RU2455375C1 - Method to produce nickel matte - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: agglomerate oxidised nickel ore and fuel reducing agent are loaded into the furnace. Oxygenated blasting is fed to the combustion zone and recovery-sulfided melting is carried out. Supply of oxygenated blasting is performed through the blast tuyeres placed at least at two levels Through the first level of the tuyeres the main blast is supplied, and through the second level of the tuyeres, located above the first level, additional oxygenated blasting is supplied. The distance between the tuyeres of the first and second levels is 660-1000 mm, while the number of primary blasting is greater than the number of additional blasting.

EFFECT: increased efficiency and sustainability of work of the furnace, as well as the melt-through of nickel alongside with reduction of coke consumption.

5 cl, 1 tbl

Description

The invention relates to metallurgy, and in particular to methods for processing oxidized nickel ore.

A known method of producing nickel matte by means of a furnace unit for pyrometallurgical processing of polymetallic raw materials and a processing method according to the patent of the Russian Federation No. 2191210. According to the said patent, the furnace unit for pyrometallurgical processing of polymetallic raw materials contains at least two closely connected furnaces, one of which is a melting furnace with tuyeres, and the other is a converter with an outlet - a hole and tuyeres, while the two furnaces are interconnected by at least one channel, one end of which is closest to the melting furnace or to the converter, immersed in the melt horizontally, below or above its other end. According to the invention, the melting furnace is made in the form of a low shaft furnace in which tuyeres for continuous purging with oxygen-containing gas are placed at several levels, with the number of levels ranging from 2 to 5 per meter in height of the remelting zone of polymetallic material, the tuyeres of the shaft furnace are located in height of the furnace with offset the axis of the lance holes of each subsequent level relative to the previous one by a distance of 0.35-0.65 from the distance between the axes of the holes of the lances of the previous level, add the converter no mechanical provided with U-shaped flue-tap horizontal architrave, which face through the sealing gasket is connected with the stationary chamber, the diameter of the horizontal converter of 0,32-0,64 of its length and the lance for supplying oxygen-containing gas are arranged along a generatrix of a horizontal converter.

The method of pyrometallurgical processing of polymetallic raw materials according to patent No. 2191210 includes loading an initial charge based on polymetallic raw materials into a smelting furnace, continuous purging with oxygen-containing gas, melting and pouring liquid metal into a converter, sludge settling, removing slag, converting liquid metal in a converter by purging with oxygen-containing gas filing, if necessary, in a liquid metal flux and the release of the finished metal or matte. According to the invention, a low-shaft furnace is used as a melting furnace, continuous supply of oxygen-containing gas blast is carried out at different levels in height of the processed polymetallic material with a number of blast levels from 2 to 5 per meter of column height of the melted polymetallic material, through lances located on the outer shell of the shaft furnace with the offset of the axis of the hole of the lance of each subsequent level, counting from below, by a distance of 0.35-0.65 from the distance between the axes of the holes of the fu m the previous level, with equal or different pressure and flow rate of the oxygen-containing gas at levels blast while blowing oxygen-containing gas is carried out under a pressure of 1 to 10 psig at a flow rate of 5 to 75 m ³ / m ² min, sucks the liquid metal in the internal forge a mine smelting furnace is carried out for 15-120 minutes, sulfide concentrates with particle sizes from 30 to 6000 microns and / or coke with particle sizes from 40 to 5000 microns are additionally introduced into the initial charge based on a polymetallic concentrate and / or secondary raw materials of various kinds in the amount of 5-55 wt.% from the weight of the polymetallic material used in the smelting, while part of the coke in the charge can be replaced by natural gas blasting or steam coal in the amount of 0.18-0.78 of the amount of coke in the charge.

A disadvantage of the known method for producing nickel matte is the unstable operation of a shaft furnace and the resulting increased consumption of coke.

The aforementioned disadvantages are due to the fact that during the smelting of nickel ores, especially easily reducible, uncontrolled formation of ferronickel deposits occurs due to the reduction of iron and nickel from the ores, due to the formation of a reducing medium as a result of the reduction of carbon dioxide to carbon monoxide with heat absorption.

