Method of arc-furnace dust recovery

FIELD: metallurgy.

SUBSTANCE: arc-furnace dust is agglomerated together with crushed carbon reducing agent and binder material in the form of pellets. The latter are dried, heated and roasted in rotary kiln together with solid reducing agent lumps at temperature of discharged materials of 700-1000°C, gases are cooled and dust bearing zinc and lead sublimates is caught therefrom. Note here that, prior to agglomeration, arc-furnace dust is premixed with lime-bearing material and crushed carbon reducing agent in amount 1.5-2 times higher than stoichiometrically necessary content of carbon for reduction of iron, zinc and lead oxides. Mix is damped to water content of 8-11% and cured for 1-3 hours while obtained pellets are loaded into kiln together with solid carbon reducing agent lumps in amount of 200-500 kg per ton of arc-furnace dust, reducing agent lump size making 20 mm.

EFFECT: higher yield of zinc and iron metallisation.

4 cl, 2 tbl, 1 ex

 

The invention relates to a method of preparation of raw materials for metallurgical treatment.

A method of refining iron - and zinc-containing wastes of metallurgical industries, including electric arc furnace dust furnaces. It includes pelletizing or briquetting, followed by reduction of oxides of iron and zinc, as well as metallized iron koskovich materials in rotary tube furnaces (see Ravich BM, Okladnikov VP, Ligach V.N., Minkowski M.A. Comprehensive use of raw materials and waste, Moscow, Chemistry, 1988, pp.92-94). Recovery processes occur due to carbon, coke or anthracite, served in a furnace in Kuskovo form together with the pellets or briquettes.

The disadvantages of this method are:

- low content of zinc oxide in caught sublimates due to the pollution of coal or coke dust;

- the need for long-term aging at temperatures of recovery due to the fact that the gas penetrates from the surface of the pellet to the center by the relatively slow diffusion through the pores.

Closest to the claimed method known technical solution is the method of purification of zinc and recovery (metallization) of iron oxide waste (EN 2240361, C22B 1/14). The main features of this method are:

- heated waste before briquetting in motivational tubular furnace to 550-1000°C;

- briquetting of waste together with crushed stone (brown) coal particle size of 3-5 mm;

- the burning of the briquettes in the flow tube furnace with burners installed from the download at the temperature descending briquettes 700-1000°C;

- maintaining the velocity of the gases in the furnace, reduced to normal conditions, 0.3-1.0 m/s;

- the cooling of the exhaust gases and the recovery from them of zinc;

the cooled combustion gases from the furnace, and the use of heat products of combustion to preheat the charge before briquetting.

The disadvantages of this method are:

- no special additives, which allow to obtain briquettes that can withstand contact with hot flue gases without destruction;

- the absence of lump carbonaceous reductant that is loaded with briquettes in the oven, does not allow to create a sufficient reduction potential for the metallization of iron and its contents in a paged briquettes will not exceed 75%;

- low degree of removal of zinc due to incomplete recovery of ferrite and silicate of zinc;

low content of metallic iron briquettes discharged from the furnace, does not allow to use them for direct download in the steel units, reducing consumer costs.

An object of the invention t is aetsa increase the degree of extraction of zinc from waste steel production and getting the product to the degree of metallization of iron not less than 75%, suitable for loading into the furnace instead of part of the scrap.

The specified technical task is achieved by a known purification method from zinc and recovery (metallization) of iron dust electric arc furnaces, which consists in sintering dust electric arc furnaces together with crushed carbonaceous reducing agent and a binder material, drying the obtained briquettes or pellets, heating and annealing in a tube furnace at a temperature paged briquettes or pellets 700-1000°C, cooling, dust-Laden gases, trapping of dust particles containing zinc and lead sublimates, according to the claimed invention before the sintering dust the electric arc furnace method work or briquetting the mixture add lime-containing material and comminuted carbonaceous reducing agent in excess of the stoichiometric required carbon content for full recovery of iron, zinc and lead in 1,5-2,0 times, the mixture is moistened to a water content of 8-11% and incubated for 1-3 hours, and the resulting briquettes or pellets after drying together with lumpy carbonaceous reductant size 0-20 mm in the number of 200-500 kg per tonne electric arc furnace dust furnaces load in a rotating oven.

