Comprehensive utilization method of iron ore

Abstract

The invention relates to the technical field of comprehensive utilization of resources, in particular to a comprehensive utilization method of iron ore. The comprehensive utilization method of the iron ore comprises the following steps: S1, preparing the iron ore into pellets and carrying out reduction reaction to obtain direct reduced iron; s2, the direct reduction iron is smelted, melt separation slag and molten iron are obtained, and the content of ferrous oxide in the melt separation slag is 1 wt%-4 wt%; and S3, directly preparing the melt separation slag into the rock wool on line when the melt separation slag is hot. Different from the prior art, the carbonaceous reducing agent is added in the smelting process, the content of ferrous oxide in the obtained melt separation slag is reduced, the heat preservation performance and the tensile mechanical performance of the prepared rock wool are improved, then the energy-saving effect, durability and safety of the rock wool are improved, meanwhile, the yield of obtained metal is increased, and the molten iron yield is increased; and the economic benefit is improved.

Description

Technical Field

[0001] The present application relates to the technical field of comprehensive utilization of resources, and specifically to a method for comprehensive utilization of iron ore. Background Art

[0002] The iron element of the steel industry mainly comes from iron ore. The production process of steel products using iron ore as raw material is mainly based on blast furnace ironmaking. Under the background of "double carbon", the non-blast furnace ironmaking process with gas-based vertical furnace as the core has lower carbon emissions and has received more attention and better development prospects because it does not require coking and sintering processes. In recent years, the world's direct reduced iron (DRI) production has grown steadily. With the continuous development of vertical furnaces and the continuous increase in direct reduced iron (DRI) production, vertical furnaces will face a situation where medium and low-grade iron ore is the main raw material.

[0003] After medium and low-grade iron ore enters the vertical furnace to produce medium and low-grade direct reduced iron (DRI), if it is directly added to the steelmaking electric arc furnace or converter like high-grade direct reduced iron (DRI), the removal of elements such as P and S requires high-basicity slag, which will lead to excessive slag, difficult operation, excessive energy consumption, long smelting cycle, high production cost and other problems. Therefore, medium and low-grade direct reduced iron (DRI) usually enters the melting furnace to produce molten iron and high-temperature molten slag, and then the molten iron is supplied to the steelmaking electric arc furnace or converter for steelmaking. The high-temperature molten slag (about 1400-1650℃) is usually cooled by hot pouring, water quenching and other methods and then used as cement raw material, resulting in a large waste of sensible heat. At the same time, there are also problems such as low product added value. It is urgent to develop a new method for high-value smelting of medium and low-grade iron ore to improve economic benefits.

[0004] Rock wool is a man-made fiber with excellent insulation, sound absorption, fire resistance and earthquake resistance. It is widely used in industries such as petroleum, electricity, metallurgy and construction. Its price is much higher than cement and its added value is high. The traditional raw materials for the preparation of rock wool are diabase and basalt. With the increasing scarcity of natural resources and the environmental damage caused by mining activities, and in order to reduce production costs, the use of industrial by-products or waste to produce rock wool has become an important research direction. Traditional molten slag such as blast furnace slag has too high alkalinity, and it is difficult to directly control the composition within the range suitable for the preparation of rock wool. When it is transported to the rock wool production workshop or sold to the rock wool manufacturer after cooling, it faces a large amount of waste of high-temperature molten slag and its sensible heat. Therefore, there are many studies on the use of traditional industrial molten slag to prepare slag wool with higher alkalinity. However, the water resistance, heat resistance, corrosion resistance and other properties of slag wool are far inferior to rock wool, and the added value is still relatively low. The patent document with publication number CN110818244A discloses a method for directly preparing rock wool by using electric furnace smelting sponge iron slag, which directly prepares rock wool by fiberizing the electric furnace smelting sponge iron slag (acidity coefficient greater than 1.5, containing 6-13% FeO). However, this method has very high requirements on the composition of sponge iron, so that molten slag directly used for producing rock wool can be obtained without adding any reducing agent and tempering agent, which is not conducive to industrial production. And this scheme adopts a smelting furnace for smelting (that is, the process of melting and reducing sponge iron in an electric furnace to obtain molten iron and molten slag), but the high-temperature melt and arc radiation generated by smelting will increase the temperature of the furnace bottom and furnace wall, aggravate the consumption of refractory materials, and affect the service life of the smelting furnace. In addition, the thermal insulation performance and mechanical properties of the rock wool obtained by this method need to be further improved. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the present invention provides a method for comprehensive utilization of iron ore to improve the economic benefits of medium and low-grade iron ore, extend the service life of the smelting furnace, and further improve the thermal insulation and mechanical properties of the prepared rock wool.

