Process method for producing iron alloy by reducing dilution slag of silver furnace

Abstract

The invention relates to the technical field of metallurgy, in particular to a process method for producing iron alloy through reduction of silver furnace dilution slag, which comprises the following steps of: 1, pretreating raw materials, namely crushing and levigating the silver furnace dilution slag, and crushing and screening a reducing agent; 2, mixing the pretreated raw materials, adding an additive, uniformly mixing, and adding the uniformly mixed mixture into a reduction furnace for reduction smelting; the tailings subjected to beneficiation dilution are selected, the dilution slag in the molten state is directly subjected to electric furnace reduction and is subjected to reduction smelting in the electric furnace, coke powder is adopted as a reducing agent, the dilution slag is added, the reduction rate of iron reaches 97% or above, the reduction rate of copper reaches 95% or above, and the iron content of the obtained alloy is 86% or above; the iron alloy can be sold as pig iron, and the depleted electric furnace slag contains more than 50% of silicon dioxide and can be used as a raw material for producing cement, so that zero emission of the smelting furnace slag, efficient utilization of high-temperature heat energy and low-cost production are realized.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a process for producing ferroalloy by reducing depleted slag from a silver furnace. Background Art

[0002] Silver furnace depleted slag is waste slag produced during the silver furnace smelting process, which contains a certain amount of valuable metals, such as iron, copper, etc. At present, the main treatment method for silver furnace depleted slag is storage or landfill, which not only occupies a large amount of land resources, but also causes environmental pollution and waste of resources. Therefore, it is of great economic and environmental significance to develop an effective silver furnace depleted slag treatment process to achieve resource recycling.

[0003] The iron in copper smelting slag mainly exists in the form of 2FeO·SiO2. Since the density of high-temperature molten slag is much greater than that of solid reducing agent (such as coke), how to achieve good contact between solid reducing agent and molten slag to accelerate the reduction reaction is the main technical feature of this patent. Summary of the invention

[0004] The present invention provides a process for producing ferroalloy by reducing depleted slag from a silver furnace, which realizes zero emission of smelting slag, efficient utilization of high-temperature thermal energy and low-cost production, and produces ferroalloy products with high economic value.

[0005] In order to solve the above problems, the process for producing ferroalloy by reducing depleted slag from a silver furnace according to the present invention comprises the following steps: The first step: pre-treat the raw materials, i.e. crush and grind the depleted slag from the silver furnace, and crush and screen the reducing agent; Step 2: Mix the pretreated raw materials, add additives and mix them evenly, and add the evenly mixed mixture into the reduction furnace for reduction smelting; Step 3: Separate the slag and ferroalloy after reduction smelting to obtain ferroalloy products and depleted electric slag; Step 4: Sell the ferroalloy products as pig iron and sell the depleted electric furnace slag as cement.

[0006] The reducing agent is coke powder.

[0007] The above-mentioned additives are lime and fluorite, and the ratio of the additives is CaO / SiO2=0.6.

[0008] The above reduction furnace is an electric furnace.

[0009] During reduction smelting in the above reduction furnace, coke powder is added in multiple times to ensure a reducing atmosphere, and the total feeding time is 30 minutes; the reduction smelting temperature is 1500-1600°C, the reduction smelting insulation time is 2-4 hours, and the atmosphere in the furnace is a reducing atmosphere.

[0010] The above-mentioned silver furnace depleted slag is crushed and ground to make its particle size less than 100 mesh; the reducing agent is crushed and screened, and the reducing agent with a particle size of 10-50mm is selected for standby use.

[0011] The mass ratio of the above-mentioned silver furnace depleted slag, reducing agent and additive is 100:15~25:10~15.

[0012] The above separation of the slag and the ferroalloy after reduction smelting includes using a gravity separation method to separate the ferroalloy from the slag to obtain a ferroalloy product and a depleted electric slag.

