CN114107588B - Preparation method of high-purity molten iron - Google Patents
Preparation method of high-purity molten iron Download PDFInfo
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- CN114107588B CN114107588B CN202111296390.8A CN202111296390A CN114107588B CN 114107588 B CN114107588 B CN 114107588B CN 202111296390 A CN202111296390 A CN 202111296390A CN 114107588 B CN114107588 B CN 114107588B
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Abstract
The invention discloses a preparation method of high-purity molten iron, belongs to the technical field of smelting of iron concentrate powder, and solves the technical problems of long smelting process and high energy consumption in the conventional preparation of high-purity molten iron. The preparation method of the high-purity molten iron comprises the following steps: step 1, adding industrial pure iron into a vacuum induction furnace to be used as an induction heating medium to form a molten iron bath; step 2, mixing iron concentrate powder and lime flux and spraying into a molten iron molten pool; then hydrogen is sprayed into a molten iron bath, the hydrogen and the melt undergo reduction reaction, the slag generated by reduction floats upwards and enters a slag layer, and the molten iron generated by reduction enters a molten iron layer; and 4, stopping blowing the hydrogen when the molten iron meets the tapping requirement, blowing the argon into the molten iron layer through an argon blowing unit, performing vacuum stirring and degassing by using the argon, and tapping after degassing to obtain the high-purity molten iron. The invention realizes the preparation of high-purity molten iron by a short process and reduces the smelting cost.
Description
Technical Field
The invention relates to the technical field of reduction and smelting of iron concentrate powder, in particular to a preparation method of high-purity molten iron.
Background
The iron and steel industry is used as the basic industry of national economy and bears the burden of national basic material production. 90 percent of crude steel in China is produced through a long flow of iron ore-sintering (or pellet) -blast furnace iron-making-steel-making, the energy consumption is high, the pollution is serious, and China CO is produced in 2020 2 The discharge amount exceeds 120 hundred million tons, and CO is generated in the steel industry 2 The emission amount accounts for 15 percent of the whole country and reaches 18 hundred million tons, and CO is generated in the iron-making process 2 The discharge accounts for 73.1 percent of the whole steel production flow and exceeds 13 hundred million tons. Therefore, the temperature of the molten metal is controlled,the steel industry, in particular to the iron-making field, is imperative to green transformation.
The non-blast furnace iron making can avoid the use of coke, save the coking link, especially reduce the discharge amount of harmful gas by a wide margin with the hydrogen metallurgy based on the direct reduction of the gas-based shaft furnace, and is developed rapidly at present. However, the gas-based shaft furnace reduction must use high-quality oxidized pellets or lump ore as raw materials, and under the conditions of shortage of high-quality lump ore and overhigh price of imported lump ore in China, the oxidized pellets can be prepared only through a series of procedures such as ore dressing, pellet making, oxidizing roasting and the like, so that the process flow is long and the energy consumption is high. In addition, the reducing gas must be heated to a higher temperature to provide the heat required by the shaft furnace reduction, the safety problem of the heating process of the reducing gas, such as the carbon precipitation problem of the hydrogen-rich gas heating process, and the hydrogen corrosion problem of the pure hydrogen heating process, cannot be solved. Therefore, although the gas-based shaft furnace direct reduction process has certain advantages compared with the traditional iron making-steel making process, the optimization is not achieved far away.
The iron ore concentrate powder can be directly utilized by one-step melting reduction, and the reduction and smelting are synchronously completed, so that the process flow is greatly shortened, and the method is theoretically more superior to gas-based direct reduction, but the problems of the melting reduction, including serious scouring of refractory materials at the furnace top due to high gas-phase space temperature, low heat transfer efficiency of the gas-phase space to a molten pool and the like, are difficult to overcome, and certain influence is brought to stable production.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a method for preparing high purity molten iron, which is used to solve the technical problems of long smelting process and high energy consumption in the conventional high purity molten iron smelting process.
