JP2007055848A - Spherical magnesia-based clinker and refractory obtained by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide spherical magnesia-based clinker having high strength, excellent corrosion resistance or slag infiltration resistance and further excellent fluidity and filling property in refractory, and to provide a porous plug obtained using the same. <P>SOLUTION: The objective clinker is obtained by producing a spherical granulated material using a raw material composition capable of giving a chemical composition containing 90-99 wt.% MgO and 1-10 wt.% ZrO<SB>2</SB>, and firing the granulated material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a spherical magnesia-based clinker and a refractory obtained by using the same, and in particular, a refractory for lining in a molten steel container, a smelting furnace container or a kiln for firing cement or lime, etc. in the steel industry, or The present invention relates to a raw material for a basic refractory material that can be advantageously used for an indeterminate refractory material such as a castable or spray material, a repair material, and the like.

  Conventionally, metal oxides such as alumina, spinel, magnesia, zirconia, and silica have been widely used as refractory materials in the field of iron and non-steel production. Among them, magnesia is excellent in corrosion resistance. It is used as a main raw material for basic refractories (see Patent Document 1).

  However, when a conventional clinker (magnesia clinker) mainly composed of magnesia capable of exhibiting such excellent properties is used as a raw material for an amorphous refractory, for example, in the obtained amorphous refractory, There was a fear that sufficient corrosion resistance and slag infiltration resistance could not be exhibited. This is because a relatively large amount of water can be added to the compound in order to ensure the fluidity of the compound consisting of clinker, binder, etc. This is because a large amount of water present causes a large number of pores in the resulting amorphous refractory.

  In addition, when a refractory such as a porous plug is manufactured using a conventional magnesia clinker, the corner of the clinker is missing due to lack of strength and shape of the clinker during molding under high pressure in the manufacturing process. Therefore, the air permeability of the obtained refractory may be lowered due to the presence of fine clinker powder. That is, the conventional magnesia clinker has a problem that it is relatively difficult to produce a refractory having a desired air permeability.

  Furthermore, since magnesia has a very high melting point of about 2800 ° C., it was necessary to fire magnesia clinker having sufficient strength, porosity, etc. at an ultra-high temperature. At present, development of a novel magnesia-based clinker that can exhibit sufficient strength by firing at a low temperature is desired.

JP 49-6008 A

  Here, the present invention has been made in the background of such circumstances, and the problems to be solved are high strength, excellent corrosion resistance, excellent slag infiltration resistance, and a raw material mixture. An object of the present invention is to provide a spherical basic refractory material mainly composed of magnesia, that is, a spherical magnesia-based clinker, and a refractory obtained by using the same.

And in order to solve this problem, the first aspect of the present invention is a raw material composition capable of giving a chemical composition of MgO: 90 to 99 wt% and ZrO ₂ : 1 to 10 wt%. The spherical magnesia clinker is characterized in that it is made of a fired product obtained by producing a spherical granulated product and firing the granulated product.

Further, in the second aspect of the spherical magnesia clinker according to the present invention, MgO: 85-98.5 wt%, ZrO _2: 1 to 10 wt%, and TiO _2: 0.5 to 5 wt% A spherical granulated product is produced using a raw material composition capable of giving a chemical composition as described above, and a fired product obtained by firing such a granulated product is used.

Further, in the third aspect of the present invention, MgO: 75 to 97.5 wt%, ZrO _2: 1 to 10 wt%, TiO _2: 0.5 to 5 wt%, and, Al ₂ O ₃ , Fe ₂ O ₃ , NiO, ZrSiO ₄ and MnO are used to produce a spherical granulated product using a raw material composition capable of giving a chemical composition of 1 to 10 wt%, and the granulated product It is comprised in the baked product obtained by baking.

Furthermore, in the fourth embodiment of the spherical magnesia-based clinker according to the present invention, a ZrO ₂ source material, a TiO ₂ source material, an Al ₂ O ₃ is formed on the surface of the spherical granule obtained using the MgO source material. Using the coated granulated material in which a coating layer containing at least one of source material, Fe ₂ O ₃ source material, NiO source material, MnO source material and SiO ₂ source material is formed, It is comprised in the baked product obtained by baking.

  The gist of the present invention is also a refractory using the spherical magnesia-based clinker of each aspect as described above.

