RU2799008C1 - Method for thermal metal smelting of iron alloys with vanadium, silicon and aluminum from charge material obtained from ash waste - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention can be used in production of iron alloys with alloying elements by “on the block” out-of-furnace melting method. The charge is prepared and loaded with an ignition mixture into a vessel for smelting, the entire surface of the fixed mass of the charge is isolated with a bulk heat-resistant layer, the reaction process is initiated, melting is carried out in this insulating layer, in which the bulk heat-resistant material of the insulating layer is used with a fraction of -10+1 mm, moreover, on the upper surface of the charge array, this layer is formed with a thickness of 72-78% of the charge array height, on the side surfaces - with a thickness of 40-48% of the width or diameter of the charge array, and at the same time, the dimensions of the charge array are increased in diameter to 55-100 cm and in height up to 80-130 cm 3 with a corresponding increase in the volume of the melted charge mass up to 0.19-1 m³ and an increase in the mass of the melted charge up to 0.3-1.8 tons.

EFFECT: invention allows smelting iron alloys from charge material obtained by enrichment of ash waste from thermal power plants while maintaining environmental cleanliness and the absence of smoke, dust and other emissions during smelting.

3 cl, 3 tbl, 1 ex

Description

The invention relates to metallurgy and can be used in the production of iron alloys with alloying elements by the metal-thermal method, in particular out-of-furnace melting "on the block".

Known methods of carbothermic and metal-thermal smelting of iron alloys, ferroalloys in an electric furnace by reducing metals from oxides with carbonaceous or metal reducing agents: aluminum or silicon [Kablukovskiy A.F. Production of electric steel and ferroalloys. - M.: ICC "Akademkniga", 2003. - 511 p.]. At the same time, carbothermal processes are initially used to obtain the bulk of iron alloys, and the resulting steels are subsequently alloyed with vanadium, silicon, manganese and other chemical elements introduced into the melt using ferroalloys and master alloys. High-performance carbothermal electric furnace smelting with high energy costs leads to environmental pollution, emissions of CO ₂ (increased "carbon footprint"), nitrogen oxides and volatile oxide impurities in the form of gas and smoke.

The classic disadvantages of high-performance industrial methods, including carbothermal or metallothermic reduction of iron in the form of alloys, are the use of expensive electric furnace and smoke and dust extraction equipment, the cost of expensive linings and high power consumption for smelting.

Known high-performance carbothermal, metal-thermal methods for smelting iron alloys, for example with vanadium and silicon, basically have difficulties in directly melting dispersed charge materials with a fraction of less than 0.5 mm, which are, for example, concentrates obtained from fly ash. The melting of such dispersed materials is inefficient due to the increased escape of dusty charge materials and reduced metal particles. The resulting briquettes or ash pellets can crumble during transshipment, during ore-thermal arc melting, as a result of which small particles of raw materials in the form of dust are carried out by convection currents from the melting space. Restoration using coal, coke and other carbonaceous substances, with the associated energy costs, creates an increased carbon footprint from smelting. Silicothermal electric furnace methods require the cost of ferrosilicon and electricity that are becoming more expensive. For the industrial implementation of the above known methods, expensive gas and dust collection systems and gas cleaning equipment are required to comply with environmental standards.

In metallurgy, less productive are also used - out-of-furnace aluminothermic methods for producing various alloys with iron, ligatures and other special alloys, commercially pure metals by melting "on a block" (or with pouring) [Lyakishev N.P. etc. Aluminothermy. - M.: Metallurgy, 1978. - 327 p.].

In the method for smelting a vanadium-containing alloy (an alloy of iron with vanadium and silicon) by an out-of-furnace aluminothermic process [RF patent No. melts, release of slags and cooling of the vanadium-containing alloy. In this method, converter vanadium slag is used as a vanadium-containing component; during preparation, a mixture of lime and magnesite is introduced into the mixture in an amount of 5-20% by weight of the input aluminum while maintaining the ratio of calcium oxides to magnesium oxides in it within 1: (1-0 ,5), while the entire mixture is heated to a temperature of 200-550°C before being loaded into the melting hearth. In the examples of this method, very small masses of charge components are given, in the amount not exceeding 300 grams (0.0003 tons). This does not confirm the effectiveness of the method at the industrial level, in which it is required to obtain masses of ingots of several tens, hundreds or thousands of kilograms per 1 heat. When scaling the method to an industrial level, increasing the mass of the charge, for example, by 100 and 1000 times, additional technological problems arise in terms of the smelting hardware and significant adjustments to the charge compositions. Converter vanadium slag is an expensive product, because its production is costly and multi-stage, starting with the extraction and enrichment of iron ore containing vanadium, then blast-furnace smelting of vanadium pig iron with the necessary preparatory processes (preparation of charge, carbonaceous reducing agent, fluxes), and ending with converter smelting.

