JPH0624833A - Production of sintered compact of dolomite and magnesia - Google Patents

Abstract

PURPOSE:To efficiently produce a sintered compact of a dolomite or magnesia used for a dolomite or a magnesia clinker as a raw material for producing a refractory material for refining iron and steel, a slag making agent for steel making, a plaster, etc. CONSTITUTION:The sintered compact of a dolomite or magnesia is produced by crashing a dolomite raw ore or a natural magnesite, adjusting the average particle size so as to be at an average size on below of a carbonate crystal consisting of the dolomite raw ore and then firing at >=900 deg.C or >=550 deg.C, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to dolomite and magnesia clinker which are raw materials for producing refractory for refining steel, and light burned dolomite and light burn used as a slag forming agent and plaster for steelmaking. The present invention relates to a method of manufacturing magnesia.

[0002]

2. Description of the Related Art Dolomite and magnesia clinker, which are raw materials for refractories used for metal refining, mainly iron and steel refining, can be roughly classified into those by melting and those by burning. is there. In the melting method, a natural product is rarely used as a raw material in terms of purity, and the melting method itself has a disadvantage in that the cost is high. As the method by firing, a method in which an auxiliary agent is added and fired while finely pulverizing or after finely pulverizing, or a coarse grain firing method in which an auxiliary agent is added to a raw material obtained by removing fine powder by classification and then firing is used. It is usually done. In the method of fine pulverization, flotation may be carried out after fine pulverization for the purpose of improving the purity. However, since SiO ₂ or Fe ₂ O ₃ is added as an auxiliary agent by the above-mentioned method, it is difficult to obtain a high-purity clinker.

On the other hand, when producing dolomite and magnesia, which are used as a slag forming agent for steelmaking, plasters, etc. I often do it. However, rough crystals of dolomite or natural magnesite are often large in size, and the crystals of the carbonates that make up the rough are often pulverized or collapsed during firing, which is likely to cause a decrease in yield.

The present application is a prior application by the present inventors. "Manufacturing method of lime sintered body" (Japanese Patent Application No. 4-1679)
16) and “Producing method of calcia clinker” (Japanese Patent Application No. 4-164869) are applied to dolomite and magnesia, and the physical properties of a sintered body to be obtained are The economic crushing particle size required for firing was clarified.

[0005]

The present invention is to produce dolomite and magnesia clinker having high specific gravity and excellent resistance to hydration without adding an auxiliary agent from rough dolomite and natural magnesite, and to light burning. The purpose is to efficiently produce dolomite and light-burned magnesia with low powder.

[0006]

[Means for Solving the Problem] The average particle size of the powder obtained by crushing rough dolomite or natural magnesite is adjusted to be equal to or smaller than the average crystal size of the carbonate constituting the raw material. After molding, 90 for Dolomite
By firing at 0 ° C or higher, and in the case of magnesia at 550 ° C or higher, high purity, high specific gravity and excellent hydration resistance are obtained in the clinker without addition of an auxiliary agent, but in the light burned product, it is excellent in hydration resistance. A highly efficient manufacturing method with less powdering is provided.

[0007]

[Function] If dolomite rough or natural magnesite is burned as a lump, many of the constituent carbonate crystals are large in size, causing pulverization and disintegration. Some of them collapse on their own. In the present invention, by crushing raw dolomite ore and natural magnesite as raw materials, the apparent crystal diameter is reduced to improve the sinterability, and by molding this, an appropriate void is formed in the molded body. By doing so, the strain at the time of firing is buffered to prevent pulverization and collapse.

In this case, if the particle size of the crushed powder is larger than the size of the carbonate crystal constituting the raw material, the crushed particle is an aggregate of several or more carbonate crystals of the raw material. Even if this is molded and fired, pulverization and disintegration due to strain during firing can be prevented, but calcination of crushed particles does not proceed, so pulverization due to peeling and falling is not improved. Therefore, it is necessary to improve the sinterability by crushing to the crystal size of the carbonate constituting the raw material or less and reducing the apparent crystal diameter. But in the case of natural magnesite,
When the crushed particle size is reduced, the water absorption may not be improved even if the bulk specific gravity is increased. This is different from dolomite in which the bulk specific gravity increases as the crushed particle size decreases, and the water absorption rate decreases.When manufacturing a magnesia sintered body, it is costly to crush the raw material more than necessary. It's useless.

