Coke oven lubricant

Abstract

To provide a lubricant for a coke oven, which can suppress damage to fused siliceous precast blocks and silica bricks in a coke oven in which a combustion chamber is constructed from the fused siliceous precast blocks, and a furnace top portion above the combustion chamber and a heat storage chamber below the combustion chamber are constructed from the silica bricks.SOLUTION: There is provided a lubricant for a coke oven. The lubricant contains 91 mass% or more and 95 mass% or less of spherical alumina particles, and 5 mass% or more and 9 mass% or less of organic glue. A particle size structure of the alumina particles is configured in that: a ratio of coarse particles with a particle size of 0.5 mm or more and less than 1 mm is 70 mass% or more and 80 mass% or less; a ratio of medium-coarse particles with a particle size of 0.3 mm or more and less than 0.5 mm is 10 mass% or more and 20 mass% or less; and a ratio of fine particles with a particle size of less than 0.070 mm is 10 mass% or more and 20 mass% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a coke oven lubricant used in a coke oven. [Background technology]

[0002] A coke oven has a heat regenerator, a combustion chamber, and a carbonization chamber provided above the heat regenerator, and is configured such that the carbonization chambers that convert coal into coke and the combustion chambers that supply heat to the carbonization chambers are arranged alternately. A coke oven is a facility that supplies heat from the combustion chamber to the carbonization chamber using heat transfer from bricks, and carbonizes the coal in the carbonization chamber to produce coke. In the following specification, the "combustion chamber and carbonization chamber" will be collectively referred to simply as the "combustion chamber." The same applies in the claims. In addition, in the present invention, the "heat regenerator" is considered to include the "bellows portion."

[0003] In recent years, in order to simplify the construction of coke ovens, a construction method of constructing a combustion chamber using large precast blocks has been adopted (for example, Patent Document 1). In this case, at the construction site of the coke oven, a heat regenerator is first constructed using silica bricks, a combustion chamber is constructed on top of that using large fused silica precast blocks, and a furnace top is constructed on top of that using silica bricks. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-222758 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have closely observed the operating conditions of a coke oven in which the combustion chamber is constructed from fused silica precast blocks, and the furnace top above the combustion chamber and the regenerator below the combustion chamber are each constructed from silica bricks, and as a result, have noticed the following problematic phenomenon: In a coke oven in which the combustion chamber is constructed from fused silica precast blocks, and the furnace top above the combustion chamber and the regenerator below the combustion chamber are each constructed from silica bricks, the thermal expansion behavior of the fused silica precast blocks and the silica bricks differ, and as a result, the fused silica precast blocks follow the expansion of the silica bricks and move, generating friction and applying a load to the silica bricks and the fused silica precast blocks, which may result in damage to the silica bricks or the fused silica blocks.

[0006] The problem to be solved by the present invention is to provide a lubricant for a coke oven that suppresses damage to the fused silica precast blocks and silica bricks in a coke oven in which the combustion chamber is constructed from fused silica precast blocks, and the furnace top above the combustion chamber and the regenerator below the combustion chamber are each constructed from silica bricks. [Means for solving the problem]

[0007] The present inventors conducted detailed observations of the operating conditions of a coke oven in which the combustion chamber was constructed from fused silica precast blocks, and the furnace top above the combustion chamber and the regenerator below the combustion chamber were each constructed from silica bricks, and found that the joints between the fused silica precast blocks and the silica bricks reached high temperatures of approximately 1000°C during operation of the coke oven. Therefore, the present inventors came up with the idea of ​​applying a lubricant primarily composed of spherical alumina particles to the joints between the fused silica precast blocks and the silica bricks in order to reduce friction between the fused silica precast blocks and the silica bricks in a high-temperature state of approximately 1000°C. The inventors then comprehensively examined the unique circumstances of the joint between a fused silica precast block and a silica brick in a coke oven, namely, the temperature conditions, load conditions, thickness conditions, etc. of the joint, as well as the materials of the fused silica precast block and the silica brick, and completed the present invention by specifying the particle size composition of the spherical alumina particles and the type and amount of binder to be used in combination with the spherical alumina particles in order to reduce friction between the fused silica precast block and the silica brick and ensure workability during construction and resistance to thermal deformation after construction.

