JPH05155653A - Method for manufacturing lime refractory - Google Patents

Abstract

(57) [Summary] [Purpose] Instead of lime refractory made from limestone,
Hydration resistance is significantly improved, and lime-based refractory materials are manufactured using food industry waste. [Structure] Shells are fired at 1,250 ° C. or higher and then crushed, and 5% or less of stearic acid or 5% or less of epoxy resin for preventing hydration is added and press-molded. This is fired at 1,100 ° C or higher to produce a lime-based refractory brick. After calcination at 1,250 ° C or higher, crush,
An amorphous refractory material can be obtained by adding 5% or less of calcium chloride for imparting adhesiveness. The shells mainly have an aragonite crystal structure, but when calcined, they can have a calcium oxide crystal structure like limestone. The crystals become significantly larger than in the case of limestone, and become a lime refractory with high hydration resistance. As a result, the increasing number of industrial wastes, shells, can be effectively used in the field of metal refining.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a lime-based refractory, and more particularly to a method for obtaining lime-based refractory bricks and amorphous refractories for metal refining by firing aragonite such as shells. Is.

[0002]

BACKGROUND OF THE INVENTION Naturally occurring limestone (calcium carbonate) is mostly used for cement and civil engineering construction, and is also used as lime for steelmaking and lime for chemical industry. That is, slaked lime (calcium hydroxide) obtained by calcining limestone to produce quick lime (calcium oxide) and further digesting it with water is widely used as a cement or a plastering material. This is because lime (quick lime, slaked lime) can utilize its hydraulic property, physical strength and alkalinity (basic). In recent years, the development of new uses of quicklime has been promoted, and quality has come to be emphasized rather than quantity. Examples thereof include static crushing agents utilizing hydration expansion, food heating agents utilizing heat of hydration, dental or industrial mold materials, and refractory materials such as crucibles and refractory bricks. The characteristics of quicklime, which is drawing attention as a refractory material, has a high coefficient of thermal expansion similar to magnesium oxide, and
This is because it has an important function as a refractory material having an extremely high melting point and also has thermodynamic stability. By the way, since calcium oxide obtained by firing calcium carbonate is hydrated, part of it becomes hydrated calcium hydroxide, so crucibles and refractory materials such as refractory bricks made from calcium oxide are manufactured and transported. ， Provides quality deterioration prevention measures at each stage of storage and actual use,
It is necessary to maintain hydration resistance. Therefore, methods such as adding an additive that promotes crystal growth, increasing the sintering temperature, forming a protective film, and reducing the specific area to lower the porosity are adopted. .. As the above additives, Al, Fe, Ti, Si, Mg, Cr, Z
There are oxides such as r, Ce, Sn, V, P and Mo. For sintering, for example, the temperature is set to 2,100 ° C., or as described in US Pat. No. 2,971,240, the temperature is rapidly increased to 540 ° C. within 5 minutes and to 820 ° C. within 15 minutes. It is necessary to raise the temperature. As the protective coating, metal spraying, metal vacuum deposition, synthetic resin, coumarone resin, oil, tar, paraffin wax, vitreous material, etc. are adopted. By the way, calcium carbonate includes calcite (calcite), aragonite (aragonite), vaterite (μ-calcium carbonate), and the like. Naturally occurring calcium carbonate is not only limestone, but also shells, such as pearl oysters, scallops, oysters, oysters, and coral remains. Limestone is calcite, and shellfish are mostly aragonite, and their crystal structures are different. It is known that when shells are heated to 440 ° C or higher, aragonite is transformed into stable calcite. As described above, when limestone is fired, CO ₂ is released to become CaO, but the same is true when the shells are fired, and becomes NaCl type tetragonal crystals.

[0003]

According to the research to date, the size of calcium oxide crystals produced by burning shells having a different crystal structure, chemical composition, and composition from limestone is the same as that of limestone. It is said that it is the same as that generated by On the other hand, it is known that refractory products made of calcium oxide with large crystals are less likely to come into contact with air containing water vapor than those with small crystals, and have excellent hydration resistance. .. By the way, in Japan, limestone, which has abundant reserves, is also increasing in mining amount, and the supply amount is not expected to be large in the future. On the other hand, nowadays, catching and aquaculture of shellfish has become popular, and the amount of shells discarded from fisheries factories after food processing is increasing rapidly. However, these shells are only used in some fields such as fertilizers, and are treated as industrial wastes without establishing effective utilization methods. For this reason, there is a need to take measures against pollution at a disposal site, etc., because of a bad odor.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce the occurrence of pollution by utilizing the industrial waste of shells brought by the food industry such as shellfish. Focusing on the fact that when aragonite such as calcination is turned into the same calcite as limestone, we aim to use it as a lime-based refractory material and realize a stable lime-based refractory material that is less dandruff than when manufactured from limestone. , A method for producing a lime-based refractory that enables high hydration resistance to be exhibited without taking special measures at each stage of production, transportation, storage and actual use. That is. By the way, as described above, in spite of the existing concept that the crystals produced by burning shells have the same size as the calcite crystals of limestone, in the study of the present inventors, It was found that the calcined calcium oxide crystals are larger than the calcite-structured natural limestone calcined calcium oxide crystals, and the present invention has been completed based on this finding.

