KR100301993B1 - Method for treating dust in electric furnace - Google Patents

Abstract

PURPOSE: A method for treating dust in an electric furnace is provided which greatly reduces loss of zinc by a reducing agent by smelting reducing the sorted materials after sorting magnetic constituents and non-magnetic constituents using a fluidized bed magnetism sorter. CONSTITUTION: The method for treating dust in an electric furnace comprises the steps of reducing dust of the electric furnace using flue gas of a pre-reduction furnace by charging the dust of the electric furnace in a dust tank(110) of the electric furnace into a fluidized bed reduction furnace(120), and cooling the dust to an ordinary temperature by charging the reduced dust of the electric furnace into a cooler(140); manufacturing into non-magnetic substance pellets by bulking the non-magnetic substance dust in a non-magnetic substance pelletizer(190A) and manufacturing magnetic substance pellets by bulking magnetic substance dust along with reducing agent and flux in a magnetic substance pelletizer(190B) after sorting dust of the electric furnace in the dust tank(110) of the electric furnace and the cooled dust of the electric furnace into magnetic substance dust and non-magnetic substance dust using a fluidized bed magnetism sorter(160); reducing the charged magnetic substance pellets using flue gas of a zinc condenser(220) partially burned or heated in a hot blast stove(230) after charging the magnetic substance pellets into a pre-reduction furnace(200); manufacturing pig iron by smelting reducing the charged magnetic and non-magnetic substance pellets after charging the pre-reduced magnetic and non-magnetic substance pellets into a smelting reduction furnace(210); and manufacturing condensed zinc by condensing zinc gas contained in the flue gas of the smelting reduction furnace.

Description

Electric Furnace Dust Treatment

The present invention relates to an electric furnace dust treatment method for obtaining pig iron and condensed zinc by melting and reducing electric dust of magnetic powder and non-magnetic powder, and more particularly, by selecting magnetic and non-magnetic components using a fluidized bed magnetic separator. It relates to an electric furnace dust treatment method capable of greatly reducing the Zn loss caused by the reducing agent by melt reduction.

In general, EAF dust contains 5 ~ 25% Zn and Fe 15 ~ 50% although there are many differences depending on the raw material condition of the electric furnace.

In addition, as the proportion of galvanized steel in scrap metal is recently increased, the Zn content in the dust of the electric furnace is increasing.

Zn is 50 to 80% of the content is ZnO, the remainder is present as zinc ferrite spinel (Zincferite spinel: ZNO.Fe ₂ O ₃ ) and a small amount of the metal Zn.

In addition, the Fe is mostly present as Fe ₂ O ₃ or ferrite spinel (MO · Fe ₂ O ₃ , M = Zn, Mn, Ni, etc.). Such particle size is generally 40 µm or less.

Conventionally, ZnO in dust is reduced to Zn gas to obtain condensed Zn by charging and melting in the melting furnace as it is, without electrically compacting the dust. However, it has been a problem that the condensed Zn contains a considerable amount of iron dust.

In order to solve this problem, many studies have been conducted. For example, at Sumitomo, Japan, as shown in FIG. 1, the dust is first compacted in the pelletizer 40 and then preliminarily. in the reducing furnace (50) ZnO is charged to then while reducing the dust into electrical pellets by adjusting the CO / CO ₂ ratio of the reducing gas to be reduced to only without reducing iron oxide, optionally at the same time it is curing a smelting reduction 60 By doing so, there has been reported a method to significantly reduce the dust content of iron in the condensed Zn.

However, according to this method, the reduction rate of iron oxide in the reduction furnace 50 was about 30 to 35%, and the reduction of ZnO to Zn gas and the metal Zn vaporization were also performed simultaneously, resulting in a loss of 10%. The higher this is, the more Zn losses are expected.

In addition, in the preliminary reduction reactor 50, since the ratio of CO / CO ₂ must be adjusted in the reducing gas so that only iron oxide can be selectively reduced without reducing ZnO, the upper limit of the ratio is about 1.0 when the Zn content increases. There is a limited problem.

Accordingly, the present invention has been made in order to solve the conventional problem as described above, and after preliminarily reducing only the magnetic component by selecting the magnetic component and the non-magnetic component, the pre-reduction rate is high and zinc by melt reduction of the pre-reduced magnetic component and non-component It is an object of the present invention to provide an electric dust treatment method that can effectively reduce the loss.

1 is an electric furnace dust treatment method recently developed by Sumitomo Heavy Industries, Japan.

