JP2016052960A - Silica castable refractory and silica precast block refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silica castable refractory excellent in thermal shock resistance during heating, having suppressed shrinkage under load at high temperature, good in creep resistance at high temperature, hardening in appropriate time and capable of being flow molding easily even when being a large molded body.SOLUTION: There is provided a silica castable refractory by adding Portland cement of 0.7 to 2 mass%, a water-reducing agent of 0.03 to 0.3 mass%, sodium silicate of 0.04 to 0.30 mass% in terms of NaO, by outer multiplication, based on 100 mass% of a silica refractory raw blended article consisting of molten quartz, crystalline silica consisting of cristobalite and quartz and silica superfine powder. There is provided a silica castable refractory which has blended ratio of the silica refractory raw material blended article of the molten quartz of 96 to 70 mass%, the crystalline silica consisting of cristobalite and quartz of 0 to 20 mass% and the silica superfine powder of 3.8 to 10 mass%, and may contain burnt silica of 10 mass% or less as a part of the silica refractory raw material blended article.SELECTED DRAWING: None

Description

  The present invention relates to a siliceous castable refractory material that is excellent in thermal shock resistance during heating, is suppressed from shrinkage under load at high temperatures, and hardly undergoes creep deformation, and a siliceous precast block refractory material using the same.

  Generally, in a coke oven, silica brick is lined for a long period of 30 years or more, and repair of damaged lining parts during long-term use is performed by replacing bricks or spraying refractory materials. . Among these, the repair brick is required to have thermal shock resistance because it is built on the inner wall of the coke oven kept at around 500 ° C.

  Silica brick for lining mainly consists of tridymite and cristobalite as crystal phases, but each crystal has an abnormal volume change due to transition from low temperature type to high temperature type in low temperature region, so thermal shock resistance is inferior. It is not suitable as a hot repair brick. Tridymite undergoes phase transition at 117 ° C and 163 ° C, resulting in a linear change of 0.15% and 0.2%, respectively, and cristobalite undergoes a phase change at 230 ° C to 270 ° C, resulting in a linear change of approximately 0.4%. Occurs.

  Therefore, as a silica brick for hot repair, a brick using a fused silica and a fused silica having a low thermal expansion is usually used. The hot expansion coefficients of cristobalite and tridymite at 1000 ° C. are 1.5% and 1.0%, respectively, whereas that of fused quartz is very small, 0.1%. Can be reduced, and thermal shock resistance is generated. For example, Patent Documents 1 to 5 describe silica impact bricks having thermal shock resistance, which are composed of calcined silica mainly composed of cristobalite and / or tridymite and fused silica.

  Fused quartz has the property of crystallizing at a temperature dependent rate regardless of its particle size. The brick is usually fired at 1200 ° C. to 1400 ° C. in the manufacturing process. When the fused quartz blended before firing is crystallized in the firing process, the thermal shock resistance decreases. Since fused quartz is crystallized from the particle surface during the firing process, if it is used in the fine powder part, it will crystallize to the inside during the firing process, and the amorphous part disappears. Thus, complete disappearance of the amorphous part in the firing process is avoided.

On the other hand, a castable refractory is a powder refractory mixed with a refractory aggregate and a hardener, has hydration properties or chemical bonds, and is added in various forms such as vibration and tamping after adding water and kneading. It is constructed. If the temperature rises rapidly after curing, the water vapor pressure in the construction body increases and there is a risk of explosion, so it is necessary to increase the temperature stepwise until it reaches several hundred degrees C over several days and dry.
As the hardener for castable refractories, alumina cement is usually used, but when alumina cement is used for siliceous castable refractories, the main component of aggregate is CaO · Al ₂ O ₃ which is the main component of alumina cement. Reacts with SiO ₂ to produce an aluminum / calcium silicate (CaO—Al ₂ O ₃ —SiO ₂ ) -based low melting point, and loses aggregate particles in a high temperature range, resulting in significantly increased shrinkage under load. Therefore, it is limited to use in a low temperature range.

As a curing agent for siliceous castable refractories, Portland cement is widely used, and there are those that are cured by the gelation action of colloidal silica.
Portland cement is mainly composed of calcium silicate, and when used in siliceous castable refractories, the amount of CaO-Al ₂ O ₃ —SiO ₂ low melting point product is small and high melting point CaO—SiO ₂ type compound is In order to maintain the function as a binder, it can be used at a higher temperature than when alumina cement is used as a hardener. For this reason, Portland cement has become mainstream as a hardener for siliceous castable refractories.

  For example, Patent Documents 6 and 7 describe a siliceous castable refractory using Portland cement as a curing agent. Patent Document 6 relates to a siliceous castable refractory material containing 2-10% by mass of Portland cement and 1-8% by mass of silica ultrafine powder using fused quartz as a main raw material. Patent Document 7 discloses a post-use silica brick that contains 70% by mass or more of tridymite as a main mineral phase or a non-standard product of a fired silica brick, 2-5% by weight of Portland cement, and 8-22 of fumed silica. The present invention relates to a siliceous castable prepared by blending mass%.

Calcium silicate which is the main component of Portland cement (its main component is alite (3CaO · SiO ₂ )) is hydrated and contains a large amount of 3CaO · 2SiO ₂ · 3H ₂ O and the like as shown in the following chemical reaction formula. Although Ca (OH) ₂ is produced, the rate of hydration is slower than that of CaO.Al ₂ O ₃ which is the main material constituting alumina cement. Moreover, the dehydration temperature of Ca (OH) ₂ is high at 500 ° C to 600 ° C. For this reason, siliceous castable refractories using Portland cement as a curing agent need to take sufficient measures against explosion in addition to means such as adding a curing accelerator. Furthermore, the dehydration at 500 ° C. to 600 ° C. is accompanied by a large volume change and exhibits shrinkage.

For example, Patent Document 8 discloses a siliceous castable refractory material that is cured using the gelling action of colloidal silica. The siliceous castable refractory described in Patent Document 8 is 3.0 by converting colloidal silica into solid SiO ₂ as an outer shell with respect to 100% by mass of a siliceous refractory raw material composition composed of fused quartz and calcined silica. 9.3 mass%, sodium silicate in terms of solid Na ₂ O added 0.04 to 0.30 mass%, the blending ratio of fused quartz and calcined silica of the siliceous refractory raw material composition, When the calcined silica is composed mainly of tridymite, it is 40 to 100% by mass of fused quartz and 0 to 60% by mass of calcined silica. When it is composed mainly of tridymite and cristobalite, it is 60 to 100% by mass of fused silica and 0% of calcined silica. -40 mass%. The siliceous refractory raw material composition may contain 8% by mass or less of silica flour.

  Colloidal silica gels at room temperature by changing pH and adding electrolyte. As the electrolyte gelling agent, ammonium chloride, sodium perfluoride, sodium sulfate, and the like are known, but in Patent Document 8, readily soluble sodium silicate is used. When ammonium chloride is used as a gelling agent, it shrinks under load from around 900 ° C., but when sodium silicate is used, this shrinkage under load is suppressed.

  Fused quartz crystallizes at a temperature-dependent rate and changes to low-temperature high-temperature cristobalite or high-temperature tridymite, but alkali metals or alkaline-earth metals have an action to promote crystallization of fused quartz. Since the siliceous castable refractory described in Patent Document 8 uses sodium silicate as a gelling agent for colloidal silica, the soda component promotes the crystallization of fused quartz, resulting in a low-temperature high-temperature cristobalite. It is presumed that the shrinkage under load was suppressed as a result of the change in the speed of the change proceeding quickly. Table 1 shows the crystal phase of silica and the density of fused silica.