[0005]

[Means for Solving the Problems] In the present invention, shells such as shells, coral remains and hailstones are fired at 1,250 ° C. or higher. After crushing it, 5% or less of stearic acid or 5% or less of epoxy resin for preventing hydration is added. Then, it is press-molded and fired at 1,100 ° C. or higher to obtain a lime-based refractory brick. In addition, the shells are fired at 1,250 ° C. or higher and then crushed, and 5% or less of calcium chloride is added to impart adhesion, and 5% or less of stearin is added to prevent hydration and improve fluidity. It is to add an acid to form an amorphous fireproof material. Furthermore, shells are crushed to 1 mm or less, and water is added to 5 mm.
After granulating to 20 mm and drying, 1,250 ℃
5% to prevent hydration after baking and adjusting the particle size
It is also possible to add the following stearic acid or 5% or less of an epoxy resin, press-mold it, and fire it at 1,100 ° C. or higher to obtain a lime-based refractory brick. At this time, 10% or less of calcium chloride is preferably added to the water for granulation. In addition, the shells are pulverized to 1 mm or less, water is added to granulate the mixture to 5 mm to 20 mm, and after drying, 1,
After baking at 250 ° C or higher and adjusting the particle size, 5% or less of calcium chloride is added to impart adhesion, and 5% or less of stearic acid is added to prevent hydration and improve fluidity. It can be a standard refractory material. Also at this time, it is preferable that the water for granulation contains 10% or less of calcium chloride.

[0006]

[Operation] Shells are crushed after firing at 1,250 ° C or higher. This granular material has an aragonite crystal structure, but has the same calcite crystal structure as limestone. 5% or less of stearic acid or 5% or less of an epoxy resin is added to this powder or granular material to enhance the hydration preventing effect. And
Put in a mold and press-mold. Molded product at 1,100 ℃
When fired as above, it becomes a lime-based refractory brick. Calcium oxide produced by burning shells is much larger than calcium oxide obtained by burning calcite, which is limestone. Since the large crystals suppress the hydration property, the hydration resistance is higher than that of the lime-based refractory made from limestone and the hydration resistance is higher. Therefore, the deterioration at each stage of production, transportation, storage and actual use is extremely small, and the handling is easy. Further, it is not necessary to add an expensive metal oxide that promotes crystal growth, and a high temperature is not required or a rapid temperature rise is required even in firing.
By using shells, industrial waste in the food industry can be used as lime refractory in a metal refining furnace, which reduces waste disposal and suppresses pollution with foul odor. The shells are fired at 1,250 ° C. or higher and then ground, and 5% or less of calcium chloride is added. This addition improves the adhesion of the powder or granules. By adding 5% or less of stearic acid for preventing hydration and improving fluidity, an amorphous fireproof material is obtained. When this is sprayed onto the furnace wall of the refining furnace, it is fired at a temperature rise during refining and can function as a refractory material for the furnace body. 5% or less stearic acid for hydration prevention after crushing shells to 1 mm or less, adding water to granulate to 5 mm to 20 mm, drying and firing at 1,250 ° C. or more, and adjusting particle size Or, press molding by adding less than 5% of epoxy resin to 1,100
When fired at a temperature of ℃ or above, a lime-based refractory brick can be obtained as described above. When the water for granulation contains 10% or less of calcium chloride, the granulation is promoted. Crush shells to 1 mm or less, add water to 5 m
1,250 ℃ after granulating to 20mm
After baking and adjusting the particle size, 5% or less of calcium chloride for imparting adhesiveness and 5% or less of stearic acid for preventing hydration and improving fluidity can be added to give an amorphous form. A refractory material can be obtained. If the granulated water in this case also contains 10% or less of calcium chloride,
The granulation effect is further improved.