The above method [RF patent No. 2374349] and most other out-of-furnace methods carried out in melting lined hearths or crucibles, mainly in open air, give dust and gas emissions, smoke, worsening working conditions and the environment. To maintain the environmental friendliness of the methods of metal-thermal mining smelting of iron alloys (with a prevailing mass fraction of iron), smoke and dust-catching equipment is used “per block” and expensive linings are used.

There are also known methods of metal-thermal smelting "on a block" in closed, evacuated chambers [RF patents No. 2269585 and No. 2034058], while there are no dust and gas emissions, but vacuum melting equipment has a very high cost and complexity of operation.

In the method [RF patent No. 2465361], the exothermic charge is loaded into a thin-walled cylinder, which is pre-installed in the smelter shaft coaxially with its perforated walls. The space between the thin-walled cylinder and the perforated walls of the shaft is filled with granular gas-permeable refractory material, then the thin-walled cylinder is removed, and the charge is also filled from above with granular gas-permeable refractory material. After that, the start of an exothermic reaction is initiated, during which gases are removed from the reaction zone through a granular gas-permeable refractory material and perforated walls of the melting hearth shaft, and after the reaction is completed and the slag is discharged, the hearth is dismantled and the ingot is separated from the slag residues.

Despite the fact that in this method the perforated hearth allows minimizing the pressure of gases (drainage removal of gases is provided), emissions of molten charge through the perforation holes and from the upper open part of the hearth are not excluded, which is confirmed by the practical use of the method with large masses of charge with a thermal capacity of more than 600 kcal. /kg (more than 2512 kJ/kg), especially if in any of the sections of the charge or lining there is an increased content of moisture, gas-forming substances (organic or other). It is very difficult to achieve a uniformly distributed pressure of gases escaping through holes in the hearth walls during metallothermic melting, and a sharp breakdown of gases and melt is possible through one or a group of holes. With an increase in the volumes of melted alloys, the use of a perforated hearth does not provide labor safety conditions and eliminate emissions. In addition, this method and the hearth do not allow for prompt granular relining - backfilling with a layer of granular gas-permeable refractory material. Since the hearth in the form of a hollow cylinder is installed on a refractory base (hearth), when dismantling the hearth - extracting the products of smelting, this granular material crumbles. And for the next heat, it must be collected and again poured into the hearth, installed on a base of refractory material. This process of preparing the hearth for melting is time-consuming and complex.

The closest and selected for the prototype is the method of metallothermic melting [RF patent No. 2406767], which includes the preparation of the charge, loading the charge into a container for melting with its isolation with a loose refractory layer, initiating the reaction process, the prepared charge array is fixed from spilling and with the ignition mixture loaded into a container for melting, while the loose refractory layer isolates the entire surface of the fixed mass of the charge. The prototype for the smelting of special alloys with iron (ferroalloys) indicates the use of expensive ore concentrates - ilmenite and chromite. To increase the content of the leading elements in the alloys, in the charge according to this method, expensive additives of rutile and chromic anhydride are used. As raw materials, expensive ore concentrates with expensive exothermic additives are used (to increase the thermality of the charge and increase the degree of extraction of the leading elements). These additives are barium peroxide and chromic anhydride - harmful to the environment and working conditions.

The main disadvantage of the prototype method for its implementation at an industrial high-performance level for smelting iron alloys with other chemical elements is the use of small amounts of charge, the mass of the charge is not more than 0.25 tons due to the rapid thermal expansion of heated air and other gases remaining in the intervals between particles of the filled refractory insulating layer (loose lining), and the lack of timely discharge of the increased pressure of these gases. With an increase in the volume of the charge over 0.16 m ³ , the mass of the charge over 0.25 tons, the thermal expansion of gases increases the gas pressure in the insulating layer during the smelting process, and loose lining is ejected from the melting tank (hearth) - sand with a fraction of 0.6- 3 mm, while there is a partial ejection of the molten charge and smoke and dust emissions. These are dangerous and unecological conditions, and the results of smelting for the metallurgical extraction of the alloy are unsatisfactory.

The technical problem to be solved by the present invention is to increase industrial efficiency - the productivity of the method of smokeless metal-thermal smelting of iron vanadium-, silicon- and aluminum-containing alloys from charge material obtained from ash waste generated from the combustion of coal from a thermal power plant, while maintaining environmental the purity of the method - the absence of smoke and dust emissions and emissions during melting.