To monitor the condition of the furnaces in order to prevent scaling and erosion of the formed deposits by means of sulfidizers in emergency situations, the load level is often lowered, which reduces the productivity of the melting process (melt) and leads to an increase in fuel consumption (coke). With intensive scaling, the normal melting mode is violated, the coke consumption increases (to compensate for heat losses in reactions with heat absorption). Removing the accretions takes time to remove them. The formation of accretions indicates the formation of zones with increased recoverability, i.e. with a high content of carbon monoxide. During the formation of ferronickel deposits, the normal melting process is hindered, sometimes the channel between the mining furnace and the remote mining is blocked, the normal supply of blast through the tuyeres is disturbed, and the hydraulic regime in the coke bed is often disturbed. All these processes are accompanied by a decrease in melt and an increase in coke consumption.

The technical result achieved by the invention is to increase the productivity of the method, increase the penetration of sintered ore or sinter, reduce the consumption of coke, increase the stability of the furnace.

The technical result is achieved due to the fact that in the method for producing nickel matte, which includes loading agglomerated oxidized nickel-containing ore and reducing fuel into the furnace, supplying the main oxygen-containing blast to the combustion zone, reduction-sulfonating smelting, according to the invention, the supply of oxygen-containing blast is carried out through tuyeres at least at two levels, through the tuyeres of the first level, the main blast is fed, through the tuyeres of the second level located above the tuyeres of the first level, carry out the supply of additional oxygen-containing blast, while the distance between the tuyeres of the first and second levels is 660-1000 mm, and the amount of the main blast is more than the amount of additional blast.

The amount of the main blast can be at least 60% of the total amount of blast.

It is possible to use a blast enriched with oxygen.

It is possible to use heated blast.

The tuyeres of neighboring levels should be placed in a checkerboard pattern with respect to each other.

The melting process in shaft furnaces is carried out thanks to the heat generated during fuel combustion. Gaseous products of combustion, being heated to high temperatures and rising upward towards the lowering charge, give it part of their heat during heat exchange. Thus, the shaft furnace works according to the counterflow principle: the heated gases rise up, and the cold charge and coke fall down. This determines the high utilization of the heat of combustion and the continuity of the whole process. Combustion of fuel in a cupola is not only of purely thermotechnical significance, but it also determines the metallurgical side of melting, i.e. furnace performance, quality of nickel matte, etc.

The main combustible component of any fuel is carbon. Therefore, the process of burning fuel is considered as a process of burning carbon.

Combustion is the chemical reaction of the combination of atmospheric oxygen with a combustible substance - carbon, accompanied by heat.

There are two types of chemical compounds of carbon with oxygen: CO ₂ (carbon dioxide or carbon dioxide) and CO (carbon monoxide).

The combination of carbon with oxygen can occur in two reactions:

C + 1 / 2O ₂ = CO;

C + O ₂ = CO ₂ .

The reaction С + 1 / 2O ₂ = СО is called the incomplete combustion reaction, because its CO product can burn further with the formation of CO ₂ .

The reaction C + O ₂ = CO ₂ is called a complete combustion reaction.

Both reactions are accompanied by heat (exothermic reactions).

26420 kcal / mol (110964 kJ / mol) is released by the reaction C + 1 / 2O ₂ = СО, and 94,060 kcal / mol (395052 kJ / mol) is released by the С + O ₂ = СО ₂ reaction.

In addition to the above reactions, a third reaction is possible - the burning of CO, because carbon monoxide is able to burn by the reaction of CO + 1 / 2O ₂ = CO ₂ . At the same time, heat is also released in the amount of 67640 kcal / mol (284088 kJ / mol).

In industrial furnaces, it is not possible to burn all carbon in CO ₂ . In the exhaust gases must be present CO ₂ and CO. However, by changing the combustion conditions, the ratio of CO ₂ and CO in gases, i.e. change the amount of heat generated.

Air passing through a layer of coke changes its composition, because air oxygen is consumed for fuel combustion. As a result, the amount of free oxygen is gradually reduced. Instead of free oxygen, gaseous combustion products of CO ₂ and CO appear. As the air stream moves through the coke bed, the composition of the resulting gas, i.e. the amount of oxygen, dioxide and carbon monoxide in it changes all the time.

The inventors, given the change in combustion of the composition of the resulting gas, its distribution along the height of the furnace and the processes occurring during the melting of the charge, achieved the claimed technical result.

