Graphite beneficiation method include flotation, electrostatic separation, gravity separation, etc. Flotation is the most widely used process. Graphite mineral processing are mainly suitable for all kinds of graphite with different crystal habit and graphite accompany with mica, etc silicate minerals or pyrite. Beneficiation method: flotation, electrostatic separation, gravity separation, etc. Flotation is the most widely used process.
About graphite ore:
Graphite ore include amorphous graphite and flaky graphite. Amorphous graphite also call cryptocrystalline graphite. This ore have small graphite crystal, surface is earthy and industrial performance is not good. But this graphite ore have high grade, general 60-80%. But its flotability is bad. After flotation, the grade have no remarkable increase. Thus, if the grade is lower than 65%, shall not be mined, the grade between 65-80%, selection and then use. The feature of Flaky graphite is the graphite present as flaky or foliated, raw ore grade is not high, general 3-5%, can't
Exceed 20-25%. This graphite ore have good flotability and grade can up to 90% after flotation. So, raw ore grade with 2-3% can be mined. Flaky graphite have good performance and can be used to make advanced carbon product. So, we can't only consider the grade for different graphite, but also the type, then decide whether use the flotation process.
Flaky graphite have good flotability, so mostly use flotation to select. In China, generally use the kerosene or diesel as collector, 2# oil or new flotation oil as foaming agent. After many years production practice, 4# oil are considered as ideal foaming agent for graphite.
Generally, Cryptocrystalline graphite associate with mica etc silicate minerals. When flotation, can use starch, dextrin, organic glue, cellulose, etc agent to control the silicate minerals, for example, if the pyrite content is high, add lime and oxide.
Flotation is the most common method used in graphite processing plants. Basically, all the flake graphite processing plants adopt flotation to separate the graphite. In general, the beneficiation process includes: one roughing, one scavenging and seven to eleven cleaning, which can obtain the graphite concentrate with a fixed carbon content of 90%-97%. In order to protect the flake, the regrind of concentrate generally adopts sand mill. Due to its strong hydrophobicity and natural floatability, flake graphite generally uses kerosene or diesel as a collector, No. 2 oil or No. 4 oil as a foaming agent for graphite flotation. Sometimes, lime or sodium carbonate is added to adjust the pulp PH at about 8-9. As for silicate minerals containing clay, quartz, mica and feldspar, it’s necessary to add the silicate, dextrin, starch and cellulose to inhibit gangue minerals and disperse the pulp
In order to continue to increase the fixed carbon content of graphite, the chemical beneficiation method is adopted to purify, such as high temperature alkali fusion acid leaching method, HF acid leaching and mixed acid leaching, chlorination melting and so on., which can produce the high purity graphite with the carbon content over 99.99%.
The gravity separation is mainly used to preprocess the graphite ores, pick out the heavy minerals, discard tailings in advance. After the preliminary enrichment of graphite, flotation is used to further increase the fixed carbon content of graphite. When large numbers of pyrite, limonite, garnet, rutile, tremolite, diopside and other minerals with large proportion are contained in minerals, it’s necessary to use the gravity separation to reach the preliminary enrichment and then obtain the coarse graphite concentrate. The coarse concentrate is further enriched by flotation. Therefore, the gravity separation is only used to preprocess graphite ore and in most cases, it’s combined with fotation in actual production. At present, it’s rarely used.
The raw ore grade of cryptocrystalline is generally high, with carbon content of 60-80%, and the product can be obtained after hand separation, crushing and milling process.
In recent years, the flotation has also been adopted in cryptocrystalline graphite ore to increase the fixed carbon content. The separation of cryptocrystalline graphite flotation is more difficult and flotation is usually used to preliminarily enrich the graphite. The concentrate and tailings obtained by flotation are sold as crystals with different quality or the concentrate after flotation is chemically purified.
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