JPH0388878A - Graphite granulated product for amorphous refractory - Google Patents

Abstract

PURPOSE:To provide the subject granulated product preventing the deterioration of work environments and the lowering of work efficiency due to the scattering of graphite dust and improving the heat resistance, corrosion resistance, etc., of molded products by coating the graphite granules of a specific state with a pitch. CONSTITUTION:Graphite granules such as flaky graphite or kish graphite in a mutually separated state or in a state wherein the plural granules of the graphite are aggregated are heated, mixed with 10-60wt.% of a pitch such as coal tar having a softening point of >=80 deg.C, cooled and subsequently crushed to provide the objective granulated product. When the granulated product having strong water repellency is required, the graphite granules are preferably pre- coated with a surfactant comprising the condensed product of an alkylnaphthalene sulfonic acid with formaldehyde.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to graphite granules added for the purpose of improving the thermal stability and corrosion resistance of monolithic refractories.

[Prior Art] Monolithic refractory materials have become an important item of refractory materials today. A typical monolithic refractory material is a mixture of alumina cement and aggregate, which is mixed with clean water to an appropriate degree of softness and then poured into a furnace using the pouring method. It is used.

[Problem to be solved by the invention] By the way, carbon materials such as coal tar pitch and graphite are added to the above-mentioned monolithic refractory materials in a proportion of several percent for the purpose of improving thermal stability and corrosion resistance. There is. When adding carbon material, it is common to knead ground pitch or graphite into the refractory material as is. However, this method has the following serious drawbacks.

(1) Pulverized carbon material, especially graphite which is a fine particle, tends to cause dust scattering, which worsens the working environment and reduces working efficiency.

(2) Graphite has strong water repellency, and in order to mix it uniformly with other materials, the amount of water added must be significantly increased.Also, there is a phenomenon in which graphite encloses air and bubbles, which not only has poor workability. , these increase porosity and contribute to a decrease in strength.

(3) In addition, if the amount of water added is large, the drying time after construction will be longer, making it more likely that cracks will occur, and in the worst case scenario, it may be used in a state that is not completely dry, resulting in high-temperature molten metal etc. There is a risk that the moisture will rapidly evaporate when it comes into contact with the water, which could lead to an explosion.

(4) In order for the monolithic refractory material to exhibit sufficient heat resistance and corrosion resistance, it is essential that each component adheres uniformly and is strongly integrated under the usage conditions. However, graphite is not compatible with the refractory material used as aggregate, and although the pitch melts and acts as an adhesive, it is difficult to obtain the desired results due to uneven distribution of each component.

An object of the present invention is to provide graphite granules that can mix carbon materials with a relatively small amount of water without deteriorating the working environment, and that can blend well with aggregate and exhibit the intended function. It is in.

[Means for Solving the Problems] The graphite granules of the present invention that achieve the above objects are characterized in that they are coated with pitch in a state where graphite particles are singly or in a plurality of aggregates. It is something. It is also effective to add a wood-philic and low-foaming surfactant to the granules, and this makes the effects of the present invention even more remarkable.

The graphite used in the present invention is not particularly limited, but includes, for example, scaly graphite, globular graphite, one-pack graphite, quiche graphite generated from the steel manufacturing process, and purified products thereof.

The pitch used in the present invention includes various pitches such as coal tar pitch, asphalt, and petroleum pitch, but it is preferable that the softening point is 80°C or higher,
More preferably, the temperature is 100°C or higher. If the softening point of the pitch is less than 80° C., it may become sticky during operation at room temperature, resulting in non-uniform kneading.

By the way, the method for producing the graphite granules of the present invention is as follows:
Add crushed pitch to powdered graphite and mix it, heat it above the softening point of the pitch, then granulate and cool it as is, or
There are methods such as cooling the heated material and then pulverizing it. The pitch ratio at this time is preferably about 10 to 60% by weight,
More preferably, it is about 20 to 40 Ii% by weight. That is, if the pitch ratio is less than 10% by weight, the coating effect of graphite will be insufficient, so that the object of the present invention will not be fully achieved, while if the pitch ratio exceeds 60% by weight, the amount of graphite will be relatively reduced. As a result, the corrosion resistance of the refractory material becomes insufficient.

Regarding the surfactants that can be used in the present invention,
Any material may be used as long as it is hydrophilic and has low foaming properties, and examples thereof include, but are not limited to, a condensate of alkylnaphthalene sulfonic acid and formaldehyde as disclosed in JP-A No. 63-47892. Addition of polyhydric alcohols, such as glycols, is effective in increasing antifoaming properties.

