Method for direct reduction of iron by potassium-sodium-fluorine-containing magnetite hydrogen-based shaft furnace

Abstract

The application discloses a kind of potassium sodium fluorite magnetite hydrogen-based shaft furnace direct reduction iron-making methods, specifically comprising: according to mass percentage, potassium sodium fluorite magnetite concentrate: 60%-70%, ordinary iron concentrate: 30%-40%, outside matching bentonite: 3.0%-3.5% are placed in mixer, so that pelletizing raw materials are mixed uniformly;With the pelletizing mixture as raw material, 12-16mm green ball is prepared on disc pelletizer by spraying water;Green ball is obtained after drying, preheating, oxidizing roasting oxidized pellet, and then the oxidized pellet is added from the top of hydrogen-based shaft furnace to carry out direct reduction in hydrogen-based shaft furnace;Reduced metallized pellet is placed in vacuum medium frequency induction furnace and is smelted and separated.The purpose of the present application is to provide a kind of potassium sodium fluorite magnetite hydrogen-based shaft furnace direct reduction iron-making method, and the development of potassium sodium fluorite magnetite hydrogen-based shaft furnace direct reduction iron-making process is an important technical approach for efficient utilization of potassium sodium fluorite magnetite, and has important practical significance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of non-blast furnace ironmaking, and particularly relates to a method for hydrogen-based shaft furnace direct reduction ironmaking of potassium-sodium-fluorine-containing magnetite. BACKGROUND

[0002] In China, crude steel is mainly produced by a blast furnace-converter process, in which the blast furnace ironmaking production as a whole covers sintering, pelletizing, coking and blast furnace ironmaking processes, and has the characteristics of long production process, high energy consumption and large pollutant emission. Specifically, the CO2 emission of the blast furnace ironmaking whole process accounts for more than 80% of the CO2 emission of the crude steel production whole process, and the energy consumption accounts for more than 70%. Therefore, the blast furnace ironmaking is the key object of energy saving and emission reduction for domestic steel enterprises, and the development and application of new low-carbon ironmaking processes are the direction of green and sustainable development of the steel industry.

[0003] Generally, the blast furnace ironmaking production requires that the ironmaking raw materials have good metallurgical properties to promote the stable operation of the blast furnace and achieve the strengthening smelting level of technical and economic indicators. However, when the blast furnace smelts potassium-sodium-fluorine-containing magnetite, due to the characteristics of the mineral, the sinter drum strength is low, the low-temperature reduction pulverization performance is poor, the compressive strength and reduction swelling of the oxidized pellet are difficult to control, and the potassium, sodium and fluorine components form a circulating enrichment in the blast furnace, resulting in a wide softening zone of the blast furnace, poor permeability, intensified coke dissolution and loss, and weakened role of the material column skeleton, which leads to poor technical and economic indicators of the blast furnace ironmaking, intensified CO2 emission per ton of iron, and inability of the blast furnace ironmaking production to apply a large proportion of fluorine-containing potassium-sodium magnetite (about 45% of the proportion of the blast furnace). It is urgent to apply a mature and efficient, stable and large-scale industrial technology to realize large-scale utilization of potassium-sodium-fluorine-containing magnetite.

[0004] The hydrogen-based shaft furnace direct reduction technology is a production process in which H2 and CO are used as the main reducing agents to reduce the iron oxides in the iron ore at a non-melting temperature in a shaft furnace to obtain sponge iron, and has the advantages of short production process (no sintering and coking process), high automation degree, stable production operation, mature process, high reduction efficiency, low energy consumption, less pollutant emission (especially less CO2 emission), and high-quality and pure product. The steel short process production process formed by the combination of the electric furnace is an important technical development direction for realizing low-carbon steel industry in China. SUMMARY

[0005] Based on the green and low-carbon development demand of the steel industry in China, the technical problems existing in the blast furnace smelting of potassium-sodium-fluorine-containing magnetite, and the technical characteristics of the hydrogen-based shaft furnace direct reduction, the purpose of the present application is to provide a method for hydrogen-based shaft furnace direct reduction ironmaking of potassium-sodium-fluorine-containing magnetite. The development of the hydrogen-based shaft furnace direct reduction ironmaking process of potassium-sodium-fluorine-containing magnetite is an important technical approach for efficient utilization of potassium-sodium-fluorine-containing magnetite, and has important practical significance.

