steel slab from the charging side to the discharging side. The skid is equipped with a skid pipe called a beam or post, and the steel slab is placed on the top of the skid pipe, and the skid moves up and down and left and right to transport the steel slab. The skid pipe has a water-cooled pipe as a cooling member. The water-cooled pipe is a tubular member through which cooling water flows. Part of the energy input to the heating furnace when heating the steel slab is also transferred to the cooling water flowing inside the water-cooled pipe. For this reason, a heat-insulating lining with high thermal insulation properties is installed around the water-cooled pipe.

[0003] As a method for applying a heat insulating lining having high heat insulating properties, a dry spraying application method in which a spraying material is sprayed onto an application surface is known. For example, Patent Document 1 discloses a dry spraying application method in which a powdered refractory raw material is pressure-fed to a nozzle, water is added at the nozzle, and the powder is sprayed onto an application surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2000-356475 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when attempting to apply the above-mentioned heat insulating lining construction method to a skid pipe, the following problems arise.

[0006] In the dry spraying method described in Patent Document 1, the powder and water are mixed in the nozzle, which tends to cause uneven mixing of the powder and water, resulting in issues such as a large amount of dust being generated and increased rebound loss when sprayed onto a water-cooled pipe. On the other hand, if the powder and water are mixed and then pumped to the nozzle, problems such as the mixture of powder and water clogging just before the nozzle can occur, which can worsen workability.

[0007] The present invention has been made to solve the above-mentioned problems associated with the conventional technology, and an object of the present invention is to provide an insulating lining, an insulating lining application method, and a skid pipe that can reduce rebound loss without deteriorating the ease of application during spraying. [Means for solving the problem]

[0008] The insulating lining according to the present invention, which advantageously solves the above problems, is configured as follows.

[0009] [1] An insulating lining covering the outer surface of a cooling member, comprising a sprayed refractory layer formed by spraying a granulated material obtained by adding moisture to a refractory raw material, a coagulant, and a hardening accelerator toward the cooling member. [2] In the above [1], the granules are a heat insulating lining having a moisture content of 5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the refractory raw material. [3] In the above [1], the refractory raw material is a heat insulating lining containing one or more selected from Al2O3, SiO2, MgO and CaO. [4] The insulating lining according to [3] above, wherein the particle size of the refractory raw material is less than 5 mm. [5] In the above [1], the granulated material is a heat insulating lining having a contact angle, which is used to evaluate the wettability of the granulated material, of less than 90°.

[0010] The method for installing a heat insulating lining according to the present invention, which advantageously solves the above problems, is configured as follows. [6] A method for applying an insulating lining to cover the outer periphery of a cooling member, comprising adding moisture to a refractory raw material, a coagulant, and a hardening accelerator to granulate them, and then spraying the granulated material toward the cooling member to form a sprayed refractory layer on the outer periphery of the cooling member.

[0011] The skid pipe according to the present invention, which advantageously solves the above problems, is configured as follows. [7] A skid pipe in which the insulating lining according to any one of [1] to [5] above is formed in an annular structure around the cooling member. Effect of the Invention

[0012] According to the present invention, a granulated material containing moisture is prepared by adding moisture to the refractory raw material, the coagulant, and the hardening accelerator and granulating them. By using the granulated material granulated by adding moisture in this way, it is not necessary to add water to the granulated material immediately before spraying, and rebound loss can be reduced compared to the case where water is added to the granulated material immediately before spraying. In addition, since the granulated material is granular, the risk of the granulated material clogging in front of the nozzle when pumped is reduced, and deterioration of workability during spraying can be suppressed. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a configuration diagram showing a cross-sectional structure of a heat insulating lining according to one embodiment of the present invention. [Diagram 2] FIG. 4 is an explanatory diagram showing a method of applying the insulating lining according to the embodiment. [Diagram 3] FIG. 1 is an explanatory diagram for evaluating wettability when a granulated material adheres to a surface of a member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The insulating lining according to this embodiment will be described below. <Thermal insulation lining> The insulating lining according to one embodiment of the present invention is an insulating lining that covers the outer surface of a cooling member, and includes a sprayed refractory layer formed by spraying a granulated material obtained by adding moisture to refractory raw materials, a coagulant, and a hardening accelerator toward the cooling member.