  Thus, in the first to fourth aspects of the spherical magnesia-based clinker according to the present invention, a spherical granulated product is produced using a raw material composition mainly composed of MgO, and the granulated product. Since it is composed of a spherical fired product obtained by firing the material, it can exhibit excellent strength as compared with the conventional magnesia clinker and also has excellent fluidity in the raw material composition. It is a thing.

In the second aspect of the spherical magnesia-based clinker of the present invention, TiO ₂ is blended in the raw material composition, and such TiO ₂ component is advantageously used as a sintering aid during firing. From the point of function, a spherical magnesia-based clinker exhibiting sufficient strength and the like can be obtained by firing at a temperature lower than the firing temperature when producing a conventional magnesia clinker.

Furthermore, in the third aspect of the present invention, in the raw material composition, in addition to the MgO component, the ZrO ₂ component and the TiO ₂ component, an Al ₂ O ₃ component, an Fe ₂ O ₃ component, a NiO component, a ZrSiO ₄ component And at least one of the MnO components is blended, and when a spherical granulated product obtained by using such a raw material composition is fired, a composite spinel is formed at the grain boundary of MgO in the obtained fired product. It is formed in an advantageous manner, so that a fired product (clinker) having better corrosion resistance and slag infiltration resistance is obtained.

On the other hand, in the fourth aspect of the spherical magnesia-based clinker according to the present invention, a ZrO ₂ source raw material, a TiO ₂ source raw material, Al ₂ is formed on the surface of the spherical granule obtained using the MgO source raw material. Using a coated granulated material in which a coating layer containing at least one of O ₃ source material, Fe ₂ O ₃ source material, NiO source material, MnO source material and SiO ₂ source material is formed, and this is fired Since the surface is coated with the fired product of the coating layer, the presence of the fired product of the coating layer allows MgO and moisture in the atmosphere and the like to be present. Can be effectively avoided, resulting in a clinker excellent in digestion resistance and also in its strength.

  Then, when such a spherical magnesia-based clinker of the present invention is used as a refractory material, for example, when a porous plug is manufactured, the clinker is spherical and has excellent strength. The generation of fine powder during high-pressure molding, which was a problem when using a clinker, can be advantageously suppressed, and thus the resulting porous has a desired air permeability, excellent corrosion resistance, and It exhibits slag resistance.

  By the way, when manufacturing the first to third aspects of the spherical magnesia-based clinker according to the present invention, first, a raw material composition mainly composed of MgO is prepared.

Specifically, in producing the spherical magnesia-based clinker of the first aspect of the present invention, an MgO source material that can give MgO by firing and a ZrO ₂ source material that can give ZrO ₂ by firing are used. In addition, when producing the spherical magnesia-based clinker of the second aspect, these MgO source raw material and ZrO ₂ source raw material and a TiO ₂ source raw material capable of giving TiO ₂ by firing are used, respectively, A product is prepared. Furthermore, when producing the spherical magnesia-based clinker of the third aspect of the present invention, an MgO source material, a ZrO ₂ source material and a TiO ₂ source material, and an Al ₂ O ₃ source capable of giving Al ₂ O ₃ by firing material, Fe ₂ O ₃ source material capable of providing the Fe ₂ O ₃ by firing, NiO source material capable of providing the NiO by sintering, ZrSiO ₄ source material capable of providing a ZrSiO ₄ by calcination, and, MnO source capable of giving the MnO by firing At least one of the raw materials is used to prepare the raw material composition.

Here, as the various raw materials used when preparing the raw material composition, any conventionally known various materials can be used as long as they can give the target component (MgO or the like) by firing. Is possible. For example, as the MgO source material, natural magnesia, seawater magnesia, magnesia clinker, magnesium hydroxide, electrofused magnesium, lightly burned magnesia and the like manufactured according to various known methods, and as the ZrO ₂ source material, Commercially available stabilized zirconia, unstabilized zirconia, and the like, and anatase type or rutile type titania, etc. can be used as the TiO ₂ source material. Further, as the Al ₂ O ₃ source material, calcined alumina, sintered alumina, electrofused alumina, artificial or natural spinel, etc., further, as the Fe ₂ O ₃ source material, a petal or the like, and NiO As the source material, generally available nickel oxide, etc., in addition, as the ZrSiO ₄ source material, zircon sand, zircon flour, etc., and as the MnO source material, generally used manganese oxide, etc. , Each can be used.

