JP2001157885A - Method for detoxifying aluminum residual ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide new technique for efficiently treating aluminum residual ash without supplying a large quantity of energy from the outside not only to detoxify aluminum residual ash but also to pyrolyze a very small amount of dioxin contained in aluminum residual ash. SOLUTION: In a reaction container housing a mixture to be treated of ferrous oxide type waste and aluminum residual ash, aluminum residual ash is detoxified by starting thermit reaction in the vertical cross-sectional direction of the mixture to be treated by a thermit reaction initiator and advancing secondary thermit reaction in the lateral direction of the mixture to be treated by the generated heat of reaction to oxidize metal aluminum and an aluminum compound in aluminum residual ash.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an iron oxide-containing waste.
The present invention relates to a novel technology for detoxifying aluminum residual ash (hereinafter referred to as “aluminum residual ash”) generated in the process of recycling aluminum in the coexistence of steel dust, steelmaking dust, etc., by subjecting it to a thermite reaction.

[0002]

2. Description of the Related Art Aluminum dross generated by recycling aluminum is pulverized and then subjected to a portion having a large particle size.
(Mesh ash) and small residual aluminum ash. Since mesh ash usually contains metallic aluminum in an amount of 20% by weight or more, it is redissolved to recover aluminum or used as a heat insulator in the steelmaking / steel making process.

On the other hand, aluminum residual ash having a small particle size is usually 10
It contains about 2% by weight of metallic aluminum and about 2 to 20% by weight of aluminum nitride. However, since the content of metallic aluminum is low, it is not useful as a recycled material.
Disposed as industrial waste. However, aluminum residual ash absorbs moisture in the air and is partially hydrolyzed to generate flammable gas such as hydrogen gas and ammonia gas, so that it is difficult to perform landfill treatment. Therefore, it is desirable to hydrolyze the aluminum residual ash in water in advance, but this still involves the danger of ignition and explosion due to the generated gas, and also increases the cost due to long-term treatment. Furthermore, dioxin contained in trace amounts in aluminum ash cannot be detoxified by hydrolysis, so it is necessary to oxidize at high temperature for a long time to detoxify it. There are difficulties.

[0004] In the case where aluminum residual ash is accommodated in a reactor and energy is supplied from the outside to advance the thermite reaction, the reaction cannot be controlled, so that the refractory of the reactor wall is damaged; Since the carbon dioxide gas generated inside is reduced to carbon monoxide gas, it is necessary to take measures against exhaust gas; there are problems such as an increase in energy cost, which is not practical.

[0005] In order to prevent the hydrolysis of aluminum residual ash,
There is also a method of landfilling in a sealed container, but there are concerns about long-term safety.

[0006] Under such circumstances, illegal disposal or treatment such as illegal dumping and illegal export of aluminum residue ash is also performed.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a method for efficiently treating aluminum ash and detoxifying the aluminum ash without requiring a large amount of external energy supply. The main object of the present invention is to provide a new technology capable of thermally decomposing a trace amount of dioxin contained in a slag.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted research while keeping in mind the current state of the prior art as described above, and as a result, have found that a mixture to be treated consisting of aluminum ash and iron oxide-containing waste is converted into a reaction vessel. When the thermit reaction is allowed to proceed in the vertical cross-sectional direction of the mixture in the reaction vessel in a state of being housed therein, it has been found that the problems of the prior art are greatly reduced or substantially eliminated, and the present invention is completed. Reached.

