JP2007169092A - Method of recycling chromium-containing refractory - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of recycling chromium-containing refractory by which spent refractory is effectively used regardless of the content of chromium. <P>SOLUTION: In the method of recycling the chromium-containing refractory, the spent refractory containing chromia and the balance being at least one kind selected from a group consisting of alumina, magnesia, silica, zirconia, hafnia and lime is used as a raw material of artificial jewelry. The spent refractory is pulverized and heated/melted to manufacture the artificial jewelry. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for recycling a chromium-containing refractory using a refractory containing chromium as a raw material for artificial gemstones.

Conventionally, a large amount of incineration residue (ash) generated in the waste treatment process has been disposed of in landfills. However, the disposal site is becoming increasingly tight, and in recent years, ash has been melted to reduce the volume. Yes. Since melting of ash requires a high temperature of 1400 ° C. or higher and the composition of ash is not constant, a refractory containing chromia is used for the purpose of extending the life of the refractory constituting the melting chamber ( Patent Document 1).
Japanese Patent Laid-Open No. 11-189459

  By the way, although the refractory containing chromia is excellent in corrosion resistance, there is a risk of generating harmful hexavalent chromium. For this reason, in order to dispose of refractories that have been used for a certain period of time, strict management is required not only for used refractories generated by replacement after use, but also for refractory manufacturing, processing, and residual materials generated during construction. Is required. Moreover, since hexavalent chromium is water-soluble, it cannot be discharged as it is until it reaches the kneading container for the irregular shaped refractory, the cleaning water for the jig, and the cooling water obtained by cutting the refractory wet. Since these solid waste and liquid waste usually need to be disposed as industrial waste, and the cost required for disposal is high, an effective recycling method is required.

  Conventionally, several methods of using refractories containing chromia have been implemented. For example, this is reused as a refractory material for bricks or the like, or is subjected to processing such as pulverization, and is used for emergency repair as a spraying material.

  However, in such a recycling method, the used refractories are limited to those having a relatively high chromium content (about 30% by weight), and for other items, an effective recycling method cannot be found. It is discarded as waste.

  In view of the above problems, an object of the present invention is to provide a method for recycling a chromium-containing refractory that can be used effectively regardless of the chromium content of the used refractory.

The present invention includes chromia (Cr ₂ O ₃ ), with the balance being alumina (A1 ₂ O ₃ ), magnesia (MgO), silica (SiO ₂ ), zirconia (ZrO ₂ ), hafnia (HfO ₂ ) and lime (CaO). And a spent refractory material selected from the group consisting of) is used as a raw material for artificial gemstones.

  More specifically, the above-mentioned used refractory is pulverized, heated and melted to produce an artificial gemstone.

  The chromia content of the spent refractory pulverized product is preferably 0.1 to 0.5% by weight, or the spent refractory pulverized product is mixed with another metal oxide powder to form a chromia. The content is preferably adjusted to 0.1 to 0.5% by weight.

  The chromia content in the refractory is generally about 3 to about 30% by weight. A used refractory having a chromia content exceeding 30% by weight may be used. However, such a used refractory having a high chromia content can be reused as it is for a refractory application such as a raw material of a spray material. When using a refractory having a chromia content exceeding 3% by weight in the method of the present invention, after pulverization of the refractory, the obtained refractory powder is converted into alumina, magnesia, silica, zirconia, hafnia and lime. It mixes with the powder of another metal oxide, and the chromia content in the obtained mixture is preferably adjusted to 0.1 to 0.5% by weight.

The balance is at least one selected from the group consisting of alumina, magnesia, silica, zirconia, hafnia and lime, but is composed of a metal oxide selected from the group consisting of alumina, magnesia, silica, zirconia, hafnia and lime. For example, mullite (3Al ₂ O ₃ · 2SiO ₂ ) may be used.

  The refractory may be a regular refractory represented by bricks or an irregular refractory such as castable, stamp ramming, or spraying material. A typical refractory is alumina-chromia. This forms a solid solution.

  Spent refractories are generated, for example, when ash melting furnaces, waste melting furnaces, cement firing kilns are actually operated and then dismantled for replacement, or when refractories are manufactured, processed, and enforced. Remaining material, processing waste, etc., for example, residue obtained by filtering the washing water of the kneading vessel and cooling water generated by wet processing, and further processing waste generated when processing in a dry process Also good.

  Chromium contained in the refractory material may be trivalent chromium or hexavalent chromium, and is finally made harmless by melting at a high temperature. Chromium contained in the refractory serves as a coloring material in the artificial jewel and the main raw material in the chrome dolomite stone. In the artificial jewel, the above-mentioned remainder of the refractory constitutes different types of artificial jewels such as ruby and safiya.