The siliceous castable described in Patent Document 8 contains a soda component as an impurity. The soda component is contained in a small amount in calcined silica or colloidal silica, but most of it is derived from sodium silicate used as a gelling agent. Alkali metal reacts with SiO ₂ to produce a low melting point, so if siliceous castable contains a soda component, it is technically common knowledge that shrinkage under load at high temperature increases and creep resistance also decreases. It is done. However, according to Patent Document 8, the total amount of soda component added by adding the soda component contained in colloidal silica and the soda component contained in sodium silicate is converted to solid Na ₂ O, 0.06 to 0.00. When the content is 32% by mass, shrinkage under load is relaxed, and creep resistance is substantially equivalent to that of ordinary silica brick. Moreover, since 40-100 mass% of low expansible fused quartz is used, the thermal shock resistance is also favorable.

  Castable refractories are usually cast in a mold after being mixed and mixed in a mixer at a place where a mold is installed in advance, such as an ironworks. Castable refractories that use colloidal silica as a curing agent are partly or entirely used as a kneading fluid and cannot be procured easily at construction sites like water. Need to be done.

Castable refractories using colloidal silica as a curing agent are liable to increase in viscosity and decrease in fluidity due to water evaporation of colloidal silica during casting in a high-temperature dry atmosphere. In addition, from the viewpoint of ease of construction, alumina cement or Portland cement may be used from the viewpoint of ease of construction. There are many problems compared to castable refractories that are hardeners.
Most of the siliceous castables that use colloidal silica as a curing agent described in Patent Document 8 are used as precast block materials in precast block manufacturing plants that are fully equipped with vibration tables, curing equipment, drying equipment, etc. Is covered with vinyl to prevent moisture evaporation.

Japanese Patent Publication No. 1-338073 JP-B-1-38074 JP 05-132355 A JP 2003-55035 A JP 2007-302540 A JP 56-78476 A JP 2006-290657 A JP 2013-189322 A

  There are various types of coke ovens, and the combustion method and heat storage method differ depending on the type, but the principle of carbonization of the coal is the same. The dried coal is put into the carbonization chamber from the coal opening at the ceiling part of the coke oven, and is subjected to dry distillation over less than one day to obtain coke. Coke that has been carbonized in the carbonization chamber is pushed out from the push side of the carbonization chamber by an extruder and discharged at the coke side. The temperature of the carbonization chamber is usually about 1000 ° C., and is maintained at 500 ° C. or higher even when the coke after dry distillation is discharged. The heat source is combustion heat of blast furnace gas and / or coke oven gas from a burner installed at the lower part of the combustion chamber, and the temperature of the combustion chamber is 1100 ° C to 1350 ° C. Each combustion chamber is subdivided into a number of flues (heating flame channels), and each flue is surrounded by a highly airtight silica brick of about 10 cm thickness. Combustion heat is conducted through the walls of the silica brick and reaches the side of the carbonization chamber, contributing to the dry distillation of coal.

  The extrusion surface of the extruder moves from the push side to the coke side in the carbonization chamber having a width of about 45 cm along the carbonization chamber side wall, but the coke after dry distillation is concentrated near the coke side outlet. Therefore, dense coke may damage the silica brick on the side wall of the coking chamber near the coke side outlet. The vicinity of the corkside exit is also a part that is rapidly cooled by contact with the outside air and is susceptible to thermal damage. Therefore, repairs are frequently performed frequently, and if the damage is significant, new silica brick is hot-replaced. Can be transshipped to siliceous brick or castable block refractories.

  If both side walls of the carbonization chamber are vertical and parallel, the extrusion surface of the extruder can move smoothly and coke can be discharged. Coke can no longer be discharged if the silica brick for squeezing out and the extrusion surface of the extruder cannot move. If such a problem location occurs near the center of the carbonization chamber, it does not stop at one flue, and in some cases, it is necessary to completely repair the corresponding carbonization chamber and combustion chamber.

  Various coke oven wall brick structures have been proposed and implemented in order to realize a long-life coke oven wall that is unlikely to cause problems such as the inclination of the carbonization chamber side wall and the extrusion of silica brick. Along with this, silica bricks for building coke ovens, hot-replacement siliceous bricks, and hot-replacement siliceous precast block refractories have a variety of shapes and sizes. Usually with dowels, the shape varies from a rectangular parallelepiped to an irregular shape such as an L shape, a U shape, and a T shape, and the weight is about 5 to 30 kg / piece.

  The coke oven wall is built by combining the various shapes of siliceous refractories as described above, but since the hot transshipment work is carried out in a heat wave exceeding 100 ° C, it is not only experience and technology, Requires labor and time. Recently, a hot transshipment method using a large-sized integrated siliceous precast block refractory having a unit structure (see FIG. 3) instead of combining various shapes of siliceous refractories has been proposed.

  The large sized precast block refractory is assumed to have a weight exceeding 500 kg, and is installed by being suspended and suspended by a crane in a portion requiring refurbishment. If several large precast block refractories are stacked and installed in one flue, the repair work for one flue is completed. The coke oven wall is formed by arranging a dozen or more flues of the same shape in a strip shape, but even when the entire carbonization chamber and combustion chamber are renovated, if this hot transshipment method is adopted, labor saving, The construction period can be shortened.

  In order to mold a large-sized precast block refractory, a longer time is required for casting molding compared to a normal small-sized one. In the case of colloidal silica bond type castable refractories, during high temperature and low humidity, fluidity decreases due to evaporation of moisture, resulting in insufficient filling of the molded product. There is a problem in terms of ease of construction and formability, such as cracks occurring on the side of the body. When colloidal silica is used as a curing agent for large precast block refractories, the yield and production efficiency are lowered.

  Since the siliceous refractory for hot transshipment for a coke oven is built on the inner wall of a coke oven kept at around 500 ° C., it is required to have thermal shock resistance. When normal siliceous refractories composed of crystalline silica such as tridymite and cristobalite are exposed to a rapid temperature change from room temperature to 500 ° C, the crystalline silica expands rapidly due to the phase transition, causing damage such as cracks. To do. In general, siliceous refractories for hot transshipment for coke ovens are designed to suppress the thermal expansion coefficient of the entire compact by replacing part or all of crystalline silica with low-expansion fused silica, thereby providing thermal shock resistance. Improves resistance. As the hot-replaceable siliceous refractories for coke ovens, there are bricks and castable block refractories, and the castable block refractories are classified into colloidal silica type and Portland cement type depending on the type of binder.

Since colloidal silica does not contain impurities such as CaO and Al ₂ O ₃ compared to alumina cement and Portland cement, a castable refractory having a considerable quality of silica brick is obtained. On the other hand, castable refractories that have the gelling action of colloidal silica as a curing agent, when water evaporates during casting, the viscosity increases and fluidity decreases, and a sufficiently filled construction body is obtained. There are problems such as not. In particular, when casting a large-sized precast block refractory in a high-temperature, low-humidity atmosphere, the casting time is longer than that of a small-sized one.

Since Portland cement has a lower Al ₂ O ₃ content than alumina cement, when it is used as a siliceous refractory, the amount of CaO—Al ₂ O ₃ —SiO ₂ -based low melting point produced is reduced at high temperatures. Further, as is apparent from the general concrete curing agent, a high-strength molded body can be obtained, which is suitable as a curing agent for large siliceous castable block refractories. However, since Portland cement contains about 4% of Al ₂ O ₃ , the amount of the low-melting-point material generated is higher than that of a castable refractory that is hardened by the gelling action of colloidal silica. Further, since Portland cement hydrate is dehydrated at around 600 ° C., castable refractories using Portland cement as a curing agent exhibit shrinkage with volume change. Therefore, the addition amount of Portland cement for siliceous castable refractories exposed to a high temperature of 1200 ° C. or higher is desirably a small amount as long as necessary strength is exhibited.