The invention is mainly realized by the following technical scheme:
the invention provides a preparation method of high-purity molten iron, which comprises the following steps:
step 1, adding industrial pure iron serving as an induction heating medium into a vacuum induction furnace at the beginning, heating and melting under the conditions of 50-100 Pa and 1550-1700 ℃ in a vacuum state, and forming a molten iron pool after complete melting;
step 2, continuously spraying iron concentrate powder and lime flux into the molten iron melting pool in the step 1 for melting pre-reduction, and forming a melt after melting pre-reduction; after iron ore concentrate powder and a lime solvent are sprayed, hydrogen is sprayed into a molten iron bath through a hydrogen spraying unit arranged at the bottom of a vacuum reaction furnace, the hydrogen and a melt in the molten iron bath carry out a smelting reduction reaction, slag generated by smelting pre-reduction and slag generated by the smelting reduction reaction both float upwards and enter a first containing layer to form a slag layer, and molten iron generated by the smelting reduction reaction sinks into a third containing layer to form a molten iron layer; forming a slag-iron mixed layer between the slag layer and the molten iron layer; the slag-iron mixed layer is positioned in the second accommodating layer;
continuously spraying iron concentrate powder and a lime solvent into the formed slag-iron mixed layer, then spraying hydrogen into a molten iron layer through a hydrogen gas spraying nozzle, heating the hydrogen gas by molten iron in the floating process, heating the hydrogen gas, then enabling the heated hydrogen gas to enter the slag-iron mixed layer, carrying out a melting reduction reaction with a melt in the slag-iron mixed layer, continuously floating the slag generated by reduction to a molten slag layer, and continuously sinking the molten iron generated by the reaction to the molten iron layer;
and 3, when the molten iron in the molten iron layer is accumulated to a certain height and meets the tapping requirement, stopping blowing the hydrogen, the iron concentrate powder and the lime solvent, blowing argon into the molten iron layer through an argon blowing unit, performing vacuum stirring by using the argon to promote molten iron degassing, and tapping after the molten iron degassing to obtain high-purity molten iron.
Further, in the step 2, the iron ore concentrate powder and the lime flux are mixed by the mixing unit and then sprayed into the molten iron bath by the mixing and water spraying unit.
Further, in the step 2, when the iron ore concentrate powder and the lime solvent are proportioned by the batching unit, the binary alkalinity of the mixture of the iron ore concentrate powder and the lime solvent is controlled within the range of 2.5-3.0.
Further, in the step 1, the reduction temperature of the vacuum induction furnace is 1600 to 1650 ℃.
Further, in step 2, the sulfur content of the melt produced by melting the pre-reduction is reduced to below 25 ppm;
further, in the step 2, the pre-reduction rate is 97.2% -98.8%.
Further, in the step 2, the hydrogen injection time is 25-30 min, and the injection amount of the hydrogen is determined according to H 2 The mol ratio of/FeO is controlled.
Further, in the above step 2, H 2 The mol ratio of the/FeO is 1.5-2.
Further, in the step 3, the vacuum stirring time is 10 to 15min, and the N and H in the degassed molten iron are removed to be less than 3 ppm.
Further, in the step 3, the blowing flow rate of argon gas is 0.4 to 0.6L/(min. Kg molten iron).
Further, in the step 3, a part of molten iron is always reserved as a medium for vacuum induction heating after tapping.
Compared with the prior art, the invention can realize at least one of the following beneficial effects:
(1) The iron-making method provided by the invention avoids the use of coke, thereby saving the coking link; the preparation method provided by the invention uses pure hydrogen as a reducing agent and electricity as a heat source, realizes carbon-free emission in the preparation process, adopts a heating mode in the induction furnace to provide heat, has high energy utilization rate, and avoids the problems of furnace top scouring of the vacuum induction furnace and low heat transfer efficiency of the gas phase space caused by overhigh temperature of combustion flue gas in the gas phase space.
(2) When the existing gas-based reduction furnace is used for iron making, high-quality oxidized pellets or lump ores need to be prepared firstly, and when raw materials of iron concentrate powder are faced, the oxidized pellets need to be prepared through ore dressing, pelletizing and oxidizing roasting, so that the process flow is long and the energy consumption is high. The preparation method adopts the iron concentrate powder to directly blow into the furnace, avoids the working procedures of sintering or pelletizing, oxidizing and roasting, and completes the processes of dephosphorization, desulfurization, reduction, slag-iron separation and refining of the iron concentrate powder in the vacuum induction furnace, thereby realizing the great simplification of the process and the equipment, greatly shortening the process flow, improving the smelting efficiency and reducing the requirement on the impurity content of the iron concentrate.