To solve this technical problem, a method for metallothermic smelting of iron alloys with vanadium, silicon and aluminum is proposed, including preparation of the charge, loading the charge with the ignition mixture into a vessel for smelting with fixing the charge mass from scattering, isolating the entire surface of the fixed charge mass with a loose refractory layer, initiating reaction process, smelting in this insulating layer, in which the loose refractory insulating material of this layer is used with a fraction of -10 + 1 mm, and on the upper surface of the charge mass this layer is formed with a thickness of 72-78% of the charge mass, on the side surfaces - with a thickness of 40- 48% of the width or diameter of the mass of the charge, and the dimensions of the mass of the charge are increased in diameter up to 55-100 cm and in height up to 80-130 cm with a corresponding increase in the volume of the melted mass of the charge up to 0.19-1 m ³ and an increase in the mass of the melted charge up to 0 ,3-1.8 tons.

As a charge material, a concentrate obtained by enrichment of ash waste is taken, or unenriched ash waste is used as a charge material, which is subjected to oxidative roasting to be converted into charge material (of sufficient quality for smelting). Ash waste is generated at thermal power plants as a result of combustion of hard coal.

The method allows smelting an iron alloy with a high content of silicon and aluminum - ferrosilicoaluminum.

The technical result of the claimed invention lies in the fact that in the method of metal-thermal smelting of iron alloys with vanadium, silicon and aluminum, loose refractory material of the insulating layer is used with a fraction of -10 + 1 mm, and on the upper surface of the charge array this layer is formed with a thickness of 72-78% of the array height charge, on the side surfaces - with a thickness of 40-48% of the width or diameter of the charge array, and at the same time, the dimensions of the charge mass increase in diameter up to 55-100 cm and in height up to 80-130 cm with a corresponding increase in the volume of the charge mass being melted through to 0.19 -1 m ³ and an increase in the mass of melted charge up to 0.3-1.8 tons. As a charge material, a concentrate obtained by enrichment of ash waste is used, or as a charge material, ash waste subjected to oxidative roasting is used.

Increasing industrial efficiency - the productivity of the method is achieved by increasing the volume of melted charge from 0.16 m ³ (charge array diameter 54 cm, height - 70 cm, known from the prototype) to 0.19-1 m ³ (charge array diameter 55-100 cm, height - 80-130 cm) and an increase in the mass of the charge from 0.25 tons (according to the prototype) to 0.3-1.8 tons.

Maintaining environmental friendliness and increasing the industrial efficiency of the method is ensured through the use of an insulating layer of refractory material with a fraction of -10+1 mm. Such a fraction provides drainage of expanding heated gases from the charge being melted and prevents the removal of this layer of refractory material by gas pressure from the melting vessel (from the open upper part of the hearth). As a result, there are no refractory and melt emissions. At the same time, the restriction of the contact of the mixture being melted with air components remains (the melt is closed from the inflow of air from the outside), therefore, smoke is not formed during smelting, and there are no emissions of smoke and dust into the air atmosphere.

In the proposed method, as a feedstock for the production of charge material and smelting, ash waste from the combustion of coal from a thermal power plant is preferably used, the problem of processing and beneficial use of these wastes is becoming more and more urgent.

Table 1 shows the composition of the bottom ash, the concentrate obtained from these wastes, and the resulting iron alloys with vanadium and silicon. Iron-rich charge material - concentrate - is obtained by two-stage enrichment of these ash wastes. Enrichment is carried out by standard methods [Handbook for the enrichment of ores. – M.: Nedra, 1982]. The first stage of enrichment is hydrodynamic separation, the second is magnetic-gravity separation with further drying.

It is possible to use charge material obtained from ash waste of another origin (not only from burnt coals of thermal power plants) with a high content of iron, vanadium and silicon.

As a reducing agent, it is preferable to use inexpensive aluminum waste in the form of crushed chips and its screenings, which are difficult in classical recycling processing (when recycling, chips and its screenings are briquetted and usually remelted in rotary furnaces, often without sorting - they produce secondary aluminum ingots of low grades).

In the proposed method, for the formation of an insulating layer, as a bulk refractory material (refractory filling), one can use, for example, waste from own aluminothermic production - crushed slag resulting from previous out-of-furnace melts.

Thus, in the proposed method of smelting, it is possible to fully combine the beneficial use of industrial waste: charge material, reducing agent and refractories are taken from industrial waste.

In the proposed method, the use of expensive exothermic additives is excluded, because the heat generated during the aluminothermic reaction of oxides FeO, Fe ₂ O ₃ , SiO ₂ , V ₂ O ₅ with aluminum, which are in the charge mixture, is enough (with a margin) for a high-quality process of metal-thermal melting with the extraction of the necessary leading elements of the alloy at the level of 90-97%.

