KR100514775B1 - Method for producing dephosphorization agent and iron oxide pigment using electrostatic precipitator dust obtained from oxygen converter - Google Patents

Abstract

Disclosed is a method of manufacturing a high efficiency molten iron dephosphorant and iron oxide pigment by forcibly oxidizing electrostatic dust, which is a waste generated in a steel mill plant converter. The method of manufacturing a molten iron dephosphorizing agent includes the step of forcibly oxidizing the electrostatic precipitating dust generated in the converter (轉爐); And adding quicklime and fluorspar to the forced oxidized electrostatic dust. The step of forcibly oxidizing the electrostatic precipitating dust may be carried out by heating the electrostatic precipitating dust in an air or oxygen atmosphere and the temperature of 200 to 600 ℃ for 10 seconds to 60 minutes, the addition amount of quicklime is the total dephosphor composition It is preferably 15 to 40% by weight, and the amount of the fluorspar is 5 to 15% by weight based on the total dephosphor composition. In addition, the iron oxide pigment may be prepared by classifying the forced oxidized electrostatic dust.

Description

Method for producing dephosphorization agent and iron oxide pigment using electrostatic precipitator dust obtained from oxygen converter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high efficiency molten iron dephosphorizer and a method for producing iron oxide pigments, and more particularly, to electrostatic precipitator dust, "converter dry dust", which is a waste generated from a steel mill plant converter. And a method for producing a high efficiency molten iron dephosphorant and iron oxide pigment by forced oxidation.

A converter in an ironworks steel plant is a furnace for supplying oxygen to oxidize and remove impurities such as carbon and silicon from molten iron, and operates at a high temperature of 1600 ° C or higher. It is connected to a dust collector for treating exhaust gas. The dust collector is composed of a dry electrostatic precipitator, and functions to cool exhaust gas and to collect dust discharged together with the exhaust gas. The dust collecting dust collected by the secondary dust collector of the dust collector has a particle size of 210 μm or less, the content of particles having a particle size of 30 μm or less is about 80% by weight, and the main component is 62 to 70% by weight of electric train (Total). Fe, 66.6 wt% on average in 2002) and 4-10 wt% quicklime (CaO, 7.4 wt% on average in 2002), and other oxides (SiO ₂ , MgO, MnO, Al ₂ O ₃ , P ₂ O ₅ And the like). The iron component is present in the range of 16 to 33% by weight of metal iron (Metal Fe), 38 to 49% by weight of iron oxide (FeO), 10 to 22% by weight of ferric oxide (Fe ₂ O ₃ ), black It is near blackish brown, ferromagnetic and usually has a temperature of 40 to 110 ° C. Since ferric oxide (Fe ₂ O ₃ ) contained in the dust collecting dust can be used as an oxidizing agent, it is used as a dephosphorizing agent (용) for molten iron by mixing with quicklime and fluorspar, such technology is disclosed in Republic of Korea Patent Publication No. 1995 -18502.

The molten iron from the blast furnace contains a large amount of various impurity elements, especially phosphorus (P) of 0.08% by weight or more.The molten phosphorus in the molten iron not only causes serious defects in casting of the final product, It should be removed as much as it may cause deterioration of mechanical properties of the product. Since the 80's, a pretreatment plant has been introduced in which dephosphorization, desulfurization and the like are treated before the converter plant to effectively remove phosphorus and sulfur, which are harmful elements in molten iron. In this dephosphorization process, phosphorus (P) dissolved in the molten iron is oxidized to a phosphate form by the dephosphorization agent (see Scheme 1 below), and the resulting phosphate is calcined (CaO) in slag suspended above the molten iron. After stabilization (see Schemes 2 and 3 below), the slag is removed and discharged from the molten iron by using a skimmer.

