Method for reducing chromium content in chromium metal smelting slag

Abstract

The invention discloses a method for reducing chromium content in metal chromium smelting slag, and relates to a method for reducing chromium content in smelting slag, which comprises the following steps: uniformly mixing chrome green, aluminum powder, sodium chlorate, fluorite and a flux machine for 30 minutes, putting into a cast iron furnace shell, paving a bottom with magnesite bricks in the furnace shell, making a sand nest with fine magnesite, and after the mixture is put, projecting the middle of the top charge surface, and then making the top of the middle convex part into a nest shape, putting a thin or thin magnesium rod and sodium chlorate into the nest, igniting the thin or thin magnesium rod, carrying out ignition reaction, cooling for 24 hours after the reaction is finished, lifting a furnace shell, separating slag from chromium, sampling and analyzing slag components. The fluorite and the flux H are added, technological conditions are changed, the melting point of the system is reduced, the viscosity of the system is reduced, the reduction reaction time is prolonged, the metal chromium settling time is prolonged, finally, the chromium content of the smelting slag is reduced, and the utilization rate of chromium resources is increased.

Description

Technical Field

[0001] The invention relates to a method for reducing the chromium content in smelting slag, in particular to a method for reducing the chromium content in metal chromium smelting furnace slag. Background Art

[0002] Chromium smelting belongs to the metallurgical industry. The metallurgical industry refers to the process of extracting metals from ores or from oxides after enrichment through high-temperature treatment. The enrichment process is a hydrometallurgical process, and the high-temperature reduction process is a pyrometallurgical process, including the smelting, processing and manufacturing of metals. The smelting of chromium metal is the process of extracting chromium from enriched oxides through high-temperature reduction, which involves high temperatures and complex physical and chemical reactions.

[0003] The metallurgical industry includes two major categories: ferrous metallurgy and nonferrous metallurgy. Ferrous metallurgy mainly involves the smelting of ferrous metals such as iron, manganese, and chromium, while nonferrous metallurgy involves the smelting of nonferrous metals such as copper, aluminum, and zinc. Metallurgical methods include hydrometallurgy and pyrometallurgy. Hydrometallurgy refers to the process of treating ore or concentrate with solvents at normal temperature and pressure to dissolve the metal to be extracted in the solution while other impurities do not dissolve, and then extracting and separating the metal from the solution. Pyrometallurgy includes the following aspects: roasting, smelting, blowing, refining, distillation and rectification, molten salt electrolysis and other processes.

[0004] The scarcity of chromium resources in my country is mainly the result of the combined effects of factors such as insufficient natural endowment, uneven geographical distribution, high dependence on imports, high production costs and large market demand. my country's chromium ore resources are relatively scarce, and the proven recoverable reserves are extremely low. my country's proven recoverable reserves of chromium resources rank 12th in the world, accounting for less than 0.1% of the world. Chromium ores are mainly distributed in Tibet, Xinjiang, Inner Mongolia and Gansu, but the deposits in these areas are small in scale and poor in development conditions. Most of them need to be mined, which makes mining difficult and costly. Because these chromium ore resources are mainly concentrated in the southwest and northwest regions, transportation is inconvenient and transportation costs are high. In addition, the chromium ore production areas are numerous and scattered, and the scale of manufacturers is small, resulting in limited overall mining and supply capabilities. Most of my country's enterprises rely on imported ores, especially high-grade chromite. The world's major chromite resources are concentrated in South Africa, Kazakhstan, India, Brazil and Russia, especially South Africa, which ranks first in the world in terms of reserves. my country's import dependence has reached more than 90%, especially imports from South Africa. In addition, the ore in my country is difficult to extract and separate, and the associated species are complex, which further increases the production cost. With the acceleration of my country's industrialization and urbanization, the demand for chromium continues to increase, especially chromium as an important raw material for stainless steel production. The role of chromium is to enhance the hardness and corrosion resistance of stainless steel.

[0005] At present, the metal chromium smelting process generally adopts the following process: 1. Preparation of raw materials: chromium trioxide (Cr2O3 content 99.1%, particle size <3 mm), aluminum powder (AL content 99.2%, particle size <1 mm), and sodium chlorate (NaCLO3 content 99.5%, particle size <0.12 mm).