[0008] That is, according to one aspect of the present invention, there is provided the following coke oven lubricant. 1. A coke oven lubricant applied to a joint between a fused silica precast block and a silica brick in a coke oven having a combustion chamber constructed of a fused silica precast block, a furnace top above the combustion chamber, and a regenerator below the combustion chamber constructed of a silica brick, the lubricant comprising: The material contains 91% by mass or more and 95% by mass or less of spherical alumina particles and 5% by mass or more and 9% by mass or less of an organic adhesive material, The particle size composition of the alumina particles is such that coarse particles with a particle size of 0.5 mm or more and less than 1 mm account for 70% by mass to 80% by mass, medium coarse particles with a particle size of 0.3 mm or more and less than 0.5 mm account for 10% by mass to 20% by mass, and fine particles with a particle size of less than 0.070 mm account for 10% by mass to 20% by mass. [Effects of the Invention]

[0009] According to the present invention, in a coke oven in which the combustion chamber is constructed of fused silica precast blocks, and the furnace top above the combustion chamber and the regenerator below the combustion chamber are each constructed of silica bricks, damage to the fused silica precast blocks and silica bricks can be suppressed. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a conceptual diagram of an evaluation sample used to evaluate lubricity. [Figure 2] A conceptual diagram showing the lubricity evaluation method. DETAILED DESCRIPTION OF THE INVENTION

[0011] The coke oven lubricant of the present invention (hereinafter simply referred to as "lubricant") is applied to the joint between the precast block structure and the silica bricks in a coke oven in which the combustion chamber is constructed from fused silica precast blocks, and the furnace top above the combustion chamber and the heat regenerator below the combustion chamber are each constructed from silica bricks.

[0012] Fused silica precast blocks are precast blocks obtained by blending fused silica as the main raw material. Specifically, the amount of fused silica blended in the raw material blend can be approximately 65 mass% or more. Fused silica is a white powder obtained by melting crushed raw silica stone in a high-temperature flame and forming it into a spherical shape using surface tension. Thus, the thermal expansion coefficient of fused silica precast blocks, which are primarily composed of fused silica, is 0.1% or less between 200 and 800°C. On the other hand, silica bricks are made from rock-like silica as aggregate. The thermal expansion rate of silica bricks, which are primarily composed of silica, is about 1.2% between 200 and 800°C.

[0013] Previously, a structure was known in coke ovens that allowed sliding between bricks made of different materials, preventing damage to silica and clay bricks caused by differences in thermal expansion due to differences in brick materials. However, this technology was applied between silica and clay bricks, and functioned at approximately 600°C, so it mainly utilized the solid lubricating properties of graphite, and used a lubricant that adjusted workability by adding organic paste to this graphite. In the present invention, in order to inexpensively construct a coke oven that makes the most of the properties of fused silica precast blocks, and to minimize the range of application of fused silica precast blocks, in a coke oven in which only the combustion chamber is constructed with fused silica precast blocks and the other areas, i.e., the sole flue, regenerator, bellows, and furnace top, are constructed with silica bricks and clay bricks, the interface between the fused silica precast blocks and the silica bricks is the top of the bellows, and the temperature at this location during operation reaches 1000° C. At such temperatures, conventional lubricants that are primarily made of graphite oxidize and lose their function as lubricants. To address these problems, the present invention applies a lubricant primarily composed of spherical alumina particles instead of the conventional lubricant primarily composed of graphite. The thickness of the lubricant is approximately 2 to 4 mm, as in the conventional lubricant. Furthermore, a vertical load of approximately 0.1 MPa typically acts on the joint between the fused silica precast block and the silica brick. Furthermore, as described above, during coke oven operation, the joint between the fused silica precast block and the silica brick reaches a high temperature of approximately 1000°C. In the present invention, the composition of the lubricant was specified by comprehensively considering the unique circumstances of the joint between the fused silica precast block and the silica brick in a coke oven, such as the temperature, load, and thickness conditions of the joint, as well as the materials of the fused silica precast block and the silica brick. A detailed description is provided below.

[0014] The lubricant of the present invention contains 91 to 95% by mass of spherical alumina particles and 5 to 9% by mass of an organic adhesive. Thus, the lubricant of the present invention typically consists of only spherical alumina particles and an organic adhesive, and an appropriate amount of water is added during application. The amount of water added can be approximately 7 to 12% by mass based on 100% by mass of the lubricant.

[0015] As described above, the object of the present invention is to suppress damage to fused silica precast blocks and silica bricks. To achieve this object, the lubricant of the present invention is primarily required to reduce friction between the fused silica blocks and silica bricks. Furthermore, to ensure that this friction-reducing function (hereinafter referred to as "lubricity") can be fully utilized during coke oven operation, the lubricant must not denature at temperatures of 1000°C and must not react with the fused silica precast blocks or silica bricks to produce low-melting-point substances or other substances (hereinafter referred to as "thermal stability"). Furthermore, the lubricant must be easy to apply with a trowel (hereinafter referred to as "workability"). Furthermore, the lubricant must be resistant to deformation due to heating after application, so that its thickness can be maintained (hereinafter referred to as "thermal deformation resistance").