  Patent Document 6 proposes a refractory composition mainly composed of fused quartz in which 2 to 10% of Portland cement and 1 to 8% of silica ultrafine powder are blended with fused quartz as a main raw material. The siliceous refractory mainly composed of fused quartz exhibits a large shrinkage in the thermal expansion curve under load at 1000 ° C. to 1300 ° C. even with fused quartz brick not containing a curing agent. In Patent Document 6, the lower limit of the amount of Portland cement is set to 2%, but even at 2%, the shrinkage due to dehydration of Portland cement is large, and under the load of 600 ° C to 1300 ° C with the above shrinkage of 1000 ° C to 1300 ° C added. The shrinkage indicated by the thermal expansion curve reaches 1% or more. Considering that the coke oven wall has a temperature difference between the carbonization chamber side and the combustion chamber maximum temperature part, the coke oven wall built with the cast refractory molded by the castable refractory shown in Patent Document 6 is cracked. And furnace wall inclination may occur.

  In general, refractories for hot repair use sintered silica and low-expansion fused quartz as an aggregate, and the use of fused quartz improves thermal damage resistance. Fused quartz has a property of crystallizing when exposed to high heat, and a refractory for hot repair using a large amount of fused quartz is likely to cause structural damage due to crystallization of fused quartz. Therefore, in the refractory for hot repair, it is necessary to optimize the blending ratio and particle size constitution of the sintered silica and the fused silica to cope with thermal and structural damage.

  The present invention has been made in view of the above-mentioned problems of the prior art relating to siliceous castable refractories, is excellent in thermal shock resistance during heating, and is suppressed from shrinkage under load at high temperatures, An object of the present invention is to provide a siliceous castable refractory and a siliceous precast block refractory that have good creep resistance, have sufficient curability in a timely manner, and can be easily applied to a large molded article.

The siliceous castable refractory according to the present invention is made of Portland cement as an outer shell with respect to 100% by mass of a siliceous refractory raw material composition composed of fused silica, crystalline silica composed of cristobalite and quartz, and ultrafine siliceous powder. It is a siliceous castable refractory to which 0.7 to ₂ % by mass, a water reducing agent is added to 0.03 to 0.3% by mass, and sodium silicate is converted to Na ₂ O in an amount of 0.04 to 0.30% by mass, The mixing ratio (total 100% by mass) of the siliceous refractory raw material composition is 96 to 70% by mass of fused silica, 0 to 20% by mass of crystalline silica composed of cristobalite and quartz, and 3.8 to 10% by mass of siliceous ultrafine powder. %.

  The siliceous castable refractory can include calcined silica as part of the siliceous refractory raw material blend. When the siliceous refractory raw material composition includes calcined silica, the blending ratio of the siliceous castable refractory raw material composition (total 100% by mass) is 96 to 70% by mass of fused quartz, crystalline silica 0 to 20 consisting of cristobalite and quartz. Mass%, calcined silica 10 mass% or less, siliceous ultrafine powder 3.8 to 10 mass%, and the total amount of the crystalline silica and the calcined silica is 20 mass% or less. The calcined silica has tridymite as a main component or tridymite and cristobalite as main components. In this case, the blending ratio of Portland cement is 0.7 to 1.3% by mass.

  According to the present invention, the thermal shock resistance at the time of heating is excellent, the shrinkage under load at high temperature is suppressed, the creep property at high temperature is good, and the curability is sufficient at an appropriate time. Even so, it is possible to provide a siliceous castable refractory and a siliceous precast block refractory that can be easily cast.

It is a conceptual diagram of a melting furnace for producing fused quartz, and is a side view (a) and a plan view (b). It is a conceptual diagram of a parallel type precast block, The side view (a) and the top view (b). It is a conceptual diagram of a large-sized precast block, and is a plan view (a) and a side view (b).

Hereinafter, the siliceous refractory raw material composition, the curing agent and the water reducing agent of the siliceous castable refractory according to the present invention will be described more specifically.
(Siliceous refractory raw material composition)
The siliceous castable refractory according to the present invention uses fused silica, crystalline silica, and ultrafine siliceous powder as a siliceous refractory raw material composition.
As fused quartz, silica glass mainly composed of α-type quartz produced in nature and acid-treated to remove impurities is melted at a high temperature of 2000 ° C. or higher and rapidly cooled and solidified, or from a solution of metal alkoxide. A high-purity fused quartz obtained by preparing a porous gel of quartz glass by a hydrolysis method and drying and firing the gel can be used.

As the crystalline silica, crystalline silica composed of cristobalite and quartz obtained as a by-product from a portion that did not reach a temperature at which the silica stone melts at the time of the production of the above quartz glass, or tridymite as a main component is used. A calcined silica or a calcined silica mainly composed of tridymite and cristobalite is used.
Silica flour and / or fused quartz ultrafine powder is used as the siliceous ultrafine powder. Silica flour is dust collection dust produced as a by-product during the production of metallic silicon and silicon alloys. The fused silica ultrafine powder is a spherical particle having an accumulated average particle diameter (a diameter giving a height of 50% in the cumulative distribution diagram, also referred to as D50) of 1 μm or less.

The mixing ratio (total 100% by mass) of fused silica, crystalline silica, and ultrafine siliceous powder in the siliceous refractory raw material blend is a crystalline substance composed of cristobalite and quartz obtained as a by-product when crystalline silica is produced in quartz glass. In the case of silica, the fused silica is 96 to 70% by mass, the crystalline silica is 0 to 20% by mass (including 0% by mass), and the siliceous ultrafine powder is 3.8 to 10%.
When the proportion of crystalline silica composed of cristobalite and quartz exceeds 20% by mass, the thermal shock resistance decreases. Since silica used as a raw material for quartz glass is treated with hydrochloric acid and impurities are removed, this crystalline silica is as high in purity as fused silica and has a SiO ₂ content of 99.5% or more. . For this reason, even if a large amount of crystalline silica composed of cristobalite and quartz is used, there is no reduction in hot creep resistance as in the case of using a lot of calcined silica.

  The blending ratio (total 100% by mass) of fused silica, crystalline silica, and siliceous ultrafine powder in the siliceous refractory raw material composition is replaced with a part or all of crystalline silica composed of cristobalite and quartz as crystalline silica. When using calcined silica, 96 to 70% by mass of fused silica, 0 to 20% by mass (including 0% by mass) of crystalline silica composed of cristobalite and quartz, 10% by mass or less (not including 0% by mass) of calcined silica, The siliceous ultrafine powder is 3.8 to 10% by mass. In this case, the total amount of crystalline silica (crystalline silica composed of cristobalite and quartz and calcined silica) is 20% by mass or less (not including 0% by mass), and the calcined silica is composed mainly of tridymite, And / or a material mainly composed of tridymite and cristobalite. When the blending ratio of the calcined silica exceeds 10% by mass, the expansion curve under load at high temperature exhibits remarkable shrinkage, or the hot creep deformation ratio increases.

  The calcined silica mainly composed of tridymite, for example, is obtained by crushing used siliceous bricks to adjust the particle size. And those whose particle sizes are adjusted by pulverization) can be used. The used siliceous brick has an X-ray diffraction intensity ratio of tridymite and cristobalite of about 100 to 10 or more, and in the present invention, the one having such an X-ray intensity diffraction ratio is called calcined silica with tridymite as a main component. . In addition, the unused siliceous brick has an X-ray diffraction intensity ratio of tridymite and cristobalite generally in the range of 100 to 90 to 140, and in the present invention, those having such an X-ray diffraction intensity ratio are treated with tridymite and cristobalite. It is called calcined silica with the main component.

