JPH06102801B2 - Treatment method of aluminum residual ash - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating aluminum residual ash produced after re-refining a molten slag generated during melting and refining of aluminum and aluminum alloys.

[0002]

[Prior art]

[Background of the Technology] During the melting and refining of aluminum and aluminum alloys, a molten slag mainly containing aluminum oxide is generated. This molten slag contains 60 to 8 metallic aluminum.
Since it is contained in an amount of 0% by weight, the aluminum metal content is recovered by applying an ashing machine. However, since the remaining slag from which the metallic aluminum content has been recovered still contains 30 to 40% by weight of the metallic aluminum content, it is re-dissolved and the metallic aluminum content is recovered. The slag that remains after such a process is generally called aluminum residual ash.

This aluminum residual ash still contains 5 to 10% by weight (sometimes 30% by weight sometimes) of metallic aluminum, but at present, it is recovered technically and economically. It is difficult to do so, and the present condition is that this aluminum residual ash becomes the final slag and is disposed of as industrial waste.

[Problem] However, the aluminum residual ash usually has a grain size of 1 mm or less and further contains 65% by weight or more of fine powder of 50 μm or less. Therefore, it is easily scattered during handling, and it is difficult to carry out the work such as transportation and disposal.

Further, in this aluminum residual ash, nitrogen is usually contained as compound nitrogen such as aluminum nitride in an amount of 2 to 6
It is contained by weight%. Therefore, for example, if water is sprayed to prevent the scattering of fine powder,
The nitrogen compounds contained decompose to generate ammonia,
The offensive odor caused by this ammonia gas is dissipated and causes secondary pollution.

The metallic aluminum contained also reacts with water to generate hydrogen gas. Therefore, it is not possible to easily dispose of the aluminum residual ash as it is as industrial waste.

[Conventional Treatment Technology] Aluminum residual ash having such problems is smelted in powder form and used as it is as a slag-forming agent in steel smelting and refining. However, the amount used is extremely small compared with the amount of aluminum residual ash produced.

Therefore, in order to facilitate the handling as industrial waste, as a method for preventing the scattering of fine powder by granulating, (1) aluminum fiber ash is mixed with vegetable fiber, a water-soluble binder and water. Alternatively, it is wet-molded by mixing paper pulp drainage. (2) By devising a granulator, apply high pressure to dry-mold it in a state that can prevent collapse after granulation. Have been tried.

In addition to the above, there has been considered a method in which water is applied to the aluminum residual ash, the generated ammonia is collected, compressed and cooled, and absorbed in liquid ammonia or sulfuric acid to be recovered as ammonium sulfate (ammonium sulfate).

[0010]

However, in the conventional treatment method, metallic aluminum contained in the aluminum residual ash as described above, or hydrogen gas or ammonia gas generated by the reaction of combined nitrogen with water is generated. Handling becomes difficult due to direct secondary pollution by gas or collapse of granulation when granulated.

[0011] Due to such problems, there is a solution to change the aluminum residual ash into a stable compound and reuse it as a resource, or to dispose of it without becoming a secondary pollution source. Is requested.

In the present invention, a stable compound is obtained by solving the above problems, oxidizing the contained aluminum metal, and reducing the content of combined nitrogen so that it does not lead to a secondary pollution source. The purpose is to provide a method for treating aluminum residual ash that can be treated as.

[0013]

In order to achieve the above-mentioned object, the present invention is to supply finely powdered aluminum residual ash to a combustion section of a combustion burner using a gas or liquid fuel, and It is a method for treating residual aluminum ash, which is characterized in that it is jetted and scattered in a flame to oxidize metallic aluminum in residual aluminum ash in a high temperature oxidizing atmosphere and decompose compound nitrogen.

The aluminum residual ash powder is supplied by being diffused and jetted into the combustion chamber from a position close to the combustion burner, and can be guided from the combustion chamber to a cyclone type combustion furnace for secondary combustion. It is suitable.

Further, according to the present invention, it is preferable that the iron oxide powder is jetted into the secondary combustion chamber connected to the primary combustion chamber by the combustion burner, and the thermite reaction with the metallic aluminum in the aluminum residual ash is carried out for high temperature combustion. Is.

[0016]

According to the present invention, the aluminum residual ash to be treated is made into fine powder so that it can be easily diffused, and this fine powder of aluminum residual ash is ejected and scattered into the combustion flame in the combustion furnace to obtain the aluminum residual ash. The metallic aluminum contained therein is suspended in a high-temperature oxidizing atmosphere, rapidly oxidized, and replaced with aluminum oxide.

