Silicon thermal magnesium smelting anti-moisture absorption high-strength anti-sticking tank sintered material balls and preparation method thereof

Abstract

The invention discloses a high-strength, anti-sticking sintered ball for magnesium smelting by a silicon thermal process, which is moisture-absorbing and anti-adhesive, and a preparation method thereof. The ball comprises the following steps: step A: preparing raw materials: calcining dolomite, ferrosilicon and fluorite according to a certain mass ratio to prepare raw materials; step B: finely grinding the raw materials: placing the prepared raw materials into a ball mill for ball milling; step C: pressing into balls: pressing the obtained raw material powder into balls; and step D: high-temperature sintering; during the sintering process, a silicon-calcium compound is generated, which has stable chemical properties and is not easy to react with water. The silicon-calcium compound in a molten state at high temperature enters the pores of the ball or wraps the ball, thereby greatly reducing the moisture absorption of the sintered ball. On the other hand, the silicon-calcium compound has high bonding force and strength, which greatly increases the strength of the sintered ball. Therefore, the moisture absorption, pulverization and crushing and pulverization phenomena of the magnesium smelting ball by the silicon thermal process are solved, thereby effectively improving the occurrence of sticking in the magnesium smelting reduction process by the silicon thermal process.

Description

Technical Field

[0001] The invention belongs to the technical field of magnesium smelting, and particularly relates to a high-strength, anti-sticking pot sintered material ball for magnesium smelting by silicon thermal method and a preparation method thereof. Background Art

[0002] Currently, the Pidgeon process is the primary method for smelting primary magnesium in my country, accounting for over 80% of global production. While the process is mature, it suffers from issues such as high-temperature manual labor and low intermittent production efficiency. Vertical tank magnesium smelting technology is considered an important development direction due to its continuous production and high degree of mechanization. However, in practice, slag removal problems caused by pellets "sticking" to the tank are common, severely hindering mechanization and automation and disrupting production continuity. Research has shown that the sticking phenomenon is closely related to the pulverization of pellets due to moisture absorption and breakage in the high-temperature reduction tank. Specifically, the enrichment of the powder phase in the reduction tank leads to an increase in the molten phase, which then adheres to the tank wall.

[0003] Chinese patents CN220339121U, CN115727683A, and CN115183596A all involve slag removal equipment for vertical tanks used in magnesium smelting. The three are mainly improvements on the mechanical structure of the vertical tank. By using mechanically controlled slag removal plates, grinding mechanisms, or scraper plates instead of manual slag removal, the slag removal efficiency and safety can be improved to a certain extent. However, the equipment structure of these methods is relatively complex, containing multiple components and connecting parts, which may result in high manufacturing and maintenance costs. Although the design is intended to improve slag removal efficiency, if the equipment fails or is improperly maintained, it may reduce the slag removal efficiency and even lead to production interruptions.

[0004] In summary, existing patented technologies for addressing the "sticking" issue in magnesium smelting using the silicon-thermal process primarily focus on developing slag removal equipment, whose practicality remains to be verified. Therefore, there is an urgent need to develop specialized magnesium smelting pellets that combine moisture absorption resistance, high-strength molding, and cost-effectiveness to address the sticking issue, improve the mechanization and automation of the magnesium smelting process, and ensure continuous production. Summary of the Invention

[0005] The present invention aims to solve the problem of slag removal difficulty caused by sticking in existing magnesium smelting by silicon thermal process, and proposes a sintered material ball with high strength and anti-sticking performance for magnesium smelting by silicon thermal process and a preparation method thereof. The material ball is a special material ball for magnesium smelting that is anti-moisture absorption, high strength, high thermal conductivity, anti-sticking performance and cost-controlled. The technical solution adopted to achieve the above purpose is:

[0006] A method for preparing high-strength, anti-sticking sintered pellets for magnesium smelting by silicon thermal method, comprising the following steps:

[0007] Step A: Prepare the raw materials by mass ratio of calcined dolomite: ferrosilicon: fluorite = 100: (15-21): (0-3);

[0008] Step B: Fine grinding of raw materials: Place the prepared raw materials into a ball mill and perform ball milling to obtain a uniformly mixed raw material powder of 80-200 mesh;

[0009] Step C: pressing into balls: pressing the obtained raw material powder into balls;

[0010] Step D: High-temperature sintering: The pellets are placed in a high-temperature furnace and sintered in a high-temperature inert gas atmosphere or under high-temperature low-vacuum conditions, so that the elemental Si and FeSi2 in the ferrosilicon in the pellets react with the CaO in the calcined dolomite to generate molten silicon-calcium compounds. The molten silicon-calcium compounds are partially located in the pores of the pellets and partially adhere to the surface layer of the pellets to form sintered pellets.