[0006] To achieve the above objectives, the scheme of this application is as follows:

[0007] The present application provides a method for comprehensive utilization of iron ore, comprising the following steps:

[0008] S1. The iron ore is pelletized and subjected to a reduction reaction to obtain direct reduced iron;

[0009] S2. mixing a carbonaceous reducing agent, a modifier and the direct reduced iron to obtain a mixture, smelting the mixture to obtain a molten slag and molten iron, wherein the ferrous oxide content of the molten slag is 1wt%-4wt%;

[0010] S3. directly making the molten slag into rock wool online while it is hot.

[0011] Optionally, the comprehensive utilization method of iron ore can be used to process medium and low grade iron ore.

[0012] In the present application, medium-low grade iron ore refers to iron ore with TFe < 67wt%, SiO2 > 3wt%, Al2O3 > 1wt%, CaO > 0.3wt% and MgO > 0.13wt%.

[0013] Optionally, in step S1, the reduction reaction is carried out in a gas-based vertical furnace.

[0014] Optionally, in step S2, the smelting is carried out in a smelting electric furnace.

[0015] Optionally, in step S2, the carbonaceous reducing agent, the modifier and the direct reduced iron are mixed and then smelted.

[0016] Optionally, in step S2, the carbonaceous reducing agent is selected from at least one of coke, coal powder and lignite.

[0017] Optionally, in the carbonaceous reducing agent in step S2, the fixed carbon content is 65wt%-85wt%.

[0018] Optionally, in step S2, the amount of the carbonaceous reducing agent used is 15-60 kg / t.

[0019] Optionally, in step S2, the amount of the modifier used is 10-50 kg / t.

[0020] Optionally, in step S2, the modifier is selected from lime or a mixture of lime and dolomite.

[0021] Optionally, the quaternary basicity of the molten slag in step S2 (i.e. the ratio of the sum of the mass of calcium oxide and magnesium oxide to the sum of the mass of silicon dioxide and aluminum oxide) is 0.55-0.65.

[0022] Optionally, in the molten slag of step S2, the silicon dioxide content is 29.5wt%-60.5wt%, the aluminum oxide content is 4.5wt%-25.5wt%, the calcium oxide content is 4.5wt%-30.5wt%, and the magnesium oxide content is 1.5wt%-15.5wt%.

[0023] Optionally, the smelting process in step S2 is carried out in a smelting device, in which a plurality of electrodes for heating are provided, and the carbonaceous reductant and / or the modifier and / or the direct reduced iron are placed around the electrodes and / or between the electrodes and / or around the inner wall of the smelting device.

[0024] Optionally, in the smelting process of step S2, the generated slag forms a condensed slag crust on the inner wall of the smelting equipment.

[0025] Optionally, during the smelting process in step S2, when a material pile is stacked around the inner wall of the smelting equipment, the generated slag forms a condensed slag crust on the inner wall of the smelting equipment, and the material pile is used to shield the arc and reduce the temperature near the furnace wall, so that the temperature of the slag when in contact with the furnace wall is lower than the solidification temperature of the slag, allowing the generated slag to form a condensed slag crust on the inner wall of the smelting equipment.