The aluminum residual ash fine powder diffused and suspended in the combustion gas is decomposed in the high temperature region of aluminum nitride contained by combustion in the combustion chamber by the combustion burner, becomes nitrogen oxides, and is transferred to the exhaust gas. It

In the primary combustion in the combustion chamber, it is not easy to completely oxidize the metallic aluminum content of the aluminum residual ash fine powder. Therefore, the combustion gas containing the fine powder is introduced into the secondary combustion chamber. Further, if it is floated in a high-temperature oxidizing atmosphere and then led to a cooling step to collect the combustion slag, all the metallic aluminum content in the aluminum residual ash is replaced with aluminum oxide. Further, the nitrogen content in the compound nitrogen state becomes a minute amount, is stabilized, and can be disposed in a state where it can be easily disposed of.

Further, by separately sprinkling iron oxide powder in the spraying area of the fine aluminum residual ash powder in the primary combustion and / or the secondary combustion to cause a thermite reaction with the contained metal aluminum to raise the combustion temperature. The burning rate can be increased.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the method for treating aluminum residual ash according to the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining one mode of the processing method of the present invention. In this figure, reference numeral 1 denotes a combustion furnace, in which a secondary combustion chamber 3 formed in a cyclone shape is connected to a primary combustion chamber 2 equipped with a combustion burner 4 and a fine powder supply section 5 of aluminum residual ash to be treated. It has been configured. Reference numeral 6 denotes a combustion slag removal port, which is provided with a rotary valve 7. Reference numeral 10 is a cyclone for cooling, which is connected to an exhaust gas duct 9 from an exhaust port 8 of the combustion furnace 1.
From the exhaust port 11 of 10 to the exhaust gas inlet 16 of the dust collector 15, the duct 12
Connected by. If necessary, an auxiliary burner (not shown) may be provided in the secondary combustion chamber 3 to accelerate the combustion operation.

As the dust collector 15, for example, a bag filter or a dust cotrel is used. The exhaust gas discharged from the secondary side exhaust chamber 17 of the dust collector 15 is preferably subjected to a harmful substance removal treatment through an exhaust gas treatment device (not shown), purified, and emitted to the atmosphere.

The combustion slag a discharged from the combustion slag removal port 6 of the combustion furnace 1 is sent out onto the conveyor 20 through a cooling chamber (not shown). Further, the combustion slag a ′ collected by the dust collector 15 is also discharged onto the conveyor 21 from the discharge port 18 at the bottom of the dust collector 15. The combustion slags a and a'conveyed by both the conveyors 20 and 21 are collected in a hopper 23, supplied to a granulator 24 by the conveyor 22, and granulated to a required size. In the figure, reference numeral 13 is a dust discharge pipe from the cyclone 10 for cooling, and the dust is discharged onto the conveyor 20. Reference numeral 26 is a dust cover, which blows away scattered dust generated in the supply section to the granulator 27.
Is returned to the dust collector 15 or the combustion furnace 1 through the conduit 29. Reference numeral 28 is a water-soluble binder or water sprinkler supplied to the combustion slag a (a ′) sent to the granulator 24. 30 is a storage unit for the granulated combustion slag.

Next, when treating the aluminum residual ash using such a treatment apparatus, the aluminum residual ash sent to the combustion furnace 1 is, for example, fine particles of 300 μm or less. Therefore, it is preferable that fine particles having a large particle size be pulverized by a pulverizer or the like. When pulverized in this manner, the reaction rate of the substance to be treated such as aluminum metal and aluminum nitride having a large surface area is increased.

The finely pulverized aluminum residual ash is diffused and ejected into the primary combustion chamber of the combustion furnace 1 toward the core of the combustion flame by the combustion burner in an appropriate amount. In the primary combustion chamber, it is preferable that a swirl flow is applied to the aluminum residual ash, together with a combustion flame, to actively burn the aluminum ash.

In this primary combustion chamber, an atmosphere in which the temperature at which metallic aluminum is burned (1800 to 2100 ° C.) is maintained, and the aluminum residual ash fine powder is directed toward the core of this primary combustion chamber 2. By being jetted and supplied so as to be in a diffused state, the aluminum residual ash fine powder is actively raised to the combustion temperature at high temperature and burned (reactive oxidation).

Further, while flowing from the primary combustion chamber 2 to the cyclone-type secondary combustion chamber 3 and being swirled in the secondary combustion chamber 3, the primary combustion chamber 2 is previously moved. The remaining aluminum residual ash particles that have not been burnt in place are burned. Simultaneously with this operation, the exhaust gas which has been classified by the combustion sludge and burned is transferred from the exhaust port 8 to the cooling cyclone 10 through the exhaust gas duct 9. The combustion slag a classified in the secondary combustion chamber 3 is dropped and accumulated in the lower part having an inverted conical shape. The dropped and accumulated combustion slag a is gradually discharged by the rotary valve 7 provided in the combustion slag outlet 6, preferably cooled and collected in the slag receiving hopper 23.

