JP2003328045A - PROCESS FOR TREATING Ca-CONTAINING DUST - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment process which can solve problems accompanying thermal reduction of high-Ca dust containing valuable metals for recovering the valuable metals, such as erosion of a furnace bottom refractory and decrease in rate of reduction caused by the high Ca-content and reduction in recovery rate of the valuable metals accompanying these. <P>SOLUTION: When thermally reducing the dust containing metal components and ≥15 mass% Ca component calculated in terms of CaO (based on dry weight), a Ca-diluting material is added to the dust to adjust the Ca content calculated in terms of CaO to ≤14 mass% before performing thermal reduction. This inhibits erosion of the furnace bottom refractory caused by slag leaching and enables efficient thermal reduction. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a dust containing metal components such as iron, nickel, and chromium (including pickling sludge) generated in an iron manufacturing plant, etc. The present invention relates to a treatment method improved so as to efficiently recover as a valuable component.

[0002]

2. Description of the Related Art As one of the methods for reducing dust containing a metal component such as iron, nickel and chromium and recovering the metal component as a valuable resource, a method of heating and reducing it using a rotary kiln is known. (Japanese Patent Publication Sho 51-1308
No. 3, gazette 55-21810, etc.). Further, Japanese Patent Application Laid-Open No. 11-241125 discloses a method of using a rotary hearth furnace as an improved method capable of continuously and efficiently performing the thermal reduction of metal components.

In an iron factory, etc., the pickling waste liquid discharged from the pickling process such as steel plate and plated steel plate is neutralized with an alkali agent to make it harmless. Is an inexpensive CaO, Ca (O) capable of recovering a neutralized product as a water-insoluble salt.
H) ₂ is commonly used. Therefore, in the neutralization sludge of the pickling waste liquid, Ca components are CaSO ₃ , CaSO ₄ , CaCO together with metallic components such as Fe, nickel and chromium.
₃ , Ca ₃ (PO ₄ ) ₂ , CaF ₂ , CaCl ₂ , CaO, C
It is contained in a large amount in the form of a (OH) ₂ . for that reason,
There are some reports on a method for recovering the metal component from the neutralized sludge.

For example, in JP-A-51-28515, 1) neutralized sludge of pickling waste liquid is dehydrated and dried to obtain a water content of 2
To about 15% by mass, 2) this is mixed with dry iron-making dust, scale, etc., 3) 1 to 5% by mass of an organic binder and about 5% by mass of an inorganic binder are added thereto. After that, water is added to adjust the water content to 6 to 14% by mass and then kneaded, and 4) the kneaded product is processed into a briquette and then dried, and the method is effectively used as a raw material for a ferroalloy of an electric furnace. Has been done.

However, the neutralized sludge is a mud-like substance in which fine granular insoluble matter is mixed, and it is extremely difficult to dry in the sun, and even if it is forcedly dried using a drying furnace or the like, the efficiency is very poor. In addition, if, for example, blast furnace wet dust is blended as a carbon source, the drying becomes more difficult and inefficient, and the equipment cost and maintenance cost required for recovery may exceed the profit due to recovery as a valuable resource. .

Further, in Japanese Patent Laid-Open No. 2001-40429, as a relatively new technique, a neutralizing sludge of pickling waste liquid is blended with a carbonaceous reducing agent to be formed into pellets or briquettes, which are formed into 1000 to 1100. A method of reducing oxides (or hydroxides) such as Fe, nickel, and chromium contained in the sludge by heating the sludge for about 5 minutes or more and recovering the reduced metal is disclosed. There is.

Since this method is a method of performing heat reduction at a low temperature of about 1000 to 1100 ° C., the low melting point compound (molten slag) that significantly melts the hearth refractory in the heat reduction step does not leak out, It has an advantage that the life of the heating reduction furnace can be maintained for a long period of time. However, the biggest difficulty pointed out in this method is that the reduction rate is slow because the heating reduction temperature is low, and the reduction efficiency is poor. Moreover, in order to increase the recovery rate of the reduced metal (recovered product) to the actual operation level, it is necessary to lengthen the heating and reduction time,
Since a long heating reduction furnace is required for continuity,
Equipment costs will also soar.

As described above, several methods are known for recovering valuable metals by heating and reducing the neutralized sludge of the pickling waste liquid, but there are many problems in recovery efficiency and equipment. Very few have been put to practical use on an industrial scale, and most iron-making dust, including the neutralized sludge, is thrown into landfills as industrial waste.

