JP2012031006A - Fire-resistant heat-insulating brick, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a fire-resistant heat-insulating brick low in thermal conductivity relative to a clayey refractory and suitable for a heat insulating material without generating sulfur oxide in baking.SOLUTION: A calcium compound without containing sulfur, a pore imparting agent and water are added in a clay mineral containing SiOand AlOas main constituents to be kneaded, obtained slurry is cast, thereafter dried, and baked at a temperature ≥1,200°C. A main crystal phase of the obtained fire-resistant heat-insulating brick is anorthite. In the fire-resistant heat-insulating brick, compressive strength, a rate of residual linear change (1,250°C×12 h) and thermal conductivity (1,000°C) are ≥1.6 MP, ≤1% and ≤0.33 W/(m*K), respectively.

Description

  The present invention relates to a high-strength and low-heat-conducting fire-insulating brick used as a heat insulating material and a method for producing the same.

Brick or refractory whose main crystalline phase is anorthite (anorthite; CaAl ₂ Si ₂ O ₈ ) has a lower thermal conductivity than clay brick or refractory. Therefore, if anorthitic brick or refractory is used as a heat insulating material such as a heating furnace, there is an advantage that energy consumption can be reduced as compared with a conventional heat insulating material made of clay brick or refractory.

  In general, brick or refractory or ceramic structural materials whose main crystal phase is anorthite are kneaded by adding a compound containing calcium sulfate as a main component, such as gypsum, and water to clay minerals, and mixing the resulting slurry. It is manufactured by casting and then demolding after curing and firing. A compound mainly composed of calcium sulfate serves as a calcium source necessary for the formation of anorthite in addition to the function as a curing agent.

  For example, in US Pat. No. 4,248,637 (Patent Document 1), 10% by weight or more of gypsum is added and mixed in alumina or aluminosilicate, water is added and kneaded, and the resulting slurry is cast into a mold. After that, a method of producing an anorthitic sintered body having a porosity of 40 to 70% and a pore diameter of 0.75 to 8 μm by firing at 1000 to 1400 ° C. is described.

US Pat. No. 4,248,637

  In the above-described conventional anorthitic sintered body, that is, a method for producing a brick or a refractory or ceramic structural material whose main crystal phase is anorthite, calcium sulfate such as gypsum is used as a main component in the raw material. Therefore, the generation of sulfur oxide (SOx) was unavoidable during firing. Therefore, a flue gas desulfurization process for removing harmful sulfur oxides from the exhaust gas is required, and a flue gas desulfurization device has to be installed.

  In view of such conventional problems, the present invention provides an anorthitic brick or refractory material that has a lower thermal conductivity than ordinary clay bricks or refractories and has high strength and is suitable as a heat insulating material. An object of the present invention is to provide a method for producing sulfur without generating sulfur oxide during firing.

  In order to achieve the above object, as a result of intensive studies, the present inventors have added a calcium compound to the raw material without using gypsum (calcium sulfate) as a curing agent, and after casting and drying and firing. As a result, it has been found that a sintered body having a main crystal phase of anorthite and having excellent strength can be obtained, and the present invention has been achieved.

That is, insulating refractory bricks provided by the present invention, a SiO ₂ 35 to 50 wt%, the _Al 2 _{O 3} 35 to 50% by weight, include CaO 10 to 20 wt%, the major crystalline phase anorthite (CaAl ₂ Si ₂ O ₈ ) having pores, compressive strength of 1.6 MP or more, residual linear change rate (1250 ° C. × 12 hr) of 1% or less, and thermal conductivity (1000 ° C.) of 0.33 W / (m · K) or less.

In addition, the method for producing a refractory heat-insulating brick provided by the present invention includes kneading by adding a sulfur-free calcium compound, a pore-imparting agent, and water to a clay mineral mainly composed of SiO ₂ and Al ₂ O _3. Then, the obtained slurry is cast-molded, dried, and fired at a temperature of 1200 ° C. or higher.

