JP2011230074A - Method of treating wet dust generated in blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To specifically provide a simple, practical and effective method for separating wet dust in gas emissions from a blast furnace for iron manufacturing containing a large amount of carbon (C) into iron (Fe) and carbon (C) to reuse them in iron manufacturing.SOLUTION: A slurry mixture is made from wet dust and ultrasonication is carried out to the slurry. Then wet separation such as wet magnetic separation is applied to the slurry to separate it into a recovered material mainly containing iron and a recovered material mainly containing carbon. The recovered material mainly containing iron can be reused as an iron source for iron manufacturing after dezincification in a reduction furnace.

Description

  The present invention relates to a recycling method for effectively using a product generated in an iron making process again in the iron making process, more specifically, separation of iron (Fe) and carbon (C) in wet dust during dust collection of an iron making blast furnace exhaust gas. It is related with the reuse method in the iron-making process of Fe content.

  The dust collected from the blast furnace exhaust gas includes a coarse primary dust collected by a dry process and a fine secondary dust collected by a wet process.

  Most of the dry dust collection dust is reused as a sintering raw material for the recovery of Fe.

  However, even when wet dust is used as a Fe source in the sintering process, it is fine and therefore has a high moisture content. Even if it is dehydrated, it generally has an adverse effect on the sintering operation. The content of the blast furnace is adversely affected, such as damage to the furnace material in the blast furnace and the promotion of the generation of deposits on the furnace wall.

  The wet dust collected from the blast furnace exhaust gas needs to be subjected to Zn removal treatment, and is often treated in a reduction furnace as shown in FIG.

  In the reduction furnace operation, although carbon is used as a reducing agent, the total amount of carbon charged is within an appropriate range in relation to the reduction reaction, and excessive compounding C causes strength deterioration in the reduced pellets, resulting in quality reduction. Adversely affected.

  However, the blast furnace wet dust contains a large amount of C as shown in Table 1 (cited from the 4th edition of the Steel Handbook) and cannot be used in large quantities as a reducing furnace raw material. Has a problem that it must be destroyed.

  Moreover, in order to avoid the bad influence of Zn to a blast furnace, it may be used by hot metal pretreatment or a steelmaking process. However, since the C content is large, adverse effects such as slag foaming due to the consumption of scouring oxygen and CO gas generated by oxidation are likely to occur, and its use is restricted.

  From this viewpoint, many methods for separating C in blast furnace dust from Fe have been proposed.

  For example, Patent Document 1 proposes a separation method by water separation treatment or magnetic separation in water, and iron oxide bites into heavy iron oxide powder and carbonaceous material that easily settles and precipitates by water separation treatment. It is said that it can be divided into the weight of the oval and the light weight of fine carbonaceous powder, iron oxide fine powder, zinc oxide and tin oxide that float and float. However, this Patent Document 1 discloses the purpose of separation of Fe and C in which Fe is used as a raw material for recycling and C is used as a raw material for activated carbon. There is no description about processing. Further, since the concentration of C contamination on the Fe recovery side is not shown, it is difficult to determine whether or not the technique is effective for the purpose of removing C which becomes an obstacle when using Fe.

  Patent Document 2 discloses a specific gravity beneficiation method using water or the like. Since metal and metal oxides such as Fe, Zn, and Pb contained in secondary dust and carbon and gangue components such as coke powder have different specific gravity, they can be easily separated by specific gravity beneficiation. As a method of specific gravity beneficiation, any method that can separate secondary dust by specific gravity can be used without particular limitation, and can be applied both dry and wet. In addition, a centrifuge may be used to increase the beneficiation rate. In particular, when wet specific gravity beneficiation is adopted, a gravity sedimentation method or a fluid cyclone may be used, but preferably a centrifuge is used. The use of a machine is described. However, only “gravity sedimentation method”, “fluid cyclone”, and “centrifugal separator” are illustrated as specific gravity beneficiation methods, and there are no specific examples of separation conditions and separation results. As described in the literature, if it can be easily separated by gravity sedimentation, a thickener often installed as a wet dust treatment facility for blast furnace dust collection should be able to be sufficiently separated.

