Method for installing thermal insulation lining and method for manufacturing skid pipes

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 a heat insulation lining for covering a cooling member, a method for constructing the heat insulation lining, and a skid pipe.

Background Art

[0002] In the hot rolling process in a steel mill, a steel slab is heated using a heating furnace and then rolled to produce a thin plate. In the heating furnace used in the hot rolling process, a table for placing the steel slab called a skid is installed to transport the steel slab from the charging side to the discharging side. The skid is equipped with a skid pipe called a beam or a post. The steel slab is placed on the upper part of the skid pipe, and the skid moves up, down, left, and right to transport the steel slab. The skid pipe pipe has a water-cooled pipe as a cooling member. The water-cooled pipe is a tubular member through which cooling water flows inside. Part of the energy input into the heating furnace when heating the steel slab is also transmitted to the cooling water flowing inside the water-cooled pipe. Therefore, a heat insulation lining having high heat insulation is constructed around the water-cooled pipe.

[0003] As a method for constructing a heat insulation lining having high heat insulation, a dry spraying construction method of spraying a spraying material onto a construction surface is known. For example, Patent Document 1 discloses a dry spraying construction method in which a powder-shaped refractory raw material is pumped to a nozzle part and water is added at the nozzle part and sprayed onto a construction surface.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, applying the above insulation lining construction method to skid pipes results in the following problems.

[0006] In the dry spray application method described in Patent Document 1, the powder and water are mixed at the nozzle, which tends to result in uneven mixing. This leads to a problem where a large amount of dust is generated and rebound loss increases when spraying onto the water-cooled pipe. On the other hand, if the powder and water are mixed and then pumped to the nozzle, problems such as clogging of the powder-water mixture before reaching the nozzle may occur, potentially worsening workability.

[0007] The present invention was made to solve the above-mentioned problems of the prior art, and its purpose is to provide an insulating lining, an insulating lining application method, and a skid pipe that can reduce rebound loss without worsening workability during spraying. [Means for solving the problem]

[0008] The thermal insulation 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 granules, which are obtained by adding water to a refractory raw material, a flocculant and a curing accelerator, toward the cooling member. [2] In the above [1], the granules are an insulating lining having a water content of 5 to 10 parts by mass on the outside, with respect to 100 parts by mass of refractory raw material. [3] In the above [1], the refractory raw material is an insulating lining containing one or more selected from Al2O3, SiO2, MgO and CaO. [4] In the above [3], the heat insulating lining is wherein the particle size of the refractory raw material is less than 5 mm. [5] In the above [1], the granules are an insulating lining in which the contact angle for evaluating the wettability of the granules is less than 90°.

[0010] The method for constructing the thermal insulation 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 water to a refractory raw material, a flocculant and a hardening accelerator to granulate, 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] The thermal insulation lining described in any one of [1] to [5] above is a skid pipe formed in an annular structure around the cooling member. [Effects of the Invention]

[0012] According to the present invention, a granular material containing water is produced by adding water to a refractory raw material, a flocculant, and a hardening accelerator and then granulating the mixture. By using a granular material produced by adding water in this way, it becomes unnecessary to add water to the granular material immediately before spraying, and rebound loss can be reduced compared to when water is added to the granular material immediately before spraying. In addition, because the granular material is in granular form, the risk of the granular material clogging the nozzle before it reaches the nozzle during pumping is reduced, and deterioration of workability during spraying can be suppressed. [Brief explanation of the drawing]

[0013] [Figure 1] This is a diagram showing the cross-sectional structure of an insulating lining according to one embodiment of the present invention. [Figure 2] This is an explanatory diagram showing the method for installing the thermal insulation lining according to the above embodiment. [Figure 3] This is an explanatory diagram for evaluating the wettability of granulated material when it adheres to the surface of a component. [Modes for carrying out the invention]

[0014] Hereinafter, the heat insulation lining according to this embodiment will be described. <Heat insulation lining> The heat insulation lining according to an embodiment of the present invention is a heat insulation lining covering the outer surface of a cooling member, and includes a sprayed refractory layer formed by spraying a granulated product obtained by adding water to a refractory raw material, an aggregating agent, and a curing accelerator toward the cooling member.

[0015] The heat insulation lining in this embodiment is for protecting a cooling member (hereinafter referred to as a water-cooled pipe) provided in a heating furnace. In the water-cooled pipe, cooling water with a temperature of about 40 to 50°C is flowing as a cooling medium.

[0016] As shown in FIG. 1, the heat insulation lining is provided so as to cover the outer periphery of a water-cooled pipe having a plurality of support members protruding from its outer peripheral surface. The heat insulation lining of this embodiment consists of only one layer of sprayed refractory layer. The sprayed refractory layer is formed by spraying a granular granulated product toward the water-cooled pipe.

[0017] Here, the granulated product to be sprayed is produced by adding water to a refractory raw material, an aggregating agent, a curing accelerator, and a binder as an optional additive, and granulating. The granulated product preferably has a water content of 5 to 10 parts by mass in excess with respect to 100 parts by mass of the refractory raw material.