That is, the present invention provides the following method for detoxifying aluminum residual ash. 1. In the reaction vessel containing the mixture to be treated with aluminum residual ash and iron oxide waste, a primary thermite reaction is started in the longitudinal section direction of the mixture to be treated by the thermite reaction initiator, and the heat generated thereby causes the reaction of the mixture to be treated. A method for detoxifying aluminum residual ash, comprising oxidizing metallic aluminum and aluminum compounds in aluminum residual ash by advancing a secondary thermite reaction in a lateral direction. 2. Item 3. The method for detoxifying aluminum residual ash according to item 1, wherein the aluminum residual ash having a metal aluminum content of 5 to 15% by weight is used. 3. Item 2. The method for detoxifying aluminum residual ash according to Item 1, wherein the iron oxide-based waste is at least one of ironmaking dust, steelmaking dust, and rolling scale. 4. Item 3. The method for detoxifying aluminum residual ash according to Item 1, wherein the iron oxide-based waste, aluminum residual ash, or a mixture to be treated composed of both are previously dried. 5. Item 3. The method for detoxifying aluminum residual ash according to Item 1, wherein at least one of aluminum mesh ash, aluminum powder, aluminum foil pieces and aluminum sheet pieces is mixed with the mixture to be treated as auxiliary components. 6. After a thermite reaction initiator composed of a mixture of an aluminum powder and an iron oxide powder is charged into a combustible material cylindrical body or an aluminum cylindrical body, at least one of the cylindrical bodies is accommodated in a reaction vessel. Item 3. The method for detoxifying aluminum residual ash according to Item 1, wherein the mixture is arranged so as to reach the upper part to the lower part of the mixture, and the primary thermite reaction is performed by igniting a thermite reaction initiator. 7. After arranging the thermite reaction initiator composed of a mixture of the aluminum powder and the iron oxide powder vertically vertically concentrically from the top to the bottom of the cylindrical reaction vessel containing the mixture to be treated, the thermite reaction initiator is ignited, Item 2. The method for detoxifying aluminum residual ash according to Item 1, wherein the primary thermite reaction is performed. 8. Item 1. The primary thermite reaction according to the above item 1, wherein the glass tube is passed from the outside of the reaction vessel to the position of the thermite reaction initiator inside, and a laser beam is irradiated through the glass tube to ignite the thermite reaction initiator and perform a primary thermite reaction. Detoxification method of aluminum residual ash. 9. Item 3. The method for detoxifying aluminum residual ash according to Item 1, wherein the mixture to be treated is reacted in a state where an inorganic layer and a combustible material layer are sequentially provided along the inner surface of the reaction vessel.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Aluminum residual ash to be treated by the method of the present invention has an aluminum content of about 5 to 15% by weight, and its calorific value is low even when subjected to a thermite reaction.

Further, since aluminum residual ash contains a large amount of hygroscopic chloride, 3 to 4% by weight absorbed from the air
It often contains a certain amount of water. When subjected to a second thermite reaction described below in this state, vaporizable components (such as water, chloride, and a small amount of zinc oxide) are vaporized, which hinders the progress of the thermite reaction, which is a solid-phase reaction. Therefore, when the aluminum ash contains water of about 1% by weight or more, the aluminum ash or the mixture to be treated with the aluminum ash and the iron oxide-containing waste described below is preliminarily heated at about 100 to 200 ° C. By heating and drying, it is desirable that the total water content be about 1% by weight or less so as not to inhibit the thermite reaction.

In the present invention, examples of the iron oxide source which is an essential component for causing the secondary thermite reaction include iron-making dust, steel-making dust, and rolling scale.

[0013] In the present invention, in a powdery mixture to be treated comprising aluminum residue ash, iron oxide-based waste (iron-made dust, steel-made dust, electric furnace dust, sludge-heated oxidized product, etc.) and aluminum dross, aluminum -Thermite reaction with iron oxide mixed powder (thermit reaction initiator)
(Primary thermite reaction), and the generated heat induces a thermite reaction (secondary thermite reaction) of the mixture to be treated. Aluminum and its compounds (such as aluminum nitride and aluminum carbide) are oxidized and rendered harmless. At this time, iron oxide derived from iron-based waste is reduced at the same time into iron fine particles, and a chemically stable product is obtained.

The remaining components do not cause secondary pollution even if they are landfilled.

The present invention provides a method for generating a primary thermite reaction with a thermite reaction initiator, igniting a powdery mixture to be treated by heat generated by the primary thermite reaction to generate a secondary thermite reaction, It is essential to control the direction of reaction and the reaction temperature, and to shut off the mixture to be treated during the secondary thermite reaction from the air and cool and collect the vapor of the vaporizable components generated.

