RU2824119C1 - Method for pyrometallurgical extraction of zinc from dust of arc steel-making furnaces - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to processing of technogenic formations of ferrous metallurgy and can be used for extraction of zinc from dust of arc steel-making furnaces. Method includes chemical analysis of dust of arc steel-making furnaces, mixing of dust of arc steel-making furnaces, solid carbonaceous reducing agent and flux, combined grinding of the mixture, its agglomeration by way of pressing in the form of briquettes, Waelz process of briquettes in a rotary furnace with supply of blast in the form of a steam-air mixture with steam content in mixture of 14–25%. Composition of the flux is determined from the data of chemical analysis of the processed dust with the addition of acidic or basic oxides before mixing the raw mixture to a level which ensures the fulfillment of the ratio (SO₃+Cl+F)/(Na₂O+K₂O)≥1. Steam-air mixture is introduced into the temperature zone of 1,000 °C, the temperature is increased to 1,100 °C and part of the sublimate containing easily sublimable compounds is removed from the furnace. After that, furnace temperature is raised to 1,350 °C and sublimate is extracted.

EFFECT: method provides higher quality of zinc sublimate at the stage of pyrometallurgical treatment without application of hydrometallurgical processing.

1 cl, 3 tbl

Description

The invention relates to the processing of man-made formations of ferrous metallurgy and can be used to extract zinc from dust of electric arc steel-smelting furnaces.

A method for producing zinc is known, which consists of introducing coke into a zinc-containing charge, heating the charge in a rotary kiln to a temperature of 1300°C, sublimating the zinc, oxidizing it, and capturing the resulting zinc oxide (Lakernik M.M., Pakhomova G.N. Metallurgy of zinc and cadmium. Moscow: Metallurgizdat, 1969, pp. 393-409). A disadvantage of this method is the contamination of zinc oxide with compounds of chlorine, fluorine, potassium, sodium, lead, and sulfur, which are sublimated together with zinc oxide.

Known is the "Method for Processing Electric Arc Furnace Dust" (Patent No. 2653394 (Russia) class C22B 19/00, 19/38 dated 08.05.2018), which includes the operations of mixing, pelletizing, sublimation of zinc, and hydrometallurgical processing of zinc-containing clinker. Electric arc furnace dust is mixed before pelletizing with a material containing calcium oxide in an amount that ensures the addition of calcium oxide in an amount of 70-110% of the content of iron oxide (Fe ₂ O ₃ ) in the dust, which is part of zinc ferrite (ZnO×Fe ₂ O ₃ ), and coke in an amount of 1-2% by weight of the said dust. The invention makes it possible to reduce the consumption of coke breeze, increase the extraction of zinc into solution, and lead into sublimates. Lead and chlorine and fluorine compounds pass into sublimates, zinc remains in the clinker in a form soluble during leaching. The disadvantage of this method is the presence of a two-stage process, in which at the pyrometallurgical stage it is not zinc oxide that sublimates, but harmful impurities, and the zinc itself is extracted at the hydrometallurgical process.

Known is the "Method for Waelz Treatment of Oxidized Zinc-Containing Materials" (Patent No. 2516191 (Russia) class C22B 19/38 (2006.01); C22B 7/00 (2006.01)), which includes feeding oxidized zinc-containing materials with coke as a solid carbonaceous reducing agent into a rotary tubular furnace and subjecting them to Waelz treatment with the supply of blast in the form of a steam-air mixture into the temperature zone of 1050-1150°C with a steam content in the mixture of 14-25%. Due to the supply of steam into the furnace in the temperature zone of 1050-1150°C, an endothermic reaction of C + H ₂ O → CO + H ₂ occurs, which ensures an increase in the reducing potential in the furnace atmosphere. increases the extraction of lead from the zinc-containing material. The disadvantage of the method is the lack of effect on other harmful impurities, contained in zinc-containing material, such as Na ₂ O, K ₂ O, SO ₃ , Cl, F.

