JP2001058891A - Corrosion-resistant high-strength refractory, its production and lifter for kiln comprising the refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide lifters capable of obtaining a sufficiently stirring effect for many hours, to obtain a corrosion-resistant high-strength refractory used for the lifters and to provide a method for producing the refractory. SOLUTION: This method for producing a corrosion-resistant high-strength refractory comprises baking a refractory composed of Al2O3 as a main component and containing >=3% and <=20% Cr2O3 by weight ratio in Cr2O3 powder at >=1,400 deg.C to form a corrosion-resistant layer having a high Cr2O3 concentration on the surface. This corrosion-resistant high-strength refractory having a high Cr2O3 concentration on the surface is produced by the method. The lifters are installed on a furnace wall refractory in the vicinity of an inlet part of a kiln and are constituted of the refractory.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory used for a kiln lifter for incinerating and melting industrial waste.

[0002]

2. Description of the Related Art Generally, refractories constituting a kiln for incinerating and melting industrial waste include Cr ₂ O ₃ having excellent corrosion resistance.
Al ₂ O ₃ -based refractories containing 3 to 20% are used. Cr ₂ O ₃ increases the corrosion resistance according to the added amount, but on the other hand, lowers the resistance to thermal shock. In particular, when the added amount of Cr ₂ O ₃ exceeds 20%, the decreasing tendency is remarkable.

[0003] When industrial waste is incinerated or melted, the composition of the waste is not constant, and it is 1300 to 1400 ° C.
If the object to be treated is not heated evenly, unburned matter increases and the treatment capacity decreases. Therefore, as shown in FIGS. 4 to 6, a protruding portion called an inwardly protruding lifter (23) is provided on the furnace wall refractory (22) near the entrance of the kiln (21), whereby To perform a uniform heat treatment.

[0004]

However, due to the provision of the lifter, the processed material accumulates at the root thereof,
For this reason, stress concentration occurs here, and destruction may occur in a shorter time than at the root. At this time, if the thickness of the lifter is smaller than the thickness of the furnace wall refractory, local melting of the object to be processed occurs, which is a serious problem. Therefore, a refractory which is superior in thermal shock resistance as compared with the furnace wall refractory and in which the amount of Cr ₂ O ₃ added is reduced as compared with the furnace wall refractory is often used for the lifter. However, in this case, since the erosion proceeds more easily than the furnace wall refractory, the lifter decreases in a short time and the stirring effect cannot be maintained for a long time.

It is an object of the present invention to solve these problems and to provide a lifter capable of obtaining a sufficient stirring effect for a long time, a corrosion-resistant high-strength refractory used for the lifter, and a method for producing the same.

[0006]

SUMMARY OF THE INVENTION The first aspect of the present invention is to provide Al ₂
O ₃ as a main component, Cr ₂ O ₃ at 3% by weight
By baking a refractory containing at least 20% or less in a Cr ₂ O ₃ powder at 1400 ° C. or more, a high Cr
_A method for producing a corrosion-resistant high-strength refractory, comprising forming a corrosion-resistant layer having a concentration of ₂ O ₃ .

[0007] A second aspect of the present invention is that the above method is used.
It is a corrosion-resistant high-strength refractory characterized by having a corrosion-resistant layer with a high Cr ₂ O ₃ concentration on the surface.

A third aspect of the present invention is a lifter provided on a furnace wall refractory near the kiln inlet and composed of the refractory.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

A required amount of Al ₂ O ₃ having an average particle diameter of 50 μm, a required amount of Cr ₂ O ₃ , a required amount of 100 parts by weight of the total, 3 parts by weight of polyvinyl alcohol as a binder and a required amount of water are mixed. The material was pulverized with a ball mill for 24 hours. Then, the pulverized product is dried by a dryer for 1 hour.
Dry at 20 ° C. for 24 hours. The powder thus obtained is
After press-molding into a prismatic shape at a pressure of 00 kg / cm ² , sintering was performed at 1600 ° C. for 2 hours in the air to obtain a prismatic sintered product of 80 × 50 × 150 mm. This sintered product was embedded in a Cr ₂ O ₃ powder having a particle size shown in Table 1,
It was heated at the temperature shown in Table 1 for the time shown in Table 1. Thus,
No. 5 to 17 test pieces were obtained.

In Table 1, No. Test specimens Nos. 1 to 4 were obtained by sintering the sintered product in Cr ₂ O ₃ powder at 1400 ° C. or higher.

Performance Evaluation a) Corrosion resistance test (erosion rate) Using this test piece, the corrosion resistance was examined by measuring the erosion rate using a rotary erosion test apparatus shown in FIG. In FIG. 1, (1) is a tester main body, (2) is a test piece contained therein, (8) is a slag, (3) is a burner for heating the test piece, (4) and (5) are burners. A flow meter is provided with a propane conduit and an oxygen conduit, respectively, connected to

The test method is as follows.

I) Propane / oxygen (1 /
6) Supply the mixed gas and heat the surface of the test piece (2) in the tester (1) at 1500 ° C for 6 hours.

Ii) A slag (8) is put on the test piece (2).

Iii) Rotate while maintaining the temperature at 1500 ° C. for 20 minutes.