  Preparation of the raw material composition performed using such various raw materials is carried out so as to obtain a raw material composition capable of giving a predetermined chemical composition.

That is, in the spherical magnesia-based clinker according to the first aspect of the present invention, MgO: 90 to 99% by weight and ZrO ₂ : 1 to 10% by weight can be provided as a raw material composition capable of providing a chemical composition. A source material and a ZrO ₂ source material are blended. The ZrO ₂ is less than 1 wt%, there is a fear that the resulting clinker can not exhibit sufficient strength, the strength of the other hand, be contained a ZrO ₂ of more than 10 wt%, the effect of adding ZrO ₂ (clinker No significant improvement is observed in (Improvement), and since the ZrO ₂ source material is expensive, ZrO ₂ is incorporated in the raw material composition in a proportion of 1 to 10% by weight.

In the spherical magnesia clinker according to the second aspect of the present invention, MgO: 85 to 98.5% by weight, ZrO ₂ : 1 to 10% by weight, and TiO ₂ : 0.5 to 5% by weight. The MgO source material, the ZrO ₂ source material, and the TiO ₂ source material are blended so as to provide a raw material composition that can give a chemical composition. If TiO ₂ is less than 0.5% by weight, the effect of addition cannot be enjoyed, that is, TiO ₂ does not function effectively as a sintering aid, and it may be difficult to advantageously lower the firing temperature. In addition, from the viewpoint of cost-effectiveness, 5% by weight is sufficient as the upper limit of the content ratio of TiO ₂ .

Furthermore, in the spherical magnesia clinker according to the third aspect of the present invention, MgO: from 75 to 97.5 wt%, ZrO _2: 1 to 10 wt%, TiO _2: 0.5 to 5 wt%, and , Al ₂ O ₃ , Fe ₂ O ₃ , NiO and MnO, MgO source raw material, ZrO ₂ source raw material and TiO so as to be a raw material composition capable of giving a chemical composition of 1 to 10 wt% _The Al ₂ O ₃ source material, the Fe ₂ O ₃ source material, the NiO source material, the ZrSiO ₄ source material or the MnO source material are blended together with the _two source materials. If these Al ₂ O _{3 and the} like are less than 1% by weight, the effect of addition (improvement of corrosion resistance and slag infiltration resistance) may not be enjoyed, and even if Al ₂ O ₃ or more exceeding 10% by weight is blended, This is because no significant improvement is observed in the effect of addition.

  And when manufacturing the spherical magnesia-type clinker of the 1st thru | or 3rd aspect in this invention, a spherical granulated material is manufactured using the raw material composition prepared as mentioned above.

  That is, when a spherical granulated product made of a raw material composition capable of giving a predetermined chemical composition is calcined, the shape of the obtained calcined product (clinker) is also advantageously maintained. In addition to the corrosion resistance and slag infiltration resistance possessed by the baked product, a fired product (clinker) exhibiting excellent strength can be obtained.

  In addition, when the obtained fired product (clinker) is used as a refractory material when producing an amorphous refractory, for example, the raw material composition composed of the fired product (clinker), a binder, water, and the like is a fired product. Due to the spherical shape of the (clinker), the fluidity is excellent. Therefore, when producing an irregular refractory using the spherical magnesia clinker of the present invention, the amount of water in the raw material mixture is effectively reduced compared to the case of using a conventional magnesia clinker. As a result, the porosity of the obtained refractory is also advantageously reduced, and thus an amorphous refractory excellent in corrosion resistance and slag infiltration resistance can be obtained.

  Furthermore, when magnesia-carbon brick is produced using the obtained spherical fired product (clinker), the filling rate in the brick is improved, the porosity can be effectively reduced, and magnesia excellent in corrosion resistance. It becomes carbon brick.

  Furthermore, when a porous refractory such as a porous plug is produced using the obtained fired product (clinker), since the fired product (clinker) is spherical, the fired product is also obtained by high-pressure molding at the time of production. Refinement by crushing (clinker) is advantageously suppressed, and thus a porous refractory having a desired porosity can be obtained.

  Here, as a method for producing a spherical granulated product using a raw material composition composed of the MgO source raw material as described above, for example, water is added to the raw material composition to form a slurry, and then Dehydrate, extrude, or knead by adding a predetermined binder to the raw material composition, then molded with a briquette machine, or commercially available granulation such as a bread granulator or rotary mixer A technique such as granulation using a machine may be employed. In addition, as a binder used when manufacturing a spherical granule, various well-known things, for example, lignins, starches, polyvinyl alcohol, methylcellulose, various phenol resins, molasses, etc. are used in an appropriate ratio. It is done.

