Method for preparing magnesium metal from photovoltaic silicon sludge

Abstract

The invention provides a method for preparing magnesium metal by utilizing photovoltaic silicon sludge. The method comprises the following steps: heating and drying the photovoltaic silicon sludge and cooling to room temperature; preparing the cooled photovoltaic silicon sludge into blocky silicon sludge; adding the blocky silicon sludge into an induction furnace, and heating the induction furnace to a preset temperature, so that the blocky silicon sludge is molten and a liquid silicon molten pool is formed in the induction furnace; and magnesium-containing raw material calcined white powder is sprayed into the liquid silicon molten pool, so that the magnesium-containing raw material calcined white powder reacts with silicon in the liquid silicon molten pool, and metal magnesium steam is generated. According to the invention, the problems of environmental pollution and low utilization rate of the solid waste silicon sludge in the photovoltaic industry at present can be solved.

Description

Technical Field

[0001] The present invention relates to the field of smelting technology, and more specifically, to a method for preparing metallic magnesium by utilizing photovoltaic silicon mud. Background Art

[0002] At present, the production methods of magnesium metal are mainly divided into two categories: electrolysis and thermal reduction. Among them, due to the difficulty in overcoming environmental problems in the electrolysis method, less than 20% of the global magnesium metal production is produced by electrolysis, and most of the remaining magnesium metal is obtained by smelting by thermal reduction. The main process of thermal reduction is silicon thermal reduction, that is, using silicon as a reducing agent to reduce magnesium oxide, obtaining magnesium metal vapor under high temperature and vacuum conditions, and then condensing to obtain solid magnesium. The mainstream process is the Pijiang process. However, its energy consumption is relatively high. At present, the total energy consumption required to produce a ton of magnesium is about 5.77tce (of which the energy consumption of ferrosilicon production is 1.27tce, accounting for more than 20% of the total energy consumption). Therefore, reducing the energy consumption of the raw magnesium smelting process is the only way for the raw magnesium industry to develop in the direction of green and low carbon.

[0003] The disadvantages of the existing mainstream magnesium smelting process (Pidgeon process) are as follows:

[0004] (1) The magnesium smelting process has high energy consumption, among which the energy consumption of ferrosilicon production as a reducing agent accounts for more than 20% of the total energy consumption, and ferrosilicon accounts for more than 60% of the total raw material cost.

[0005] (2) When 75% SiFe is used as a reducing agent, the elemental silicon and ferrosilicon phase each account for about 50%, resulting in a decrease in its reactivity in the silicon thermal reaction, and thus a lower reduction rate, usually not higher than 80%.

[0006] (3) The production scale of a single factory is small and the efficiency is low. It is impossible to achieve mechanized and automated production, and the pollution is serious.

[0007] In addition, the silicon mud generated by the photovoltaic industry will increase from an average of 117,000 tons in 2021 to 286,000 tons in 2023. With the further development of the photovoltaic industry in the future, this figure will be higher, and it is predicted that it will exceed 500,000 tons in 2025. At present, the recycling and reuse of silicon mud is mainly concentrated in the preparation of high-purity silicon, silicon alloys and ceramics, but its scale and application are very small, so it may cause huge waste of resources and environmental pollution. At present, the photovoltaic industry is facing the pressure of how to effectively deal with this solid waste problem.

[0008] Therefore, in order to solve the above problems, the present invention provides a method for producing metallic magnesium using photovoltaic solid waste silicon mud. Summary of the invention

[0009] In view of the above problems, the purpose of the present invention is to provide a method for preparing metallic magnesium using photovoltaic silicon mud, so as to solve the current problems of solid waste silicon mud polluting the environment and low utilization rate in the photovoltaic industry.

[0010] The present invention provides a method for preparing metallic magnesium by using photovoltaic silicon mud, comprising:

[0011] Heat and dry the photovoltaic silicon mud and cool it to room temperature;

[0012] The cooled photovoltaic silicon mud is prepared into block silicon mud;

[0013] Adding the block silicon mud into an induction furnace, heating the induction furnace to a preset temperature, so that the block silicon mud is melted and a liquid silicon molten pool is formed in the induction furnace;

[0014] The magnesium-containing raw material calcined white powder is sprayed into the liquid silicon molten pool, so that the magnesium-containing raw material calcined white powder reacts with silicon in the liquid silicon molten pool to generate metal magnesium vapor.