[0016] In this invention, spherical particles are used to ensure lubricity, and alumina is used as the material for the spherical particles to ensure thermal stability. Furthermore, coarse particles with a particle size of 0.5 mm to less than 1 mm are primarily used, with an appropriate amount of medium-coarse particles with a particle size of 0.3 mm to less than 0.5 mm and fine particles with a particle size of less than 0.070 mm. Alumina does not denature at temperatures of 1000°C and is unlikely to react with fused silica precast blocks or silica bricks to produce other substances, such as low-melting-point substances. Therefore, the lubricant's lubricating function is not impaired by chemical changes or deformation. Furthermore, the use of coarse particles primarily prevents sintering between particles. Furthermore, the combination of appropriate amounts of medium-coarse and fine particles ensures the lubricant as a whole exhibits a bearing effect and ensures stable lubrication.

[0017] The fine particles also contribute to improving workability and heat distortion resistance. That is, when the appropriate amount of fine particles is included, the lubricant becomes smooth and easy to apply with a trowel. Furthermore, the fine particles fill the gaps between the coarse and medium-coarse particles, making it easier to maintain the shape after application.

[0018] From the above viewpoints, the lubricant of the present invention contains 91 to 95% by mass of spherical alumina particles, and the particle size distribution of the spherical alumina particles is as follows: 70 to 80% by mass of coarse particles having a particle size of 0.5 mm to 1 mm, 10 to 20% by mass of medium-coarse particles having a particle size of 0.3 mm to 0.5 mm, and 10 to 20% by mass of fine particles having a particle size of less than 0.070 mm. In other words, the lubricant of the present invention contains 91 to 95% by mass of spherical alumina particles, and the spherical alumina particles contain, relative to 100% by mass of the spherical alumina particles, 70 to 80% by mass of coarse particles having a particle size of 0.5 mm to 1 mm, 10 to 20% by mass of medium-coarse particles having a particle size of 0.3 mm to 0.5 mm, and 10 to 20% by mass of fine particles having a particle size of less than 0.070 mm.

[0019] Here, in the present invention, "spherical alumina particles" refers to solid alumina particles with a sphericity of 1.0 to 1.5, and examples thereof include commercially available spherical alumina and alumina balls. Furthermore, "sphericity" refers to the arithmetic mean value (n=10) of the ratio of the maximum diameter to the minimum diameter of any 10 alumina particles measured by a binarization measurement method using image analysis with a scanning electron microscope (SEM). In the following description, "spherical alumina particles" will simply be referred to as "alumina particles."

[0020] In the present invention, the proportion of medium-sized alumina particles having a particle size of 0.070 mm or more and less than 0.3 mm is not particularly specified as the particle size composition of the alumina particles, but the lubricant of the present invention may or may not contain medium-sized alumina particles. Furthermore, in the present invention, the purity of the alumina particles is preferably 99.9% or more, particularly from the viewpoint of ensuring thermal stability.

[0021] In the present invention, particle size refers to the size of the sieve openings when particles are sieved to separate them. For example, alumina particles with a particle size of less than 0.5 mm are alumina particles that pass through a sieve with 0.5 mm openings, and alumina particles with a particle size of 0.5 mm or more are alumina particles that do not pass through a sieve with 0.5 mm openings.

[0022] The lubricant of the present invention contains an organic adhesive material as a binder in an amount of 5% by mass or more and 9% by mass or less. If the organic adhesive material content is less than 5% by mass, sufficient workability during application cannot be ensured. On the other hand, if the organic adhesive material content exceeds 9% by mass, heat distortion resistance after application decreases. It is preferable that the organic adhesive material does not contain CaO, MgO, or alkali components that react with fused silica precast blocks or silica bricks to produce low-melting-point substances, or if it does contain such components, it contains only a small amount. Typically, starch, such as dextrin, corn starch, potato starch, or tapioca, can be used.

[0023] As described above, the lubricant of the present invention typically consists of only alumina particles and an organic adhesive, but this does not exclude the inclusion of substances other than alumina particles and the organic adhesive. For example, it may contain oxide particles other than alumina particles, such as silica particles, or binders other than the organic adhesive. When oxide particles other than alumina particles are used, it is preferable to use solid, spherical oxide particles with a sphericity of 1.0 to 1.5. [Example]

[0024] Table 1 shows the configurations of the lubricants according to the examples of the present invention and the comparative examples, and the evaluation results thereof.

[0025] [Table 1]

[0026] The evaluation items were lubricity, workability, and heat distortion resistance, and each was evaluated according to the following criteria.