The neutralization sludge of the pickling waste liquid is described above.
For a reason as described above, a large amount of CaO or its hydrate is used.
Ca (OH)₂And CaSO₃, CaSO_Four, CaCO₃，
Ca ₃(PO_Four)₂, CaF₂, CaCl₂C in the form
a component is contained, and the Ca component is low in the heat reduction step.
A slag with a melting point is formed and added by the molten slag
Pyrolysis furnace Refractory material meltdown and valuable metal reduction effect
The CaO content in the sludge should be adjusted to reduce the rate.
It is considered extremely important to control it carefully.

However, including the above-mentioned publicly known documents, when the neutralized sludge is heated and reduced to recover the valuable metal, attention is paid to the CaO content in the sludge and the reduction efficiency and recovery rate of the valuable metal component. There has been no research aimed at increasing

[0011]

Under the above circumstances, the present invention is intended to provide a large amount of CaO, CaSO ₃ , CaSO ₄ , CaCO ₃ , C as found in neutralization sludge of pickling waste liquid.
a ₃ (PO ₄₎ when recovering valuable metal by heating and reducing a dust containing _2, CaF _2, Ca component such as _{CaCl 2, Ca (OH) 2} , focus on problems caused by the large amount containing the Ca component Have advanced research. When the Ca-rich dust is heated and reduced at a high temperature of about 1100 ° C. or higher,
It was confirmed that the low-melting-point slag with a high CaO content was exuded, the hearth refractory of the heating reduction furnace was significantly melted, and the reduction reaction of valuable metal components was hindered.

On the other hand, if the heating reduction temperature is suppressed to the level of 1100 ° C. or lower, the above problems due to the leaching of the low melting point slag can be avoided, but the reduction efficiency is lowered, and the heating reduction takes a long time and is satisfactory. The recovery rate of valuable metals cannot be obtained either. In addition, if the heating reduction temperature is lowered,
The crushing strength of the reduced metal obtained by heating and reduction is also poor, and the handleability as a recovered metal is poor.

The present invention has been made in view of such circumstances, and its purpose is to have a high Ca content such as neutralized sludge of pickling waste liquid, and specifically, to convert it to CaO.
When the valuable metal-containing dust having an a content of 15% by mass or more is heated and reduced to recover the valuable metal as a resource, the above-mentioned problems caused by the high Ca content, particularly melting loss of the hearth refractory of the heating and reduction furnace and Another object of the present invention is to provide a treatment method capable of solving all of the problems such as reduction in reduction efficiency and reduction in recovery rate of valuable metals.

[0014]

The method for treating Ca-containing dust according to the present invention which has been able to solve the above-mentioned problems is C
A method of heating and reducing metal component-containing dust containing 15% by mass or more of Ca component on a dry basis of aO conversion,
The gist resides in that a Ca diluent is added to the dust to adjust the Ca content in terms of CaO to 14% by mass or less and then the material is heated and reduced.

By adopting this treatment method, even if the heating / reduction temperature is raised to 1100 ° C. or higher, the problem as pointed out in the prior art does not occur, and the valuable metal component can be efficiently recovered as a reduced metal. it can. However, if the heating / reduction temperature is too high, melting loss of the hearth refractory due to the slag leaking out is unavoidable.
It is desirable to keep the temperature below about ° C.

Further, in carrying out the present invention, a carbonaceous reducing agent is blended in order to reduce the valuable metal component, and the blending amount of the carbonaceous reducing agent is equivalent to free C which contributes to the reduction. Valuable metal by controlling the amount of reducing metal oxides (oxides of iron, nickel, chromium, lead, zinc, etc.) contained in dust to -2% or more and + 1% or less with respect to the theoretical amount of C required for reduction. It is preferable because the heat reduction of the components can be efficiently advanced without waste, and the crushing strength of the produced metal components can be increased. However, this does not apply if a particularly high metallization rate is not required, such as when used for blast furnace applications.