Upon receipt of the nickel matte according to the known method, the uncontrolled formation of refractory alloys of ferronickel (ferronickel-cobalt) and the formation of deposits from it in the zone of the tuyeres of supply of blast and in the transition channel often occur.

The uncontrolled formation of ferronickel is due to the following.

The main reducing agents in the mine shaft above the tuyeres are, first of all, carbon monoxide CO and hydrogen. Since the concentration of hydrogen in the furnace is low, the main reducing agent is carbon monoxide CO.

In accordance with the principle of A.A.Baikov at temperatures below 570 ° C, reduction reactions occur:

3Fe ₂ O ₃ + СО = 2Fе ₃ O ₄ + СО ₂ (37.137 mJ)

Fe ₃ O ₄ + kCO = 3Fe + (k-4) CO + 4CO ₂ (17.166 mJ)

At temperatures above 570 ° C - reduction reaction:

3Fe ₂ O ₃ + СО = 2Fе ₃ O ₄ + СО ₂ (37.137 mJ)

Fe ₃ O ₄ + mCO = 3FeO + (m-1) CO + CO ₂ (20.892 mJ)

FeO + nCO = Fe + (n-1) CO + CO ₂ (13,607 mJ)

The reduction of iron, nickel and cobalt oxides occurs simultaneously (with the formation of a refractory alloy of ferronickel), and the reduction of cobalt oxides occurs at a faster pace. Perhaps that is why the loss of cobalt Co is greater than the loss of nickel, and the distribution coefficients of cobalt between matte and slag are an order of magnitude lower than for nickel. The state diagrams of binary systems Ni-Fe, Ni-Co, Co-Fe form continuous rows of solid solutions, respectively, and the ternary system Ni-Co-Fe has complete mutual solubility. For all ratios, these three metals form homogeneous alloys with a melting point above 1400 ° C (Hansen M., Anderko X. Structures of double alloys. - M .: Metallurgizdat, 1962, v.1, 607 s, v.2 1488 s; Diagrams states of double metal systems. Handbook in 3 volumes, edited by N.P. Lyakishev, M .: Mechanical Engineering, 1996-2000; Gasik M.I., Lyakishev N.P., Emlin B.I.Theory and technology of production of ferroalloys . - M.: Metallurgy, 1988, 784 p .; State diagrams of metal systems, issue I-XXXIX. - M.: VINITI, 1959-1992).

Cobalt is also included in the resulting refractory alloy, since it is small, the authors call the resulting alloy ferronickel.

The composition of the reduced gases from the tuyere belt to a height of 2100-2400 mm above the tuyere belt has a high content of carbon monoxide, i.e. has a restorative character. Such a medium promotes the reduction of iron and nickel compounds and the appearance of refractory compounds (alloys) and ferronickel deposits that disrupt the normal trouble-free operation of the furnace. This is especially evident when smelting well-reduced ores.

Thus, in order to reduce the reactions occurring with the absorption of heat and the reactions providing the reduction of iron and nickel with the formation of an alloy of ferronickel, it is necessary to reduce the volume of reactions proceeding with the release of CO by its afterburning.

The regulation of these reactions is ensured by the fact that in the inventive method, oxygen-containing blast is supplied at a level higher than the level of the first (main) blast by at least 660-1000 mm. The introduction of a second level of blast, located relative to the first level of blast at a distance of 660-1000 mm, allows you to expand the melting zone and, accordingly, increase the specific melt and the completeness of nickel extraction.

To do this, a second level of tuyeres is introduced into the furnace (for most furnaces, the location of the tuyere of the main blast is at an altitude of about 1400 mm from the bottom of the furnace). On existing stoves, up to 15 tuyeres are located on each side of the kiln. Accordingly, when using swimming trunks in shaft furnaces according to the claimed method, in the first and second row of tuyeres, for example, 15 tuyeres will be located on each side of the furnace.

The supply of blast through the second level of the tuyeres ensures the implementation of the reaction CO + 1 / 2O ₂ = CO ₂ . This ensures a decrease in the CO content in the furnace, suppresses the reducing atmosphere that promotes the formation of ferronickel, and reduces the volume of reactions that occur with heat absorption.

The formation of deposits is also due to the fact that during the smelting of nickel-containing ore, oxygen-containing blast supplied to the oxygen zone passes through the coke, while the oxygen of the blast interacts with coke carbon by the above reactions.