Lime-containing material added to Koli is este, providing the ratio of CaO/SiO2=1,3-2,2 unit briquettes or pellets discharged from the furnace.

As the lime-containing material used lime content of active CaO not less than 80% or disintegrating slag electric furnace steelmaking with CaO content of not less than 50%.

Additive to the mixture of lime-containing material provides high strength raw pellets or briquettes due to the formation of the structure of the granules on the basis of the newly formed crystals of hydrate of calcium oxide by the reaction:

CaO+H2O=Ca(OH)2.(1)

Granules associated with the hydrate water is more stable under intense heating that takes place at their contact with hot flue gases, the temperature of which reaches 600-700°C. to Reduce the temperature of exhaust gases is not possible, otherwise a vaporous zinc will begin to condense on the furnace lining. In the absence of lime water pellets or briquettes are free and when heated rapidly evaporates with the formation of high pressure in the pores, resulting in the destruction of the granules. Dust is Yosida of the rotary kiln, enters the gas purification system along with the action, reducing the concentration of zinc in the product discharged from the filters, and, accordingly, devaluing them.

Reaction (1) proceeds with evolution of heat and increased the size of the particles of the hydroxide of calcium compared with calcium oxide. If these processes take place after forming the structure granules, they will lead to their destruction. Therefore, the mixture with lime-containing materials should be kept at room temperature until completion of the reaction (1). The velocity is determined by the size and type of lime-containing material. When the optimal size to obtain pellets, 0-0,074 mm, the hydration of calcium oxide does not exceed 1 hour. At the same time in the manufacture of briquettes, it is permissible to use a larger grinding 1-3 mm. In this case, the time of reaction is increased to 3 hours.

Experience in the production of pellets and briquettes shows that the optimum moisture content of the mixture is in the range of 8-11%. When humidity less than 8% water is in the microscopic pores of the particles of electric arc furnace dust and doesn't leave on their surface. In this case, there is no capillary force of the compression of the grains, which is the basis of formation of briquettes or pellets and their strength. In the case of excessive moisture, more than 11%, the particle e is crotalariae dust and lime-containing material are separated by water droplets, the frame is destroyed, and the granules lose their strength, they can be transported on highways and load in a rotating oven.

In addition to the lime-containing material in the mixture for the manufacture of granules add the crushed carbonaceous reducing agent, which may be coke or coal. The amount of carbon in the pellets should ensure complete reaction processes:

C+2FeO=2Femet.+CO2(2)

3C+2Fe2O3=4Femet.+3CO2(3)

C+2ZnO=2Znpandp+CO2(4)

C+2PbO =2Pbpandp+CO2(5)

It is found experimentally that for the complete filling of the pores of briquettes or pellets reducing gas produced by the reaction:

C+CO2=2CO,(6)

which is the main reagent processes (2-5), you need the excess content of solid carbon on the stoichiometric recovery of oxides of iron, zinc and lead metal to 1.5-2.0 times. At a lower content ratio of CO/CO2in the pores of the granules is less than required for metallization of iron and voshon zinc, but at a higher - unspent solid reducing agent prevents the sintering of iron ore dust particles and granules lose their strength. These reasons lead to the fact that the output for the claimed interval content of the solid carbonaceous reducing agent is associated with a decrease in the concentration of zinc sublimates and quality metallized product.