P ₂ O ₅

3CaOP ₂ O ₅

4CaOP ₂ O ₅

As shown in Scheme 1, an oxygen source is required for the oxidation reaction of phosphorus. In the pretreatment process, solid iron oxides (FeO, Fe ₂ O ₃ ) are mainly used as oxygen sources. In some cases, gaseous oxygen obtained by separating air is used as a dephosphorizing agent, that is, an oxygen source. However, when gaseous oxygen is used, reaction with carbon, silicon, etc., which are important heat sources in molten iron, is performed before oxygen contributes to the dephosphorization reaction. As such, this method is mainly used in converter processes without pretreatment. For dephosphorization, as well as iron oxide, as shown in Schemes 2 and 3 above, quicklime (CaO) is mixed and used to stabilize and slag phosphate, and also improve the fluidity of slag to react phosphate and quicklime Fluorite (CaF ₂ ) is also used in parallel in order to facilitate this.

However, electrostatic precipitating dust, which is currently used as a dephosphorizer, has about 14% by weight of the total amount of solid dust contributing to the oxidation reaction of phosphorus (P). It contains a large amount of FeO). Since the metal iron is not substantially bonded with oxygen, it does not act as an oxygen source contributing to dephosphorization, and since iron oxide (FeO) also has a smaller oxygen source than ferric oxide (Fe ₂ 0 ₃ ), effectively phosphorus (P ) Does not oxidize. This means that in order to remove phosphorus as an impurity by the dephosphorization reaction, a large amount of electrostatic dust should be used as a dephosphor, which results in a long dephosphorization treatment time, a decrease in productivity, and an increase in load on equipment. to be. In addition, ultrafine metal iron and iron oxide are chemically unstable and cause a reoxidation reaction with ferric oxide, which is stable under a certain condition. This oxidation reaction is an exothermic reaction, which causes the possibility of fire, sintering and seizure of dust collecting dust. Great care must be taken in handling, transporting, storing, and manufacturing dust collection dust.

Therefore, an object of the present invention is to maximize the amount of solid oxygen of the electrostatic dust, shorten the dephosphorization treatment time, improve the productivity of the dephosphorization process, as well as demineralization process, such as reducing the load of the facility, the amount of slag generated waste It is to provide a method for producing a high efficiency molten iron dephosphorizing agent that can improve the economics.

Another object of the present invention is to provide a method for producing a high-efficiency molten iron dephosphorizing agent having a low possibility of fire, sintering and sticking, which is safe to handle and convenient to use.

It is still another object of the present invention to provide a method for producing an iron oxide pigment having high value by recycling electrostatic dust, which is an industrial waste.

In order to achieve the above object, the present invention comprises the steps of forcibly oxidizing the electrostatic precipitating dust generated in the converter; And adding quicklime and fluorspar to the forcibly oxidized electrostatic precipitating dust. The step of forcibly oxidizing the electrostatic precipitating dust may be carried out by heating the electrostatic precipitating dust in an air or oxygen atmosphere and the temperature of 200 to 600 ℃ for 10 seconds to 60 minutes, the addition amount of quicklime is the total dephosphor composition It is preferably 15 to 40% by weight, and the amount of the fluorspar is 5 to 15% by weight based on the total dephosphor composition.

The present invention also includes the step of forcibly oxidizing the electrostatic precipitating dust generated in the converter; And it provides a method for producing an iron oxide pigment comprising the step of classifying the forced oxidized electrostatic dust.

Hereinafter, the present invention will be described in more detail.

In dust converter operation of steel making process, electrostatic dust, which is a waste generated from a dry electrostatic precipitator connected to a converter, is known to be used as an oxidizing agent included in the dephosphorizing agent for molten iron. By forcing oxidation, it has been found that the problems caused when the electrostatic dust is used as it is can be solved, and that it can also be used as a pigment, thereby completing the present invention.