Table 1. Composition of ash ¹⁾ and concentrate obtained from this ash, and possible compositions of iron alloys smelted from these wastes

Component Component content in ash ¹⁾
and in concentrate ²⁾ , wt. % The content of components in the finished iron alloy with vanadium and silicon actual
in the initial complex ash sample ¹⁾ typical range
in concentrate ²⁾ typical
in concentrate ²⁾ extraction
elements
from 1 ton of concentrate
in alloy, kg typical content of elements
in 1 ton of alloy, kg typical element range
in finished alloy ²⁾ ,
mass. % Fe met. 1.6 7.1-8.0 7 68 Fe 815 Fe 80-83 Fe FeO 7.83 31.8-34.7 32.9 250 Fe _{Fe2O3 _} 8.02 32.2-35.1 33.1 227Fe _SiO2 45 6.5-8.2 8 36 Si 55 Si 4-7 Si V ₂ O ₅ 0.2 9.1-9.8 9.5 51V 75V 6-8V MNO 1.14 2.3-2.6 2.4 17 Mn 25 Mn 2-3 Mn _{Al2O3 _} 18.7 2.8-4.1 3.5 goes to slag
10 kg - residual Al from aluminothermy 15 Al 0.5-1.5Al CaO 6.02 0.9-2.1 1.3 goes to slag in slag - MgO 2.55 0.4-0.7 0.5 goes to slag in slag - _TiO2 1 0.2-0.3 0.2 into impurities and slag admixture - _Na2O 0.8 0.05-0.1 0.1 goes to slag in slag - _K2O 1.14 0.05-0.2 0.1 goes to slag in slag - WITH 4.29 0.1-0.5 0.2 into impurities and slag admixture - S 0.11 0.1-0.3 0.1 into impurities and slag admixture - Others, impurities 1.69 0.8-1.4 1.1 10 including Ti 15,
including Ti 1.5-3 others, TOTAL 100 - 100 670 1000 100

Notes: 1) Ash waste from the combustion of hard coals of CHPP.

2) The concentrate was obtained by two-stage enrichment of ash waste from the CHPP.

3) The sum of the mass fractions of useful elements V, Si and Mn (Mn as a useful impurity) is 12-18%.

To implement the proposed smelting method, a concentrate obtained by a two-stage enrichment of ash waste from the combustion of coal from a thermal power plant (option 1) and ash waste subjected to oxidative roasting (option 2) is used as a charge material. The chemical composition of both types of charge material obtained from fly ash is shown in Table 2.

Table 2. Charge components

Components Chemical composition, wt. % Description Charge material option 1
for smelting iron alloys
with vanadium
and silicon
– concentrate ¹⁾ 7.1-8.0 Fe, 31.8-34.7 FeO, 32.2-35.1 Fe ₂ O ₃ , 6.5-8.2 SiO ₂ , 9.1-9.8 V ₂ O ₅ , 2.3-2.6 MnO, 0.9-2.1 CaO,
0.4-0.7 MgO, 2.8-4.1 Al ₂ O ₃ , 0.2-0.3 TiO ₂ , 0.1-0.2 K ₂ O and Na ₂ O, 0.1- 0.4 C, 0.1-0.3 S, moisture, others - 0.8-1.4 Concentrate obtained by two-stage enrichment of ash waste from the combustion of hard coals from a thermal power plant option 2
for smelting ferrosilicoaluminum
– prepared fly ash ²⁾ 19.5 Fe ₂ O ₃ , 47 SiO ₂ , 0.2 V ₂ O ₅ , 1.15 MnO, 19.7 Al ₂ O ₃ , 6.2 CaO, 2.6 MgO,
1 TiO ₂ , 0.5 Na ₂ O, 1.1 K ₂ O, 0.25 C, 0.05 S, others - 2. No enrichment.
After oxidation firing at 1000°C for 3 hours to reduce the content of carbon, sulfur, moisture Technological aluminum shavings
and dropouts Aluminum shavings: Al not less than 92.5, 0.3-6 Mg, 0.2-5 Si, not more than:
0.4 Cu, 0.1 Zn, 0.03 Pb, 0.02% Sn;
aluminum waste
(aluminum can, etc.):
97 Al, 0.8 Mg, 0.2 Si, 0.6 Fe,
0.2 Cu, 0.7 Mn, 0.02 Zn, 0.8 C Crushed shavings of secondary aluminum, particle size 0.1-5 mm;
shredded aluminum waste
STO 74845470-2006,
particle size - 0.3-5 mm lime
(technical calcium oxide) 85-93 CaO, 3-5 MgO, 1.5-2 SiO ₂ , water of hydration - no more than 2%,
CO ₂ - no more than 4% Quicklime powder

Notes:

1) The chemical composition is indicated in interval values, since the enrichment of composition-averaged ash waste technologically gives a heterogeneous charge material in different enriched batches.

2) The chemical composition is indicated in average values for 5 samples; typical interval content of silicon dioxide 45-48%, iron oxides 19-21%.