[0026] Optionally, during the smelting process in step S2, the molten iron forms a condensed iron layer on the furnace wall and the furnace bottom of the smelting equipment.

[0027] Optionally, during the smelting process in step S2, when the amount of iron retained at the bottom of the smelting equipment is greater than 500 kg, a temperature gradient will be formed so that the contact temperature between the molten iron and the furnace wall and bottom is lower than the solidification temperature of the molten iron, causing the molten iron to form a condensed iron layer on the furnace wall and bottom of the smelting equipment.

[0028] Optionally, the stockpile in step S2 includes the direct reduced iron and / or the carbonaceous reducing agent and / or the modifier.

[0029] Optionally, in step S2, the smelting temperature is 1400-1650°C.

[0030] Optionally, the method for comprehensive utilization of iron ore further comprises the following steps: refining the molten iron to produce steel products.

[0031] Beneficial effects of the present invention:

[0032] Different from the prior art, the present application adds a carbonaceous reducing agent during the smelting process, thereby reducing the ferrous oxide content in the molten slag obtained from the smelting, improving the thermal insulation performance and tensile mechanical properties of the produced rock wool, and thereby improving the energy-saving effect, durability and safety of the rock wool.

[0033] The present application adds a carbonaceous reducing agent during the smelting process, thereby reducing the ferrous oxide content in the molten slag obtained from the smelting, while increasing the degree of reduction and the metal recovery rate during the smelting process, increasing the output of molten iron, and improving the economic benefits.

[0034] Different from the prior art, the present application controls the composition of the slag by adding a modifier to make its basicity at a lower level (quaternary basicity is 0.55-0.65), which is convenient for directly preparing rock wool.

[0035] The method of the present application is adopted for production. During the smelting process, the carbonaceous reducing agent and / or modifier and / or direct reduced iron are placed around the electrodes and / or between the electrodes of the smelting equipment to form an arc-blocking material pile to accelerate the melting and reaction of the charge. A material pile is provided around the inner wall of the smelting equipment to further block the arc and reduce the temperature near the furnace wall, so that the temperature of the slag when in contact with the furnace wall is lower than the solidification temperature of the slag, and a condensed slag crust is formed on the furnace wall to protect the refractory material from corrosion, thereby extending the service life of the smelting equipment.

[0036] By adopting the method of the present application for production, the amount of iron retained at the bottom of the smelting equipment is greater than 500kg, and a temperature gradient can be formed (specifically, the smelting furnace is heated by electric heating, and its heat source is far away from the furnace wall and the furnace bottom. Therefore, the temperature of the upper material close to the electrode inside the smelting furnace is higher than the temperature of the lower material far away from the electrode, and the temperature of the furnace wall and the furnace bottom is lower than the temperature of the lower material, thereby forming a temperature gradient) so that the contact temperature of the molten iron with the furnace wall and the furnace bottom is lower than the solidification temperature of the molten iron, and a condensed iron layer is formed on the furnace wall and the furnace bottom to protect the refractory material from corrosion, thereby extending the service life of the smelting furnace.

[0037] Different from the prior art, the present application controls the composition of the slag by adding a modifier to make its basicity at a lower level (quaternary basicity is 0.55-0.65), which is convenient for directly preparing rock wool.

[0038] The present application can produce rock wool with excellent thermal insulation performance and tensile mechanical properties by controlling the dosage of the modifier within a specific range (10-50kg / t).

[0039] Different from the prior art, the present application innovatively discharges high-temperature molten slag through online tempering in a smelting furnace and uses it directly while hot to prepare rock wool, thereby maximizing the thermal and mass coupling utilization of the molten slag and its sensible heat, that is, utilizing the molten slag and its waste heat to directly produce rock wool while hot. The product has high added value, low rock wool production cost, simple and more economical process, thereby improving economic benefits. At the same time, since the molten slag in the conventional process is generally post-processed for the production of cement, glass and other products, and the preparation of rock wool requires the addition of slag conditioning agents, heating and other post-processing, the post-processing step of the molten slag is omitted.