The electrostatic precipitating dust used in the present invention has a CaO content of 4 to 10% by weight, a SiO ₂ content of 0.2 to 2% by weight, a total content of iron (Fe) of 62 to 70% by weight, and a total oxygen content of about 12 to It is about 16% by weight, and under normal temperature conditions, no rapid oxidation or exothermic heat occurs, even when partially oxidized, no uniform oxidation occurs, and a relatively large diameter of oxide lumps are formed unevenly. However, if the forced oxidation by heating the dust collecting dust at a predetermined temperature as in the present invention, the diameter of the dust, the oxide particles increase relatively uniform, ferric preparation before oxide (Fe ₂ O ₃₎ content of component The content is increased by more than 200% by weight, the content of metal iron (M-Fe), iron oxide (FeO) is reduced by about 50% by weight or more, the total amount of oxygen is increased by about 40% by weight compared to before the forced oxidation. Therefore, when the dephosphorization process is performed through the oxidation reaction of phosphorus (P) as shown in Scheme 1, it is expected that the dephosphorization rate may be increased by 40% or more when forcibly oxidized dust collecting dust is used as a dephosphorizing agent. do. The increase in dephosphorization rate means that the dephosphorization time used in the pretreatment plant, that is, the dephosphorization time, can be shortened by 40% or more, which is economical, such as increased productivity, reduced load on the pretreatment facility, and reduced slag generation. This means that it is greatly improved.

In the method for producing a high efficiency molten iron dephosphorizing agent according to the present invention, the oxidation of the dust collecting dust is the electrostatic dust generated in the converter (air) and 200 to 600 ℃, preferably 200 to 400 ℃, more preferably May be carried out by heating at a temperature of 200 to 300 ° C. for 10 seconds to 60 minutes, preferably 10 seconds to 60 minutes, and oxidizing the dust collecting dust while injecting pure oxygen or air having an increased oxygen concentration, if necessary. You can also At this time, if the heating temperature is less than 200 ℃ or the heating time is less than 10 seconds, the oxidation of the current collector dust is not sufficiently made, if the heating temperature exceeds 600 ℃, or the heating time exceeds 60 minutes, the manufacturing cost increases There is a problem that the economic efficiency is lowered, such as a decrease in productivity. The oxidation reaction formula of metal iron and iron oxide in such dust collection dust is as follows.

FeO

Fe ₂ O ₃

Fe ₂ O ₃

As can be seen from the reaction scheme, since the metal iron and iron oxide are combined with oxygen and oxidized to the most stable ferric oxide (Fe ₂ O ₃ ), the total dust weight also increases by that amount. The metal oxide (Fe) and iron oxide (FeO) components in the dust collected by the forced oxidation, such as not completely converted into ferric oxide, the surface of the dust particles are completely oxidized to ferric oxide (Fe ₂ O ₃ ), The oxidation of the dust particles is not well progressed because the iron oxide (FeO) or iron (Fe) component remains, which shows that the progress of oxidation into the dust particles is the rate step of the reaction. As described above, even when the dust is forcibly oxidized in the dust collecting part, iron oxide (FeO) or iron (Fe) components remain in the dust, but these are usually located inside the dust particles, and thus the handling stability and pretreatment process of the dust. Does not have an excessively adverse effect on the oxidation of phosphorus (P).

In general, iron components present in dry dust and in Fe or FeO state do not undergo rapid oxidation under normal temperature conditions, but they are partially unevenly oxidized during transportation, storage, and manufacturing, causing fire, sintering, and sticking. There is a possibility. However, dust collection dust forcibly oxidized according to the method of the present invention has a form coated with ferric oxide (Fe ₂ O ₃ ), which is a chemically very stable form, and thus transport, storage, manufacture, and the like of dust collection dust. There is an advantage that can secure the safety.

In order to produce a new high efficiency molten iron dephosphor using the electrostatic precipitating dust in this way, quicklime (CaO) is added to 15 to 40% by weight, preferably 20 to 30% by weight relative to the total dephosphor composition Fluorite is added in an amount of 5 to 15% by weight, preferably 7 to 10% by weight. In this case, the burnt lime is, the P ₂ as being added to convert the like P ₂ O ₅ a stable slag screen the compounds _{3CaO · P 2 O 5, 4CaO} · P 2 O 5, when the amount of the calcium oxide is less than 15% by weight It is difficult to produce O ₅ as a stable compound, and it has little effect on the dephosphorization rate even if it exceeds 40% by weight, and the amount of solid oxygen contributing to the dephosphorization reaction is reduced due to the reduction of the mixing ratio of the forced oxidized dry dust. There is only a risk of deterioration. The fluorspar is added to increase the flowability of the slag, when the addition amount of the fluorspar is less than 5% by weight can not sufficiently secure the fluidity of the slag to reduce the dephosphorization reaction efficiency, in the case of exceeding 15% by weight The refractory may be damaged.