[0027] <Lubricity> A lubricant paste was obtained by adding 12% by mass of water to 100% by mass of each lubricant. Then, as shown in Figure 1, the lubricant paste was applied to the top and bottom surfaces of a fused silica precast block measuring 100 x 100 x 50 mm thick, with a thickness of 3 mm, and allowed to harden sufficiently. After the lubricant paste had hardened, the top and bottom surfaces of the fused silica precast block were sandwiched between silica bricks measuring 100 x 100 x 50 mm thick, and this was used as the evaluation sample. The evaluation sample is placed in an electric furnace and heated to 1000°C at a rate of 5°C / min, and then maintained at 1000°C for 72 hours. After 72 hours, the evaluation sample is removed from the 1000°C electric furnace and placed in the evaluation device, sandwiched between refractory bricks from above and below, as conceptually shown in Figure 2. After placing the evaluation sample, a hydraulic cylinder (not shown) attached below the lower refractory brick is used to push up the evaluation sample, and a load is applied until the top surface of the evaluation sample hits the upper refractory brick and a vertical load of 0.1 MPa is applied to fix it in place. After fixing, a horizontal load is applied to the fused silica precast block portion of the evaluation sample, and the coefficient of friction is measured. The lubricity was evaluated as good when the friction coefficient was less than 0.4, and poor when it was 0.4 or more.

[0028] <Workability> The workability was evaluated by the free flow value of the lubricant paste obtained as described above. The free flow value refers to the diameter of the lubricant paste spread when the lubricant paste is poured into a flow cone as specified in JIS R 2521, filled with the lubricant paste, and the flow cone is removed upward and left to stand for 60 seconds. The workability was evaluated as good when the free flow value was 110 to 130 mm, and poor when it was less than 110 mm or more than 130 mm.

[0029] <Heat deformation resistance> To evaluate the heat deformation resistance, the lubricant paste obtained as described above was formed into a pellet shape of φ30mm x 10mm, and if there was no deformation in the diameter (φ30) up to 300°C, it was rated as good, and if there was deformation, it was rated as poor.

[0030] All of the lubricants in Examples 1 to 7 were within the scope of the present invention, and were excellent in the evaluation of lubricity, workability, and heat distortion resistance.

[0031] Comparative Example 1 is an example in which the particle size structure of the alumina particles is composed only of coarse particles, Comparative Example 2 is an example in which the particle size structure of the alumina particles is composed only of medium-coarse particles, and Comparative Example 3 is an example in which the particle size structure of the alumina particles is composed only of fine particles, and all of these examples were evaluated as poor in lubricity and poor in workability.

[0032] Comparative Example 4 does not contain fine alumina particles, but the ratio of coarse particles to medium-coarse particles in the particle size composition of the alumina particles is within the range of the present invention. The lubricity evaluation was just good, but the workability evaluation was poor. Comparative Example 5 is an example in which fine alumina particles were not included and the ratio of coarse particles to medium-coarse particles in the particle size composition of the alumina particles was outside the range of the present invention. The lubricity evaluation was poor and the workability evaluation was also poor. Comparative Example 6 does not contain medium-to-coarse alumina particles, but the ratio of coarse to fine particles in the particle size composition of the alumina particles is within the range of the present invention. The evaluation of workability was good, but the evaluation of lubricity was poor. Comparative Example 7 is an example in which no medium-to-coarse alumina particles were contained and the ratio of coarse to fine particles in the particle size composition of the alumina particles was outside the range of the present invention. The lubricity evaluation was poor and the workability evaluation was also poor.

[0033] Comparative Example 8 is an example in which the content of the organic adhesive material was too high, and the evaluation of the heat distortion resistance was poor, and accordingly the evaluation of the lubricity was also poor. Comparative Example 9 is an example in which the content of the organic adhesive material was too low, and the evaluation of workability was poor, and accordingly the evaluation of lubricity was also poor.

Claims

1. 1. A coke oven lubricant applied to a joint between a fused silica precast block and a silica brick in a coke oven having a combustion chamber constructed of a fused silica precast block, a furnace top above the combustion chamber, and a regenerator below the combustion chamber constructed of a silica brick, the lubricant comprising: The composition contains 91% by mass or more and 95% by mass or less of spherical alumina particles and 5% by mass or more and 9% by mass or less of an organic adhesive material, The particle size composition of the alumina particles is such that coarse particles with a particle size of 0.5 mm or more and less than 1 mm account for 70% by mass to 80% by mass, medium coarse particles with a particle size of 0.3 mm or more and less than 0.5 mm account for 10% by mass to 20% by mass, and fine particles with a particle size of less than 0.070 mm account for 10% by mass to 20% by mass.

2. 2. The coke oven lubricant of claim 1, wherein the organic glue is starch.

3. 3. The coke oven lubricant according to claim 1, wherein the purity of the alumina particles is 99.9% or more.

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