(3) The invention fully utilizes the high oxidizability of a molten pool in the pre-reduction stage of the molten iron to carry out oxidative desulfurization and dephosphorization, and adopts carbon-free smelting to avoid the reduction of phosphorus, thereby eliminating the limitation on the contents of sulfur and phosphorus in iron concentrate powder and producing high-purity molten iron in an extremely short flow.
(4) The iron ore concentrate powder is subjected to pure hydrogen reduction in a vacuum melting state, so that the reduction rate is accelerated, the oxygen content in the molten iron is reduced to an extremely low content (the oxygen content is less than 10 ppm), and a deoxidation process and the use of a deoxidizer are omitted.
(5) The method adopts molten iron to carry out melting pre-reduction on the iron ore concentrate powder, converts the conventional gas-solid two-phase reaction into a homogeneous melting reaction, and improves the reduction rate; the molten iron layer is used as an induction medium to provide heat for the molten pool, and the defect of low heat transfer efficiency of the traditional melting reduction gas phase space is overcome.
In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings, in which like reference numerals refer to like parts throughout, are for the purpose of illustrating particular embodiments only and are not to be considered limiting of the invention.
FIG. 1 is a schematic view of a manufacturing process of high purity molten iron.
Detailed Description
The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and which together with the embodiments of the invention serve to explain the principles of the invention and not to limit its scope.
The invention also provides a preparation method of the high-purity molten iron, which comprises the following steps:
step 1, adding industrial pure iron into a vacuum induction furnace and taking the industrial pure iron as an induction heating medium, heating and melting the industrial pure iron under the vacuum state at 50-100 Pa, and setting the melting temperature to 1550-1700 ℃; adding iron ore concentrate powder and lime flux;
step 1, adding industrial pure iron serving as an induction heating medium into a vacuum induction furnace, heating and melting at the temperature of 50-100 Pa and 1550-1700 ℃ in a vacuum state, and forming a molten iron bath after complete melting;
step 2, continuously spraying iron concentrate powder and lime flux into the molten iron melting pool in the step 1 for melting pre-reduction, and forming a melt after melting pre-reduction; after iron ore concentrate powder and a lime solvent are sprayed, hydrogen is sprayed into a molten iron bath through a hydrogen spraying unit arranged at the bottom of a vacuum reaction furnace, the hydrogen and a melt in the molten iron bath carry out a smelting reduction reaction, slag generated by smelting pre-reduction and slag generated by the smelting reduction reaction both float upwards and enter a first containing layer to form a slag layer, and molten iron generated by the smelting reduction reaction sinks into a third containing layer to form a molten iron layer; forming a slag-iron mixed layer between the slag layer and the molten iron layer; a slag-iron mixed layer is located in the second containment layer. And continuously spraying iron concentrate powder and a lime solvent into the formed slag-iron mixed layer, then spraying hydrogen into the molten iron layer through a hydrogen gas spraying nozzle, heating the molten iron in the hydrogen floating process, heating the molten iron, then allowing the molten iron to enter the slag-iron mixed layer, carrying out a melting reduction reaction with a melt in the slag-iron mixed layer, continuously floating the slag generated by reduction to a molten slag layer, and continuously sinking the molten iron generated by the reaction to the molten iron layer.
Specifically, iron ore concentrate powder and quicklime powder (lime flux) are directly blown into a molten iron molten pool, the temperature of the iron ore concentrate powder in the molten iron molten pool is rapidly raised, and in the rapid temperature raising process, desulfurization is carried out through autoxidation, and the iron ore concentrate powder and molten iron in the molten iron molten pool are subjected to pre-reduction reaction to rapidly form an FeO melt; in the pre-reduction reaction process, phosphorus in the iron ore concentrate powder is combined with the lime flux to form stable calcium phosphate, the calcium phosphate floats upwards to enter the first accommodating layer, and forms a slag layer together with slag generated by the subsequent melting reduction reaction by utilizing hydrogen.
The iron ore concentrate powder and the lime flux are proportioned by the proportioning unit and then are sprayed into a molten iron melting pool of the vacuum induction furnace by the proportioning and blowing unit to be melted and pre-reduced; in the process of melting materials, deeply removing sulfur and iron oxide in iron ore concentrate powder through vacuum autoxidation, forming a melt after the iron ore concentrate powder is melted, and reducing the sulfur content of the melt to below 25 ppm; phosphorus in the iron concentrate powder is autoxidized by the iron concentrate powder in the slag-iron mixed layer during the melting pre-reduction process.
