Method for melting and smelting ferrochrome through total-oxygen hydrogen-rich low-carbon furnace

Abstract

The invention discloses a method for melting and smelting ferrochrome in an all-oxygen hydrogen-rich low-carbon furnace, which comprises the following steps: (1) proportioning and uniformly mixing chromite pellets, coke and lime according to the mass ratio of 1: (0.15-0.2): (0.08-0.15), and filling the mixture into the all-oxygen hydrogen-rich low-carbon furnace; (2) high-temperature hydrogen-rich gas at the temperature of 900-1100 DEG C is introduced into the middle of the furnace body, and selective reduction of ferrochrome oxide is achieved; blowing industrial pure oxygen at the lower part of the furnace body, combusting with coke to generate CO, and driving a secondary reduction reaction; (3) maintaining a high-temperature environment in the furnace through oxygen-fuel combustion to completely melt the materials into molten iron, and carrying out central stirring on the molten iron to form a vortex with the height-diameter ratio of 0.5-1.5; and (4) discharging the molten iron after the reaction is completed. According to the method, the reduction rate of chromium in the chromite exceeds 92%, the carbon emission is reduced by 40% or above compared with a traditional blast furnace and submerged arc furnace process, meanwhile, the method has the advantages of being high in smelting efficiency, low in energy consumption, stable in product quality and the like, and a low-carbon and efficient innovative path is provided for ferrochrome smelting.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hydrogen metallurgy, and in particular to a method for smelting ferrochrome alloy in a full-oxygen hydrogen-rich low-carbon furnace. BACKGROUND

[0002] Ferrochrome alloy is an indispensable basic raw material for the steel industry, which can greatly improve the strength, hardness and corrosion resistance of steel, and plays an important strategic role in modern manufacturing. At present, the main smelting technologies for ferrochrome alloy are the ore smelting furnace method, the electric furnace method and the blast furnace method, which have formed a mature and stable industrial production mode through long-term technical iteration and practical accumulation.

[0003] However, the drawbacks of traditional smelting technology are highlighted in the industrialization process. In terms of energy and environment, this technology has significant defects such as high energy consumption and high carbon emissions, which is in sharp contradiction with the global green and low-carbon development concept. In terms of process technology, the traditional process system with coke as the core reducing agent exposes problems such as low production efficiency and insufficient reduction reaction, resulting in a large amount of chromium iron oxide remaining in the smelting tailings, causing serious waste of chromium resources and exacerbating environmental pollution. These drawbacks further lead to an extension of the smelting cycle and an increase in production costs, which seriously restricts the sustainable development of the ferrochrome alloy industry.

[0004] Under the background of accelerating the development of green and low-carbon technologies worldwide and the continuous growth of demand for high-quality ferrochrome alloy in various fields, it is urgent to break through the bottlenecks of traditional smelting technology. Through innovative furnace design and process optimization, the reduction limit of existing technology is overcome, and the production of ferrochrome alloy is realized with low carbon, low energy consumption and high efficiency, which has become a key direction for technological innovation in the industry. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a low-carbon and efficient method for smelting ferrochrome alloy in a full-oxygen hydrogen-rich low-carbon furnace.

[0006] To solve the above technical problems, the technical solution adopted by the present application includes the following steps: (1) mixing and uniformly mixing chromite pellets, coke and lime according to a mass ratio of 1:(0.15-0.2):(0.08-0.15) and loading into a full-oxygen hydrogen-rich low-carbon furnace; (2) passing high-temperature hydrogen-rich gas at 900-1100℃ into the middle part of the furnace body to realize selective reduction of chromium iron oxides; and blowing industrial pure oxygen into the lower part of the furnace body to generate CO by combustion with coke, thereby driving the secondary reduction reaction; (3) maintaining a high-temperature environment in the furnace by full-oxygen combustion to completely melt the material into molten iron, and center stirring the molten iron to form a vortex with a height-diameter ratio of 0.5-1.5; (4) discharging the molten iron after the reaction is completed.

[0007] Further, the full-oxygen hydrogen-rich low-carbon furnace is provided with a stirring paddle, and the paddle blade of the stirring paddle is located at 1 / 4-1 / 2 of the liquid level height of molten iron.

[0008] Further, in the step (1), the chromite pellet particle size is 6-12 mm, the compression strength is greater than or equal to 2000 N / sphere, and the reduction expansion rate is less than or equal to 15%.