  The spherical pulverized product thus obtained is fired at a temperature of about 1500 to 2000 ° C. according to a normal firing operation, whereby the intended clinker is obtained as the fired product.

  By the way, when producing the fourth aspect of the spherical magnesia-based clinker according to the present invention, first, a spherical granulated product is produced using an MgO source material that can give MgO by firing.

  In addition, as an MgO source raw material used when manufacturing this spherical granulated material, it is possible to use any of the MgO source raw materials mentioned above. In addition, as a method for producing a spherical granulated product using them, the method for producing a spherical granulated product for producing the clinker according to the first to third aspects of the present invention described above and Similar approaches can be employed.

Next, on the surface of the obtained spherical granulated product, ZrO ₂ source material, TiO ₂ source material, Al ₂ O ₃ source material, Fe ₂ O ₃ source material, NiO source material, MnO source material and SiO ₂ source material At least one of them is used to form the coating layer.

Here, as the ZrO ₂ source material used when forming the coating layer, any of the above-described ZrO ₂ source materials can be used. Moreover, it is preferable that the thickness of the coating layer using such a ZrO ₂ source material is 10 to 30% of the diameter of the spherical granulated product. However, if the thickness of the coating layer is less than 10% of the diameter of the spherical granulated product, the effect of the coating layer described later may not be enjoyed advantageously, while the thickness of the coating layer is more than 30% of the diameter. This is because if it is thick, the resulting clinker may not exhibit the excellent corrosion resistance and slag infiltration resistance inherently possessed by MgO.

  And the target clinker is obtained as a baked product by baking the coated granulated material in which the coating layer was formed at the temperature of about 1500-2000 degreeC according to normal baking operation.

In the clinker thus obtained, the surface is covered with a fired product of a coating layer made of a ZrO ₂ source material and the like, so that excellent strength can be exhibited and spherical granulation is performed. Contact between the MgO component in the fired product and moisture in the air can be effectively avoided, and thus excellent digestion resistance is also exhibited.

  However, it goes without saying that the clinker thus obtained can exhibit the same effects as those of the clinker according to the first to third aspects of the present invention described above.

  Some examples of the present invention will be shown below to clarify the present invention more specifically. However, the present invention is not limited by the description of such examples. Needless to say. In addition to the following examples, the present invention includes various changes and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention, in addition to the specific description described above. It should be understood that improvements and the like can be added.

-Experimental Example 1-
Four raw material compositions having the composition shown in Table 1 below using light-burned magnesia as a MgO source material, stabilized zirconia as a ZrO ₂ source material, and rutile-type titania as a TiO ₂ source material. The lignins as a binder were added to each raw material composition together with water and kneaded, and spherical granules were produced using the obtained kneaded product. And 4 types of clinkers (clinker 1-4) were obtained by baking 4 types of spherical granulated materials at 1750 degreeC for 2 hours. The properties of each of the obtained clinker, that is, bulk specific gravity, apparent porosity, and compressive strength were measured, and the results are also shown in Table 1 below.

  The bulk specific gravity and the apparent porosity in the evaluation of the properties of the clinker are physical properties of particles obtained by sieving the obtained clinker to 3.35 to 1.70 mm, and are measured in accordance with JIS-R-2205. And obtained. Furthermore, the compressive strength is a physical property of the particles sieved to 2.0 to 1.7 mm, and was evaluated by a compression load value when the particles were broken by applying a compression load with an Amsler type compression tester.

  As is clear from the results of Table 1, the spherical magnesia clinker (clinker 2 to 4) according to the present invention has sufficient physical properties as a clinker despite being fired at a relatively low temperature (1750 ° C.). It was found to have

-Experimental example 2-
Using light-burned magnesia as the MgO source material, stabilized zirconia as the ZrO ₂ source material, rutile-type titania as the TiO ₂ source material, and calcined alumina as the Al ₂ O ₃ source material, MgO: A raw material composition having a chemical composition of 93% by weight, ZrO ₂ : 5% by weight, TiO ₂ : 2% by weight, and Al ₂ O ₃ : 1% by weight was prepared, and lignin as a binder was added thereto together with water. After kneading, a spherical granulated product was produced using the obtained kneaded product. The spherical granulated product was fired at 1900 ° C. for 10 minutes in a rotary furnace to obtain a spherical magnesia clinker (spherical MgO clinker) according to the present invention.