3Fe 2 O 3 +FeS＝7FeO+SO 2 (1)
3Fe 3 O 4 +FeS＝10FeO+SO 2 (2)
Fe in iron ore concentrate powder during melting 2 O 3 Or Fe 3 O 4 The iron ore concentrate powder and molten iron react violently to realize melting pre-reduction of materials, and high-valence iron oxide in the iron ore concentrate powder is converted into FeO melt.
Fe 2 O 3 +Fe＝3FeO (3)
Fe 3 O 4 +Fe＝4FeO (4)
In addition, hydrogen sprayed from the bottom of the molten iron pool firstly passes through a molten iron layer and is fully heated by the molten iron layer in the upward floating process, feO is reduced after heating, the oxygen potential of the slag-iron mixed layer (the oxygen potential refers to the relative chemical potential of oxygen in a balance system) is gradually reduced from top to bottom, an oxygen-free slag molten iron layer is formed at the lower part of the slag-iron mixed layer, sulfur in the molten iron is fully removed, and the reduced molten iron after oxygen and sulfur removal is settled and enters the molten iron layer; before tapping, argon is used for replacing hydrogen to be sprayed into a molten iron layer, and the molten iron is subjected to vacuum stirring and degassing, so that high-purity molten iron is obtained.
It should be noted that, in the step 2, the hydrogen injection time is 25-30 min, and the injection amount of the hydrogen is H 2 The mol ratio of FeO/FeO is controlled to be 1.5-2, the melt in the molten iron bath is directly reduced by hydrogen, the reduced molten iron is gradually deposited into a molten iron layer, the slag generated by the reaction floats upwards to enter a slag layer due to lighter density, and the oxygen content of the molten iron is reduced to the extent that the oxygen content of the molten iron is reduced<10ppm; and the sulfur in the molten iron is further removed in the reduction process, and the sulfur content of the molten iron is reduced to<5ppm。
FeO+H 2 ＝Fe+H 2 O (5)
CaO+FeS+H 2 ＝CaS+Fe+H 2 O (6)
And 3, when the molten iron in the molten iron layer is accumulated to a certain height and meets the tapping requirement, stopping blowing the hydrogen, the iron concentrate powder and the lime solvent, blowing argon into the molten iron layer through an argon blowing unit, performing vacuum stirring by using the argon to promote molten iron degassing, and tapping after the molten iron degassing to obtain high-purity molten iron.
In the step 2, the binary alkalinity of the mixture of the iron ore concentrate powder and the lime flux is 2.5-3.0, so as to ensure a better desulfurization effect; the temperature of the vacuum induction furnace is 1600-1650 ℃ for ensuring better reduction effect.
In the step 3, a part of molten iron is always reserved as a medium for vacuum induction heating after tapping.
In the step 3, the time for vacuum stirring and degassing is 10 to 15min, and the blowing flow rate of argon is 0.4 to 0.6L/(min. Kg molten iron) so as to remove N and H in the molten iron to be less than 3 ppm.
The invention also provides a preparation system of high-purity molten iron, which is used for realizing the preparation method of the high-purity molten iron, and as shown in figure 1, the preparation system comprises a vacuum induction unit, an argon injection unit, a hydrogen injection unit, a batching unit and a batching injection unit; a first accommodating layer, a second accommodating layer and a third accommodating layer which are communicated with each other are sequentially arranged in the vacuum induction unit from top to bottom; the first accommodating layer is internally provided with a slag layer; a slag-iron mixed layer is arranged in the second accommodating layer, and a molten iron layer is arranged in the third accommodating layer; the argon blowing unit and the hydrogen blowing unit are communicated with the molten iron layer; the batching unit is communicated with the slag-iron mixed layer through the batching blowing unit; the iron ore concentrate powder and the lime flux enter the slag-iron mixed layer of the vacuum induction unit through the batching unit and the batching blowing unit.
Specifically, as shown in fig. 1, the system for high purity molten iron comprises a vacuum induction unit, an argon blowing unit, a hydrogen blowing unit, a batching unit and a batching blowing unit; wherein, a first containing layer, a second containing layer and a second containing layer are sequentially arranged in the vacuum induction unit from top to bottom; a slag layer is arranged in the first accommodating layer, a slag-iron mixed layer is arranged in the second accommodating layer, and a molten iron layer is arranged in the third accommodating layer; outlets of the argon gas injection unit and the hydrogen gas injection unit are communicated with the third containing layer, and the iron concentrate powder and the quicklime powder are mixed by the mixing unit and then injected by the injection unit to form a slag-iron mixed layer; and a slag outlet is formed in the third accommodating layer and used for discharging slag in the vacuum induction unit.