Below is information on the amount of reducing agent required for smelting an iron alloy with vanadium and silicon, calculated per 1 ton of charge material - concentrate.

Concentrate component Content, Reducing agent,

(in 1 ton) kg (waste 93-96% Al), kg

Iron Fe met. 71 - 80 -

iron oxide FeO 318 - 347 83.7 - 91.3

iron oxide Fe ₂ O ₃ 322 - 351 114.2 - 124.5

silicon dioxide SiO ₂ 65 - 82 41 - 51.8

vanadium pentoxide V ₂ O ₅ 91 - 98 47.4 - 51

manganese oxide MnO 23 - 26 6.1 - 7

TOTAL 292.4 - 325.6.

For the smelting of 1 ton of iron alloy with vanadium and silicon from a concentrate obtained by two-stage enrichment of ash waste from the combustion of coal from a thermal power plant, the following charge composition is used:

kg mass. %

Ash waste concentrate 1410 – 1615 74 – 75

Aluminum shavings and screenings 436 – 486 22 – 23

Lime 60 - 90 3 - 4.

To reduce the thermality of the mixture, if necessary, it is possible to add to the ash concentrate, i.e. pre-calcined ash waste from the combustion of coal from a thermal power plant.

According to the proposed method, it is possible to smelt an iron alloy with a high content of silicon and aluminum - ferrosilicoaluminum - from unenriched ash waste from the combustion of coal from a thermal power plant, with the addition of iron scale and an excess of aluminum reducing agent.

Below is information on the amount of reducing agent required for the smelting of ferrosilicoaluminum, and the quantitative characteristics of the components in the resulting alloy (calculated per 1 tonne of unenriched calcined ash waste from a thermal power plant).

Component Content, Reducer Output Items

concentrate (in 1 ton) kg (waste 93-96% Al), kg into alloy, kg

iron oxide Fe ₂ O ₃ 195 70 133 Fe

silicon dioxide SiO ₂ 470 297 213 Si

vanadium pentoxide V ₂ O ₅ 2 1 1 V

manganese oxide MnO 11.5 3 8 Mn

calcium oxide CaO 62 - -

other 249.5 - 17

ADDED:

aluminum shavings

and its screenings 52.6 - 50 Al

iron scale 100 32.6 71 Fe

TOTAL 403.6 493 (ingot).

For the smelting of 1 tonne of ferrosilicoaluminum from unenriched ash waste from coal combustion at CHPPs, the following charge composition is used:

kg mass. %

Ash waste

after oxidation firing 2020 – 2050 65 – 66

Iron scale 200 – 205 6 – 7

Aluminum shavings and screenings 920 – 930 28 – 29.

Figure 1 attached to the description shows a schematic diagram of the main equipment for metal-thermal smelting - one completed hearth (left) with a fixed array of charge and a system of two hearths (right).

Schematically, figure 1 shows:

1 - horn (wall thickness 20 mm),

2 - an array of charge in a thin-walled steel cylinder,

3 - a layer of loose refractory insulating material,

4 - ignition mixture (in a separate package) with a nichrome spiral,

5 - a basket for transporting an array of charge and extracting smelting products,

6 - loops for transporting the horn,

7 - layer (substrate) of refractory (magnesite) sand,

8 - electrical wires attached to the nichrome spiral in the ignition mixture,

9 - smelting product - slag;

10 - smelting product - ingot,

11 - crust of melted insulating material (refractory sand and slag),

12 - beam crane (lifts the reactor using slings or traverses).

In the proposed method of metal-thermal smelting of iron alloys with vanadium, silicon and aluminum, the preparation of the charge is carried out by standard methods [Gasik M.I., Lyakishev N.P., Emlin B.I. Theory and technology of production of ferroalloys. - M.: Metallurgy, 1988. - 784 S.], including the dosing of charge components (if necessary, pre-drying or calcination) and mixing. As in other methods of metal-thermal smelting “per block”, additional charge components (aluminum waste and lime) are used in crushed form (with a fraction of -5 + 1 mm), while the concentrate (obtained by enrichment of fly ash) is used with particle sizes less than 1 mm .

After mixing the charge components, the mass of the charge is fixed, preventing its spillage - the charge is poured into a thin-walled cylinder mounted on a substrate of loose refractory insulating material in a basket.

Then the mass of the charge, fixed by this cylinder from spilling, is loaded on the specified substrate in this basket into a container for smelting - a hearth.

The fixed array of charge is insulated with a thick massive layer of refractory refractory non-metallic particles. That is, the space inside the hearth is filled with loose refractory insulating material. A basket with an array of charge, fixed by a cylinder, is in a layer of this insulating material.

