Feldspar is an aluminosilicate mineral of alkali metals such as potassium, sodium, calcium, barium, etc. Pure feldspar is rarely found in nature, and even minerals known as "potassium feldspar" may co-exist or be mixed with some sodium feldspar. According to the type of deposit, feldspar can be divided into pegmatite feldspar, white granite feldspar, granite feldspar and feldspar placer.
Because of the different deposits and ore characteristics, the feldspar mining processes are quite different with each other. Common feldspar mining processes includ hand sorting, desliming, magnetic separation, gravity separation, flotation and combined processing technology, in order to separate quartz, iron, mica and other minerals.
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Commonly, pegmatite feldspar has good quality feldspar ores, which has simple mineral constitute. So the mineral processing technology is rather simple than other minerals. This kind of feldspar mining process includes selecting, crushing, grinding, and strong magnetic separation.
Selecting: hand sorting or color sorting, which can separate big chucks.
Crushing: rough crushing and fine crushing.
Grinding: continuous grinding operation is carried out by using the gravel mill or rod mill lined with ceramic liner plate and quartzite.
Strong magnetic separation: Strong magnetic separation is carried out for separating iron and other magnetic minerals. The magnetic strength is over 1200kA/m.
Albite feldspar has well-proportioned mineral constitute and stable quality. The potash feldspar and soda feldspar is about 50~60%. The gangue minerals include quartz, mica, and iron minerals. This kind of feldspar usually transfer into feldspar concentrates through flotation. The feldspar mining process is mainly:
The raw ores are crushed roughly (in jaw crusher) and middling (in cone crusher) into 20mm.
2. Grinding and classification:
Crushing product is mixed and fed into the close recycle of rod mill and roller screen into under 20 mesh. Then the fine clay impurities under 200 mesh are removed through hydrocyclone and spiral classifier. The minerals between -20 mesh and -200 mesh are sent to flotation workshop.
Remove impurities such as mica, iron ore and quartz. In the first stage, mica was obtained by flotation in a weakly acidic medium with cationic collectors (mainly amine collectors). Mica is purified by flotation and wet-screened with 80 mesh screen, and sold to the mica processing plant for more than 80 meshes. In the second stage, anion collector (mainly sulfonated oil) was used to remove iron ore in weakly acidic medium. In the third stage, feldspar and quartz were separated with a combination collector in a weakly acidic medium.
Of course, the flotation operation is adjusted according to the mineral composition. If the content of mica in the grinding products is very small, can pass the first stage flotation, directly into the second stage iron removal flotation; If the content of iron and quartz can meet the requirements of some glass factories after the first and second stage flotation of the grinding products, the flotation separation of feldspar and quartz in the third stage can be eliminated and the products can be directly used as glass batting in the form of feldspar silica sand mixture.
Granite feldspar is a coarse-grained acid plutonic igneous rock. Its Mosaic grain size is smaller than pegmatite, quartz content accounts for about 25-30%, mica and iron content accounts for about 10%. Feldspar is its main constituent (alkaline), that is, a kind of potassium feldspar and sodium feldspar in a certain proportion of the combination of crystalline feldspar.
Granites have fine grain size, so the cost of grinding and dressing is higher. Granite-type feldspar mining process flow is roughly the same as that of white granite ore dressing process. The process principle of ore dressing includes crushing, grinding, grading, flotation (except iron and mica), flotation (quartz and feldspar separation).
The flotation operation of grinding products shall be determined according to the mineral composition. If the content of mica and iron is low, it will enter the flotation separation of quartz and feldspar directly after graded desilting. If the content of impurities such as mica and iron is high, it is necessary to remove the impurities such as iron and mica by flotation first, and then carry out the separation and flotation of feldspar and quartz.
Feldspar placer is mainly composited with quartz and feldspar. It is mainly formed by the accumulation of some granite and feldspathic metamorphic rocks during long-term weathering. Feldspar placer is inferior to pegmatite feldspar deposit in quality, but because the crushing and grinding operations are neglected in the mining and processing process, the cost of ore processing is relatively low, and it is also one of the important sources of feldspar concentrate at present.
The principle of feldspar placer mining process is rather simple. It mainly includes: washing, scrubbing, classifying, magnetic separation, flotation and so on. The subsequent separation operation shall be determined through the composite of classifying products.
The above is the common four types of feldspar mining processes. Before feldspar flotation, the owner must be undressed ore chemical composition, mineral composition, ore structure, composition, density of run of mine ore, ore grade is relatively grinding degree properties are measured, such as scientific selection of experiment report recommended by single or combined technological process, to remove the quartz, iron, mica and other associated minerals, effective recycling is rich in potassium, sodium feldspar concentrates.
1. Hunan 700tpd feldspar processing project
This mineral is mainly feldspar and quartz, little white mica and tourmaline. The key point in separating quartz and feldspar is how to get qualified feldspar concentrates and quartz concentrates.
Two block and a half crushing and screening – one block close grinding – one rough, three concentrating and three scavenging flotation–fine tailings transportation.
In this project the grade of K2O and Na2O concentrates is 14.16%. The grade of SiO2 concentrates is over 97.87%. The productivity of K2O and Na2O concentrates is 54%, and which of SiO2 is 10%.
2. Hebei 400tpd feldspar processing project
In this project, the main mineral is potash feldspar and soda feldspar, about 60~80%. Then quartz is about 10~30%. Some black mica is about 1~5%. White mica is about 1~5%. Part ores have some magnetite and tourmaline.
Two block and one close crushing and screening – one block close grinding and classifying – magnetic separation, desliming and verse flotation – mechanical dewatering
Finally, in this project, the productivity is 73.31%. it can provide 87972 tons of feldspar per year.