Innovative flake graphite technology to promote progress in materials science

(Innovative flake graphite technology to promote progress in materials science)

Graphite is a carbonaceous non-metallic mineral and a high-performance crystalline carbon material. It has extraodinary thermal conductivity, هدایت الکتریکی, high and low temperature resistance, radiation resistance, مقاومت در برابر خوردگی, self-lubrication and other properties. It is widely used in metallurgy, ماشین آلات, اتومبیل ها, and atomic energy. , دارو, military industry, باتری ها, aerospace and other fields, it has actually become one of the crucial raw materials for materials in high, brand-new and advanced scientific and technological fields in the 21st century. در سالهای اخیر, many developed countries have listed graphite as a strategic mineral for protection. In order to improve resource supply capabilities and development and utilization levels.

 

Category of graphite

The process characteristics of graphite mainly depend on its crystal form. According to the different crystal forms, natural graphite can be industrially divided into three categories: dense crystalline graphite (lumpy graphite), cryptocrystalline graphite (earth graphite) and flake graphite. .

Flake graphite is relatively rare in nature and is the most valuable graphite ore. It has the best crystallization state, with a particle diameter greater than 0.1mm. The crystals are visible to the naked eye. The specific surface area ranges from 0.1 to 1m2/g, and it has a dense block structure. The fixed carbon content is 60% به 65%, sometimes as high as 80% به 90%, اما انعطاف پذیری و صافی آن به خوبی گرافیت پولکی نیست.

Earthy graphite has the worst crystallization state, with a crystal diameter less than 1 μm and a specific surface area mainly distributed between 1 و 5 m2/g. It is an aggregate of microcrystalline graphite. The complete crystal form can only be seen under an electron microscope. The surface is earthy. شکل, lack of luster and lubricity, poor floatability, but higher grade, fixed carbon content is generally 60% به 80%, and a few can reach more than 90%.

Flake graphite is one of the most floatable ores in nature. After multiple grinding and multiple separations, high-grade graphite concentrate can be obtained. قابلیت شناور بودن, روانکاری, and plasticity of this type of ore are superior to Other types of graphite, so its industrial application value is greatest.

 

Overview of flake graphite

Flake graphite is formed by high-pressure metamorphism. It is generally blue-gray in color and becomes yellow-brown or off-white when weathered. It is mostly found in gneiss, شیست, crystalline limestone and skarn. The symbiotic minerals are complex and the main component is flake crystalline carbon, accompanied by There are impurity minerals such as feldspar, کوارتز, biotite, پیریت, pyrrhotite, and rutile.

The graphite in the ore is in the form of crystalline scales or blades, black or steel gray, and is mainly found between feldspar, quartz or diopside and tremolite particles. It has an obvious directional arrangement and is consistent with the layer direction. Most of the flake graphite is natural crystalline graphite, which has a layered structure. It is shaped like fish scales, belongs to the hexagonal crystal system, and has a good crystallization state. The particle size diameter is 0.05~1.5μm, the flake thickness is 0.02~0.05mm, and the largest flake can reach 4 ~5mm, graphite carbon content is generally around 2% ~ 5% یا 10% ~ 25%.

Classification and application of flake graphite

According to the total graphitic carbon content (Total Graphitic Carbon, TGC), flake graphite is divided into high purity graphite (TGC ≥ 99.9%), گرافیت کربن بالا (TGC 94.0% ~ 99.9%), medium carbon graphite (TGC 80.0% ~ 94.0% ) and low carbon graphite (TGC ≤ 50.0% ~ 80.0%) four categories. According to the size of the scales, flake graphite is divided into large flake graphite (>147متر) and small flake graphite (<147متر).

 

Flake graphite application areasFlake graphite resource reserves and production

Natural flake graphite deposits are the main type of graphite deposits in the world. They are mainly found in China and Sri Lanka in Asia, Ukraine in Europe, Mozambique, Madagascar, Tanzania in Africa, and Brazil in South America. Mozambique, Tanzania, Madagascar and other countries are rich in them ( فوق العاده) large flake graphite has high industrial value.

The "MINERAL COMMODITY SUMMARIES 2021" released by the United States Geological Survey (USGS) shows that as of the end of 2020, the world's proven natural flake graphite reserves were 230 میلیون تن, of which China, Brazil, Madagascar, and Mozambique accounted for more than 84% .

در حال حاضر, the main producing countries of natural flake graphite are China, Brazil and India. From 2011 به 2016, the global production of natural flake graphite remained stable at 1.1 به 1.2 million t/a. Affected by a series of factors, it plummeted to 897,000 tons in 2017; slowly rose to 930,000 tons in 2018; and recovered to 1.1 million tons in 2019 due to the increase in the supply of natural flake graphite in Mozambique. در 2020, China's flake graphite output was 650,000 تن, accounting for approximately 59% of the world's total output, making it the world's largest producer; Mozambique's flake graphite output was 120,000 تن, حسابداری برای 11% of the world's total output, making it the second largest producer. Producing countries.

 Ore dressing and purification of flake graphite

The purity of graphite determines its use. As the application scope of graphite continues to expand, the requirements for its purity are becoming higher and higher. Experimental research and industrial practice show that different purification methods have different advantages and markets

Flotation method: Flake graphite has good natural floatability. After flotation, enrichment and purification, a concentrate product with a fixed carbon content of more than 90% can be obtained. The flotation process is unique. It must not only increase the fixed carbon content of the concentrate, but also increase the yield of large scales. با این حال, the fixed carbon content of the raw ore is generally not high, در مورد 3% به 10%. The process mineral processing ratio is large and rich. The degree of concentration is high and multi-stage grinding is required to achieve gradual dissociation from gangue minerals. معمولا, the stage grinding stage flotation process is adopted. Exploring how to protect large flakes in flake graphite flotation, rationally optimizing the grinding process and flotation process, and improving large flake yield and concentrate quality are the mainstream development trends of flake graphite beneficiation.

 

Alkaline-acid method: It is a purification method for flake graphite that is currently widely used and has relatively ideal purification effects. با این حال, this process has high energy consumption, complex processes, and large water consumption.

Hydrofluoric acid method: The effect of purifying graphite is remarkable, but hydrofluoric acid is highly toxic and seriously pollutes the environment, so its use is restricted.

Chlorination roasting method: The effect of purifying graphite is limited, and chlorine gas is toxic and harmful to health and environmental protection, and requires high equipment.

High-temperature method: It is an effective means to achieve ultra-pure graphite production, but this method has extremely high requirements for raw materials and equipment.

Global flake graphite trade pattern

در حال حاضر, چین, Brazil, Mozambique, Madagascar and other countries are the main exporters of natural flake graphite in the world, and China, ایالات متحده, India, ژاپن, آلمان, Canada and other countries are the main importers. China is both a major exporter and a major importer of natural flake graphite. It is one of the world's largest producers and consumers of graphite and plays an important role in the global graphite trade market.

China mainly exports rough-processed, low-value-added graphite products such as raw flake graphite ore and low-grade flake graphite, while developed countries such as the United States, ژاپن, and Germany mainly export deep-processed, high-value-added graphite such as fluorinated graphite, expanded graphite, and high-purity graphite. graphite products.

 

تامین کننده

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(Innovative flake graphite technology to promote progress in materials science)