In this case, as already noted, during the incomplete combustion reaction, an amount of heat is released, significantly less than during the complete combustion reaction. Therefore, the incomplete combustion reaction is accompanied by less heat in relation to the combustion reaction, which is accompanied by cooling of the furnace.

During combustion during the passage of CO ₂ emitted during combustion, it interacts, in turn, with coke carbon by the reaction: C + CO ₂ = 2CO. This reaction is accompanied by the absorption of heat (-41220) kcal / mol (173124 kJ / mol), which leads to a decrease in temperature in the reaction zone and an increase in the reduction ability of gases due to the formation of carbon monoxide CO.

Molecule ₂ is a linear CO: O-CO. Both bonds of oxygen with carbon are equivalent, therefore, the energy 41220 kcal / mol is the energy spent on detaching carbon atoms from the body (pieces) of coke.

When melting oxidized nickel ores, there is no need to maintain an increased reducing atmosphere. The fuller the fuel is burned to CO ₂ , the better the smelting performance.

In order to reduce the likelihood of formation of ferronickel layers in the furnace, it is necessary to reduce the concentration of reducing gases (CO) by burning CO + 1 / 2O ₂ = CO ₂ , at the same time, more complete combustion of the fuel will occur, and the zone of elevated temperatures favorable for the melting process will expand , and increase the penetration of ore raw materials (increased productivity).

To this end, the authors proposed to introduce a second level of oxygen-containing blast located higher than the first main level of blast by 660-1000 mm, which follows from figure 1.

The distance between both levels of the blast (between the tuyeres of the first level and the second level) is selected based on the fact that intense CO release occurs in this gap.

By supplying an oxygen-containing blast at a level higher than the level of the first blast, we will ensure that the reaction CO + 1 / 2O ₂ = CO _{2 is} carried out in the furnace above the level that produces heat in an amount significantly greater than during the incomplete combustion reaction. Thus, it becomes possible to compensate for the heat loss in the furnace from the carbon dioxide CO ₂ reduction reaction.

Thus, the regulation of the reducing environment and the expansion of the zone of the furnace with high temperature can significantly reduce the likelihood of formation of ferronickel deposits, increase the stability and productivity of shaft furnaces while reducing coke consumption.

Providing high temperature in the furnace can significantly reduce the likelihood of formation of accretions.

Figure 1 shows the change in the composition of the gaseous medium along the height of the shaft furnace during cold air blasting when the blast is fed through the first (main) tuyere level (CO graph, shown by a solid line).

When blowing air through the second tuyere level, the graph of the CO content (the dependence of the CO content along the furnace height on the level of the main tuyere) has the character shown by a dashed line. Those. CO content is reduced.

Previously, oxygen enriched blast was used to ensure complete combustion of fuel to CO ₂ . In this case, the combustion conditions shift towards more complete combustion and fuel economy. But even in these conditions, especially when melting easily reducible ores, the formation of ferronickel deposits is observed and the disturbances in the operation (progress) of the furnaces, i.e. there is an increased reducibility of the gaseous medium and an increased content of CO.

The appropriateness of staggering the tuyeres of the second level in relation to the tuyeres of the first level is explained by the following.

In the areas between the tuyeres, the greatest oxygen deficiency is observed and the highest concentration of carbon monoxide is created, i.e. reducing medium, accompanied by heat absorption (cooling of the furnace) and at the same time the formation of deposits of refractory ferronickel compounds. Therefore, the supply of blast to this zone and the suppression of the reducing atmosphere lead to the heating of the furnace in this zone, the expansion of the melting zone, and the reduction of the formation of ferronickel deposits.

All this favorably affects the stability of the furnaces, as emergency stops are sharply reduced, there is no need for frequent inspection of the condition of furnaces by lowering the load level. As a result, the productivity of the furnaces increases, and the coke consumption decreases. The expected decrease in coke consumption and an increase in productivity of more than 15%. Reduced repair costs.

The melting process of oxidized nickel ores is carried out by layer-by-layer burning of coke. Moreover, it is known from practice that with coke pieces larger than 40 mm, coke layers are optimal (with an average coke pieces diameter of 55-65 mm) 180-200 mm. For smaller coke, finer layers are required. The uniform distribution of the latter is more difficult. Based on this condition, taking into account the specific consumption of coke, material is supplied to the shaft furnace (coke, fluxes, agglomerates, briquettes, sulfidizers, etc.).