[0040] Compared with the traditional technology of using blast furnace for production, the present application combines gas-based vertical furnace and smelting furnace to process medium and low-grade iron ore, eliminating the coking and sintering steps, achieving low-carbon production and green energy saving.

[0041] The present application solves the problem of increasing shortage of existing high-grade iron ore resources and achieves sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0043] Figure 1 This is a process flow chart of the comprehensive utilization method of medium and low grade iron ore of Examples 1-3. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. It should be noted that in this application, unless otherwise specified, "wt%" refers to mass percentage.

[0045] An embodiment of the present application provides a comprehensive utilization method of iron ore, which is used to process medium and low-grade iron ore, and comprises the following steps:

[0046] S1. The iron ore is pelletized and subjected to a reduction reaction in a gas-based shaft furnace to obtain direct reduced iron;

[0047] S2. A carbonaceous reducing agent, a modifier and direct reduced iron are mixed to obtain a mixture, and the mixture is smelted in a melting furnace at a temperature of 1400-1650° C., wherein a plurality of electrodes for heating are provided in the melting furnace, and the mixture is placed around the electrodes and / or between the electrodes and / or around the inner wall of the smelting equipment to obtain a molten slag and molten iron, wherein the molten slag has a silicon dioxide content of 29.5wt%-60.5wt%, an aluminum oxide content of 4.5wt%-25.5wt%, a calcium oxide content of 4.5wt%-30.5wt%, a magnesium oxide content of 1.5wt%-15.5wt%, and a ferrous oxide content of 1wt%-4wt%;

[0048] The carbonaceous reducing agent is selected from at least one of coke, coal powder and blue carbon, the amount of the carbonaceous reducing agent is 15-60 kg / t, and the fixed carbon content of the carbonaceous reducing agent is 65wt%-85wt%;

[0049] The modifier is selected from lime or a mixture of lime and dolomite, and the amount of the modifier is 10-50kg / t;

[0050] During the smelting process, when there is a pile of materials around the inner wall of the smelting furnace, the generated slag forms a condensed slag crust on the inner wall of the smelting furnace. When the amount of iron left at the bottom of the smelting furnace is greater than 500kg, the molten iron forms a condensed iron layer on the furnace wall and bottom of the smelting furnace.

[0051] The stockpile includes direct reduced iron and / or carbonaceous reducing agent and / or modifying agent;

[0052] S3. The molten slag is directly made into rock wool online while hot;

[0053] The molten iron is then made into steel products.

[0054] In the following description, numerous details are discussed to provide a more thorough explanation of embodiments of the present invention; however, it is apparent to one skilled in the art that embodiments of the present invention may be practiced without these specific details.

[0055] Example 1

[0056] like Figure 1 As shown, this embodiment provides a method for comprehensive utilization of medium and low-grade iron ore, and the specific steps are as follows:

[0057] S1. Medium-low grade iron ore (TFe 64.63wt%, SiO2 4.86wt%, Al2O3 1.01wt%, CaO 1.01wt%, MgO 0.15wt%) is made into pellets, and the obtained pellets are placed in a gas-based vertical furnace with a furnace temperature of 900°C, and a mixed gas of carbon monoxide and hydrogen (the volume ratio of carbon monoxide to hydrogen is 3:1, and the pressure of the mixed gas is 0.4MPa) is introduced into the gas-based vertical furnace. The pellets undergo a reduction reaction in the gas-based vertical furnace to obtain direct reduced iron (TFe 87.80wt%, SiO2 6.54wt%, Al2O3 1.36wt%, CaO 1.36wt%, MgO 0.2wt%, metallization rate 93%);