Hereinafter, each component of the present invention will be described in detail. 1． Reaction progress direction and ignition method In general, when the mixture to be treated contains zinc oxide, chloride, alkali metal, etc., as the thermite reaction progresses, the vaporized components such as reduced zinc, alkali, chlorine, etc. Becomes a vapor and desorbs from the solid phase. The target mixture to be treated by the present invention has a low aluminum content and low reactivity.For example, a thermite reaction (primary thermite reaction) is performed using a thermite reaction initiator composed of a mixture of aluminum powder and iron oxide. Raise,
It is necessary to forcibly start the thermite reaction (secondary thermite reaction) of the mixture to be treated by the reaction heat.

According to the study of the present inventor, the primary thermite reaction is used to ignite the vertical cross section of the mixture to be treated filled in the container to cause the secondary thermite reaction to proceed in the lateral direction or to ignite from below. When the secondary thermite reaction proceeds upward, unexpectedly, it has been found that the thermit reaction continues to the end in the entire mixture to be treated at a reaction temperature as low as about 1000 ° C. did. Furthermore, according to the analysis of the reaction products, zinc oxide, which may be present in the mixture to be treated, hardly vaporizes even if reduced at this low reaction temperature, and large amounts of alkali and chlorine are present. A portion was also found to remain in the reaction product. On the other hand, it was also revealed that aluminum metal and aluminum nitride were completely oxidized and made harmless.

When the secondary thermite reaction proceeds from above to below the mixture to be treated filled in the container, the upper thermite reaction initiator (primary thermite material)
Completely melts, and the mixture immediately below it also melts, so that it becomes "capped" by the molten slag phase. Therefore, the volatilization of the vaporizable component vaporized by the reaction may be hindered to stop the reaction.

Further, when the secondary thermite reaction proceeds upward by ignition from below, the reaction proceeds reliably, but if a small amount of dioxin is contained in the mixture to be treated, the dioxin can be reduced. There is a risk of vaporizing before it is pyrolyzed and dissipating from above.

Therefore, it is particularly preferred that the secondary thermite reaction proceeds in a direction transverse to the vertical cross section of the mixture to be treated filled in the container. In this case, even if the dioxin is vaporized, the gasified dioxin volatilizes from the vertical gap formed by the high-temperature primary thermite reaction, comes into contact with the high-temperature reaction product gas, and is thermally decomposed. Practically, a lid is placed on the top of the reaction vessel,
By guiding the reaction product gas out of the apparatus through the vent provided in the lid, the detoxification of aluminum ash and the thermal decomposition of dioxin can be performed simultaneously and reliably.

In the present invention, a thermite reaction (primary thermite reaction) composed of a mixture of metallic aluminum and iron oxide is performed in order to allow the reaction (secondary thermite reaction) of the mixture to be treated accommodated in the reaction vessel to proceed uniformly. Use an initiator. The initiator and the mixture to be treated are significantly different in terms of the reaction rate of the thermite reaction. That is, the reaction rate of the initiator is about 100 cm / min, while the reaction rate of the mixture to be treated is about 1 cm / min. Therefore, in the case where the thermite reaction initiator is arranged in a bar shape, a layer shape, or concentric circles in the vertical direction (a tilt of about ± 10% is not a problem) in the mixture to be treated, the starting point in the mixture to be treated is The primary thermite reaction by the agent can proceed rapidly in the vertical cross-sectional direction.

The heat generated by the primary thermite reaction heats the mixture to be treated to a high temperature, so that the secondary thermite reaction proceeds from the vertical direction to the lateral direction even in the mixture having a low reactivity.

Regarding the ignition of the thermite initiator,
There are no restrictions on the heat source, ignition means, etc. For example, it can be performed by an electric means from an opening provided above the reaction vessel. Alternatively, a glass tube may be provided from the outside of the reaction vessel to the position of the thermite reaction initiator, and a carbon dioxide laser beam may be irradiated to ignite the thermite reaction initiator.

It is preferable that the aluminum ash and the iron-based waste, or the mixture to be treated composed of both, be dried and / or heat-treated before the thermite reaction. 2. Properties of reaction products and removal of vaporized components by reaction temperature The shape and components of the reaction products are greatly affected by the temperature of the second thermite reaction.

In the study underlying the present invention, the secondary thermite reaction was carried out by changing the zinc oxide content and the iron oxide / metal aluminum ratio in the mixture to be treated, as described in detail below. .