[0009] Further, in the step (2), the H2 content of the high-temperature hydrogen-rich gas is greater than or equal to 60 wt%, and the flow rate is controlled to be 200-400 Nm 3 / t; the flow rate of the industrial pure oxygen is controlled to be 100-200 Nm 3 / t.

[0010] Further, in the step (3), the temperature of the molten iron is controlled to be 1450-1550 DEG C.

[0011] The beneficial effects generated by the above technical scheme are that: the present application adopts a unique layered synergistic smelting mechanism: the chromite pellets, coke and lime are uniformly mixed according to the proportion and then are distributed into the full-oxygen hydrogen-rich low-carbon furnace; the high-temperature hydrogen-rich gas is introduced into the middle part of the furnace body, and the strong reducing property of hydrogen is used to realize efficient reduction of the materials; the lower part of the furnace body further promotes the deep reduction of the materials and completes the melting separation by means of the full-oxygen combustion environment. In the smelting process, the stirring system applies mechanical force to the molten pool area, promotes the circulation flow of the materials, and significantly strengthens the mass and heat transfer efficiency in the molten pool. Finally, the molten iron and slag are smoothly discharged from the slag-iron port. The present application makes the reduction rate of chromium in chromite exceed 92%, and the carbon emission is reduced by more than 40% compared with the traditional blast furnace and electric furnace process, and at the same time has the advantages of high smelting efficiency, low energy consumption, stable product quality and the like, thereby providing a low-carbon and efficient innovative path for the smelting of ferrochrome alloy.

[0012] The present application adopts a synergistic reaction system of "upper hydrogen-rich selective reduction + lower full-oxygen high-temperature melting", combines with the mechanical strengthening technology of the stirring paddle, forms a new mode of low-carbon and efficient chromium-containing mineral smelting, and has the following characteristics: (1) The quality of the chromite pellet is strictly controlled, and the accurate process parameter control is matched to ensure the stability of the smelting process and the excellent performance of the produced ferrochrome alloy; (2) The hydrogen-rich gas is used as the main reducing agent to replace the use of a large amount of coke in the traditional way, and the full-oxygen combustion technology is combined to effectively reduce the carbon emission in the smelting process, thereby meeting the green and low-carbon development demand; (3) The structure design of the full-oxygen hydrogen-rich low-carbon furnace is scientific, temperature and pressure sensors are installed at the coal gas outlet, and the reaction progress in the furnace can be monitored and controlled in real time; (4) The mechanical stirring forms a specific high-diameter ratio vortex to promote the reaction to proceed fully, shorten the smelting cycle and improve the production efficiency; (5) The chromium recovery rate of the method is greater than or equal to 92%, and the comprehensive utilization rate of chromium resources is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0014] Figure 1 It is a structural schematic diagram of the all-oxygen hydrogen-rich low-carbon furnace of the present invention.

[0015] In the figure: 1-furnace body, 2-indirect reduction zone, 3-soft melt dripping zone, 4-coke combustion and slag iron zone, 5-stirring paddle, 6-gas outlet, 7-hydrogen-rich reducing gas inlet, 8-oxygen air inlet, 9-slag iron outlet. DETAILED DESCRIPTION

[0016] Figure 1 As shown, the structure of the all-oxygen hydrogen-rich low-carbon furnace used in the method for melting and smelting ferrochrome alloy in this all-oxygen hydrogen-rich low-carbon furnace is as follows: it comprises a furnace body 1; the inner cavity of the furnace body 1 is sequentially divided into an indirect reduction zone 2, a soft melt dripping zone 3, and a coke combustion and slag iron zone 4 from top to bottom, and is also provided with a stirring paddle 5; the blades of the stirring paddle 5 are located in the coke combustion and slag iron zone 4, preferably at 1 / 4 to 1 / 2 of the height of the molten iron liquid level during melting and smelting; the stirring paddle is preferably a zirconia stirring paddle with a high temperature resistance of ≥2200°C. The furnace body 1 is also provided with a gas outlet 6, a hydrogen-rich reducing gas air inlet 7, an oxygen air inlet 8, and a slag iron outlet 9; the gas outlet 6 is located at the top of the furnace body 1, the hydrogen-rich reducing gas air inlet 7 is located in the middle of the furnace body 1 and connected to the indirect reduction zone 2, the oxygen air inlet 8 is located in the bottom of the furnace body 1 and connected to the coke combustion and slag iron zone 4, and the slag iron outlet 9 is located at the side bottom of the furnace body 1. A temperature sensor and a pressure sensor are installed at the gas outlet 6 to monitor the gas temperature and pressure in real time. The monitoring data are used to regulate the reduction reaction process in the furnace.