  Of the ultrafine siliceous powder, silica flour is spherical and exhibits a remarkable water-reducing effect when used in combination with a dispersing agent. This phenomenon is physically said to be a ball bearing effect due to the shape of microsilica. Fused quartz ultrafine powder also exhibits a remarkable water-reducing effect when used in combination with a dispersant, similarly to silica flour. When the molded product obtained by hydro-kneading the castable refractory is dried, the portion where water was present becomes voids. Therefore, if the amount of added water is reduced to reduce the voids, the strength of the molded product increases. As the amount of the siliceous ultrafine powder increases, the amount of added water decreases and the strength of the molded body increases. When the blending amount of the siliceous ultrafine powder exceeds 10%, water reduction does not appear for the blending amount, and the viscosity of the kneaded product becomes excessive, which takes time for the molding operation. The surface energy of siliceous ultrafine powder is high, and has the effect of preventing strength deterioration associated with dehydration of Portland cement at 400 ° C to 800 ° C. On the other hand, if the blending amount of the siliceous ultrafine powder is less than 3.8% by mass, the effect of increasing the strength of the molded article or preventing the strength deterioration is small due to insufficient quantity.

Fused silica ultrafine powder is highly pure, but silica flour contains several mass% impurities. In Examples described later, SiO ₂ content of fused silica ultrafine is 99.7%, SiO ₂ content of silica flour was 97.1%. Silica flour has a trace amount of water-soluble components. If the amount of water-soluble components or the pH varies, the flowability and curing time of castable refractories are affected. Moreover, when silica flour is used frequently, impurities increase, the amount of low melting point products generated at high temperatures increases, and creep resistance decreases. In order to reduce the amount of impurities in the siliceous refractory raw material composition, the addition amount of silica flour is preferably 6% by mass or less.

(Curing agent)
The castable refractory according to the present invention uses Portland cement as a curing agent. As the Portland cement, it is desirable that the content of CaO and SiO ₂ as main components is large and the content of impure components such as Al ₂ O ₃ is small, and ordinary Portland cement, early strength Portland cement, white Portland cement, etc. are suitable. Can be used. When Portland cement is frequently used as a castable refractory, the volume change accompanying dehydration occurs from around 600 ° C. in the temperature rising process, resulting in significant shrinkage. Also, the amount of Al ₂ O ₃ mixed from Portland cement increases and CaO− The amount of Al ₂ O ₃ —SiO ₂ -based low-melting point product increases, resulting in high temperature degradation. Accordingly, the amount of Portland cement added is desirably a small amount as long as the strength of the molded body is sufficiently developed.
The amount of Al ₂ O ₃ mixed in the castable refractory according to the present invention varies depending not only on the amount of Portland cement but also on the type of raw materials used in the siliceous refractory raw material blend and the amounts of various raw materials. Since the calcined silica contains several percent Al ₂ O ₃ , the addition amount of Portland cement in the case where 0-10% by mass of calcined silica is contained in the siliceous refractory raw material composition is 0.7- 1.3% by mass. Since crystalline silica produced as a by-product during the production of quartz glass contains almost no Al ₂ O ₃ , the amount of Portland cement added when it does not contain calcined silica is 0.7-2.0 mass% as an outer shell. Preferably, the content is 1.5% by mass or less.

The castable refractory according to the present invention is to be poured into a mold by adding water, but the pot life that can maintain the softness of pouring is required to be 0.5 hours or more, and the frame is removed. It is required that the curing time until it becomes as hard as possible is within 72 hours. Further, the pot life is preferably 1 hour or longer and the curing time is preferably within 24 hours.
Portland cement addition amount used as a curing agent for the castable refractory according to the present invention is in the range of 0.7 to 1.3% by mass or 0.7 to 2.0% by mass, and is a small amount. It is cured within the necessary curing time by using together. As the curing accelerator, known materials such as sodium silicate, calcium chloride, sodium chloride and sulfate can be used.

As described above, the refractory material using a large amount of fused quartz is remarkably shrunk under load at 1000 ° C. to 1400 ° C. even in a brick. When the fused quartz is exposed to a high temperature for a long time, it will crystallize to become β-tridymite and / or β cristobalite having a relatively low density and expand. Alkali has an effect of promoting crystallization, and in the castable refractory according to the present invention, crystallization is performed in a temperature rising process of 1000 ° C. to 1400 ° C. by adding 0.04 to 0.30 mass% of the Na ₂ O component. And the shrinkage under load is suppressed.
When an alkali salt such as sodium silicate or sodium chloride is used as a curing accelerator, it is possible to obtain the amount of Na ₂ O component necessary for suppressing shrinkage under load. However, when an amount of Na ₂ O that provides a sufficient effect for suppressing shrinkage under load is added as a curing accelerator, the necessary pot life may not be obtained due to excessive curing acceleration. Moreover, the use of curing accelerator which does not contain alkali such as calcium chloride, Na 2 _O component added need to alleviate the load under contraction required separately. In such a case, it is possible to add a Na ₂ O component necessary for relaxation under load by adding hardly soluble sodium silicate.

Slightly soluble sodium silicate is pulverized material (cullet) before autoclaving, which is obtained by melting cinnabar sand and sodium hydroxide at a high temperature and then cooling. The powder or aqueous solution obtained by dehydrating this after autoclaving is generally called sodium silicate. It is what. Sodium silicate is readily soluble in water and has a hardening accelerating action, whereas poorly soluble sodium silicate has a much lower solubility in water and less hardening accelerating action than sodium silicate.
In the present invention, with respect to 100% by mass of the siliceous refractory raw material composition, the sodium silicate to be added as an outer shell is an easily soluble sodium silicate, a hardly soluble sodium silicate, or a mixture of an easily soluble sodium silicate and a hardly soluble sodium silicate. The amount of addition is 0.04 to 0.30% by mass in terms of solid Na ₂ O.

(Water reducing agent)
Since the castable refractory of the present invention has a very small amount of Portland cement used as a curing agent, in order to make the molded body have sufficient strength, a siliceous aggregate composition is provided with siliceous ultrafine powder and water is reduced. It is desirable to use a highly effective water reducing agent. The water reducing agent used in the present invention is preferably a polyether carboxylic acid type, and the amount added is 0.03 to 0.3% by mass on the basis of 100% by mass of the siliceous aggregate composition. Further, inorganic electrolytes such as naphthalene, melamine sulfonic acid condensate, and sodium phosphate can also be used.

(Organic fiber)
As described above, castable refractories using Portland cement as a curing agent are more likely to explode in the process of heating and heating compared to the case where the gelling action of alumina cement or colloidal silica is used as a curing agent. In the castable refractory material of the present invention, it is desirable to add 0.03 to 0.2% by mass of organic fiber to the siliceous refractory aggregate composition in order to avoid explosion. As the organic fibers, chemical fibers having a fiber length of 3 to 15 mm, such as polypropylene, polyethylene, and polyvinyl alcohol, can be used.

[Common subject matter]
Unused silica bricks that are out-of-standard or useless as fired silica stones mainly composed of tridymite and cristobalite, using spent silica brick scraps that have been refurbished after use for a long time in a hot stove as fired silica stones mainly composed of tridymite Waste was used. About 300 kg of used silica brick waste and unused brick waste were collected at random, crushed and mixed to 3 mm or less, and divided into particle sizes of 3-1 mm, 1-0.150 mm, and 0.150 mm or less.

