JP2000336420A - Method for decomposing and recovering treating gas for aluminum residual ash utilizing metal smelting and refining unburned gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote a thermal decomposition reaction and to change gas into the pollution-free and the resource by recovering gas treating aluminum residual ash and blowing this gas into high temp. recovering gas generated at the metal smelting and refining time. SOLUTION: The aluminum residual ash stored in a hopper 1 is discharged with a feeder 2 and charged into a rotary furnace 3. Water is poured into the rotary furnace 3 and aluminum carbide and aluminum nitride in the aluminum residual ash, are reacted with the water at 20-50 deg.C the temp. in the furnace, to generate hydrocarbon and ammonia gas. The generated ammonia gas is dissolved into the water added in the aluminum residual ash to raise pH in this water. Aluminum oxide covering the metallic aluminum contained in the residual ash is dissoved with the high pH water and the metallic aluminum is exposed and reacted with the water to generate hydrogen. This reaction has large calorific value and brings about rapid heat-up in the reaction system. The aluminum residual ash in the rotary furnace 3 is promoted in this reaction with the heat-up to vaporize un-reacted moisture. The treated material 6 can be used for slag-making material in the steel-making.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for detoxifying and decomposing aluminum residual ash processing gas using gas generated during metal production and refining, and simultaneously recovering the gas together with the gas.

[0002]

2. Description of the Related Art In a converter refining process for producing molten steel from molten pig iron or the like, a high-temperature recovered gas mainly composed of carbon monoxide is used.
(Hereinafter, this gas is simply referred to as “LDG”). In the past, this LDG was mixed with air at the discharge port (furnace port) of a smelting and refining furnace and burned, and the resulting high-temperature exhaust gas was used as a heat source for a boiler. However, this method has many troubles caused by dust in the exhaust gas, and has been a main cause of a reduction in the operation rate of the manufacturing / refining operation. Thereafter, the exhaust gas has been recovered as a fuel gas as an unburned gas due to the development of technology, and this has led to a dramatic improvement in the operation rate of the production and refining furnace.

[0003] That is, this LDG usually contains a large amount of dust mainly composed of iron. However, since the temperature is as high as about 1500 ° C, the LDG is collected by a venturi scrubber installed in the middle of a collection duct and cooled. After being stored in a gas holder, it is used as fuel gas. In addition, many uses of the high-temperature sensible heat of the LDG have been proposed since ancient times.

For example, in Japanese Patent Application Laid-Open No. Sho 56-44710, a part of an LDG once recovered and cooled to room temperature is
A method has been proposed in which a convection type heat exchanger is provided after dry dust collection to reduce heat by blowing into a high-temperature LDG as a refrigerant to lower the temperature. Japanese Patent Publication No. 56-21327 proposes a method in which a hot water heat exchanger is provided in the middle of a cooling water circulation system provided in a radiating section of a converter duct to recover hot water. In Japanese Patent Publication No. 57-15171,
A method is disclosed in which a moving layer of coke grains is provided in the middle of a converter gas duct, the coke is red-heated by LDG sensible heat, and steam is blown into this to generate water gas. JP-A-58-11712 proposes a method of recovering sensible heat of an LDG by installing a collision reversal type dry dust collector in the middle of a converter gas duct and a convection heat exchanger downstream of the dry dust collector. ing.

[0005] In Japan, about 350,000 tons of aluminum residue ash is generated annually, of which about 120,000 tons are provided for landfill disposal. The aluminum residue as used herein means the following. That is, in the process of dissolving aluminum, when metal aluminum comes into contact with air, aluminum dross including aluminum oxide and aluminum nitride is generated. However, since this aluminum dross has a high content of metal aluminum, a machine called MRM is used. By 1
The secondary squeezing and secondary squeezing are performed to collect a desired metal component. In such a processing step, the residue after the secondary squeezing is called aluminum residual ash.

[0006] When the above aluminum residue ash is landfilled as it is, it comes into contact with rainwater or the like to generate gas by the following reaction. _{Al 4 C 3 + xH 2 O} = 4Al (OH) 3 + yCnHm + zCm'Hn '·· (1) AlN + 4H 2 O = Al (OH) 3 + NH 4 OH ···· (2) Al + 3H 2 O = Al ( (OH) ₃ + 3 / 2H ₂ ··· (3) All of these reactions are exothermic, and the reaction is accelerated as the temperature rises. In the case of landfill disposal, detoxification treatment such as removal heat treatment and removal of odor is required beforehand.

