JPS62278120A - Treatment of aluminum dross - Google Patents

Abstract

PURPOSE:To obtain useful NH4Cl and Al slug suitable for thermit reaction without causing environmental pollution, by heating a mixture of water and Al dross containing AlN and a chloride in a furnace and collecting produced NH4Cl formed from NH3 and HCl. CONSTITUTION:Al dross composed mainly of AlN and AlCl3 and optionally containing MgCl2 and CaCl2 is mixed with water at a ratio to achieve the reaction formulas I-V in proper quantities. The produced composition is heated at 100-300 deg.C in a furnace an NH4Cl formed from generated NH3 and HCl is collected by a dust-collector. At the same time, a raw material free from harmful impurities and useful for thermit reaction can be obtained.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention provides a process for producing molten alumina etc. using aluminum slag and scale as raw materials. Concerning a method of pre-treatment.

(Prior art) Aluminum slag is an A1°0 slag that emerges on the surface of a molten product during refining of metal aluminum, melting and refining of scrap aluminum, melting and refining of aluminum alloy, etc.
This is the residual material obtained by processing the raw wood slag 3 by crushing it, sifting it, etc., and recovering a portion of the metal aluminum.

The aluminum slag obtained by melting and refining) contains AIN when inert nitrogen gas is blown into the melting and refining process, and AlCl when active chlorine gas is blown into the aluminum slag. Recently, a mixture of nitrogen and chlorine gases has been blown, which in this case contains both AIN and AlCl3. Also, when using 7lux without gas blowing in melting and refining, A
It often contains either IN or A+cL or both.

Furthermore, scale is a thin layer formed and peeled off on the surface of a steel ingot during processes such as continuous casting, rolling, and forging of steel and special steel, and is mainly composed of iron oxide.

A method for producing iron and molten alumina from scale and aluminum slag is known as seen in Japanese Patent Application Laid-Open No. 59-121153. Specifically, dried scale and aluminum slag are mixed and put into a melting furnace, and in the furnace a thermite reaction occurs between metallic aluminum contained in the aluminum slag and iron oxide contained in the scale. By this thermite reaction, iron oxide is reduced to obtain iron, and metallic aluminum is oxidized to obtain molten alumina. With this technology,
It has the advantage of producing useful iron and molten alumina with less energy by using by-products similar to two types of industrial waste.

(Problems to be Solved by the Invention) In the above method, for example, if aluminum slag containing AIN is used, this AIN may react with steam in the furnace to generate ammonia gas, causing a pollution problem. There was sex. Further, AIN remaining in molten alumina sometimes caused deterioration of properties.

Further, when aluminum slag containing AlCl is used, this AlCl reacts with the water vapor in the furnace to generate hydrogen chloride, which may cause a pollution problem.

(Means for Solving the Problems) The present invention has been made to solve the above problems.
The gist is that aluminum nitride and chloride (mainly aluminum chloride, but in some cases M g C+ 2 and C
aluminum slag containing both aCl□);
By heating the mixture containing moisture in a furnace, the aluminum nitride and moisture are reacted to produce ammonia, the chloride and moisture are reacted to produce hydrogen chloride, and finally Ammonia and hydrogen chloride are reacted to produce ammonium chloride, this ammonium chloride is collected by a dust collector, and the contents of aluminum nitride, chloride, and water in the above formulation are adjusted approximately to achieve the above reaction. A method for treating aluminum slag is characterized in that it is prepared in just the right amount.

(Function) When a mixture containing aluminum slag and water is heated in a furnace, aluminum nitride and water react to produce ammonia. Additionally, chloride and water react to generate hydrogen chloride. Finally, ammonia and hydrogen chloride react to produce ammonium chloride, which is collected by a dust collector.

Aluminum nitride, chloride, and water in the above formulation are contained in just the right amount to achieve the above reaction.
Aluminum slag can be processed with almost no pollution, and it can be used as fertilizer or
Ammonium chloride, which is useful as a laxative, can be obtained. In addition, aluminum slag can be used for thermal treatment with scale.
Since harmful substances such as aluminum nitride and chlorides are removed without losing much of the metal aluminum necessary for the nod reaction, it is ideal as a raw material for producing molten alumina etc. by the chill mint reaction.

(Example) An embodiment of the present invention will be described below.

aluminum slag Aluminum slag is prepared with the following ingredients.

(a) Metal aluminum should be 20 to 50% (weight %, same hereinafter). The reason why it was set at 20% or more was to ensure that the chillmint reaction occurred, and the reason why it was set at 50% or less was because
This is to prevent thermite reactions from occurring so violently that they damage the reactor walls.

(b) A I20 shall be 40% or more.

