At present, feldspar is mainly derived from the following rocks: pegmatite, some white granite, some fine-grained rocks, weathered granite and feldspar sand. For feldspar from different sources, according to the ore properties of feldspar minerals, the general selection process principle is as follows.

1. High-quality feldspar produced in pegmatite: hand-broken-grinding (or water-milling)-grading.

The wheel mill used in the process has low grinding efficiency and small processing capacity. Since there is no iron removal equipment, the products produced cannot meet the requirements of ceramics and other industries, the production process is backward, and the product quality is low.

2. Weathered granite feldspar: crushing-grinding-grading-flotation (except iron, mica )-flotation (separation of quartz and feldspar).

The feldspar products produced by this process have good quality and high recovery rate, which can meet the different grade requirements of various users. However, the cost of mineral processing is relatively high and there is some pollution to the environment. In the case of declining quality feldspar resources, it can be selected according to the specific conditions of the mine.

3, feldspar in fine-grained rock (generally containing mica, sometimes containing iron): crushing - grinding - screening - magnetic separation.

The feldspar products produced by this process are of high quality and can meet the different needs of various users. Magnetic separation is divided into dry method and wet type. Although the dry magnetic separation process has lower production cost but the iron removal rate is not high; the wet magnetic separation process has higher production cost than the double pressure filtration and drying equipment.

4. Baigangyan (semi-weathered granite):

After being crushed and ball milled by a jaw crusher or a cone crusher , the mica is floated with an amine; the iron mineral is floated with hydrochloric acid; and the feldspar is floated with an amine to separate the quartz. The feldspar sands can also be sorted in a similar way.

5. Changshi sand mine:
Water-eluting mud-sieving (or flotation separation of quartz, etc.).

Feldspar used to produce high-grade ceramics with stricter iron content. Acid leaching is sometimes used to remove iron. Electrostatic dressing was adopted abroad in the 1960s. An old feldspar mine in Yunnan Province has also built an electrostatic beneficiation process, but it failed to produce normally due to the lack of technology.

Since its inception in the 1930s, feldspar has been widely used in the United States, Japan, Germany, Italy and other countries. This flotation method is applicable to Weijing granite, semi-weathered granite, weathered granite and silica sand, so that feldspar production is no longer solely dependent on coarse crystalline pegmatite, and low-grade feldspar deposits are also exploited. After the 1970s, there was a fluorine-free flotation method using hydrofluoric acid or hydrochloric acid instead of hydrofluoric acid as a regulator, fatty diamine and petroleum sulfonate as a collector. In recent years, China has successfully studied fluorine-free and acid-free float. The selection process makes the feldspar flotation not pollute the environment.

In the 1980s, a new method of mineral processing, light selection, appeared. Instead of hand selection, a photometric sorter is used to select block feldspar from the ore. For example, the 16-type photometric ore sorting machine installed at the Glusllno concentrator in Italy uses a magenta laser to shoot the ore. This light can only be reflected from the lighter color ore, encountering dark waste rock particles, and the computer immediately Issue instructions to remove the waste rock with compressed air to achieve the purpose of sorting. If the waste rock is removed by hand, the particle size is required to be larger than 40 mm, and the particle size can be reduced to 10 to 25 mm. Photometric beneficiation can reduce the quality of the selected grade, thereby reducing mining costs.

For flotation of feldspar, filtration dehydration, drying, grinding and air separation are generally required to ensure the user's requirements for moisture and particle size.

The fluorinated mica crystals have very good high temperature resistance, corrosion resistance and light transmission properties, and can work for a long time at a high temperature of 1100°C.

No reaction occurs with strong acids and alkalis; complete light transmittance (pure and transparent). The natural mica plates traditionally used in the observation window of high-pressure boiler water level gauge are all brown, and the light transmittance is not good, and the temperature resistance is in the range of 200-700°C, especially the corrosion resistance is poor. The boiler steam drum water in thermal power plants contains alkali. After reacting with natural mica and alkali, it is washed with hot air and hot water, and it is prone to fluffing, scaling, and being broken. In the short term (about 1-2 months), the water level is not clearly understood. After being broken, it can easily cause leakage. The fluorite mica does not react with the acid-base solution, and does not react with water in the hydration reaction, so that it does not form a layer, does not scale, and does not break. In the long-term (2 to 3 years) scouring of high-temperature and high-pressure water (including acid and alkali), the original clarity and transparency can still be maintained. In China, it has been widely applied to the observation window of steam boiler water level gauge in high-pressure boilers of thermal power plants. It has also been selected by Japanese BBK company and NDK (Colin) company for the observation window of high pressure boiler drum level gauge.

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