At the same time, an ignition thermite mixture with saltpeter is previously embedded in the upper or lower layer of the charge, and a nichrome resistance spiral is inserted into the ignition mixture. Electric wires are extended from this spiral outside the hearth for the subsequent initiation of a metallothermic reaction through a fuse.

The initiation of the metallothermic reaction process can be carried out by an electric arc or an electrospark method, using incendiary or thermite mixtures of various compositions.

The filling of the hearth with loose refractory insulating material is performed from an adjacent raised hearth filled with this insulating material, made with the possibility of dropping this insulating material.

The entire surface of the charge mass is isolated, and thus the access of air to the charge is minimized. An insulating layer is created, for example, by backfilling a mixture of silica and refractory sand and crushed stone (magnesite or others) or crushed refractory minerals, crushed refractory production waste (for example, refractory slag, etc.).

The insulating layer is made of refractory particles larger than those used in the implementation of the prototype method, that is, the size of these particles is increased from 0.6-3 mm to 1-10 mm. The elimination of dust-like and fine particles less than 1 mm from the loose refractory insulating material, and the increased gaps between the filled-in particles of the insulating layer due to the reduction in dispersion, ensures the absence of critical pressures of heated expanding gases, which lead to emissions of loose refractory insulating material and molten charge from the hearth. Dangerous effects of increasing gas pressures that worsen the melting process, leading to such emissions, are absent even with an increase in the mass of the melted charge up to 1.8 tons.

The thickness of the insulating layer is chosen based on the size of the charge mass. At the same time, the thicknesses of the insulating layer are formed: under the lower surface of the charge array - 15-20% of the height of this array, on the side surface - 40-48% of the diameter of this array, and the upper layer (above the upper surface) - 72-78% of the height of this array.

These reduced thicknesses, relative to those used in the prototype method, provide an increase in the melting volumes and, accordingly, the masses of the melted charge when using the dimensions and volume of the hearth the same as in the prototype.

A container for smelting - a hearth - is a thick-walled cylindrical glass made of a durable material, such as steel. The cylindrical wall of the hearth (shaft body) is not perforated, without holes. At the same time, the hearth for melting the maximum volume of the charge is increased in diameter up to 180 cm, and in height - up to 260 cm. the mass of this material per 1 kg of charge in the prototype.

This design of the hearth with the above arrangement of the insulating layer is safe, there are no perforations into which the melt can be squeezed out by expanding gases with the formation of accompanying emissions. Gas pressure is minimized by the drainage effect through increased gaps between enlarged particles 1-10 mm in size near the loose lining, gases are removed upwards - through the open upper part of the hearth.

In the metallothermic out-of-furnace method in a closed hearth, it is possible to use a fine concentrate or ash with a fraction of less than 0.5 mm as the main charge component, while costly briquetting, agglomeration or pelletizing of this component is not required, and there is no use of electricity for smelting.

A thin-walled steel cylinder, which fixes the mass of the charge, is removed from the filling with a cable, while the mass of the charge remains completely insulated with loose refractory material with the above-mentioned layer thicknesses.

Next, the reaction process is initiated by applying an electric current with heating the nichrome coil in the fuse, and smelting is carried out in an insulating layer formed according to the above conditions.

The metal-thermal smelting process takes place autonomously without electric heating, due to the use of the heat of exothermic reactions with subsequent crystallization of the resulting alloy in the same insulating layer. If necessary, it is possible to heat the mixture of melted charge components, for example, by electric arc method. If necessary, it is possible to use a smelting scheme with the release (drain) of liquid slag or alloy from the melting space.

Since air access to the molten charge is minimized, melting is essentially closed from the air atmosphere, there are no smoke emissions during smelting, and, accordingly, there are no emissions of dispersed particles, including vanadium oxides (which are toxic).

Under the action of the heat of the metallothermic reaction, the bulk refractory insulating material is sintered into a lining crust up to 8 cm thick on the surface of the melted charge mass.

After the metallothermic process and crystallization, the smelting products are released from the insulating layer, the insulating layer is poured out under the action of its own weight from the hearth using a special device.

Then a basket with smelting products is removed from the forge. The ingot is separated from the slag, the caked crust of the insulating material is separated from the ingot.

The essence of the claimed invention is confirmed by the following and other examples given in table 3.