The use of solid carbon reset is the only representative in powdered form, Sanatana in pellets or briquettes, in excess of the stoichiometric 1.5-2.0 times, it is not possible to create an atmosphere in the furnace with a high recovery potential. Therefore, the pores of the pellets or briquettes after the initial recovery of the oxides of zinc and iron, occurring at high partial pressure of gases inside the granules will begin to penetrate oxidizing gases, which are products of combustion of natural gas fed to the burner. Zinc, evaporated at the initial stage of active restoration is removed and the metallic iron is oxidized to carbon dioxide and water vapor. To achieve high degrees of voshon zinc and iron metallization together with pellets (briquettes) loaded lumpy carbonaceous reducing agent in the form of coke or coal. The solid carbon reductant gasified carbon dioxide by the reaction of Boudoir and water vapor by the reaction of water gas. The resulting carbon monoxide and hydrogen have a high recovery potential, and will provide almost complete Vashon zinc and iron metallization. In addition, the presence of lump carbonaceous reductant in the form of coke or coal in the furnace chamber will provide oxygen combustion air entering through leaks docking station fixed heads and rotary drum stove in question is ransta. The lack of oxygen in the depths of presuposes layer, and its surface is to guarantee the conservation of metallic iron in the pellets (briquettes). Download bulk reductant in the quantity < 200 kg per ton of pellets, insufficient for burning all the oxygen generated in the furnace chamber rotary kiln, and will reduce the degree of metallization of iron. Enter bulk reductant more than 500 kg per ton of pellets is not required to maintain a high reduction potential of the gas phase and impractical because of the additional costs.

The particle size lump of solid reducing agent is in the range of 0-20 mm, Use larger material will increase the time of its gasification due to the reduction of the reaction surface and will require unreasonably high flow. The charging smaller carbon reductant will lead to increased dust and contamination zinc sublimates.

As the lime-containing material was used lime pushonka with CaO content of more than 80%. A lower CaO content is associated with the presence of impurities of oxides of silicon, aluminum, iron and other metals, which are not binding elements and lead to lower strength wet and dry briquettes. Less durable briquettes of razrushaetsya kiln dust, which pollutes zinc sublimates and reduces the productivity of the furnace.

As the lime-containing material is highly basic slag electric furnace steelmaking with CaO content not less than 55%. Lower content of calcium oxide in the slag than lime valid, as cooling samoraspadayutsya slag active compounds calcium aluminosilicates having a high specific surface area and astringent properties.

Additive lime-containing materials must ensure that the basicity of the sintered pellets or briquettes in the range of CaO/SiO2=1,3-2,2 unit This allows you to melt metallized pellets or briquettes as in the blast furnace and steel melting furnaces, without the introduction of additional charge of fluxing additives.

An example of implementing the inventive method. To obtain briquettes used the following scrap materials:

dust steel-making furnaces, captured in bag filters complex arc furnace EAF-80 metallurgical plant. Akhmerova;

- solid carbonaceous reducing agent in the form of dropout metallurgical coke of JSC " NTMK " size 20-0 mm;

the hydrated lime.

The chemical composition of these components are shown in table 1.

When calculating the contents of the components in the charge took the excess content of the project for carbon over the stoichiometric - of 1.75 times, and the basicity of the leaving the furnace briquettes is 1.75%

Table 1.
The chemical composition of the components of the charge to obtain pellets of EAF dust with the addition of a binder, ground coke and lime
№№ p/pMaterial typeThe chemical composition, mass %
FetotalFeOFe2O3CaOSiO2MgOZnOStotalCTV.PM PMAl2O3Amount
1Dust EAF-8043,73,558,58,210,02,57,90,61,03,3 1,597,0
2Cox1,0-1,50,97,50,5-0,580,0-the 3.894,7
3Lime0,3--80,00,51,2---of 17.5-99,5

Thus, the stoichiometric amount of carbon for the reactions (2-4) was 8.2 g per 100 g of dust. Taking into account the required and excess carbon in the coke, the amount of coke was equal to 17.9 g per 100 g of dust steel-making furnaces. To achieve the required basicity in charge must be added 13.5 g of lime per 100 g of dust steel-making furnaces. Equity component content in the charge is equal to:

dust DS is -80 - 76,1%;

- coke breeze is 13.6%;

- lime - 10,3%.

The mixture in a predetermined ratio of the components was moistened to a water content of 9% and were placed in a concrete pit for lime slaking. Wet the mixture was kept under stirring grab crane for 2 hours. Wet sustained the charge was bitterbal and after drying of the briquettes, which had the strength of 100 kg/briquettes were loaded in a rotating furnace with a length of 40 m and a diameter of 3 m together with lumpy solid carbonaceous reducing agent, which was the coke particle size 20-0 mm Consumption lump of solid carbonaceous reductant was 300 kg per 1 ton electric arc furnace dust furnaces. Regenerative firing in a rotary kiln was carried out at a temperature in the reduction zone and voshon zinc 1200°-1400°C. In the furnace, the zinc was recovered carbon coke. Volatile compounds of zinc vothonas in the gas phase, and then cooling gases zinc is condensed in the form of fine metal dust, oxidized by the false air in the ducts, the cooling and dust collecting devices, and then catch bag filters, forming a semi-finished product with a high concentration of zinc oxide, which is the raw material for further processing.