[0017] Figure 1 As shown, the method for melting and smelting ferrochrome alloy in a full oxygen hydrogen-rich low carbon furnace comprises the following steps: (1) chromite pellets, coke and lime are mixed in a mass ratio of 1: (0.15-0.2): (0.08-0.15) and loaded into the full oxygen hydrogen-rich low carbon furnace.

[0018] The chromite pellets are prepared from chromite green balls by drying, preheating and roasting, preferably using a chain grate-rotary kiln system; in the drying stage, the drying temperature is 250-300 DEG C, and the drying time is 10-15 min, to remove the internal moisture of the green balls; in the preheating stage, the preheating temperature is 900-950 DEG C, and the preheating time is 15-25 min, to preliminarily densify the structure of the green balls; in the roasting stage, the roasting temperature is 1200-1250 DEG C, and the roasting time is 30-35 min, to complete the transformation from the green balls to the chromite pellets. The obtained chromite pellets have uniform chemical composition, good mechanical strength and reduction performance, and the particle size is 6-12 mm, the compressive strength is greater than or equal to 2000 N / pellet, and the reduction expansion rate is less than or equal to 15%.

[0019] (2) The high-temperature hydrogen-rich gas at 900-1100 DEG C is introduced into the middle part of the furnace body through the hydrogen-rich reduction gas inlet 7, and in this area, the hydrogen-rich gas is reduced with the chromite oxide to gradually reduce the high-valence chromite oxide into low-valence state, realizing the selective reduction of the chromite oxide; the industrial pure oxygen is injected into the lower part of the furnace body through the oxygen inlet 8, and is combusted with the coke to generate CO; the generated CO fully contacts with the furnace charge in the upward movement process, driving the secondary reduction reaction; in this process, the CO as a strong reducing agent further reduces the chromite oxide, strengthens the overall reduction effect, and significantly improves the reduction efficiency of the chromium element. The H2 content in the high-temperature hydrogen-rich gas is greater than or equal to 60 wt%, and the flow rate is controlled at 200-400 Nm 3 / t; the O2 content in the industrial pure oxygen is greater than or equal to 99 wt%, and the flow rate is controlled at 100-200 Nm3 / t.

[0020] (3) In the above reduction reaction process, the oxygen is input through the oxygen inlet 8 to maintain the high-temperature environment in the furnace by full-oxygen combustion, so that the material is completely melted into molten iron, and the temperature of the molten iron is controlled at 1450-1550 DEG C; the paddle located at 1 / 4-1 / 2 of the liquid level height of the molten iron during smelting is used to centrally stir the molten iron, the stirring speed is controlled at 50-100 r / min, and a vortex with a height / diameter ratio = height / diameter = 0.5-1.5 is formed; the vortex drives the metal liquid to continuously flow, on the one hand, it can uniformly the temperature and composition of the molten iron, avoiding local overheating or composition segregation; on the other hand, it greatly accelerates the chemical reaction speed in the furnace, making the reaction more sufficient and efficient. After the reaction is completely finished, the stirring paddle control system is closed in time to stop the stirring operation.

[0021] (4) The molten product after the reaction is left for a period of time, and the natural layering is realized by using the difference in density between the molten iron and the molten slag; then, the molten iron and the molten slag are discharged in layers from the slag-iron outlet 9, and the mixture flowing out is precisely separated by the skimmer, effectively isolating the molten slag, to obtain pure molten iron. After the above reduction reaction, the reduction rate of chromium in the chromite is greater than or equal to 92%.

[0022] Example 1: The method for smelting ferrochrome alloy in the full-oxygen hydrogen-rich low-carbon furnace is as follows.

[0023] (1) The high-quality chromite raw balls with a Cr2O3 content of 43.03% are put into the chain grate-rotary kiln system for drying, preheating and roasting treatment. In the drying stage, the drying temperature is 250°C, the drying time is 12 min, and the internal moisture of the raw balls is removed; in the preheating stage, the preheating temperature is 900°C, the preheating time is 15 min, and the structure of the raw balls is preliminarily densified; in the roasting stage, the roasting temperature is 1200°C, the roasting time is 32 min, and the transformation from the raw balls to the chromite pellets is completed. The chromite pellets prepared by this process have uniform chemical composition, good mechanical strength and reduction performance, the particle size is in the range of 8-12 mm, the average compressive strength is 2158 N / ball, and the reduction expansion rate is 8.5%. The chromite pellets, coke and lime are mixed and uniformly mixed according to a mass ratio of 1:0.15:0.08, and are loaded into the full-oxygen hydrogen-rich low-carbon furnace in batches, and the material surface is always kept below the furnace opening plane to ensure safe and standardized operation and good permeability in the furnace.