(c) Mg and Mg compounds (MgC1□r M g○
etc.) to 9% or less. The reason for setting it to 9% is to limit the content of spinel in the finally obtained molten alumina, which will be described later, to 40% or less. Mg and M
The g compound eventually becomes MgO, and since this MgO is not reduced by the thermite reaction and has little volatilization, it is difficult to remove in the process of manufacturing molten alumina, and it ultimately becomes spinel and remains in the molten alumina. be. Therefore, when restricting the spinel content as described above, it is necessary to restrict the content in the aluminum slag.

(-) Ca and Ca compounds (Ca Cl 2 , Ca
(O, etc.) is 1% or less. These eventually become CaO, which, like Mg, is difficult to remove in the molten alumina production process, and their eventual contamination with molten alumina is unavoidable, as CaO has a negative effect on the properties of molten alumina. It is necessary to strictly limit the above content rate.

(e) AIN is 15% or less, preferably 10% or less.

(f) Reaction formula (1), which describes the content of AICl3 later, (
2).

Adjust so that there is no excess or deficiency based on (5), so that the weight ratio is AIN:AlCl=1:1.07. In reality, MgC1□ and CaCl2, which undergo almost the same chemical reaction as AlCl, are contained, albeit in trace amounts, and the reaction formula (3) for these chlorides is
4), AIN and chloride (A Ic 13.c
The above weight ratio is determined so that the amount of ac 12°MgC12) is not too much or too little.

During the rolling process, the AIN and the total weight of the chlorides may be adjusted to be approximately equal.

(g) Impurities other than the above (S i, Ti, Fe, Cu
, Cr, Zn and its compounds, NaCl, KCI and A1. C.

etc.) to 5% or less.

As mentioned above, aluminum slag contains AIN,
There are some containing AlCl and some containing both, but usually two or more of these three types of aluminum slag are blended to achieve the above weight ratio of AIN and chlorides such as AlCl. Prepare as follows.

Scale The scale may be made of either ordinary steel or special steel. In large-scale factories, on production lines such as continuous casting, rolling, and forging, scale is collected by water transportation and stored in water tanks, so when taken out from the water tank, it contains 20 to 30% water. There is too much water in this state, so dry it until it contains the appropriate amount.

Here, the appropriate amount is determined based on the reaction formulas (1) to (5) described later, so that there is almost no excess or deficiency, and specifically, in a mixture obtained by mixing aluminum slag and scale, A
The amount is 35% of the total weight of IN and AlCl.

A mixture is prepared by thoroughly mixing the crushed aluminum slag and scale in a mixer. At this time, even when two or more types of aluminum slag are used, it is preferable in terms of work efficiency to mix them together with the scale without mixing them in advance. The weight ratio of aluminum slag and scale is determined based on thermite reaction equations (7) to (16) described below. If there is a lot of scale, Fe20= will remain in the slag, and if there is little scale, A1 will be included in the ferroalloy. In order to ensure the quality of the slag, it is also possible to simultaneously perform 5-b processing based on the calculated amount of scale.

Heat Treatment Next, the material is heated at 100 to 300°C in a drying furnace or a melting furnace that causes the thermite reaction described below. As a result, as shown in equation (1) below, AIN contained in the aluminum slag reacts with moisture to produce ammonia.
In addition, as shown in equations (2) to (4), AIC1 in aluminum slag, and smaller amounts of MgCl2 and CaC
1□ reacts with moisture to produce hydrogen chloride, and further, as shown in equation (5), the ammonia and hydrogen chloride finally react to produce ammonium chloride.

AIN+3820=NH,+Al(O)l),
(1) AICl, +3820=3) IC1+Al(OH
)3 (2) or 2 AlCl, +(3+X))12
0=68C1+Al□O, -XH20(2)'MgCl
□+2 H20= 2 HCl + Mg(OH)2
(3) CaCL+ 2 H20= 2 HCI+Ca(
OH)2 (4)NH,+HC1=NH,CI
(5) The above heating temperature was set to 100'C.
The above is because the water contained in the compound becomes water vapor, so the reaction in equation (1) above becomes rapid at 100'C, and at lower temperatures, equations (2) to (4) This is because hydrogen chloride generated due to the reaction evaporates actively at temperatures above 100"C, and as a result, the reaction of equation (5) occurs rapidly. Also, the reason why the temperature is below 300°C is that , 300'C, a reaction opposite to the above formula (5) occurs and ammonium chloride is decomposed.

Note that decomposition of ammonium chloride occurs at 337°C.
(It varies depending on the pressure inside the furnace). Therefore, if temperature control can be performed accurately, it is possible to maintain the temperature at 300° C. or higher as long as it is below the above decomposition temperature. Even if the temperature inside the furnace is above the decomposition temperature, if the configuration outside the furnace is devised, the decomposed ammonium chloride can be recombined outside the furnace, and the above treatment is possible.