[0015] The insulating lining in this embodiment is intended to protect a cooling member (hereinafter, referred to as a water-cooled pipe) installed in the heating furnace. Cooling water with a temperature of about 40 to 50° C. flows in the water-cooled pipe as a cooling medium.

[0016] As shown in Fig. 1, the insulating lining is provided so as to cover the outer periphery of the water-cooled pipe having a plurality of supporting members protruding from its outer periphery. The insulating lining of this embodiment is made of only one sprayed refractory layer. The sprayed refractory layer is formed by spraying granular granulated material against the water-cooled pipe.

[0017] The granulated material to be sprayed is prepared by adding moisture to the refractory raw material, the coagulant, the hardening accelerator, and the binder as an optional additive, and granulating the mixture. The granulated material preferably has a moisture content of 5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the refractory raw material.

[0018] Unlike refractories, the insulating lining has a structure with many voids, so rebound loss is likely to occur when the moisture content is low compared to refractories. Therefore, when spraying toward the water-cooled pipe, if the moisture content of the granulated material to be sprayed is less than 5 parts by mass, the moisture content is low, and the amount of rebound loss caused by falling without adhering to the water-cooled pipe when sprayed increases. On the other hand, if the moisture content is more than 10 parts by mass, the moisture content is too high, and there is a high risk of clogging during pressure feeding, and the amount of moisture evaporated during drying increases. Therefore, after drying, the porosity increases and the densification does not occur, so the bending strength and compressive strength also decrease, and there is a high risk of poor durability. Therefore, the moisture content is preferably 5 parts by mass or more and 10 parts by mass or less, based on 100 parts by mass of the refractory raw material.

[0019] The moisture content of the granulated material to be sprayed is adjusted by the amount of water added during granulation. In this way, by setting the moisture content of the granulated material to be sprayed to 5 parts by mass or more and 10 parts by mass or less, the adhesion rate of the sprayed material to the water-cooled pipe can be increased without deteriorating the workability, and rebound loss can be reduced. In addition, by increasing the adhesion rate between the granulated material to be sprayed, it is possible to layer the granulated material to the desired thickness without peeling off.

[0020] Specifically, it is preferable to adjust the moisture content of the granulated material so that the rebound loss when the granulated material is sprayed against a water-cooled pipe is 25% or less.

[0021] In addition, the rebound loss was examined from the viewpoint of wettability of the granulated material on the surface of the component. Figure 3 shows the relationship between the surface tension of the solid γ S and the surface tension of the liquid γ L , the contact angle of the liquid θ, and the interfacial tension between the solid and the liquid γ SLFIG. 1 is an explanatory diagram showing the relationship between the contact angle θ and the wettability. As a result of evaluating the adhesion of the granulated material, the contact angle θ was 40.6° under condition (a) and 76.8° under condition (b), which showed no problem with wettability. Under condition (c), the contact angle θ was 105.5°, which showed a problem with wettability. The rebound loss was 15% under condition (a), 20% under condition (b), and 30% under condition (c). Thus, it was found that the wettability was better and the rebound loss at the time of spraying could be reduced as the contact angle θ was smaller than 90°. Therefore, when the granulated material adheres to the water-cooled pipe, in order to keep the rebound loss at 25% or less, it is preferable that the contact angle θ for evaluating the wettability of the granulated material is less than 90°.

[0022] By using such granules, the thickness of the sprayed refractory layer that constitutes the insulating lining (the layered thickness of the granules) can be made 50 mm or more, and the water-cooled pipe can be sufficiently insulated by only one sprayed refractory layer.

[0023] As the refractory raw material, any known refractory raw material can be used, but it is preferable that the refractory raw material contains one or more selected from Al2O3, SiO2, MgO, and CaO, and it is more preferable that the refractory raw material contains the four types of Al2O3, SiO2, MgO, and CaO. By using the above four types as the refractory raw material, the range of composition and physical property values ​​is broadened compared to a case where the refractory raw material is composed of one or two types, and the versatility is expanded, and the heat resistance, slag melting resistance, and mechanical strength are improved.