  According to the present invention, anorthitic refractory heat-insulating bricks having lower thermal conductivity than ordinary clay refractories, high strength, and suitable as heat insulating materials can be produced without generating sulfur oxides during firing. can do. As a result, not only environmental pollution due to undesulfurized flue gas can be eliminated, but also the cost required for the flue gas desulfurization process and apparatus can be reduced, which is extremely advantageous from an economical viewpoint.

  Moreover, the refractory heat-insulating brick according to the present invention has a lower bulk specific gravity and lower thermal conductivity than a clay refractory, and also has a strength superior to that of a conventional anorthic refractory. Therefore, the fireproof heat-insulating brick of the present invention can be expected to save energy in operation by using it for construction of a heating furnace, and the application range such as use as a fireproof heat insulating material for structures requiring strength can be expanded. I can expect.

  In the method for producing a fireproof heat-insulating brick according to the present invention, a calcium compound not containing sulfur is used as a calcium source necessary for the formation of anorthite, instead of a conventionally used compound mainly composed of calcium sulfate such as gypsum. To do. As the calcium compound not containing sulfur, for example, calcium carbonate, calcium carbide, calcium oxide, calcium hydroxide, wollastonite, cement, and the like can be used.

Specifically, first, a calcium compound not containing sulfur, a pore-imparting agent and water are added to a clay mineral mainly composed of SiO ₂ and Al ₂ O ₃ and kneaded to form a slurry. After the obtained slurry is cast into a predetermined shape and then fired at a temperature of 1200 ° C. or higher, a fireproof and heat insulating brick can be obtained. If the temperature at the time of firing is less than 1000 ° C., the formation of anorthite is insufficient, and the residual line change rate of the obtained brick increases, so it is necessary to set it to 1200 ° C. or more, particularly 1250 to 1450 ° C. Is preferred.

The clay mineral is not particularly limited as long as it contains SiO ₂ and Al ₂ O ₃ as main components. For example, alumina-silica refractory clay, kaolinite, halloysite, and the like can be suitably used. As the composition of the clay mineral, with _Al 2 _{O 3} is 30 wt% or more, and a total of SiO ₂ and _Al 2 _{O 3} is 80 wt% or more. As the pore imparting agent, foam beads such as polystyrene and polypropylene, foaming agents, and the like can be used.

In each of the raw material powders, the amounts of CaO, Al ₂ O ₃ and SiO ₂ in all raw materials are composition ratios necessary for the synthesis of anorthite (CaAl ₂ Si ₂ O ₈ ), that is, the theoretical weight ratio of SiO ₂ / Al _{2. O 3 / CaO = 43/37} /20 may be blended so as to. For example, it is preferable to blend a clay mineral mainly composed of SiO ₂ and Al ₂ O ₃ in a proportion of 20 to 80% by weight and a calcium compound not containing sulfur in a proportion of 10 to 40% by weight.

  As a molding method of the slurry, cast molding in which the slurry is poured into a mold is used. After drying the obtained molded object, the fireproof heat insulation brick of this invention is obtained by baking at the temperature of 1200 degreeC or more. According to such a method of the present invention, since a calcium compound not containing sulfur is used as a calcium source necessary for the formation of anorthite, sulfur oxides are not generated during firing.

  The obtained refractory heat-insulating brick is finished by cutting or the like to obtain a product. The powder generated during the finishing process can be used as a raw material for the refractory heat-insulating brick. In addition, the addition ratio of this processed powder shall be less than 80 weight% of the whole raw material.

Insulating refractory bricks obtained by the present invention, the SiO ₂ and _Al 2 _{O 3} and CaO as main components, a SiO ₂ 35 to 50 wt%, the _Al 2 _{O 3} 35 to 50 wt%, 10 to 20 weight CaO %, The main crystalline phase is anorthite and has pores. Moreover, the fireproof heat insulating brick of the present invention has high strength and low thermal conductivity.