Compared with the prior art, the method has the advantages that the raw material iron concentrate powder is directly injected into the furnace, the sintering or pelletizing oxidizing roasting process is avoided, the processes of dephosphorization, desulfurization, reduction, slag-iron separation and refining of the iron concentrate powder are all completed in the vacuum induction unit, the process and the equipment are greatly simplified, the process flow is greatly shortened, the preparation efficiency is improved, and the requirement on the impurity content of the iron concentrate is reduced. And secondly, pure hydrogen reduction is carried out on the iron concentrate powder in a vacuum melting state, so that the reduction rate is accelerated, the oxygen content in the molten iron is reduced to an extremely low content (< 10 ppm), and a deoxidation process and the use of a deoxidizer can be omitted. Thirdly, the iron ore concentrate powder is subjected to melting pre-reduction by adopting molten iron, the conventional gas-solid two-phase reaction is converted into a homogeneous melting reaction, and the reduction rate is improved; the molten iron layer is used as an induction medium to provide heat for the molten pool, and the defect of low heat transfer efficiency of the traditional melting reduction gas phase space is overcome.
It should be noted that the second accommodating layer (slag-iron mixed layer) in the present invention includes a metallic iron pre-reduction region and a hydrogen reduction region; the metallic iron pre-reduction area is arranged above the hydrogen reduction area; the oxygen potential of the slag-iron mixed layer is gradually reduced from top to bottom.
Specifically, the slag-iron mixed layer of the vacuum induction unit comprises a metallic iron pre-reduction area and a hydrogen reduction area, wherein the hydrogen reduction area is a final reduction area and is positioned below the metallic iron pre-reduction area; in the metallic iron pre-reduction area, the iron ore concentrate powder is subjected to vacuum melting auto-oxidation desulfurization, while in the hydrogen reduction area, reduction deep desulfurization is performed, and the desulfurization efficiency and the desulfurization limit of the iron ore concentrate powder are greatly improved through the vacuum melting auto-oxidation desulfurization and the reduction deep desulfurization. In addition, phosphorus in the iron ore concentrate powder is oxidized in the metallic iron pre-reduction area to form stable calcium phosphate, and the calcium phosphate cannot be reduced by hydrogen, so that the phosphorus can be prevented from being dissolved in the molten iron.
In order to better prepare high-purity molten iron, the vacuum induction unit in the invention is a vacuum induction furnace, the vacuum induction furnace takes electricity as a heat source and provides heat for materials in the furnace in an internal heating mode; the bottom of the molten iron layer is provided with a tap hole which is used for discharging high-purity molten iron.
Specifically, the vacuum induction furnace of the invention uses a potential heat source, completely avoids the utilization of carbonaceous energy, and realizes no carbon emission in the whole process. The vacuum induction furnace heats molten iron in an internal heating mode, the molten iron is utilized to carry out melting pre-reduction on iron ore concentrate powder, and the conventional gas-solid two-phase reaction is converted into a homogeneous melting reaction so as to improve the reduction rate; in addition, the molten iron layer is used as an induction medium to provide heat for the molten pool, and the defect of low heat efficiency of traditional smelting reduction gas phase space transfer is overcome.
It should be noted that a tap hole is formed in the bottom of the molten pool, and the high-purity molten iron obtained by smelting is discharged out of the vacuum induction unit through the tap hole.
In order to realize the recycling of the hydrogen reducing gas, the system also comprises a reducing flue gas treatment unit; the reduction flue gas treatment unit is connected with the top of the vacuum induction unit, the reduction flue gas treatment unit comprises waste heat recovery equipment, desulfurization equipment and spray dehydration and drying equipment which are sequentially connected, and the reduction flue gas enters the hydrogen injection unit together with supplemented hydrogen after waste heat utilization, desulfurization, spray dehydration and drying.