[0006] To solve the above technical problems, the application adopts the following technical solutions:

[0007] The application discloses a method for directly reducing and smelting iron by using potassium-sodium-fluorine-containing magnetite and hydrogen in a shaft furnace, and specifically comprises the following steps.

[0008] (1) According to the mass percentage, the potassium-sodium-fluorine-containing magnetite concentrate is 60-70%, the ordinary iron concentrate is 30-40%, and the bentonite is 3.0-3.5%, which are placed in a planetary mixer to uniformly mix the balling raw materials.

[0009] (2) The mixed balling materials are used as raw materials to prepare green balls with a diameter of 12-16 mm by spraying water on a disc balling machine, the green balls have a compression strength higher than 10 N / piece, a falling strength not lower than 4 times, and a water content of 8-10% by mass; the green balls are dried at 120-180 DEG C for 40-60 min to obtain dried balls with a compression strength not lower than 100 N / piece; the dried balls are preheated at 600-800 DEG C for 10-15 min to obtain preheated balls with a compression strength not lower than 800 N / piece; and the preheated balls are further calcined at 1220-1250 DEG C for 15-20 min to obtain finished oxidized pellets with a compression strength not lower than 2500 N / piece.

[0010] (3) The oxidized pellets are added into a hydrogen-based shaft furnace from the top of the furnace for direct reduction, the reduction temperature is controlled to be 950-1050 DEG C, the reduction pressure in the furnace is 0.5-0.6 MPa, the reduction gas flow rate is 3-5 m 3 / m 2 ·min, the volume ratio of H2+CO in the reduction gas is not lower than 95%, the molar ratio of H2 to CO is 4-6, and the reduction time is not lower than 40 min, so that the metallized pellets obtained finally have a metallization rate higher than 92% and a reduction expansion rate lower than 20%.

[0011] (4) The metallized pellets after reduction are placed in a vacuum medium-frequency induction furnace for smelting, the smelting temperature is controlled to be 1600-1650 DEG C, the smelting time is 30-50 min, the smelting slag basicity is controlled to be 0.8-1.0 by adding calcium flux, and finally the smelted metal lumps and smelting slag are obtained; the iron grade of the smelted metal lumps is not lower than 99.5%, and the iron recovery rate is higher than 90%.

[0012] Further, the chemical composition of the potassium-sodium-fluorine-containing magnetite concentrate includes, in percentage by mass: 64.50-68.50% of TFe, 26.00-30.00% of FeO, 0.50-2.00% of CaO, 1.00-4.00% of SiO2, 0.50-2.00% of MgO, 0.10-0.80% of Al2O3, 0.05-0.30% of K2O, 0.10-0.25% of Na2O, 0.20-0.40% of F, 0.30-1.00% of S, and the proportion of the iron concentrate with a particle size less than 0.074 mm is 80-95%.

[0013] Further, the chemical composition of the ordinary iron concentrate includes, in percentage by mass: 62.00-64.00% of TFe, 25.00-29.00% of FeO, 0.20-0.60% of CaO, 2.00-4.00% of SiO2, 0.50-1.00% of MgO, 1.00-2.00% of Al2O3, and the proportion of the iron concentrate with a particle size less than 0.074 mm is 80-95%.

[0014] Further, the chemical composition of the bentonite includes, in percentage by mass: 1.00-4.00% of CaO, 61.00-68.00% of SiO2, 1.00-4.00% of MgO, 13.00-15.00% of Al2O3, 1.00-3.00% of K2O, 1.00-3.00% of Na2O, and the proportion of the bentonite with a particle size less than 0.074 mm is higher than 98%.

[0015] Further, compared with the production process of smelting the potassium-sodium-fluorine-containing magnetite by a blast furnace, the hydrogen-based shaft furnace direct reduction ironmaking process of the potassium-sodium-fluorine-containing magnetite is short, does not involve a sintering process and a coking process, reduces the dependence of smelting production on coking coal resources, and is clean and low in environmental load.