In addition, moisture and aluminum metal in aluminum slag react as follows, and this reaction is similar to (1) to (5) above.
Since the reaction is much slower than that of the formula, only a small amount of metallic aluminum is lost.

2AI+6820=382+2AI(OH)3 (
6) In addition, since the water content is adjusted to be almost exact by pre-drying the scale, the remaining water will not react with metal aluminum as shown in equation (6) and the metal aluminum will not be lost.

In addition, since the weight ratio of chlorides such as AIN and AlCl and water is adjusted as described above, (
Almost all of the ammonia and hydrogen chloride produced in formulas 1) to (4) become ammonium chloride through the reaction in (5), so
Ammonia and hydrogen chloride are rarely scattered, or only in small amounts, and do not cause any pollution.

White smoke is produced by the reactions of formulas (1) to (5) accompanying the heating, and when this white smoke is collected by a dust collector, a powder containing ammonium chloride as a main component is obtained. This powder is useful as a fertilizer or as a fertilizer used for melting and refining aluminum alloys.

In addition, the above formulation contains almost all the metallic aluminum necessary for the thermite reaction with scale, and A
Since it does not contain IN, AlCl, etc., it is optimal as a raw material for producing fused alumina, which will be described later. During this heat treatment, the scale is almost completely dried.

Thermite reaction When the above heat treatment is performed in a drying furnace, the treated aluminum slag is transferred to a melting furnace. When carried out in a melting furnace, the formulation may be used as is.

Then, a small amount of electrode scrap is placed on the surface of the compound in the melting furnace, and electricity is supplied to gently ignite it with an arc. Reactions of formulas (1) to (5) above occur with water vapor, producing some white smoke. When the temperature of the mixture eventually reaches flooO'c, a strike reaction occurs mainly with the metallic aluminum contained in the aluminum slag.

AI+Fe20z=2Fe+AL□O, -194,80
0(7)2A I+3/4F8.04=9/4Fe+
A I201-189,800(8)2A I+3F
eo =aF e1A I20 , -197.900
(9) In the case of special steel scale, the following thermite reaction occurs between the metal aluminum and the metal oxide in the scale.

2A I + Cr20-= 2Cr 10A 120
s-123,800(10)2AI+3NiO=3Ni
+ALO, -216,000(11)2Al+3/2M
o○2=3/2MO+A I20 z-192,90
0(12)2AI+3/2W02=372W+AI. ○
, -196,800 (13) 2A I+3/2S
io 2=3/28 i+ A I203-81,60
0 (14) 2A I+ 3/2T io 2= 3/
'2T i + A I203-68,850 (15
) ΔH (Cat/molA l.oz) Note that a thermite reaction similar to the above occurs between trace amounts of metal oxides other than those mentioned above and metal aluminum.

In addition, A1 in aluminum slag. Thermite anti-3/2F as exemplified below with C, and iron oxide, etc. in the scale.
e20 ff+ 1/2A 14c 3=3F e10A
I20:1+3/2C○-ΔH(16) Furthermore, 5in2 and TiO contained in the aluminum slag
2 also causes a thermite reaction with metal aluminum as shown in equations (14) and (15).

The thermite reaction described above is rapid and generates high temperatures, but the reaction is moderated by substances that do not participate in the thermite reaction, that is, Al 203 contained in the aluminum slag and AlzO* obtained by the above reaction. damage can be prevented.

At the high temperature of the thermite reaction, chlorides such as NaCl and KCI float to the surface, are almost completely volatilized at 1500°C by arc heat, and are collected by a dust collector.

Due to the high heat of the thermite reaction and arc heat, the slag becomes 21
When heated to 00'C and completely melted, the reduced ferroalloy sinks to the bottom due to the difference in specific gravity. This completely separates the slag and ferroalloy.

The thermite reaction and melting may be carried out in any type of electric furnace, such as a resistance furnace, an arc furnace, or an induction furnace.

When the recovery temperature of the ferroalloy reaches 2100'C, the power supply is stopped and the electrode is raised. Then, before this positive charge is applied, the stopper at the bottom of the furnace is removed (tapping), the ferroalloy is allowed to flow out of the furnace, received in a ladle, and then fed in its molten state to the steel melting furnace (hot charge). Alternatively, it may be poured into a mold and sold as an ingot for use in steel production or cast iron melting.

Slowly cooling the slag After applying positive electricity, a heat insulating cover is placed on the top of the furnace and the slag is slowly cooled. The slowly cooled slag is pulverized and sized to be used as abrasive grains for grinding and polishing tools or as a refractory material.

Since the content of impurities in the aluminum slag was restricted, in the above slag, Al2O3 was 91% or more, MgO was 8% or less, and the pond (CaO, Fe=03tSi02.T
iO2, Cr2O, Na2O,20) can be made 1.5% or less. M g O is almost all A1□O
It combines with 0 to form a spinel crystal. Furthermore, almost all of the remaining ALO is alpha alumina crystal.

