How to sort feldspar

Feldspar is a group of minerals consisting of aluminosilicates of potassium, sodium, calcium and barium. The main chemical composition is SiO2, Al2O3, CaO, K2O, Na2O.

　　Feldspar group minerals are the most important rock-forming minerals in nature, accounting for about 50%~60~ of the mineral composition of the earth's crust. Felsic minerals are widely produced in various genetic types of rocks, and are the main rock-forming minerals of magmatic and metamorphic rocks.

　　As feldspar is a rock-forming mineral, it is difficult to separate from other minerals in most cases, so the only feldspar deposits of industrial significance are pegmatite deposits with huge crystals that are easy to separate.

I. Types of feldspar

According to its chemical composition and crystallization characteristics, it can be divided into two subgroups: potassium sodium feldspar and plagioclase feldspar subgroup.

　　(1) Potassium-sodium feldspar subgroup

　　It is composed of potassium feldspar molecules and sodium feldspar molecules. The natural output of potassium feldspar are mixed with sodium feldspar, so often called potassium feldspar, all belong to potassium sodium feldspar, common potassium sodium feldspar species.

　　Turbidite, (K, Na)[AlSi3O8], contains sodium feldspar

　　molecules up to 50%, K: Na = 1: 1

　　Orthoclase, (K, Na)[AlSi3O8], containing sodium feldspar

　　molecules up to 30%, K:Na = 2:1

　　Microplagioclase, (K, Na)[AlSi3O8], containing sodium feldspar

　  molecules up to 20%, K: Na = 4: 1

　　(2) Plagioclase subgroup

　　It consists of sodium feldspar molecules and calcium feldspar molecules, which can be mixed in any ratio to form a continuous series of plagioclase analogues. It can be divided into six types: sodium feldspar, more feldspar, medium feldspar, labradorite, peperite, calcium feldspar, etc. Among them.

　　Sodium feldspar, containing 0-10% of calcium feldspar molecules, is produced in pegmatites, fine crystal rocks and schist.

　　Calcium feldspar, containing calcium feldspar molecules 90 ~ 100%, produced in gabbro and related rocks.

　　2. Chemical composition of feldspar

　　The feldspar species used in the glass and ceramic industry are mainly microplagioclase, orthoclase and sodium feldspar.

　　The theoretical chemical composition of potassium feldspar is: K2O 16.90%, Al2O3 18.40%, SiO2, 64.70%.

　　(Among them: orthoclase often contains sodium feldspar, more up to 30%; microcline feldspar is a more pure potassium feldspar, but it contains sodium feldspar, more up to 20%)

　　The theoretical chemical composition of sodium feldspar is: Na2O 11.80%, Al2O3 19.50%, SiO2, 68.70%

　　But the pure sodium feldspar is rare, the content of Na2O is often lower than the theoretical value, and contains K2O, CaO, etc.

Second, the physical and chemical properties of feldspar

Feldspar family minerals are generally white, gray, light flesh red, glassy luster, decomposition development, hardness of 6 ~ 6.5, density of 2.5 ~ 2.7g/cm3.

　　As an important industrial raw material, the melting point, melting interval and viscosity of feldspar have important application significance.

　　1. Melting point and melt interval

　　The melting point of potassium feldspar is 1290℃, sodium feldspar is 1215℃, and

　　Calcium feldspar is 1552℃, and barium feldspar is 1715℃.

　　The wide melting interval is also one of the excellent process properties of feldspar, and the melting interval varies with the content of feldspar components. Potassium microplagioclase feldspar in 1160 ~ 1180 ℃ is liquid, to 1210 ~ 1280 ℃ before completely molten.

　　2. Melting liquid viscosity

　　When feldspar is melted, the melt viscosity depends on the mineral composition, chemical composition and melting temperature of the ore.

　　At the same temperature potassium feldspar melt than sodium feldspar melt viscosity, and as the temperature increases, sodium feldspar melt quickly becomes a small viscosity easy to dilute the fluid, so that the ceramic blank deformation.