On the other hand, the electrostatic precipitating dust generated in the converter is an ultra fine powder having about 80% by weight of particles having a particle size of 30 μm or less. When the dust is forcibly oxidized, the dust color changes from reddish brown to reddish brown. It contains about 43% by weight of particles having a phosphorus of 325 mesh (0.043 mm) or less. The reason why the particle size increases after oxidation is that the oxidation reaction occurs more rapidly as the fine powder is formed, and because the reaction surface area is wide, the fine particles adhere to each other. For forced oxidized dust dust, to examine its applicability as iron oxide pigments specified in KS M 5102, the oxidized dust dust is sieveed to an appropriate size, preferably 325 mesh, and then 325 Sub-mesh samples were subjected to component analysis using a fluorescence analyzer (XRF). As a result, it was found that the content of ferric oxide (Fe ₂ O ₃ ), which is a component specification of the iron oxide pigment, increased from 15.3% by weight to 78.7% by weight before forced oxidation. Table 1 shows physical properties of grades (1 to 5) of the iron oxide pigments defined in Korean Industrial Standard KS M 5102.

Type 1 2 types 3 types 4 types 5 types Ferric Oxide (Fe ₂ O ₃ ) (wt%) 98.5 or more 96.0 or more 92.0 or higher 85.0 or more 70.0 or more Moisture and Volatility (wt%) 0.5 or less 1.0 or less 1.0 or less 1.0 or less 2.0 or less Ignition loss (% by weight) 1.0 or less 2.5 or less 2.5 or less 3.0 or less 5.0 or less Water dissolved content (% by weight) 0.3 or less 0.5 or less 0.8 or less 1.0 or less 1.5 or less pH 6.0-8.0 6.0-8.0 5.0-8.0 - - Organic pigment No No No No No Sieve (45 μm), non-permeable (wt%) 0.3 or less 0.5 or less 0.5 or less 1.0 or less 2.0 or less

As shown in Table 1, the component specifications of the iron oxide pigment is divided into 1 to 5 types according to the ferric oxide (Fe ₂ O ₃ ) content, the ferric oxide (Fe ₂ O ₃ ) content is 70% by weight If it is above, it will be divided into 5 types, and if it is 85 weight% or more, it will be divided into 4 types. That is, when classifying dust-collected dust forcibly 325 mesh or less, it turns out that it is applicable to the 5th type of iron oxide pigment. Therefore, by producing high value-added iron oxide pigments using dust collecting dust which is general waste, it is possible to realize effective resource recycling.

Next, a preferred embodiment for helping understanding of the present invention is presented. However, the following examples illustrate the present invention and do not limit the present invention.

Example 1 Preparation of High Efficiency Dephosphor Raw Material and Chartering Dephosphor

In order to forcibly oxidize the dust collector, the furnace temperature was first set to 300 ° C., and the trivet was placed in the furnace so that the sample vessel could be exposed to the ambient temperature. In addition, a laser thermometer (Potable Laser) was prepared to measure the ignition temperature and the measurement position was fixed at the center of the sample. A vessel containing 30 g of dust collection was placed on the trivet and heating was started. Oxidation reaction started when the dust which was blackish brown became reddish brown at 228 degreeC, and the temperature of the sample rose to 390 degreeC by the oxidative exothermic reaction. After 5 minutes after the surface oxidation started, it was taken out and air-cooled in a desiccator to prevent reaction with moisture in the air. After 3 hours, the sample was removed from the dryer and weighed with an electronic balance (chemical balance), and the component analysis was performed using a fluorescence analyzer (XRF). After performing three times in the same manner, the components before and after forced oxidation were analyzed and the results are shown in Table 2. In addition, quicklime (CaO) was added to the forced oxidized dust collecting dust to 25% by weight of the total dephosphor composition, and 10% by weight of fluorite was added to the total dephosphor composition to prepare a molten iron for molten iron.