The mixture to be treated is composed of an iron oxide source and metal Al
It was prepared by mixing with the source mixture. Iron oxide source is iron oxide alone or iron oxide and electric furnace dust (Zinc content; ZnO
35% by weight).

As a result, the following has been found. The reaction temperature of the secondary thermite reaction is determined by the
Although it depends on the Al content, the amount of water adsorbed from the air, and the like, the composition range used here is usually about 1000 to 1300 ° C. As the metal Al content increases, the reaction temperature increases, and as the metal Al content decreases, the reaction temperature decreases.

When the metal Al content is less than 5% by weight,
Secondary thermite reaction cannot be sustained. In contrast, metal
When the Al content exceeds 15% by weight, the maximum temperature of the secondary thermite reaction exceeds 1300 ° C, and low boiling compounds such as zinc, chlorides and alkali metals are vaporized and removed, but the slag phase is complete. And become strong. In addition, the amount of generated gas increases, and it is necessary to collect and detoxify the gas.

However, when the secondary thermite reaction temperature is 1000
When the composition of the mixture to be treated is adjusted to about 1300 ° C., zinc, chloride and alkali metal hardly evaporate, so that a large amount of aluminum ash can be treated with a simple apparatus. When the Al content in the mixture to be treated is too small, the temperature of the secondary thermite reaction does not reach about 1000 ° C., and thus the thermit reaction may not be able to be continued. Therefore, it is desirable to use aluminum residual ash having an Al content of about 5 to 15% by weight, more preferably about 9 to 12% by weight. Alternatively, if the Al content in the mixture to be treated is too small, aluminum dross, aluminum mesh ash, aluminum powder, aluminum foil pieces, aluminum sheet pieces, etc. may be added to the mixture to be treated.

When the content of the iron oxide in the mixture to be treated is too small, an iron oxide-containing by-product such as a rolling scale may be added. 3. Collection of vaporized components The vaporized components are taken out of the container through the opening provided at the top of the refractory reaction vessel containing the mixture to be treated, and cooled or washed with water to remove the purified gas into the atmosphere. An opening in the refractory vessel, which can be discharged to the refractory vessel, can also be used to ignite the thermite initiator. 4. Separation of reaction product from reaction vessel It is practically desirable that the thermite reaction vessel can be repeatedly used at a high temperature of 1000 ° C. or higher. The reaction vessel is formed of a refractory material. Known refractory materials include iron-based refractory metals (such as ordinary steel and heat-resistant alloy steel), oxide-based and nitride-based refractory materials used in metal melting vessels and the like (magnesia-based refractories, chromium-based materials). Refractory, etc.).

However, since the refractory material easily adheres to the thermite reaction product, it may be difficult to take out the reaction product from the reaction vessel or reuse the reaction vessel. In such a case, before performing the thermite reaction, the inorganic layer (sand, thermite reaction product, etc.) and the flammable or carbonizable material layer (corrugated cardboard, cardboard, By sequentially providing paper towels, plastic sheets, etc.), adhesion of reaction products can be prevented and the heat insulation of the reaction vessel can be enhanced. The combustible material or carbonizable material layer is carbonized without burning and in a state where the original shape is substantially maintained. The carbonized layer prevents diffusion of zinc and the like to the inorganic layer and the inner wall of the reaction vessel, and facilitates taking out of the solidified porous reaction product from the reaction vessel.

[0032]

According to the present invention for treating aluminum ash in the presence of iron oxide-containing waste, the following effects can be achieved. 1. The metal aluminum and aluminum compounds in the residual aluminum ash can be oxidized and easily detoxified without supplying a large amount of energy from the outside. 2. Since the solid reaction product is chemically stable, it can be granulated by itself or after wet-kneading with clay. The granulated material is useful as a raw material for ceramics, an alternative material for fluorite added to slag, or as an additive for preventing decay (dandruff) of slag at the reduction stage of electric furnaces and refining slag outside the furnace. 3. It can completely decompose dioxin contained in trace amounts of aluminum residue ash and iron / dust dust.