[0013] The invention uses tailings after mineral processing and depletion, directly performs electric furnace reduction on the molten depleted slag, performs electric furnace reduction smelting in a 40KVA electric arc furnace, maintains the smelting temperature at 1500-1600°C, CaO / SiO2=0.6, uses coke powder as a reducing agent, and the added amount is 15% of the depleted slag. The insulation time is 3h, the iron reduction rate reaches more than 97%, the copper reduction rate reaches more than 95%, the obtained alloy contains more than 86% iron, 8-9% silicon, 0.6-0.7% copper, and less than 0.05% sulfur; the ferroalloy can be sold as pig iron, the depleted electric furnace slag contains more than 50% silicon dioxide and 2% iron, and can be used as a raw material for producing cement; the zero emission of smelting slag, the efficient utilization of high-temperature thermal energy and the low-cost production are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0015] Figure 1 This is a process flow chart of Example 1 of the present invention. DETAILED DESCRIPTION

[0016] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0017] Example 1: Figure 1 As shown, the embodiment of the present invention discloses a process for reducing depleted slag from a silver furnace to produce ferroalloy, comprising the following steps: The first step: pre-treat the raw materials, i.e. crush and grind the depleted slag from the silver furnace, and crush and screen the reducing agent; Step 2: Mix the pretreated raw materials, add additives and mix them evenly, and add the evenly mixed mixture into the reduction furnace for reduction smelting; Step 3: Separate the slag and ferroalloy after reduction smelting to obtain ferroalloy products and depleted electric slag; Step 4: Sell the ferroalloy products as pig iron and sell the depleted electric furnace slag as cement.

[0018] Wherein, the reducing agent is coke powder.

[0019] Among them, the additives are lime and fluorite, and the ratio of the additives is CaO / SiO2=0.6.

[0020] Among them, the reduction furnace is an electric furnace.

[0021] During the reduction smelting in the reduction furnace, coke powder is added in multiple times to ensure the reducing atmosphere, and the total feeding time is 30 minutes; the temperature of the reduction smelting is 1500-1600℃, the reduction smelting holding time is 2-4 hours, and the atmosphere in the furnace is a reducing atmosphere. During the smelting process, the reducing agent reduces the iron oxide in the depleted slag to metallic iron and forms an iron alloy at the same time.

[0022] Among them, the depleted slag of the silver furnace is crushed and ground to make its particle size less than 100 mesh; the reducing agent is crushed and screened, and the reducing agent with a particle size of 10 to 50 mm is selected for use.

[0023] The mass ratio of the depleted slag of the silver furnace, the reducing agent and the additive is 100:15-25:10-15. The reduction rate of iron is improved by mixing the depleted slag of the silver furnace, the reducing agent and the additive in a certain proportion and mixing them evenly in a mixer.

[0024] Among them, the slag and ferroalloy after reduction smelting are separated, including the use of gravity separation method to separate the ferroalloy from the slag to obtain ferroalloy products and depleted electric slag. As a result, the reduction rate of the main component iron reaches more than 97%, and the obtained alloy contains more than 86% iron, 8-9% silicon, 0.6-0.7% copper, and less than 0.05% sulfur, which can be sold as pig iron; the depleted electric slag contains more than 50% silicon dioxide and 2% iron, which can be used as raw material for cement production.

[0025] Example 2: 1) The selection of experimental raw materials in the present invention is as follows: The copper slag of Baiyin furnace is firstly subjected to mineral processing and depletion, and the depleted slag is then subjected to reduction smelting, and the raw material for reduction smelting is the depleted slag of tailings from mineral processing of copper slag. The depleted slag samples were subjected to ICP analysis and chemical analysis, and the results are listed in Table 1 and Table 2.

[0026] 2) The experimental research on reduction smelting of depleted slag in electric furnace is as follows: The depleted slag electric furnace reduction smelting test was carried out in a 40kVA single-phase electric arc furnace produced by Xi'an Electric Furnace Plant.

[0027] The arc initiation method for arc furnace melting test was coke initiation (i.e. arc initiation using external coke), with an arc initiation voltage of 40-55V and a current of 260-320A; during melting, the secondary voltage was 80-90V and the secondary current was 300-320A; during the insulation period, the secondary voltage was 50-70V and the secondary current was 150-180A. The melting temperature was measured with an infrared thermometer.

[0028] In the arc furnace test, 12 kg of prepared materials are added to each furnace in batches. After the charge is completely melted and kept warm for a specified time, a hexagonal iron rod is inserted into the slag layer in the furnace to a depth of 15 to 20 mm, and the slag sample is taken for analysis after two rotations. Then, the heat is applied for 10 minutes, and the melt is poured into the iron ladle. After natural cooling, the slag and gold are separated, and samples are taken for analysis again.

