A green smelting system and method of magnesium metal

Abstract

The application discloses a kind of green smelting system and method of metal magnesium, belong to metal smelting technical field.The application includes biomass gasification system and smelting system;The biomass gasification system includes the biomass gasification furnace, waste heat recovery device and dust collector arranged in sequence;The smelting system includes the rotary kiln, briquetting machine and reduction furnace arranged in sequence;Wherein, the steam generated by waste heat recovery device and the CO2 generated in reduction furnace return to biomass gasification furnace;Clean coal gas separated by dust collector is divided into two ways, respectively into rotary kiln and reduction furnace;Fly ash separated by dust collector enters briquetting machine;Calcium slag generated in reduction furnace returns to biomass gasification furnace.The application can perfectly fit the advantages of each other by coupling of biomass gasification system and smelting system, compared with traditional metal magnesium smelting industry, not only energy consumption is greatly reduced, and green smelting of metal magnesium is realized.

Description

Technical Field

[0001] This invention belongs to the field of metal smelting technology, and more specifically, relates to a green smelting system and method for magnesium. Background Technology

[0002] The traditional magnesium smelting process commonly uses the Pidgeon process, which involves calcining dolomite at high temperatures to produce magnesium oxide (calcined white magnesium oxide). This calcined white magnesium oxide is then granulated by adding ferrosilicon and placed in a reduction tank. The tank is heated to 1200°C and held at this temperature for a period of time, reducing the magnesium oxide to crude magnesium. Currently, the fuels used in the magnesium oxide reduction process are mainly coal, natural gas, and some semi-coke tail gas. However, natural gas is expensive, resulting in high magnesium smelting costs. Furthermore, the process generates waste slag, which, if not properly treated, can have adverse effects on the environment. Therefore, designing an energy-saving and environmentally friendly magnesium smelting method is of great significance for the clean and efficient development of the entire magnesium industry.

[0003] A search revealed a patent, CN119750925A, which discloses a method and system for the combined production of biomass pyrolysis and magnesite calcination. This application utilizes naturally renewable biomass fuel to partially or completely replace traditional fossil fuels used in the magnesite industry, saving energy and reducing production costs. However, this application does not effectively utilize the waste residue generated during the magnesite smelting process; therefore, there is still room for optimization. Summary of the Invention

[0004] 1. The problem to be solved

[0005] In view of at least some of the problems existing in the prior art, the present invention proposes a green magnesium smelting system and method, the purpose of which is to solve the problems of high cost and easy environmental pollution caused by the existing traditional magnesium smelting process.

[0006] 2. Technical Solution

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a green smelting method for metallic magnesium, comprising the following steps:

[0009] S1. After pretreatment, the biomass raw material enters the biomass gasifier for gasification reaction to generate coal gas and slag.

[0010] S2. After primary separation, the coal gas yields crude coal gas and primary fly ash; the primary fly ash is returned to the biomass gasification furnace for further reaction.

[0011] S3. After heat exchange, the crude coal gas is converted into steam, and part of the steam is used as a gasifying agent in the biomass gasification reaction.

[0012] S4. After heat exchange, the crude coal gas is separated twice to obtain clean coal gas and secondary fly ash.

[0013] S5. Secondary fly ash and calcined dolomite are compressed into briquettes and then subjected to a reduction reaction to generate magnesium crystals; wherein, the clean coal gas in step S3 is used as fuel for the calcination and reduction reactions.

[0014] The calcium slag produced during the reduction reaction is used as a bed material in the biomass gasification reaction. This calcium slag bed material can capture potassium in biomass and absorb CO2 in coal gas at high temperatures.

[0015] The carbon dioxide produced during the reduction reaction is used as a gasifying agent in the biomass gasification reaction.

[0016] In some embodiments, in step S3, the crude gas is heated before heat exchange to fully crack the tar in the crude gas.

[0017] In some embodiments, the temperature in step S3 is 1000-1300°C.

[0018] In some embodiments, in step S2, the separation particle size of the first separation is 50 μm to 100 μm; in step S4, the separation particle size of the second separation is controlled between 10 μm and 50 μm.

[0019] In some embodiments, in step S1, the temperature of the gasification reaction is 600–800°C; and the calorific value of the biomass feedstock is greater than 2500 kcal / kg.

[0020] In some embodiments, the biomass raw material is one or more of plant straw, wood, rice husks, peanut shells, corn cobs, seaweed, bagasse, manure, or organic waste.

[0021] The present invention provides a green smelting system for magnesium metal, comprising,

[0022] A biomass gasification system, comprising a biomass gasifier, a waste heat recovery unit, and a dust collector arranged sequentially.

[0023] The smelting system includes a rotary kiln, a briquetting mill, and a reduction furnace arranged sequentially; wherein...

[0024] The steam generated by the waste heat recovery unit and the CO2 generated in the reduction furnace are returned to the biomass gasification furnace;

[0025] The clean coal gas separated by the dust collector is divided into two paths, which enter the rotary kiln and the reduction furnace respectively; the fly ash separated by the dust collector enters the briquetting machine.