As a method for treating aluminum residual ash, a method is generally used in which aluminum residual ash is put into a large amount of water, a hydrolysis reaction is caused, gas is released, and then landfill is performed.
Other methods include the following. Tokuhei 7-3290
In the publication No. 1, the water content is 5 to 30 with respect to the residual aluminum ash.
% After adding water in advance,
A method of firing at 500 ° C. is disclosed. JP-A-9-1
No. 76752 discloses a method of simultaneously treating aluminum residual ash and aluminum sludge with water for 100 parts by weight of aluminum residual ash.
There is disclosed a method in which water in aluminum sludge is added so as to be 20 to 300 parts by weight and then heated to 700 to 1000 ° C. As for the dry treatment method, for example, in “Aluminum dross treatment technology using a rotary arc furnace” (Resource Processing VOL.45 No.1 ('98 -Spring)), aluminum residue ash is removed using an arc furnace. After heating to about 1300 ° C., air is supplied into the furnace for 90 to 120 minutes to decompose and oxidize chlorides and nitrides.

[0008]

Conventionally, as a method for recovering sensible heat of exhaust gas from a heating furnace, a heat treatment furnace, or the like, a multi-tube heat exchanger is installed in the middle of an exhaust gas duct to exchange heat and recover as hot air or steam. The method of doing is general. However, LDG is a gas that is generated intermittently in the first place, and since the gas contains a large amount of metallic iron dust, it is difficult to install an obstacle such as a multi-tube heat exchanger in the middle of the duct. In addition, metal dust adheres and accumulates on the pipes, causing clogging and blockage, resulting in inoperability. For this reason, various methods for recovering the sensible heat of exhaust gas have been studied, but in fact, they have not yet achieved sufficient results.

For example, in the technique proposed in Japanese Patent Application Laid-Open No. Sho 56-44710, the LDG recovered at an angle is blown into untreated LDG again, so that the processing cost increases and the amount of gas becomes large. The equipment is large, and the economic burden is heavy. Further, in the case of the technique proposed in Japanese Patent Publication No. 56-21327, since the recovered heat is hot water, there is a disadvantage in that the use thereof is extremely limited. In particular, the LDG sensible heat is at a high temperature, and it is not advisable to heat it. In the technique proposed in Japanese Patent Publication No. 57-15171, a moving layer of coke is installed in a duct, and a large amount of active rich dust in LDG adheres to a metal frame of the moving layer.
It may accumulate and become inoperable. Further, the converter is operated intermittently and is usually of an open type. Therefore, there is a red hot coke in the middle of the duct because the intrusion of air can be considered sufficiently. There was a problem. The technique proposed in Japanese Patent Application Laid-Open No. 58-11712 discloses a method in which a simple collision plate is installed in a duct and dust is collected by a difference in inertia between gas and dust. Since it is very fine and has an average of 1 to 2 microns, it is predicted that the dust removal efficiency is low in the collision plate method, and there is a concern that residual dust adheres and accumulates on the downstream heat exchanger. In addition, when recovering the sensible heat of a high-temperature gas containing a large amount of dust generated during metal refining, it is a major problem how to avoid dust adhesion trouble.

[0010] On the other hand, there are still many problems with the conventional aluminum residual ash treatment, that is, problems of preventing odor and heat generation. For example, the most common method is to put aluminum residual ash into a large amount of water and degas, but this method requires a long time for such treatment and completes the reaction. Can not. 7-32
No. 901 and Japanese Patent Application Laid-Open No. 9-176752 disclose heating and sintering after addition of water, which eliminates the offensive odor. However, nitrogen oxides are generated instead. Process is indispensable, which results in a large cost burden. In the dry treatment method using a rotary arc furnace described in the above-mentioned document, the power consumption is 340 kWh per ton of aluminum residual ash. An inexpensive processing method is required.

Accordingly, an object of the present invention is to provide a method capable of simultaneously solving the problem of bad odor and heat generation in the gas for treating aluminum residual ash and the problem of dust and low recovery in the gas for producing and refining metals. It is to propose.