  Patent Document 3 and Patent Document 4 disclose wet crushing treatment as necessary and separation of C by flotation. This also uses the difference in density between the Fe-based material and the C-based material after mechanically separating the particles and separating them into fine particles. In any case, it is disclosed that a suspended substance mainly composed of graphite and iron oxide or other substances can be separated into sediments. However, the flotation shown in any of the literature is not possible for the flotation treatment of particles using the density difference unless the particles of Fe-based material and C-based material are sufficiently separated. There is a problem. In addition, there is a problem that the Fe-based material and the C-based material cannot be effectively separated without any particle separation treatment. Furthermore, it is relatively easy to crush large objects, for example, crushing large objects of several centimeters or more into several millimeters, etc. Well known. It is quite difficult to completely separate agglomerated fixed matter composed of particles of several microns to several tens of microns into original particles by a mechanical crushing method. There is a problem that appropriate equipment needs to be selected and the operation load is large.

  Further, Patent Document 5 discloses a method of contact levitation separation using an organic solvent. The carbon content in the dust is high in graphite and has the property of selectively adsorbing organic matter like activated carbon. Therefore, the carbon content is lighter than water and less soluble in water, so it is dispersed in water and has a floating effect. It has been disclosed that it floats and collects by contact adsorption with a certain organic substance and leaving it to stand. However, the contact flotation method using an organic solvent requires safety and hygiene measures and environmental measures for using an organic solvent, and has many restrictions on facilities and operations. In addition, if the blast furnace gas ash contains easily soluble components and impurities in the organic solvent, it is extracted and accumulated in the organic solvent, which makes it difficult to use the organic solvent repeatedly and increases the cost. is there.

  Furthermore, Patent Document 6 discloses that for the purpose of separating Fe and Zn, elemental separation of the blast furnace gas ash is performed by performing a dispersing agent and ultrasonic treatment and performing sedimentation / floating separation by standing, The table showing the results of the example also describes the behavior of C. However, in the disclosure in this document, it is noted that a pretreatment such as a dispersing agent and ultrasonic treatment is used in combination to promote component separation, but in the calm / specific gravity separation, separation of Fe and Zn. Although it is good, there is no effect on the separation of Fe and C.

JP-A-48-52694 JP 2004-105801 A JP-A-53-88601 Japanese Patent Laid-Open No. 55-14864 JP-A-53-23896 Japanese Patent Laid-Open No. 52-2807

  An object of the present invention is to provide a simple, practical and effective method for separating iron (Fe) from carbon (C) in order to reuse iron (Fe) in a steelmaking process with respect to wet dust of blast furnace exhaust gas.

  The method of treating wet dust in the blast furnace product that separates the iron-based material and the carbon-based material of the present invention is collected when the exhaust gas generated from the blast furnace for iron making is wet-collected. The wet dust is made into a slurry, and the wet wet dust is subjected to ultrasonic treatment, and then wet separation is performed using the difference in physical properties between the particles mainly composed of iron and the particles composed mainly of carbon. Is the basic configuration.

According to the present invention, the C content contained in a large amount in the blast furnace wet dust is separated from the portion mainly composed of Fe. As a result, it is possible to reduce the amount of blast furnace wet dust used due to the total carbon limit when charging the main part of Fe into the reduction furnace for dezincing, and the amount of blast furnace wet dust that can be reused as an iron source Can be increased. In other words, it has the effect of reducing the amount of blast furnace wet dust that cannot be used and is discarded.

FIG. 3 is a flow diagram illustrating the process of the present invention. It is a flowchart which shows an example of the process of a conventional method. The relationship between the presence / absence of ultrasonic treatment and the treatment conditions and the C content (%) / Fe content (%) of the magnetized side slurry is shown. The relationship between the presence / absence of ultrasonic treatment and the treatment conditions and the C distribution ratio (%) to the magnetized side slurry is shown.

  Referring to FIG. 1, the conditions in each process of the present invention are as follows.

Slurry conditions Since the dust generated in the blast furnace is collected in a wet venturi and is in the form of a thin slurry immediately after being collected, it is usually dehydrated by a dehydrator after sedimentation and concentration with a thickener so that it can be easily handled.

  In order to apply the present invention, the wet dust needs to be in a slurry state, and as a method therefor, the slurry collected by a wet venturi may be used as it is, or a slurry that is precipitated and concentrated by a thickener may be used. A slurry concentrated or diluted by any method based on these slurries may be used.

  Furthermore, for convenience of transportation and storage, water may be added to the blast furnace wet dust that has been dewatered by a dehydrator and turned into sludge to form a slurry.

  In the present invention, although not essential, it is more preferable to maintain the pH of the slurry at about 8.5 to 10. This is because, compared with other pH values, in this pH range, there is less elution of metal elements such as Fe and Zn into the liquid, and the drainage treatment after the final solid-liquid separation is easy.