Discharged from the furnace material in the form of metallized pellets substantially free of zinc and had a temperature of 900°C. It was cooled in the drum to a temperature of 150-200°C. the cooled product by the method of dry magnetic separation has allocated the residual lump carbonaceous reducing agent in the non-magnetic fraction and metal briquettes - magnetic. Unused coke is returned to the process, and metallized pellets shipped to the consumer at the metallurgical plant.

The claimed method allowed us to obtain in bag filters zinc intermediate with ZnO content=50-70%, suitable for the production of zinc electrolytic method and sputter briquettes or pellets with a degree of metallization of more than 75%, corresponding to modern requirements to the iron-containing raw materials for metallurgical processing. The benchmarking process in the present method and the closest analogue is given in table 2.

Table 2.
Comparative figures the closest analogue and the proposed method
The closest analogue (EN 2240361 C22B 1/14)The claimed method
123
Fe total) - charge, %4040
The degree of metallization of iron, %7595
ZnO (mixture), %0,66,0
ZnO (product), %0,010,01
Specific consumption of natural gas, m3/t charge5050
The specific consumption of solid reductant, kg/t charge100300

123
The content of ZnO in the dust, caught from the gases leaving the kiln, %5070
Loss of material return for recycling, %55

From the above example it follows that the inventive method allows to process dust electric melting furnaces, the original content of zinc which is 10 times tacos is second in the closest analog. As in the closest analogue, and in the present method zinc in foods firing virtually absent, and the degree of metallization of iron and zinc concentration in caught sublimates significantly higher in the invention.

1. The method of disposal of electric arc furnace dust furnaces, including the agglomeration of dust electric arc furnaces together with crushed carbonaceous reducing agent and a binder material in the form of pellets or briquettes, drying the obtained pellets or briquettes, heating and firing in a rotary kiln together with lumpy solid carbonaceous reducing agent at a temperature of downloadable materials 700-1000°C, gas cooling and trapping of dust particles containing zinc and lead sublimates, characterized in that the electric arc furnace dust furnaces before sintering mixed with lime-containing material and comminuted carbonaceous reducing agent in excess of the required stoichiometric carbon content for the recovery of oxides of iron, zinc and lead 1.5-2.0 times, the mixture is moistened to a water content of 8-11%, incubated for 1-3 h, and the resulting pellets or briquettes are loaded into the furnace together with lumpy solid carbonaceous reductant size 0-20 mm in the number of 200-500 kg per ton of dust electrostatically the furnaces.

2. The method according to claim 1, characterized in that the lime-containing material added to ensure relationships CaO/SiO2the pellets or briquettes discharged from the furnace, equal to 1.3 to 2.2%

3. The method according to claim 1, characterized in that as the lime-containing material used lime with active CaO content not less than 80%.

4. The method according to claim 1, characterized in that as the lime-containing material used samoraspadayutsya slag electric furnace steelmaking with CaO content not less than 55%.



 

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FIELD: metallurgy.

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FIELD: technological processes, mining.

SUBSTANCE: invention may be used for processing of zinc-containing wastes of metallurgy and mining production, in particular, zinc-containing blast furnace, converter, electro-steel-smelting dusts and slags, and also zinc and iron containing oxide wastes of ferrous and non-ferrous metallurgy. Method of zinc-containing dusts and slags processing in metallurgy and mining production includes stacking of dusts and slags in ash-and-slag collectors and their processing. Processing is performed by means of disintegration of initial raw material into rotation-pulsation-cavitation device of continuous action with ratio of solid to liquid of 1:4 and at excessive pressure of 5 atmospheres at the inlet to device. Further supply of material into flotator with extraction of zinc, as harmful impurity in foam product and chamber product sent to gravitation classification. in which fine and large-scale fractions are extracted and sent separately to wet magnetic separation in separators with permanent magnets with preparation of conditioned iron-containing concentrate purified from zinc and final tailings.