[0015] In addition, a preferred solution is that the heating and drying temperature of the photovoltaic silicon mud is 110°C-300°C.

[0016] In addition, a preferred solution is to crush and screen the cooled photovoltaic silicon mud to form block silicon mud with a particle size less than 50 mm.

[0017] In addition, a preferred solution is that a graphite crucible is provided in the reaction furnace, the block silicon mud is added into the graphite crucible, and the graphite crucible is heated to form the liquid silicon molten pool.

[0018] In addition, a preferred solution is that the preset temperature is 1420°C-1550°C.

[0019] In addition, a preferred solution is to spray the magnesium-containing raw material calcined white powder into the liquid silicon molten pool through a blowing feeding device.

[0020] In addition, a preferred solution is that the blowing feeding device includes a silo for storing the magnesium-containing raw material calcined white powder, a vacuum chamber connected to the silo, a spray gun arranged in the vacuum chamber, and a spray gun lifting mechanism for driving the spray gun to lift and lower, wherein:

[0021] Inserting the spray gun into the liquid silicon molten pool under the action of the spray gun lifting mechanism;

[0022] The argon gas in the vacuum chamber is used as a carrier to spray the magnesium-containing raw material calcined white powder into the liquid silicon molten pool, so that the magnesium-containing raw material calcined white powder and the liquid silicon undergo a reduction reaction to generate metallic magnesium vapor.

[0023] In addition, a preferred solution is that the vacuum chamber is connected to the reaction furnace, and the spray gun is extended into the reaction furnace under the action of the spray gun lifting mechanism and reaches the graphite crucible.

[0024] In addition, a preferred solution is that the time for the magnesium-containing raw material calcined white powder to react with the liquid silicon is less than or equal to 10 seconds.

[0025] In addition, a preferred solution is that the equation for the reduction reaction between the magnesium-containing raw material calcined white powder and the liquid silicon is:

[0026] MgO·CaO(s)+Si(l)→Mg(g)+2CaO·SiO2(l).

[0027] From the above technical scheme, it can be seen that the method for preparing magnesium metal using photovoltaic silicon mud provided by the present invention uses solid waste silicon mud from photovoltaic production as a reducing agent, and uses a spraying method to spray the magnesium-containing raw material calcined white powder into the molten pool formed by the solid waste silicon mud, thereby generating magnesium metal vapor. This preparation method can realize the large-scale secondary utilization of photovoltaic silicon mud valuable resources, thereby reducing land occupation and environmental pollution; and the silicon mud has a high silicon content, which can effectively promote the reduction reaction of magnesium and play a role in energy saving and consumption reduction.

[0028] In order to achieve the above and related purposes, one or more aspects of the present invention include the features that will be described in detail later. The following description and the accompanying drawings describe some exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] By referring to the following description in conjunction with the accompanying drawings, and with a more comprehensive understanding of the present invention, other objects and results of the present invention will become more apparent and easy to understand. In the accompanying drawings:

[0030] Figure 1 The present invention is a schematic flow chart of a method for preparing metallic magnesium using photovoltaic silicon mud according to an embodiment of the present invention.

[0031] The same reference numerals throughout the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0032] In the following description, for the purpose of illustration, in order to provide a comprehensive understanding of one or more embodiments, many specific details are set forth. However, it is apparent that these embodiments may also be implemented without these specific details. In other examples, for ease of describing one or more embodiments, known structures and devices are shown in the form of block diagrams.

[0033] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0034] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] In order to illustrate the method for preparing magnesium metal by using photovoltaic silicon mud provided by the present invention, Figure 1 The present invention shows a method for preparing metallic magnesium using photovoltaic silicon mud according to an embodiment of the present invention.