The dust used in the present invention can be used without any particular limitation as long as it contains a large amount of valuable metal components in addition to the Ca component, such as the neutralization sludge of the pickling waste liquid described above. It is useful as a method for recovering a reduced metal mainly composed of metallic iron from dust containing at least one of iron, nickel, and chromium, and particularly a large amount of Fe.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, according to the present invention, metal component-containing dust containing a large amount of Ca component of 15% by mass or more in terms of CaO (dry basis: hereinafter the same), such as neutralized sludge of pickling waste liquid. The present invention provides a heating reduction treatment method of the above, which is characterized in that by adding a Ca diluent to the dust,
The content of CaO in terms of CaO is adjusted to 14% by mass or less, and then the material is heated and reduced. Incidentally, CaO contained in the metal component-containing dust is combined with slag-forming components such as SiO ₂ and Al ₂ O ₃ contained in the dust in the heat reduction step of the metal component to form slag. When the content is high, the content of CaO in the slag is also high and a slag having a relatively low melting point is formed. Therefore, the low-melting slag becomes molten slag in a relatively low temperature range in the heating and reducing step of the metal component, and is drained out, which significantly melts the hearth refractory material. Therefore, in order to suppress the melting loss of the hearth refractory, the heat reduction must be carried out in a low temperature range, the reduction efficiency for the metal component becomes insufficient, and the recovery rate of the metal component cannot be sufficiently increased. Such a tendency is remarkably exhibited when the Ca content in terms of CaO in the raw material dust is 15% by mass or more.

Therefore, in the present invention, such a large amount of CaO is used.
When the metal component in the dust containing is heated and reduced, by adding a Ca diluent to the dust, the Ca content in terms of CaO is 14% by mass or less, more preferably 10% by mass.
After reduction to below, heat reduction is performed. Then, the CaO content in the slag produced in the heating reduction step also decreases, and the melting point of the produced slag rises accordingly. As a result, melting and exudation of the generated slag do not occur in the temperature range around 1100 ° C, as well as in the temperature range around 1000 ° C, which is the generally used heat reduction temperature, and the melting damage of the hearth refractory is prevented. it can. Moreover, the heating reduction temperature is set to, for example, 110.
Since the temperature can be set higher than about 0 ° C., the heat reduction efficiency of the metal component is improved and the recovery rate of the metal component can be increased.

However, if the heating reduction temperature is too high, Ca
Despite the reduction of O content, there is a concern of melting of the hearth refractory due to the exudation of the generated slag.
It is desirable to keep it below a certain level.

Further, in carrying out the present invention, a carbonaceous reducing agent is blended in order to reduce the valuable metal component, and the blending amount of the carbonaceous reducing agent is calculated in terms of free C which contributes to the reduction. It is desirable that the amount is adjusted to be −2% or more and + 1% or less, and more preferably −1.7 to 0% with respect to the theoretical amount of C required to reduce the reducing metal oxide contained in the dust. By the way, if the amount of the carbonaceous reducing agent blended is less than -2% with respect to the theoretical amount, the reduction efficiency of the metal component tends to be insufficient due to insufficient C content. On the other hand, if the C content exceeds + 1% and becomes excessive, the residual C hinders the binding of metallic iron, and the slag is also less likely to soften, resulting in a weak binding force. The handling becomes poor. Therefore, the blending amount of the carbonaceous reducing agent is preferably within a range of -2% or more and 1% or less with respect to the theoretical amount required for reducing the metal component contained in the raw material dust. However, this does not apply to cases where a particularly high metallization rate is not required, such as when used in applications for blast furnaces.

As the dust used in the present invention, as described above, a large amount of Ca such as neutralization sludge of pickling waste liquid is used.
It can be used without particular limitation as long as it contains a valuable metal component together with the components, in addition to neutralization sludge, electric furnace dust,
Converter dust, hot metal pretreatment dust (especially dust produced when a large amount of lime is used to improve desulfurization, etc.), as well as road cleaning sludge, such as iron, nickel as metal components,
Various dusts containing at least one of chromium can be used. Among them, various dusts containing a large amount of Fe component discharged from iron and steel manufacturing plants, and Fe-containing sludge discharged from hot rolling plants are useful raw materials and valuable as waste raw materials with a high content of valuable metal components. It can be effectively used for metal recovery.

As the Ca diluent, CaO itself is used.
Various materials with low content, such as iron ore, can be used, but preferred are blast furnace wet dust, lagoon sludge, electric furnace dust, converter dust, converter sludge, which are themselves required to be effectively used as waste materials. Mill scale, mill sludge, iron ore pellet powder, sinter dust, cupola dust, DRI powder, and the like can be used alone, and if necessary, two or more kinds can be appropriately used in combination.

As the carbonaceous reducing agent, coal, coke breeze, CDQ powder, municipal solid waste carbide, etc. can be used. Further, since blast furnace wet dust, lagoon sludge, and the like contain a considerable amount of C together with the Fe component, they can be effectively utilized as raw material dust that also serves as a carbon source and a Ca diluent.

