1. Flotation method: China's phosphate rock generally contains higher MgO, phosphorus minerals and gangue minerals are closely symbiotic, and the inlaid grain size is fine. Only by flotation method can we obtain better separation effect, so the flotation method is Chinese phosphorus. One of the most used methods for ore dressing. The flotation method includes direct flotation, reverse flotation, anti-positive (positive-reverse) flotation and double reverse flotation. Direct flotation processes and reverse flotation processes are used in production practice. The direct flotation process uses an effective inhibitor to inhibit gangue minerals in the phosphate ore and a collector to enrich the phosphorus minerals in the flotation foam. The beneficiation process has been successfully applied to the ore dressing industry production of magmatic rock type apatite and sedimentary metamorphic apatite ore. The Jiangsu Jinping Phosphate ore dressing plant is a typical example. Sedimentary silicocalcium (calcium silicon) phosphate rock is recognized as a refractory phosphate rock in the world. Since the development of the direct flotation process for the "S" series of inhibitors, breakthroughs have been made in the beneficiation technology of such phosphorite ore. Reverse flotation process The reverse flotation process is mainly used for the separation of phosphorus minerals and dolomite. The inorganic acid is used as the pH adjuster for the slurry. In the weakly acidic medium, the dolomite is floated with the fatty acid collector, and the phosphorus mineral is rich. Collected in the tank product. The biggest advantage is that the room temperature flotation is realized, and the coarse particle size of the groove product is beneficial to the post-treatment of the product. The process has been successfully applied to the beneficiation industry production of the phosphate rock in the Yanfu Phosphorus Deposit.
2. Rub-off mud process: In the mid-1960s, China began to study the rubbing and eluting mud of Liuyang Phosphorus Mine in Hunan Province, and achieved certain results. In the early 1980s, the research on the Haikou Phosphorite Mine in Yunnan was carried out, and then it was expanded to the low- magnesium weathering mine in the Dianchi area. At present, this technology has been successfully developed and applied to the production of phosphate rock in Dianchi area. The process principle is simple, purely physical beneficiation, that is, the weathered phosphate rock is scrubbed or ground in water to remove surface mud and enrich the phosphorus mineral. The enrichment ratio of the process is not large, and the P2O5 grade can only be increased by 3 to 5 percentage points. Among them, the more typical and the better effect is the Haikou Phosphate Weathered Mine. In 1995, Jinning Phosphate Mine Scrub Factory was completed and put into production.
3. Heavy medium sorting technology: The difference in specific gravity between minerals is the key to heavy medium sorting. China began research in the mid-1980s and found that the key to its technology is whether it can strictly control the separation ratio between 2.8 and 2.9. In 1992, Hubei Yichang Huaguoshu Phosphorus Heavy Medium Plant was put into operation. Heavy medium sorting technology has broad development prospects due to its high sorting efficiency and low environmental pollution. In the long run, this technology is expected to be used as a pre-selection operation to pre-exclude most of the gangue from low-grade phosphate rock, thereby improving the effectiveness of subsequent sorting operations.
4. Roasting digestion process: This is a chemical beneficiation method, mainly used for carbonate type phosphate ore containing little silicate minerals. Using carbonate minerals to liberate CO2 at high temperature, then adding water to hydrate CaO and MgO into fine-grained Ca(OH)2 and Mg(OH)2, and removing calcium and magnesium hydroxide by classification technique to make phosphorus Mineral enrichment. The process has obtained good results in the selection of phosphate rock in Hejiayan, Guizhou Yufu, Datang, etc. in Shaanxi, and has completed the expansion test. However, due to high energy consumption, difficulty in handling the exposed lime milk, and difficulty in production control, it has not been promoted and applied.
5. Chemical beneficiation: This method is mainly used to exclude carbonate minerals, especially MgO, so that the MgO content in the concentrate is reduced to less than 0.5%. Due to the high processing cost, it is only possible to use this technology to treat concentrates if the quality of the concentrate obtained by other beneficiation processes cannot meet the requirements of subsequent processing. In the phosphate ore chemical beneficiation, the extractants used as carbonate minerals are mainly ammonium chloride, sulfuric acid and sulfur dioxide, among which sulfuric acid is the most widely used.
6. Photoelectric picking technology: Photoelectric beneficiation is to use the color difference between ore and gangue for sorting instead of manual hand selection; it is rarely used in phosphate rock production. China has conducted photoelectric picking research on the Kaiyang Phosphorus Mine, which is mainly used to pick up the top dolomite mixed in the mining and obtain certain effects.
China's phosphate ore beneficiation research began in the late 1950s, and in 1958 was completed and put into operation the first large-scale sedimentary metamorphic phosphate rock flotation plant that processed 1.2 million tons of raw ore annually - Jiangsu Jinping Phosphate Mine Concentrator. Thereafter, in 1976, a medium-sized magmatic rock-type apatite flotation plant with an annual processing capacity of 300,000 tons of ore was built and put into operation at the Maying Phosphorus Mine in Hebei Province. The completion of these two plants indicates that China has mastered the mineral processing technology of the easy-selected phosphate rock. At present, direct flotation, reverse flotation, scrub elution, and heavy media sorting have been applied to industrial production.
Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure and display pressure in an integral unit are called pressure gauges or vacuum gauges. A manometer is a good example as it uses a column of liquid to both measure and indicate pressure. Likewise the widely used Bourdon gauge is a mechanical device which both measures and indicates, and is probably the best known type of gauge.
A vacuum gauge is an absolute Pressure Gauge used to measure the pressures lower than the ambient atmospheric pressure.
Other methods of pressure measurement involve sensors which can transmit the pressure reading to a remote indicator or control system (telemetry).
Gauge pressure is zero-referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure. Negative signs are usually omitted. To distinguish a negative pressure, the value may be appended with the word "vacuum" or the gauge may be labeled a "vacuum gauge." These are further divided into two subcategories: high and low vacuum (and sometimes ultra-high vacuum). The applicable pressure ranges of many of the techniques used to measure vacuums have an overlap. Hence, by combining several different types of gauge, it is possible to measure system pressure continuously from 10 mbar down to 10−11 mbar.
Pressure Gauge
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