[0058] S2. The direct reduced iron is added to the melting furnace, and 46.45 kg / t of carbonaceous reducing agent coke (fixed carbon content of 80.48 wt%) and 24.90 kg / t of modifier lime are added to the melting furnace to obtain a mixture;

[0059] The mixture is smelted at a temperature of 1560°C. During the smelting process, the mixture is located around the electrodes and / or between the electrodes and / or around the inner wall of the smelting furnace to form an arc-blocking pile to accelerate the melting and reaction of the charge. Direct reduced iron, carbonaceous reducing agent coke and modifier lime are piled around the inner wall of the smelting furnace to form a pile to further block the arc and reduce the temperature near the furnace wall, so that the temperature of the slag when in contact with the furnace wall is lower than the solidification temperature of the slag, and a condensed slag crust is formed on the furnace wall to protect the refractory from corrosion, thereby extending the service life of the smelting furnace; the amount of iron left at the bottom of the smelting furnace is 850kg (i.e., the iron content of the adjacent previous batch is 1.575kg). After the first smelting is completed, the mixture formed by the molten slag and the molten iron is not discharged in full, but partially discharged, leaving 850 kg at the bottom of the smelting furnace, and the remaining part of the mixture formed by the molten slag and the molten iron is smelted together with the mixture of the next adjacent batch) to form a temperature gradient so that the contact temperature of the molten iron with the furnace wall and the furnace bottom is lower than the solidification temperature of the molten iron, and a condensed iron layer is formed on the furnace wall and the furnace bottom to protect the refractory from corrosion, thereby extending the service life of the smelting furnace; 147.25 kg / t molten slag (containing SiO247.96wt%, Al2O312.65wt%, CaO31.94wt%, MgO 4.42wt% and FeO 1.0wt%) and 910 kg / t molten iron are obtained. During the smelting process, the following reduction reactions mainly occur:

[0060] FeO+C=Fe+CO (1);

[0061] SiO2+2C=Si+2CO (2);

[0062] S3. The molten slag is directly drained and spun while hot to obtain rock wool fibers, and the rock wool fibers are sent to a cotton collecting chamber and a curing furnace for pressing to obtain 117.8 kg / t rock wool;

[0063] The molten iron is transferred to an electric arc furnace and subjected to processes such as refining, continuous casting and rolling to obtain 728kg / t steel billets.

[0064] Example 2

[0065] like Figure 1 As shown, this embodiment provides a method for comprehensive utilization of medium and low-grade iron ore, and the specific steps are as follows:

[0066] S1. Medium-low grade iron ore (TFe 61.35wt%, SiO2 6.28wt%, Al2O3 1.76wt%, CaO 1.23wt%, MgO 0.61wt%) is made into pellets, and the obtained pellets are placed in a gas-based vertical furnace with a furnace temperature of 900°C, and a mixed gas of carbon monoxide and hydrogen (the volume ratio of carbon monoxide to hydrogen is 3:1, and the pressure of the mixed gas is 0.4MPa) is introduced into the gas-based vertical furnace. The pellets undergo a reduction reaction in the gas-based vertical furnace to obtain direct reduced iron (TFe 81.79wt%, SiO2 8.29wt%, Al2O3 2.32wt%, CaO 1.62wt%, MgO 0.81wt%, and metallization rate 93%);

[0067] S2. The direct reduced iron is added to the melting furnace, and 42.77 kg / t of carbonaceous reducing agent coke (fixed carbon content of 80.48 wt%) and 40.91 kg / t of modifier lime are added to the melting furnace to obtain a mixture;