The closest in technical essence and achieved effect to the claimed invention is a method for removing excess acidic and alkaline oxides from Portland cement clinker, consisting of maintaining in the raw mix a molar ratio of SO ₃ /(Na ₂ O + K ₂ O) ≥ 1 (Javed I. Bhatty.; Role of Minor Elements in Cement Manufacture and Use, Portland Cement Association, Skokie, Illinois 1995, p. 24-25.). When this ratio is maintained, Na ₂ SO ₄ and K ₂ SO ₄ are formed in the raw mix during firing, which sublimate to a temperature of 1100 °C. Due to the organization of suction of a portion of the gaseous combustion products through a bypass at a temperature of 1200 °C, these salts are removed from the firing zone, ensuring their low content in the firing products (Portland cement clinker).

In addition to the above oxides ( _Na2O , _K2O , _SO3 ), other elements such as Cl, F, Pb are also present in the dust of arc steel furnaces, which, when sublimated together with zinc, pollute it, reducing the quality of the zinc sublimate. To purify the zinc sublimate, manufacturers are forced to use hydrometallurgical processing, which removes soluble salts from the zinc sublimate. However, insoluble impurities such as Pb are not removed from the zinc sublimate.

The technical result of the present invention is the creation of a method for the pyrometallurgical extraction of zinc from arc steel-smelting furnace dust, ensuring an increase in the quality of zinc sublimation at the stage of pyrometallurgical processing without the use of hydrometallurgical processing.

The specified technical result is achieved in that in the method of pyrometallurgical extraction of zinc from electric arc furnace dust, including chemical analysis of electric arc furnace dust, mixing of electric arc furnace dust, solid carbonaceous reducing agent and flux, joint milling of the mixture, its agglomeration by pressing, Waelz briquettes of the mixture with the supply of blast in the form of a steam-air mixture with a steam content in the mixture of 14-25%, characterized in that the composition of the flux is determined according to the data of chemical analysis of the electric arc furnace dust with the introduction of acidic or basic oxides before mixing the raw mixture to a level ensuring the fulfillment of the ratio (SO ₃ + Cl + F) / (Na ₂ O + K ₂ O) ≥ 1, while the steam-air mixture is introduced into the temperature zone of 1000 ° C and part of the sublimation is removed from rotary kiln to a temperature of 1100°C.

By ensuring that the ratio (SO ₃ +Cl+F)/(Na ₂ O+K ₂ O)≥1 is met in the flux, compounds of Na ₂ SO ₄ , K ₂ SO ₄ , NaCl, KCl, NaF and KF that easily sublimate to a temperature of 1100°C are formed in the raw mixture during the firing process, and by introducing steam, the reducing potential of the furnace atmosphere increases, allowing the PbO contained in the dust to be reduced to Pb and converted into sublimation to a temperature of 1100°C, and by removing part of the sublimation to a temperature of 1100°C, these compounds are removed from the firing zone. Since zinc begins to sublimate above a temperature of 1100°C, the content of the indicated harmful impurities in the zinc sublimation is significantly reduced.

When testing the claimed method, a chemical analysis of the initial dust from electric arc furnaces is first performed, as shown in Table 1.

Table 1. Chemical analysis data of the initial dust from electric arc furnaces Name of oxide Content, mass % Standard error, % Element name Content, mass % Standard error, % ZnO 38.14 0.24 Zn 30.64 0.20 _{Fe2O3 ​} 23.51 0.21 Fe 16.44 0.15 CaO 7.54 0.13 Ca 5.39 0.09 _SiO2 4.40 0.10 Si 2.05 0.05 _K2O 4.09 0.10 K 3.39 0.08 Cl 3.94 0.10 Cl 3.94 0.10 _Na2O 3.74 0.29 Na 2.78 0.21 PbO 3.59 0.09 Pb 3.34 0.09 MnO 2.88 0.08 Mn 2.23 0.06 MgO 2.47 0.08 Mg 1.49 0.05 SO ₃ 2.38 0.08 S 0.95 0.08 _CO2 1.42 0.23 C 0.39 0.06 _{Al2O3 ​} 0.89 0.04 Al 0.47 0.02 CuO 0.29 0.01 Cu 0.23 0.01 _{P2O5 ​} 0.26 0.01 P 0.11 0.01 _{Cr2O3 ​} 0.23 0.01 Cr 0.16 0.01 _TiO2 0.14 0.01 You 0.082 0.004 _SnO2 0.056 0.004 Sn 0.044 0.003 NiO 0,013 0.003 Ni 0,010 0.002