Conditions for ultrasonic treatment The slurry is treated by irradiating ultrasonic waves. The purpose and function of the ultrasonic irradiation is to microscopically separate various types of particles such as Fe-based bodies and C-based bodies that are physically attached to each other. Here, micro means the separation of particles suspended in a slurry. That is, the individual particles are separated as much as possible before carrying out any macro wet separation for separating the slurry or sludge containing a large amount of Fe into the slurry or sludge containing a large amount of C in the next step.

The ultrasonic treatment is sufficient if the slurry can be substantially irradiated with ultrasonic waves. For example, the ultrasonic intensity of 1kW per slurry 1 m ³ at 2-3 minutes of ultrasonic irradiation, the separation of Fe and C becomes good as compared with the case without ultrasonic irradiation.

  The frequency of the ultrasonic wave to be irradiated is not particularly limited, but a relatively low frequency of about 100 kHz or less is more preferable.

The ultrasonic irradiation may be performed in either a batch type container or a continuous flow path.
In both batch processing and continuous processing, sufficient slurry agitation is required by some method. This is because it is impossible to make the slurry uniform and, consequently, uniform ultrasonic irradiation only by the ultrasonic excitation force.

  The slurry concentration at the time of ultrasonic irradiation, that is, the ratio of solid substance amount / total mass is not particularly limited. The lower the concentration, the lower the treatment efficiency and the larger the equipment scale for the same wet dust treatment amount, which is economically disadvantageous. Moreover, if it becomes high concentration, processing efficiency will improve, but processing, such as stirring and transfer, will become difficult. Although the effect can be obtained at any slurry concentration, it can be said that the range of about 3 to 25% by mass is a preferable range from these viewpoints.

In particular, ultrasonic treatment conditions, the ultrasonic intensity displayed in kW per slurry 1 m ^3, sonication parameter represented by the product of the ultrasonic irradiation time is displayed in minutes is less than 20kW · min / m ³ As the value of this ultrasonic treatment parameter increases, the C / Fe ratio on the Fe recovery side is greatly reduced. However, when the value is 20-30 kW · min / m ³ or more, the degree of decrease in the C / Fe ratio is Decrease.

This is because, in the region where the value of the sonication parameter is less than 20 kW · min / m ³ , micro separation of Fe-based particles and C-based particles by sonication is still insufficient, and as sonication increases. It shows that the separation is progressing rapidly. On the other hand, when it is 20 to 30 kW · min / m ³ or more, the separation proceeds with an increase in the ultrasonic treatment, but the degree thereof is small.

For this reason, considering the efficiency balance between the equipment cost and the effect, it can be said that it is particularly preferable to satisfy the condition that the value of the ultrasonic treatment parameter is 20 kW · min / m ³ or more industrially.

Moreover, the combination of ultrasonic intensity and irradiation time is not particularly limited. As shown in the Examples, as long as satisfying the 20kW · min / ^{m 3} or more, the case of performing long-time irradiation of low intensity, such as 4 kW / ^{m 3,} a high strength, such as 35 kW / ^{m 3} There is no clear difference between long-time irradiation and any combination can be selected.

Wet separation conditions The method of wet separation after ultrasonic treatment shown in FIG. 1 is not particularly limited. Any method that can be macroscopically separated into slurry or sludge with a high Fe content and slurry or sludge with a high C content, such as wet magnetic separation, flotation, centrifugation, chemical extraction, etc. But it can be applied. Any conditions may be used as long as they can be separated industrially.

  Among the wet separation methods, the wet magnetic separation method is particularly suitable. The reason for this is that the structure of the equipment used is simpler and the installation costs and maintenance / maintenance costs are lower than those of a centrifugal method such as a decanter. In addition to the establishment of treatment facilities, the flotation method and chemical extraction process require the use of appropriate chemicals during operation, resulting in cost and environmental management burdens. There is no use. Therefore, it can be said that the wet magnetic separation method is particularly excellent among the wet separation methods.

  Also, among the wet magnetic separation methods, drum-type wet magnetic separation, filter-type wet magnetic separation, and the like can be applied, and specific methods of wet magnetic separation and conditions such as magnetic flux density are not specified.

Reuse of the separated material Ultrasonic irradiation and wet separation methods more than the separation of the slurry or sludge rich in Fe is more concentrated in Fe compared to blast furnace wet dust before treatment. It can be used as an Fe source. Specific usage destinations such as a sintering process, a blast furnace process, and a steel making process are not necessarily limited.

However, since the slurry or sludge still contains a large amount of Zn, in order to use a large amount of the slurry or sludge, it is particularly preferable to perform after the removal of Zn in the reduction furnace.