[0024] In addition, the particle size of the aggregate of the refractory raw material is preferably less than 5 mm. By making the particle size of the refractory raw material constituting the granulated material to be sprayed less than 5 mm, rebound loss when the granulated material is sprayed can be reduced. Here, the particle size refers to the maximum particle size of the aggregate. For example, a sieve with an opening of 5 mm can be used.

[0025] Furthermore, it is preferable that the refractory raw material contains fine particles in addition to the aggregate having a particle size of less than 5 mm. Examples of the fine particles include silica fine particles (SiO2) or dolomite fine particles (MgO, CaO) having a particle size of less than 0.2 mm. In this way, by containing the fine particles in the refractory raw material, rebound loss when spraying the granulated material can be reduced compared to a configuration in which the refractory raw material contains only aggregate.

[0026] Examples of the flocculant include alumina cement. Examples of the hardening accelerator include alumina cement hydrate, lithium carbonate, and alkali metal hydroxide. Examples of the binder that is added optionally include alumina cement. The total amount of the flocculant and hardening accelerator is preferably 5 parts by mass or more and 11 parts by mass or less per 100 parts by mass of the refractory raw material.

[0027] In the above embodiment, the insulating lining is formed of only one sprayed refractory layer, but an insulating layer other than the sprayed refractory layer may be provided. Specifically, for example, a sprayed refractory layer may be provided on the outside of the water-cooled pipe, an insulating layer made of a microporous insulating sheet may be provided on the outside of that, and another sprayed refractory layer may be provided on the outside of that insulating layer. In this way, by forming the insulating layer with two or more layers and sandwiching the microporous insulating sheet between the sprayed refractory layers on both sides, it is possible to improve the insulating performance of the insulating layer while protecting the microporous insulating sheet.

[0028] Even when the insulating lining is formed of two or more insulating layers, it is preferable that at least 50% of the total thickness of the insulating lining is composed of the sprayed refractory layer, and more preferably 80% or more of the total thickness of the insulating lining is composed of the sprayed refractory layer. By forming most of the insulating lining from the sprayed refractory layer, the construction efficiency of the insulating lining can be improved.

[0029] Next, a method for applying the insulating lining according to this embodiment will be described. <How to install the heat insulating lining> The method for constructing the insulating lining according to this embodiment involves adding moisture to refractory raw materials, a flocculant, and a hardening accelerator to granulate them, and then spraying the granulated material toward a cooling member to form a sprayed refractory layer on the outer periphery of the cooling member.

[0030] When applying the heat insulating lining, as shown in Fig. 2, the granulated material is sprayed toward the water-cooled pipe by air pressure using a dry spraying machine to form a sprayed refractory layer on the outside of the water-cooled pipe. The granulated material is prepared by adding water to the refractory raw material, aggregating agent, hardening accelerator, and optionally a binder, and granulating the material in advance. There are no particular limitations on the granulation method for the granulated material, and the granulated material is granulated, for example, using a known granulator such as a rotating drum.

[0031] In a typical dry spraying method, unhumidified powder is compressed by air to a nozzle, where the powder is mixed with water and sprayed. However, in this embodiment, a granulated material to which moisture has been added is used, so there is no need to mix the powder with water just before spraying, and the granulated material can be sprayed directly toward the water-cooled pipe.

[0032] In other words, since the refractory raw material and water can be mixed sufficiently in advance during granulation, the present embodiment is not affected by the amount of water added at the time of spraying, generates less dust, and can reduce rebound loss, compared to the conventional method in which water is added to the powder immediately before spraying.

[0033] The above-mentioned insulating lining can be applied to a skid pipe installed in a heating furnace. High insulation is required around the water-cooled pipe, and by forming the insulating lining according to this embodiment in a ring structure around the water-cooled pipe, a skid pipe with high insulation can be obtained. EXAMPLES

[0034] The effects of this embodiment will be specifically described below based on examples, but the present invention is not limited to these examples. As an example of this embodiment, the optimum specifications for the spraying method were examined for the insulating lining of a water-cooling pipe installed in a heating furnace, with the insulating lining consisting of one layer and having a total thickness of 100 mm.

