Method for preparing ferromolybdenum alloy by combining hydrogen-based vertical furnace reduction and electric furnace smelting

Abstract

The present invention discloses a method for preparing ferromolybdenum alloy by hydrogen-based vertical furnace reduction and electric furnace smelting, comprising the following steps: (1) mixing iron concentrate powder with molybdenum oxide powder, bentonite and slaked lime, and pelletizing to obtain green balls; (2) drying and roasting the green balls to prepare oxidized pellets; (3) reducing the oxidized pellets with hydrogen-rich gas in a hydrogen-rich reduction vertical furnace to obtain molybdenum-containing DRI; (4) cooling the molybdenum-containing DRI under the protection of inert gas; (5) subjecting the cooled molybdenum-containing DRI to electric furnace smelting and separation to obtain ferromolybdenum alloy. The method adopts hydrogen-based vertical furnace-electric furnace smelting to produce ferromolybdenum alloy, reducing process energy consumption and pollutant emissions; slaked lime is added during the pellet preparation process to react with molybdenum oxide powder to form a calcium molybdate stable compound, thereby inhibiting the high-temperature volatilization of molybdenum oxide and improving the pelletizing performance of molybdenum-containing pellets.

Description

Technical Field

[0001] The present invention relates to a method, in particular to a method for preparing ferromolybdenum alloy by combining hydrogen-based shaft furnace reduction and electric furnace smelting. Background Art

[0002] Molybdenum-containing steel has good strength, toughness, oxidation resistance and corrosion resistance. It has been widely used in special steels such as stainless steel and tool steel. Molybdenum-containing steel usually uses ferromolybdenum as an alloying agent to achieve molybdenum alloying during the steelmaking process, with a high yield and a stable production process. At present, there are two methods for producing ferromolybdenum at home and abroad. One is to use carbon as a reducing agent to smelt in an electric furnace, which is called the "agglomeration method"; the other is the metal thermal reduction method outside the furnace, which is more widely used, that is, the silicon-aluminum thermal reduction method is used to smelt ferromolybdenum. The raw materials used for smelting are: oxides-roasted molybdenum concentrate and iron scale, reducing agents-ferrosilicon and aluminum powder, flux-calcium oxide, iron scale, heat supplement-saltpeter and ferroalloy grade regulator-steel scraps, with ferrosilicon and aluminum particles as reducing agents. Both processes have the problems of high energy consumption and environmental pollution.

[0003] Under the constraint of the “dual carbon” goal, replacing carbon with hydrogen is a hot research topic in the current metallurgical field. The hydrogen reduction product is H 2 O, friendly to the environment. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing ferromolybdenum alloy by combining hydrogen-based vertical furnace reduction and electric furnace smelting with low energy consumption.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention includes the following steps:

[0006] (1) Mixing iron ore concentrate powder with molybdenum oxide powder, bentonite and slaked lime, and making balls to obtain green balls;

[0007] (2) Drying, preheating and roasting the green pellets to prepare oxidized pellets;

[0008] (3) The oxidized pellets are reduced using hydrogen-rich gas in a hydrogen-rich reduction shaft furnace to obtain molybdenum-containing DRI;

[0009] (4) Cooling the molybdenum-containing DRI under the protection of an inert gas;

[0010] (5) The cooled molybdenum-containing DRI is subjected to electric furnace smelting and melting to obtain molybdenum-iron alloy.

[0011] In the further step (1), the mass ratio of the iron ore concentrate to the molybdenum oxide powder, bentonite and slaked lime is 100:3-10:0.8-2:1.5-5.

[0012] In the further step (2), the calcination temperature is 1200-1280°C.

[0013] In the further step (3), the hydrogen-rich gas is coke oven gas.

[0014] In the further step (3), the reduction temperature is 950-1050°C.

[0015] In the further step (4), the tapping temperature of the electric furnace smelting is 1600-1650°C.

