CN-122012948-A - Calcium carbonate reduction method based on coupling of microwaves and heat conduction

Abstract

The invention discloses a calcium carbonate reduction method based on microwave and heat conduction coupling, and relates to the technical field of metal smelting. The method comprises the steps of raw material pretreatment, material proportioning and forming, sectional microwave pretreatment, microwave-inductive coupling reduction and product separation and recovery, and realizes the cooperative regulation and control of microwave internal heating and inductive heat conduction by optimizing the raw material proportion and introducing a wave-absorbing auxiliary material and combining vacuum degree and temperature parameters designed for the high activity of the metal calcium. The method solves the defects of difficult adaptation of the prior art to the high activity of calcium, insufficient temperature control precision, high energy consumption, low product purity and poor environmental protection, obviously improves the quality and reduction efficiency of the metal calcium, reduces the production energy consumption and cost, has no secondary pollution, has strong process stability, and is suitable for industrial continuous production.

Inventors

• Fang Songwen
• HUANG ZHIMIN
• CHEN XIANRUI
• LI YANMING
• LONG SIYU
• LIU ZHONGLIN

Assignees

• 广西科学院

Dates

Publication Date

20260512

Application Date

20260228

Claims (8)

1. 1. A calcium carbonate reduction method based on microwave and heat conduction coupling is characterized by comprising the following steps: S1, raw material pretreatment, namely calcining calcium carbonate with the purity of more than or equal to 95% for 2-3 hours at 850-950 ℃, and ball-milling to 80-120 meshes to obtain calcined calcium powder, crushing and grinding a reducing agent to 100-150 meshes, grinding a mineralizer to 120 meshes, and treating a wave-absorbing auxiliary material to the granularity of <40 meshes for later use; S2, proportioning and forming, namely calcining calcium powder, a reducing agent, a mineralizing agent and a wave-absorbing auxiliary material according to the mass ratio, wherein the wave-absorbing auxiliary material comprises = (60-75): (15-25): (2-5): (5-10): (1-3), mixing, performing high-energy ball milling to the particle size of less than or equal to 50 mu m, and extruding the mixture into pellets with the diameter of less than or equal to 20mm and the porosity of 15-20% under the pressure of 20-30 MPa; S3, sectional pretreatment, namely conveying the pellets into a closed pretreatment furnace, vacuumizing to 10-20Pa, preheating by microwaves to 900-1100 ℃ and preserving heat for 1-2 hours, and recovering CO 2 generated by preheating; S4, transferring the pretreated pellets into a coupling reduction furnace, vacuumizing to 1-5Pa, heating to 1400-1500 ℃ by microwaves, starting induction heat conduction heating, regulating the temperature to 1600-1800 ℃, and preserving heat for 3-5 hours to perform reduction reaction; s5, separating and recycling the product, namely guiding the calcium steam to a 850-950 ℃ condenser for crystallization and collection through argon, cooling the byproduct waste residue, recycling, and purifying and recycling the argon.
2. 2. The method for reducing calcium carbonate based on coupling of microwaves and heat conduction according to claim 1, wherein the reducing agent in S1 is 75% ferrosilicon or aluminum metal powder with purity more than or equal to 99%, and the ferrosilicon is subjected to surface oxidation layer removal in advance.
3. 3. The method for reducing calcium carbonate based on coupling of microwaves and heat conduction according to claim 1, wherein the mineralizer in S1 is fluorite with CaF 2 being more than or equal to 98%, the wave-absorbing auxiliary material is silicon carbide or graphite powder, and the impurity removing agent is sodium carbonate with purity being more than or equal to 99%.
4. 4. The method for reducing calcium carbonate based on coupling of microwaves and heat conduction according to claim 1, wherein the frequency of the microwaves in S4 is 2450MHz, the microwave power in the preheating stage is 25-35kW, and the microwave power in the reduction stage is 40-60kW.
5. 5. The method for reducing calcium carbonate based on coupling of microwaves and heat conduction according to claim 1, wherein the coupling reduction furnace in S4 adopts a double-layer heat preservation structure, a microwave generator and an induction heating coil are built in, interference rejection is avoided through frequency isolation layout, and cooperative regulation and control of microwave internal heating and induction heat conduction are achieved.
6. 6. The method for reducing calcium carbonate based on coupling of microwave and heat conduction according to claim 1, wherein the by-product in S5 is calcium silicate or calcium aluminate, wherein the CaO content in the calcium silicate is more than or equal to 45%, and the calcium silicate can be used as a raw material of cement clinker or building materials.
7. 7. The method for reducing calcium carbonate based on coupling of microwaves and heat conduction according to claim 1, wherein the vacuum degree in S3 and S4 is controlled by a combination system of a jet pump and a mechanical pump, and the fluctuation range of the vacuum degree is less than or equal to +/-0.5 Pa.
8. 8. The method for reducing calcium carbonate based on coupling of microwaves and heat conduction according to claim 1, wherein the condenser in S5 adopts an inert gas sealing structure, the purity of argon is more than or equal to 99.99%, and the recycling rate is more than or equal to 90%.