[0007]

The method for producing a lime refractory material according to the present invention will be described in detail below. After the shellfish is separated from the shells, the shellfish brought into the fisheries processing plant are considered as fresh food, dried food, and highly processed canned food. On the other hand, the discarded shells are heated to 1,250 ° C or higher in a baking factory attached to a fish processing plant. During the calcination, the shells having an aragonite crystal structure transform into a stable calcite crystal structure at 440 ° C. or higher, and then C ₂ is released while releasing CO _2.
It is generated in aO (calcium oxide). The shells taken out from the firing kiln are air-cooled and then crushed into powder particles of 1 mm or less by a crusher such as a mill. By the way, the shells after firing are brittle, and their crushing is relatively easy.

The crystals of quicklime thus fired and ground are larger than the crystals of quicklime fired from natural limestone. The state can be clearly understood from the electron micrograph. FIG. 1 is a 300 times magnified photograph, in which (A) is a calcium oxide crystal structure obtained by burning limestone, and (B) is a calcium oxide crystal structure obtained by burning a shell. It can be seen that the quicklime crystals obtained by burning the shells are larger than the quicklime crystals obtained by burning the limestone. This is (A) and (B) of FIG. 2 which is a 2,000 times photograph, and FIG.
It can be understood more clearly from (A) and (B).
By the way, in the past, it was believed that the size of calcium oxide crystals produced by burning shells having a different crystal structure from limestone was the same as that produced by burning limestone. This has 44 aragonite shells
It is recognized that the crystal structure is the same and the size does not change in the same calcite because it has transformed into calcite when it exceeds 0 ° C and both are calcite. Is imagined. However, in reality, as can be seen from the above photograph, the sizes of the crystals are significantly different. The reason for this is not clear, but the difference in size always appears, so the specific area of calcium oxide in the shell is lower than that of calcium oxide in limestone, and the porosity is low. This means that it is difficult for air or the like to enter between the crystal structures, and the internal structure does not come into contact with air, and in the end, dandruff does not easily reach the inside of the crystal. Therefore, contact with air containing water vapor is reduced,
Higher hydration resistance. Also in the hydration test, it was proved from the fact that no dandruff phenomenon was observed in the calcium oxide of the shell.

The calcium oxide of the shell thus produced is pulverized as described above, and as a binder for further preventing hydration and for strengthening the molecular bond of quick lime, the amount of calcium is 5% or less. Stearic acid is added. This is put into a brick forming die and press-formed at 1 t / cm ² or more. It should be noted that oil or the like to be a protective film may be added together before charging to the molding die. Molding pressure is 1
It may be, for example, 3 t / cm ² which is larger than ton. When this molded product is fired at 1,100 ° C., it becomes a lime-based refractory brick for refining which has dandruff-resistant properties and high fire resistance. The molded product is not limited to a refractory brick, and can be a lime-based crucible. As can be seen from the above description, the industrial waste of shells brought by the food industry can be used as a lime-based refractory, and the occurrence of pollution can be prevented. Then, a stable lime-based refractory having higher hydration resistance than that produced from limestone can be obtained. Therefore, no special measures are required to prevent deterioration at each stage of production, transportation, storage, and actual use, and the lime-based refractory is extremely easy to handle. In addition, expensive metal oxides that promote crystal growth are not intentionally added as additives. In addition, it is not necessary to consider the heating such as raising the temperature or rapidly raising the temperature during sintering.

Although stearic acid is used in the above description, 5% by weight or less of an epoxy resin may be added instead. In either case, it is possible to exert a binder effect as well as prevent hydration. By the way, the shell has an aragonite crystal structure, but the remains of corals and hailstones that have the same structure may be used. Also,
It seems that some of the shells are not aragonite, but calcium oxide having large crystals as described above can be obtained in the same manner, and a lime-based refractory having high hydration resistance can be manufactured.

The above is the case of using a lime-based refractory brick, but the case of manufacturing an amorphous refractory material for stamping or spraying for repairing the refractory wall of the furnace body will be described. Similar to the above-mentioned manufacturing method, first of all,
After calcination at ℃ or more, crush. Then, not more than 5% by weight of calcium chloride is added in order to impart the adhesiveness to the fire wall and the like. Further, 5% by weight or less of stearic acid is added to prevent hydration and improve fluidity. If such an amorphous lime-based refractory material is blown onto the furnace wall, when the refining furnace operates and the inside of the furnace reaches 1,100 ° C. or higher, the lime-based refractory material is spontaneously fired. When calcium chloride is added with water as described above, it melts at a low temperature of 772 ° C, producing a melt that wets well low solids. Moreover, there is an advantage that when heated at a high temperature, the compound is changed to a stable compound or volatilized and disappears, and no adverse effect remains after firing. This is because the addition of salts causes CaO crystals to grow large and form a dense skeleton. In addition, the addition of CaCl ₂ causes a significant shrinkage in a low temperature range as compared with CaO without addition, and the effect that the dense sintered body becomes difficult to hydrate is exhibited. The use of the above-mentioned lime-based refractory material and amorphous refractory material prevents the impurities from being mixed into the molten steel, and is extremely effective when manufacturing high-grade steel or hydrogen storage alloy. Of course, it can also be applied to converters, ladle and tundish. Above all,
In the case of melting scrap, it is stable against impurities such as plating that adhere to the scrap, and is suitable as a refractory material for an electric steelmaking furnace.