  Specifically, the compressive strength is 1.6 MP or more, the residual linear change rate (1250 ° C. × 12 h) is 1% or less, and the thermal conductivity is 0.33 W / (m · K) or less at 1000 ° C. The bulk specific gravity is 1.0 or less. The compressive strength was measured based on JIS R 2615, and the residual line change rate was measured based on ISO 2477. The thermal conductivity was measured based on ASTM C182. The bulk specific gravity was measured according to JIS R 2614.

  Although the compressive strength of the anorthitic refractory manufactured by the conventional method was about 1 MPa, the refractory heat-insulating brick according to the present invention has a compressive strength exceeding 1.6 MPa. The reason why the refractory heat-insulating brick of the present invention has high strength is that casting is peptized so that the clay is peptized in water, each raw material can be mixed uniformly, and each raw material reacts uniformly during firing, and anorthite It is conceivable that the continuity of surrounding solid portions (portions that support the brick structure) increases because of the precipitation of spherical independent pores.

[Example 1]
78 kg of powder of high-purity kaolin (SiO ₂ : 52 to 56 wt%, Al ₂ O ₃ : 42 to 44 wt%) as a clay mineral is added with 22 kg of calcium carbonate, 60 liters of polystyrene beads and 80 liters of water, and wet kneaded. To give a slurry. The slurry was cast and dried, and then fired at 1340 ° C. to produce a refractory heat insulating brick.

  The obtained fireproof heat insulating brick has a bulk specific gravity (JIS R 2614) of 0.67, a bending strength (JIS R 2213) of 2.3 MPa, a compressive strength (JIS R 2206) of 4.8 MPa, and a residual linear change rate. (ISO 2477, 1250 ° C. × 12 h) was 0.07%. The thermal conductivity (ASTM C182) is 0.18 W / (m · K) at 200 ° C., 0.21 W / (m · K) at 400 ° C., 0.25 W / (m · K) at 600 ° C., It was 0.29 W / (m · K) at 800 ° C. and 0.33 W / (m · K) at 1000 ° C.

[Example 2]
To 100 kg of fireproof heat insulating brick processed powder obtained in Example 1 above, 54 kg of high-purity kaolin powder, which is a clay mineral, and 16 kg of calcium carbonate, 100 liters of foam-imparting beads and 54 liters of water are added, Thoroughly wet-kneaded. The obtained slurry was poured into a mold, cast and molded, dried, and then fired at 1340 ° C. to produce a refractory heat-insulating brick.

  The resulting fireproof heat-insulating brick has a bulk specific gravity (JIS R 2614) of 0.52, a bending strength (JIS R 2213) of 1.3 MPa, a compressive strength (JIS R 2206) of 2.6 MPa, and a residual linear change rate. (ISO 2477, 1250 ° C. × 12 h) was 0.01%. Thermal conductivity (ASTM C182) is 0.16 W / (m · K) at 200 ° C., 0.19 W / (m · K) at 400 ° C., 0.22 W / (m · K) at 600 ° C., It was 0.26 W / (m · K) at 800 ° C. and 0.29 W / (m · K) at 1000 ° C.

Claims (3)

It contains 35 to 50% by weight of SiO ₂ , 35 to 50% by weight of Al ₂ O ₃ and 10 to 20% by weight of CaO, the main crystal phase is anorthite, has pores, and has a compressive strength of 1. A fireproof heat insulating brick characterized by having a residual line change rate (1250 ° C. × 12 h) of 1% or less and a thermal conductivity (1000 ° C.) of 0.33 W / (m · K) or less, 6MP or more. To a clay mineral mainly composed of SiO ₂ and Al ₂ O ₃ , a calcium compound not containing sulfur, a pore-imparting agent and water are added and kneaded, and the resulting slurry is cast and then dried, A method for producing a refractory heat-insulating brick, characterized by firing at a temperature of 1200 ° C or higher.   3. The sulfur-free calcium compound is at least one selected from calcium carbonate, calcium carbide, calcium oxide, calcium hydroxide, wollastonite, and cement. The manufacturing method of the fireproof heat insulation brick as described in.