Graphite is one of the minerals of the elemental carbon (C) crystal. The hexagonal crystal is a plate-like crystal. The crystal lattice is hexagonal and parallel to the (0001) cleavage. Lead gray, opaque, metallic gloss, hardness with anisotropy, a direction perpendicular to the surface treatment solution is 3-5, the direction parallel to the cleavage plane 1-2, a specific gravity of 2.2-2.37, 1.5-1.8 bulk density.
Graphite is a special non-metallic material that combines the excellent properties of metals. The properties that graphite can use are: coating, lubricity, high temperature resistance, corrosion resistance, plasticity, thermal conductivity, electrical conductivity, chemical stability and Special heat resistance properties at high temperatures.
The melting point of graphite is 3850 ± 50 °C. The burning of ultra-high temperature arc, in several kinds of high temperature resistant materials, according to the weight loss after burning, the graphite is the smallest. Its thermal expansion coefficient is very small, not only high temperature resistance, but also low temperature resistance. At high temperature, it does not tend to soften, but the strength is increased.
First, the use of graphite
Casting: A coating made of graphite as a casting mold. It utilizes the coatability, fire resistance, lubricity and chemical stability of graphite. Graphite for casting accounts for about one-third of the total graphite.
Metallurgical industry: graphite bricks made from tantalum and high-temperature electric furnaces are used to smelt precious metal materials such as non-ferrous metals and alloys. The use of graphite is also about one-third of the total amount. At present, China used (metallurgy) flux in the steel industry.
Mechanical industry: Graphite is often used as a lubricant for ship axles, locomotives and axles. Solid lubricants made of graphite can be used for various mechanical lubrication, and graphite can be used as an emulsifier for die forging and hammer forging lubricants.
Textile and food industry: The use of graphite to make solid lubricants, graphite and metal together to make oil-free bearings.
Electric industry: for a small electrode to produce graphite electrodes, carbon tubes, arc, carbon rod, welding of carbon, mercury rectifier positive electrode, telephone parts, tungsten and molybdenum wire pulling lubricant and high resistance, and the like.
Chemical industry: Because graphite has abnormal chemical stability, the use of graphite pipes can ensure the normal progress of chemical reactions and meet the needs of manufacturing high-purity chemicals. Graphite powder made of graphite can be used as a chemical catalyst for chemical fertilizer manufacturing. Vessels and equipment made of graphite fibers and plastics are resistant to a variety of corrosive gases and liquids. Graphite can also be used as a filler for rubber and plastic.
Light industry: graphite is used as a polishing agent and rust inhibitor for glass and paper industry, as a raw material for black paint and as a filler for ink.
Atomic energy defense industry: using high-purity and high-density graphite as a sub-decelerator in an atomic energy reactor, an anti-atomic radiation enclosure, a rocket engine tail nozzle throat liner, a radio connection signal for use on an artificial satellite, and a conductive structural material. Graphite is also used in gunpowder, submarine, and aircraft manufacturing.
In addition, required for producing a graphite pencil; in the chimney can be coated as a preservative; synthetic diamond required to confer a graphite material.
In the past, the industrial use of small, low-carbon graphite, is now expanding its range of use, such as the use of low-carbon graphite can be used as fuel aspects of small ovens, industrial boilers, brick, civil honeycomb coal.
Second, graphite ore composition and ore type
The composition of graphite is carbon (C), but there are often impurities such as quartz , pyrite, pyrrhotite, and carbonate in the ore, and sometimes water, asphalt , carbon dioxide, and the like.
According to the crystal form of graphite, graphite ore is generally divided into two categories:
1. Crystalline (or scale) graphite: scaly and massive (or dense crystalline) graphite with a crystal diameter greater than 1 micron. The grade of ore is generally poor, and it can be used in the industry by mineral processing . But its quality is good and its use is wide.
2, cryptocrystalline (or amorphous, earthy) graphite: crystal diameter less than 1 micron, under the microscope is also difficult to see its crystalline dense graphite aggregate. Due to the poor selectivity of the ore, the industry has higher requirements on the ore grade for direct grinding into powder. Its industrial performance is worse than crystalline graphite.
According to the carbon content, particle size and impurity content of graphite, it is commercially divided into high purity, high carbon, medium carbon, low carbon and other graphite.