2 is a furnace dust treatment method according to the present invention

* Explanation of symbols for the main parts of the drawings

110: EAF Dust Bin 120: Fluidized Bed Reduction Furnace

140: cooler 160: flow-side magnetic separator

170: non-magnetic component storage tank 180: magnetic component storage tank

190A, 190B: Pelletizer 200: Shaft Furnace

210: Melting Furnace 220: Zinc Condencer

230: Hot Gas Generator 240: Reduction Production

250: Solvent

The present invention is to prepare the pig iron by molten reduction by pre-reduction of the dust in the melting and reduction of electric furnace dust consisting of magnetic and non-components in the molten reduction reactor, and zinc zinc contained in the exhaust gas of the molten reduction reactor In the method of treating the dust in the electric furnace, including the step of condensing in the condenser to produce a condensed zinc, partially burning and heating the exhaust gas of the zinc condenser in the hot stove to supply to the preliminary reduction reactor,

Charging electric furnace dust into a fluidized-bed reduction furnace to reduce electric furnace dust by pre-reduction furnace exhaust gas, charging the reduced electric furnace dust into a cooler and cooling it to room temperature;

The electric dust or the cooled electric dust is separated into magnetic dust and non-magnetic dust by fluidized bed magnetic separator, and the non-magnetic dust is agglomerated in a non-magnetic pelletizer and manufactured into a non-magnetic pellet, and the magnetic dust is a magnetic substance. Compacting together with a reducing agent and a solvent in a pelletizer to prepare a magnetic pellet;

Charging the magnetic pellets into a preliminary reduction reactor and reducing the exhaust gas of a zinc condenser that has been partially burned and heated in a hot stove;

Preparing the pig iron by charging the pre-reduced magnetic pellets and non-magnetic pellets in a melt reduction furnace and melting reduction; And

Condensing zinc gas contained in the melt reduction flue gas in the zinc condenser 220 to produce a condensed zinc; relates to an electric dust treatment method comprising a.

Hereinafter, the present invention will be described in detail.

2 shows an example of a preferred process of the electric furnace dust treatment method of the present invention.

As shown in FIG. 2, the electric furnace dust 111 composed of magnetic and non-components in the electric furnace dust tank 110 is charged into the fluidized-bed reduction furnace 120 to discharge the exhaust gas 130 of the preliminary reduction reactor 200. It is reduced while forming a bubble fluidized layer by).

Reduction process of the preferred electric dust dust 111 in the fluidized-bed reduction reactor 120, the Fe ₃ O ₄ is stabilized by mixing the converter exhaust gas or blast furnace exhaust gas 131 to the exhaust gas 130 of the preliminary reduction reactor (200). Reducing Fe ₂ O ₃ to Fe ₃ O ₄ while forming a bubble flow layer by reducing exhaust gas adjusted to temperature and gas oxidation.

In order to reduce the Fe ₂ O ₃ to Fe ₃ O ₄ according to the present invention, since a fast reduction rate and a relatively low temperature and high oxidation degree of reducing gas are required, by-products of steelmaking, such as blast furnace flue gas or converter flue gas 131, It can be used as it is without further processing.

In the fluidized-bed reduction furnace 120, the CO / CO ₂ ratio of the reducing gas during the reduction of the electric furnace dust 111 is preferably set at 0.1 to 0.8, and the reduction temperature is 500 to 600 ° C.

As described above, the reduced dust of the electric furnace is discharged from the fluidized bed reduction furnace 120 to the cooler 140 and cooled to a room temperature in the cooler 140.

The dust cooled by the electric power from the cooler 140 is charged to the fluidized bed magnetic separator 160 so that nonmagnetic materials (Zn, ZnO, ZnO · SiO ₂ , SiO ₂ , CaO, MgO, etc.) and ferromagnetic materials (Fe ₃ O ₄ , Ferrite) spinel, etc.).

At this time, to an electric glass Fe ₂ O ₃ of the dust to the electricity in the dust tank 110 less 112 without passing through the 120 and the condenser 140 to the fluidized bed reduction, direct fluid bed magnetic separator 160 Charges.

On the other hand, as a magnetic separator for selecting the particulate magnetic material and the nonmagnetic material in the fluid state, the fluidized bed magnetic separator proposed in Korean Patent No. 93-012110 (July 1, 1993) can be used.

The nonmagnetic material selected by the fluidized bed magnetic separator 160 is transferred to a nonmagnetic pelletizer 190A and then agglomerated to produce nonmagnetic pellets.

