JPH0892619A - Refractory ball for cokeless cupola - Google Patents

Abstract

PURPOSE: To provide a refractory ball for a cokeless cupola which has a carbonizing effect and is hardly consumed even in the heating zone of the cupola. CONSTITUTION: This refractory ball has a nucleus part 2 formed of a non- carbonaceous refractory material and is formed with a graphite layer 3 on its outer periphery. A coating layer 4 formed of the refractory material described above is formed on the outer periphery of this graphite layer 3. This coating layer 4 is preferably formed at the layer thickness at which the layer is removed by rubbing and friction at the time of passing the preheating zone of the cupola.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory ball used for cokeless cupola (natural gas cupola).

[0002]

2. Description of the Related Art Conventionally, when operating a cupola, coke is deposited in the furnace at a certain height from the bottom of the furnace, and metal and coke are alternately charged on the coke, and air is sent from the tuyere. Burn coke. The heat generated by the combustion of coke gradually melts the metal from the bottom.

However, in a cupola using such coke as fuel, a large amount of sulfur is absorbed in the molten metal. There is also a problem that the sulfur in the combustion gas pollutes the atmosphere. Therefore, in recent years, cokeless cupola has come into use. During the operation of the cokeless cupola, refractory balls are deposited on a grate provided at the bottom of the furnace, and then the charging raw material and the refractory balls are alternately charged. A tuyere is provided below the grate, and combustion gas such as natural gas or city gas is injected from a burner attached to the tuyere to melt the raw material on the refractory ball.
In the cupola, a heating zone, a melting zone, and a pretropical zone are formed upward from the grate, and the heating zone is composed of only refractory balls.

As the refractory ball, Japanese Patent Laid-Open No. 4-74 is known.
As disclosed in Japanese Laid-Open Patent Publication No. 815, there is a spherical material formed by adding an inorganic binder to a refractory material such as ceramics or graphite and kneading the mixture.

[0005]

When a large amount of steel scrap is mixed as a charging raw material, it is necessary to carry out carburization. In this case, as the refractory ball, one having graphite as a main component may be used. However, using such a refractory ball, when the refractory ball passes through the cupola's pretropical zone,
Thermal decomposition occurs. Further, since the refractory balls are exposed to high temperatures in the heating zone, thermal decomposition is accelerated and wear is severe. Therefore, there is a problem that the yield of the graphite refractory balls is low.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a refractory ball for cokeless cupola which has a carburizing effect and is less likely to be consumed in the cupola heating zone.

[0007]

DISCLOSURE OF THE INVENTION The present invention is a refractory ball to be introduced into a cokeless cupola, which has a core portion formed of a non-carbonaceous refractory material and has a graphite layer formed on the outer periphery thereof. A coating layer made of the refractory material is formed around the graphite layer. The coating layer is preferably formed to have a layer thickness which is removed by rubbing and abrasion when passing through the cupola pretropical zone.

[0008]

When the refractory balls introduced from the inlet of the cupola descend in the pretropical zone, the outermost coating layer prevents the graphite layer from being consumed by oxidation due to thermal decomposition. By forming the coating layer to an appropriate thickness, the balls or the balls and the charging raw material rub against each other, the coating layer gradually peels off, and is removed by the time it reaches the melting zone, exposing the graphite layer. Come to do.

In the melting zone or the upper part of the heating zone, the charging raw material melts down and flows down along the surface of the graphite layer of the refractory ball. At this time, it is carburized. Further, a part of the graphite layer is oxidized and generates heat. By the time the refractory balls reach the upper or middle part of the heating zone, the graphite layer disappears, leaving only the core and depositing on the grate. A ball consisting of only a core portion deposited on the grate is hard to wear even when exposed to high temperature.

[0010]

1 shows a cross-sectional view of a refractory ball 1 according to the present invention, in which a graphite layer 3 is formed around a spherical core portion 2 forming a central portion, and a coating layer 4 is formed on the outer periphery thereof. It is formed by stacking. The core portion 2 and the coating layer 4 are formed by spherically molding a mixture of a refractory material other than graphite, for example, a powder of SiO ₂ , ZrO ₂ , Al ₂ O ₃ or the like and an inorganic binder such as water glass or cement. . On the other hand, the graphite layer 3 is formed by mixing graphite and an inorganic binder, and the compounding amount of graphite is usually 90 wt% or more, preferably 95 wt% or more. The size of each part is a cupola for 65 tons, the outer diameter φ is 150 to 200 mm, the thickness of the coating layer 4 is about 1 to 3 mm, and the thickness of the graphite layer 3 is about 10 to 30 mm.

FIG. 2 shows a state of use of the refractory ball of the present invention. A fire grate 12 is provided on the furnace bottom of the cupola body 11, and refractory balls 1C and 1B are deposited thereon.
Further, the charging raw material 21 and the refractory balls 1A are alternately charged thereon. A tuyere 13 is provided below the grate 12, and a burner 14 is attached to the tuyere 13 to inject combustion gas such as natural gas or city gas. Reference numeral 15 is a tap hole, and 16 is a slag discharge port. A is a pre-tropical zone, B is a melting zone, C is a heating zone, and the lower part of the melting zone B or the heating zone C
The graphite layer 3 is exposed in the refractory ball 1B on the upper part of the. On the other hand, the ball 1C existing from the center to the lower part of the heating zone C
Is only the core 2 without the graphite layer 3.

[0012]

As described above, according to the refractory ball of the present invention, the refractory ball has a core portion formed of a non-carbonaceous refractory material,
A graphite layer is formed on the outer periphery of the graphite layer, and a coating layer formed of the refractory material is formed on the outer periphery of the graphite layer. While being prevented, the graphite layer exposed at the upper part of the melting zone or the heating zone exerts an effective carburizing action. Further, since the core is formed inside the graphite layer, it is hard to be consumed even when exposed to high temperature in the heating zone, and the yield is high.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a refractory ball according to the present invention.

FIG. 2 is a schematic cross-sectional view of a main part of a cupola showing an operating state.

[Explanation of symbols]

 1, 1A, 1B, 1C Refractory ball 2 Core part 3 Graphite layer 4 Covering layer

Claims (2)

[Claims] 1. A refractory ball to be introduced into a cokeless cupola, which has a core portion formed of a non-carbonaceous refractory material, a graphite layer is formed on the outer periphery thereof, and the graphite layer is formed on the outer periphery of the graphite layer. A refractory ball for cokeless cupola having a coating layer formed of a refractory material. 2. The refractory ball for a cokeless cupola according to claim 1, wherein the coating layer is formed to have a layer thickness which is removed by rubbing and abrasion when descending in the pretropical zone.