The alpha alumina crystals are surrounded by spinel crystals. Further, the α-alumina crystal content can be 60% or more, and the spinel crystal content can be 40% or less.

Particle size 3.3 obtained by slag crushing and sieving
When comparing the porosity and bulk specific gravity of fused alumina of 6 to 1.68 mm with white alumina abrasives of the same grain size, as shown in the table below, the porosity is small and the bulk specific gravity is large, and the abrasives It is excellent as. In addition, the hardness and toughness are equal to or higher than those of white alumina abrasives.

In addition, in the present invention, the particle size ratio (ratio of short axis to long axis, based on microscopic observation) of molten alumina with a particle size of 0.5 to 2.0 mho is as shown in the table below. Many of them are small and are excellent as an abrasive material.

Experiment 1 20 kg of aluminum slag was prepared by mixing aluminum slag produced when melting and refining an aluminum alloy using an active gas method and aluminum slag produced when melting and refining an aluminum alloy using an inert gas method. . The chemical composition (unit weight %, same hereinafter) is as shown in the table below.

Note that the chloride content in the pond is 0.9%.

Pre-dried moisture 8% in 20kg of the above aluminum slag
A blend of 42 Kg was prepared by mixing 22 Kg of stainless steel scale with the following chemical composition containing:

42 kg of the above formulation was loaded into a drying oven preheated to 300°C and held at 100-300°C for 15 minutes. The white smoke generated during that time was captured by a dust collector.

The amount of dust collected by the dust collector was 1.8 kg, and its chemical composition was as shown in the table below.

Therefore, it was confirmed that this dust can be used as 7 lux when melting fertilizer or aluminum alloy scrap.

The compound that was treated in a pollution-free manner in the furnace weighed 38.5 kg, had a moisture content of 0.2%, and metal aluminum at 16%, with no AIN or AlCl detected. was found to be an excellent formulation for producing fused alumina.

Next, 38.5 kg of the above compound was loaded into a three-phase electric furnace (130 KV 8), electrode scraps were placed on the surface of the furnace, and electricity was supplied, causing the compound to melt while undergoing a Chirmitz reaction. do. The temperature of the melt in the furnace is 2100
When 'C was reached, the power supply to the furnace was shut off.

Next, the electrode is raised, the top of the furnace is covered with a heat insulating cover, and the molten material is slowly cooled.

In the product solidified in the furnace, the upper slag and the lower ferroalloy are completely separated. The chemical composition of the produced ferroalloy is as follows.

The chemical composition of the produced slag is shown in the table below.

When the above slag was analyzed by X-ray diffraction, almost all of the M
It chemically combines with either gO or A I20 to form a spinel, and almost all of the remaining A1. O, is an α-alumina crystal. As a result of microscopic observation, spinel crystals were observed surrounding the α-alumina crystals, and impurities were reduced.

The present invention is not limited to the above embodiments, and for example, a blend may be obtained by using previously dried scale and mixing aluminum slag and water with this scale.

Alternatively, the process of the present invention may be carried out using only aluminum slag and water, and then dried scale may be mixed therein.

Blends of aluminum slag and scale treated according to the present invention may be used in the production of molten spinel, alumina cement, and the like.

(Effects of the Invention) As explained above, in the present invention, chlorides such as aluminum nitride and ammonium chloride contained in aluminum slag are reacted with water to finally produce ammonium chloride. Ammonium is collected using a dust collector, and aluminum slag can be processed with almost no pollution, and ammonium chloride, which is useful as fertilizer or 7-lacs, can be obtained. In addition, aluminum i-based is a raw material for producing molten alumina etc. by the thermite reaction, as harmful substances such as aluminum nitride and chlorides are removed without losing much of the metal aluminum required for the thermite reaction with scale. It becomes the most suitable one.

Claims (3)

[Claims] (1) Aluminum nitride and chloride (mainly aluminum chloride, but in some cases MgCl_2 and CaCl_2
By heating a mixture containing aluminum slag containing both chloride and water in a furnace, the aluminum nitride and water react to produce ammonia, and the chloride and water are combined. The reaction produces hydrogen chloride, and finally ammonia and hydrogen chloride are reacted to produce ammonium chloride, and this ammonium chloride is collected by a dust collector, and the aluminum nitride in the above formulation is
A method for treating aluminum slag, characterized in that the contents of chloride and water are adjusted to just the right amount so as to achieve the above reaction. (2) The method for treating aluminum slag according to claim 1, wherein the heating temperature is 100 to 300°C. (3) The aluminum slag is the aluminum slag according to claim 1, which is obtained by blending and preparing at least two of the above-mentioned aluminum nitride-containing material, the above-mentioned chloride-containing material, and both of these materials. processing method.