[0033]

Hereinafter, the present invention will be described more specifically with reference to examples. <Ignition method> Thermite reaction initiator is aluminum powder
(Particle size 10-100 μm) and iron oxide powder (particle size 1-10 μm) in a weight ratio of 3
Prepared by mixing in pairs 8. A magnesium ribbon having a thickness of 1 mm, a width of 5 mm, and a length of 5 cm was protruded from the surface of the thermite reaction initiator, and this was used as a fuse. When the tip of the magnesium ribbon is heated with a gas burner, it is ignited instantly, and at the same time burns out, ignites the thermite reaction initiator. Example 1 A reaction vessel 1 (thickness: 2.5 cm, internal dimensions: 10 cm in length × 10 cm in width × 15 cm in height) of a 1.5 liter capacity refractory insulation material schematically shown in FIG. Cardboard paper (not shown) having a height of 15 cm was placed at an interval of 10 mm, and a space 13 between the inner surface and the cardboard was filled with sand 13 having a particle size of about 1 to 2 mm. Then, rolled scale iron oxide alone or rolled scale iron oxide and electric furnace dust (the zinc content is 35% by weight as Zn) is placed in the rectangular cylindrical inner space surrounded by corrugated paper.
(Iron oxide source), and metallic aluminum content
After 2 kg of the mixture 3 to be treated consisting of 9.3% aluminum ash was filled, a lid 5 made of fire-resistant steel was placed. Around the side of the charged mixture 3 to be treated, about 110 g of a thermite reaction initiator composed of iron oxide powder and Al powder was layered into a layer 7 having a thickness of about 1 cm.
Previously filled. Next, the mixture to be treated is heated to 150 ° C.
After heating and drying for 2 days, a hole having a diameter of 1 cm was made in the center of the side wall, a quartz tube was inserted to the center of the mixture to be treated, and a thermocouple (not shown) was installed. Next, an opening (not shown) of the lid 5
, And the thermite initiator was ignited.

When the thermite reaction initiator on one side is ignited, the primary thermite reaction instantaneously proceeds in the downward direction to form a cavity 9 in the vertical direction, and the mixture to be treated in contact with the cavity 9 is substantially entirely formed. It was fired at the same time. Thereafter, the secondary thermite reaction proceeded slowly in the lateral direction (rightward in the drawing) of the mixture 3 to be treated, and reached the opposite side filled with sand similarly, and the reaction was completed. During that time, the apparent shape and volume of the mixture to be treated 3 did not change, and in the case of a composition containing zinc oxide, a slight gas was generated from the cavity 9.

FIG. 2 is a graph showing a temperature change measured by a thermocouple installed at the center of the mixture to be treated. Sample N
o.In any of 1-3, when the secondary thermite reaction surface in the mixture to be treated reaches the thermocouple installation position, the temperature rises rapidly, reaches approximately 1000-1100 ° C, and stays at the same temperature for 1 minute or more. After maintaining the temperature, the temperature drops slowly. Since dioxin is reported to decompose within 1 second at 800 ° C., it is clear that dioxin is completely decomposed according to the present invention.

When the reaction vessel 1 was left standing for one day and cooled, a readily disintegrable solid reaction product was obtained. The reaction product was poured into an aqueous sodium hydroxide solution (concentration: 3 mol / l),
Although heated to 0 ° C., no gas generation was observed in any of the samples, and no smell of ammonia was felt.

The composition of the mixture to be treated (sample Nos. 1 to 3)
Table 1 shows the reaction temperature and the properties of the reaction product.

[0038]

[Table 1]

In place of the reaction vessel shown in FIG. 1, a cylindrical reaction vessel having the same internal volume is used, and a thermite reaction initiator is arranged in a columnar shape in the vertical direction at the center of the reaction vessel. In the case of performing the processing, substantially the same results as described above were obtained. Example 2 Using the same reaction vessel as in Example 1, the mixture to be treated having the composition shown in Table 2 was treated.

In this embodiment, a mixture of aluminum residual ash and mesh ash (metal Al content = 15) was used as the metal Al source.
Wt%), and the same electric furnace dust as in Example 1 was used.