Randomly sample 2Kg from used silica bricks and unused silica bricks crushed and mixed to 3mm or less. The crystal phase was examined. The crystal phase was analyzed by X-ray diffraction method. Table 2 shows chemical components of used silica brick waste and unused silica brick waste, and Table 3 shows crystal layers and X-ray diffraction intensities. For both used and unused silica bricks, low-temperature tridymite and low-temperature cristobalite were observed in the crystal phase. In Table 3, the X-ray diffraction intensity (maximum diffraction intensity) of cristobalite is a relative value when the X-ray diffraction intensity (maximum diffraction intensity) of tridymite is 100.
Spent silica brick waste is mainly composed of tridymite, and unused silica brick waste is mainly composed of tridymite and cristobalite.

  Fused quartz is produced by heating and melting silica at a temperature exceeding the melting temperature (1723 ° C.) and then rapidly cooling it. The structure of a melting furnace for producing fused quartz used in the present invention is shown in FIG. In this type, a SiC heating element 2 is installed at the center of a circle of a cylindrical metal container 1 having a diameter of about 1 m and a length of about 2 m, and the heating element 2 is heated by electricity. As the silica that is a raw material of the fused quartz, high-purity silica that has been subjected to acid treatment to remove impurities is used, which is placed in the metal container 1 and heated and melted. The metal container 1 and the heating element 2 are disposable, and after heating and melting, the metal container 1 and the metal container 1 are cooled with water, disassembled, and a fused quartz portion is collected. Fused quartz is a high-purity amorphous product having a SiO2 content of 99.5% by mass or more, and this was divided into 5-3 mm, 3-1 mm, 1-0.150 mm, and 0.150 mm or less.

The silica in the metal container 1 is not completely melted, but there is an opaque silica layer having a width of several centimeters in the portion below the melting temperature along the container side wall 3 away from the heating part of the heating element 2. . Silica stone collected from this opaque silica layer is referred to as crystalline silica in the following examples.
Obtain about 400Kg of this crystalline silica ore, pulverize to 3mm or less, mix and collect 2Kg at random, further reduce to 100g with a bifurcater, and then pulverize the whole amount to obtain the chemical components and crystals The phase was examined. The crystal phase was analyzed by X-ray diffraction method.
Table 4 shows the chemical components of fused silica and crystalline silica, and Table 5 shows the crystalline phases of fused silica and crystalline silica. Low-temperature cristobalite and low-temperature quartz were recognized as crystalline phases of crystalline silica. In Table 4, the diffraction intensity (maximum diffraction intensity) of the low-temperature type quartz is a relative value when the diffraction intensity (maximum diffraction intensity) of the low-temperature type cristobalite is 100.
The crystalline silica pulverized and mixed to 3 mm or less was further divided into particle sizes of 3-1 mm, 1-0.150 mm, and 0.150 mm or less.

The siliceous ultrafine powder used in the present invention is of two types: silica flour and fused quartz ultrafine powder. As the silica flour, a product having a SiO ₂ content of 97.1% by mass was used. The fused quartz ultrafine powder is a spherical particle having a SiO ₂ content of 99.7% by mass and an accumulated average particle size of 1 μm or less.
As the water reducing agent, a polyether polycarboxylic acid system was used.
As the organic fiber, polypropylene having a fineness of 2.2 dtex, a fiber diameter of 18 μm, and a fiber length of 5 mm was used.
The water added to the castable refractory of the present invention was tap water. The numerical value of the amount of added water is the ratio (outer coating) of added water to the siliceous refractory raw material composition, and is expressed in mass%.

[Test 1]
The fused silica and crystalline silica are used as the siliceous refractory raw material composition (aggregate), the mixing ratio of both aggregates is changed, and the siliceous ultrafine powder is converted to 100 mass% of the raw material composition containing 8 mass%. In contrast, Portland cement is 1.0% by mass, sodium silicate is 0.02% by mass in terms of solid Na ₂ O, and sparingly soluble sodium silicate is 0.07% in terms of solid Na ₂ O. %, Organic water-reducing agent 0.2% by mass, organic fiber 0.05% by mass, water 5.5% by mass added, kneaded, molded, de-framed, and using refractory specimens obtained, Measurement of values (bulk specific gravity, compressive strength, thermal expansion coefficient, thermal expansion coefficient under load, creep value), thermal shock resistance evaluation test, and explosion resistance evaluation test were performed.
For the kneading, a universal testing machine manufactured by Dalton Co., Ltd. was used. The softness of the castable refractory after kneading was almost the same in Examples 1 to 4 and Comparative Example 1. Molding was performed using a vibration table manufactured by Hayashi Vibrator Co., Ltd. under conditions of a frequency of 50 Hz and a vibration time of 5 minutes. Using the castable refractories after kneading and molding, the pot life and curing time at room temperature (25 ° C.) were measured.

A part (about 500 g) of the castable refractory after kneading was put in a plastic bag and stored in a thermostatic bath maintained at a constant temperature of 25 ° C., and used for measuring the pot life. At this time, the bag mouth of the plastic bag was closed with a rubber band and stored in a thermostatic bath so that the castable refractory was not dried. Check the fluidity of castable refractories every 15 minutes with the touch and visual sense, and use the time from kneading until the fluidity is lowered (flowiness is lowered enough to cause insufficient filling by vibration construction method). It was time (assuming T1). If no decrease in fluidity was confirmed after 72 hours had elapsed from the start of the pot life measurement, the subsequent measurement was stopped.
Castable refractories that have been judged to have deteriorated in fluidity are placed on a vibration table with plastic bags and subjected to vibration for 5 minutes to increase the density. Then, the fluidity is confirmed again as described above, and the decrease in fluidity is re-established. When confirmed, the pot life of the castable refractory was determined as T1. This castable refractory was returned to the thermostat for curing time measurement. On the other hand, if fluidity decline was not reconfirmed (fluidity returned), it was returned to the thermostatic bath again, and after 15 minutes, the plastic bag was placed on the vibration table again and subjected to vibration for 5 minutes. In this case, when the fluidity was reconfirmed, the pot life of the castable refractory was determined to be T1 + 15 minutes. If the fluidity decline was not reconfirmed, the above process was repeated. Table 6 shows the pot life.

The curing time is the time from when kneading until strength is developed to such an extent that the molded body can be removed without damage. In this example, the strength of the castable refractory for measuring the curing time is confirmed every 30 minutes, and the time until the strength is developed to such an extent that the castable refractory is not crushed or cracked by arm force is defined as the curing time. did. Table 6 shows the curing time.
On the other hand, a part of the castable refractory after the kneading was poured into a mold conforming to the provisions of JIS R2553, and the entire mold was cured in the same thermostatic bath as described above, and this was used for confirmation of curing. During curing, the castable refractories were covered with a plastic sheet to prevent drying. When the castable refractory for curing time measurement reached the curing time, the castable refractory for curing confirmation was taken out of the thermostatic chamber and de-framed to check whether it could be de-framed normally. Moreover, the compressive strength after 1 day curing was measured according to the prescription | regulation of JISR2553. In addition, about the Example of this invention, all were able to remove a frame normally at the time of hardening time arrival, and all the compressive strengths after 1 day curing were 5 MPa or more.

The test piece for bulk specific gravity and compressive strength test was molded using a molding die described in JIS-R-2553. The compressive strength was measured in accordance with JIS-R-2553. Table 6 shows the measured values of bulk specific gravity and compressive strength after drying at 110 ° C. for 24 hours and after baking at 1200 ° C. (heating rate 5 ° C./min) for 3 hours.
The coefficient of thermal expansion was measured in accordance with JIS-R-2207-1 (visible light projection method). Table 6 shows the measured values of the coefficient of thermal expansion at 1000 ° C.