[Function] Since graphite has the most thermally and chemically stable structure among carbon materials, it is extremely useful for protecting refractory materials from erosion by high-temperature molten slag. However, it is necessary to firmly adhere and integrate it with the surface of the refractory material.

Pitch melts in the amorphous refractory material due to high heat during use, penetrates and adheres between the aggregates, acts as an adhesive between graphite and aggregates, and carbonizes at high temperatures, and these carbon materials Chemically reacts with other components to form carbide, forming a strong heat-resistant bond.

The carbon material fixed on the refractory material prevents corrosion by impairing the wettability with high-temperature molten slag and iron, while the partially gasified carbon material reacts with the oxygen present in the surrounding area and dissolves the iron. It also has the effect of preventing oxidation.

However, if graphite and pitches are added as separate particles, it is often difficult for this interaction to proceed in the expected manner due to the uneven distribution of each component or insufficient contact. By adding it, protection and reinforcement of the aggregate can be ideally achieved.

The fact that graphite coated with the pitches of the present invention scatters less dust than fine graphite powder is a natural result of its structure, particle shape, bulk density, etc.

The reason why there is almost no need to increase the amount of water for mixing monolithic refractories is the effect of coating the extremely water-repellent graphite surface with pitch, which has relatively low water repellency. Further improvements can be made by adding activators.

[Example] The present invention will be explained in more detail with reference to Examples below. However, the following Examples are not intended to limit the present invention.
Any design changes for the purposes described below are included within the technical scope of the present invention.

Example 1 Natural scaly graphite with 100 mesh or less and purity of 94%
A mixture of 3011 parts by weight and pulverized coal tar pitch with a softening point of 125°C was heated at 160 to 220°C.
After mixing with heating and cooling, particle size C of 1 mm or less
The graphite granules of the present invention were obtained by pulverization.

Al master 90m! To 5 parts by weight of alumina cement, 5 parts by weight of the above-mentioned graphite granules treated with sodium dinaphthyl methanesulfonate and 5 parts by weight of water were mixed, and vibration molding was performed. It was possible to obtain a strong molded body in which no uneven distribution or lifting of (graphite granules) was observed. Further, the above molded body was fired at 1200° C. for 2 hours, and the fired product was strong and showed no cracks at all.

Example 2 A mixture of 6511 parts by weight of quiche graphite with 100 mesh or less and a C concentration of 90% and 235 parts by weight of crushed coal tar pitch with a softening point of 145°C was mixed with about 25 parts by weight of
The mixture was mixed while heating at 0° C., cooled and then crushed to obtain the graphite granules of the present invention.

The above graphite granules were treated with sodium dinaphthyl methanesulfonate to 90 parts by weight of aluminum and 5 parts by weight of alumina cement. 5! When i parts and 5 parts by weight of water were added, kneaded, and vibration molded, it was possible to obtain a strong molded product in which no uneven distribution or lifting of the carbon material (graphite granules) was observed. Further, the above molded body was fired at 1300° C. for 2 hours, and the fired product was strong and showed no cracks.

Comparative Example 5 parts by weight of natural scaly graphite with a purity of 94% or less, 100 mesh or less, 5 parts by weight of Alyosu 901i, and 5 parts by weight of Alyona cement were mixed, water was added, and the mixture was thoroughly kneaded, but a good molded body was obtained. required 8 parts by weight of water based on the above mixture. In addition, the above molded body was fired at 1200°C for 2 hours, but
The fired product was more brittle than that obtained in Example 1.2, and some cracks were observed.

[Effects of the Invention] As described above, according to the present invention, since graphite is coated with pitch, the heat resistance and corrosion resistance of the refractory can be significantly improved.

In addition, deterioration of the working environment due to dust scattering is prevented, crosstalk can be achieved with a relatively small amount of water, preventing a decrease in the strength of the molded product due to increased porosity, and no longer drying time, reducing operational efficiency. It could be prevented.

Heisei October 26, 1 year 1999 Patent Application No. 226548 2. Name of the invention Graphite granules for monolithic refractory materials 3. Person who makes corrections connection to the incident

Claims (2)

[Claims] (1) Graphite granules for monolithic refractories, characterized in that they are made by coating graphite particles singly or in a plurality of aggregates with pitch. (2) The graphite granule for an amorphous refractory material according to claim (1), which contains a hydrophilic and low-foaming surfactant.