[0011] Preferably, in step D, when a high-temperature inert gas atmosphere is used in the high-temperature furnace, the sintering temperature is 1000° C.<T<1300° C., and the high-temperature furnace maintains an inert gas atmosphere without the presence of oxidizing gas.

[0012] Preferably, in step D, when a high temperature and low vacuum atmosphere is used in the high temperature furnace, the high temperature and low vacuum conditions are: sintering temperature 1000°C < T < 1300°C, absolute pressure P satisfies -5.594×10 -6 T 2 +0.0187T-10.757<lgP<4.5, where lgP is the common logarithm of the absolute pressure P, the unit of the absolute pressure P is Pa, and the unit of the sintering temperature T is °C.

[0013] Preferably, in step D, the molten calcium-silicon compound flows into different pores of the ball and forms a special-shaped connector embedded with the sintered ball, and the sintered ball as a whole has electrical conductivity.

[0014] Also disclosed is a silicon thermal magnesium sintering anti-moisture absorption high-strength anti-sticking tank sintered material ball prepared according to the above preparation method.

[0015] Also disclosed is a magnesium smelting method using the sintered pellets as raw materials.

[0016] Also disclosed is an induction heating magnesium smelting method using the sintered pellets as raw materials, wherein the sintered pellets are placed in an induction heating environment to smelt metallic magnesium.

[0017] The beneficial effects of the present invention are as follows: (1) the silicon-calcium compounds generated during the sintering process, such as calcium disilicide (CaSi2), are chemically relatively stable and do not easily react with water. The molten silicon-calcium compounds enter the pores of the balls or wrap the balls, thereby greatly reducing the water absorption of the sintered balls; on the other hand, the silicon-calcium compounds have high bonding force and strength, which greatly increases the strength and wear resistance of the sintered balls. Therefore, the pulverization phenomenon of the sintered balls in the high-temperature reduction tank is solved, thereby effectively improving the occurrence of the "sticking to the tank and glazing" phenomenon.

[0018] (2) The silicon-calcium compound generated during the sintering process has a high thermal conductivity coefficient and can transfer heat quickly. After sintering, the internal structure of the ball is reconstructed. The silicon-calcium compound is interconnected in three-dimensional space, and the porosity of the ball is reduced, which improves the thermal conductivity of the ball. The heat in the reduction tank can be quickly transferred from the tank wall to the sintered ball, thereby increasing the reduction reaction rate, shortening the reduction cycle, and reducing energy consumption.

[0019] (3) The silicon-calcium compound generated during the sintering process has conductive properties. When the molten silicon-calcium compound enters the different pores of the ball, it flows into each other to form a special-shaped connector embedded with the sintered ball, making the sintered ball as a whole conductive. Therefore, the sintered ball can also be used in the induction heating magnesium smelting process.

[0020] (4) Since silicon-calcium compounds exist on the surface and inside of the sintered balls, when induction heating is used, the sintered balls can be heated efficiently and quickly both inside and outside, thereby improving the smelting efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 IgP-T curve of the reaction of reducing calcium silicon compound to generate magnesium vapor;

[0022] Figure 2 The figures are comparison diagrams of the micromorphology of the sintered pellets before and after sintering; Figure a shows the micromorphology and element distribution of the pellets before sintering, and Figure b shows the micromorphology and element distribution of the sintered pellets;

[0023] Figure 3 This is a comparison chart of the water absorption and pulverization experiments of the sintered balls of the present invention and ordinary balls. DETAILED DESCRIPTION

[0024] The following describes several preferred embodiments of the present invention with reference to the accompanying drawings to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0025] The present invention discloses a method for preparing high-strength sintered material balls by silicon thermal magnesium smelting and moisture absorption prevention, comprising the following steps:

[0026] Step A: Raw material preparation: According to the mass ratio of calcined dolomite: ferrosilicon: fluorite = 100: (15-21): (0-3). Fluorite within the above ratio range can be added as a catalyst to accelerate the reaction when necessary.