[0016] The beneficial effects of the above technical solution are as follows: the present invention adopts the hydrogen-based vertical furnace-electric furnace smelting method to produce molybdenum iron alloy, reducing process energy consumption and pollutant emissions; slaked lime is added during the pellet preparation process, reacting with molybdenum oxide powder in the pellet preheating-roasting stage to form a calcium molybdate stable compound, inhibiting the high-temperature volatilization of molybdenum oxide and improving the pelletizing performance of molybdenum-containing pellets. In particular, the use of low-cost coke oven gas as a reducing agent further realizes the clean production of molybdenum iron. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0018] Figure 1 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0019] Figure 1 As shown, the method for preparing molybdenum-iron alloy by hydrogen-based vertical furnace reduction and electric furnace smelting comprises the following steps: (1) mixing iron ore concentrate with molybdenum oxide powder, bentonite and slaked lime, and pelletizing in a disc pelletizing machine to obtain green balls. The mass ratio of the iron ore concentrate to molybdenum oxide powder, bentonite and slaked lime is 100:3-10:0.8-2:1.5-5; the iron ore concentrate with a particle size of 200 mesh and below accounts for 75% or more of the total amount, and the molybdenum oxide powder with a particle size of 200 mesh and below accounts for 75% or more of the total amount; the iron grade of the iron ore concentrate is 67% or more. The green ball particle size is 8-16 mm; the moisture content of the green ball is 8-10 wt%.

[0020] (2) Drying, preheating and roasting the green balls to prepare oxidized balls; the drying temperature is 350-450°C; the roasting temperature is 1200-1280°C, and the roasting time is 20-30 minutes.

[0021] (3) The oxidized pellets are reduced in a hydrogen-rich reduction shaft furnace using hydrogen-rich gas to obtain molybdenum-containing DRI (molybdenum-containing direct reduced iron); the hydrogen-rich gas is coke oven gas, and the coke oven gas (H 2 +CO+CH 4 )≥85vol%, volume ratio H 2 / CO≥4; during the reduction process, the consumption of coke oven gas is 450~550Nm 3 / tDRI. The reduction temperature of the reduction is 950-1050°C, and the reduction time is 1-2h.

[0022] (4) Cool the molybdenum-containing DRI under the protection of an inert gas to 50°C or below.

[0023] (5) The cooled molybdenum-containing DRI is subjected to electric furnace smelting and melting to obtain molybdenum-iron alloy. The tapping temperature of the electric furnace smelting is 1600-1650° C., and the power supply time is 25-35 minutes.

[0024] Example 1: The method for preparing ferromolybdenum alloy by combining hydrogen-based vertical furnace reduction and electric furnace smelting is specifically described as follows.

[0025] (1) Select iron ore concentrate with an iron grade of 70% and mix it with molybdenum oxide powder, bentonite and slaked lime in a mass ratio of 100:10:2:5. The iron ore concentrate and molybdenum oxide powder with a particle size of 200 mesh and below account for 78% and 80% of their total amount respectively. The moisture content of the mixed material is 10%. Then the mixed material enters the disc pelletizing machine for pelletizing. The raw ball size is controlled to be 8-16 mm.

[0026] (2) Drying and roasting the raw balls to prepare oxidized pellets; the drying temperature is 350°C, the roasting temperature is 1280°C, the roasting time is 30 min, and the average compressive strength of the pellets is 2450N.

[0027] (3) In a hydrogen-rich reduction shaft furnace, the pellets are subjected to a reduction reaction at 1050° C. using coke oven gas for 1 h to obtain molybdenum-containing DRI; wherein the coke oven gas (H 2 +CO+CH 4 )=86%, H 2 / CO=8, the consumption of coke oven gas is 450Nm 3 / tDRI.

[0028] (4) Cool the molybdenum-containing DRI to 45°C under inert gas protection.

[0029] (5) The cooled molybdenum-containing DRI is smelted in an electric furnace at a tapping temperature of 1600°C and a power supply time of 35 minutes to obtain a molybdenum-iron alloy.

[0030] In this embodiment, the comprehensive recovery rate of molybdenum and iron reaches 93%.

[0031] Example 2: The method for preparing ferromolybdenum alloy by combining hydrogen-based vertical furnace reduction and electric furnace smelting is specifically described as follows.