　　Because of the potassium feldspar melting point is not high, melting interval time is long, molten liquid viscosity and other advantages, so in the industrial use of more than other feldspar more widely

　　3. Chemical stability

　　Potassium feldspar glass and soda feldspar glass have a high degree of chemical stability, except for high concentrations of sulfuric acid and hydrofluoric acid, not subject to corrosion by any other acids, alkalis.

　　4. Fluctuating properties

　　The feldspar melt has a fluxing effect on other substances, and its fluxing ability is related to the temperature and the type of feldspar. Sodium feldspar melt has a greater fusion effect on quartz than potassium feldspar melt.

　5. Easy to grind and grindability

　　The feldspar has good grinding and grindability due to the development of decomposition.

The use of feldspar

Feldspar is mainly used in glass and ceramic industry. The amount of feldspar in the glass industry accounts for 50%~60% of feldspar, the amount of feldspar in the ceramic industry accounts for 30%, and the rest is used in filler and other sectors.

　　1.Glass melting agent

　　Feldspar is one of the components of the glass mixture. It is mainly used to increase the alumina content in the glass ingredients, reduce the melting temperature and increase the alkali content in glass production, in order to reduce the amount of alkali.

　　Feldspar melt into glass process is relatively slow, crystallization ability is small, can prevent the formation of glass in the process of precipitation of crystals and damage to the product. Adjust the viscosity of the glass.

　　Generally used as a mixture of glass, such as potassium feldspar and sodium feldspar. Feldspar can also be used as glass fiber raw materials.

　　2. Ceramic blank raw materials

　　Before firing as a barren raw material to reduce the drying shrinkage deformation of the blank, improve drying performance, shorten the drying time.

　　When firing as a fusing agent to reduce the firing temperature, to promote the fusion of quartz and kaolin, accelerate the formation of mullite, so that the dense body and reduce the void, improve its mechanical strength and dielectric properties, improve the light transmission of the body. The amount of admixture is generally around 20%.

　　3. Ceramic glaze

　　Glaze is mainly composed of feldspar, quartz and clay raw materials, of which the content of feldspar up to 10% ~ 35%. In the ceramic industry (blank and glaze) is mainly with potassium feldspar.

　　Due to the feldspar fusion agent effect, so that the glaze melt fully. Feldspar glaze luster is good, smooth and transparent glaze.

　　4. Enamel raw materials

　　With feldspar and other mineral raw materials blended into enamel. The amount of feldspar blending is usually 20% to 30%.

　5.abrasive

　　The production of grinding wheels used as ceramic cements components, the content of

　　28%～30%

　　6. Other

　　Feldspar with high potassium content can be used as raw material for extracting potassium fertilizer.

　　It is one of the raw materials for the production of white cement.

　　Paper, refractory materials, machinery manufacturing, coatings, welding rods, etc. as filler

D. Sorting of feldspar

According to the different types and nature of feldspar deposits, and the use of different beneficiation methods. In the past, it was generally crushed and ground after hand sorting, and then magnetic separation was used to remove iron minerals. Such sorting method has been criticized by the majority of feldspar sorting enterprises due to the high cost, low efficiency and the inability to be used on a large scale.

In recent years, as the quality of feldspar ore decreases, the quality of the product requirements continue to improve, as well as the development of comprehensive mine recovery, the introduction of increasingly sophisticated technology of color separation equipment for sorting operations, so as to remove quartz, mica, iron and titanium and other associated minerals.

After years of development, our company (Hefei Mingde Photoelectric Technology Co., Ltd.) has developed ore color sorting machine for ore sorting, which is also applied to feldspar sorting operation on a large scale. For feldspar sorting, we use the photoelectric principle to identify and analyze the color of feldspar, so as to carry out sorting. This way of sorting improves the quality and productivity of the product and realizes the value of the ore itself.

After research and the use of the majority of mining enterprises to prove that the sorting of feldspar and the entire ore industry will use the ore color sorting machine to produce, which is the progress of the industry, but also the progress of the times, but also the trend of the development of ore. Take the road of fine processing, deep processing has come, the use of automated equipment sorting is imminent. Mingde photoelectric welcome all mining enterprises to visit our company.