A method for resource utilization and high-value utilization of magnesium slag smelting calcium carbide

Abstract

This invention relates to a method for the resource-based and high-value utilization of calcium carbide produced from magnesium slag smelting, belonging to the field of metallurgy. The invention proposes the production of calcium carbide from magnesium slag waste. The main steps are as follows: first, magnesium slag and carbon reducing agent are crushed and screened, then mixed in a certain proportion, and pressed into pellets; the pellets are then smelted at high temperature with carbon blocks in a certain weight ratio; after the smelting product is removed from the furnace, it is refined and crushed to obtain the main product calcium carbide and the by-product ferrosilicon alloy. This invention not only recovers and utilizes the calcium element in industrial magnesium slag to form calcium carbide, but also reduces the silicon and iron elements in the magnesium slag to become reasonable by-products of ferrosilicon. The main product calcium carbide prepared by this invention can be used as a chemical raw material for the production of PVC resin, polyvinyl alcohol, chloroprene rubber, and other chemical products, and can also be used for metal welding and cutting. The by-product ferrosilicon alloy obtained from smelting can be used as a deoxidizer in steelmaking, a reducing agent in magnesium smelting, and an additive in alloy making.

Description

Technical Field

[0001] This invention belongs to the field of metallurgy, specifically relating to a method for the resource utilization and high-value utilization of calcium carbide produced from magnesium slag smelting. Background Technology

[0002] The main methods for preparing metallic magnesium are electrolysis and the Pidgeon process.

[0003] The principle of electrolytic magnesium production is to prepare metallic magnesium by electrolyzing molten anhydrous magnesium chloride under high-temperature conditions. The specific process is as follows: First, anhydrous magnesium chloride is melted and maintained at a high temperature, typically high enough to ensure complete melting and good conductivity. Then, the molten anhydrous magnesium chloride is placed in an electrolytic cell, and an appropriate amount of electrolyte is added to reduce the resistance of the molten salt and improve electrolysis efficiency. During electrolysis, a voltage is applied to the anode and cathode of the electrolytic cell through a DC power supply, causing magnesium ions to gain electrons at the cathode and be reduced to metallic magnesium. Simultaneously, chloride ions at the anode lose electrons to generate chlorine gas. Thus, metallic magnesium accumulates at the cathode, while chlorine gas is produced at the anode. Through proper collection and treatment, both metallic magnesium and chlorine gas can be obtained. The entire electrolytic magnesium production process requires strict control of process parameters such as temperature and pressure to ensure product quality and electrolysis efficiency. The preparation of the raw material, anhydrous magnesium chloride, is also a crucial step, requiring the selection of high-quality magnesium chloride ore powder and a series of processing steps.

[0004] The Pidgeon process for preparing metallic magnesium mainly involves several steps, including dolomite calcination, pelletizing, vacuum thermal reduction, and refining before ingot casting. First, dolomite is heated to 1100℃–1200℃ in a rotary kiln or vertical kiln to produce calcined dolomite (MgO·CaO). Next, the calcined dolomite, ferrosilicon powder, and fluorite powder are metered, ground, and pressed into pellets. Then, the pellets are heated to 1200±10℃ in a reduction vessel and maintained under vacuum (13.3 Pa or higher) for 8–10 hours, allowing the magnesium oxide to be reduced to magnesium vapor by the silicon in the ferrosilicon. The magnesium vapor forms crystalline magnesium, also known as crude magnesium, in the condenser at the front end of the reduction vessel. Finally, the crude magnesium is melted and refined with a solvent at high temperature before being cast into magnesium ingots, i.e., refined magnesium.

[0005] Because of its simple process, low investment, and abundant source of dolomite, the Pidgeon process has become the primary method for producing metallic magnesium in my country. However, this process generates a large amount of magnesium slag, producing 5-7 tons of slag for every ton of magnesium produced. Magnesium slag is an industrial solid waste. Currently, my country has explored various methods for its disposal and utilization, such as using it in cement production, as a soil conditioner, and as a wastewater treatment agent. However, a suitable, large-scale disposal and utilization method has yet to be found. The treatment and utilization of magnesium slag has become a major challenge and bottleneck restricting the development of my country's magnesium industry.