Specifically, still be equipped with the fourth in the vacuum induction furnace and hold the layer, the fourth holds the layer and locates the top that the first layer was held, the fourth holds the layer and is used for holding the reduction flue gas that produces, in addition, be equipped with reduction exhanst gas outlet on the top surface of vacuum induction furnace, reduction flue gas processing unit one end is connected with this reduction exhanst gas outlet, the other end is connected with hydrogen jetting unit, the reduction flue gas is drawn forth through reduction exhanst gas outlet, in proper order through waste heat recovery equipment, sweetener, spray dehydration and drying equipment and handle, obtain surplus hydrogen after waste heat recovery, the desulfurization, spray dehydration and drying, introduce this part of surplus hydrogen and the hydrogen of newly supplementing into the vacuum induction furnace together, the cyclic utilization of surplus hydrogen has been realized.
It should be noted that the dosing unit of the present invention comprises a feed delivery pipe and a buffer chamber; iron ore concentrate powder and lime flux enter a buffer chamber through a feed delivery pipe; the blowing unit comprises a spray gun, the buffer chamber is communicated with the spray gun, and the iron concentrate powder and the lime solvent are sprayed into the slag-iron mixed layer by the spray gun after being mixed by the buffer chamber.
The argon blowing unit comprises an argon source, the argon source is connected with the vacuum induction furnace through a first branch, an argon switch valve and an argon flow regulating valve are arranged on the argon source, and argon provided by the argon source enters the vacuum induction furnace through the first branch.
Specifically, the dry argon source is an argon tank, the argon tank is communicated with the bottom of the vacuum induction furnace through a first branch, an argon switch valve and an argon flow regulating valve are arranged on the first branch, and the argon switch valve and the argon flow regulating valve are respectively used for controlling the argon to be sprayed into the vacuum induction furnace and the flow of the argon to be sprayed.
Compared with the prior art, the argon blowing unit is arranged to blow argon into the vacuum induction furnace for vacuum stirring and degassing, so that N and H in molten iron are removed to be below 3 ppm.
In order to further enhance the degassing effect of argon stirring, the bottom of the vacuum induction furnace is provided with an argon blowing opening, the first branch is connected with the argon blowing opening, and the argon blowing opening is provided with a hollow cylindrical nozzle along the vertical direction, and the hollow cylindrical nozzle can rotate.
Specifically, in order to enhance the stirring effect and promote the molten iron to remove N and H gases, the hollow cylindrical nozzle is arranged at the argon blowing opening, argon in the argon tank passes through the first branch pipe and the argon blowing opening and then is sprayed into the molten iron through the hollow cylindrical nozzle, and the hollow cylindrical nozzle can rotate to generate a certain stirring effect on the molten iron so as to promote the molten iron to be degassed. It should be noted that the motor is arranged at the bottom of the vacuum induction furnace, the motor drives the hollow cylindrical nozzle to rotate through the transmission belt, and when the hollow cylindrical nozzle rotates, the argon sprayed into the molten iron can enable the molten iron to flow to a certain extent, so that the stirring effect of the hollow cylindrical nozzle is enhanced, and the degassing effect of removing N and H gases from the molten iron is improved.
In order to further enhance the degassing effect, the top surface of the hollow cylindrical nozzle is provided with a first stirring part, the first stirring part comprises a first U-shaped blade and a second U-shaped blade, and the first U-shaped blade and the second U-shaped blade are installed in opposite directions and are mutually embedded; the first stirring component is obliquely arranged on the hollow cylindrical nozzle; the inclination angle of the stirring component is 30-60 degrees.
Compared with the prior art, the first U-shaped blade and the second U-shaped blade are arranged on the first stirring part, and the first stirring part is inclined by 30-60 degrees, so that the stirring effect on molten iron can be realized to the greatest extent, and the degassing effect of the molten iron is better.
Similarly, in order to further enhance the degassing effect of molten iron, the top surface of the hollow cylindrical nozzle of the present invention is provided with a second stirring member, the second stirring member includes a first arcuate blade and a second arcuate blade, and the first arcuate blade and the second arcuate blade are disposed in parallel with each other and on the top surface of the hollow cylindrical nozzle.
Compared with the prior art, the second stirring component is arranged in a bow shape, and can also stir the molten iron, so that the degassing effect of the molten iron is better.
Example 1
This example illustrates the effect of smelting temperature on oxidative desulfurization and pre-reduction. Wherein, the selected iron ore concentrate powder has the components shown in Table 1, the total iron content is 67 percent, and the sulfur and phosphorus content is 0.01 percent. Taking CaO pure chemical reagent as a flux, and proportionally mixing iron ore concentrate powder and calcium oxide according to a binary alkalinity of 3.0.