[0027] Step B: Fine grinding of raw materials: Place the prepared raw materials into a ball mill and perform ball milling to obtain a uniformly mixed raw material powder of 80-200 mesh;

[0028] Step C: Pressing the obtained raw material powder into balls, preferably at a pressure of 25-200 MPa;

[0029] Step D: High-temperature sintering: The pellets are placed in a high-temperature furnace and sintered in a high-temperature inert gas atmosphere or under high-temperature, low-vacuum conditions. This allows the elemental Si and FeSi2 in the ferrosilicon in the pellets to react with the CaO in the calcined dolomite to form molten silicon-calcium compounds. The molten silicon-calcium compounds then enter the pores of the pellets or envelop them, forming sintered pellets. The reaction process is as follows:

[0030] 5Si + 4CaO = 2CaSi2 + Ca2SiO4 (1)

[0031] 5FeSi2 + 4CaO = 2CaSi2 + 5FeSi + Ca2SiO4 (2)

[0032] 2CaSi2 + 6CaO + 10MgO = 10Mg (g) + 4Ca2SiO4 (3)

[0033] In step D, when a high-temperature inert gas atmosphere is used in the high-temperature furnace, the sintering temperature is 1000°C < T < 1300°C, and the high-temperature furnace maintains an inert gas atmosphere without the presence of oxidizing gas to ensure that the reaction of Si, FeSi2 with CaO in the calcined dolomite to form silicon-calcium compounds proceeds normally. Otherwise, the oxidizing gas will react with the ferrosilicon particles to form a layer of silicon oxide on the surface of the ferrosilicon particles, hindering the occurrence of reaction formula (1) and reaction formula (2).

[0034] In step D, when a high temperature and low vacuum atmosphere is used in the high temperature furnace, the high temperature and low vacuum conditions are: sintering temperature 1000℃<T<1300℃, absolute pressure P satisfies -5.594×10 -6 T 2+0.0187T-10.757<lgP<4.5, where lgP is the common logarithm of the absolute pressure P, expressed in Pa, and the sintering temperature T in °C. The absolute pressure should not be too high to ensure that there is no large amount of oxidizing gas in the high-temperature furnace, thereby ensuring the normal reaction of Si, FeSi2, and CaO in the calcined dolomite to form a silicon-calcium alloy. The absolute pressure should not be too low to ensure that the generated silicon-calcium alloy does not react with and be consumed by MgO in the calcined dolomite.

[0035] like Figure 1 As shown, when the lgP value is at the upper part of the curve, that is, lgP>-5.594×10 -6 T 2 When the value of IgP is between +0.0187T and -10.757, reaction (3) will not occur, meaning the generated calcium-silicon alloy will not be consumed. However, the IgP value cannot be too high, otherwise excessive oxidizing gases will be generated, hindering the occurrence of reactions (1) and (2). Preferably, the raw material powder is pressed into pellets at a pressure of 25-200 MPa.

[0036] In step D, the criterion for determining whether the sintering of the pellets in the high-temperature furnace is complete is whether a silicon-calcium compound is generated.

[0037] Furthermore, a compressive strength test was conducted on the sintered balls. The experimental results showed that the compressive strength of the sintered balls was 15-26 MPa, while the compressive strength of the unsintered balls was 5-6 MPa. It is obvious that the compressive strength of the sintered balls of the present invention is greatly improved.

[0038] Figure 2 Figure a shows the micromorphology and element distribution before sintering, while Figure b shows the micromorphology and element distribution of the sintered pellets. A comparison shows that in the pellets before sintering, Ca is distributed in the calcined white, while Si is distributed in the silicon particles. The interface between the two is clear and non-overlapping. The overlap of Ca and Si in the sintered pellets indicates that a reaction occurred within the pellets during the sintering process, forming a silicon-calcium compound. Furthermore, the calcined white in Figure a has a distinct granular feel, with micropores between the particles. In contrast, the silicon-calcium compound in Figure b solidifies from a high-temperature liquid state, resulting in a dense internal structure and a significantly larger proportion of the pellet volume. Its three-dimensional, continuous distribution facilitates heat conduction.