  The thermal expansion coefficient and creep value under load were measured in accordance with JIS-R-2658 using a hot creep test furnace (SRC-15 type) manufactured by Shinagawa Refractories Co., Ltd. with a pressure of 0.2 MPa. did. Table 6 shows measured values of the coefficient of thermal expansion under load when the temperature reaches 1400 ° C. Then, it kept at 1400 degreeC for 50 hours as it was, and measured the thermal expansion coefficient under the load after holding for 50 hours. Table 6 shows the difference between the thermal expansion coefficient under load after holding at 1400 ° C. for 50 hours and the thermal expansion coefficient under load when reaching 1400 ° C. as a creep value.

The thermal shock resistance evaluation was performed by using a test body which was molded into a cube having a side of 100 mm, dried at 110 ° C. × 24 hours and then naturally cooled, and placed in an electric furnace maintained at 600 ° C. or 1200 ° C. for 30 minutes. After the elapse of time, the specimen was taken out from the electric furnace into a normal room and naturally cooled, and then the appearance of the specimen was observed with the naked eye. Thermal shock resistance was evaluated by the presence or absence of cracks. The results are shown in Table 6.
In the explosion resistance evaluation test, a cube having a side of 60 mm was formed, put into an electric furnace held at 600 ° C. immediately after being removed from the frame, and evaluated by exploding or not exploding. The castable refractory composition and the kneading water were stored in a thermostat kept at 25 ° C., and the kneaded and vibration-treated one was cured in the same thermostat until de-framed.

  As shown in Table 6, in all of Examples 1 to 4 and Comparative Example 1, the compressive strength is 20 MPa or more, which is the standard for silica brick for coke ovens, and the thermal expansion coefficient under load when reaching 1400 ° C. is −0. It was in the range of 30 to 0.16%, and the results of the creep resistance and explosion resistance evaluation tests were also good. On the other hand, the results of the thermal shock resistance evaluation test were good in Examples 1 to 4, whereas in Comparative Example 1, the blending ratio of crystalline silica exceeded the provisions of the present invention and the blending of fused quartz The ratio was less than that of the present invention, and cracks occurred.

[Test 2]
As a siliceous refractory raw material composition (aggregate), fused quartz, crystalline silica and calcined silica stone are used, and the composition ratio of the three aggregates is changed, and the raw material composition 100 containing 8% by mass of siliceous ultrafine powder 100 Portland cement is 1.0% by mass, sodium silicate is converted to solid Na ₂ O, 0.02% by mass, and sparingly soluble sodium silicate is converted to solid Na ₂ O. 0.07% by mass, 0.2% by mass of organic water reducing agent, 0.05% by mass of organic fiber, and 5.5% by mass of water, and using a refractory test piece obtained by kneading, molding and de-framed In the same manner as in [Test 1], measurement of physical properties, thermal shock resistance evaluation test, and explosion resistance evaluation test were performed. Table 7 shows the results of using silica (mainly used silica brick) containing tridymite as a main component as the calcined silica. Table 8 shows the results of using unused silica bricks (mainly cristobalite and tridymite) as calcined silica.

  As shown in Table 7, in Examples 5 to 8, the aggregate blending ratio is 72 to 82% by mass of fused silica, 10% by mass of crystalline silica, and 0 to 10% by mass of used silica stone brick, all of which are compressed. The strength is 20 Mpa or more, which is the standard for coke oven bricks, and the coefficient of thermal expansion under load when reaching 1400 ° C. is in the range of −0.20 to −0.31%, and the creep resistance and thermal shock resistance As a result of the evaluation test, the result of the explosion resistance evaluation test was also good. On the other hand, in Comparative Example 2, the proportion of used silica brick exceeds the provisions of the present invention, the proportion of fused silica is less than the provisions of the present invention, and the thermal expansion coefficient under load when reaching 1400 ° C. is large. As a result of the thermal shock resistance evaluation test at 1200 ° C., cracks occurred.

  As shown in Table 8, in Examples 9 to 11, the aggregate blending ratio was 72 to 77% by mass of fused silica, 10% by mass of crystalline silica, and 0 to 10% by mass of unused silica brick, and all were compressed. The strength is 20 Mpa or more, which is the standard for coke oven bricks, and the thermal expansion coefficient under load when reaching 1400 ° C. is in the range of −0.11 to −0.16%, and the creep resistance and thermal shock resistance As a result of the evaluation test, the result of the explosion resistance evaluation test was also good. On the other hand, in Comparative Examples 3 to 4, the total blending ratio of crystalline silica and unused silica brick exceeds the provisions of the present invention, and the blending ratio of fused silica is less than the provisions of the present invention, and the thermal shock resistance evaluation test As a result, cracks occurred. Moreover, the comparative example 4 in which the mixture ratio of an unused silica brick exceeds the prescription | regulation of this invention showed the shrinkability with a large thermal expansion coefficient under load.

[Test 3]
Comparative Examples 5, 6 and Examples 12 and 13, same as Example 3 using fused silica and crystalline silica, where the siliceous refractory raw material composition (aggregate) is fused quartz, crystalline silica and used silica brick For Examples 14 and 15 and Comparative Example 7 which were the same as Example 7 used, the amount of Portland cement to be added as an outer shell was changed, physical property values were measured in the same manner as in [Test 1], and thermal shock resistance was used. An evaluation test and an explosion resistance evaluation test were performed. The results are shown in Table 9. Table 9 also shows post-curing compressive strength measurements after 1-day curing or 3-day curing.

  In Example 12, Example 3, and Example 13, the amount of Portland cement added is within the specified range of the present invention (0.7 to 2% by mass), and the compressive strength is 20 MPa or more which is the standard for coke oven bricks. The thermal expansion coefficient under load when reaching 1400 ° C. is in the range of 0.06 to −0.27, and the results of the creep resistance and thermal shock resistance evaluation test and the explosion resistance evaluation test are also shown. It was good. On the other hand, in Comparative Example 5, the amount of Portland cement added was 0.5 mass%, which was less than that of the present invention, and the compressive strength after drying at 110 ° C. × 24 h was less than 20 MPa. In Comparative Example 6, the amount of Portland cement added was 3% by mass, exceeding the definition of the present invention, the thermal expansion coefficient under load when reaching 1400 ° C. was −0.65%, and the creep deformation ratio was also large.

  The amount of Portland cement added in Example 14, Example 7, and Example 15 is within the specified range of the present invention (0.7 to 1.3% by mass), and the compressive strength is 20 MPa, which is the standard for coke oven bricks. The coefficient of thermal expansion under load when reaching 1400 ° C. is in the range of 0.03 to −0.3%, and the results of creep resistance, thermal shock resistance evaluation test, and explosion resistance evaluation test are also obtained. It was good. On the other hand, in Comparative Example 7, the amount of Portland cement added was 1.6% by mass, exceeding the regulation of the present invention, the thermal expansion coefficient under load when reaching 1400 ° C. was −0.50%, and the creep deformation ratio was also large.

The compressive strength after daily curing and after drying (110 ° C. × 24 h) of Example 3, Example 7, Examples 12 to 15 and Comparative Examples 5 to 7 shown in Table 9 increase in the amount of Portland cement added. Along with it. In the case of insufficient strength after curing, corner breakage is liable to occur when the frame is removed, so it is desirable that the curing strength is large.
When fused silica and crystalline silica are used as the siliceous refractory raw material composition, the appropriate addition amount range of Portland cement is 0.7 to 2% by mass, whereas as the siliceous refractory raw material composition, When fused silica, crystalline silica, and used silica brick are used, the appropriate addition amount range of Portland cement is 0.7 to 1.3% by mass, and Portland cement cannot be used much as compared with the former.