[0035] First, for Test No. 1-1, granulated material was prepared by adding water to the refractory raw materials, coagulant, and hardening accelerator. For Test No. 1-2, ungranulated material was prepared without adding water to granulate. For the granulated material in Test No. 1-1, it was sprayed as is without mixing with mixing water in the nozzle of the dry spraying machine. For the ungranulated material in Test No. 1-2, it was mixed with mixing water in the nozzle and sprayed, and the amount of rebound loss after spraying was compared.

[0036] The results are shown in Table 1. In Test No. 1-1, the rebound loss amount when granulated material was sprayed was 15%, while in Test No. 1-2, the rebound loss amount when ungranulated material was sprayed was 30%.

[0037] Next, the moisture content of the granulated material was examined. The results are shown in Table 2. As shown in Test No. 1-1 and Test Nos. 2-2 to 2-4, when the moisture content of the granulated material was 5 parts by mass or more and 10 parts by mass or less, the rebound loss amount could be suppressed to 25% or less, and the granulated material could be pumped without clogging.

[0038] Furthermore, the adhesion rate between the granulated materials increased, so that the granulated materials could be laminated to a specified thickness without peeling off. On the other hand, when the moisture content was less than 5 parts by mass, as in Test No. 2-1, the moisture content was too low, so the adhesion rate of the granulated materials when sprayed decreased, and the rebound loss amount exceeded 25%. When the moisture content was more than 10 parts by mass, as in Test No. 2-5, the moisture content was too high, so clogging occurred when the granulated materials were pumped, and the porosity of the spray material increased significantly, preventing densification. In order to eliminate this clogging, it was necessary to increase the air pressure, which increased costs compared to other test conditions.

[0039] Furthermore, the components of the refractory raw material used as the granules were examined. The results are shown in Table 3. When the components of the refractory raw material were four types, Al2O3, SiO2, MgO, and CaO, as in Test No. 1-1, the compressive strength and bending strength of the sprayed refractory layer were high. When the components of the refractory raw material were three types, Al2O3, SiO2, MgO, and CaO, as in Test No. 3-1 to 3-4, the compressive strength and bending strength were slightly lower than those of Test No. 1-1. When the components of the refractory raw material were two types, as in Test No. 3-5 to 3-6, the compressive strength and bending strength were further lower than those of Test No. 1-1.

[0040] Next, the maximum particle size of the refractory raw material used as the granules was examined. The results are shown in Table 4. When the maximum particle size of the aggregate was set to 5 mm or more, as in Test No. 4-1, the amount of rebound loss increased compared to when the maximum particle size of the aggregate was less than 5 mm.

[0041] [Table 1]

[0042] [Table 2]

[0043] [Table 3]

[0044] [Table 4] [Explanation of symbols]

[0045] 1 Water cooling pipe 2. Sprayed refractory layer 3 Support material 4 Cooling water 5 Dry spray machine (air) 6 Granulated materials 7 Nozzle section θ contact angle Gamma S Surface tension of solids Gamma L Surface tension of liquids Gamma SL Interfacial tension between solids and liquids

Claims

1. A thermal insulating lining covering an outer surface of a cooling member, The insulating lining includes a sprayed refractory layer formed by spraying a granulated material obtained by adding moisture to a refractory raw material, a flocculating agent, and a hardening accelerator toward the cooling member.

2. 2. The insulating lining according to claim 1, wherein the granules have a moisture content of 5 parts by mass or more and 10 parts by mass or less based on 100 parts by mass of the refractory raw material.

3. The refractory raw material is Al ２ O ３ , SiO ２ 2. The insulating lining according to claim 1, further comprising at least one selected from the group consisting of SiO, MgO and CaO.

4. 4. The insulating lining of claim 3, wherein the particle size of the refractory raw material is less than 5 mm.

5. The insulating lining according to claim 1 , wherein the granulated material has a contact angle, which evaluates the wettability of the granulated material, of less than 90°.

6. A method for applying a heat insulating lining to cover an outer periphery of a cooling member, comprising the steps of: A method for constructing an insulating lining, comprising adding moisture to a refractory raw material, a flocculant and a hardening accelerator to granulate the refractory raw material, and then spraying the granulated material toward the cooling member to form a sprayed refractory layer on the outer periphery of the cooling member.

7. A skid pipe, comprising an insulating lining according to any one of claims 1 to 5 formed in an annular configuration around the cooling member.

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