[0036] like Figure 1 As shown, the method for preparing metallic magnesium using photovoltaic silicon mud provided by the present invention comprises:

[0037] S1: heating and drying the photovoltaic silicon mud and cooling it to room temperature;

[0038] S2: preparing the cooled photovoltaic silicon mud into block silicon mud;

[0039] S3: adding the block silicon mud into an induction furnace, heating the induction furnace to a preset temperature, so that the block silicon mud is melted and a liquid silicon molten pool is formed in the induction furnace;

[0040] S4: Spraying the calcined white powder containing magnesium as raw material into the liquid silicon molten pool, so that the calcined white powder containing magnesium as raw material reacts with silicon in the liquid silicon molten pool to generate metallic magnesium vapor.

[0041] In an embodiment of the present invention, solid waste silicon mud from photovoltaic production is used as a reducing agent, and the magnesium-containing raw material calcined white powder is mixed with the reducing agent in combination with a spraying method, thereby causing a solid-liquid reduction reaction. The sprayed magnesium-containing raw material calcined white powder is completely reduced within 10 seconds, and its reaction rate and efficiency are much higher than solid-solid reactions.

[0042] In step S1, the heating and drying temperature of the photovoltaic silicon mud is 110°C-300°C.

[0043] In step S2, the cooled photovoltaic silicon mud is crushed and sieved to form block silicon mud with a particle size of less than 50 mm. In specific applications, a suitable particle size can be selected according to actual conditions, and is not limited to the above requirements.

[0044] In step S3, a graphite crucible is arranged in the reaction furnace, the block silicon mud is added into the graphite crucible, and the graphite crucible is heated to form the liquid silicon molten pool. The preset temperature is 1420°C-1550°C.

[0045] Specifically, the graphite crucible adopts an induction heating graphite crucible, and the graphite crucible is fixed on the reaction furnace through a bracket; a splash cover is arranged on the upper part of the graphite crucible, and a furnace cover is arranged on the reaction furnace, and the furnace cover is arranged above the splash cover. Openings are respectively arranged on the furnace cover and the splash cover, and the spray gun extends into the vacuum tank through the openings and finally reaches the graphite crucible.

[0046] In step S4, the magnesium-containing raw material calcined white powder is sprayed into the liquid silicon molten pool through a spray feeding device.

[0047] The spray feeding device comprises a silo for storing the magnesium-containing raw material calcined white powder, a vacuum chamber connected to the silo, a spray gun arranged in the vacuum chamber, and a spray gun lifting mechanism for driving the spray gun to rise and fall, wherein the spray gun is inserted into the liquid silicon molten pool under the action of the spray gun lifting mechanism; the magnesium-containing raw material calcined white powder is sprayed into the liquid silicon molten pool using the argon gas in the vacuum chamber as a carrier, so that the magnesium-containing raw material calcined white powder undergoes a reduction reaction with the liquid silicon to produce metallic magnesium vapor.

[0048] The vacuum chamber is connected to the reaction furnace, and the spray gun extends into the vacuum tank through the opening under the action of the spray gun lifting mechanism and finally reaches the graphite crucible. A high-temperature insulation layer and a refractory material layer are arranged on the periphery of the spray gun from the inside to the outside, wherein a blowpipe is arranged on the spray gun, and the blowpipe is made of wear-resistant and high-temperature resistant metal material; the refractory material layer is graphite or magnesium oxide wrapped in a boron nitride film.

[0049] The principle of the embodiment of the present invention is as follows: the spray gun is inserted into the melting pool of the graphite crucible through the furnace cover and the splash-proof cover, and the powder is sprayed into the graphite crucible from the top. The argon gas in the vacuum chamber is used as a carrier to spray the magnesium-containing raw material calcined white powder into the liquid silicon melting pool, so that the magnesium-containing raw material calcined white powder and the liquid silicon undergo a reduction reaction to produce metal magnesium vapor. The stirring force of the mixed fluid spraying the magnesium-containing raw material calcined white powder on the melting pool and the stirring force of the electromagnetic induction on the melting pool are coupled to form a flow field that suppresses splashing, which can not only prolong the residence time of the magnesium-containing raw material calcined white powder in the melt, increase the reaction rate, but also prevent the solution and slag liquid in the melting pool from splashing; a small amount of splashing can be blocked in the graphite crucible by the splash-proof cover.