In carrying out the present invention, the above-mentioned valuable metal-containing dust, Ca diluent and carbonaceous reducing agent are blended so as to have predetermined CaO content and C content,
If necessary, add an organic or inorganic binder,
Preferably, it is preliminarily shaped into pellets or briquettes and then pre-dried, or while it is in powder form, it may be subjected to heat reduction in any heating reduction furnace such as a rotary kiln or a rotary hearth furnace according to a conventional method. While suppressing the melting damage of the rotary kiln inner wall and the hearth refractory material due to the leaching of slag as much as possible, the metal component can be efficiently recovered as a reduced metal with a high level of reduction efficiency.

The heat reduction temperature at this time is 1100 to 135 in order to secure higher reduction efficiency and metallization rate while suppressing melting loss of the refractory due to slag creeping out as described above.
It is desirable to carry out in the range of 0 ° C. If, for example, neutralized sludge of pickling waste liquid discharged from a hot dip galvanizing plant is used as a raw material, a considerable amount of Zn component is mixed in the neutralized sludge, and this reduced iron is recovered. May be mixed in. However, according to the present invention, as a side effect of being able to set the heating reduction temperature higher as described above, metal zinc, which has a relatively low volatilization temperature, is volatilized and removed in the heating reduction step, so the recovered reduced metal is recovered. The content of different metals such as Zn contained therein which is unfavorable to be mixed when used as an iron source is also reduced, which is preferable.

[0027]

EXAMPLES Hereinafter, the embodiments of the present invention will be described in detail with reference to specific examples. However, the present invention is not limited to the following examples, and conforms to the gist of the preceding and the following. It is also possible to carry out appropriate modifications within the range to be obtained, and all of them are included in the technical scope of the present invention.

Example First, as a raw material waste material, a reduction experiment was conducted in a steel material pickling line using neutralized sludge obtained by using CaO / Ca (OH) ₂ as an alkali neutralizing agent of the pickling waste solution. . Wet blast furnace dust was used as a carbon source for reduction, and lagoon sludge and mill scale were used for component adjustment. The composition of each component is as shown in Table 1 below.

[0029]

[Table 1]

First, the Ca content in terms of CaO is 15% by mass.
The above-mentioned neutralized sludge as the above dust, Ca
Wet blast furnace dust, lagoon sludge, and mill scale were used as diluents. Further, since the blast furnace wet dust contains a considerable amount of carbon, it was also used as a carbon source. Also,
Slaked lime was added as a part of the binder in a 1 mass% exterior.

86 parts by mass (solid content) of neutralized sludge and 14 parts by mass of blast furnace dust were pre-mixed and pre-dried by a rotary dryer until the water content became 13 mass%, then mixed and kneaded to make a size 6 cc briquette. It was molded into a shape. The content of CaO in the solid content of the briquette is 1
The total C content is 9.3% by mass, the total C content is 8.2% by mass, and the free C content is 4.9%. Then, when the product further dried to reduce the water content to 1.0 mass% was subjected to heat reduction using a rotary hearth furnace at 1300 ° C., low melting point slag was exuded. Also, the heating temperature is 12
When the temperature was lowered to 50 ° C. and further to 1200 ° C. and the same heat reduction was carried out, the slag leaked out similarly. When the heating reduction temperature was lowered to 1100 ° C, the slag did not leak out, but the metallization rate and dezincification rate of iron were low, and the metallization of iron at a residence time of 9 minutes and 12 seconds was low. The rate was 30.6% and the dezincification rate was only 32.9%.

Therefore, by changing the blending ratio of the raw materials shown in Table 1 above as shown in Table 2 below, the CaO content in the blended raw materials can be changed and the blending amount of the carbon source can be adjusted. Adjusting the C content for metal components,
A similar dry briquette was made. Regarding the C content, the surplus C amount shown as the following formula (1) surplus C amount (mass%) = free C (mass%) contributing to the reduction reaction- (oxygen amount in the reducing metal oxide in the briquette (Mass%)) × 12/16 ... (1) was adjusted. The reducing metal oxides mean oxides of iron, nickel, chromium, zinc, lead, etc., and each briquette obtained, which does not contain alumina, silica, magnesia, etc. Was heated and reduced at 1250 ° C. to examine whether or not the low melting point slag was leaked out, and the Fe metallization ratio and dezincification ratio, and further the crush strength of the reduced metal were measured, and the results shown in Table 3 were obtained.