[0012]

Means for Solving the Problems The present invention avoids the odor and heat generation of the aluminum residual ash processing gas on the one hand, and on the other hand, the completely different types of industries of metal and refining the efficient recovery of the sensible heat of the hot gas during refining. It is a way to solve the problems that we have together by skillfully combining each other's technologies.
In other words, the generated gas containing ammonia gas during the aluminum residual ash processing, that is, the aluminum residual ash processing gas is recovered without burning, and is blown into the high-temperature recovered gas generated during metal refining and refining. By utilizing the catalytic action of metallic iron contained as dust and the sensible heat of the high-temperature recovery gas, the aluminum residual ash processing gas is thermally decomposed,
This is a method of recovering the metal and refining gas together.

Although the composition of the aluminum residue ash gas varies depending on the aluminum residue ash composition, it is approximately 55% hydrogen and ammonia 40%.
%, About 5% of hydrocarbon gas and other gases. The gas to be decomposed is mainly ammonia gas which is a source of offensive odor and pungent odor. The decomposition reaction of ammonia gas is (4)
It is an endothermic reaction as shown in the equation. 2NH ₃ → N ₂ + 3H ₂ -13 kcal / mol (4) Therefore, thermal compensation is required for the reaction. In the present invention, as the heat source, the sensible heat possessed by the LDG, which has been discharged unnecessarily as hot wastewater for gas purification and cooling at present, is effectively utilized. Furthermore, the decomposition reaction of the aluminum residual ash processing gas is promoted by utilizing the catalytic function of metallic iron and iron oxide, which are the main components of the dust contained in the LDG, and the reaction is completed in a short time to form a reaction between the two gases. It realizes harmless recovery.

In the present invention, since the sensible heat of the LDG is recovered in the form of gas decomposition reaction heat, it is only necessary to blow the aluminum residual ash processing gas into the high-temperature LDG gas. Therefore, there is no need to incorporate such a device, and therefore there is no concern about the hindrance to the metal refining operation as in the conventional method.

[0015]

FIG. 1 shows a process flow of the present invention.
FIG. In FIG. 1, a predetermined amount of aluminum residue ash stored in hopper-1 is cut out by feeder-2.
It is charged into the rotary furnace 3. Water as the other reactant is injected into the rotary furnace 3 through the flow control valve 4 and the pipe 5 at a weight ratio of 0.3 to 0.5 with respect to the amount of residual aluminum ash. Is mixed with the aluminum ash using the rotary motion of the furnace. As a result, in the rotary furnace 3, the aluminum carbide and aluminum nitride in the residual aluminum ash were converted to the above (1) at a furnace temperature of 20 to 50 ° C.
Reacts with water by the reaction shown in formulas (3) to generate hydrocarbons and ammonia gas. Then, the generated ammonia gas is dissolved in water added to the aluminum residual ash to increase the pH. The aluminum oxide covering the metal aluminum contained in the residual ash is dissolved by the high pH water,
Metal aluminum is exposed and comes into direct contact with water,
Hydrogen is generated by the reaction shown in equation (3). Since this reaction generates a large amount of heat, it causes a rapid rise in the temperature of the reaction system,
The generated gas causes fluidization of the reaction powder. That is, as the temperature of the aluminum ash in the rotary furnace 3 rises, the reaction is further promoted, and unreacted water evaporates, drying is completed, and the reaction stops.

The aluminum ash after the reaction is discharged as a processed aluminum ash 6 from a discharge port provided at the other end of the rotary furnace 3. Table 1 shows the composition of the residual aluminum ash before and after the treatment. The treated material 6 can also be used, for example, as a steelmaking slag.

On the other hand, the aluminum residue ash processing gas generated from the rotary furnace 3 is in a wet gas state,
After being guided to and pressurized, it is stored in the tank 10. The drain generated when the pressure is increased by the compressor 8 is recycled to the rotary furnace via the pipe 9 because it contains a large amount of ammonia.