[0018] Since the heat-insulating lining has a structure with many voids, unlike refractory materials, rebound loss is likely to occur when the water content is low compared to refractory materials. Therefore, when spraying towards the water-cooled pipe, if the water content of the sprayed granulated material is less than 5 parts by mass, the amount of water is small, and when sprayed, it does not adhere to the water-cooled pipe and the amount that becomes rebound loss increases as it falls. On the other hand, if the water content exceeds 10 parts by mass, not only is the risk of clogging during pressure feeding high due to too much water content, but also the amount of water evaporated during drying increases. Therefore, after drying, the porosity increases and densification does not occur, so there is a high risk that the bending strength and compressive strength will also decrease and the durability will be inferior. Therefore, the water content is preferably 5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the refractory raw material externally.

[0019] Note that the water content of the sprayed granulated material is adjusted by the amount of water added during granulation. Thus, by setting the water content of the sprayed granulated material 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 the rebound loss can be reduced. Also, by increasing the adhesion rate between the sprayed granulated materials, it becomes possible to stack them to the desired thickness without peeling off the sprayed granulated materials.

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

[0021] Also, regarding the rebound loss, the adhesion of the granulated material on the surface of the member was examined from the perspective of wettability. Fig. 3 shows the solid surface tension γ S and the liquid surface tension γ L and the contact angle θ of the liquid, and the interfacial tension γ SLThis is an explanatory diagram illustrating the relationship. Evaluation of the adhesion of the granules showed that the contact angle θ was 40.6° under condition (a) and 76.8° under condition (b), indicating no problems with wettability. Under condition (c), the contact angle θ was 105.5°, indicating a problem with wettability. Rebound loss was 15% under condition (a), 20% under condition (b), and 30% under condition (c). Therefore, it was found that the smaller the contact angle θ is (less than 90°), the better the wettability and the less rebound loss there is when spraying. Consequently, to keep the rebound loss below 25% when the granules adhere to the water-cooled pipe, it is preferable that the contact angle θ used to evaluate the wettability of the granules is less than 90°.

[0022] By using such granules, the thickness of the sprayed refractory layer constituting the insulating lining (the layer thickness of the granules) can be made 50 mm or more, and the water-cooled pipes can be sufficiently insulated by a single layer of sprayed refractory material.

[0023] While known refractory raw materials can be used, it is preferable to include one or more selected from Al2O3, SiO2, MgO, and CaO, and more preferably to include all four: Al2O3, SiO2, MgO, and CaO. By using these four types as refractory raw materials, the range of composition and physical properties is broadened compared to cases where the refractory raw materials consist of one or two types, increasing versatility, as well as improving heat resistance, slag erosion resistance, and mechanical strength.

[0024] Furthermore, it is preferable that the particle size of the aggregate in the refractory raw material is less than 5 mm. By making the particle size of the refractory raw material constituting the sprayed granules less than 5 mm, rebound loss when spraying the granules can be reduced. Here, particle size refers to the maximum particle size of the aggregate. For example, a sieve with a mesh size of 5 mm can be used.

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

[0026] Examples of flocculants include alumina cement. Examples of hardening accelerators include alumina cement hydrate, lithium carbonate, and alkali metal hydroxides. Examples of optional binders include alumina cement. It is preferable that the total amount of flocculant and hardening accelerator added externally is 5 to 11 parts per 10

[0027] In the above embodiment, the thermal insulation lining was composed of only one sprayed refractory layer, but other thermal insulation layers may also be provided. Specifically, for example, one sprayed refractory layer may be provided on the outside of the water-cooling pipe, a thermal insulation layer made of a microporous thermal insulation sheet may be provided on the outside of that, and another sprayed refractory layer may be provided on the outside of that thermal insulation layer. In this way, by composing the thermal insulation layer with two or more layers and sandwiching the microporous thermal insulation sheet from both sides with sprayed refractory layers, the thermal insulation performance of the thermal insulation layer can be enhanced while protecting the microporous thermal insulation sheet.

[0028] Furthermore, even when the thermal insulation lining is formed of two or more insulation layers, it is preferable that at least 50% of the total thickness of the thermal insulation lining is composed of a sprayed refractory layer, and more preferably 80% or more is composed of a sprayed refractory layer. By making the majority of the thermal insulation lining a sprayed refractory layer, the construction efficiency of the thermal insulation lining can be increased.

[0029] Next, the method for installing the thermal insulation lining according to this embodiment will be described. <Installation method for thermal insulation lining> The method for applying the heat insulating lining according to this embodiment involves adding water to a refractory raw material, a flocculant, and a hardening accelerator to granulate the material, and then spraying the granulated material toward a cooling member to form a sprayed refractory layer on the outer circumference of the cooling member.