Based on the chemical analysis data, the (SO ₃ +Cl + F)/(Na ₂ O + K ₂ O) ratio was calculated to be (2.38 + 3.94 + 0)/(3.74 + 4.09) = 0.807. Based on the chemical analysis results, a calculation was made and a flux consisting of CaSO ₄ in an amount of 2.74% was added to the raw material mixture, while the SO ₃ content in the raw material mixture was 4%, and the (SO ₃ +Cl + F)/(Na ₂ O + K ₂ O) ratio was equal to 1.014. After the flux was added, the raw material mixture consisting of arc furnace dust with carbon-containing additives (coke breeze) in an amount of (0.1-0.3): 1 to the weight of the zinc-containing material and flux was homogenized by grinding them together to a specific surface area of at least 3000 cm ² /g. Water was added to the homogenized mixture in an amount of 8% over 100% and the mixture was pressed at a pressure of 50 MPa. The initial dust of arc steel-smelting furnaces was prepared in the same way without the introduction of flux.

Briquettes of the initial dust of electric arc furnaces and the raw mix of the initial dust of electric arc furnaces and flux were heated in a Tamman furnace to a temperature of 900°C. The sublimate was collected by depositing it on a cold copper plate for 15 minutes. Then, heating was performed to a temperature of 1000°C, at which time steam was supplied to the reaction zone of the furnace for 15 minutes. After the introduction of steam, the temperature in the furnace rose to a temperature of 1350°C and the sublimate was also collected for 15 minutes. The sublimates were subjected to chemical analysis. The data of the chemical analysis of the sublimates of the initial dust of electric arc furnaces and dust of electric arc furnaces with flux at 900°C are given in Table 2.

Table 2. Chemical analysis data of sublimates at 900°C Electric arc furnace feed dust Arc furnace dust with flux Name of oxide Content, mass % Standard error, % Element name Content, mass % Standard error, % ZnO 68.3 0.23 ZnO 20.8 0.22 _K2O 7.3 0.10 _K2O 17.8 0.09 Cl 7 0.10 Cl 18.2 0.10 _Na2O 6.7 0.5 _Na2O 15.7 0.20 PbO 6.4 0.07 PbO 14.3 0.07 SO ₃ 4.3 0.08 SO ₃ 13.2 0.06

The data of chemical analysis of sublimates of the initial dust of electric arc furnaces and dust of electric arc furnaces with flux at 1350°C are given in Table 3.

Table 3. Chemical analysis data of sublimates at 1350°C Electric arc furnace feed dust Arc furnace dust with flux Name of oxide Content, mass % Standard error, % Element name Content, mass % Standard error, % ZnO 61.0 0.24 ZnO 95.4 0.21 _K2O 9.5 0.12 _K2O 0.6 0.11 Cl 9.7 0.13 Cl 0.8 0.12 _Na2O 9.1 0.55 _Na2O 0.5 0.26 PbO 7.4 0.09 PbO 1.4 0.07 SO ₃ 3.3 0.08 SO ₃ 1.3 0.06

The test results show that the introduction of flux, determined by the patented ratio, and steam into the reaction zone of the furnace makes it possible to increase the removal of harmful compounds and increase the ZnO content in the sublimation from 61% to 95% at a Waelz temperature of 1350°C.

Claims (1)

A method for the pyrometallurgical extraction of zinc from electric arc furnace dust, comprising chemical analysis of electric arc furnace dust, mixing of electric arc furnace dust, solid carbonaceous reducing agent and flux, joint milling of the mixture, agglomeration thereof by pressing into briquettes, Waelz-coating of the briquettes in a rotary kiln with blast feed in the form of a steam-air mixture with a steam content in the mixture of 14-25%, characterized in that the composition of the flux is determined based on chemical analysis of the electric arc furnace dust with the introduction of acidic or basic oxides before mixing the raw mixture to a level ensuring the fulfillment of the ratio (SO ₃ + Cl + F) / (Na ₂ O + K ₂ O) ≥ 1, wherein the steam-air mixture is introduced into the temperature zone of 1000 ° C, the temperature is increased to 1100 ° C and part of the sublimation containing easily sublimable compounds is removed from the rotary kiln, after which the temperature in the rotary kiln is raised to 1350°C and the sublimation is collected.