Progress in Phosphate Ore Dressing Technology (1)
From a global perspective, the production of phosphorus ore trade reached one hundred and fifty million tons, and will increase year by year. The rich ore and easy-to-select phosphate rock resources will be gradually reduced, and the enrichment of medium- and low-grade refractory phosphate ore has received widespread attention. For example, in the past ten years, Brazil has succeeded in developing and utilizing its own P2O 5 content with a P 2 O 5 content of 10 to 15% and a large amount of carbonate gangue and mineral inclusions. The P 2 O 5 content is also attracting worldwide attention in terms of 5% normal-gas, very low-grade apatite deposits. Exploitation in China P 2 O 5 content of about 10%, and contains a large amount of dolomite mineral deposits and metamorphic rock phosphate content in terms of P 2 O 5 15 to 25% silicon calcium phosphate rock deposits also made significant progress. Other countries such as India, Egypt, Syria, Senegal, Togo, Jordan, Iraq, etc. are actively developing their own low-grade phosphate deposits. Even the Soviet Union, the United States and other countries phosphate rock is rich in resources, but also attaches great importance to the issue of this national crisis enriched mineral stone. For example, the Soviet Union's beneficiation research on its carcass phosphate ore, the United States for its South Florida phosphate-dolomite ore and western silicon-calcium phosphate ore dressing experimental research. The results of these experimental studies and the experience of industrial utilization have not only promoted the development of the world phosphate fertilizer industry, but also promoted the improvement, innovation and progress of phosphate ore beneficiation technology from around the world.
In the world of phosphate ore dressing practice, the current dominant method of selection is still scrubbing, deliming, flotation and roasting. Photoelectric sorting and heavy medium sorting of phosphate ore have also begun to receive attention in recent years.
Traditional washing processes and equipment are becoming more and more perfect. A special washing machine is currently widely used to remove clay impurities and purify the surface of phosphate particles. For example, Algeria is used to remove the slime before the roasting of the Wengke Phosphate Mine. The Tunisia pilot plant in the grinding cycle, the Bathoms classifier is pre-classified before being installed in the hydrocyclone. In the process uses two stages or three off the mud, some of the United States and the Soviet Union concentrator general practice, such as the Soviet Union Karatau, Kim Ji Xiepu Florida phosphate rock phosphate rock processing plant and concentrator. China's surface weathered phosphate ore around Dianchi Lake in Yunnan is also widely used in multi-stage scrubbing and desliming processes.
The calcination method of phosphate rock has also been developed. The calcination can be carried out in a shaft furnace, a converter and a boiling furnace, which should be classified as a state-of-the-art roaster, and is therefore used in some phosphate ore dressing plants such as the United States, Morocco, and Algeria, but the size of the raw materials to be charged is fine. In order to save fuel and obtain coarse ore products, sometimes only some of the phosphate rock is calcined. For example, Israel Negev Phosphate has developed a partially calcined new phosphate product, which saves about 70% of energy. In the new roasting process, such as the "flicker roasting" developed by FCB of France, the roasting process can be completed in only 3 seconds. Low-temperature roasting of phosphate rock has long been used in the United States to select its western phosphate rock. This method has also been tested in China's Tiantaishan phosphate mine. The decomposition of carbonate minerals in phosphate rock during calcination consumes a large amount of heat, which is also related to the species of carbonate minerals and the amount of other impurities. For example, phosphate rock containing carbonate pyrite calcination temperature of only 650 ℃, while also using the heat in the phosphate rock pyrite roasting process generated to compensate for the time necessary to consume calories firing More than 50%.
Further, calcium and magnesium oxides which are generated during the calcination process can be generally removed by a washing method or a wind classification method according to the method of digestion, but in order to achieve the purpose of completely removing them, an acid washing method has been attempted in recent years. With the progress of the roasting process of phosphate ore, the composition minerals in the phosphate ore will inevitably change accordingly. It has been confirmed that the floatability and other changes are not consistent: if the phosphorus minerals become buoyant, the quartz floatability is unchanged; Carbonate minerals become buoyant. This naturally facilitates flotation separation.
For the pre-selection of phosphate rock, in addition to the commonly used screening or classification method, there are promising photoelectric sorting and heavy medium sorting techniques. Heavy medium (using magnetite or ferrosilicon or a mixture of the two as a weighting agent) is used for the treatment of carbonated phosphate ore. The Soviet Union has studied the effect of slime content in ore on heavy media separation. Photoelectric beneficiation, the United States used for its Kangda Phosphorus ore dressing plant, the Soviet Union used to select the Karalu Phosphate Mine, and China's Kaiyang and Yichang Phosphate Mines were also tested and tested, all of which achieved satisfactory results.
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