  In the step of heating / melting the pulverized product of a used refractory or a mixture of the refractory and another metal oxide, the particle size of the pulverized product is appropriately determined so that it can be easily melted next. As for the heating temperature, trace amounts of sodium, potassium, calcium and iron contained in ash and cement used in ash melting furnaces and cement firing kilns serve to lower the temperature required for the production of artificial gemstones. Thus, the artificial jewel can be manufactured at a temperature lower by about 50 to 100 ° C. than the melting temperature 2000 to 3000 ° C. of an ordinary artificial jewel by the ash melting component contained in the refractory, which is economical.

  Artificial gems obtained by the method of the present invention are, for example, ruby, emerald, aquamarine, chromium-containing tourmaline, and chromium-magnesium tourmaline.

  When chromia is used as an aggregate component, it is possible to more efficiently recycle / detoxify chromium by separating only chromia. In the case of an alumina-chromia refractory, for example, 80% by weight of alumina-20% by weight of chromia inevitably causes most of the aggregate to be alumina, so that a certain degree of separation is possible. After that, the content is adjusted to a desired value while measuring the chromia content by a technique such as X-ray analysis.

  As can be seen from the examples described later, it is possible to reuse the refractory waste as a pigment source for artificial gemstones. Artificial gemstones have many uses because they have the same shine as naturally produced gemstones but are extremely inexpensive compared to natural products. For example, ruby can be used not only for jewelry purposes but also for machining tool materials by taking advantage of its high hardness, and tourmaline can also be applied as a piezoelectric material as the alias of tourmaline shows.

  Moreover, when obtaining ruby, emerald, etc., chromia can be used as a pigment source. In addition to chromia, alumina, silica, etc. are mixed in refractory waste, but these ingredients are also contained in trace amounts in natural gemstones, and the amount necessary for vivid color development is very small (0. Therefore, alumina, silica, etc. have no effect on the quality of the product.

  On the other hand, tourmaline can be used as a main raw material for chromium bituminous tourmaline having the following composition by adding chromium so as to have the following composition.

Chrome magnesia _{tourmaline: NaMg 3 Cr 5 Fe (BO} 3) 3 Si 6 O 18 (OH) 3 OH

  According to the present invention, a used chromium-containing refractory can be effectively used as a raw material for a product with high added value such as an artificial gem regardless of the chromium content.

  Next, in order to specifically explain the present invention, some examples of the present invention and comparative examples for showing comparison with the examples will be given.

Example 1
After operating the waste melting furnace for about one year, it was dismantled for replacement. The alumina-chromia refractory generated at that time is pulverized into granules having a particle size of about 200 μm or less, and the components are adjusted so that the chromia content is 0.1 to 0.5% by weight of the whole and the balance is alumina. did.

  Then, when this was heated and melted at 2500 ° C. and cooled, a lump exhibiting a bright red color was obtained.

As a result of powder X-ray diffraction, only a corundum single phase was detected. The specific gravity was 4 g / cm ³ , indicating that an artificial ruby was obtained.

Example 2
A commercially available raw material was blended so as to have a composition of beryl (3BeO · Al ₂ O ₃ · 6SiO ₂ ), and the blend was melted at a high temperature and cooled in the same manner as in Example 1 to obtain a colorless mass. It was only.

  Add the powdered refractory waste material so that the chromia content is 0.1 to 0.5 wt% of the total to the above blend, mix the whole, melt at high temperature like rubies and cool, The resulting emerald mass was obtained.

Example 3
A powdered refractory waste material obtained from a magnesia refractory containing 20% by weight of chromia is added to each commercial product of sodium carbonate, lithium oxide, aluminum hydroxide, boron oxide, silica, magnesium hydroxide, and iron oxide. It was added so that it might become 0.1 to 0.5 weight% of the whole, this composition was melted, and when it cooled, the green lump was obtained.

  As a result of analysis, it was confirmed that this was a tourmaline containing chromium having the following composition. Moreover, it was confirmed that when this lump was heated, it was charged with static electricity, which is a characteristic characteristic of tourmaline.

Composition of tourmaline: AD ₃ C ₆ (BO ₃ ) ₃ Si ₆ O ₁₈ (X) ₃ Y
A: Na, Ca
D: Li, Al, Mg, Fe
C: Al, Cr, Fe, Mg
X: OH, O
Y: OH, O, F

Claims (2)

A chrome-containing refractory comprising a used refractory containing at least one selected from the group consisting of alumina, magnesia, silica, zirconia, hafnia and lime, as a raw material for artificial gemstones, containing chromia Recycling method. The method for recycling a chromium-containing refractory according to claim 1, wherein the artificial jewel is produced by pulverizing, heating and melting the used refractory.