The obtained clinker and each component shown in Table 2 below were blended in the proportions (for porous refractory) and kneaded, and then loaded to 1 t / cm ² using an Amsler type compression tester. After the molded body thus obtained was dried, it was fired at 1700 ° C. for 2 hours to obtain a porous refractory sample (sample 2). On the other hand, a porous refractory sample (sample 1) was obtained according to the same technique using a commercially available MgO clinker and each component shown in Table 2 below. The porosity of each of the two types of samples thus obtained was measured according to the boiling method. The measurement results are also shown in Table 2 below.

  As apparent from the results in Table 2, the porous refractory sample (sample 2) obtained using the spherical magnesia-based clinker according to the present invention was found to have an excellent porosity. Thereby, even when the spherical magnesia-based clinker of the present invention is molded at a high pressure, it can be confirmed that the crushing can be advantageously avoided.

-Experimental Example 3-
Castable 2 was prepared by blending and kneading the spherical MgO clinker obtained in Experimental Example 2 and each component shown in Table 3 below in the proportions shown therein. On the other hand, castable 1 was prepared in the same manner as castable 2, using a commercially available MgO clinker and each component shown in Table 3 below. For the two types of castables obtained, the amounts of added water were standardized and kneaded with a universal mixer, and then each flow value was measured using a flow tester having a flow table, a flow cone and a stick.

  The flow value is a value measured and calculated as follows. That is: 1) Pack the castable into a flow cone that is correctly placed in the center on a flow table that is well wiped with a dry cloth. In this operation, the tip of the stab is struck 15 times over the entire surface so that the tip of the stab stick reaches about half the depth of the castable layer, and finally the deficiency is compensated to smooth the surface. 2) Immediately after filling the castable, remove the flow cone upward, give the castable layer 15 drop motions in 15 seconds, and measure the maximum diameter of the castable and the diameter perpendicular to it. And the value which expressed the average value with the integer which has mm as a unit is made into a flow value. In addition, about 300 or more, it displays as 300 or more. The results are also shown in Table 3 below.

  As is clear from the results in Table 3, it was confirmed that the castable 2 using the spherical magnesia-based clinker according to the present invention exhibits excellent fluidity.

-Experimental example 4-
Using light-burned magnesia as the MgO source material, stabilized zirconia as the ZrO ₂ source material, rutile titania as the TiO ₂ source material, and calcined alumina as the Al ₂ O ₃ source material, Four types of raw material compositions having the blending compositions listed in Table 4 below were prepared, and lignin as a binder was added to each raw material composition together with water and kneaded. A spherical granulated product was produced using And 4 types of spherical pulverized products were fired at 1900 ° C. for 10 minutes in a rotary furnace to obtain 4 types of clinker.

  The obtained clinker and each component shown in Table 5 below were blended and kneaded in the proportions shown therein, and after kneading, the obtained kneaded material was put into a predetermined mold and cured, and then 110 ° C. Were dried for 12 hours to obtain amorphous refractory samples (samples 3 to 6). About the obtained samples 3-6, the slag infiltration resistance was evaluated.

In addition, slag infiltration resistance was evaluated from the amount of erosion and penetration measured in the rotary erosion test. Specifically, slag having a composition consisting of CaO: 60 parts by weight, SiO ₂ : 20 parts by weight, Fe: 20 parts by weight, Al ₂ O ₃ : 5 parts by weight, and MgO: 5 parts by weight is used as the erodible material. 1) Place the erosion material on the sample, 2) Rotate the sample on which the erosion material is placed at 1650 ° C. for 30 minutes, and 3) once the erosion material is discarded after the rotation. Was repeated for 8 cycles, and the amount of erosion loss (mm) of the sample and the amount of penetration of the erosion material (mm) were measured. About the amount of erosion and the amount of permeation obtained in this way, the amount of erosion and the amount of permeation of the sample 3 to be compared was set as 100, and the erosion index and the permeation index of each sample (samples 4 to 6) were calculated. The results are also shown in Table 4 below.

  As apparent from the results of Table 4, it was confirmed that the refractory (samples 4 to 6) using the spherical magnesia-based clinker according to the present invention exhibits excellent slag infiltration resistance. .