[0068] The mixture is smelted at a temperature of 1550°C. During the smelting process, the mixture is located around the electrodes and / or between the electrodes and / or around the inner wall of the smelting furnace to form an arc-blocking material pile; direct reduced iron, carbonaceous reducing agent coke and modifier lime are piled around the inner wall of the smelting furnace to form a material pile, and the amount of iron retained at the bottom of the smelting furnace is 800kg; 226.35kg / t smelting slag (containing SiO242.81wt%, Al2O313.78wt%, CaO 28.96wt%, MgO 5.0wt%, FeO1.0wt%) and 858kg / t molten iron are obtained. During the smelting process, the following reduction reactions mainly occur:

[0069] FeO+C=Fe+CO (1);

[0070] SiO2+2C=Si+2CO (2);

[0071] S3. The molten slag is directly drained and spun while hot to obtain rock wool fibers, which are sent to a cotton collecting chamber and a curing furnace for pressing to obtain 181.08 kg / t rock wool;

[0072] The molten iron is transferred to the converter for steelmaking, and after refining, continuous casting, rolling and other processes, 730kg / t steel billets are obtained.

[0073] Example 3

[0074] like Figure 1 As shown, this embodiment provides a method for comprehensive utilization of medium and low-grade iron ore, and the specific steps are as follows:

[0075] S1. Medium-low grade iron ore (TFe 61.35wt%, SiO2 6.28wt%, Al2O3 1.76wt%, CaO 1.23wt%, MgO 0.61wt%) is made into pellets, and the obtained pellets are placed in a gas-based vertical furnace with a furnace temperature of 900°C, and a mixed gas of carbon monoxide and hydrogen (the volume ratio of carbon monoxide to hydrogen is 3:1, and the pressure of the mixed gas is 0.4MPa) is introduced into the gas-based vertical furnace. The pellets undergo a reduction reaction in the gas-based vertical furnace to obtain direct reduced iron (TFe 81.79wt%, SiO2 8.29wt%, Al2O3 2.32wt%, CaO 1.62wt%, MgO 0.81wt%, and metallization rate 93%);

[0076] S2. The direct reduced iron is added to the melting furnace, and 27.62kg / t of carbonaceous reducing agent pulverized coal (fixed carbon content of 75.48wt%) and 44.42kg / t of modifier lime are added to the melting furnace to obtain a mixture;

[0077] The mixture is smelted at a temperature of 1500° C. During the smelting process, the mixture is located around the electrodes of the smelting furnace and / or between the electrodes and / or the inner wall of the smelting furnace to form an arc-blocking material pile; direct reduced iron, carbonaceous reducing agent pulverized coal and modifier lime are piled around the inner wall of the smelting furnace to form a material pile, and the amount of iron retained at the bottom of the smelting furnace is 750 kg; 236.68 kg / t smelting slag (containing SiO2 41.42 wt%, Al2O3 12.99 wt%, CaO 30.37 wt%, MgO 5.0 wt% and FeO2.0 wt%) and 843 kg / t molten iron are obtained. During the smelting process, the following reduction reactions mainly occur:

[0078] FeO+C=Fe+CO (1);

[0079] SiO2+2C=Si+2CO (2);

[0080] S3. The molten slag is directly drained and spun while hot to obtain rock wool fibers, which are sent to a cotton collecting chamber and a curing furnace for pressing to obtain 201.18 kg / t rock wool;

[0081] The molten iron is transferred to an electric arc furnace and subjected to processes such as refining, continuous casting and rolling to obtain 717kg / t steel billets.

[0082] Comparative Example 1

[0083] The production was carried out in the same manner as in Example 3 except for the following conditions:

[0084] S2. The direct reduced iron was added to the melting furnace, and 44.42kg / t of lime modifier was added to the melting furnace to obtain a mixture;

[0085] The mixture is smelted at a temperature of 1500° C. During the smelting process, the mixture is located around the electrodes and / or between the electrodes of the smelting furnace to form an arc-blocking material pile; direct reduced iron, carbonaceous reducing agent coal powder and modifier lime are piled around the inner wall of the smelting furnace to form a material pile, and the amount of iron left at the bottom of the smelting furnace is 750 kg; 252 kg / t smelting slag (containing SiO2 41.38 wt%, Al2O3 11.76 wt%, CaO 27.68 wt%, MgO 4.2 wt% and FeO 7.0 wt%) and 815 kg / t molten iron are obtained. During the smelting process, the following reduction reactions mainly occur:

[0086] FeO+C=Fe+CO (1);

[0087] SiO2+2C=Si+2CO (2);

[0088] S3. The molten slag is directly drained and spun while hot to obtain rock wool fibers, and the rock wool fibers are sent to a cotton collecting chamber and a curing furnace for pressing to obtain 214.50 kg / t rock wool.

[0089] That is, no carbonaceous reducing agent was added during the smelting process of this comparative example, and the FeO content in the molten slag obtained by smelting was 7.0wt%.

[0090] Comparative Example 2

[0091] The production was carried out in the same manner as in Example 3 except for the following conditions:

[0092] S2. The direct reduced iron is added to the melting furnace, and 27.62kg / t of carbonaceous reducing agent pulverized coal (fixed carbon content of 75.48wt%) and 60kg / t of modifier lime are added to the melting furnace to obtain a mixture;

[0093] The mixture is smelted at a temperature of 1510°C. During the smelting process, the mixture is located around the electrodes of the smelting furnace and / or between the electrodes and / or the inner wall of the smelting furnace to form an arc-blocking material pile; direct reduced iron, carbonaceous reducing agent pulverized coal and modifier lime are piled around the inner wall of the smelting furnace to form a material pile, and the amount of iron retained at the bottom of the smelting furnace is 750kg; 246.67kg / t smelting slag (containing SiO239.87wt%, Al2O312.53wt%, CaO34.97wt%, MgO4.3wt% and FeO0.5wt%) and 841.44kg / t molten iron are obtained. During the smelting process, the following reduction reactions mainly occur:

[0094] FeO+C=Fe+CO (1);

[0095] SiO2+2C=Si+2CO (2);

[0096] S3. The molten slag is directly drained and spun while hot to obtain rock wool fibers, and the rock wool fibers are sent to a cotton collecting chamber and a curing furnace for pressing to obtain 209.67 kg / t rock wool;

[0097] The molten iron is transferred to an electric arc furnace and subjected to processes such as refining, continuous casting and rolling to obtain 715kg / t steel billets.

[0098] That is, the amount of the modifier added during the smelting process of this comparative example is adjusted to 60 kg / t.

[0099] Performance Testing

[0100] The thermal conductivity and compressive strength of the rock wool obtained in Examples 1-3 and Comparative Examples 1-2 were tested, and the results are shown in Table 1;

[0101] Among them, the thermal conductivity is tested in accordance with GB / T 10295-2008 Determination of Steady-State Thermal Resistance and Related Properties of Insulation Materials - Heat Flow Meter Method;

[0102] The tensile strength is tested in accordance with GB / T 30804-2014 Determination of tensile strength of thermal insulation products for building perpendicular to the surface.

[0103] Table 1 Test results

[0104] Group Thermal conductivity, W / (m·K) Tensile strength, kPa Example 1 0.032 28 Example 2 0.033 26 Example 3 0.034 23 Comparative Example 1 0.038 16 Comparative Example 2 0.037 18

[0105] As shown in Table 1, compared with Comparative Example 1 (the ferrous oxide content in the molten slag is 7.0%), the thermal conductivity of Example 3 (the ferrous oxide content in the molten slag is 2.0wt%) is reduced and the tensile strength is increased. This result shows that the present application improves the thermal insulation performance and tensile mechanical properties of the obtained rock wool by reducing the ferrous oxide content in the molten slag obtained by smelting.

[0106] As shown in Table 1, compared with Comparative Example 2 (modifier dosage of 60 kg / t), Example 3 (modifier dosage of 44.42 kg / t) has a reduced thermal conductivity and a reduced tensile strength. This result shows that the present application can produce rock wool with excellent thermal insulation performance and tensile mechanical properties by controlling the dosage of the modifier in the smelting process within a specific range (10-50 kg / t).