[0006] 2 Weigh the materials according to the ratio of 100% chromium oxide: 35.6% aluminum powder: 8.5% sodium chlorate, and use a mixer to mix the materials weighed according to the ratio for 40 minutes until they are evenly mixed.

[0007] 3 Smelting, put the evenly mixed materials into the cast iron furnace shell, ignite them with magnesium chips, and then smelt them.

[0008] 4 24 hours after smelting is completed, remove the furnace shell, and 48 hours later, separate the slag and iron.

[0009] 5. Sandblasting: Use a sandblasting machine to blast the oxide scale of the chrome ingot into the natural silver-white color of the metal with steel balls.

[0010] 6. Packaging: After crushing and weighing, pack in stainless steel barrels (galvanized barrels).

[0011] When the reaction system is at a high temperature of more than 2200°C, the metallic chromium and the slag are separated under molten liquid conditions. The temperature of the system and the viscosity of the slag are the key factors affecting the separation results of the metallic chromium and the slag. Due to the high melting point of the system and the high viscosity of the slag, the slag solidifies quickly and the molten liquid time is short, resulting in incomplete separation of the metallic chromium and the slag, and the remaining metallic chromium content in the slag reaches 4%. Due to the rapid solidification of the slag and the short reaction time, the reaction of chromium trioxide and aluminum powder is incomplete, so that the chromium trioxide content in the slag (including the metallic chromium converted part) reaches more than 15%. Therefore, it is of great significance to reduce the chromium content in metallic chromium smelting slag and improve the utilization rate of chromium resources.

[0012] The main chemical reaction of the existing aluminothermic method for smelting metallic chromium is to use aluminum powder to reduce the trivalent chromium in chromium trioxide to zero-valent chromium: Cr2O3+2AI→2Cr+ AI2O3 Then, under the high temperature molten liquid conditions of metallic chromium and slag, natural sedimentation separation is completed by the specific gravity difference between metallic chromium and slag. The specific gravity of metallic chromium is 7.15 g / cm 3 , and the specific gravity of slag is 3.6 g / cm 3 ; Due to the high melting point of the system and the high viscosity of the slag, the slag solidifies quickly and remains in the molten liquid state for a short time, resulting in incomplete separation of metallic chromium and slag. Moreover, due to the rapid solidification of the slag, the overall reaction time is short and the reaction is not fully carried out. Summary of the invention

[0013] The object of the present invention is to provide a method for reducing the chromium content in metal chromium smelting slag. The present invention adds fluorite and flux H, changes the process conditions to reduce the melting point of the system, reduces the viscosity of the system, increases the reduction reaction time, and increases the sedimentation time of metal chromium, ultimately achieving the purpose of reducing the chromium content in the smelting slag and improving the utilization rate of chromium resources.

[0014] The objective of the present invention is achieved through the following technical solutions: A method for reducing the chromium content in chromium smelting slag, the method comprising the following steps: 100 kg of metallurgical chrome green (Cr2O3 content 99.1%), 35.6 kg of aluminum powder (AL content 99.2%), 8.5 kg of sodium chlorate (NaCLO3 content 99.5%), 8 kg of fluorite (CaF2 content 98%), and 5 kg of flux H; The specific process is as follows: mix the above-mentioned chrome green, aluminum powder, sodium chlorate, fluorite and flux machine for 30 minutes to mix the materials evenly, and put them into the cast iron furnace shell. The bottom of the furnace shell is paved with magnesium bricks, and fine magnesium sand is used to make sand nests. After the mixture is put in, the middle of the top material surface is convex, and then the top of the convex part in the middle is made into a nest shape, and thin or thin magnesium strips and sodium chlorate are put into the nest, and the thin or thin magnesium strips are ignited to ignite the reaction. After the reaction is completed, cool for 24 hours, remove the furnace shell, and then separate the slag and chromium, and take samples to analyze the slag composition.

[0015] The method for reducing the chromium content in the slag of metal chromium smelting furnace, the slag components are sampled and analyzed after the slag chromium is separated and correspond to the following: Cr2O3: Cr 0+ AL2O3 AL Fe Na2O 10 2 86 0.24 0.15 0.5 The method for reducing the chromium content in the slag of metal chromium smelting is as follows: when the metal chromium is smelted by the aluminothermic method, 0 to 12% of fluorite and 0 to 8% of flux H are added to 100 kg of chrome green.