Iv) The slag (8) is discharged and new slag is charged.

V) The above operations iii) and iv) are repeated 18 times (total heating for 6 hours).

Vi) The temperature is measured when the slag is melted.

Vii) Observe the cross section of the test piece after the test and calculate the erosion rate from the change in thickness.

The slag used was Na₂ O: 7
%, Al₂ O₃ : 8%, SiO ₂ : 33.5%,
CaO: 33.5%, Fe₂ O₃ : 18% basicity
It has a composition of 1.0.

B) Thermal shock resistance test As shown in FIG. 2, the thermal shock resistance was evaluated by heating one side of a test piece (6) in an electric furnace (7) at 1000 ° C., holding for 30 minutes, and cooling with water. The operation was repeated and the number of times of peeling from the test piece was measured.

Table 1 shows the results of these tests.

According to the test results, the sintered product was made of Cr ₂ O ₃
The temperature for embedding and heating in the powder is preferably 140
0 ° C. or higher (Comparison of No. 5 with Nos. 8 and 9). Regarding the particle size of the Cr ₂ O ₃ powder used for embedding, a powder having a particle size of 50 to 1000 μm was used in this test, but the characteristics were not affected at all by the change in the particle size (Nos. 10 to 13). Further, the holding time is also 0.
If it is 5 hours or longer, the characteristics will not be affected even if the length is increased.

From the above test results, it is possible to obtain a corrosion-resistant high-strength refractory with improved corrosion resistance while maintaining thermal shock resistance by using the present invention. By applying this to a kiln lifter, the durability can be improved. It can be seen that it is possible to achieve an improvement.

[0026]

[Table 1] No. 1 in Table 1. Using a refractory consisting of 8
A lifter was provided on a furnace wall refractory near the kiln inlet of a rotary kiln having an inner diameter of 4 m and a length of 10 m, and its durability was examined.
A brick containing 10% of Cr ₂ O ₃ was used as a furnace wall refractory.

For comparison, a refractory for a lifter was used.
As Cr₂ O₃ 3% (No. 1) and 1
Two types of bricks containing 0% (No. 2) were used. They are,
Cr ₂ O₃ Fired at 1400 ° C or higher in powder
is not. Furnace temperature 1300 ° C, 3 revolutions / hour
The waste having a basicity of 0.7 was treated three times for each 1 ton.
After the operation was completed, the furnace was gradually cooled and the furnace was inspected.₂ O
₃ Bricks with a content of 3% suffer significant erosion and have a high Cr content.
₂ O₃ Cracks occur on bricks with a content of 10%
Was. In contrast, the product of the present invention was completely sound.

No. 1 in Table 1 A prismatic refractory specimen consisting of 10 components (80 × 50 × 150 mm)
About the distance in the vertical direction (80 mm in height) and Cr ₂
The relationship with the O ₃ concentration was examined by X-ray fluorescence. This result is shown in FIG.
Shown in According to this, it can be seen that the Cr ₂ O ₃ concentration is high at the surface of the test piece and decreases toward the inside. That is, the surface portion of the test piece has a high Cr ₂ O ₃ concentration and is excellent in corrosion resistance, and the inside has a low Cr ₂ O ₃ concentration and is excellent in thermal shock resistance.

[0029]

As described above, according to the present invention, it is possible to easily impart corrosion resistance to a low Cr ₂ O ₃ material having good thermal shock resistance. This will break the kiln lifter,
The occurrence of melting damage can be suppressed, and a good stirring effect can be maintained for a long time.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a rotary erosion test method.

FIG. 2 is a schematic view showing a thermal shock resistance test method.

FIG. 3 is a graph showing a relationship between a vertical distance of a test piece and a Cr ₂ O ₃ concentration.

FIG. 4 is a longitudinal sectional view showing a lifter installation state near an entrance of a kiln.

FIG. 5 is a sectional view taken along line VV in FIG. 4;

FIG. 6 is a sectional view taken along the line VI-VI in FIG.

[Explanation of symbols]

 1: Tester body 2: Test piece 3: Burner 4: Propane pipe 5: Oxygen pipe 6: Test piece 7: Electric furnace 21: Kiln 22: Furnace wall refractory 23: Lifter

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F27B 7/28 C04B 35/10 F F27D 1/00 35/64 B F-term (Reference) 3K065 AA07 AC20 BA08 BA09 FA12 FB13 4G030 AA22 AA36 BA25 BA33 GA27 4K051 AA03 AB03 BE03 4K061 AA02 BA12

Claims (3)

[Claims] [Claim 1] as a main component Al ₂ O _3, Cr ₂
A refractory containing 3% to 20% by weight of O ₃ is fired in a Cr ₂ O ₃ powder at 1400 ° C. or more to form a corrosion resistant layer with a high Cr ₂ O ₃ concentration on the surface. Method for producing high-strength corrosion-resistant refractories. 2. A high-corrosion-resistant refractory comprising a corrosion-resistant layer having a high Cr ₂ O ₃ concentration on the surface, produced by the method according to claim 1. 3. A lifter provided on a furnace wall refractory near a kiln inlet and comprising the refractory according to claim 2.