The progress of the reaction was almost the same as in Example 1, except that the reaction temperature was about 100 ° C. higher than that in Example 1, and the mixture to be treated containing electric furnace dust was removed from the cavity at the ignition point. Moderate generation of white smoke was observed. During the reaction, the apparent shape and volume of the mixture to be treated hardly changed, and the properties of the reaction product were almost the same except that they were slightly harder than in Example 1.

Table 2 shows the compositions, reaction temperatures, and properties of the reaction products of the three kinds of the mixture to be treated (samples Nos. 4 to 6).

[0043]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a perspective view showing an outline of a reaction vessel used in the method of the present invention.

FIG. 2 is a graph showing a temperature change measured by a thermocouple installed at the center of the mixture to be treated during the secondary thermite reaction in Example 2.

[Description of Signs] 1—Reaction vessel 3—Material to be treated 5—Lid 7—Thermit reaction initiator 9—Cavity 11—Partition

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Shuhei Miyauchi 2-7-1, Ayumino, Izumi-shi, Osaka Prefecture Osaka Institute of Advanced Industrial Science and Technology (72) Taizo Imoto 2-7-1, Ayumino, Izumi-shi, Osaka No. Within the Osaka Prefectural Institute of Industrial Science and Technology (72) Kazuya Iwasaki 2-7-1, Ayumino, Izumi-shi, Osaka Prefecture Inside the Osaka Prefectural Institute of Industrial Science and Technology (72) Inventor Masahiro Mori 2-7-1, Ayumino, Izumi-shi, Osaka No. 1 Inside the Osaka Prefectural Institute of Industrial Science (72) Inventor Kiyoshi Yamazaki 2-7-1, Ayumino, Izumi-shi, Osaka Pref. Inside the Osaka Prefectural Institute of Industrial Science and Technology (72) Inventor Shunsaku Odadai, Osaka Sayama-shi, Osaka 3-22-2

Claims (9)

[Claims] 1. A primary thermite reaction is started in a longitudinal section of a mixture to be treated by a thermite reaction initiator in a reaction vessel containing a mixture to be treated of aluminum residual ash and iron oxide waste, and the heat generated A secondary thermite reaction proceeds in the lateral direction of the mixture to be treated, thereby oxidizing metallic aluminum and aluminum compounds in the aluminum residual ash. 2. The method for detoxifying aluminum residual ash according to claim 1, wherein aluminum residual ash having a metal aluminum content of 5 to 15% by weight is used. 3. The iron oxide-based waste is at least one of ironmaking dust, steelmaking dust, and rolling scale.
A method for detoxifying aluminum residual ash according to Item 1. 4. The method according to claim 1, wherein the iron oxide-based waste, the aluminum ash or the mixture to be treated comprising both are dried in advance.
A method for detoxifying aluminum residual ash according to Item 1. 5. The method for detoxifying residual aluminum ash according to claim 1, wherein at least one of aluminum mesh ash, aluminum powder, aluminum foil pieces and aluminum sheet pieces is mixed as an auxiliary component into the mixture to be treated. 6. After a thermite reaction initiator comprising a mixture of an aluminum powder and an iron oxide powder is filled in a combustible material cylindrical body or an aluminum cylindrical body, at least one of the cylindrical bodies is placed in a reaction vessel. 2. The method for detoxifying aluminum residual ash according to claim 1, wherein the mixture is disposed so as to reach from the upper part to the lower part of the mixture to be treated, and the primary thermite reaction is performed by igniting a thermite reaction initiator. 7. A thermite reaction initiator comprising a mixture of an aluminum powder and an iron oxide powder is disposed vertically concentrically vertically from the upper part to the lower part of a cylindrical reaction vessel containing the mixture to be treated. The method for detoxifying aluminum residual ash according to claim 1, wherein the primary thermite reaction is performed by igniting the aluminum. 8. A first thermite reaction is carried out by passing a glass tube from the outside of the reaction vessel to the position of the thermite reaction initiator inside and irradiating a laser beam through the glass tube to ignite the thermite reaction initiator. Item 1
A method for detoxifying aluminum residual ash according to Item 1. 9. The method for detoxifying aluminum ash according to claim 1, wherein the mixture to be treated is reacted in a state where an inorganic layer and a combustible material layer are sequentially provided along the inner surface of the reaction vessel.