  Moreover, when the blast furnace wet dust is used as the Fe source in the iron making process after the Zn removal treatment in the reduction furnace, it is not always necessary to apply the ultrasonic irradiation and wet separation method according to the present invention to the total amount of dust. Instead, a part of the dust may be treated in accordance with the total amount of carbon charged in the reduction furnace.

  In other words, the C / Fe ratio of wet dust as recovered is about 0.7 to 0.8, but the C / Fe ratio of slurry or sludge containing a large amount of Fe separated by applying the method of the present invention is 0. .15 to 0.2, and the C content ratio is about 1/4 to 1/5 before the treatment.

  That is, when it is desired to halve the amount of charged C from dust, it is sufficient to process about 60% of the total amount of dust. On the other hand, the treatment method of the present invention can be applied to the entire amount to perform an operation with a C / Fe ratio of 0.3 to 0.4. However, the present invention is applied to only a part of the charged amount. The treatment method with a / Fe ratio of about 0.15 to 0.2 is preferable because the cost of depreciation of the equipment, the cost of processing, etc. becomes low.

Example 1
The blast furnace wet dust having the composition shown in Table 2 was subjected to ultrasonic treatment and wet magnetic separation by the process shown in FIG.

  The slurry containing blast furnace wet dust having the composition shown in Table 2 was a concentrated slurry extracted from the thickener, and its mass concentration was 12%. The pH was adjusted to about 9.5.

  This was processed under the level of ultrasonic intensity and irradiation time shown in Table 3. As a comparison, a level in which only wet magnetic separation was performed without performing ultrasonic treatment was also provided.

  In the ultrasonic treatment, slurry was stored in a storage tank, and ultrasonic irradiation was performed for a predetermined time and with a predetermined intensity while impeller stirring. Wet magnetic separation was performed with a drum type magnetic separator having a surface magnetic flux density of 0.24 Tesla. The magnetized-side slurry and the non-magnetized-side slurry were each sampled and analyzed on the magnetic separator output side.

  Table 3 also shows the Fe analysis value and C analysis value of the magnetized side slurry, and the ratio of C distribution to the magnetized side slurry with respect to the total amount of input C. These are shown in FIG. 3 and FIG.

  From these figures, the following can be said and the effect of the method of the present invention can be clearly understood.

B) Separation of Fe and C is improved by performing wet magnetic separation after ultrasonic treatment as compared with the comparative method without ultrasonic treatment (No. 1 in Table 3).
(B) When the ultrasonic treatment condition is 20 kW · min / m ³ or more, the cost for improving the effect is reduced. Therefore, a condition range of 20 kW · min / m ³ or more is a particularly preferable range as compared with conditions less than that.

Example 2
Due to the restriction of the total amount of C charged in the reduction furnace, only about 12 tons, which is half of the blast furnace wet dust generation amount of 24 tons, can be processed. 60% of the generated amount was treated by the method of the present invention, and the remaining 40% was charged as it was into the reduction furnace.

  Table 4 shows the mass balance measurement results. Almost all of the wet dust can be used with the carbon charged in the reduction furnace in the same manner as in the comparative method (uses half of the generated amount without treatment), and as a result, the effect of increasing the amount of recycled Fe was obtained.

Claims (5)

The wet dust collected when the exhaust gas generated from the blast furnace for steelmaking is wet collected is made into a slurry,
After performing ultrasonic treatment on the slurry-like wet dust, by performing wet separation using the difference in physical properties of particles mainly composed of iron and particles mainly composed of carbon,
A method for treating wet dust in blast furnace products that separates into iron-based materials and carbon-based materials. The sonication is
2. The blast furnace generation according to claim 1, wherein an ultrasonic treatment parameter represented by a product of ultrasonic intensity expressed in kW per 1 m ^{3 of} slurry and ultrasonic irradiation time expressed in minutes is 20 kW · min / m ³ or more. A method for treating wet dust in objects.   The method for treating wet dust in a blast furnace product according to claim 1, wherein the wet separation utilizing a difference in physical properties between the iron-based particles and the carbon-based particles is a wet magnetic separation method.   A material mainly comprising iron after separation by wet separation utilizing a difference in physical properties between the particles mainly composed of iron and the particles mainly composed of carbon is used as a raw material of a reduction furnace for dezincing. The processing method of the wet dust in the blast furnace product in any one of 1-3. When using wet dust collected when the exhaust gas generated from the blast furnace for iron making is collected as a raw material for the reduction furnace,
A method for treating wet dust in a blast furnace product, wherein a part of the wet dust is used after the treatment according to any one of claims 1 to 3 is used, and the remainder of the wet dust is used without being treated.

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