[0029] 3) The analysis process of the influence of reducing agent dosage is as follows: The depleted slag is 12kg, and the reducing agent is coke powder. Before smelting, a layer of depleted slag is first laid on the bottom of the furnace, and then power is supplied, and coke is used to strike the arc. The voltage during arc striking is 50V, and the current is 300A. The voltage during charging is 85V, and the current is 300-340A. The voltage during reduction smelting is 85-100V, and the current is 300-340A. In order to strengthen the reduction of iron in the charge, coke powder is added four times during smelting to ensure the required strong reducing atmosphere. The charging time is 24min, the holding time is 4h, the smelting temperature is 1500-1600℃, and CaO / SiO2=0.6. The test results of the reducing agent dosage are shown in Table 3.

[0030] The test results of reducing agent dosage show that when 10% of coke powder is added to the lean slag, the iron reduction rate is only 92.23%. When the coke powder dosage reaches more than 15%, the iron reduction rate can reach more than 97%. Therefore, the reducing agent dosage is 15% of the lean slag.

[0031] 4) The test of the influence of smelting time is as follows: The depleted slag is 12kg, the reducing agent is coke powder, and the amount of coke powder is 15% of the depleted slag. Before smelting, a layer of depleted slag is first laid on the bottom of the furnace, and then power is supplied, and coke is used to strike the arc. The voltage during arc striking is 50V, the current is 300A, the voltage during charging is 85V, the current is 300-340A, and the voltage during reduction smelting is 85-100V, and the current is 300-340A. In order to strengthen the reduction of iron in the charge, coke powder is added four times during smelting to ensure the required strong reducing atmosphere, and the charging time is 24min. The smelting temperature is 1500-1600℃, and CaO / SiO2=0.6. The results of the smelting time test are shown in Table 4.

[0032] The test results show that when the reduction smelting holding time is 3 hours, the iron reduction rate reaches 97.96%. If the holding time is extended, the iron reduction rate does not increase, but the energy consumption increases. Therefore, the reduction smelting holding time is determined to be 3 hours.

[0033] Example 3: This example discloses a process for reducing depleted slag from a silver furnace to produce ferroalloys. The main component in the depleted slag from the silver furnace is Fe: 36.92% by weight.

[0034] (1) The depleted slag of the silver furnace is crushed and ground to a particle size of less than 80 mesh. At the same time, the reducing agent coke is crushed and screened, and the reducing agent with a particle size of 30 mm is selected for standby use.

[0035] (2) The pretreated depleted silver furnace slag, the reducing agent, and the additive fluorite and lime are mixed in a certain ratio and fully mixed in a mixer. The mass ratio of the depleted silver furnace slag, the reducing agent, and the additive is 100:15:10.

[0036] (3) The mixed materials are added to the electric furnace for reduction smelting. In order to strengthen the reduction of iron in the charge, coke powder is added four times during smelting to ensure the required strong reducing atmosphere. The feeding time is 24 minutes. The smelting temperature is controlled at 1500℃, the reduction smelting holding time is 3 hours, and the iron reduction rate reaches 97.96%. During the smelting process, the reducing agent reduces the iron oxide in the depleted slag to metallic iron and forms an iron alloy.

[0037] (4) After smelting, the slag and ferroalloy are discharged from the electric furnace for slag and iron separation. The ferroalloy can be separated from the slag by gravity separation. The obtained alloy contains 86.29% iron, 9.05% silicon, 0.65% copper and 0.04% sulfur, and can be sold as pig iron. The depleted electric furnace slag contains 52.37% silicon dioxide, 1.55% iron and 30.96% calcium oxide. The electric furnace slag can be used as a raw material for cement production.

[0038] Example 4: This example discloses a process for reducing depleted slag from a silver furnace to produce ferroalloys. The main component in the depleted slag from the silver furnace is Fe: 36.92% by weight.

[0039] (1) The depleted slag of the silver furnace is crushed and ground to a particle size of less than 70 mesh. At the same time, the reducing agent coke is crushed and screened, and the reducing agent with a particle size of 40 mm is selected for standby use.

[0040] (2) The pretreated depleted slag from the silver furnace, the reducing agent, and the additive fluorite and lime are mixed in a certain proportion and fully mixed in a mixer. The mass ratio of the depleted slag from the silver furnace, the reducing agent, and the additive is 100:20:12.

