JPH0519772A - Ceramic sound absorbing material - Google Patents

Abstract

PURPOSE:To obtain the sound absorbing plate to be used for a sound absorbing and gas discharging column for discharging high-temp. exhaust gases, such as high-temp. steam in particular or the like. CONSTITUTION:This ceramic sound absorbing plate is produced by mixing refractory ceramic particles having 0.5 to 3mm grain sizes and low melting glassy particles having the m. p. lower than the m. p. of the ceramic particles and pressing the mixture, then calcining the molding. The material of the above- mentioned refractory ceramic particles consists essentially of lithium aluminum silicate and/or cordierite.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic sound absorbing plate, and more particularly, to a sound absorbing plate used in a sound absorbing exhaust tower for discharging high temperature exhaust gas such as high temperature steam.

[0002]

2. Description of the Related Art Conventionally, fibrous sound absorbers such as glass wool are widely used in exhaust towers that exhaust high-temperature exhaust gas such as steam exhausted from various factories in order to muffle or absorb noise from exhaust pipes. Has been done. However, once the fibrous sound absorber absorbs water due to water vapor or rainfall, it becomes difficult to completely remove the water, and the sound absorption is remarkably lowered by the water absorption.

[0003]

In order to make up for this drawback, a so-called ceramic has recently been used in place of a fibrous sound absorber, in which particles such as silica sand, mullite, or ceramic tile are crushed and bonded with a heat-resistant binder such as glaze. Sound absorbers have come into use. Since these sound absorbers can remove water very easily and quickly even if they absorb water, there is no significant decrease in the sound absorption coefficient, and the demand for steam absorbers is growing mainly.

In this connection, the present inventors also filed Japanese Patent Application No. 61
The improved sound absorbing plate has been proposed in -200053 and 62-251575. On the other hand, based on these achievements, the demand for ceramic sound absorbing plates has come to be demanded for noises such as gas turbines and higher temperatures. For example, for the purpose of absorbing sound at the gas turbine safety valve outlet, it is subjected to severe thermal shock by high-temperature gas of 800 ° C or higher. In this case, the conventional mullite (3Al ₂
In the case of using O ₃ · 2SiO ₂ ) -based ceramic particles as an aggregate, there is a drawback that the ceramic particles cannot withstand the thermal shock and are damaged.

The present invention is intended to provide a ceramics sound absorber that solves the drawbacks of the conventional ceramics sound absorber.

[0006]

The present invention has a particle size of 0.5 to 0.5.
3mm refractory ceramic particles and melting point than ceramic particles
Low melting point glassy particles are mixed, pressed and fired
In the finished product, the material of the refractory ceramic particles is
Aluminum silicate (Li₂O-Al ₂O₃−
SiO₂) And / or cordierite (2MgO.2A)
l₂O₃・ 5 SiO₂) Is the main component
It is a ceramic sound absorbing board.

[0007]

The present invention has excellent thermal shock resistance as compared with the conventional ceramic sound absorber. Its action is mainly based on the materials of the refractory ceramic particles such as lithium / aluminum / silicate Li ₂ O—Al ₂ O ₃ —SiO ₂ (hereinafter abbreviated as LAS) and cordierite 2MgO · 2Al ₂ O _3.
It can be obtained by using 5SiO ₂ (hereinafter abbreviated as MAS). Thermal shock resistance R against sudden temperature changes
Is expressed by the following equation. R = σ _C / Ε · α where σ _{C is} strength, E is Young's modulus, and α is coefficient of thermal expansion. That is, the higher the strength, the smaller the Young's modulus and the coefficient of thermal expansion, the more excellent the thermal shock resistance.

LAS and MAS are characterized by a small coefficient of thermal expansion. In other words, LAS is 1 × 10 ⁻⁶ / ° C. and MAS is 2 × 10 ⁻⁶ , compared to 5 × 10 ⁻⁶ / ° C. of mullite, which is the main component of conventional ceramics sound ^absorbers.
It is as small as / ° C and has a great effect on improving thermal shock resistance. By this action, it becomes possible to manufacture a ceramic sound absorber having excellent thermal shock resistance at high temperatures.