[0006] Literature and patent searches revealed no reports on the use of magnesium slag to prepare calcium carbide as the main product and ferrosilicon alloy as a byproduct. Therefore, this invention has profound significance for the utilization of magnesium slag. Summary of the Invention

[0007] To address the challenge of disposing of large quantities of magnesium slag in my country's magnesium industry, this invention provides a method for the resource utilization and high-value utilization of magnesium slag. This invention proposes using magnesium slag waste to produce calcium carbide as the main product and ferrosilicon alloy as a byproduct. Existing technologies lack reports on the preparation of calcium carbide and ferrosilicon alloys from magnesium slag. This invention, through the resource utilization and high-value utilization of magnesium slag, not only turns waste into treasure, conserves resources, and reduces environmental pollution, but also brings significant economic benefits. The method described in this invention provides a new approach to the recycling and utilization of magnesium slag, enabling more effective use of magnesium slag and effectively solving the problems in the background technology.

[0008] The solution adopted in this invention is as follows:

[0009] A method for the resource utilization and high-value utilization of calcium carbide produced from magnesium slag smelting includes the following steps:

[0010] (1) Magnesium slag is crushed and screened to obtain magnesium slag powder, and carbon reducing agent is crushed and screened to obtain carbon powder and carbon blocks;

[0011] (2) The magnesium slag powder and the carbon powder are mixed in a certain proportion to obtain a mixed powder;

[0012] (3) The mixed powder is pressed into pellets using a high-pressure briquetting machine to obtain pellet material;

[0013] (4) The pellets and the carbon blocks are fed into a high-temperature furnace for high-temperature smelting according to a certain weight ratio;

[0014] (5) After the smelting product is taken out of the furnace, it is refined and crushed to obtain the main product calcium carbide and the by-product ferrosilicon alloy.

[0015] Further, the magnesium slag mentioned in step (1) is magnesium slag produced by the Pidgeon process for producing metallic magnesium, and its main components are: CaO mass percentage of 60-70%; SiO2 mass percentage of 20-35%; Fe2O3 mass percentage of 1-5%; MgO mass percentage of 0.5-3.5%; Al2O3 mass percentage of 0.1-1.5%; and the remainder are impurities; the particle size of the magnesium slag powder is controlled to be ≤3mm.

[0016] Further, the carbon reducing agent in step (1) is one or a mixture of several of anthracite, semi-coke, petroleum coke and charcoal, and the fixed carbon content of the carbon reducing agent is ≥65%.

[0017] Furthermore, the particle size of the carbon powder in step (1) is controlled to be ≤3mm; the particle size of the carbon block is controlled to be 3mm~100mm.

[0018] Further, in step (2), the weight ratio of the magnesium slag powder to the carbon powder is 1.0:(0.5~1.2).

[0019] Furthermore, in step (3), the pressure of the high-pressure briquetting machine pressing the briquetting pellets is 50MPa to 200MPa, and the diameter of the briquetting pellets is 5cm to 12cm.

[0020] Further, the weight ratio of the pellet material to the carbon block material in step (4) is 1.0:(0.1~1.0).

[0021] Further, in step (4), the high-temperature furnace is one of an AC submerged arc furnace, a DC submerged arc furnace, and an induction furnace; the smelting temperature is 1500℃~5000℃; the smelting time is 2h~10h; the main smelting reaction is:

[0022] CaO + 3C = CaC₂ + CO (1)

[0023] SiO2 + C = Si + CO (2)

[0024] Fe2O3+3C=2Fe+3CO2 (3).

