KR900006695B1 - Process for recovering valuable metals from an iron dust constaining a higher content of zinc - Google Patents

Abstract

Steel dust containing Zn is pelletised and fed into a reduction furnace. Reduction of the Fe-oxides is performed under an atmosphere controlled according to the temperature and the CO/CO2 range in the area surrounded by the equilibrium curves for the reactions of ZnO+CO= Zn+CO2, FeO+CO= Fe+CO2 and C+CO2= 2CO. Zn and Fe are effectively recovered from the steel dust.

Description

Recovery of Valuable Metals from Steelmaking Dust

1 is a flowchart of the apparatus for implementing the valuable metal recovery method of the present invention.

2 is a diagram showing the relationship between the gas partial pressure in the pre-reduction path of the preheating and the preliminary reduction path, in particular, the hatched portion is set to Pzn = 0.20 atm, and the area surrounded by the equilibrium line of the component partial pressure at Pco + Pco ₂ = 0.98 atm. Display.

* Explanation of symbols for main parts of the drawings

1: Assembly Machine 2: Preheating, Preliminary Reduction Furnace

3: low frequency induction furnace 4: lead wire

5: zinc condenser 6: cooling tube

7: zinc (or lead) circulation pump 8: gas temperature component adjustment

9: gouks dryer 10: dust collector

11 chlorine removal device 12 desulfurization device

D: Go zinc steel dust C: Corks

Sl: slag Fe: molten pig iron

Zn: molten zinc Pb: molten lead

G: exhaust gas, A, A1, A2: air CO: CO gas

The present invention relates to a method for recovering valuable metals such as zinc and iron from, for example, high zinc-containing iron dust generated in steelmaking in an electric furnace. For example, dust generated in an electric furnace is collected by a dust collector, but the amount of dust usually corresponds to l-1.5% of crude steel. Although it contains a lot of valuable metals such as iron 25-30%, zinc 20-25% and lead 3-4%, it is small and has no easy recovery method. It is true. As such a recovery method, a rotary kiln furnace furnace or a treatment method using plasma heat has recently been proposed. The present invention has been studied in consideration of the above-described phenomenon, and an object thereof is to provide a valuable metal recovery method capable of recovering valuable metals from high zinc steelmaking dust easily and with low processing energy.

In the recovery method of the valuable metal according to the present invention, high zinc steelmaking dust is assembled into pellets, and the pellets are charged into a furnace of a shaft type with a reduction part at the upper part and a lower part at the lower part of the preheating part. Preheating of the pellets is carried out in the preheating section by using CO2 exhaust gas, and pre-reduction of the pellets under the gas condition of CO ₂ / CO ratio which actively reduces the reduction of zinc oxide by suppressing the reduction of zinc oxide as much as possible. Pre-reduced pellets are added to the induction furnace together with the carbonaceous solids reducing agent and melt-reduced in the induction furnace to separate zinc by distillation to make crude zinc. Iron and lead are separated by specific gravity, and iron is molten pig iron, and lead is prepaid. As a result, it is easy to recover with low processing energy.

Hereinafter, the present invention will be described according to an embodiment in which the drawings are created. The high zinc steelmaking dust D is assembled into pellets of 6-15 mm in the granulator 1. The pellets made of the particles are charged to the preheating, preliminary reduction of the shaft type. In the preheating section of the shaft, the carbon in the CO-CO ₂ gas that has risen through the preliminary reduction section and the carbon containing the pellet are burned by the combustion air A ₂ (if necessary, oxygen load is also applied) and pellets Is heated in a short time. This preheating section also removes moisture and ignition loss components in the pellets. The heated pellets are transferred to the reducing unit and adjusted by the gas temperature and component adjusting furnace 8 to react with the reducing gas, thereby preliminarily reducing the iron oxide. The gas conditions buried in this reducing unit actively cause the reduction of the iron oxide. That is, it is adjusted such that the area enclosed by pyeonghyeongseon and C + CO ₂ = 2CO pyeonghyeongseon of Fe O + CO = Fe + CO 2. In addition, the gas condition at a region indicated by hatched portion in the figure 2, when in order to as much as possible inhibit the reduction of zinc oxide, for example, set to PZn = 0.02 atm, and adding a pyeonghyeongseon of ZnO + CO = Zn + CO ₂ Set it. The pre-reduced pellets are fed to the low frequency induction furnace 3 together with the coke C dried by the coke dryer 9 so that iron oxides, zinc oxide and lead oxides are reduced and melted and most of the remaining metal oxides are slag S1. Form. The reduced iron is molten pig iron (approximately 4% C) Fe, discharged from the induction furnace 3 and charged at high temperature in the subsequent electric furnace.

The produced slag is drawn off with a molten iron under stirring while energized in an induction furnace, or temporarily discharged by terminating the current, or discharged from a separate outlet as is normally practiced in a blast furnace.