division Ingredient (% by weight) Particle size (% by weight) (-325mesh) Sample weight (g) color M-Fe FeO Fe ₂ O ₃ T-Fe CaO Before oxidation 22.6 42.1 15.3 66.1 8.2 84.1 30.0 Dark brown After oxidation 12.6 15.3 54.2 62.2 7.4 43.5 32.3 maroon

As can be seen from Table 2, after the oxidation, the ferric oxide (Fe ₂ O ₃ ) component was increased by 254% by weight compared to before the oxidation, metal iron (M-Fe), iron oxide (FeO) content is about 55% by weight Decreased. The amount of solid oxygen (considering only the oxidation reaction of Fe and FeO components) that contributed to the dephosphorization reaction increased by 41.7 wt% from 13.9 wt% before dust oxidation to 19.6 wt% after oxidation. When used, it can be seen that the dephosphorization rate can be increased by more than 40% by weight. In addition, from Table 1, the weight of the sample before oxidation was 30g, but the weight was increased to 32.3g after oxidation by 7.7% by weight, which is a natural addition increase according to the forced oxidation of the dust collecting dust, it can be seen that the amount of oxidant is effectively increased. Can be.

Example 2 Preparation of High Value Added Iron Oxide Pigments

Ultrafine powdery dust-collected dust powder having a particle size of about 30% or less, which is blackish brown, is forcibly oxidized according to the method described in Example 1, reddish brown, and has a particle size of 325 mesh (0.043 mm) or less. Iron oxide powder having a content of about 43 wt% was prepared. After the obtained iron oxide powder was sifted with a 325 mesh sieve, a sample of 325 mesh or less was subjected to component analysis using a fluorescence analyzer (XRF). As a result of the component analysis, the content of ferric oxide (Fe ₂ O ₃ ), which is a component specification of the iron oxide pigment, increased from 15.3 wt% to 78.7 wt% before oxidation, and the obtained iron oxide was defined in KS M 5102 (see Table 1). It can be seen that it can be applied as a fifth type iron oxide pigment accordingly.

As described above, the method for producing a high efficiency molten iron dephosphorization agent according to the present invention maximizes the amount of solid oxygen in the electrostatic dust generated in the converter, and when used as a dephosphor in the pretreatment process of the steel mill, the dephosphorization treatment time is shortened. In addition to improving the productivity of dephosphorization treatment process, it is possible to improve the economics such as reducing the load of equipment and reducing the amount of slag generated as waste, and there is less possibility of fire, sintering and seizure during storage or transportation, and it is safe to handle. have. In another aspect, the present invention provides a method for producing a high value iron oxide pigment by recycling the electrostatic dust dust as an industrial waste.

Claims (5)

Occurs in converters containing 4 to 10% by weight of quicklime, 0.2 to 2% by weight of SiO ₂ , 62 to 70% by weight of total Fe, and 12 to 16% by weight of total oxygen. Forcing oxidation of finely divided electrostatic dust; And Method of producing a molten iron for molten iron comprising the step of adding quicklime and fluorspar to the forced oxidized electrostatic dust. The method of claim 1, wherein the step of forcibly oxidizing the electrostatic precipitating dust is carried out by heating the electrostatic precipitating dust in an air or oxygen atmosphere and the temperature of 200 to 600 ℃ for 10 seconds to 60 minutes. Preparation of Inje. According to claim 1, wherein the amount of quicklime added is 15 to 40% by weight based on the total dephosphor composition, the amount of fluorspar is 5 to 15% by weight based on the total dephosphor composition of the molten iron dephosphorizing agent Manufacturing method. delete Occurs in converters containing 4 to 10% by weight of quicklime, 0.2 to 2% by weight of SiO ₂ , 62 to 70% by weight of total Fe, and 12 to 16% by weight of total oxygen. Forcing oxidation of finely divided electrostatic dust; And Method for producing an iron oxide pigment comprising the step of classifying the forced oxidized electrostatic dust.