[0033]

[Table 2]

[0034]

[Table 3]

Based on the results shown in Tables 2 and 3, FIG. 1 shows the effects of CaO content and surplus C content of raw material briquettes on the exudation of low melting point slag during heat reduction. It is a graph. As is clear from this figure, when the CaO content is about 10 mass% or less, the slag is not exuded regardless of the amount of surplus C. Further, if the CaO content is 14 mass% or less, the slag can be suppressed from leaking out to a very small amount, and sludge can be smoothly treated.

Similarly, based on the experimental results shown in Tables 2 and 3, FIG. 2 summarizes the effects of CaO content and surplus C content on the slag creeping out and the crush strength of the reduced iron obtained. It is the graph shown. As is clear from this figure, when the excess C exceeds + 1%, the crushing strength of reduced iron tends to decrease, and when the excess C falls below -2%, the metallization rate tends to decrease. ing.

As is clear from the above Tables 2 and 3 and FIGS. 1 and 2, if the CaO content is adjusted to 14% or less and the heat reduction is carried out, the slag will be removed even if the heating temperature is raised to 1250 ° C. It can be seen that no heat generation occurs, and that the heat reduction can be smoothly performed without causing melting loss of the hearth refractory material. Further, when the C content in the raw material is less than -2% with respect to the theoretical amount required for the reduction of the metal component, the metallization rate will be slightly insufficient and the reduction efficiency will be low. On the other hand, if the C content exceeds + 1% and the C content becomes too high, the crush strength of the obtained reduced iron becomes poor. However, for the purpose of "preventing melting damage of the hearth refractory by preventing slag from leaking out", which is the greatest problem of the present invention, it has been found that the purpose can be sufficiently achieved by suppressing the CaO content to 14% or less. It

[0038]

The present invention is configured as described above,
When recovering valuable metals by heating and reducing dust having a large CaO content such as neutralized sludge of pickling waste liquid, C is added to the dust.
a By adjusting the CaO content to 14% or less by blending a diluent, the slag can be suppressed from exuding as much as possible without reducing the reduction efficiency during heating reduction, and the hearth of the heating reduction furnace is reduced. The melting loss of the refractory can be suppressed as much as possible. In addition, if the excess C amount is adjusted within the range of -2% to + 1% with respect to the theoretical amount required for the reduction of the metal component in the raw material preparation stage, the crushing strength can be ensured while ensuring a high level of reduction efficiency and metallization rate. It is possible to efficiently obtain a reduced metal that is strong and easy to handle.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of CaO content in dust subjected to heat reduction on slag creeping out.

FIG. 2 is a graph showing the influence of CaO content and surplus C content in the dust subjected to heat reduction on the crush strength of the heat reduced product.

Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C22B 34/32 C22B 34/32 (72) Inventor Kazuhiko Tate 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Steel Tube Stocks In-house (72) Inventor Tatsuro Ariyama 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Toshihiko Okada 1-2 1-2 Marunouchi, Chiyoda-ku, Tokyo Nihonkansen Co., Ltd. (72) Inventor Hiroshi Sugitu 4-3, Bingo-cho, Chuo-ku, Osaka City Kobe Steel, Ltd. Osaka Branch Office (72) Inventor Hidetoshi Tanaka 4- 1-3, Bingo-cho, Chuo-ku, Osaka Kobe Steel Works Osaka Branch (72) Inventor Takao Harada 4-3 Bingocho, Chuo-ku, Osaka City Kobe Steel Works Osaka Branch (72) Inventor Hiroshi Tamazawa 4-1-1 Bingocho, Chuo-ku, Osaka No. 3 F-term of Kobe Steel, Ltd. Osaka branch office (reference) 4D059 AA11 AA13 BK30 CC07 DA51 DA57 DA58 EB01 EB06 4K001 AA08 AA10 AA19 BA14 BA15 BA24 CA09 CA19 CA21 CA23 GA07 KA06 4K012 DE03 DE06

Claims (4)

[Claims] 1. A method of heat-reducing a metal component-containing dust containing 15% by mass or more of Ca component on a dry weight basis in terms of CaO, wherein a Ca diluent is added to the dust.
A method for treating Ca-containing dust, which comprises reducing the Ca content in terms of O to 14% by mass or less and then reducing the content by heating. 2. The heating reduction is performed at 1100 ° C. or higher for 135
The processing method according to claim 1, which is performed at a temperature of 0 ° C. or lower. 3. The processing method according to claim 1, wherein the dust contains at least one of iron, nickel and chromium as a metal component. 4. The processing method according to claim 3, wherein the dust is neutralized sludge discharged from a steelmaking plant.