Next, different manufacturing methods will be described. In all of the above, the shells were crushed after firing, but first, the shells are crushed to 1 mm or less. Then, water is added to the granular material to granulate it to 5 mm to 20 mm. This is dried and then fired at 1,250 ° C. or higher. Adjust the particle size of the calcined product and use 5% or less of stearic acid or 5
Epoxy resin of less than% weight is added and press molding is performed.
If the molded product is fired at 1,100 ° C. or higher, a lime-based refractory brick can be obtained. On the other hand, after the above particle size adjustment, an amorphous fire-resistant material can be obtained by adding 5% by weight or less of calcium chloride for imparting adhesiveness in addition to addition of stearic acid and the like. This amorphous lime-based refractory material is blown onto the furnace wall and fired when the temperature inside the furnace reaches 1,100 ° C. or higher to obtain a lime-based refractory material. In the above two production methods, water for granulation may contain 10% or less of calcium chloride. CaCl ₂
As a result, adhesion is improved and granulation is promoted. However, since the chemical action of CaCl ₂ disappears as described above by baking before adjusting the particle size, it is necessary to affect the amount of CaCl ₂ added before baking at 1,100 degrees after adjusting the particle size. There is no.

As can be seen from the above description, the inventors of the present invention noticed a significant difference in the size between the calcite crystals of limestone and the calcium oxide crystals produced by calcining aragonite or calcite shells. It was also found that the lime-based refractory made of shells is highly resistant to hydration. As a result, the present invention has been devised, and the use of stearic acid for further improving the prevention of hydration is
This is a major feature.

[0014]

According to the present invention, a lime-based refractory similar to limestone having a calcite crystal structure can be realized mainly by using shells having an aragonite crystal structure. Moreover, the crystals are much larger than those of limestone, and it can be used as a lime-based refractory brick with significantly improved hydration resistance or as an amorphous fire-resistant material. Shells as a raw material to replace limestone, whose reserves have been decreasing, have been increasing rapidly as industrial wastes in recent years, and in order to reduce the waste treatment, prevent pollution, and effectively use resources, future social demands will increase. It is possible to provide a lime-based refractory material that can meet the above requirements.

[Brief description of drawings]

FIG. 1 is a photograph of a metal structure magnified 300 times taken with an electron microscope. (A) shows a fired limestone, and (B) shows a fired shell.

FIG. 2 is a 2,000 times magnified metal structure photograph taken by an electron microscope, where (A) is a fired limestone, (B)
Is a baked shell.

FIG. 3 is a 10,000 times magnified metallographic photograph taken by an electron microscope, (A) shows a fired limestone,
(B) is obtained by firing a shell.

Claims (6)

[Claims] 1. Shells are fired at 1,250 ° C. or higher and then crushed, and 5% or less of stearic acid or 5% or less of epoxy resin for preventing hydration is added and press-molded,
A method for producing a lime-based refractory, which comprises firing at 1,100 ° C. or higher to obtain a lime-based refractory brick. 2. Shells are fired at 1,250 ° C. or higher and then crushed to add 5% or less of calcium chloride for imparting adhesiveness, and 5% for preventing hydration and improving fluidity. A method for producing a lime-based refractory material, which comprises adding the following stearic acid to form an amorphous refractory material. 3. Shells are pulverized to 1 mm or less, water is added to granulate the mixture to 5 mm to 20 mm, dried and then calcined at 1,250 ° C. or higher to adjust the particle size and then to prevent hydration. A method for producing a lime-based refractory material, which comprises adding 5% or less of stearic acid or 5% or less of an epoxy resin, press-molding, and firing at 1,100 ° C. or more to obtain a lime-based refractory brick. 4. The method for producing a lime refractory material according to claim 3, wherein the water for granulation contains 10% or less of calcium chloride. 5. To pulverize shells to 1 mm or less, add water to granulate the mixture to 5 mm to 20 mm, dry and then bake at 1,250 ° C. or more to adjust the particle size to impart adhesiveness Of 5% or less of calcium chloride and 5% or less of stearic acid for preventing hydration and improving fluidity to form an amorphous refractory material. .. 6. The method for producing a lime refractory material according to claim 5, wherein the water for granulation contains 10% or less of calcium chloride.