The aluminum residual ash processing gas stored in the holder 10 is passed through a flow control valve 11 controlled by an operation signal of a controller 13 into a recovery duct 15 for gas generated from a metal smelting / smelting furnace. It is blown. The recovery duct 1
5, an LDG (converter gas) of about 1500 ° C. generated by the blowing operation of the smelting and refining furnace 14, for example, the converter, flows. Decomposed into hydrogen and nitrogen as shown in the formula,
It is mixed with the LDG to form a modified LDG, and the dust is removed by a venturi scrubber 16 which is a dust removing device, and is cooled by water 17 injected into the venturi scrubber 16. Dust collected water containing dust from the venturi scrubber 16 is discharged from the collection duct 15 to the outside of the system by a drain pipe 18. On the other hand, the reformed gas, which has been dust-removed and cooled, is sent to the gas holder 20 by the induction blower 19, temporarily stored, and then used as fuel.

[0019]

EXAMPLE An aluminum residue ash having the composition shown in Table 1 was used in a rotary furnace.
(Rotary kiln), water was simultaneously injected and mixed in the kiln, and the generated aluminum residual ash processing gas was stored in a tank. On the other hand, hot metal is refined in a 10-ton converter, and aluminum residual ash processing gas is extracted from the storage tank and blown into a converter gas recovery duct generated during the refining, and the resulting gas is decomposed. Was recovered as a reforming converter gas. Table 1 shows the operating conditions of the aluminum residue ash treatment in the rotary kiln, Table 2 shows the results, and Table 3 shows the conditions of blowing the aluminum residue ash treatment gas into the high-temperature recovery converter gas.
And the results of this treatment are shown in Table 4. As shown in Table 4, with respect to the converter gas recovery amount 91Nm ³ / t-steel, by blowing aluminum residual ash process gas 27 nm ³ / min, reformed converter gas recovery amount is increased to 157 nm ³ / t Was collected. The sensible heat recovery of the recovered converter gas consumed to decompose the aluminum residue ash processing gas is 230,900 Kcal, which is 48.3% of the total converter gas sensible heat, and energy can be effectively recovered. The detoxification and recovery of the aluminum residual ash processing gas was achieved.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

[0024]

As described above, the following effects can be obtained by implementing the recovery method of the present invention. Recycling of the gas generated during the treatment of aluminum residual ash, which has been disposed of as a foul-smelling heat-producing gas, will be achieved. By blowing the gas generated at the time of aluminum residual ash processing into the high-temperature metal / refining generated recovery gas, the sensible heat of the high-temperature recovered gas can be effectively utilized as the decomposition reaction heat of the aluminum residual ash processing gas, The amount of recovered gas can be increased. The remaining aluminum ash, which had been discarded as it is, can be recycled as slag for steelmaking.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a processing flow of a method of the present invention. DESCRIPTION OF SYMBOLS 1 Aluminum ash storage hopper 2 Feeder 3 Rotary furnace 4 Water flow control valve 5 Water injection pipe 6 Aluminum residue ash treatment 7 Conduit 8 Compressor 9 Piping 10 Gas tank 11 Gas flow control valve 12 Gas flow meter 13 Control Equipment 14 Refining furnace 15 Duct 16 Venturi scrubber 17 Water 18 Dust collected 19 Induction blower 20 Gas holder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B09B 3/00 303L (72) Inventor Hiroyuki Uesugi 2-2-3 Uchisaiwaicho, Chiyoda-ku, Tokyo Kawasaki Steel Corporation Head Office (72) Inventor Akira Morita 1-34-1 Kambara, Kambara-cho, Anbara-gun, Shizuoka Japan Light Metal Co., Ltd. (72) Inventor Riki Sakakibara 5-3 Tokai-cho, Tokai-shi, Aichi Pref. 72) Inventor Eiji Okada 1-26-5 Toranomon, Minato-ku, Tokyo Toranomon 17 Mori Building 6F F-term in the Metal Materials Research and Development Center (Reference) 3B117 AA02 BA51 4D004 AA44 CA24 CA28 CA48 CB09 DA03 DA06 DA10 4K001 AA02 BA16 4K002 AB04 AD01 BA01 4K056 DB04

Claims (1)

[Claims] An aluminum residual ash processing gas generated when water is injected into aluminum residual ash is blown into a high-temperature recovered gas generated during metal production and refining, thereby producing a part of the metal production and refining gas. A method for decomposing and collecting residual aluminum ash-treated gas using unburned gas produced and refined from metals, characterized by being recovered together.