JP3057859B2 - Production method and furnace wall structure of silica brick for coke oven. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to a method for producing silica brick used for a furnace body of a coke oven and a furnace wall structure of a coke oven using the same. More specifically, the present invention relates to a method for manufacturing a silica brick for a coke oven and a furnace wall structure in which the performance of the silica brick is improved by performing a secondary treatment on the existing brick, and the furnace wall structure of the coke oven is strengthened.

[0002]

2. Description of the Related Art Silica brick is an acidic refractory brick made of a raw material containing anhydrous silicate as a main component, and has a high mechanical strength at a high temperature. It has the property of withstanding large loads. Further, the coefficient of thermal expansion at 760 ° C. or higher is extremely small, and shows good volume stability in this temperature range. Taking advantage of these characteristics, silica brick is used for ceilings of general kilns. However, since it does not shrink particularly after long use, it is also widely used for furnace bodies of coke ovens.

Recently, coke oven along with the size of the steel manufacturing facilities are large, but the aim of improving productivity, carbonization chamber furnace walls order to further shorten the carbonization time in terms of energy saving and NO _x reduction Therefore, there is a demand for a dense and high thermal conductive silica brick. On the other hand, in the operating coke oven, carbon from the carbonization gas adheres to the inner wall surface of the oven and forms a strong carbon adhesion layer. There is a demand for dense bricks to which carbon does not easily adhere. In order to cope with such a situation, various proposals have conventionally been made on a method for producing a dense brick, a treatment method for densifying the brick, or a method for maintaining the cleanness of the brick surface.

In the production of silica bricks, CaO, TiO ₂ , Mg
A method of adding an oxide material such as O, or SiC, Si
There is a method of blending a non-oxide such as N to promote oxidation at the firing stage. However, in these methods, unevenness in firing tends to occur, and even if densification can be achieved, sufficient performance cannot be maintained because the fire resistance and the softening point under load are reduced. In addition, the adjustment of the pore distribution is insufficient with this method.

[0005] As a treatment method for densifying the silica brick, there are a coating method for sealing pores in the surface area of the brick and a method of impregnating pores in the brick. As the former method, for example, a method of treating with a coating material containing fly ash as a main component described in JP-B-57-27873, or a glaze made of crystalline glass described in JP-A-59-174585. There is a method of providing a layer. Each of these surface treatment materials is a low melt containing alkali, ZnO 2, CaO 2 and the like, and thus deteriorates the fire resistance of the base silica brick. In addition, since the surface layer contains a liquid phase, it promotes the adhesion of carbon, and wears due to friction with the coke cake when it is discharged from the kiln, so that only a transient effect can be expected.

[0006] As the latter impregnation method, immersion of a solution can be considered. For example, magnesia dolomite bricks may be impregnated with wax to prevent moisture absorption.
It is also a well-known method to impregnate coal tar from the viewpoint of improving corrosion resistance. There is also known a method of impregnating with colloidal silica (silica sol) and performing heat treatment so that SiO ₂ remains in pores. However, its content is 20
At about weight%, the filling amount is smaller than the permeation amount of the solution,
The fact is that sufficient effects cannot be obtained.

As another possible method for preventing carbon deposition,
There is a method of removing carbon. For example, JP-A-61-231088
Japanese Patent Application Publication No. JP-A-2005-115122 discloses a method of burning and separating carbon by using a special nozzle. There is also a method of shaving off with a sandblaster. However, although these are effective for the adhering carbon itself, they secondarily cause damage to the base material brick and impair the robustness of the furnace in the long term.

In general, filling the pores with an oxide and densifying the pores is a process that impairs spalling resistance and is incompatible with improving strength. However, if the microstructure can be changed to a method of making the pore distribution fine, a state in which the densification and the spalling resistance are satisfied at the same time and the generation of attached carbon is difficult can be obtained. In addition, if the impregnating substance can be given a releasing action, it can be used semi-permanently as furnace wall brick, and the economic efficiency is remarkably improved. However, such a method has not been established at present.

[0009]

The problems of the furnace wall structure caused by the conventional silica brick are summarized as follows. Densification by the addition of additives causes deterioration of other properties such as fire resistance, and insufficient adjustment of pore distribution. The method of sealing the brick surface by coating has a temporary effect and has a large secondary adverse effect. In the method in which pores are sealed by impregnation, the amount of residual components is small, and the required pore reduction cannot be achieved.