Third, general industrial requirements for graphite
(a) crystalline (scaled) graphite ore
1. Weathered ore
Boundary grade: fixed carbon 2-3%, minimum industrial grade: fixed carbon 2.5-3.5%
Available thickness: ≥2—4 meters, thickness of stone removal: ≥1—4 meters,
Stripping ratio: no more than 3 - 4:1
2. Native ore
Boundary grade: fixed carbon 2.5-3.5%, minimum industrial grade: fixed carbon 3-8%
Available thickness: ≥2—4 meters, stone removal thickness: ≥1—4 meters
Stripping ratio: no more than 3 - 4:1
Note: Due to the different degree of crystalline (scaly) graphite, its industrial use and economic value vary greatly. The industrial index of the specific mining area that provides the basis for mine construction design should be based on the level of graphite (+100 mesh). To develop border grades and industrial grades. When the content of the normal graphite is high, the grade requirement can be lowered; otherwise, it should be improved. Generally, the content of the primary eye graphite is required to be about 40-60%. (The main target refers to the ore, the concentrate obtained by ore dressing after screening, +100 mesh graphite, the percentage in the concentrate). Specific mining areas should also determine industrial requirements through technical and economic evaluation.
(2) cryptocrystalline (earth) graphite ore
Boundary grade: fixed carbon ≥ 55%, minimum industrial grade: fixed carbon ≥ 65%
Available thickness: ≥0.7-1.4 meters, stone removal thickness: ≥1~3 meters
Note: The above industrial indicators are summarized based on the current production mines (crystalline graphite is open-pit mining and cryptocrystalline graphite is used for tunnel mining). If the mining methods are different, the indicators should be formulated according to the mining conditions.
2 cryptocrystalline graphite grade: first grade contains fixed carbon ≥ 80%; second grade contains fixed carbon ≥ 65%
3 Graphite containing sulfur and high iron content will reduce the degree of refractoriness and chemical stability, should be determined.
4 When conducting a general evaluation of the new crystalline graphite ore, a laboratory beneficiation test is required to determine whether the concentrate contains more than 85% of the fixed carbon, and a piece measurement is required to determine the value of further work of the deposit;
5 The hardness of the ore will directly affect the beneficiation production process, production cost, product and economic value. Weathering ore and primary ore should be divided during exploration and evaluated separately;
6 cryptocrystalline graphite, in some countries, such as a Czech deposit, the original ore grade is only 32-35% also mining (but need to be ore, after flotation, the concentrate grade can reach 72%, the recovery rate is 67%). Only 25% of a mineral grade in the Soviet Union is used for mining because the deposit is accompanied by a large amount of refractory clay that can be used in the foundry industry.
Fourth, the deposit example
(1) Graphite mine in Jiaodong area
1 large scale: the graphite piece diameter in the ore is 1.0-2.0 mm, and the graphite piece >100 mesh in the concentrate accounts for more than 30%;
2 medium scales: the graphite piece diameter in the ore is 0.5-1.0 mm, and the graphite piece >100 mesh in the concentrate accounts for 10-30% or more;
3 small scales: the graphite piece diameter in the ore is <0.5 mm, and the graphite piece >100 mesh in the concentrate accounts for less than 10%;
4 Large-scale mines have a high degree of mechanization. Under the premise of counterpart exploration, the thickness and the thickness of the stone can be removed by 2-4 meters, such as Nanshu Mine. If it is a small mine, it can only be used for mining in township and village enterprises, then the thickness of the harvestable stone and the thickness of the stone should be 1-2 meters. Regardless of the size of the deposit, it can be considered 1-2 meters in the census evaluation stage.
(2) Heilongjiang Jixi Liumao Graphite Mine
Boundary grade: fixed carbon 3%, minimum industrial grade: fixed carbon 5% (I grade ≥ 10%, grade II ≥ 5%)
Available thickness: ≥ 2 meters, stone removal thickness: ≥ 2 meters
(3) Hunan Lutang cryptocrystalline graphite ore
Boundary grade: fixed carbon ≥ 65%, industrial grade: fixed carbon ≥ 70%
Minimum recoverable thickness: 0.5 m, stone removal thickness: 15% of the thickness of the ore layer
V. Comprehensive evaluation
The cryptocrystalline graphite deposits produced in the coal system may be accompanied by porcelain clay and rare earth element strontium . The regional metamorphic crystallization stone deposits are often accompanied by uranium , vanadium , titanium , gold, silver, pyrite, rare earth elements, and phosphate ash. stone, high aluminum mineral raw materials, to be noted that the comprehensive evaluation, comprehensive recycling.
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