[Test 4]
As a siliceous refractory raw material composition (aggregate), crystalline silica and fused silica are used, and with respect to 100% by mass of the raw material composition in which the mixing ratio of the ultrafine siliceous powder is changed, sodium silicate and difficult The total amount of soluble sodium silicate is 0.09% by mass in terms of solid Na ₂ O, 0.2% by mass of organic water reducing agent, 0.05% by mass of organic fiber is added, and the softness of the castable refractory is constant. Using the refractory specimen obtained by adjusting the amount of water added, kneading, molding, and de-framed, the measurement of physical properties and the thermal shock resistance evaluation test, An explosive evaluation test was conducted. The results are shown in Table 10. In addition, in the column of the raw material blends of Examples 16 to 18 and Comparative Examples 8 and 9 in Table 10, the total of each refractory raw material exceeds 100% by mass.

  Examples 3 and 16 to 18 in which the blending ratio of the siliceous ultrafine powder is within the specified range of the present invention (3.8 to 10% by mass when the total of each refractory raw material is 100% by mass) The compressive strength is 20 MPa or more, which is the standard for coke oven bricks, the thermal expansion coefficient under load when reaching 1400 ° C. is in the range of −0.30 to −0.04%, and the creep resistance is also good. The results of the thermal shock resistance evaluation test and the explosion resistance evaluation test were also good. On the other hand, Comparative Example 8 in which the mixing ratio of the siliceous ultrafine powder is 3% by mass has a relatively large amount of added water, the compressive strength after drying at 110 ° C is less than 20 MPa, and the expansion coefficient under load when reaching 1400 ° C is -0.38%. In Comparative Example 9 in which the mixing ratio of the siliceous ultrafine powder was 12% by mass, explosion occurred as a result of the explosion resistance evaluation test.

[Test 5]
As a siliceous refractory raw material composition (aggregate), crystalline silica, unused silica brick and fused quartz are used, and it is externally applied to 100% by mass of the raw material composition in which the mixing ratio of siliceous ultrafine powder is changed. The total of sodium silicate and sparingly soluble sodium silicate is 0.09% by mass in terms of solid Na ₂ O, 0.2% by mass of organic water reducing agent, 0.05% by mass of organic fiber is added, and castable refractory Using the refractory test piece obtained by adjusting the amount of added water so that the softness is constant, kneading, molding, and de-framed, measurement of physical properties and thermal shock resistance in the same manner as in [Test 1] An evaluation test and an explosion resistance evaluation test were performed. The results are shown in Table 11. In the column of raw material blends of Example 21 and Comparative Example 11 in Table 11, the total of each refractory raw material exceeds 100% by mass.

  Examples 10 and 19 to 21 in which the blending ratio of the siliceous ultrafine powder is within the specified range of the present invention (3.8 to 10% by mass when the total of each refractory raw material is 100% by mass) The compressive strength is 20 MPa or more, which is the standard for coke oven bricks, the thermal expansion coefficient under load when reaching 1400 ° C. is in the range of −0.29 to −0.15%, and the creep resistance is also good. As a result of the thermal shock resistance evaluation test, the result of the explosion resistance evaluation test was also good. On the other hand, Comparative Example 10 in which the mixing ratio of the siliceous ultrafine powder is 3% by mass has a relatively large amount of added water, the compressive strength after drying at 110 ° C. is less than 20 MPa, and the expansion coefficient under load when reaching 1400 ° C. is -0.43%. In Comparative Example 11 in which the blending ratio of the siliceous ultrafine powder is 12% by mass, the test specimen placed in the electric furnace maintained at 1200 ° C. was cracked as a result of the thermal shock resistance evaluation test. As a result, cracks occurred.

[Test 6]
With respect to 100% by mass of the refractory raw material composition in which the blending ratio of crystalline silica, fused silica, and siliceous ultrafine powder is constant, the amount of sodium silicate and sparingly soluble silicate soda is changed on the outside, Portland cement, Using a refractory test piece obtained by adding water-reducing agent, organic fiber and water in constant amounts, kneading, molding, and de-framed, measuring physical properties and heat shock resistance in the same manner as [Test 1] An evaluation test and an explosion resistance evaluation test were conducted. The results are shown in Table 12.

Example 3 and Examples 22 to 13 in which the amount of the outer addition of the amount of sodium silicate and / or the hardly soluble sodium silicate is within the specified range of the present invention (in terms of Na ₂ O, 0.04 to 0.30% by mass). No. 24 has a compressive strength of 20 MPa or more, which is the standard for coke oven bricks, and a thermal expansion coefficient under load when reaching 1400 ° C. is in the range of −0.24 to −0.07%, and is resistant to creep. The results of the evaluation test for the heat resistance, the thermal shock resistance and the explosion resistance evaluation were also good. On the other hand, in Comparative Examples 12 and 13, the total amount of sodium silicate and hardly soluble sodium silicate was 0.00 or 0.02% by mass in terms of solid Na ₂ O, and the expansion coefficient under load when reaching 1400 ° C. However, they showed large shrinkage at −1.06% and −0.58%, respectively. In Comparative Example 14, the total amount of sodium silicate and hardly soluble sodium silicate is 0.40% by mass in terms of solid Na ₂ O, and the creep deformation rate is large.

[Test 7]
Raw material containing 8% by mass of siliceous ultrafine powder, using crystalline silica, fused silica and spent silica brick as a siliceous refractory raw material composition (aggregate), with a constant mixing ratio of these three types of aggregate The amount of the organic fiber is changed as an outer shell with respect to 100% by mass of the blend, and 1.0% by mass of Portland cement, 0.02% by mass of sodium silicate converted to solid Na ₂ O, and hardly soluble sodium silicate 0.07% by mass in terms of solid Na ₂ O and 0.2% by mass of organic water reducing agent are added, and the amount of water added is adjusted so that the softness of the castable refractory is constant, kneading, molding, de-framework Using the refractory specimens obtained in this manner, the physical property values, the thermal shock resistance evaluation test, and the explosion resistance evaluation test were performed in the same manner as in [Test 1]. The results are shown in Table 13.

  In Examples 7 and 25 to 27, the amount of the organic fiber outer sheath added is within the specified range (0.03 to 0.20% by mass) of the present invention. Brick is 20 MPa or more which is a standard, and the thermal expansion coefficient under load when reaching 1400 ° C. is in the range of −0.22 to −0.30%, and the creep resistance, thermal shock resistance evaluation test, The result of the explosiveness evaluation test was also good. On the other hand, in Comparative Example 15 in which the amount of the outer coating of the organic fiber was 0.02% by mass, cracks occurred as a result of the explosion resistance evaluation test. In Comparative Example 16 in which the outer fiber addition amount of the organic fiber is 0.3% by mass, the amount of added water is relatively large, the compressive strength after drying at 110 ° C. is less than 20 MPa, and the expansion coefficient under load when reaching 1400 ° C. is -0.54%, showing high shrinkage.

[Test 8]
As the siliceous refractory raw material mixture (aggregate), the used silica brick and fused quartz are used, the mixing ratio of both aggregates is changed, and the raw material mixture containing 8% by mass of siliceous ultrafine powder is 100% by mass. On the other hand, the amount of Portland cement was changed as an outer shell, and the sodium silicate was converted to solid Na ₂ O at 0.02% by mass, and the hardly soluble sodium silicate was converted to solid Na ₂ O at 0.05% by mass. %, Organic water-reducing agent 0.2% by mass, organic fiber 0.05% was added, the amount of water added was adjusted so that the softness of the castable refractory was constant, and kneaded, molded, and unframed. Using the refractory test pieces, physical property values, thermal shock resistance evaluation tests, and explosion resistance evaluation tests were performed in the same manner as in [Test 1]. The results are shown in Table 14. In the column of raw material blends of Examples 28 and 29 in Table 14, the total of each refractory raw material exceeds 100% by mass.