[0032] (1) Select iron ore concentrate with an iron grade of 69% and mix it with molybdenum oxide powder, bentonite and slaked lime in a mass ratio of 100:8:1.6:4. The iron ore concentrate and molybdenum oxide powder with a particle size of 200 mesh and below account for 78% and 80% of their total amount respectively. The moisture content of the mixed material is 9%. Then the mixed material enters the disc pelletizing machine for pelletizing. The raw ball size is controlled to be 8-16 mm.

[0033] (2) The raw balls are dried and roasted to prepare oxidized pellets; the drying temperature is 370°C, the roasting temperature is 1260°C, the roasting time is 28 min, and the average compressive strength of the pellets is 2378N.

[0034] (3) In a hydrogen-rich reduction shaft furnace, the pellets are subjected to a reduction reaction at 1020° C. using coke oven gas for 1.5 h to obtain molybdenum-containing DRI; wherein the coke oven gas (H 2 +CO+CH 4 )=85%, H 2 / CO=7.2, the consumption of coke oven gas is 500Nm 3 / tDRI.

[0035] (4) Cool the molybdenum-containing DRI to 45°C under inert gas protection.

[0036] (5) The cooled molybdenum-containing DRI is smelted in an electric furnace with a tapping temperature of 1620°C and a power supply time of 33 min to obtain a molybdenum-iron alloy.

[0037] In this embodiment, the comprehensive recovery rate of molybdenum and iron reaches 95%.

[0038] Example 3: The method for preparing ferro-molybdenum alloy by combining hydrogen-based vertical furnace reduction and electric furnace smelting is specifically described as follows.

[0039] (1) Select iron ore concentrate with an iron grade of 67% and mix it with molybdenum oxide powder, bentonite and slaked lime in a mass ratio of 100:6:1.2:3. The particle size of the iron ore concentrate and molybdenum oxide powder of 200 mesh and below accounts for 75% of their total amount respectively. The moisture content of the mixed material is 9%. Then the mixed material enters the disc pelletizing machine for pelletizing. The raw ball size is controlled to be 8-16 mm.

[0040] (2) Drying and roasting the raw balls to prepare oxidized pellets; the drying temperature is 400°C, the roasting temperature is 1250°C, the roasting time is 30 min, and the average compressive strength of the pellets is 2390N.

[0041] (3) using coke oven gas in a hydrogen-rich reduction shaft furnace to reduce the pellets at 1000°C for 1.5 hours to obtain molybdenum-containing DRI; wherein the coke oven gas (H 2 +CO+CH 4)=87%, H 2 / CO=6, the consumption of coke oven gas is 500Nm 3 / tDRI.

[0042] (4) Cool the molybdenum-containing DRI to 47°C under inert gas protection.

[0043] (5) The cooled molybdenum-containing DRI is smelted in an electric furnace with a tapping temperature of 1620°C and a power supply time of 31 min to obtain a molybdenum-iron alloy.

[0044] In this embodiment, the comprehensive recovery rate of molybdenum and iron reaches 96%.

[0045] Example 4: The method for preparing ferro-molybdenum alloy by combining hydrogen-based vertical furnace reduction and electric furnace smelting is specifically described as follows.

[0046] (1) Select iron ore concentrate with an iron grade of 67% and mix them in a mass ratio of iron ore concentrate: molybdenum oxide powder: bentonite: slaked lime = 100:5:1:2.5. The iron ore concentrate and molybdenum oxide powder with a particle size of 200 mesh and below account for 75% of their respective total amounts. The moisture content of the mixture is 9%. Then the mixture enters the disc pelletizing machine for pelletizing, and the raw ball size is controlled to be 8-16 mm.

[0047] (2) Drying and roasting the raw balls to prepare oxidized pellets; the drying temperature is 420°C, the roasting temperature is 1250°C, the roasting time is 25 min, and the average compressive strength of the pellets is 2515N.