-Experimental example 5
Diameter obtained by using light-fired magnesia: Spherical granule having a diameter of about 1 mm, ZrO ₂ source material in powder form (stabilized zirconia), or Al ₂ O ₃ source material in powder form (calcined) Alumina) is used to stir a spherical granulated product and a predetermined amount of powdery raw material in a mixer to obtain four types of coated granulated product having a coating layer having a thickness listed in Table 6 below. It was. After drying the spherical granulated product and the four types of the coated granulated product obtained, by baking at 1900 ° C. for 10 minutes using a rotary furnace, five types of clinker (clinker 5 to 9) are obtained. Obtained.

  Digestion resistance was evaluated using particles obtained by sieving the obtained clinker to 3.35 to 1.00 mm. Specifically, Gakushin Method 7 [Dolomite Clinker Digestibility Test Method] (Japan Society for the Promotion of Science 124th Committee, except that the treatment was performed at a pressure of 3 atm and a temperature of 132.9 ° C. for 2 hours. The weight increase rate (%) was measured according to [(II) Method by Autoclave] in the Analysis Subcommittee). In addition, it means that the digestion resistance of a clinker is excellent, so that the numerical value of this weight increase rate is small. The results are also shown in Table 6 below. In addition, the compressive strength of each clinker was measured in the same manner as in Experimental Example 1, and the results are also shown in Table 6 below.

  As apparent from the results in Table 6, the spherical magnesia clinker (clinker 6-9) according to the present invention exhibits excellent digestion resistance and has excellent strength. Admitted.

-Experimental Example 6
A spherical magnesia clinker having a particle size of 5 mm to 1 mm is formed by using a powdered Al ₂ O ₃ source material (calcined alumina) to form a 0.3 mm coating layer. By firing at 1900 ° C. for 10 minutes, a spherical magnesia clinker (with a coating layer) according to the present invention was obtained. The obtained clinker and each component shown in Table 7 below were blended in the proportions shown therein and kneaded in a universal mixer to obtain a castable. The castable was cast into a mold of length: 160 mm × width: 40 mm × thickness: 40 mm, cured there for 12 hours, and then deframed to obtain an amorphous refractory sample (sample 8). Similarly, an amorphous refractory sample (Sample 7) was obtained using a spherical magnesia clinker having a particle size of 5 mm to 1 mm without a coating layer. Each sample obtained was digested by holding it in an autoclave (132.9 ° C., 3 atm) for 3 hours, and the presence or absence of cracks in the sample after holding was visually observed. The length in the length direction was measured with a caliper, and the residual line change rate (%) was calculated. The results are also shown in Table 7 below.

As is clear from the results of Table 7, in the amorphous refractory (sample 8) obtained using the spherical magnesia-based clinker according to the present invention, the linear change rate after the digestion test is small, No cracks were observed and it was confirmed that the digestion resistance was excellent.

Claims (5)

Using a raw material composition capable of providing a chemical composition of MgO: 90 to 99% by weight and ZrO ₂ : 1 to 10% by weight, a spherical granulated product is produced, and the obtained product is fired. A spherical magnesia-based clinker characterized by comprising a product. MgO: from 85 to 98.5 wt%, ZrO _2: 1 to 10 wt%, and TiO _2: 0.5 to 5 with weight percent comprising the material composition capable of giving the chemical composition, producing granules spherical And a spherical magnesia clinker comprising a fired product obtained by firing such a granulated product. MgO: 75 to 97.5 wt%, ZrO _2: 1 to 10 wt%, TiO _2: 0.5 to 5 wt%, _{and, Al 2 O 3, Fe 2} O 3, NiO, of ZrSiO ₄ and MnO A raw material composition capable of giving a chemical composition of at least one or more of 1 to 10% by weight is manufactured using a fired product obtained by producing a spherical granulated product and firing the granulated product. Spherical magnesia clinker. On the surface of the spherical granule obtained using the MgO source material, a ZrO ₂ source material, a TiO ₂ source material, an Al ₂ O ₃ source material, an Fe ₂ O ₃ source material, a NiO source material, an MnO source material and A spherical magnesia comprising a fired product obtained by firing a coated granulated material having a coated layer formed with a coating layer containing at least one of SiO ₂ source materials. System clinker. A refractory using the clinker according to any one of claims 1 to 4.