Currently, there are several technology options associated with the preparation of ore and the supply of blast in shaft furnaces: air blasting, oxygen-rich blasting, heated blasting. It should be noted that the improvement of the intensification of the nickel ore smelting process was associated with the intensification of fuel combustion, i.e. with intensification of the supply of blast. However, simultaneously with the intensification of the fuel combustion process, the distribution coefficient of nickel between matte and slag decreased, i.e. losses of nickel with slag increased. In addition, at present, when melting oxidized nickel ores in shaft furnaces during layer-by-layer burning of fuel, high demands are made on the quality of the fuel (coke), namely, the use of large pieces of coke larger than 40 mm is optimal, because when using smaller coke, its consumption increases. Also, the use of smaller classes of fuel leads to the formation of increased amounts of CO, i.e. contributes to the creation of a reducing atmosphere for iron and nickel and, consequently, to the formation of nastronie from ferronickel.

The authors' experience shows that when layer-by-layer burning of fuel (coke) with the introduction of the second level of blast located at a distance of 660-1000 mm relative to the first level of tuyeres, the requirements for the quality of coke, including the size of pieces of coke, are reduced. The completeness of the use of its chemical potential increases. For example, when replacing coke larger than 40 mm with coke larger than 25 mm, coke consumption will change less than with single-row blasting.

It is advisable to ensure the distribution of the total amount of blast into two tuyere levels in the following amounts:

- the volume (quantity) of blast in the first main (lower) level of the tuyeres should be more than the volume of blast in the second level (upper level) in order to exclude the occurrence of the second focus of fuel combustion;

- optimally the blast in the first main (lower) tuyere level should be at least 60% of the total blast quantity.

Figure 2 shows a cross section of a shaft furnace, on which the combustion zone and the temperature distribution in the cross section of the furnace at the same blast level (main) are shown on the left; on the right shows the combustion zone and temperature distribution in the cross section of the furnace at two levels of blast (according to the claimed method).

The results of the melting of Nickel-containing ores according to the claimed method are illustrated in the Table.

Where in column 1 are the item numbers relating to different types of fuel and blast conditions. The interpretation of column 1 is given after the Table.

No. p / p Coke consumption,% Matte content,% The content in the slag,% Specific melt, t / m ² * day The increase in penetration,% Nsht / Nishl. Coke consumption reduction,% Ni Co S Ni S one thirty 12.0 0.24 19.65 0.12 0.37 28.0 0 one hundred 0 2 20,44 10.1 0.72 22.1 0.16 0.38 43.36 0 63.1 0 3 28 12.0 0.24 19.7 0.115 0.35 28.9 3.0 104.4 6.7 four thirty 10.72 0.21 19.65 0,085 0.33 31.8 3.8 127 0 5 thirty 10.84 0.23 19.56 0.06 0.36 28.0 0 180 0 6 28 12.05 0.23 20.1 0.115 0.35 30,0 7.0 105 6.7 7 26 12.05 0.22 19.8 0,110 0.36 32,0 14.3 110 13.3 8 25.5 12.1 0.25 20.5 0.105 0.35 32.3 15.4 115 15.0 9 25.5 12.1 0.25 20.5 0,078 0.36 32.1 14.6 150 15.0 10 18.5 10,4 0.78 22.3 0.102 0.38 47.78 10,2 102.0 11.6 eleven 18.0 10.5 0.76 22.4 0.102 0.3 48.50 11.8 102.0 11,4

Decoding column 1 Tables:

1. Metallurgical coke is larger than 40 mm, the average size is 60 mm. Air blast without heating, tuyere level - one (main), smelting of ore briquettes.

2. Metallurgical coke larger than 40 mm, average size 60 mm. Oxygen enriched blast, tuyere level - one (main), sinter melting.

3. Coke from a coal charge with the addition of caking with the release of volatile substances 17.8% in an amount of 40%; the coke ash content is 8%, the volatiles yield of coke is 0.7%, the average size of coke pieces is 68 mm. Air blast without heating, tuyere level - one (main), smelting of ore briquettes.

4. Metallurgical coke larger than 40 mm in an amount of 50% of the total amount of fuel; lump petroleum coke with a size of (40-100) mm in an amount of 50% of the total amount of fuel. Air blast without heating, tuyere level - one (main), smelting of ore briquettes.