[0030] When applying the thermal insulation lining, as shown in Figure 2, a dry sprayer is used to spray the granulated material toward the water-cooled pipe using air pressure, forming a sprayed refractory layer on the outside of the water-cooled pipe. The granulated material used is one which has been pre-granulated by adding water to refractory raw materials, a flocculant and a hardening accelerator, and optionally a binder. The granulation method of the granulated material is not particularly limited, and it can be granulated using a known granulator such as a rotary drum.

[0031] In typical dry spray application methods, unhumidified powder is compressed with air to the nozzle, where it is mixed with water and then sprayed. However, in this embodiment, since granulated material with added water is used, there is no need to mix the powder and water immediately before spraying, and the granulated material can be sprayed directly towards the water-cooled pipe.

[0032] In other words, since the refractory raw materials and water can be thoroughly mixed in advance during granulation, this embodiment is not affected by the amount of water added during spraying, compared to the conventional method in which water is added to the powder immediately before spraying, and the amount of dust generated is also reduced, and rebound loss can be reduced.

[0033] The above-described insulating lining can be applied to skid pipes installed in heating furnaces. High thermal insulation is required around water-cooled pipes, and by forming the insulating lining according to this embodiment in an annular structure around the water-cooled pipe, a skid pipe with high thermal insulation can be obtained. [Examples]

[0034] The effects of this embodiment will be described in detail below based on the examples, but the present invention is not limited to these examples. As an example of this embodiment, in the case of an insulating lining for a water-cooled pipe installed in a heating furnace, the optimal specifications for the spraying method were investigated, assuming that the insulating lining consists of one layer and has a total thickness of 100 mm.

[0035] First, for Test No. 1-1, a granulated material was prepared by adding water to refractory raw materials, a coagulant, and a hardening accelerator and then granulating them. For Test No. 1-2, an ungranulated material was prepared by not adding water and granulating it. For the granulated material in Test No. 1-1, the material was sprayed directly from the nozzle of a dry spraying machine without mixing in any mixing water. For the ungranulated material in Test No. 1-2, the material was sprayed after mixing in any mixing water from the nozzle, 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 was 15% when granulated material was sprayed, while in Test No. 1-2, the rebound loss was 30% when ungranulated material was sprayed.

[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 Tests No. 2-2 to 2-4, when the moisture content of the granulated material was between 5 parts by mass and 10 parts by mass, the rebound loss could be suppressed to 25% or less, and the granules could be pumped without clogging.

[0038] Furthermore, the adhesion rate between granules increased, allowing the granules to be layered to the specified thickness without peeling. On the other hand, as in Test No. 2-1, when the moisture content was less than 5 parts by mass, the moisture content was too low, resulting in a decrease in the adhesion rate of the sprayed granules and a rebound loss exceeding 25%. Also, as in Test No. 2-5, when the moisture content exceeded 10 parts by mass, the moisture content was too high, causing clogging when the granules were pumped, and significantly increasing the porosity of the sprayed material, preventing densification. Increasing the air pressure was necessary to resolve this clogging, which increased costs compared to other test conditions.

[0039] Furthermore, the composition of the refractory raw materials used as granules was investigated. The results are shown in Table 3. As in Test No. 1-1, when the refractory raw materials consisted of four types: Al2O3, SiO2, MgO, and CaO, the compressive strength and flexural strength of the sprayed refractory layer were high. As in Tests No. 3-1 to 3-4, when the refractory raw materials consisted of any three of Al2O3, SiO2, MgO, and CaO, the compressive strength and flexural strength were slightly lower compared to Test No. 1-1. As in Tests No. 3-5 to 3-6, when the refractory raw materials consisted of two types, the compressive strength and flexural strength were further lower compared to Test No. 1-1.

[0040] Next, we investigated the maximum particle size of the aggregate used as the refractory raw material for the granulated material. The results are shown in Table 4. As in Test No. 4-1, when the maximum aggregate particle size was 5 mm or more, the rebound loss increased compared to when the maximum aggregate particle size 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 spraying machine (air) 6. Granulated materials 7. Nozzle section θ contact angle γ S Surface tension of solids γ L surface tension of liquids γ SL Interfacial tension between solids and liquids

Claims

1. A method for installing an insulating lining that covers the outer circumference of a cooling component, In the process of adding water to refractory raw materials, a flocculant, 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 circumference of the cooling member, The aforementioned granules have a moisture content of 5 to 10 parts by mass when applied externally, relative to 100 parts by mass of refractory raw material, in a method for constructing an insulating lining.

2. The aforementioned refractory raw material is Al ２ O ３ SiO ２ A method for constructing an insulating lining according to claim 1, comprising one or more selected from MgO and CaO.

3. The method for installing the thermal insulation lining according to claim 2, wherein the particle size of the refractory material is less than 5 mm.

4. The method for installing an insulating lining according to claim 1, wherein the granules have a contact angle of less than 90° for evaluating the wettability of the granules.

5. A method for manufacturing a skid pipe, comprising forming an annular thermal insulation lining around the cooling member using the method for constructing a thermal insulation lining according to any one of claims 1 to 4.

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