[0016] Further, the molten metal block iron obtained can be directly used as a base material for producing high-value-added steel.

[0017] Further, under the hydrogen-rich reduction condition of the hydrogen-based shaft furnace, the reduction expansion rate of the pellet is lower than that under the reduction atmosphere of the blast furnace, thereby improving the application proportion of the potassium-sodium-fluorine-containing magnetite in ironmaking production.

[0018] Compared with the prior art, the beneficial technical effects of the present application are:

[0019] Compared with the production process of the potassium-sodium-fluorine-containing magnetite by blast furnace smelting, the technical advantage of the application lies in that the hydrogen-based shaft furnace direct reduction ironmaking process of the potassium-sodium-fluorine-containing magnetite is short, does not involve sintering process and coking process, can reduce the dependence of smelting production on coking coal resources, the overall process is clean, the environmental load is low, meets the demand of the national steel industry for green and low-carbon development, and the molten metal block iron obtained can be directly used as a base material for producing high-value-added steel. In addition, under the hydrogen-rich reduction condition of the hydrogen-based shaft furnace, the reduction expansion rate of the pellet is lower than that under the reduction atmosphere of the blast furnace, and thus the application proportion of the potassium-sodium-fluorine-containing magnetite in ironmaking production can be improved. DETAILED DESCRIPTION

[0020] The technical scheme of the application will be described in detail below in combination with examples.

[0021] Example 1

[0022] The particle size composition and the chemical component analysis according to the mass percentage of the potassium-sodium-fluorine-containing magnetite concentrate, the ordinary iron concentrate and the externally added bentonite binder used in the example of the application are shown in Table 1.

[0023] Table 1 Chemical components of the iron ore powder and bentonite used in the example / %

[0024]

[0025] The implementation steps are as follows:

[0026] (1) According to the mass percentage, the potassium-sodium-fluorine-containing magnetite concentrate 60%, the ordinary iron concentrate 40% and the externally added bentonite 3.0% are placed in a planetary mixer to mix the balling raw materials uniformly;

[0027] (2) Further, the balling mixture is used as the raw material to prepare green balls of 12-16 mm on a disc balling machine by spraying water, the green ball compression strength is higher than 10 N / piece, the falling strength is not less than 4 times, and the water mass percentage is controlled to be 8%-10%. The green balls are dried at 150℃ for 60 min to obtain dried balls, and the dried ball compression strength reaches 135 N / piece. The dried balls are preheated at 800℃ for 12 min to obtain preheated balls, and the preheated ball compression strength reaches 865 N / piece. The preheated balls are further calcined at 1220℃ for 15 min to obtain finished oxidized pellet, and the finished pellet compression strength reaches 2816 N / piece.

[0028] (4) Further, the oxidized pellet is added into the hydrogen-based shaft furnace from the top of the furnace for direct reduction. The reduction temperature is controlled to be 1050℃, the reduction pressure in the furnace is 0.55 MPa, the reduction gas flow rate is 3 m 3 / m 2• min, H2+CO volume ratio in the reducing gas is 95%, H2 / CO molar ratio is 5, and the reduction time is 50 min. The metallization rate of the metallized pellets obtained finally is 92.1%, and the reduction expansion rate is 18.9%.

[0029] (5) Further, the reduced metallized pellets are placed in a vacuum medium-frequency induction furnace for smelting. The smelting temperature is controlled at 1600℃, the smelting time is 40 min, the smelting slag basicity is controlled at 0.8 by adding calcium flux, and finally the smelting metal lumps and smelting slag are obtained. The iron grade of the smelting metal lumps is 99.58%, and the iron recovery rate is 90.36%.