An object of the present invention is to provide a high-strength and robust carbon dioxide coke oven which has good heat transfer characteristics to dry distillation, suppresses carbon deposition during operation, and has a high density. An object of the present invention is to provide a method for producing a silica brick for a coke oven, and an oven wall structure constituted therefrom.

[0011]

DISCLOSURE OF THE INVENTION The present inventors have achieved the above object by impregnating the pores of an existing silica brick with ceramic fine particles and densifying the same, thereby achieving robustness with less operation trouble. It has been found that a simple furnace wall structure can be obtained.

Here, the gist of the present invention is that the average particle size is 0.05 to
An impregnating liquid obtained by dispersing 7 to 60 parts by weight of one or two kinds of 10 μm chromium oxide powder and calcium carbonate powder in 93 to 40 parts by weight of at least one organic or silicon-based liquid binder is used. A method for producing a silica brick for a coke oven, characterized in that the silica brick of 16 to 25% is impregnated under reduced pressure and then dried, and at least a part of the wall surface of the carbonization chamber is produced by the above method. A furnace wall structure of a coke oven characterized by being composed of silica brick.

[0013]

According to the present invention, one or two kinds of fine particles of chromium oxide (Cr ₂ O ₃ ) and calcium carbonate (CaCO ₃ ) having a particle size adjusted to a specific range are used instead of the conventional liquid impregnation with only silica sol. By impregnating with a liquid in which is dispersed, pores can be efficiently sealed without impairing fire resistance. In addition, since the liquid and calcium carbonate powder used for the impregnation are thermally decomposed by increasing the temperature at the start of the operation of the coke oven to form fine pores, the pore size of the pore distribution can be simultaneously increased, and the apparent porosity can be achieved. As described above, the thermal shock resistance, and thus the spalling resistance, is maintained favorably.

The method for producing a silica brick of the present invention comprises:
This will be described in detail below. The silica brick used as the base material in the present invention is not particularly limited in composition, but has an apparent porosity.
Use 16-25%. When the apparent porosity is less than 16%, the spalling resistance is reduced even if the impregnation is performed by the method of the present invention. On the other hand, if the apparent porosity exceeds 25%, the impregnation efficiency is reduced, and the desired effect cannot be sufficiently obtained.

The silica brick is impregnated with an impregnating liquid in which fine particles of one or two selected from chromium oxide powder and calcium carbonate powder are dispersed in at least one organic or silicon liquid binder. .

As the fine particles to be dispersed in the impregnation liquid, chromium oxide powder or calcium carbonate powder alone or a mixed powder thereof is used. Chromium ions form a high-viscosity melt even when they react with SiO _{2 in} silica brick,
The adverse effect on load softening is small. Also, calcium ions, shows the effect of the reaction of the SiO ₂ has a property of tridymite the SiO _2, increased resistance to rapid heating-rapid cooling. The particle size of the fine particles is in the range of 0.05 to 10 μm in average particle size. When the average particle size is larger than 10 μm, it is difficult to smoothly penetrate into the pores of the silica brick, and only the surface layer is completely penetrated, and cannot penetrate pores having a diameter of 30 μm or less. When the average particle size is smaller than 0.05 μm, the particles are agglomerated when dispersed, and cannot be efficiently dispersed in the binder liquid. Further, without the presence of these fine particles, conventional silica sol (the average particle size of
When only 100 nm) is impregnated into silica brick, it is only impregnation of the liquid, and no substantial packing by particles occurs.

As a dispersion medium for dispersing the fine particles,
An organic or silicon-based liquid binder is used. Examples of the organic liquid binder include a liquid obtained by diluting a resin such as an acrylic resin or a phenol resin with an appropriate organic solvent (eg, isopropanol) as required, or a viscous liquid organic compound such as a polyhydric alcohol (eg, glycerin). Can be used. The silicon-based liquid binder can supplement Si and form a siloxane bond to contribute to densification. Examples of useful silicon-based liquid binders include silicone oil (diluted with an organic solvent if necessary), silica sol,
And aqueous solutions of sodium silicate (eg, water glass).
Water-based liquids such as silica sol and sodium silicate aqueous solution have a high vapor pressure, and crystal water and attached water are formed during the water evaporation process, so care must be taken to completely remove water in the next drying step. It costs. The liquid binder preferably has a viscosity at room temperature of 50 cp or less. If the viscosity is too high, dilute it with an appropriate diluent (organic solvent, water) to reduce the viscosity.