[0026] The calcium slag produced in the reduction furnace is returned to the biomass gasification furnace.

[0027] In some embodiments, a heating furnace is provided between the biomass gasifier and the waste heat recovery unit to heat the crude gas.

[0028] In some embodiments, a cyclone separator is provided between the heating furnace and the biomass gasification furnace, and the fly ash separated by the cyclone separator is returned to the biomass gasification furnace.

[0029] In some embodiments, the inlet temperature of the waste heat recovery unit is 500–700°C, and the outlet temperature is 200–400°C; the inlet temperature of the dust collector is 200–400°C, and the filtration velocity is 0.4–0.6 m / s.

[0030] 3. Beneficial effects

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] This invention utilizes high-calorific-value coal gas generated from the pyrolysis of biomass raw materials, which can replace traditional high-priced fuels and provide heat for the dolomite calcination and reduction process in the magnesium smelting system. This effectively reduces the dependence of magnesium smelting on traditional energy sources such as coal and natural gas, improves energy utilization efficiency, and reduces production costs.

[0033] Meanwhile, the calcium slag produced during the magnesium smelting process is used as bed material in the biomass gasification system and is ultimately discharged as plant fertilizer, avoiding environmental pollution from waste residue and achieving a green cycle throughout the entire production process, which has good environmental benefits.

[0034] In addition, fly ash generated during biomass gasification is usually considered waste in traditional processes. However, in this invention, fly ash directly participates in the reduction process of magnesium smelting, realizing the resource utilization of waste and reducing waste emissions and treatment costs. Attached Figure Description

[0035] Figure 1 This is a simplified structural diagram of a green magnesium smelting system according to the present invention. Detailed Implementation

[0036] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings.

[0037] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0038] The present invention will be further described below with reference to specific embodiments.

[0039] like Figure 1 As shown in this embodiment, a green magnesium smelting system includes a biomass gasification system and a smelting system. The biomass gasification system includes a biomass gasifier, a waste heat recovery unit, and a dust collector arranged sequentially. The biomass feedstock, after pretreatment, enters the biomass gasifier to produce coal gas and slag. The coal gas then enters the waste heat recovery system to recover heat before entering the dust removal system. The separated fly ash and coal gas then enter the smelting system respectively.

[0040] The smelting system includes a rotary kiln, a briquetting machine, and a reduction furnace arranged sequentially. Dolomite enters the rotary kiln and is calcined using the gas generated from the biomass gasification process. After calcination, it is briquetized with high-carbon fly ash (carbon content >60%) produced by the biomass gasification system and then enters the reduction furnace for a reduction reaction to produce magnesium crystals. The calcium slag produced during the magnesium smelting process serves as the bed material for the biomass gasification system, which helps to fix potassium in the biomass ash. In addition, the biomass gas can be used as energy for the reduction process in the reduction furnace.

[0041] This embodiment presents a green magnesium smelting system where the gas produced by biomass gasification can be used as fuel for dolomite calcination and magnesium reduction. Simultaneously, the calcium slag produced in the reduction furnace is returned to the biomass gasifier as bed material. At high temperatures, the calcium slag bed material can capture potassium from the biomass and absorb CO2 from the gas, which helps improve the gas composition and increase its calorific value. Furthermore, the final discharged calcium slag can be used as a soil conditioner, avoiding environmental pollution from waste residue and achieving a green cycle throughout the entire production process, resulting in significant environmental benefits.

[0042] In addition, in this embodiment, the fly ash separated by the dust collector enters the briquetting machine to briquette the calcined dolomite. At this time, the fly ash particles can fill the pores of the dolomite briquetting, improve the formability and permeability of the material, and facilitate the diffusion of heat and gas in the reduction reaction. At the same time, the SiO2 in the fly ash can react with CaO to generate low-melting-point silicates, reduce the melting temperature of the reaction system, and help promote the reduction efficiency of MgO.

[0043] In some implementations, a heating furnace is provided between the biomass gasifier and the waste heat recovery unit to heat the crude gas, thereby fully cracking the tar in the crude gas and preventing subsequent tar precipitation from clogging and damaging the equipment.

[0044] Meanwhile, a cyclone separator is installed between the heating furnace and the biomass gasification furnace. The fly ash separated by the cyclone separator is returned to the biomass gasification furnace to continue the reaction.

[0045] This embodiment also provides a green smelting method for metallic magnesium, including the following steps:

[0046] S1. Biomass feedstock reacts with a gasifying agent in a biomass fluidized bed gasifier to produce coal gas and slag; wherein, biomass is one or more of the following: plant straw, wood, rice husks, peanut shells, corn cobs, seaweed, bagasse, manure, or organic waste. The gasifying agent is a mixture of water vapor, carbon dioxide, and air or oxygen.

[0047] Preferably, the calorific value of the biomass feedstock is greater than 2500 kcal / kg; and the reaction temperature in the gasifier is 600-800℃, for example, 630℃, 680℃, 760℃, etc.

[0048] S2. The gas is sent to the heating furnace via a cyclone separator for secondary heating. The primary fly ash separated by the cyclone separator is returned to the gasifier to continue the reaction, thereby improving the carbon conversion rate of the system.