Example 1. Aluminothermic out-of-furnace melting of an iron alloy with vanadium and silicon was carried out "on the block" in a layer of loose refractory insulating material. A charge mixture consisting of the following components:

charge material obtained by two-stage enrichment of CHPP ash waste - concentrate with a fraction of ≤ 1 mm, composition, wt. %: 7.6 Fe, 33.4 FeO, 34.2 Fe ₂ O ₃ , 7.7 SiO ₂ , 9.5 V ₂ O ₅ , 2.5 MnO, 0.9-2.1 CaO, 0, 5 MgO, 3.4 Al ₂ O ₃ , 0.2 TiO ₂ , 0.1 K ₂ O and Na ₂ O, 0.2 C, 0.2 S, moisture, others - 1.2; shavings of secondary aluminum and silumin, washed from coolant and crushed to a fraction of -5 + 1 mm, ground calcined lime of a fraction of ≤ 5 mm were thoroughly mixed in a mixer. Before mixing, the concentrate and other components of the mixture were dried. The charge mixture was composed of 74 wt. % concentrate (1200 kg), 22 wt.% aluminum chips and screenings (375 kg), 3 wt.% lime (50 kg). From the mixed charge, an array of charge was formed - the mixed charge was poured into a thin-walled steel cylinder installed in a basket on a refractory substrate from a mixture of magnesite and quartz sand, and slightly compacted. The charge array was made with a diameter of 100 cm, a height of 130 cm, the mass of the charge used was 1.63 tons, the volume of the charge array was 1.0 m ³ . Previously, before filling the charge, an ignition mixture consisting of ground potassium nitrate (3 parts by weight) and aluminum powder (1.3 parts by weight) was placed on the substrate, and a nichrome spiral was placed in the ignition mixture.

The basket with the charge in the cylinder was placed in the hearth. Then crushed and screened to a fraction of -10 + 1 slag (aluminothermic smelting) was poured into this hearth from a neighboring raised hearth. The thickness of the resulting insulating layer on the upper surface of the charge mass was 74% of the charge mass, under the lower surface - 20% of the charge mass, on the side cylindrical surface - 47% of the charge mass. A thin-walled steel cylinder, fixing the mass of the charge, was pulled out of the backfill using a cable. The aluminothermic reaction was initiated through a nichrome spiral heated by an electric current with electrical wires pre-attached to it, brought out of the hearth. The smelting process took place without emissions of bulk insulating material, without melt emissions, and without smoke and dust emissions. After the crystallization of the smelting products, the refractory insulating material was poured out of the hearth, the basket with the smelting products was removed from the hearth, the smelting products were removed from the basket. The ingot was separated from the slag, the resulting metal alloy was chemically analyzed, and the metallurgical yield of the alloy was evaluated. It should be noted that the slag phase and the melted layer of the mixture of refractory insulating material easily separated from the ingot. The obtained chemical composition of the ingot is averaged (for three samples), wt. %: 81.2 Fe, 5.4 Si, 7.1 V, 2.3 Mn, 1.2 Al, others - 2.8. The yield was 96%.

Table 3. Characteristics of the work performed according to the method

Examples Fraction,
mm Charge mass dimensions, cm Charge volume, m ³ Charge weight ¹⁾
in one melt
T Thickness of bulk refractory
insulating layer Availability of outliers
smelting products
(with smoke
and dust) diameter height under the bottom surface of the array
charge, in %
from the height of the charge array above the top surface
array
charge, in %
from height
charge array on the side surfaces
array
charge, in %
on the diameter of the charge mass According to the proposed method: 1 -10+1 100 130 1.0 1.63 20 74 47 No 2 -10+1 55 80 0.19 0.3 15 72 40 No 3 -10+1 60 90 0.254 0.4 20 73 44 No 4 -10+1 70 100 0.385 0.6 20 74 45 No 5 -10+1 80 110 0.553 0.86 20 75 46 No 6 -10+1 90 120 0.763 1.21 20 76 42 No 7 ²⁾ -10+1 100 130 1.0 1.8 20 78 48 No 8 ²⁾ -10+1 100 130 1.0 1.8 20 71 39 Eat 9 -10+1 50 65 0.128 0.2 15 71 39 Eat According to the known method: 10 -3+0.6 50 65 0.128 0.2 20 150 100 No eleven -3+0.6 50 65 0.128 0.2 15 78 48 Eat 12 -3+0.6 54 70 0.16 0.25 20 150 100 No 13 -9+0 55 80 0.19 0.3 20 90 70 Eat 14 -11+2 60 90 0.254 0.4 20 120 80 Eat 15 -6+0 65 90 0.30 0.47 20 150 100 Eat

Notes:

1) the charge under the action of its own weight is compacted.

2) The charge in examples 7, 8 is rammed.

3) Smelted from the concentrate obtained from the ash waste of the thermal power plant, iron alloys contain, wt. %: 80-83 Fe, 6-8 V, 4-7 Si, 2-3 Mn, 0.5-1.5 Al, 1.5-3.2 others (including carbon), which corresponds to alloys of the ferrosilicovanadium type for microalloying of steels with vanadium, or steel vanadium semi-product (charge billet), which can be remelted in an induction or electric arc furnace with deoxidation, refining, carburization, modification to obtain tool and wear-resistant vanadium steel.