The mixing ratio between the fine particles and the liquid binder (after dilution, if diluted) is defined as 100 parts by weight of the total amount of both, and 7 to 60 parts by weight of the fine particles and 93 to 50 parts by weight of the liquid binder. It should be within the range of 40 parts by weight. 7 particles
If the amount is less than part by weight, the effect of impregnation of the fine particles is unclear, and the required performance improvement cannot be achieved. When the amount of the fine particles exceeds 60 parts by weight, the viscosity of the prepared impregnating liquid itself increases, and it becomes difficult to perform a sufficient amount of impregnation.

If desired, small amounts of other components may be present in the impregnating liquid. Examples of other components that can be added include organic dispersants.

The impregnating liquid thus prepared is impregnated into silica brick under vacuum. In this impregnation, for example, the impregnation liquid and the silica brick are charged into a vacuum chamber and deaerated by a vacuum pump, or the vacuum chamber in which the silica brick is previously charged is degassed, and then the degree of vacuum is reduced. It can be carried out by introducing the impregnating liquid while maintaining. The degree of vacuum during impregnation is
It is preferable that the pressure be about 3 Torr or less. This impregnation
The impregnation liquid is permeated into at least 10 mm or more from the surface layer of the silica brick. Normal temperature is sufficient for the impregnation temperature, but heating may be performed if desired. The impregnation time is usually one hour or more, and is adjusted according to the temperature and the size of the silica brick to be treated.

After the impregnation, the silica brick is taken out of the vacuum chamber and dried to remove volatile components such as a solvent in the impregnation liquid. Drying is desirably heat drying, but drying at room temperature is also possible depending on the type of solvent.

The silica brick produced by impregnation according to the method of the present invention is densified and has significantly improved thermal and mechanical properties as compared with untreated silica brick. By constructing the furnace wall structure, the adhesion of carbon is small, the thermal conductivity is high,
A robust coke oven wall structure for a coke oven can be formed. Furthermore, since the impregnated binder and calcium carbonate powder are thermally decomposed to form fine pores by raising the temperature at the start of the coke oven operation, the thermal shock resistance is kept good, and the spalling resistance is lowered. Absent. Therefore, at least a part of the furnace wall structure of the coke oven carbonization chamber (for example,
By forming the siliceous brick selected by the method of the present invention from the middle part of the furnace wall of the coking chamber, preferably, the whole is made of silica brick. A coke oven wall structure that does not require removal processing is constructed.

[0023]

EXAMPLES The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples.

Example 1 Calcium carbonate powder having an average particle size of 0.1 μm and chromium oxide powder having an average particle size of 1.4 μm
Mix uniformly at a weight ratio of 1 and mix 25 parts by weight of this mixed powder with 75 parts by weight of the liquid binder shown in Table 1 and sufficiently stir with ultrasonic vibration to uniformly disperse the powder and prepare the impregnating liquid. did. In Table 1, the acrylic resins were each diluted with isopropanol (IPA) to the concentration in parentheses before use. The values of specific gravity and viscosity are values after dilution.

[0025]

[Table 1]

From a silica brick having an apparent porosity of 21%, the diameter is
Two types of test pieces were cut out: a 50 mm x 50 mm length cylindrical body and a 25 mm x 25 mm x 140 mm square rod, and these two test pieces were placed in the impregnating liquid charged in a vacuum chamber. Throw in, 10 ^-3
The impregnation treatment was performed at room temperature for 3 hours at a vacuum of Torr, so that the impregnation liquid permeated all pores of the brick. Thereafter, the silica brick was taken out of the impregnating liquid and dried with hot air to obtain an impregnated material.

The impregnated material thus obtained was further dried in a dryer at 100 ° C. for 10 hours for testing, and then the pore size distribution by the mercury intrusion method and the hot bending strength at 1000 ° C. were measured. did. Table 2 summarizes the measurement results.