[0039] Figure 3 This is a comparison chart of the water absorption and pulverization experiments of the sintered balls of the present invention and ordinary balls. It can be seen from the figure that the balls before sintering are very easy to absorb moisture and crack, while after sintering, there are only a few cracks on the surface of the balls, showing excellent moisture absorption resistance.

[0040] The present invention also discloses a silicon thermal magnesium smelting anti-moisture absorption high-strength anti-sticking tank sintered material ball prepared according to the preparation method and a metal magnesium smelting method using the sintered material ball as a raw material. Specific embodiments

[0041] Step A: Prepare the raw materials in a mass ratio of calcined dolomite to ferrosilicon (75%) = 100:21.

[0042] Step B: Fine grinding of raw materials: Place the prepared raw materials into a ball mill for ball milling, and sieve through a sieve to obtain a uniformly mixed raw material powder of 100 mesh;

[0043] Step C: Pressing into balls: Pressing the obtained raw material powder into balls under a pressure of 75 MPa;

[0044] Step D: High-temperature sintering: Place the pellets in a high-temperature furnace and sinter under high-temperature, low-vacuum conditions. Control the vacuum degree to 8000 Pa and keep them at 1050°C for 30 minutes. During this process, the elemental Si and FeSi2 in the ferrosilicon in the pellets react with the CaO in the calcined dolomite to generate molten silicon-calcium compounds. The molten silicon-calcium compounds enter the pores of the pellets or wrap the pellets to form sintered pellets.

[0045] Furthermore, a compressive strength test was conducted on the sintered balls. The experimental results showed that the compressive strength of the sintered balls was 15 MPa, while the compressive strength of the unsintered balls was 5.5 MPa. It is obvious that the compressive strength of the sintered balls of the present invention is increased by about two times. Specific embodiments

[0046] Step A: Prepare the raw materials in a mass ratio of calcined dolomite: 75 ferrosilicon: fluorite = 100:15:2.

[0047] Step B: Fine grinding of raw materials: The prepared raw materials are placed in a ball mill for ball milling, and sieved through a sieve to obtain a uniformly mixed raw material powder of 150 mesh;

[0048] Step C: Pressing into balls: Pressing the obtained raw material powder into balls under a pressure of 25 MPa;

[0049] Step D: High-temperature sintering: Place the pellets in a high-temperature furnace and sinter under high-temperature, low-vacuum conditions. Control the vacuum degree to 6000 Pa and keep them at 1200°C for 10 minutes. During this process, the elemental Si and FeSi2 in the ferrosilicon in the pellets react with the CaO in the calcined dolomite to generate molten silicon-calcium compounds. The molten silicon-calcium compounds enter the pores of the pellets or wrap the pellets to form sintered pellets.

[0050] Furthermore, a compressive strength test was conducted on the sintered balls. The experimental results showed that the compressive strength of the sintered balls was 17 MPa, while the compressive strength of the unsintered balls was 5 MPa. It is obvious that the compressive strength of the sintered balls of the present invention is increased by more than 3 times. Specific embodiments

[0051] Step A: Prepare the raw materials in a mass ratio of calcined dolomite to 75% ferrosilicon at 100:17.

[0052] Step B: Fine grinding of raw materials: Place the prepared raw materials into a ball mill for ball milling, and sieve through a sieve to obtain a uniformly mixed raw material powder of 100 mesh;

[0053] Step C: Pressing the obtained raw material powder into balls under a pressure of 150 MPa;

[0054] Step D: High-temperature sintering: Place the pellets in a high-temperature furnace and sinter under high-temperature, low-vacuum conditions. Control the vacuum degree to 5000 Pa and keep them at 1200°C for 90 minutes. During this process, the elemental Si and FeSi2 in the ferrosilicon in the pellets react with the CaO in the calcined dolomite to generate molten silicon-calcium compounds. The molten silicon-calcium compounds enter the pores of the pellets or wrap the pellets to form sintered pellets.