Reduced lead Pb is separated from the molten iron due to its relatively high specific gravity, so it accumulates in the lead 4 (4) in the lower part, so it is regularly removed.

The reduced zinc Zn is melted and circulated by a zinc circulating (or lead circulating) pump 7 which is induced by the zinc condenser 5 in a gaseous state together with the reducing gas CO. Or condensed as a liquid object, cooled in the cooling vessel 6 to remove impurities, and then recovered as crude zinc.

CO, the reducing gas exiting the condenser (5), is led to the gas temperature, component control furnace (8). In this regulating furnace, the reducing gas CO is burned at once by combustion air A ₂ (if necessary, enriched with oxygen) and adjusted to a gas condition that satisfies the preliminary reduction condition.

The exhaust gas of the preheating and preliminary reduction path 2 is led to the coke dryer 9 and used for drying the coke, and then outside the system after the dust collector 10, the chlorine removal device 11 and the desulfurization device 12. Discharged.

As described above, according to the present invention, the high zinc steelmaking dust is made into large chunks, followed by preheating, removal of moisture in the pellets, carbon and ignition loss components in the preliminary reduction furnace, and preliminary reduction of acid and iron, followed by melting and reducing in the induction furnace and zinc. The silver was separated by distillation, and as crude zinc, iron and lead were separated by specific gravity, iron was molten pig iron, and lead was recovered by prepaid.

(1) In the preheating and preliminary reduction furnaces, the preliminary reduction of iron oxides charged to the induction furnaces reduces the power load of the induction furnaces.

(2) The preliminary reduction of the iron oxide can reduce the FeO component which reacts with the induction furnace refractory to significantly reduce the life of the refractory, and thus it is expected to extend the refractory life.

(3) In the preliminary reduction section, the reduction of zinc oxide is suppressed as much as possible, and the reduction of iron oxide is operated in a gas condition that actively occurs, so the charged gas conditions are FeO + CO = Fe + CO ₂ , C + CO ₂ = 2CO again according to the vapor pressure of zinc ZnO + CO = Zn + If CO limited to the area surrounded by the three pyeonghyeongseon of _2, for example CO corresponding extent preheated, PZn = 0.02 eseo the partial pressure of the bottom CO highest part in the preliminary reducing pressure If the partial pressure and temperature of is set, the partial pressure of the gas rising while reacting in the furnace in the upper part of the furnace is considerably lower than that of the Roger and the temperature is also lowered. have.

(4) The induction furnace has a high agitation force and may have a rim structure, which is suitable for melting, reducing, and distilling zinc, and recovering valuable metals easily.

(5) By removing the ignition loss part in advance, when the pellets are charged into the induction furnace, stable operation of the capacity is possible without causing bursting and dust generation can be suppressed.

(6) In addition to being able to preheat pellets by pre-burning the carbon content of the fuel, carbon as a reducing agent necessary for the reduction of the pellets in the induction furnace is not supplied from the coal ash existing in the pellet, the so-called coal, and the molten iron in the induction furnace. Since it is supplied from carbon, the reduction of metal oxides in the pellet occurs only at the pellet surface. As a result, it is possible to prevent sudden gas generation or breakdown of the pellets when the pellets with the anti-burnt are exposed at high temperatures, and to suppress the sudden boiling of the dust or the generation of dust. Therefore, stable operation of the capacity is possible.

(7) Reduction of deposits by induction furnace alone generates excess gas, which can be expected to be used effectively depending on the location conditions. However, according to the method of the present invention, the energy possessed by the gas can be effectively utilized by preheating the pellet by combustion after use for preliminary reduction or preliminary reduction, and overall energy can be saved.

Claims (1)

High zinc steelmaking dust is assembled into pellets, and the pellets are preheated in the upper part of the shaft, and the preheating part of the shaft type having a reducing part in the lower part and charged into a pre-reduction path to remove the moisture, carbon and ignition loss components of the pellets from the preheating part. removing charged gas conditions in the reduction unit and the (temperature, CO / CO ₂ ratio) of ZnO + CO = Zn + CO equilibrium lines of the _{2, FeO + CO = Fe +} CO 2 the pyeonghyeongseon and C + CO ₂ = 2CO pyeonghyeongseon of The reduction of zinc oxide is strongly controlled by setting in the area surrounded by the gas, whereas the reduction of iron oxide is pre-reduced to actively cause reduction, and then the pre-reduced pellet is poured into the induction furnace together with the carbonaceous solid reducing agent and melted in the induction furnace. By reducing, zinc is separated by distillation and recovered as crude zinc, iron and lead are separated with specific gravity, iron is molten pig iron, and lead is recovered as crude iron. Precious metals recovery process.

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