[0025] Furthermore, in step (5), the temperature of the smelted product exiting the furnace is 1800-2000℃, and the cooling time is ≥1.5h.

[0026] Furthermore, in step (5), the main product calcium carbide contains ≥80% CaC2+CaO by mass percentage, and the gas release per kilogram of calcium carbide is ≥200L. The by-product ferrosilicon alloy contains ≥10% Si by mass percentage. The particle size of the main product calcium carbide and the by-product ferrosilicon alloy obtained after finishing and crushing are both controlled between 3cm and 20cm.

[0027] Compared with existing technologies, the advantages of this invention are as follows: This invention not only recovers and utilizes the calcium element in industrial magnesium slag to form calcium carbide, but also reduces the silicon and iron elements in the magnesium slag to become reasonable by-products of ferrosilicon. This invention can realize the large-scale resource utilization and high-value utilization of magnesium slag. The main product calcium carbide prepared by this invention can be used as a chemical raw material for the production of PVC resin, polyvinyl alcohol, vinyl acetate, chloroprene rubber and other chemical products, and can also be used for metal welding and cutting; the by-product ferrosilicon alloy obtained by this invention can be used as a deoxidizer in steelmaking, a reducing agent in magnesium smelting, and an additive in alloy making. Attached Figure Description

[0028] Figure 1 This is a flowchart of a method for the resource utilization and high-value utilization of calcium carbide prepared from magnesium slag according to the present invention. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0030] Example 1

[0031] The raw material used in this embodiment is magnesium slag produced by the Pidgeon process for producing metallic magnesium. Its composition is as follows: CaO mass percentage is 63.41%; SiO2 mass percentage is 29.50%; Fe2O3 mass percentage is 3.33%; MgO mass percentage is 2.38%; Al2O3 mass percentage is 0.99%; and the remainder is impurities.

[0032] A method for the resource utilization and high-value utilization of magnesium slag, such as Figure 1 As shown, it includes the following steps:

[0033] (1) Magnesium slag is crushed and screened to obtain magnesium slag powder, and the particle size of magnesium slag powder is controlled to be ≤3mm; carbon reducing agent petroleum coke is crushed and screened to obtain carbon powder and carbon blocks, wherein the fixed carbon content of the carbon reducing agent is 88.21%, the particle size of carbon powder is controlled to be ≤3mm, and the particle size of carbon blocks is controlled to be 3mm~100mm.

[0034] (2) The magnesium slag powder and the carbon powder are mixed in a ratio of 1.0:1.2 to obtain a mixed powder;

[0035] (3) The mixed powder is pressed into pellets using a high-pressure briquetting machine to obtain pellet material. The pressure is 50MPa and the diameter of the pellets is 5cm.

[0036] (4) The pellets and the carbon blocks are fed into a high-temperature furnace at a weight ratio of 1.0:0.1 for high-temperature smelting at 1500℃ for 4 hours.

[0037] (5) The smelting product is discharged from the furnace at a temperature of 1800℃ and a cooling time of 1.5h. After finishing and crushing, the main product calcium carbide and the by-product ferrosilicon alloy are obtained. The main product calcium carbide contains 80% CaC2+CaO by mass percentage and has a gas release of 200L per kilogram. The by-product ferrosilicon alloy contains 10% Si by mass percentage and has a particle size of 3cm.

[0038] Example 2

[0039] The raw material used in this embodiment is magnesium slag produced by the Pidgeon process for producing metallic magnesium. Its composition is as follows: CaO mass percentage is 62.83%; SiO2 mass percentage is 29.97%; Fe2O3 mass percentage is 2.97%; MgO mass percentage is 0.5%; Al2O3 mass percentage is 0.1%; and the remainder is impurities.