[0030] Example 2

[0031] In this example, the iron ore concentrate and bentonite used in Example 1 are used as raw materials. The specific implementation steps are as follows:

[0032] (1) According to the mass percentage, 65% of potassium-sodium-fluorine-containing magnetite concentrate, 35% of ordinary iron ore concentrate, and 3.2% of externally added bentonite are placed in a planetary mixer to mix the pelletizing raw materials uniformly;

[0033] (2) Further, the pelletizing mixture is used as raw material to prepare 12-16mm green pellets on a disc pelletizer by spraying water. The green pellet compressive strength is higher than 10N / pellet, the drop strength is not less than 4 times, and the water content is controlled at 8%-10%. The green pellets are dried at 150℃ for 60 min to obtain dried pellets with a compressive strength of 126N / pellet. The dried pellets are preheated at 800℃ for 12 min to obtain preheated pellets with a compressive strength of 846N / pellet. The preheated pellets are further calcined at 1220℃ for 15 min to obtain finished oxidized pellets with a compressive strength of 2739N / pellet.

[0034] (4) Further, the oxidized pellets are added from the top of the hydrogen-based shaft furnace for direct reduction. The reduction temperature is controlled at 1000℃, the furnace reduction pressure is 0.60MPa, the reducing gas flow rate is 4m 3 / m 2 • min, H2+CO volume ratio in the reducing gas is 95%, H2 / CO molar ratio is 5, and the reduction time is 50 min. The metallization rate of the metallized pellets obtained finally is 92.1%, and the reduction expansion rate is 18.9%.

[0035] (5) Further, the reduced metallized pellets are placed in a vacuum medium-frequency induction furnace for smelting. The smelting temperature is controlled at 1600℃, the smelting time is 40 min, the smelting slag basicity is controlled at 0.8 by adding calcium flux, and finally the smelting metal lumps and smelting slag are obtained. The iron grade of the smelting metal lumps is 99.58%, and the iron recovery rate is 90.36%.

[0036] Example 3

[0037] This example still uses the iron concentrate and bentonite used in Example 1 as raw materials. The specific implementation steps are as follows:

[0038] (1) According to the mass percentage, put the potassium sodium fluorine containing magnetite concentrate 70%, ordinary iron concentrate 30% and external bentonite 3.5% into the planetary mixer, and mix the balling raw materials uniformly;

[0039] (2) Further, take the balling mixture as raw material, and prepare 12-16mm green balls on the disc balling machine by spraying water, the green ball compression strength is higher than 10N / each, the falling strength is not less than 4 times, and the moisture mass percentage is controlled to be 8%-10%. The green balls are dried at 150℃ for 60min to obtain dried balls, the dried ball compression strength reaches 128N / each. The dried balls are preheated at 800℃ for 12min to obtain preheated balls, the preheated ball compression strength reaches 873N / each. The preheated balls are further roasted at 1250℃ for 20min to obtain finished oxidized pellets, and the finished pellet compression strength reaches 3087N / each.

[0040] (4) Further, the oxidized pellets are added from the top of the furnace into the hydrogen-based shaft furnace for direct reduction. The reduction temperature is controlled to be 950℃, the furnace reduction pressure is 0.60MPa, the reduction gas flow rate is 5m 3 / m 2 ·min, the H2+CO volume ratio in the reduction gas is 97%, the H2 and CO molar ratio is 6, and the reduction time is 60min. The final obtained metallized pellets have a metallization rate of 94.3% and a reduction expansion rate of 17.6%.

[0041] (5) Further, the reduced metallized pellets are placed in a vacuum medium frequency induction furnace for smelting. The smelting temperature is controlled to be 1650℃, the smelting time is 30min, and the smelting slag basicity is controlled to be 1.0 by adding calcium flux. Finally, smelting metal blocks and smelting slag are obtained. The smelting metal block has an iron grade of 99.88% and an iron recovery rate of 93.20%.

