Feldspar is one of the most abundant minerals in the earth's crust and is produced in some sedimentary rocks and in almost all igneous rocks.
In general, pure feldspar is rare in nature, and even in minerals known as "potassium feldspar", some albite may be symbiotic or mixed. The feldspar mineral composed of potassium feldspar and albite is generally called alkaline feldspar; the feldspar mineral composed of albite and anorthite is called plagioclase; the feldspar mineral composed of anorthite and celsian is called It is an alkaline earth feldspar. Potassium micro-plagioclase is a kind of potassium feldspar whose crystal system is triclinic. The albite is regularly arranged in the potassium feldspar, called stripe feldspar.
At present, the feldspar that has been exploited in China is mainly produced in pegmatite (or pegmatite granite ) (such as Shandong Xintai Changshi Mine, Hunan Hengshan Sodium Feldspar Mine, Linxiang County Tuanwan Changshi Mine, etc.). Some other feldspars are produced in weathered granites (such as the Yunnan old feldspar mine, the Liangting River mine in Susong County, Anhui), fine-grained rocks (such as the Fengyang Weishan mine in Anhui), and hydrothermal alteration deposits (such as Anhui Suxian). Dry mountain mine) and feldspathic sandstone (such as Yikeng Mine in Qimen County, Anhui Province). In addition, the comprehensive recovery of feldspar in other ore beneficiation processes is also one of the sources of feldspar production. The harmful minerals found in feldspar are mainly iron minerals. Other impurity minerals include clay, quartz , mica , garnet, tourmaline , beryl, etc. Therefore, it is necessary to select and select the feldspar mine. And because the main deposits of feldspar are pegmatite, weathered granite, fine-grained rock (semi-weathered granite), in addition to feldspathic pottery, potassic rhyolite, albite and sand associated with serpentinite Stone diorite and white granite. Depending on the type of feldspar deposit and the nature of the ore, different methods of beneficiation are required. Generally, the crushing and grinding is carried out after the hand picking, and then the iron mineral is removed by magnetic separation. In recent years, with the reduction of rich feldspar mines and the development of other mines' comprehensive recovery of feldspar technology, more complicated sorting operations such as re-election, electric selection and flotation have been introduced to eliminate the accompanying right-wing and mica. Minerals, the feldspar concentrate rich in potassium and sodium, the purpose of recycling quality products.
Requirements for feldspar beneficiation
In order to make feldspar suitable for manufacturing, feldspar must meet certain technical requirements. It must be as free of impurities as possible, so it is necessary to select the feldspar, and the impurities must be known before the selection.
Classification of impurities contained in feldspar
These impurities are now distinguished as follows based on the effect on the degree of damage to the ceramic.
(1) harmless dissolved impurities and albite derivatives in striped feldspar
1 absolutely harmful impurities.
2 brown condensate of a large amount of hydroxide.
3 biotite, pyrite, tourmaline, pure sodium pyroxene and other iron-bearing minerals.
(2) Muscovite that is difficult to crush should pay special attention to these impurities when sorting pegmatite and feldspar. All the inclusions of these minerals that can be seen with the eyes must be removed as much as possible.
The more harmful impurities are quartz, plagioclase, nepheline, sericite, kaolin and other similar minerals. These minerals not to make the deterioration of the quality of ceramic products, however, because of their different contents, the contrast between the area of each kind of deposit feldspar, aluminum oxide and silicon oxide is different, therefore, the presence of such impurities causes the mined The sorting work at that time is complicated, and at the same time it increases the difficulty of the technical operation process.
The industrial technical significance and effects of various impurities are different. The impurities can form dark spots on the article, which degrades the quality of the product. As mentioned above, the most harmful is iron, the content of iron oxide in feldspar can not exceed 0.5% for light-colored tablets, and can not exceed 0.2% to 0.3% for white-colored transparent enamel products.
Industry is generally required for feldspar
(1) Purity
The hand-selected feldspar has no or slightly iron minerals on the surface, and the total amount of iron-containing minerals and mica flakes is less than 8%. Among them, feldspar is sorted in advance according to the appearance characteristics.
1Selected - first white or fiber color; block, 20 ~ 200cm, the allowable content of debris is 8%; the allowable content of quartz and other impurities is 3%; there must be no surface iron impurities.
2 Selected - second white or fiber color; block, 20 ~ 200cm, the allowable content of debris is 15%; the allowable content of quartz and other impurities is not more than 15%; there must be no surface iron impurities.
3 Ordinary - the first amount of debris is allowed to be 20%; the content of quartz and other impurities is not more than 10%; a small amount of iron impurities are allowed on the surface.
4 Ordinary - the second class of debris is allowed to contain no more than 25% to 30%; quartz and other impurities are not more than 20%; the surface allows iron impurities.
In the 1930s and 1940s, these specifications were generally adopted in the Soviet feldspar industry. They only provided the bulk weight, the presence of impurities and surface contamination, but could not meet the needs.
The classification of American ceramsite is based on the particle composition of the ground raw material, the content of silica, the ratio of potassium oxide and sodium oxide, the content of sodium oxide, and the content of iron oxide.
(2) Performance
After calcination at 1300 ° C, it should be melted into a white transparent, lustrous glass body.
(3) Mineralization rate
The content of feldspar in the ore body is above 40%, and the ore block is greater than 5cm.
Depending on the type of feldspar deposit and the nature of the ore, different methods of beneficiation are required. Generally, crushing and grinding are carried out after the first choice of the stope, and then the iron mineral is removed by magnetic separation.
In recent years, with the reduction of Changshi rich ore and the development of other mines comprehensive recovery of feldspar technology, re-election, electrification, flotation and other mineral processing methods have been introduced for joint sorting operations to remove associated minerals such as quartz and mica. , the purpose of recycling feldspar concentrate rich in potassium and sodium. Table 1 lists the main beneficiation methods for feldspar.
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