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1 dwg

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EFFECT: production of metallised pellets, meeting requirements of metallurgical industry, and of commodity zinc sublimates.

2 cl, 1 tbl, 1 ex

FIELD: processing finely-dispersed iron-and-zinc-containing wastes of metallurgical process and byproducts of coke and byproduct process; ferrous and non-ferrous metallurgy.

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EFFECT: high intensity of zinc sublimation and iron reduction processes; increased degree of removal of sulfur; increased degree of metallization of finished product.

7 tbl, 1 ex

FIELD: ferrous metallurgy, possibly processing of iron and zinc containing materials being waste products, for example dusts and alloys of gas scrubbers of open hearth and blast furnaces, of converters.

SUBSTANCE: method comprises reduction annealing at presence of reducing agent in rotary tubular furnace without air access in controlled-temperature mode for producing metal plated iron-containing product and zinc product. Mixture of initial material and reducing agent is preliminarily processed at temperature no less than 400°C till humidity content no more than 0.05% and then such mixture is fed into rotary tubular furnace. Reduction annealing in such furnace is realized due to contact free heating with use of heat exchanger mounted in said furnace due to supplying combustion products into said heat exchanger. Zinc condensate is trapped and cooled for producing zinc product in the form of metallic zinc.

EFFECT: possibility for producing zinc product in the form of metallic zinc at lowered consumption of reducing agent.

2 cl, 1 tbl

FIELD: complex usage of raw materials in ferrous metallurgy, namely processing blast furnace production slimes containing iron, zinc, sulfur and other metals, possibly extraction of harmful zinc impurities preventing participation of iron-containing raw materials in metallurgical conversion from slimes of scrubbing at blast furnace production.

SUBSTANCE: zinc extraction is realized by magnetic separation method. In order to convert zinc ferrites and zincates to non-magnetic fraction, magnetic separation is performed in magnetic field with intensity up to 96 kA/m.

EFFECT: improved efficiency of zinc extraction from blast furnace production slimes due to lowered mass content of zinc in magnetic product.

1 tbl

FIELD: ferrous and nonferrous industry; methods of reprocessing of zinc-containing waste products.

SUBSTANCE: the invention is pertaining to the field of ferrous and nonferrous industry, in particular, to the method of reprocessing of zinc-containing waste products of metallurgical production and may be used in ferrous and nonferrous metallurgy. The method provides for mixing of the wastes with a carbon reducing agent, a high-temperature treatment of the gained mixture in the roasting furnace, withdrawal of zinc and trapping sublimates with production of zinc oxides. The gained mixture is granulated with production of granules of 4-10 mms sizes and humidity of 11-15%. The high-temperature treatment of the mixture is conducted at temperatures of 910-1100°C for 1-2 hours. The trapping sublimates of zinc conduct by withdrawal of 70-80 % from the total volume of the zinc-containing dust-gaseous mixture from the reaction zone of the roasting furnace. The rest volume of the dust-gaseous mixture is withdrawn from the cold end of the roasting furnace. From the withdrawn from the cold end of the roasting furnace dust-gaseous mixture separate the zinc-iron-containing dust and return it to be used in a sub-charge for the initial granulated mixture and the zinc-free granules are directed into agglo blast-furnace production. The invention allows to reach the heightened degree of extraction of the commercial zinc product with a minimal share of impurities and also to reduce the harmful effect of the wastes on environment.

EFFECT: the invention allows to obtain the heightened degree of extraction of the commercial zinc product with a minimal share of impurities, to reduce the harmful effect of the wastes on environment.

3 cl, 1 tbl, 3 ex

FIELD: non-mechanical processing of nonferrous metals, in particular, processing of zinc-containing materials.

SUBSTANCE: method involves heating zinc scale lumps of 50-300 mm size to temperature of 540-560 C.

EFFECT: increased efficiency by maximal utilization of zinc separated from scale in hot zincing process.

1 tbl

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