[0040] A method for the resource utilization and high-value utilization of magnesium slag includes the following steps:

[0041] (1) Magnesium slag is crushed and screened to obtain magnesium slag powder, and the particle size of magnesium slag powder is controlled to be ≤3mm; carbon reducing agent semi-coke is crushed and screened to obtain carbon powder and carbon blocks, wherein the fixed carbon content of the carbon reducing agent is 65%, the particle size of the carbon powder is controlled to be ≤3mm, and the particle size of the carbon blocks is controlled to be 3mm~100mm.

[0042] (2) The magnesium slag powder and the carbon powder are mixed in a ratio of 1.0:0.5 to obtain a mixed powder;

[0043] (3) The mixed powder is pressed into pellets using a high-pressure briquetting machine to obtain pellet material. The pressure is 150MPa and the diameter of the pellets is 12cm.

[0044] (4) The pellets and the carbon blocks are fed into a high-temperature furnace at a weight ratio of 1.0:0.3 for high-temperature smelting at 2000℃ for 2 hours.

[0045] (5) The smelting product is discharged from the furnace at a temperature of 1850℃ and a cooling time of 2 hours. After finishing and crushing, the main product calcium carbide and the by-product ferrosilicon alloy are obtained. The main product calcium carbide contains 85% CaC2+CaO by mass percentage and has a gas release of 50L per kilogram. The by-product ferrosilicon alloy contains 20% Si by mass percentage and has a particle size of 3cm.

[0046] Example 3

[0047] The raw material used in this embodiment is magnesium slag produced by the Pidgeon process for producing metallic magnesium. Its composition is as follows: CaO mass percentage is 64.7%; SiO2 mass percentage is 30.27%; Fe2O3 mass percentage is 4.05%; MgO mass percentage is 1.0%; Al2O3 mass percentage is 1.5%; and the remainder is impurities.

[0048] A method for the resource utilization and high-value utilization of magnesium slag includes the following steps:

[0049] (1) Magnesium slag is crushed and screened to obtain magnesium slag powder, and the particle size of magnesium slag powder is controlled to be ≤3mm; carbon reducing agent anthracite is crushed and screened to obtain carbon powder and carbon blocks, wherein the fixed carbon content of the carbon reducing agent is 70%, the particle size of the carbon powder is controlled to be ≤3mm; and the particle size of the carbon blocks is controlled to be 3mm~100mm.

[0050] (2) The magnesium slag powder and the carbon powder are mixed in a ratio of 1.0:0.7 to obtain a mixed powder.

[0051] (3) The mixed powder is pressed into pellets using a high-pressure briquetting machine to obtain pellet material. The pressure is 100MPa and the diameter of the pellets is 5cm.

[0052] (4) The pellets and the carbon blocks are fed into a high-temperature furnace at a weight ratio of 1.0:0.5 for high-temperature smelting at 2500℃ for 7 hours.

[0053] (5) The smelting product is discharged from the furnace at a temperature of 1900℃ and a cooling time of 3h. After finishing and crushing, the main product calcium carbide and the by-product ferrosilicon alloy are obtained. The main product calcium carbide contains 85% CaC2+CaO by mass percentage and has a gas release of 270L per kilogram. The by-product ferrosilicon alloy contains 45% Si by mass percentage and has a particle size of 10cm.

[0054] Example 4

[0055] The raw material used in this embodiment is magnesium slag produced by the Pidgeon process for producing metallic magnesium. Its composition is as follows: CaO mass percentage is 66.37%; SiO2 mass percentage is 28.57%; Fe2O3 mass percentage is 3.47%; MgO mass percentage is 1.5%; Al2O3 mass percentage is 0.4%; and the remainder is impurities.

[0056] A method for the resource utilization and high-value utilization of magnesium slag includes the following steps:

[0057] (1) Magnesium slag is crushed and screened to obtain magnesium slag powder, and the particle size of magnesium slag powder is controlled to be ≤3mm; carbon reducing agent charcoal is crushed and screened to obtain carbon powder and carbon blocks, wherein the fixed carbon content of the carbon reducing agent is 75%, the particle size of the carbon powder is controlled to be ≤3mm, and the particle size of the carbon blocks is controlled to be 3mm~100mm.