[0107] It can be seen from Example 3 and Comparative Example 1 that the molten iron output of Example 3 (the ferrous oxide content in the molten slag is 2.0wt%) is increased compared with Comparative Example 1 (the ferrous oxide content in the molten slag is 6.1%). This result shows that the present application can increase the degree of reduction and the metal recovery rate during the smelting process by reducing the ferrous oxide content in the molten slag obtained by smelting and adding a carbonaceous reducing agent during the smelting process, thereby increasing the molten iron output.

[0108] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for comprehensive utilization of iron ore, characterized in that: The steps include: S1. The iron ore is pelletized and subjected to a reduction reaction to obtain direct reduced iron; S2. The direct reduced iron is smelted to obtain molten slag and molten iron, wherein the ferrous oxide content of the molten slag is 1wt%-4wt%; S3. directly making the molten slag into rock wool online while it is hot.

2. The comprehensive utilization method of iron ore according to claim 1, characterized in that: The comprehensive utilization method is used to process medium and low grade iron ore; And / or, in step S1, the reduction reaction is carried out in a gas-based vertical furnace.

3. The comprehensive utilization method of iron ore according to claim 1, characterized in that: In step S2, a carbonaceous reducing agent, a modifier and the direct reduced iron are mixed and then smelted; And / or, in step S2, the smelting is carried out in a smelting electric furnace; And / or, in the molten slag of step S2, the silicon dioxide content is 29.5wt%-60.5wt%, the aluminum oxide content is 4.5wt%-25.5wt%, the calcium oxide content is 4.5wt%-30.5wt%, and the magnesium oxide content is 1.5wt%-15.5wt%.

4. The comprehensive utilization method of iron ore according to claim 3, characterized in that: In step S2, the carbonaceous reducing agent is selected from at least one of coke, coal powder and semi-coke; And / or, the carbonaceous reducing agent in step S2 has a fixed carbon content of 65wt%-85wt%; And / or, in step S2, the amount of the carbonaceous reducing agent used is 15-60 kg / t.

5. The comprehensive utilization method of iron ore according to claim 3, characterized in that: In step S2, the modifier is selected from lime or a mixture of lime and dolomite; And / or, in step S2, the amount of the modifier used is 10-50 kg / t.

6. The comprehensive utilization method of iron ore according to claim 3, characterized in that: The smelting process in step S2 is carried out in a smelting device, in which a plurality of electrodes for heating are arranged, and the carbonaceous reducing agent and / or the modifier and / or the direct reduced iron are placed around the electrodes and / or between the electrodes and / or around the inner wall of the smelting device.

7. The comprehensive utilization method of iron ore according to claim 3, characterized in that: During the smelting process in step S2, the generated slag forms a condensed slag crust on the inner wall of the smelting equipment; And / or, during the smelting process in step S2, the molten iron forms a condensed iron layer on the furnace wall and the furnace bottom of the smelting equipment.

8. The comprehensive utilization method of iron ore according to claim 7, characterized in that: In the smelting process of step S2, when a material pile is piled around the inner wall of the smelting equipment, the generated slag forms a condensed slag shell on the inner wall of the smelting equipment; And / or, during the smelting process in step S2, when the amount of iron remaining at the bottom of the smelting equipment is greater than 500 kg, the molten iron forms a condensed iron layer on the furnace wall and the furnace bottom of the smelting equipment.

9. The comprehensive utilization method of iron ore according to claim 8, characterized in that: In step S2, the stockpile includes the direct reduced iron and / or the carbonaceous reducing agent and / or the modifier.

10. The comprehensive utilization method of iron ore according to claim 1, characterized in that: The following steps are also included: The molten iron is refined to produce steel products.

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