The crystal size of the raw material carbonate is 0.2
In the case of a coarse crystal having a size of 5 mm or more, it may be difficult to mold even if it is crushed to a size not larger than the crystal size of the carbonate. At this time, the crushed particle size is less than 0.1 considering the moldability and handling strength.
It should be 2 mm or less.

The raw material powder obtained within the scope of the present invention can be molded by a general molding method such as press molding or extrusion molding, and a binder can be used if necessary. The molding density is 1.5g / c considering the friction between the molded products during firing and the refractory, the impact of dropping, etc.
It is desirable that it is m ³ or more.

The obtained molded body is then fired at 900 ° C. or higher for dolomite and 550 ° C. or higher for magnesite. Since the decarboxylation of dolomite and magnesite is completed at 900 and 550 ° C., respectively, it is necessary to calcine at a temperature higher than this.

[0012]

[Example] Raw dolomite ore A and natural magnesite B were prepared as raw materials. The cut surface of each raw material was polished and observed with a scanning electron microscope or optical microscope.
The carbonate crystal sizes of 0.13 mm and 3.
It was 5 mm. Each of A and B was crushed with a lump of about 35 mm, crushed with a hammer crusher and classified to 100 μm, and this powder was further crushed with a ball mill to prepare a powder having an average particle size of 4.5 μm. The powdered sample was formed into a disc-shaped compact at a pressure of 500 kg / cm ₂ using a die having a diameter of 40 mm. Then, the lump and the molded body are 110
Baking at 0, 1300, 1500 and 1700 ° C for 3 hours.

The bulk density, water absorption, and pulverization degree of the obtained sintered body were measured. However, the water absorption here is the weight increase rate when the dolomite sintered body is left for 120 hours and the magnesia sintered body is left for 30 days in a saturated vapor pressure at a temperature of 30 ° C. The degree is about 7 inside diameter
Approximately 60 rpm with 3 samples and 10 porcelain balls with a diameter of 10 mm placed in a porcelain pot of 5 mm and height of 120 mm
It is the generation rate of powder of 3 mm or less when rotated for 30 minutes.

The chemical analysis values of A and B are shown in Table 1 and the results are shown in Table 2. However, the lump of B was not described in Table 2 at each temperature because it collapsed and scattered during firing and a sintered body was not obtained. In both A and B, the smaller the pulverized particle size at each temperature, the smaller the pulverization rate, which is effective in preventing pulverization. For A, the smaller the crushed particle size is, the larger the bulk specific gravity is and the lower the water absorption is, which is effective for the hydration resistance. However, the water absorption rate did not decrease. Therefore, when producing a magnesia sintered body, it is necessary to determine the pulverized particle size based on physical properties such as the pulverization rate and the porosity of the sintered body.

[0015]

[Table 1]

[Table 2]

[0016]

EFFECTS OF THE INVENTION According to the present invention, dolomite and magnesia clinker having high purity and excellent hydration resistance can be produced without adding an auxiliary agent, or light burned dolomite and magnesia can be efficiently produced due to low powdering. it can.

Further, in addition to the dolomite rough stone powder or the natural magnesite powder within the scope of the present invention, calcium carbonate of Japanese Patent Application Laid-Open No. 4-130046, which is a prior application of the present inventors, and the above-mentioned "production of lime sintered body". By mixing limestone powder in the range of `` Method '', molding and firing, it is possible to freely set the ratio of calcium oxide and magnesium oxide, and to obtain a synthetic dolomite sintered body with low powder and excellent hydration resistance. Obtainable.

Claims (2)

[Claims] 1. After the molding, the average particle size of the powder obtained by crushing the dolomite raw ore is adjusted to be equal to or less than the average crystal size of the carbonate constituting the dolomite raw ore.
A method for producing a dolomite sintered body, which comprises firing at a temperature of 00 ° C or higher. 2. 550 ° after molding by adjusting the average particle size of the powder obtained by crushing natural magnesite to be equal to or less than the average size of the crystals of the carbonate constituting the natural magnesite. A method for producing a magnesia sintered body, which comprises firing at C or higher.