[0016] The advantages and positive effects of the present invention are: 1 The present invention adds fluorite and flux H so that the flux can react with gangue oxides and harmful impurity oxides in the ore during the metallurgical process to form a low melting point slag layer, thereby effectively separating the metal to be extracted from the smelting slag. In the process of smelting metal chromium, the added flux also plays this role. From the surface of the slag and chromium separation, the tiny particles of chromium entrained in the slag are significantly reduced, and the surface of the slag and chromium separation is smoother than that without adding fluorite and flux H, reducing the pores on the chromium surface.

[0017] 2 The present invention controls the melting temperature of slag: by adding flux, the melting temperature of slag can be reduced, so that it melts at a lower temperature, thereby controlling the melting temperature of slag. In the process of chromium metal smelting, after adding flux fluorite and flux H, the temperature of the reaction system is reduced by 200°C to 300°C, which accelerates the reaction process.

[0018] 3. The present invention controls the viscosity and density of slag: The flux can control the viscosity and density of slag, effectively separate it from the metal, reduce the loss of metal in the slag, and improve the recovery rate of metal. After adding the flux fluorite and flux H, the viscosity of the slag becomes thinner.

[0019] 4. The present invention removes impurities: The flux can remove impurities such as sulfur and phosphorus, and improve the quality of the metal. Sulfur, phosphorus, etc. enter the slag in the form of calcium salts, which is beneficial to improve the quality of metallic chromium.

[0020] 5 The present invention enhances the fluidity of the slag: by adjusting the basicity of the charge, the flux and the alumina in the slag form a low melting point composite salt, which enhances the fluidity of the slag and facilitates the operation of the smelting process and the separation of the metal. After adding the flux fluorite and flux H, the fluidity of the metal chromium smelting slag is significantly enhanced.

[0021] 6. As the temperature of the reaction system decreases, the solidification time of the slag increases, which means that the reaction time and the settling time of the metal increase. Two fluxes, fluorite and H flux, are added. The use mechanism of H flux is similar to that of fluorite. H flux enhances the use effect of the overall flux and makes the flux effect better. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a process flow chart for reducing the chromium content in metallic chromium smelting slag. DETAILED DESCRIPTION

[0023] The present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.

[0024] The composition of the smelting slag in the process of the present invention is (%): Cr2O3: Cr 0+ AL2O3 AL Fe Na2O 8-12 1-4 82-90 0.25 0.15 0.5 Example 1

[0025] The smelting ratio is: 100 kg of metallurgical chrome green (Cr2O3 content 99.1%, particle size <3 mm), 35.6 kg of aluminum powder (AL content 99.2%, particle size <1 mm), 8.5 kg of sodium chlorate (NaCLO3 content 99.5%, particle size <0.12 mm), 8 kg of fluorite (CaF2 content 98%, particle size <0.18 mm), and 5 kg of flux H. The composition of the smelting slag is (%): Cr2O3: Cr 0+ AL2O3 AL Fe Na2O 10 2 86 0.24 0.15 0.5 The specific process is: 200 kg of chrome green, 71.2 kg of aluminum powder, 17 kg of sodium chlorate, 16 kg of fluorite, and 10 kg of flux are mixed in a flux machine for 30 minutes, and the materials are mixed and placed in the cast iron furnace shell. The furnace shell is paved with magnesium bricks, and a sand nest is made with fine magnesium sand. After the mixed materials are loaded, the middle of the top material surface is convex, and then the top of the convex part in the middle is made into a nest shape, and a thin (thin) magnesium strip and a small amount of sodium chlorate are put into the nest, and the thin (thin) magnesium strip is ignited to ignite the reaction. After the reaction is completed, it is cooled for 24 hours, and the furnace shell is removed, and then the slag chromium is separated, and the slag composition is analyzed by sampling. Example 2

[0026] The smelting ratio is: 100 kg of metallurgical chrome green (Cr2O3 content 99.1%), 35.6 kg of aluminum powder (AL content 99.2%), 8.5 kg of sodium chlorate (NaCLO3 content 99.5%), 6 kg of fluorite (CaF2 content 98%), and 4 kg of flux H. The composition of the smelting slag is (%): Cr2O3: Cr 0+ AL2O3 AL Fe Na2O 12 2.4 84 0.28 0.15 0.5 The specific process is: 200 kg of chrome green, 71.2 kg of aluminum powder, 17 kg of sodium chlorate, 12 kg of fluorite, and 8 kg of flux H are mixed in a mixer for 30 minutes, and the materials are mixed evenly and placed in the cast iron furnace shell. The furnace shell is paved with magnesium bricks, and a sand nest is made with fine magnesium sand. After the mixture is loaded, the middle of the top material surface is convex, and then the top of the convex part in the middle is made into a nest shape, and a thin (thin) magnesium strip and a small amount of sodium chlorate are placed in the nest, and the thin (thin) magnesium strip is ignited to ignite the reaction. After the reaction is completed, it is cooled for 24 hours, and the furnace shell is removed, and then the slag chromium is separated, and the slag composition is analyzed by sampling. Example 3