[0058] (2) The magnesium slag powder and the carbon powder are mixed in a ratio of 1.0:0.9 to obtain a mixed powder;

[0059] (3) The mixed powder is pressed into pellets using a high-pressure briquetting machine to obtain pellet material. The pressure is 200MPa and the diameter of the pellets is 10cm.

[0060] (4) The pellets and the carbon blocks are fed into a high-temperature furnace at a weight ratio of 1.0:0.7 for high-temperature smelting at 3000℃ for 9 hours.

[0061] (5) The smelting product is tapped out of the furnace at a temperature of 1820℃ and a cooling time of 3h. After finishing and crushing, the main product calcium carbide and the by-product ferrosilicon alloy are obtained. The main product calcium carbide contains 90% CaC2+CaO by mass percentage and has a gas release of 280L per kilogram. The by-product ferrosilicon alloy contains 65% Si by mass percentage and has a particle size of 12cm.

[0062] Example 5

[0063] The raw material used in this embodiment is magnesium slag produced by the Pidgeon process for producing metallic magnesium. Its composition is as follows: CaO mass percentage 65.5%; SiO2 mass percentage 25.97%; Fe2O3 mass percentage 3.77%; MgO mass percentage 2.38%; Al2O3 mass percentage 0.99%; and the remainder is impurities.

[0064] A method for the resource utilization and high-value utilization of magnesium slag includes the following steps:

[0065] (1) Magnesium slag is crushed and screened to obtain magnesium slag powder, and the particle size of magnesium slag powder is controlled to be ≤3mm; carbon reducing agent petroleum coke is crushed and screened to obtain carbon powder and carbon blocks, wherein the fixed carbon content of the carbon reducing agent is 85%, the particle size of the carbon powder is controlled to be ≤3mm, and the particle size of the carbon blocks is controlled to be 3mm~100mm.

[0066] (2) The magnesium slag powder and the carbon powder are mixed in a ratio of 1.0:1.3 to obtain a mixed powder;

[0067] (3) The mixed powder is pressed into pellets using a high-pressure briquetting machine to obtain pellet material. The pressure is 50MPa and the diameter of the pellets is 7cm.

[0068] (4) The pellets and the carbon blocks are fed into a high-temperature furnace at a weight ratio of 1.0:0.9 for high-temperature smelting at 3500℃ for 10 hours.

[0069] (5) The smelting product is tapped out of the furnace at a temperature of 1920℃ and a cooling time of 3h. After finishing and crushing, the main product calcium carbide and the by-product ferrosilicon alloy are obtained. The main product calcium carbide contains 86% CaC2+CaO by mass percentage and has a gas release of 265L per kilogram. The by-product ferrosilicon alloy contains 75% Si by mass percentage and has a particle size of 18cm.

[0070] Example 6

[0071] The raw material used in this embodiment is magnesium slag produced by the Pidgeon process for producing metallic magnesium. Its composition is as follows: CaO mass percentage is 67.1%; SiO2 mass percentage is 31.59%; Fe2O3 mass percentage is 2.97%; MgO mass percentage is 3.0%; Al2O3 mass percentage is 0.8%; and the remainder is impurities.

[0072] A method for the resource utilization and high-value utilization of magnesium slag includes the following steps:

[0073] (1) Magnesium slag is crushed and screened to obtain magnesium slag powder, and the particle size of magnesium slag powder is controlled to be ≤3mm; carbon reducing agent semi-coke is crushed and screened to obtain carbon powder and carbon blocks, wherein the fixed carbon content of the carbon reducing agent is 90%, the particle size of the carbon powder is controlled to be ≤3mm, and the particle size of the carbon blocks is controlled to be 3mm~100mm.