[0042] The above-described examples only describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for direct reduction of iron by potassium sodium fluor-magnetite hydrogen-based shaft furnace, characterized by, Specifically comprising the following steps: (1) according to the mass percentage, put the potassium sodium fluorine-containing magnetite concentrate: 60%-70%, ordinary iron concentrate: 30%-40%, and externally added bentonite: 3.0%-3.5% into a mixer to mix the balling raw materials uniformly; (2) using the balling mixture as raw material, 12-16mm green balls are prepared on a disc balling machine by spraying water, the green ball compression strength is higher than 10N / each, the falling strength is not less than 4 times, the moisture content is controlled to be 8%-10%, the green balls are dried at 120-180℃ for 40-60min to obtain dried balls, the dried ball compression strength is not less than 100N / each; the dried balls are preheated at 600-800℃ for 10-15min to obtain preheated balls, the preheated ball compression strength is not less than 800N / each; the preheated balls are further roasted at 1220-1250℃ for 15-20min to obtain finished oxidized pellets, the finished pellet compression strength is not less than 2500N / each; (3) adding oxidized pellets from the top of the shaft furnace into the hydrogen-based shaft furnace for direct reduction; the reduction temperature is controlled at 950-1050°C, the reduction pressure in the furnace is 0.5-0.6 MPa, the reduction gas flow rate is 3-5 m 3 / m 2 ·min, the volume ratio of H2+CO in the reduction gas is not less than 95%, the molar ratio of H2 to CO is 4-6, and the reduction time is not less than 40 min, and the final obtained metallized pellets meet the requirements that the metallization rate is higher than 92% and the reduction expansion rate is lower than 20%. (4) the reduced metallized pellets are placed in a vacuum medium frequency induction furnace for smelting; the smelting temperature is controlled to be 1600-1650℃, the smelting time is 30-50min, the smelting slag basicity is controlled to be 0.8-1.0 by adding calcium flux, and finally the smelting metal blocks and smelting slag are obtained; the iron grade of the smelting metal blocks is not less than 99.5%, and the iron recovery rate is higher than 90%.

2. The method of direct reduction of iron ore by potassium sodium fluornatite hydrogen based shaft furnace as claimed in claim 1 wherein, The potassium sodium fluorine-containing magnetite concentrate has the following chemical components according to the mass percentage: 64.50-68.50% of TFe, 26.00-30.00% of FeO, 0.50-2.00% of CaO, 1.00-4.00% of SiO2, 0.50-2.00% of MgO, 0.10-0.80% of Al2O3, 0.05-0.30% of K2O, 0.10-0.25% of Na2O, 0.20-0.40% of F, 0.30-1.00% of S, and the proportion of the iron concentrate with a particle size less than 0.074mm is 80-95%.

3. The method of direct reduction of iron ore by potassium sodium fluornatite hydrogen based shaft furnace as claimed in claim 1 wherein, The ordinary iron concentrate has the following chemical components according to the mass percentage: 62.00-64.00% of TFe, 25.00-29.00% of FeO, 0.20-0.60% of CaO, 2.00-4.00% of SiO2, 0.50-1.00% of MgO, 1.00-2.00% of Al2O3, and the proportion of the iron concentrate with a particle size less than 0.074mm is 80-95%.

4. The method of direct reduction of iron ore by potassium sodium fluornatite hydrogen based shaft furnace as claimed in claim 1 wherein, The bentonite has the following chemical components according to the mass percentage: 1.00-4.00% of CaO, 61.00-68.00% of SiO2, 1.00-4.00% of MgO, 13.00-15.00% of Al2O3, 1.00-3.00% of K2O, 1.00-3.00% of Na2O, and the proportion of the bentonite with a particle size less than 0.074mm is higher than 98%.

5. The method of direct reduction of iron ore by potassium sodium fluomagnetite hydrogen-based shaft furnace as claimed in claim 1, wherein, Compared with the production process of potassium-sodium-fluorine-containing magnetite by blast furnace smelting, the hydrogen-based shaft furnace direct reduction ironmaking process of potassium-sodium-fluorine-containing magnetite has a short process flow, does not involve sintering process and coking process, reduces the dependence of smelting production on coking coal resources, and has a clean overall process flow and low environmental load.

6. The method of direct reduction of iron ore by potassium sodium fluornatite hydrogen based shaft furnace as claimed in claim 1 wherein, The obtained fused metal blocks can be directly used as a base material for producing high-value-added steel.

7. The method of direct reduction of iron ore by potassium sodium fluornatite hydrogen based shaft furnace as claimed in claim 1 wherein, Under the rich hydrogen reduction condition of the hydrogen-based shaft furnace, the reduction expansion rate of the pellet is lower than that under the blast furnace reduction atmosphere, thereby improving the application proportion of potassium-sodium-fluorine-containing magnetite in ironmaking production.

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