[0041] (3) The mixed materials are added to the electric furnace for reduction smelting. In order to strengthen the reduction of iron in the charge, coke powder is added four times during the smelting period to ensure the required strong reducing atmosphere. The feeding time is 24 minutes. The smelting temperature is controlled at 1550℃, the reduction smelting holding time is 4 hours, and the iron reduction rate reaches 97.58%. During the smelting process, the reducing agent reduces the iron oxide in the depleted slag to metallic iron and forms an iron alloy.

[0042] (4) After smelting, the slag and ferroalloy are discharged from the electric furnace for slag and iron separation. The ferroalloy can be separated from the slag by gravity separation. The obtained ferroalloy contains 86.18% iron, 8.34% silicon, 0.64% copper and 0.04% sulfur, and can be sold as pig iron. The depleted electric furnace slag contains 51.56% silicon dioxide, 2.1% iron and 29.43% calcium oxide. The electric furnace slag can be used as a raw material for cement production.

[0043] In summary, the present invention provides a process method for producing ferroalloy by reducing depleted slag from a silver furnace, wherein tailings after mineral processing depletion are selected, and the molten depleted slag is directly reduced in an electric furnace, and electric furnace reduction smelting is carried out in a 40KVA electric arc furnace, the smelting temperature is maintained at 1500-1600°C, CaO / SiO2=0.6, coke powder is used as a reducing agent, the addition amount is 15% of the depleted slag, the insulation time is 3h, the iron reduction rate reaches more than 97%, the copper reduction rate is more than 95%, the obtained alloy contains more than 86% iron, 8-9% silicon, 0.6-0.7% copper, and less than 0.05% sulfur; the ferroalloy can be sold as pig iron, the depleted electric furnace slag contains more than 50% silicon dioxide and 2% iron, and can be used as a raw material for producing cement; zero emission of smelting slag, efficient utilization of high-temperature thermal energy and low-cost production are achieved.

[0044] Table 1 ICP analysis results of depleted slag (%) Table 2 Chemical analysis results of depleted slag (%) Table 3 Test results of reducing agent dosage Table 4 Melting time test results

Claims

1. A process for reducing depleted slag from a silver furnace to produce ferroalloy, characterized in that: The following steps are involved: The first step: pre-treat the raw materials, i.e. crush and grind the depleted slag from the silver furnace, and crush and screen the reducing agent; Step 2: Mix the pretreated raw materials, add additives and mix them evenly, and add the evenly mixed mixture into the reduction furnace for reduction smelting; Step 3: Separate the slag and ferroalloy after reduction smelting to obtain ferroalloy products and depleted electric slag; Step 4: Sell the ferroalloy products as pig iron and sell the depleted electric furnace slag as cement.

2. The process for producing ferroalloy by reducing depleted slag from a silver furnace according to claim 1, characterized in that: The reducing agent is coke powder.

3. The process for producing ferroalloy by reducing depleted slag from a silver furnace according to claim 1, characterized in that: The additives are lime and fluorite, and the ratio of the additives is CaO / SiO2=0.

6.

4. The process for producing ferroalloy by reducing depleted slag from a silver furnace according to claim 1, characterized in that: The reduction furnace is an electric furnace.

5. The process for producing ferroalloy by reducing depleted slag from a silver furnace according to claim 1, characterized in that: During reduction smelting in the reduction furnace, coke powder is added in multiple times to ensure a reducing atmosphere, and the total feeding time is 30 minutes; the reduction smelting temperature is 1500-1600°C, the reduction smelting insulation time is 2-4 hours, and the atmosphere in the furnace is a reducing atmosphere.

6. The process for producing ferroalloy by reducing depleted slag from a silver furnace according to claim 1, characterized in that: The depleted slag of the silver furnace is crushed and ground to a particle size less than 100 mesh; the reducing agent is crushed and screened, and the reducing agent with a particle size of 10 to 50 mm is selected for use.

7. The process for producing ferroalloy by reducing depleted slag from a silver furnace according to claim 1, characterized in that: The mass ratio of the depleted slag, reducing agent and additive of the silver furnace is 100:15~25:10~15.

8. The process for producing ferroalloy by reducing depleted slag from a silver furnace according to claim 1, characterized in that: The slag and ferroalloy after reduction smelting are separated, including using a gravity separation method to separate the ferroalloy from the slag to obtain a ferroalloy product and a depleted electric slag.

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