In addition, the magnetic material selected by the fluidized bed magnetic separator 160 is transferred to a magnetic pelletizer 190B, mixed with a reducing agent and a solvent, and then agglomerated to produce a magnetic pellet.

The magnetic pellets containing iron oxide as a main component are charged into the preliminary reduction furnace 200 and reduced by using the exhaust gas 222 of the zinc condenser 220 that is partially burned and heated in the hot stove 230.

As described above, in the operation of the preliminary reduction furnace 200 in which only the magnetic material is secondaryly reduced, the ratio of CO / CO ₂ in the reducing gas is 0.5 to 10, and the reduction temperature is preferably 750 to 900 ° C.

The pre-reduced magnetic pellets and the non-magnetic pellets are charged to the melt reduction reactor 210 and melt-reduced to produce pig iron, and discharged together with the slag.

Condensed zinc is produced by condensing the zinc gas contained in the exhaust gas into the molten reduction 210 in the zinc condenser 220.

In addition, the exhaust gas 222 of the zinc condenser 220 is supplied to the hot stove 230, partially burned and heated to a preliminary reduction reactor 200. In FIG. 2, the dotted line means the flow of gas.

As described above, the present invention focuses on the fact that zinc is present in the Zn, ZnO, ZnO.SiO ₂ state of the nonmagnetic substance and ZnO · Fe ₂ O _{3 of the} ferromagnetic substance, and the nonmagnetic substance is most of the total zinc. The spleen was separated from the magnetic material and charged into the molten reduction reactor without going through the preliminary reduction reactor, thereby greatly reducing the Zn loss in the reduction furnace.

Therefore, since ZnO is not reduced in the preliminary reduction furnace, the selection range of the CO / CO ₂ ratio in the reducing gas to be adjusted to selectively reduce only the iron oxide is widened.

That is, since the reducing power of the reducing gas is increased, the pre-reduction rate can be significantly increased, and the burden on the melt reduction reactor can be significantly reduced.

In the case of a large amount of free Fe ₂ O ₃ in the dust, it is reduced to Fe ₃ O ₄ , which is a forcing material, to significantly reduce the Fe content in the non-magnetic material to be treated separately, and to reduce the iron dust content of the Zn layer condensed when directly charged into the furnace. Can be.

Hereinafter, the present invention will be described in detail through examples.

Example 1

Electromagnetic dust is separated from the magnetic material by a fluidized bed magnetic separator as disclosed in Korean Patent No. 93-012110, and then made into a spherical pellet having a particle diameter of 20 mm and placed in a vertical test tube with a chan balance. Suspended by preliminary reduction, and then chemically analyzed to measure the loss of Zn in the preliminary reduction reactor, and compared with that produced by reducing pellets without separating dust into magnetic and nonmagnetic materials.

At this time, the raw material conditions and pre-reduction conditions were as follows.

1) Raw material condition:

-Composition of basin with raw material electric furnace: ZnO = 25.3%, Zn = 5.5%, ZnO · Fe ₂ O ₃ = 22.8%, Fe ₂ O ₃ = 2.2%, others = 44.2%

-Particle size distribution of dust with dust: less than 2㎛ = 40.7%, 2 ~ 10㎛ = 12.5%, 10 ~ 20㎛ = 18.4%,

20-40 μm = 11.9%, 40 μm or more = 16.5%,

2) Pre-reduction conditions:

-Preliminary reduction gas composition: CO 70%, CO ₂ 14%, N ₂ 16%

-Pre-reduced gas flow rate: 0.9 Nm ³ / hr

Preliminary reduction time: 1 hour

Preliminary reduction temperature: 850 ℃

As a result of this experiment, when the pellets were made without separating the nonmagnetic material, the Zn loss was about 11% at the reduction rate of about 50%, but the loss was not reduced when the nonmagnetic material was separated from the magnetic material by the fluidized bed magnetic separator and then reduced. Reduced to 5%.

Example 2

In order to indirectly evaluate the dust content of iron in the solidified Zn in the Zn condenser, free Fe ₂ O ₃ was converted into Fe ₃ O ₄ during the dust in the fluidized-bed reduction furnace using an electric furnace dust containing high Fe ₂ O ₃ . and when the preliminary reduction to release the non-magnetic material in a fluid bed magnetic separator after cooling to room temperature from a magnetic material, and then a non-magnetic material of the analyzed the iron / zinc content ratio separating it from the Fe ₃ O ₄ magnetic material to without reduction as a non-magnetic material to the Compared.

At this time, the raw material conditions and the primary pre-reduction conditions were as follows.