[0049] The cyclone separator separates particles with a particle size of 50μm to 100μm, such as 60μm, 70μm, 80μm, and 90μm. The heating furnace has a temperature of 1000 to 1300℃, such as 1140℃, 1220℃, and 1280℃.

[0050] S3. After the crude coal gas is heated by the waste heat recovery unit, it is converted into steam. Some of the steam is used as a gasifying agent in the biomass gasification reaction. The inlet temperature of the waste heat recovery unit is 500-700℃, for example, 530℃, 610℃, 690℃, etc.; the outlet temperature is 200-400℃, for example, 215℃, 270℃, 330℃, 380℃, etc.

[0051] S4. After heat exchange, the coal gas is separated by a dust collector to obtain clean coal gas and secondary fly ash. The separated secondary fly ash is granulated with calcined dolomite and then undergoes a reduction reaction to generate magnesium crystals. The clean coal gas provides energy for the dolomite calcination and reduction furnace.

[0052] Preferably, the inlet temperature of the dust collector is 200–400℃, for example, 230℃, 320℃, 336℃, etc.; the filtration velocity is 0.4–0.6 m / s, for example, 0.48 m / s, 0.53 m / s, etc.; and the separation particle size of the dust collector is 10 μm–50 μm, for example, 18 μm, 32 μm, 44 μm, etc.

[0053] Meanwhile, the calcium slag produced during the reduction reaction is returned to the gasifier as bed material; the carbon dioxide produced during the reduction reaction is used as a gasifying agent for the biomass gasification reaction.

[0054] This embodiment of a green magnesium smelting method has the following advantages compared to existing technologies.

[0055] High-efficiency energy utilization: The high-calorific-value coal gas produced by the pyrolysis of biomass raw materials can not only be used directly as the power source for system operation, but also replace traditional high-priced fuels, providing heat for the dolomite calcination and reduction processes in the magnesium smelting system. This effectively reduces the dependence of magnesium smelting on traditional energy sources such as coal and natural gas, improves energy utilization efficiency, and reduces production costs. Waste resource utilization: The fly ash produced in the biomass gasification process is usually considered waste in traditional processes. However, in this system, the fly ash directly participates in the reduction process of magnesium smelting, realizing the resource utilization of waste, reducing waste emissions and treatment costs, and simplifying the magnesium smelting process.

[0056] Environmentally friendly: The entire system achieves CO2 recovery and utilization through the recycling of materials and energy, reducing carbon emissions. The calcium slag produced in the magnesium smelting process is used as the bed material of the biomass gasification system and is ultimately discharged as plant fertilizer, avoiding pollution of the environment by waste residue and realizing a green cycle throughout the entire production process, which has good environmental benefits.

[0057] In summary, this embodiment of a green magnesium smelting method perfectly combines the advantages of both systems through coupling. Compared to the traditional magnesium smelting industry, it not only significantly reduces energy consumption but also achieves clean and efficient development of the green magnesium smelting system industry.

[0058] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A green smelting method for metallic magnesium, characterized in that: Includes the following steps, S1. After pretreatment, the biomass raw material enters the biomass gasifier for gasification reaction to generate coal gas and slag. S2. After primary separation, the coal gas yields crude coal gas and primary fly ash; the primary fly ash is returned to the biomass gasification furnace for further reaction. S3. After heat exchange, the crude coal gas is converted into steam, and part of the steam is used as a gasifying agent in the biomass gasification reaction. S4. After heat exchange, the crude coal gas is separated twice to obtain clean coal gas and secondary fly ash. S5. Secondary fly ash and calcined dolomite are compressed into briquettes and then subjected to a reduction reaction to generate magnesium crystals; wherein, the clean coal gas in step S3 is used as fuel for the calcination and reduction reactions. The calcium slag produced during the reduction reaction is used as a bed material in the biomass gasification reaction. This calcium slag bed material can capture potassium in biomass and absorb CO2 in coal gas at high temperatures. The carbon dioxide produced during the reduction reaction is used as a gasifying agent in the biomass gasification reaction.

2. The green smelting method for metallic magnesium according to claim 1, characterized in that: In step S3, the crude gas is heated before heat exchange to fully crack the tar in the crude gas.

3. The green smelting method for metallic magnesium according to claim 2, characterized in that: In step S3, the temperature is raised to 1000~1300℃.

4. The green smelting method for metallic magnesium according to claim 1, characterized in that: In step S2, the separation particle size of the first separation is 50μm~100μm; in step S4, the separation particle size of the second separation is controlled between 10μm~50μm.

5. The green smelting method for metallic magnesium according to claim 4, characterized in that: In step S1, the temperature of the gasification reaction is 600~800℃; the calorific value of the biomass raw material is greater than 2500kcal / kg.

6. The green smelting method for metallic magnesium according to claim 5, characterized in that: The biomass raw materials mentioned are one or more of the following: plant straw, wood, rice husks, peanut shells, corn cobs, seaweed, bagasse, and manure.

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