On the other hand, the exhaust gas introduced from the exhaust port 8 of the combustion furnace 1 to the cyclone 10 for cooling by the duct 9 has its temperature lowered in the cyclone 10 and the suspended dust entrained therein is classified. It is guided from the exhaust port 11 through the duct 12 to the exhaust gas inlet 16 of the dust collector 15. In the dust collector 15, for example, when the dust collector 15 is a bag filter, the exhaust gas is passed through the filter bag to filter and separate the entrained fine dust, and the secondary side exhaust chamber 17 is a known exhaust gas treatment device. The toxic gas contained therein is processed and released into the atmosphere.

The combustion slag a'collected in the dust collector 15 is conveyed from the exhaust port 18 by a rotary valve to a conveyor.
It is sent to the upper part 21 and collected in the hopper 23 for receiving the slag like the slag a sent from the combustion furnace 1. Note that the combustion slag separated in the cooling cyclone 10 is also discharged as a combustion slag a by discharging the dust discharge pipe 13 onto the conveyor 20 by opening the valve at the bottom appropriately.

Burnt slag a (a ') collected in this way
Is sent from the combustion slag receiving hopper 23 to the granulator 24 via the conveyor 22 in appropriate amounts, and an appropriate amount of the water-soluble binder or water is sprinkled by the sprinkler 28, shaped into pellets by the granulator 24, and stored. After being sent to part 30,
Supplied for exhaust treatment or recycling.

By comparing an example of the result of the burning treatment of the above-mentioned aluminum residual ash with that before the treatment,
As shown in the following table, it can be seen that the content of metallic aluminum and compound nitrogen contained therein is significantly reduced.

[Table 1]

In the above-mentioned aluminum residual ash treatment means, when burning the aluminum residual ash in the combustion furnace 1, in addition to using fuel such as heavy oil or light oil, it is also possible to use pure oxygen for combustion. . In this case, since the combustion temperature can be further increased, the combustion effect can be further enhanced by causing the aluminum residual ash to be jetted and supplied so that the contact with the flame is effective.

Further, as another example of the treatment method of the present invention, an appropriate amount of iron oxide powder is scattered to the primary combustion chamber 2 or the secondary combustion chamber 3, or the combustion part in both the primary and secondary combustion chambers. If it is jetted and supplied, the thermite reaction occurs due to the contact between the metallic aluminum component in the aluminum residual ash fine powder previously sent in the combustion air flow and the iron oxide powder, resulting in a higher temperature atmosphere and combustion of the aluminum residual ash fine powder. The rate is increased to accelerate the oxidation of metallic aluminum and the decomposition of combined nitrogen. In this case, as the iron oxide powder to be used, wastes such as so-called iron rust and dust, which are generated in various processing operations of steel materials, may be used, so that the economical burden is not increased.

The thermal energy of the exhaust gas generated during the above-mentioned combustion process of the aluminum residual ash can be economically enhanced by exchanging the heat energy with cooling water or the like for other purposes.

[0035]

According to the treatment method of the present invention, the stable aluminum oxide is substituted for the metallic aluminum content in the aluminum residual ash, which has been problematic in the conventional exhaust gas treatment. Since it can be decomposed into a compound that is generally stable, it can be easily disposed of and can be disposed of without being a source of pollution. If necessary, it can be reused as a part of steelmaking auxiliary or refractory raw material, or part of raw material for molded products such as roadbed materials if it is refined by pulverizing the treated slag. It's easy.

[Brief description of drawings]

FIG. 1 is a diagram illustrating one embodiment of a method for treating aluminum residual ash according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion furnace 2 Primary combustion chamber 3 Secondary combustion chamber 4 Combustion burner 5 Fine powder supply part of aluminum residual ash 6 Combustion slag extraction port 7 Rotary valve 8 Exhaust port of combustion furnace 9,12 Exhaust gas duct 10 Cooling cyclone 15 Dust collection Device 17 Secondary side exhaust chamber of dust collector 18 Discharge port of dust collector 20, 21, 22 Conveyor 23 Hopper for receiving slag 24 Granulator 28 Water-soluble binder or water sprayer 30 Granulated combustion Slag storage

Claims (3)

[Claims] 1. Finely pulverized aluminum residual ash is supplied to a combustion section by a combustion burner using a gas or liquid fuel to be ejected and scattered into a flame in a combustion furnace, and the aluminum residual ash in a high temperature oxidizing atmosphere A method for treating aluminum residual ash, which comprises oxidizing metallic aluminum and decomposing compound nitrogen. 2. The aluminum residual ash powder is supplied so as to be diffused and jetted into a combustion chamber from a position close to a combustion burner, and is then secondarily burned from the combustion chamber to a cyclone type combustion furnace. The method for treating aluminum residual ash according to claim 1. 3. The high temperature combustion according to claim 1, wherein iron oxide powder is ejected into the primary combustion chamber or a secondary combustion chamber connected to the primary combustion chamber to cause a thermite reaction with metallic aluminum contained in the aluminum residual ash to perform high temperature combustion. Method for treating aluminum residual ash.