1) Raw material condition:

-Composition of basin with raw material electric furnace: ZnO = 20.8%, Zn = 6.1%, ZnO · Fe ₂ O ₃ = 18.3%, Fe ₂ O ₃ = 15.5%, others = 39.3%

-Particle size distribution of dust with dust: less than 2㎛ = 35.2%, 2 ~ 10㎛ = 12.9%, 10 ~ 20㎛ = 17.4%,

20-40 μm = 15.1%, 40 μm or more = 19.4%,

2) Pre-reduction conditions:

-Preliminary reduction gas composition: CO 27.5%, CO ₂ 39%, H ₂ 10% H ₂ O 18.5% N ₂ 5%

-Pre-reduced gas flow rate: 3 Nm ³ / hr

Preliminary reduction time: 20 minutes

Preliminary reduction temperature: 550 ℃

As a result of the analysis, the iron / zinc content ratio in the nonmagnetic body was about 0.77 when the separation was performed without the first preliminary reduction, but the first preliminary reduction of free Fe ₂ O ₃ to Fe ₃ O ₄ in the dust of the electric furnace in the fluidized-bed reduction reactor When the nonmagnetic material was separated from the magnetic material, the iron / zinc content ratio of the nonmagnetic material decreased to about 0.31.

As described above, the present invention separates the nonmagnetic material composed mainly of Zn, ZnO, ZnO.SiO ₂ in the electric dust, and the magnetic material composed mainly of Fe ₂ O ₃ and ferrite spinel by magnetic field lines. Charged into the melt reduction reactor, the magnetic material is preliminarily reduced the iron oxide component in the preliminary reduction reactor and charged into the molten reduction reactor, thereby reducing the Zn loss in the preliminary reduction reactor.

In addition, the present invention is to increase the upper limit of the CO / CO ₂ ratio of the reducing gas, that is, to reduce the ZnO in the preliminary reduction reactor to selectively reduce only the iron oxide, that is, to increase the upper limit reducing power of the reducing gas in the preliminary reduction reactor The reduction rate is significantly increased to reduce the reduction burden in the furnace.

Claims (5)

After pre-reduction of dust by magnetic and non-component electric furnaces in a preliminary reduction reactor, charged into a molten reduction reactor to produce pig iron by melt reduction, and condensation of zinc gas contained in the exhaust gas of the molten reduction reactor in a zinc condenser In the process for producing condensed zinc, the process of treating the dust in the furnace, including the step of partially burning and heating the exhaust gas of the zinc condenser in a hot stove to supply to the preliminary reduction reactor The electric furnace dust in the electric furnace dust tank 110 is charged to the fluidized-bed reduction furnace 120 to reduce the electric dust by the pre-reduction furnace exhaust gas, and the reduced electric furnace dust is charged to the cooler 140 to room temperature. Cooling; The electric furnace dust in the electric furnace dust tank 110 or the cooled electric furnace dust is separated into magnetic dust and non-magnetic dust by the fluidized bed magnetic separator 160 so that the nonmagnetic dust is a nonmagnetic pelletizer 190A. Agglomerated in to prepare a non-magnetic pellet, and magnetic powder is agglomerated with a reducing agent and a solvent in a magnetic pelletizer 190B to produce a magnetic pellet; Charging the magnetic pellet into the preliminary reduction furnace 200 and reducing the exhaust gas of the zinc condenser 220 that is partially burned and heated in the hot stove 230; Preparing the pig iron by charging the pre-reduced magnetic pellets and non-magnetic pellets in a melt reduction furnace (210) and melting reduction; And Preparing condensed zinc by condensing zinc gas contained in the melt reduction flue gas in a zinc condenser (220); Furnace dust treatment method characterized in that it comprises a The method according to claim 1, wherein a converter flue gas or a blast furnace flue gas is mixed with the preliminary flue gas flue gas supplied to the fluidized-bed reduction furnace. The method according to claim 1 or 2, wherein the CO / CO ₂ ratio in the reducing gas is 0.1-1.8 and the reduction temperature is 500-600 ° C. when the dust of the furnace is reduced in the fluidized-bed reduction furnace 120. The method according to claim 1 or 2, wherein the CO / CO ₂ ratio in the reducing gas is 0.5-10 and the reduction temperature is 500-600 ° C. when reducing the magnetic pellets in the preliminary reduction reactor 200. According to claim 3, wherein the CO / CO ₂ ratio of the reducing gas when reducing the magnetic pellets in the preliminary reduction reactor 200 is 0.5-10, characterized in that the reduction temperature is 500-600 ℃