[0050] The reaction time between the calcined white powder containing magnesium and the liquid silicon is less than or equal to 10 seconds. The reaction rate and efficiency of this solid-liquid reaction are much higher than the solid-solid reaction of the Pidgeon process. The equation for the reduction reaction between the calcined white powder containing magnesium and the liquid silicon is: MgO·CaO(s)+Si(l)→Mg(g)+2CaO·SiO2(l).

[0051] From the specific embodiments provided by the present invention, it can be seen that the method for preparing magnesium metal using photovoltaic silicon mud provided by the present invention uses solid waste silicon mud from photovoltaic production as a reducing agent, and combines the injection method to spray the magnesium-containing raw material calcined white powder into the molten pool formed by the solid waste silicon mud, thereby generating magnesium metal vapor. This preparation method can realize the large-scale secondary utilization of photovoltaic silicon mud valuable resources, thereby reducing land occupation and environmental pollution; due to the high silicon content in silicon mud, it can effectively promote the reduction reaction of magnesium, thereby playing a role in energy saving and consumption reduction.

[0052] The above descriptions are only optional embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for preparing metallic magnesium using photovoltaic silicon mud, characterized in that: include: Heat and dry the photovoltaic silicon mud and cool it to room temperature; The cooled photovoltaic silicon mud is prepared into block silicon mud; Adding the block silicon mud into an induction furnace, heating the induction furnace to a preset temperature, so that the block silicon mud is melted and a liquid silicon molten pool is formed in the induction furnace; The magnesium-containing raw material calcined white powder is sprayed into the liquid silicon molten pool, so that the magnesium-containing raw material calcined white powder reacts with silicon in the liquid silicon molten pool to generate metal magnesium vapor.

2. The method for preparing metallic magnesium using photovoltaic silicon mud according to claim 1, characterized in that: The heating and drying temperature of the photovoltaic silicon mud is 110°C-300°C.

3. The method for preparing metallic magnesium using photovoltaic silicon mud according to claim 1, characterized in that: The cooled photovoltaic silicon mud is crushed and screened to form block silicon mud with a particle size less than 50 mm.

4. The method for preparing metallic magnesium using photovoltaic silicon mud according to claim 1, characterized in that: A graphite crucible is arranged in the reaction furnace, the block silicon mud is added into the graphite crucible, and the graphite crucible is heated to form the liquid silicon molten pool.

5. The method for preparing metallic magnesium using photovoltaic silicon mud according to claim 1, characterized in that: The preset temperature is 1420°C-1550°C.

6. The method for preparing metallic magnesium using photovoltaic silicon mud according to claim 1, characterized in that: The magnesium-containing raw material calcined white powder is sprayed into the liquid silicon molten pool through a blowing feeding device.

7. The method for preparing metallic magnesium using photovoltaic silicon mud according to claim 6, characterized in that: The spray feeding device includes a silo for storing the magnesium-containing raw material calcined white powder, a vacuum chamber connected to the silo, a spray gun arranged in the vacuum chamber, and a spray gun lifting mechanism for driving the spray gun to rise and fall, wherein: Inserting the spray gun into the liquid silicon molten pool under the action of the spray gun lifting mechanism; The argon gas in the vacuum chamber is used as a carrier to spray the magnesium-containing raw material calcined white powder into the liquid silicon molten pool, so that the magnesium-containing raw material calcined white powder and the liquid silicon undergo a reduction reaction to generate metallic magnesium vapor.

8. The method for preparing metallic magnesium using photovoltaic silicon mud according to claim 7, characterized in that: The vacuum chamber is connected to the reaction furnace, and the spray gun is extended into the reaction furnace under the action of the spray gun lifting mechanism and reaches the graphite crucible.

9. The method for preparing metallic magnesium using photovoltaic silicon mud according to claim 7, characterized in that: The time for the magnesium-containing raw material calcined white powder to react with the liquid silicon is less than or equal to 10 seconds.

10. The method for preparing metallic magnesium using photovoltaic silicon mud according to claim 7, characterized in that: The equation for the reduction reaction between the magnesium-containing raw material calcined white powder and the liquid silicon is: MgO·CaO(s)+Si(l)→Mg(g)+2CaO·SiO2(l).

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