TABLE 1 iron concentrate powder composition
| Composition (A) | TFe | FeO | Fe 2 O 3 | Al 2 O 3 | CaO | MgO | SiO 2 | P | S |
| Content (a) of | 67 | 1.04 | 94.6 | 0.64 | 0.89 | 0.68 | 2.61 | 0.03 | 0.01 |
Vacuum induction with 10kg of technical pure iron added to a capacity of 50kgThe furnace is used as an induction heating medium and is heated and melted in a vacuum state to form a molten iron pool, wherein the melting temperature is set to 1550-1700 ℃. After the pure iron is completely melted, 10kg of the mixture of the iron concentrate powder and the calcium oxide is blown into a molten iron bath, and the temperature is kept for 10min after the blowing is finished to ensure that the reaction is complete. Taking out the upper layer melt through a sampler, quenching the upper layer melt in liquid nitrogen, and respectively determining the sulfur content and Fe content of the slag sample through a carbon-sulfur analyzer and chemical titration analysis 3+ The content of the components is calculated, and the pre-reduction rate of the melt is calculated, and the result is shown in table 2.
Wherein, the calculation formula of the pre-reduction rate of the melt is as follows:
wherein: r-pre-reduction ratio of melt,%;
It can be seen from the above that, the increase of the smelting temperature is beneficial to promoting the oxidative desulfurization of the iron ore concentrate powder and the pre-reduction of the high-valence iron oxide, the sulfur content of the melt is reduced to 25ppm when the temperature reaches 1600 ℃, the pre-reduction rate reaches 97.2%, the change is not great when the temperature exceeds 1650 ℃, and the reduction temperature is preferably 1600-1650 ℃.
TABLE 2 influence of the melting temperature on the oxidative desulfurization and prereduction
Example 2
This example illustrates the alkalinity of slag versus the sulfur and oxygen content of molten ironWherein the iron ore concentrate powder and the calcium oxide flux are mixed according to the proportion of 2.0, 2.5, 3.0 and 3.5 of binary alkalinity. After pre-reduction is carried out according to the same procedure, pure hydrogen is sprayed into the molten pool through a hydrogen spray gun for final reduction, and the spraying amount of the hydrogen is H 2 The mol ratio of FeO/FeO is controlled to be 2, the blowing time is 30min, and the smelting temperature is 1650 ℃. The sulfur content and the oxygen content of the molten iron were measured by a carbon-sulfur analyzer and chemical analysis after the reduction reaction time was reached, and the results are shown in table 3.
It can be seen that the increase of the slag alkalinity has a favorable influence on both the desulfurization and the deoxidation of molten iron, the sulfur and oxygen contents of the molten iron are respectively lower than 10ppm and 30ppm when the alkalinity is controlled to be more than 2.5, and it needs to be noted that the influence on the deoxidation and the desulfurization effects is not great when the alkalinity reaches 3.0, so the alkalinity range is preferably 2.5 to 3.0.
TABLE 3 influence of slag basicity on sulfur and oxygen contents in molten iron
| Basicity of slag | 2.0 | 2.5 | 3.0 | 3.5 |
| Sulfur content% | 12 | 8 | 6 | 5 |
| Oxygen content% | 35 | 30 | 26 | 25 |
Example 3
In this example for explaining the influence of the argon blowing time on the contents of H and N in the molten iron, the molten iron in example 2 having a slag basicity of 3.0 and a melting temperature of 1650 ℃ was used, and argon gas was blown for vacuum degassing, the flow of argon gas was 5L/min, the blowing time was 5min, 10min, 15min, and 20min, and the contents of H and N in the molten iron were analyzed by sampling at different times, and the results are shown in table 4. It can be seen that the content of N and H in the molten iron is reduced to below 3ppm after the vacuum argon blowing time reaches 10min, and the argon blowing time is preferably 10-15 min.