  In Examples 1, 28, and 29, the compressive strength is 20 MPa or more, which is the standard for coke oven bricks, and the thermal expansion coefficient under load when reaching 1400 ° C. is in the range of −0.37 to −0.14%. The results of the creep resistance and thermal shock resistance evaluation tests and the explosion resistance evaluation tests were also good.

[Test 9]
Castable refractories for coke oven hot transfer are excellent in thermal shock resistance during heating, with reduced shrinkage under load at high temperature, low creep deformation rate at high temperature, and sufficient hardening in a timely manner And those that can be easily cast and molded are suitable. In the laboratory tests of [Test 1] to [Test 8] above, select an example suitable for a castable refractory for coke oven hot transfer, after curing, after drying, after firing at 1000 ° C., after firing at 1200 ° C., The bending strength and compressive strength after firing at 1400 ° C. were measured according to JIS-R-2553. The results are shown in Table 15.

The compressive strength after firing in each example shown in Table 15 is all greater than the compressive strength after curing and the compressive strength after drying.
On the other hand, the bending strength after drying of each example is higher than the bending strength after curing. In each example, the bending strength after baking at 1000 ° C. and / or 1200 ° C. is inferior to the bending strength after drying, but the bending strength after baking at 1400 ° C. is larger than the bending strength after baking at 1000 ° C. and / or 1200 ° C. In Example 13, the content of Portland cement is the highest, and the strength after curing and the strength after drying are the largest.
The raw material composition of Example 1 does not contain crystals and is all glassy. The bending strength after firing at 1200 ° C. is remarkably reduced, but the bending strength after firing at 1000 ° C. is the largest in Example 1, and from the bending strength after drying. The rate of decline is the smallest.

  In Examples 1, 28, and 29, compared to Examples 13, 7, 15, and 10, the raw material blend has a high glass phase content and a low crystal phase content. In the present invention, sodium silicate and hardly soluble sodium silicate are added to promote crystallization of fused quartz and to suppress shrinkage under load at high temperature. 1200 ° C. is a temperature range in which the crystallization speed of the fused silica increases, and a structural change occurs inside the test piece. In Examples 7, 15, and 10 having a relatively large crystal phase content, the bending strength after firing at 1200 ° C. is almost equal to the bending strength after firing at 1000 ° C. because there is little influence due to crystallization of fused quartz. Is done.

Examples 13, 7, 15, 10, 28, and 29 have a SiO ₂ crystalline phase composed of low-temperature type cristobalite and / or low-temperature type tridymite and / or low-temperature type quartz. These SiO ₂ crystalline phases undergo a phase transition from a low temperature type to a high temperature type in a temperature range of 150 to 600 ° C., and exhibit rapid expansibility. The decrease in bending strength after firing at 1000 ° C. is presumed to involve some degree of phase transition of the SiO ₂ crystalline phase. Since Example 1 does not have a SiO ₂ crystalline phase, there is almost no decrease in bending strength after firing at 1000 ° C.
In order to avoid structural spalling due to crystallization of fused quartz and thermal spalling due to transition of SiO ₂ crystalline phase, the bending strength after firing at 1200 ° C. and 1000 ° C. is It is presumed that a material that does not significantly decrease the bending strength is more desirable. The bending strength after firing at 1200 ° C. and 1000 ° C. in Examples 7, 15, and 10 has a small strength reduction rate from the bending strength after drying. In Example 28, since the content of Portland cement is the smallest, the strength is inferior to that of the other examples, but the strength change due to firing is small.

[Test 10]
Examples 13, 15, 10, and 28 shown in Table 16 have a difference in the amount of Portland cement added as an outer shell within a range of 2 to 0.7% by mass, and bending strength and compressive strength after curing and after drying. The size also follows the amount of Portland cement added (see Table 15).
The precast block refractory is generally molded and dried at a precast manufacturing factory. For Examples 13, 15, 10, and 28, normal and large-sized precast block refractories were actually manufactured at a precast block refractory manufacturing plant, and after normal vibration molding, curing, deframement, and drying, normal castable block refractories were manufactured. It was tested whether a dried product could be obtained.

At this time, a vortex mixer was used for kneading, and the vibration molding time was 15 minutes for the normal precast block and 50 minutes for the large precast block. All were deframed after curing at 25 ° C. × 24 h, dried in a dryer at 300 ° C. × 24 hours (temperature increase rate 1 ° C./min), and then naturally cooled in a normal room.
FIG. 2 shows a schematic diagram of a parallel type precast block refractory (mass after drying of about 15 kg), and FIG. 3 shows a schematic diagram of a large precast block refractory (weight after drying: about 550 kg).
For large precast refractories, the hoist type crane installed on the factory ceiling should be used when it is necessary to lay the formwork sideways when unframed, and when the molded product is lifted, suspended, and moved after drying. This was done using a suspension belt or suspension clamp. The precast block refractory production test results are shown in Table 16.

Examples 13, 15, 10, and 28 could all be molded as normal, parallel-type precast block refractory dried products.
The removal of large-sized precast block refractories exceeding 500Kg is carried out by using a hoist crane or forklift to lay the molded product on its side or upside down. The corners and dowels of the molded product are placed on the floor surface. It can be easily damaged by contact with the claws of the formwork and forklift.
In Example 28, compared with Examples 13, 15, and 10, the amount of Portland cement added is small, the curing strength is small, and careful removal work is required.
All of the large precast block refractory dried products of Examples 13, 15, 10, and 28 were lifted and suspended by a hoist type crane equipped with a suspension clamp and a suspension belt, and the horizontal movement could be performed without any problem.

Claims (5)

With respect to 100% by mass of fused silica, crystalline silica composed of cristobalite and quartz, and 100% by mass of siliceous refractory raw material composed of ultrafine siliceous powder, 0.7-2% by mass of Portland cement is used as a water reducing agent. Is a siliceous castable in which 0.04 to 0.30 mass% is added in terms of 0.03-0.3 mass% and sodium silicate converted to solid Na ₂ O, and the composition of the siliceous refractory raw material composition A siliceous castable refractory characterized in that the proportion is 96 to 70% by mass of fused silica, 0 to 20% by mass of crystalline silica composed of cristobalite and quartz, and 3.8 to 10% by mass of siliceous ultrafine powder. 0.7 to 1.3 Portland cement is externally applied to 100% by mass of the fused silica, crystalline silica composed of cristobalite and quartz, calcined silica, and siliceous refractory raw material composition composed of siliceous ultrafine powder. mass%, and 0.03 to 0.3 mass% of water-reducing agent, a silica castable refractory supplemented with 0.04 to 0.30 wt% in terms of sodium silicate into solid Na ₂ O, wherein The blending ratio of the siliceous refractory raw material composition is 96 to 70% by mass of fused quartz, 0 to 20% by mass of crystalline silica composed of cristobalite and quartz, 10% by mass or less of calcined silica, and 3.8 to 10% by mass of siliceous ultrafine powder. %, And the total amount of the crystalline silica and the calcined silica is 20% by mass or less. The siliceous castable refractory according to claim 2, wherein the calcined silica is composed mainly of tridymite, or mainly composed of tridymite and cristobalite. The silica stone according to any one of claims 1 to 3, comprising 0.03 to 0.20 mass% or less of organic fiber as an outer shell with respect to 100 mass% of the siliceous refractory aggregate composition. Quality castable refractory. A siliceous precast block refractory obtained by adding water to the siliceous castable refractory according to any one of claims 1 to 4, kneading, pouring into a mold and drying.

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