[0048] (3) In a hydrogen-rich reduction shaft furnace, the pellets are subjected to a reduction reaction at 980°C using coke oven gas for 1.5 hours to obtain molybdenum-containing DRI; wherein the coke oven gas (H 2 +CO+CH 4 )=85%, H 2 / CO=5.8, the consumption of coke oven gas is 520Nm 3 / tDRI.

[0049] (4) Cool the molybdenum-containing DRI to 45°C under inert gas protection.

[0050] (5) The cooled molybdenum-containing DRI is smelted in an electric furnace with a tapping temperature of 1640°C and a power supply time of 28 min to obtain a molybdenum-iron alloy.

[0051] In this embodiment, the comprehensive recovery rate of molybdenum and iron reaches 94%.

[0052] Example 5: The method for preparing ferro-molybdenum alloy by combining hydrogen-based vertical furnace reduction and electric furnace smelting is specifically described as follows.

[0053] (1) Select iron ore concentrate with an iron grade of 67% and mix it with molybdenum oxide powder, bentonite and slaked lime in a mass ratio of 100:3:0.8:1.5. The particle size of the iron ore concentrate and molybdenum oxide powder of 200 mesh and below accounts for 75% of their total amount respectively. The moisture content of the mixed material is 8%. Then the mixed material enters the disc pelletizing machine for pelletizing. The raw ball size is controlled to be 8-16 mm.

[0054] (2) The green balls are dried and roasted to prepare oxidized pellets; the drying temperature is 450°C, the roasting temperature is 1200°C, the roasting time is 20 min, and the average compressive strength of the pellets is 2615N.

[0055] (3) In a hydrogen-rich reduction shaft furnace, the pellets are subjected to a reduction reaction at 950°C using coke oven gas for 2 hours to obtain molybdenum-containing DRI; wherein the coke oven gas (H 2 +CO+CH 4 )=88%, H 2 / CO=4, the consumption of coke oven gas is 550Nm 3 / tDRI.

[0056] (4) Cool the molybdenum-containing DRI to 50°C under inert gas protection.

[0057] (5) The cooled molybdenum-containing DRI is smelted in an electric furnace with a tapping temperature of 1650°C and a power supply time of 25 min to obtain a molybdenum-iron alloy.

[0058] In this embodiment, the comprehensive recovery rate of molybdenum and iron reaches 96%.

Claims

1. A method for preparing ferromolybdenum alloy by combining hydrogen-based shaft furnace reduction and electric furnace smelting, characterized in that: The method comprises the following steps: (1) mixing iron ore concentrate with molybdenum oxide powder, bentonite and slaked lime, and making balls to obtain green balls; the mass ratio of the iron ore concentrate to molybdenum oxide powder, bentonite and slaked lime is 100:3-10:0.8-2:1.5-5; the iron ore concentrate with a particle size of 200 mesh or less accounts for 75% or more of the total amount, and the molybdenum oxide powder with a particle size of 200 mesh or less accounts for 75% or more of the total amount; the iron grade of the iron ore concentrate is 67% or more; the green ball particle size is 8-16 mm; the moisture content of the green ball is 8-10 wt%; (2) Drying, preheating and roasting the green balls to prepare oxidized balls; the roasting temperature is 1200-1280°C and the roasting time is 20-30 minutes; (3) The oxidized pellets are reduced in a hydrogen-rich reduction shaft furnace using a hydrogen-rich gas to obtain molybdenum-containing DRI; the reduction temperature is 950-1050°C and the reduction time is 1-2 hours; the hydrogen-rich gas is coke oven gas; the coke oven gas contains (H2+CO+CH4) ≥85 vol%, and the volume ratio H2 / CO ≥4; (4) Cooling the molybdenum-containing DRI under the protection of an inert gas; (5) The cooled molybdenum-containing DRI is subjected to electric furnace smelting and melting to obtain molybdenum-iron alloy.

2. The method for preparing ferromolybdenum alloy by combining hydrogen-based shaft furnace reduction and electric furnace smelting according to claim 1, characterized in that: In the step (5), the tapping temperature of the electric furnace smelting is 1600-1650°C.

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