[0024] (2) The hydrogen-rich gas is heated to 900°C by the heating furnace, and is injected into the furnace at a flow rate of 200 Nm 3 / t from the hydrogen-rich reducing gas inlet, entering the indirect reduction zone. The H2 content in the hydrogen-rich gas is 62.8wt%, and the CH4 content is 16.4%, and the CH4 can undergo self-reforming reaction under a specific atmosphere in the furnace to convert into CO and H2, so that the effective utilization rate of the hydrogen-rich gas reaches 45.2%. At the same time, 100 Nm 3 / t of industrial pure oxygen with a purity of 99.0% is injected from the oxygen inlet, and the oxygen is combusted with the coke in the furnace to rapidly generate CO to drive the secondary reduction reaction.

[0025] (3) The full-oxygen combustion provides a continuous and stable high-temperature environment to completely melt the reduced material into molten iron, and the temperature of the molten iron is maintained at about 1450°C. The zirconia stirring paddle is selected and inserted to 1 / 3 of the height of the molten iron liquid surface, and the center stirring is performed at a stirring speed of 50 r / min. Under the action of the stirring paddle, the molten iron forms a vortex with a height-diameter ratio of 0.5. After the reaction is completed, the stirring paddle control system is turned off in time to stop the stirring operation.

[0026] (4) After the reaction is completed, the molten iron and the slag are discharged by layering, and the final obtained ferrochrome alloy has a chromium content of 53.7% and a chromium element recovery rate of 92.1%.

[0027] Example 2: The method for smelting ferrochrome alloy in the full-oxygen hydrogen-rich low-carbon furnace is as follows.

[0028] (1) The high-quality chromite green balls with Cr2O3 content of 43.03% are put into the chain grate-rotary kiln system for drying, preheating and roasting treatment. In the drying stage, the drying temperature is 275°C, and the drying time is 10 min to remove the internal moisture of the green balls. In the preheating stage, the preheating temperature is 925°C, and the preheating time is 20 min to preliminarily densify the structure of the green balls. In the roasting stage, the roasting temperature is 1225°C, and the roasting time is 30 min to complete the conversion from the green balls to the chromite pellets. The chromite pellets prepared by this process have uniform chemical composition, good mechanical strength and reduction performance, and the particle size is in the range of 9-12 mm, the average compressive strength is 2198 N / pellet, and the reduction expansion rate is 7.8%. The chromite pellets, coke and lime are mixed and uniformly mixed in a mass ratio of 1:0.18:0.12, and are loaded into the full-oxygen hydrogen-rich low-carbon furnace in batches, and the material surface is always kept below the furnace opening plane to ensure safe and standardized operation and good permeability in the furnace.

[0029] (2) The hydrogen-rich gas is heated to 950°C by the heating furnace, and is injected into the furnace at a flow rate of 300 Nm 3 / t from the hydrogen-rich reducing gas inlet to enter the indirect reduction zone. The H2 content in the hydrogen-rich gas is 64.1wt%, and the CH4 content is 16.9%. CH4 can undergo self-reforming reaction under a specific atmosphere in the furnace to convert into CO and H2, so that the effective utilization rate of the hydrogen-rich gas reaches 46.7%. At the same time, 150 Nm 3 / t of industrial pure oxygen with a purity of 99.0% is injected from the oxygen inlet, and the oxygen is combusted with the coke in the furnace to rapidly generate CO to drive the secondary reduction reaction.

[0030] (3) The full-oxygen combustion provides a continuous and stable high-temperature environment to completely melt the reduced material into molten iron, and the temperature of the molten iron is maintained at about 1500°C. Zirconia stirring paddles are selected, the paddle blades are inserted to 1 / 4 of the height of the molten iron liquid surface, and the center stirring is carried out at a stirring speed of 75 r / min. Under the action of the stirring paddles, the molten iron forms a vortex with a height-diameter ratio of 1.0.

[0031] (4) After the reaction is completed, the molten iron and molten slag are discharged by layering, and the final obtained chromium-iron alloy has a chromium content of 54.2% and a chromium element recovery rate of 92.8%.

[0032] Example 3: The method for smelting chromium-iron alloy by the full-oxygen hydrogen-rich low-carbon furnace is specifically as follows.