TABLE 4 molten iron H, N content
Example 4
In this example, the same iron ore concentrate as in example 1 was used, and the iron ore concentrate of the composition shown in Table 1 was mixed with calcium oxide pure chemical reagent uniformly according to the basicity of 3.0 and sprayed into the molten iron bath by the spray gun system, the temperature of the molten bath was controlled at 1650 deg.C, after the pre-reduction process was completed, pure hydrogen was sprayed into the molten bath by the hydrogen spray gun for final reduction, and the amount of hydrogen sprayed was H 2 Controlling the mol ratio of FeO to be 2, blowing for 30min, blowing argon after the reduction reaction time is reached, and carrying out vacuum degassing, wherein the flow of the argon is 5L/min, and the blowing time is 10min. The contents of sulfur, phosphorus, oxygen, nitrogen, hydrogen and total iron in the molten iron were measured by a carbon-sulfur analyzer and chemical analysis, respectively, and the results are shown in table 5. It can be seen that a high purity iron product can be obtained by the preparation method of the present invention.
TABLE 5 molten iron chemical composition
| Composition (A) | TFe | O | N | H | P | S |
| Content (a) of | 99.985 | 0.0028 | 0.0003 | 0.0002 | 0.0006 | 0.0006 |
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (10)
1. The preparation method of the high-purity molten iron is characterized by comprising the following steps of:
step 1, adding industrial pure iron serving as an induction heating medium into a vacuum induction furnace, heating and melting at the temperature of 50-100 Pa and 1550-1700 ℃ in a vacuum state, and forming a molten iron bath after complete melting;
step 2, continuously spraying iron concentrate powder and lime flux into the molten iron melting pool in the step 1 for melting pre-reduction, and forming a melt after melting pre-reduction; after iron ore concentrate powder and lime fluxing agent are sprayed, hydrogen is sprayed into a molten iron bath through a hydrogen spraying unit arranged at the bottom of a vacuum reaction furnace, the hydrogen and a melt in the molten iron bath carry out a melting reduction reaction, molten slag generated by melting pre-reduction and molten slag generated by melting reduction reaction both float upwards and enter a first containing layer to form a molten slag layer, and molten iron generated by melting reduction reaction sinks into a third containing layer to form a molten iron layer; forming a slag-iron mixed layer between the slag layer and the molten iron layer; the slag-iron mixed layer is positioned in the second accommodating layer;
continuously spraying iron concentrate powder and lime melting agent into the formed slag-iron mixed layer, then spraying hydrogen into a molten iron layer through a hydrogen gas spraying and blowing port, heating the hydrogen by molten iron in the floating process, heating the hydrogen, then entering the slag-iron mixed layer, carrying out melting reduction reaction with the melt in the slag-iron mixed layer, continuously floating the slag generated by reduction to a molten slag layer, and continuously sinking the molten iron generated by reaction to the molten iron layer;
and 3, stopping blowing hydrogen, iron concentrate powder and lime flux when the molten iron in the molten iron layer is accumulated to a certain height to meet the tapping requirement, blowing argon into the molten iron layer through an argon blowing unit, performing vacuum stirring by using the argon to promote molten iron degassing, and tapping after the molten iron degassing to obtain high-purity molten iron.
2. The method of claim 1, wherein in the step 2, the iron ore concentrate powder and the lime flux are continuously injected into the molten iron bath through the injection unit after being mixed by the mixing unit.
3. The method of claim 1, wherein the binary basicity of the mixture of the iron ore concentrate powder and the lime flux is controlled to be in the range of 2.5 to 3.0 when the iron ore concentrate powder and the lime flux are proportioned by the batching unit in the step 2.
4. The method of claim 1, wherein the reduction temperature of the vacuum induction furnace in the step 2 is 1600 to 1650 ℃.
5. The method of claim 1, wherein the sulfur content of the melt produced by the melting pre-reduction is reduced to less than 25ppm in the step 2.
6. The method of claim 1, wherein the pre-reduction rate is 97.2-98.8%.
7. The method of claim 1, wherein in the step 2, the hydrogen injection time is 25 to 30min, and the amount of hydrogen injected is determined according to H 2 The mol ratio of the/FeO is controlled.
8. The method according to claim 1, wherein in the step 3, the vacuum stirring time is 10 to 15min, and N and H in the degassed molten iron are removed to less than 3 ppm.
9. The method of claim 1, wherein in the step 3, the blowing flow rate of the argon gas is 0.4 to 0.6L/(min-kg) Molten iron )。
10. The method of manufacturing a high purity molten iron according to claim 1, wherein a portion of the molten iron is always remained as a medium for vacuum induction heating after tapping in the step 3.
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