[0074] (2) The magnesium slag powder and the carbon powder are mixed in a ratio of 1.0:1.1 to obtain a mixed powder;

[0075] (3) The mixed powder is pressed into pellets using a high-pressure briquetting machine to obtain pellet material. The pressure is 150MPa and the diameter of the pellets is 5cm.

[0076] (4) The pellets and the carbon blocks are fed into a high-temperature furnace at a weight ratio of 1.0:1.0 for high-temperature smelting at 5000℃ for 6 hours.

[0077] (5) The smelting product is discharged from the furnace at a temperature of 1800℃ and a cooling time of 4h. After finishing and crushing, the main product calcium carbide and the by-product ferrosilicon alloy are obtained. The main product calcium carbide contains 91% CaC2+CaO by mass percentage and has a gas release of 295L per kilogram. The by-product ferrosilicon alloy contains 80% Si by mass percentage and has a particle size of 20cm.

Claims

1. A method for resource utilization and high-value utilization of magnesium slag smelting production of calcium carbide, characterized in that, Includes the following steps: (1) Magnesium slag is crushed and screened to obtain magnesium slag powder, and carbon reducing agent is crushed and screened to obtain carbon powder and carbon blocks; (2) The magnesium slag powder and the carbon powder are mixed in a certain proportion to obtain a mixed powder; (3) The mixed powder is pressed into pellets using a high-pressure briquetting machine to obtain pellet material; (4) The pellets and the carbon blocks are fed into a high-temperature furnace in a certain weight ratio for high-temperature smelting; (5) After the smelting products are taken out of the furnace, they are refined and crushed to obtain the main product calcium carbide and the by-product ferrosilicon alloy; The magnesium slag mentioned in step (1) is the magnesium slag produced by the Pidgeon process for producing metallic magnesium. Its main components are: CaO mass percentage of 60~70%; SiO2 mass percentage of 20~35%; Fe2O3 mass percentage of 1~5%; MgO mass percentage of 0.5~3.5%; Al2O3 mass percentage of 0.1~1.5%; and the remainder are impurities. The particle size of the magnesium slag powder is controlled to be ≤3mm. The carbon reducing agent mentioned in step (1) is one or a mixture of several of anthracite, semi-coke, petroleum coke, and charcoal, and the fixed carbon content of the carbon reducing agent is ≥65%; In step (2), the weight ratio of magnesium slag powder to carbon powder is 1.0 : (0.5~1.2); The weight ratio of pellets to carbon blocks mentioned in step (4) is 1.0 : (0.1~1.0); In step (4), the high-temperature furnace is one of an AC submerged arc furnace, a DC submerged arc furnace, and an induction furnace; the smelting temperature is 2000℃~5000℃; the smelting time is 2h~10h; the main smelting reaction is: CaO + 3C = CaC2 + CO (1) SiO2+C=Si+CO (2) Fe2O3+3C=2Fe+3CO2(3) 2. The method according to claim 1, wherein, The particle size of the carbon powder in step (1) is controlled to be ≤3mm; the particle size of the carbon block is controlled to be 3mm~100mm.

3. The method according to claim 1, wherein, In step (3), the pressure of the high-pressure briquetting machine for pressing the briquetting balls is 50MPa ~ 200MPa, and the diameter of the briquetting balls is 5cm ~ 12cm.

4. The method for resource utilization and high-value utilization of calcium carbide produced from magnesium slag smelting according to claim 1, characterized in that, In step (5), the temperature of the smelted product exiting the furnace is 1800~2000℃ and the cooling time is ≥1.5h.

5. The method for resource utilization and high-value utilization of calcium carbide produced from magnesium slag smelting according to claim 1, characterized in that, In step (5), the main product calcium carbide contains ≥80% CaC2+CaO by mass percentage, and the gas release per kilogram of calcium carbide is ≥200L. The by-product ferrosilicon alloy contains ≥10% Si by mass percentage. The particle size of the main product calcium carbide and the by-product ferrosilicon alloy obtained after finishing and crushing are controlled between 3cm and 20cm.

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