[0028]

[Table 2]

As can be seen from Table 2, when the silica brick is impregnated with the impregnating liquid in which the fine particles of chromium oxide and calcium carbonate are dispersed according to the present invention, the untreated irrespective of whether the binder resin is organic or silicon-based. The apparent porosity, the amount of micropores, and the average pore diameter were all significantly lower than those of silica brick, and the structure was densified and pored.
At the same time, the bending strength was significantly improved and strengthened.

Example 2 A silica brick treated material according to the method B of the present invention shown in Example 1 (impregnated material using silicone oil as a binder, but the mixing ratio of chromium oxide powder and calcium carbonate powder is weight ratio (3: 2) and a commercially available dense silica brick (apparent porosity 16.0%) were subjected to a heat cycle test. Figure 1 shows the pore distribution of both test materials.
Shown in In the test, a cylindrical brick test piece was reciprocated up and down in two vertically connected cylindrical electric furnaces maintained at temperatures of 900 ° C. and 400 ° C., respectively, and subjected to thermal shock.
Table 3 shows the results of visual observation of the surface of the test piece after 10 cycles of thermal shock for cracks. For comparison, the results of a test material in which the surface of a silica brick is coated with a glaze layer made of a low-expansion crystalline glass according to the method disclosed in JP-A-59-174585 are also shown.

[0031]

[Table 3]

In the untreated conventional example, cracks were generated by thermal shock, whereas those impregnated by the method of the present invention were resistant to thermal shock and did not crack. Therefore, it can be seen that the method of the present invention produces silica brick having excellent thermal shock resistance. It was found that the coating of the surface coated with the low-expansion glaze layer of the comparative example was peeled off by the thermal shock and could not serve as the coating.

[Example 3] In a coke oven A (a furnace volume of 48.5 m ³ , 50 units) operating at a load factor of 115%, the furnace was about 1 m ² in size to repair the end flue bottom on the coke side. The bricks on the wall are cut open, and after repair, a separate brick is replaced to repair the furnace wall. As the replacement brick at this time, a silica brick impregnated by the method of the present invention (the treatment material A of Example 1 using an acrylic resin as a binder) was applied, and when the empty kiln was inspected, the wall condition was broken and carbon was removed. The adhesion was observed and evaluated. The results are shown in Table 4 together with the case where the conventional untreated silica brick was replaced with an apparent porosity of 18%.

[0034]

[Table 4]

As is clear from the above results, it was found that the impregnated steel according to the present invention had less carbon adhesion and less cracking during operation than the conventional silica brick.

[0036]

By the impregnation treatment according to the method of the present invention, it is possible to produce a reinforced silica brick having an apparent porosity lower than that of an untreated silica brick, significantly densified, and having a high high-temperature strength. it can. Moreover, the resulting silica brick has a reduced pore diameter due to the impregnation process,
Despite the impregnation treatment, the thermal shock resistance is higher than that of the untreated product, and the spalling resistance is improved. Therefore, according to the present invention, a silica brick for forming a furnace wall of a coke oven carbonization chamber, which is dense, has low carbon adhesion, has good thermal conductivity, has high strength and long life, and has excellent spalling resistance. It can be easily manufactured. As a result, the operating efficiency of the coke oven is greatly improved, and the coke oven can be operated stably for a long period of time.

[Brief description of the drawings]

FIG. 1 shows a silica brick obtained by the method of the present invention (product of the present invention) and an untreated commercial dense silica brick used in the examples.
3 is a graph showing the pore distribution of (commercially available product).

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-59-174585 (JP, A) JP-A-2-160896 (JP, A) JP-A-53-131086 (JP, A) JP-A-58-178 99179 (JP, A) JP-A-59-73473 (JP, A) JP-A-62-197371 (JP, A) JP-A-54-19243 (JP, U) JP-B-57-27873 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) C10B 29/02 C04B 41/45 C04B 41/81 F27D 1/00

Claims (2)

(57) [Claims] 1. One or two or more 7 to 60 parts by weight of chromium oxide powder and calcium carbonate powder having an average particle size of 0.05 to 10 μm are added to 93 to 40 parts by weight of at least one organic or silicon-based liquid binder. Dispersed impregnating liquid has an apparent porosity
A method for producing silica brick for a coke oven, comprising impregnating 16 to 25% of silica brick under reduced pressure and drying. 2. A furnace wall structure for a coke oven, wherein at least a part of the wall surface of the carbonization chamber is made of silica brick produced by the method according to claim 1.