[0033] (1) The high-quality chromite green balls with Cr2O3 content of 43.03% are put into the chain grate-rotary kiln system for drying, preheating and roasting treatment. In the drying stage, the drying temperature is 300°C, the drying time is 15 min, and the internal moisture of the green balls is removed; in the preheating stage, the preheating temperature is 950°C, the preheating time is 25 min, and the structure of the green balls is preliminarily densified; in the roasting stage, the roasting temperature is 1250°C, the roasting time is 35 min, and the transformation from green balls to chromite pellets is completed. The chromite pellets prepared by this process have uniform chemical composition, good mechanical strength and reduction performance, the particle size is in the range of 6-10 mm, the average compressive strength is 2258 N / ball, and the reduction expansion rate is 7.2%. The chromite pellets, coke and lime are mixed and uniformly mixed according to the mass ratio of 1:0.20:0.15, and are loaded into the full-oxygen hydrogen-rich low-carbon furnace in batches, and the material surface is always kept below the furnace opening plane to ensure safe and standardized operation and good permeability in the furnace.

[0034] (2) The hydrogen-rich gas is heated to 1100°C by the heating furnace, and is injected into the furnace at a flow rate of 400 Nm 3 / t from the hydrogen-rich reducing gas inlet, entering the indirect reduction zone. The H2 content in the hydrogen-rich gas is 64.7wt%, and the CH4 content is 17.2%, and CH4 can undergo self-reforming reaction under a specific atmosphere in the furnace to convert into CO and H2, so that the effective utilization rate of hydrogen-rich gas reaches 46.8%. At the same time, 200 Nm 3 / t of industrial pure oxygen with a purity of 99.0% is injected at the oxygen inlet, and the oxygen and coke in the furnace are combusted rapidly to generate CO, driving the secondary reduction reaction.

[0035] (3) The full-oxygen combustion provides a continuous and stable high-temperature environment, which promotes the complete melting of the reduced material into molten iron, and keeps the temperature of the molten iron at about 1525°C. Zirconia stirring paddles are selected and inserted to 1 / 2 of the height of the molten iron liquid surface, and the center stirring is carried out at a stirring speed of 100 r / min. Under the action of the stirring paddles, the molten iron forms a vortex with a height-diameter ratio of 1.5.

[0036] (4) After the reaction is completed, the molten iron and slag are discharged by layering. The final obtained chromium-iron alloy has a chromium content of 54.9%, and the recovery rate of chromium element reaches 93.3%.

Claims

1. A method for melting and smelting ferrochrome alloy in a full oxygen, hydrogen-rich, low-carbon furnace, characterized in that: The method comprises the following steps: (1) mixing chromite pellets, coke and lime in a mass ratio of 1:(0.15-0.2):(0.08-0.15), and loading the mixture into a full oxygen, hydrogen-rich and low-carbon furnace; (2) A high-temperature hydrogen-rich gas at 900-1100°C is introduced into the middle of the furnace to achieve the selective reduction of chromium iron oxides; industrial pure oxygen is injected into the lower part of the furnace to burn with coke to generate CO, driving the secondary reduction reaction; (3) Maintaining a high temperature environment in the furnace through full oxygen combustion allows the material to be completely melted into molten iron, and the molten iron is centrally stirred to form a vortex with a height-to-diameter ratio of 0.5 to 1.5; (4) After the reaction is completed, the molten iron can be discharged.

2. The method for melting and smelting ferrochrome alloy in a full oxygen, hydrogen-rich, low carbon furnace according to claim 1, characterized in that: The all-oxygen, hydrogen-rich, low-carbon furnace is provided with a stirring paddle, and the blades of the stirring paddle are located at 1 / 4 to 1 / 2 of the height of the molten iron liquid level.

3. The method for melting and smelting ferrochrome alloy in a full oxygen, hydrogen-rich, low carbon furnace according to claim 1, characterized in that: In the step (1), the chromite pellets have a particle size of 6 to 12 mm, a compressive strength of ≥ 2000 N / ball, and a reduction expansion rate of ≤ 15%.

4. The method for melting and smelting ferrochrome alloy in a full oxygen, hydrogen-rich, low carbon furnace according to claim 1, characterized in that: In step (2), the H2 content of the high-temperature hydrogen-rich gas is ≥60wt%, and the flow rate is controlled at 200-400Nm 3 / t; the industrial pure oxygen flow rate is controlled at 100~200Nm 3 / t.

5. The method for melting and smelting ferrochrome alloy in an all-oxygen, hydrogen-rich, low-carbon furnace according to any one of claims 1 to 4, characterized in that: In the step (3), the temperature of the molten iron is controlled at 1450-1550°C.

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