Description

Calcium carbonate reduction method based on coupling of microwaves and heat conduction Technical Field The invention relates to the technical field of metal smelting, in particular to a calcium carbonate reduction method based on microwave and heat conduction coupling. Background The metal calcium is used as a high-activity light metal material and has irreplaceable effects in the fields of aerospace, electronic manufacturing, special alloy smelting, chemical deoxidation and desulfurization and the like. The excellent reducibility and physical and chemical characteristics of the catalyst make the catalyst a key raw material in high-end industrial production. At present, the industrial production of the metal calcium is mainly based on traditional processes such as a silicothermic method and an aluminothermic method, along with the rising of microwave metallurgy technology, the advantages of microwave internal heating, uniform temperature rise and high heat efficiency are gradually applied to the field of metal smelting, related technologies are explored in the preparation of metals such as magnesium, a feasible direction is provided for the innovation of the metal calcium smelting process, and the development of an adaptive efficient and accurate smelting technology is needed aiming at the special property that the metal calcium is more active than the magnesium. In the prior art, related patents of microwave smelting are mainly aimed at metals with relatively low activities such as magnesium, for example, a novel process method for smelting magnesium by a continuous electric furnace in a publication No. CN105420516A and a technology for smelting magnesium by microwave heating in a publication No. CN103882247A, although energy consumption optimization and continuous production of magnesium smelting are realized, the reduction reaction of calcium metal has higher requirements on control accuracy of temperature and vacuum degree, and the existing magnesium smelting process cannot be directly adapted, so that problems of incomplete reduction and lower product purity are easy to occur in the calcium smelting process. Meanwhile, although the prior art has an attempt to directly apply microwave heating to preliminary exploration of calcium carbonate reduction, as disclosed in patent CN116496007B, a process for decomposing lime by microwave, the patent discloses application of microwave heating in decomposing calcium carbonate raw materials, and uses pre-decomposition to form a CaO layer to improve the wave-absorbing property of the raw materials, and uses microwave heating to complete calcination and decomposition of limestone, the technology is designed only for preparing calcium oxide by limestone, does not optimize vacuum degree and temperature control parameters for high activity of calcium metal, and does not design a special wave-absorbing auxiliary material and microwave-heat conduction coupling heating mechanism, and only realizes basic wave absorption by self-modification of the raw materials, the heating mode is still single microwave heating, and the attempt to apply the microwave heating to the process of preparing the calcium metal by calcium carbonate reduction can cause the problems of incomplete reduction reaction, low product purity and high energy consumption, and cannot meet the requirement of industrial production. The traditional calcium smelting process depends on a single heating mode, has the defects of high temperature control difficulty, low heat efficiency and high energy consumption, and environmental protection emission indexes in the production process are difficult to meet the current requirements of green metallurgical policies, and meanwhile, the optimization design aiming at the wave absorption characteristics of the calcium smelting raw materials is lacking, so that the improvement of the production efficiency and the product quality is further limited. Disclosure of Invention (One) solving the technical problems Aiming at the defects of the prior art, the invention provides a calcium carbonate reduction method based on coupling of microwaves and heat conduction, which solves the defects that the existing metal calcium smelting technology (such as aluminothermic method, electrolytic method and the existing microwave smelting related technology) has the defects of difficulty in adapting to the high activity of calcium, low temperature control precision and heat efficiency caused by single heating mode, higher energy consumption and environmental protection emission, insufficient product purity and lack of optimization of the wave absorption characteristics of raw materials. (II) technical scheme In order to achieve the aim, the invention is realized by the following technical scheme that the calcium carbonate reduction method based on microwave and heat conduction coupling comprises the following steps: S1, raw material pretreatment, namely calcining calcium carbonate with the pu