[0027] The smelting ratio is: 100 kg of metallurgical chrome green (Cr2O3 content 99.1%), 35.6 kg of aluminum powder (AL content 99.2%), 8.5 kg of sodium chlorate (NaCLO3 content 99.5%), 10 kg of fluorite (CaF2 content 98%), and 6 kg of flux H. The composition of the smelting slag is (%): Cr2O3: Cr 0+ AL2O3 AL Fe Na2O 11 2.2 85 0.26 0.15 0.5 The specific process is: 200 kg of chrome green, 71.2 kg of aluminum powder, 17 kg of sodium chlorate, 20 kg of fluorite, and 12 kg of flux H are mixed in a mixer for 30 minutes, and the materials are mixed evenly and placed in the cast iron furnace shell. The furnace shell is paved with magnesium bricks and a sand nest is made with fine magnesium sand. After the mixture is loaded, the middle of the top material surface is convex, and then the top of the convex part in the middle is made into a nest shape, and a thin (thin) magnesium strip and a small amount of sodium chlorate are placed in the nest, and the thin (thin) magnesium strip is ignited to ignite the reaction. After the reaction is completed, it is cooled for 24 hours, and the furnace shell is removed, and then the slag chromium is separated, and the slag composition is sampled and analyzed. Example 4

[0028] The further optimized ratio is: 100 kg of metallurgical chrome green (Cr2O3 content 99.1%), 35.6 kg of aluminum powder (AL content 99.2%), 8.5 kg of sodium chlorate (NaCLO3 content 99.5%), 8 kg of fluorite (CaF2 content 98%), and 5 kg of flux H. The composition of the smelting slag is (%): Cr2O3: Cr 0+ AL2O3 AL Fe Na2O 10 2 86 0.24 0.15 0.5 When the aluminothermic method is used to smelt metallic chromium, 0 to 12% fluorite and 0 to 8% flux H are added to 100 kg of chrome green; the smelting process is the same as that in Example 1.

Claims

1. A method for reducing the chromium content in chromium smelting slag, characterized in that: The method comprises the following steps: 100 kg of metallurgical chrome green (Cr2O3 content 99.1%), 35.6 kg of aluminum powder (AL content 99.2%), 8.5 kg of sodium chlorate (NaCLO3 content 99.5%), 8 kg of fluorite (CaF2 content 98%), and 5 kg of flux H; The specific process is as follows: mix the above-mentioned chrome green, aluminum powder, sodium chlorate, fluorite and flux machine for 30 minutes to mix the materials evenly, and put them into the cast iron furnace shell. The bottom of the furnace shell is paved with magnesium bricks, and fine magnesium sand is used to make sand nests. After the mixture is put in, the middle of the top material surface is convex, and then the top of the convex part in the middle is made into a nest shape, and thin or thin magnesium strips and sodium chlorate are put into the nest, and the thin or thin magnesium strips are ignited to ignite the reaction. After the reaction is completed, cool for 24 hours, remove the furnace shell, and then separate the slag and chromium, and take samples to analyze the slag composition.

2. A method for reducing the chromium content in chromium smelting slag according to claim 1, characterized in that: After the slag chromium is separated, the slag components are sampled and analyzed as follows: <h2 style=";text-align:left;direction:ltr">Cr2O3: Cr<h2 style=";text-align:left;direction:ltr"> 0+ <h2 style=";text-align:left;direction:ltr"> AL2O3 ALFeNa2O 10 2 86 0.24 0.15 0.5。 3. The method for reducing the chromium content in chromium smelting slag according to claim 1, characterized in that: When the aluminothermic method is used to smelt metallic chromium, 0 to 12% of fluorite and 0 to 8% of flux H are added to 100 kg of chrome green.

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