5. Metallurgical coke is larger than 40 mm 50% and anthracite classes (40-100) mm 50%. Air blast without heating, tuyere level - one (main), smelting of ore briquettes.

6. Metallurgical coke larger than 40 mm, smelting briquettes. Airless blast without heating (cold blasting) with the distribution of blasting levels:

- the main (lower) level of 90% of the total amount of blast;

- an additional (upper) level of 10% of the total blast quantity.

An additional level is located above the main 800 mm.

7. Metallurgical coke larger than 40 mm, briquetting. Airless blast without heating (cold blasting) with the distribution of blasting levels:

- the main (lower) level of 70% of the total amount of blast;

- an additional (upper) level of 30% of the total blast quantity.

An additional level is located above the main 800 mm.

8. Metallurgical coke larger than 40 mm, briquetting. Airless blast without heating (cold blasting) with the distribution of blasting levels:

- the main (lower) level of 60% of the total amount of blast;

- an additional (upper) level of 40% of the total blast quantity.

An additional level is located above the main 800 mm.

9. Metallurgical coke larger than 40 mm in the amount of 70% and anthracite grades (40-100) mm in the amount of 30%, smelting of ore briquettes. Airless blast without heating (cold blasting) with the distribution of blasting levels:

- the main (lower) level of 70% of the total amount of blast;

- an additional (upper) level of 30% of the total blast quantity.

An additional level is located above the main 800 mm.

10. Metallurgical coke larger than 40 mm, sinter smelting. Air blast enriched with oxygen with the distribution of blast by levels:

- the main (lower) level of 70% of the total amount of blast;

- an additional (upper) level of 30% of the total blast quantity.

An additional level is located above the main 800 mm.

11. Metallurgical coke larger than 40 mm, sinter smelting. Oxygen enriched air blast with level distribution:

- the main (lower) level of 65% of the total amount of blast;

- additional (second level) 800 mm above the main one - 25% of the total blast quantity;

- the third level - 1000 mm higher than the second - 10% of the total blast consumption.

The introduction of the third level makes it possible to reduce heat losses from chemical underburning of fuel and at the same time improve the service conditions of furnaces (make them more comfortable), because CO will be burned in the charge layer and give heat to the charge, and not burn out on the top, do not worsen the conditions of the flues, dust collecting devices and smoke exhausters. Those. operating conditions of gas ducts, dust collecting equipment and smoke exhausters are improved.

The total loading height is 5.0-5.5 m from the tuyere level.

Using the proposed method provides:

1. Normalization of the operation of shaft furnaces, facilitating the work of maintenance personnel.

2. Reducing coke consumption and increasing the stability of shaft furnaces by reducing emergency stops (by reducing heat loss in the furnace, reducing the reducing atmosphere), which allows to increase the productivity of furnaces by 5-15%.

3. Reducing the current (relative) consumption of coke in the working spike by 5-10%.

4. Reducing the influence of coke quality, including by size, on the technological indicators of mine smelting.

5. Improving the efficiency of use of coke and due to improved environmental conditions by reducing emissions of CO, CO ₂ and SO ₂ .

6. The increase in penetration due to the expansion of the melting zone and increase the duration of the furnaces; reduction of nickel losses with slags.

The expected overall reduction in coke consumption is at least 15%.

The expected increase in furnace productivity is at least 15%.

Claims (5)

1. The method of producing nickel matte, including loading into the furnace a bit of oxidized nickel-containing ore and reducing fuel, supplying the main oxygen-containing blast to the combustion zone, sulphiding reduction smelting, characterized in that the supply of oxygen-containing blasting is carried out through lances located at least at two levels moreover, through the tuyeres of the first lower level, the main blast is fed, through the tuyeres of the second level located above the tuyeres of the first level, the filler is supplied oxygen-containing blast, the distance between the tuyeres of the first and second levels is 660-1000 mm, and the amount of the main blast is greater than the amount of additional blast. 2. The method according to claim 1, characterized in that the amount of the main blast is at least 60% of the total amount of blast. 3. The method according to claim 1, characterized in that they use blast enriched with oxygen. 4. The method according to claim 1, characterized in that use heated blast. 5. The method according to claim 1, characterized in that the tuyeres of the first and second levels are arranged in a checkerboard pattern with respect to each other.

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