Further, in the present invention, the refractory ceramic particles are limited to those which are sieved in the range of 0.5 to 3 mm.
The shape of the particles is obtained by adding water to a kaolin-based matrix prepared to have a composition of LAS or MAS, kneading it into a clay-like material to form pellets by extrusion molding, and then spheroidizing the pellets by a tumbling granulation method or the like, Alternatively, there are those prepared by melting and crushing the above compounding base at a high temperature, crushing failed honeycomb-shaped products, etc., and the manufacturing method is not particularly limited.

The reason why the particle size of the aggregate particles is limited to the range of 0.5 to 3 mm is determined from the sound absorption characteristics and the flow resistance test results. On the contrary, if it is less than 0.5 mm, the flow resistance is too large, so that the air permeability is poor and the performance as a sound absorbing plate is not achieved.

The low-melting glass particles bond the aggregate particles, and when heated to a temperature above the melting point of the low-melting glass, flow between the aggregate particles, and when cooled, the aggregate particles are firmly bonded. To do.

In the present invention, water glass may be blended in order to maintain a desired shape at room temperature. The mixing ratio of refractory ceramic particles (LAS, MAS), low melting point glass and water glass is refractory ceramic particles: Low melting glass:
The ratio of water glass = 100: 10: 5 is preferable.

[0013]

EXAMPLES Examples of the present invention will be described below. Table 1 shows the characteristics of the sound absorbing panel prepared by the example of the present invention and the test method carried out for comparison.

Aggregates used were LAS aggregates and MAS aggregates, which were prepared by crushing and sieving honeycomb fired bodies whose main components were LAS and MAS, respectively.

Low melting glassy particles used as heat resistant binder
The child is SiO₂77.8%, Al₂O ₃13.2%, Mg
O 3.3%, K₂O 5.1%, melting point 130
It is 0 ° C. Water glass No. 4 was used.

The trial manufacture of the panel was carried out by adding low melting glass particles and water glass to the aggregate particles and kneading the mixture to obtain 300 × 300 mm.
A sound absorbing plate was obtained by press-molding into a plate shape using the above mold and sintering the molded product. The general characteristics of the obtained sound absorbing plate were evaluated by bending test, porosity, flow resistance and sound absorbing performance.

Further, the thermal shock resistance is measured by bending test pieces (10 mouths ×
(100 liters) was heated and then dropped in water to be subjected to thermal shock, and then a bending test was performed at room temperature for evaluation.

Table 1 shows the general characteristics of the sound absorbing plate. The sound absorption peak value which is the basic characteristic of the sound absorbing plate is 500 Hz, α
_{When 0} = 0.9 or more, the particle size is classified to 0.5 to 3 mm, and the flow resistance is maintained at 30,000 ± 10,000 MKSr / m,
I was able to achieve it.

Among the products shown in Table 1, the conventional material of No. 2
The results of thermal shock test of the materials of the present invention No. 3 and No. 5 are shown in FIG. It is clear that mullite has a sharp decrease in strength, whereas the material of the present invention has a gradual decrease and has excellent thermal shock resistance.

[Table 1]

[0020]

As described above, the ceramic sound absorbing body of the present invention can be provided with excellent thermal shock resistance which has never been obtained by using low thermal expansion LAS and / or MAS as aggregate particles. Is.

[Brief description of drawings]

FIG. 1 is a diagram showing a comparison of thermal shock test results of a sound absorbing material of an example of the present invention and a conventional sound absorbing material.

Claims (1)

[Claims] 1. A refractory ceramic grain having a grain size of 0.5 to 3 mm.
Low-melting glassy particles with a lower melting point than the child and ceramic particles
In the product that mixes the child, presses it, and fires it,
The material of the ceramic particles is lithium aluminum aluminum
Acid salt (Li₂O-Al₂O₃-SiO₂) And / or
-Jerlite (2MgO / 2Al₂O ₃・ 5 SiO₂)
A ceramic sound absorbing board characterized by having as a main component.