4) According to these examples, it is possible to smelt aluminum ferrosilicon from unenriched ash waste from thermal power plants subjected to oxidative roasting and containing 45-48% silicon dioxide, 19-21% iron oxides, with the addition of iron scale and excess aluminum reducing agent in the form of screenings and chips.

Examples 2-7, shown in table No. 3, were carried out similarly to example No. 1. Examples No. 8 and 9 are control examples, performed similarly to example No. 1. Examples No. 10-15 are prototype examples.

According to example No. 1 (and other examples of the proposed method given in table 3), when replacing the composition of the charge material with the composition shown in option 2 in table 2, using the composition of the charge in the masses given above for ferrosilicoaluminum. % (in the required proportions) are obtained alloys containing wt. %: 42-46 Fe, 40-45 Si, 10-12 Al, others 2-3. These alloys correspond to FS45A10 grade ferrosilicoaluminum, which is an effective large-tonnage deoxidizer for the steel industry. This alloy is more effective for deoxidation than FS45 ferrosilicon used with secondary aluminum. The total recovery of the FS45A10 alloy during smelting from fly ash by the proposed method is 90-95%, depending on the composition of the main raw material.

Thus, as a result of metal-thermal smelting according to the proposed method, iron alloys with vanadium, silicon and aluminum are obtained.

With an increase in the size of the hearth and the thickness of the layer of loose refractory insulating material, it is possible to increase the mass of the melted charge by more than 1.8 tons.

The proposed method provides an increase in industrial efficiency - the productivity of smokeless metal-thermal smelting of iron vanadium-, silicon- and aluminum-containing alloys from charge material obtained from coal ash from thermal power plants while maintaining environmental cleanliness (no smoke and dust emissions and emissions during smelting).

In doing so, you must specify the following.

If you use loose refractory insulating material with a fraction less than -10 + 1 mm, for example -9 + 0 mm, or more than -10 + 1 mm, for example

-11+2 mm, then with an increase in the mass of the charge over 0.25 tons (volume more than 0.16 m ³ ), emissions of this material and melt from the hearth occur (examples No. 11, No. 13, No. 14 and No. 15).

If an insulating layer less than 72% of the height of the charge mass is used on the upper surface of the charge mass and on the side surfaces less than 40% of the diameter (or width) of the charge mass, then during smelting, emissions of loose refractory insulating material and molten charge occur, accompanied by smoke and dust emissions, (control examples No. 8, No. 9).

If an insulating layer with a thickness of more than 78% of the charge array height is used on the upper surface of the charge massif, more than 20% of the charge massif height is used under the bottom surface, and more than 48% of the charge massif width or diameter is used on the side surfaces of the charge massif, then this will be impractical from the point of view of energy and labor costs for lifting and handling excess volume of refractory insulating material. This also increases the time required to form the insulating layer.

Using the size of the charge array with a diameter of less than 55 cm, a height of less than 80 cm, mass and volume of the charge, respectively, less than 0.3 tons and 0.19 m ³ does not correspond to the necessary increase in industrial efficiency - a sufficient increase in the productivity of the method. Using the dimensions of the charge mass with a diameter of more than 100 cm and a height of more than 130 cm, the mass and volume of the charge, respectively, more than 1.8 tons and 1 m ³ , increases the risks of molten charge and smoke and dust emissions.

Claims (3)

1. The method of metallothermic smelting of iron alloys with vanadium, silicon and aluminum from charge material obtained from fly ash, including preparation of the charge, loading the charge with the ignition mixture into a vessel for smelting with fixing the charge mass from scattering, isolating the entire surface of the fixed charge mass with loose refractory layer, initiation of the reaction process, smelting in this insulating layer, characterized in that the loose refractory insulating material of this layer is used with a fraction of -10 + 1 mm, and on the upper surface of the charge array this layer is formed with a thickness of 72-78% of the height of the charge array, on side surfaces - with a thickness of 40-48% of the width or diameter of the mass of the charge, and the dimensions of the mass of the charge are increased in diameter up to 55-100 cm and in height up to 80-130 cm with a corresponding increase in the volume of the melted mass of the charge to 0.19-1 m ³ and an increase in the mass of the melted charge up to 0.3-1.8 tons. 2. The method according to p. 1, characterized in that as a charge material for smelting, a concentrate obtained from ash waste from the combustion of coal from a thermal power plant is used. 3. The method according to p. 1, characterized in that from unenriched ash waste from a thermal power plant containing 45-48 wt.% silicon dioxide, 19-21 wt.% iron oxides, with the addition of iron scale and excess aluminum reducing agent in the form of screenings and chips smelt ferrosilicoaluminum.

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