[0055] Furthermore, a compressive strength test was conducted on the sintered balls. The experimental results showed that the compressive strength of the sintered balls was 15 MPa, while the compressive strength of the unsintered balls was 5 MPa. It is obvious that the compressive strength of the sintered balls of the present invention is increased by 3 times. Specific embodiments

[0056] Step A: Prepare the raw materials in a mass ratio of calcined dolomite: 75% ferrosilicon: fluorite = 100:20:1.

[0057] Step B: Fine grinding of raw materials: Place the prepared raw materials into a ball mill for ball milling, and sieve through a sieve to obtain a uniformly mixed raw material powder of 100 mesh;

[0058] Step C: Pressing into balls: Pressing the obtained raw material powder into balls under a pressure of 75 MPa;

[0059] Step D: High-temperature sintering: Place the pellets in a high-temperature furnace and sinter under high-temperature, low-vacuum conditions. Control the vacuum degree to 8000 Pa and keep them at 1050°C for 30 minutes. During this process, the elemental Si and FeSi2 in the ferrosilicon in the pellets react with the CaO in the calcined dolomite to generate molten silicon-calcium compounds. The molten silicon-calcium compounds enter the pores of the pellets or wrap the pellets to form sintered pellets.

[0060] Furthermore, a compressive strength test was conducted on the sintered balls. The experimental results showed that the compressive strength of the sintered balls was 18 MPa, while the compressive strength of the unsintered balls was 5 MPa. It is obvious that the compressive strength of the sintered balls of the present invention is increased by more than 3 times.

[0061] The preferred embodiments of the present invention have been described in detail above. It should be understood that numerous modifications and variations based on the concepts of the present invention are possible without inventive effort by those skilled in the art. Therefore, any technical solution that can be derived by one skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for preparing high-strength, anti-sticking sintered pellets for magnesium smelting by silicon thermal method, characterized in that: The steps include: Step A: Prepare the raw materials by mass ratio of calcined dolomite: ferrosilicon: fluorite = 100: (15-21): (0-3); Step B: Fine grinding of raw materials: Place the prepared raw materials into a ball mill and perform ball milling to obtain a uniformly mixed raw material powder of 80-200 mesh; Step C: pressing into balls: pressing the obtained raw material powder into balls; Step D: High-temperature sintering: The pellets are placed in a high-temperature furnace and sintered in a high-temperature inert gas atmosphere or a high-temperature low-vacuum condition, so that the elemental Si and FeSi2 in the ferrosilicon in the pellets react with the CaO in the calcined dolomite to form a molten silicon-calcium compound, and the molten silicon-calcium compound is connected to the pellets; In step D, when a high temperature and low vacuum atmosphere is used in the high temperature furnace, the high temperature and low vacuum conditions are: sintering temperature 1000℃<T<1300℃, absolute pressure P satisfies -5.594×10 -6 T 2 +0.0187T-10.757<lgP<4.5, where lgP is the common logarithm of the absolute pressure P, the unit of the absolute pressure P is Pa, and the unit of the sintering temperature T is °C.

2. The method for preparing high-strength, anti-sticking sintered pellets by silicon thermal magnesium smelting according to claim 1, characterized in that: In step D, when a high-temperature inert gas atmosphere is used in the high-temperature furnace, the sintering temperature is 1000° C.<T<1300° C., and the high-temperature furnace maintains an inert gas atmosphere without the presence of oxidizing gas.

3. The method for preparing high-strength, anti-sticking sintered pellets by silicon thermal magnesium smelting according to claim 1 or 2, characterized in that: In step D, the molten calcium-silicon compound flows into different pores of the ball and forms a special-shaped connector embedded with the sintered ball. The sintered ball has electrical conductivity as a whole.

4. A silicon thermal magnesium sintering ball with high strength and anti-sticking properties obtained by the preparation method according to any one of claims 1 to 3.

5. A magnesium smelting method using the sintered pellets according to claim 3 as raw materials.

6. An induction heating magnesium smelting method using the sintered pellets according to claim 3 as raw materials, characterized in that: The sintered pellets are placed in an induction heating environment for smelting magnesium metal.

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