Phosphate ore beneficiation process: unlocking the value of phosphate ore

As an important non-metallic chemical raw material, phosphate ore plays an indispensable role in many fields such as agriculture and chemical industry. However, natural phosphate ore often coexists with a variety of veinstone minerals, which requires beneficiation process to enhance the quality and meet the needs of different industries. Reasonable selection of phosphorus ore beneficiation process and chemicals is crucial, and is the core link to achieve the efficient use of phosphorus ore.

Phosphorus ore flotation process is mainly based on the nature of the ore and the type of impurities contained in the selection, common direct positive flotation, a single reverse flotation and two-step flotation (positive - reverse flotation, reverse - positive flotation and double reverse flotation). Direct positive flotation is in an alkaline environment, adding inhibitors to inhibit the silicate and other vein minerals, so that the phosphorus minerals are enriched, applicable to siliceous or calcium - siliceous phosphorus block rock and so on. A low-grade iron-containing phosphate ore in Liaoning province, using anhydrous sodium carbonate as pH adjuster, water glass to inhibit chalcopyrite minerals, composite anionic agent as a collector, through the ‘one coarse, two fine and one sweep’ process, to obtain high-quality phosphorus concentrate. A phosphate mine in Lianyungang, Jiangsu Province, uses sodium oleate as the capture agent, adopts ‘one coarse, one fine and one sweep’ positive flotation closed-circuit process, effectively separating fluoroapatite and chondritic minerals.

Single reverse flotation is suitable for calcareous phosphate rock with dense lumps or bands of phosphate minerals and more carbonate minerals. It inhibits phosphorites by using inhibitors such as sulphuric acid and phosphoric acid, and specific traps remove the chondritic minerals. A low-grade siliceous and silicate colloidal phosphorus ore in Puning, Guangdong Province, uses a single reverse flotation after matching with Kunyang high-magnesium ore to remove impurities and bring the phosphorus concentrate up to the sales standard. A phosphate plant in Yunnan will be different mining areas of the original ore allocation flotation, to solve the problem of low-grade silicate-type gum phosphorus ore stockpile, to achieve the maximum use of resources.

The cost of two-step flotation process is relatively high, but it can achieve better flotation indexes and economic benefits for complex ores. Positive - reverse flotation is used to deal with calcium-siliceous phosphorite, first positive flotation to remove siliceous veinstone, and then reverse flotation to remove carbonate veinstone. Sichuan Qingping Phosphorus Mine adopts normal temperature ‘four no’ positive and negative flotation new technology, making full use of low-grade phosphorus ore, reducing the consumption of chemicals and costs. Reverse - positive flotation is suitable for the need to effectively reduce the content of carbonate minerals and siliceous minerals in the ore, such as a low-grade silica-calcium weathering phosphorus ores abroad, through the desliming of reverse - positive flotation to obtain high-quality phosphorus concentrate. Double reverse flotation process is commonly used in siliceous veinstone and carbonate content of low mixed phosphate rock, can be carried out at room temperature, the cost is low. A phosphorus mine in Yibin adopts double reverse flotation, which provides technical support for the development of low-grade phosphorus ore in Yibin.

Flotation chemicals are the key of phosphorus ore flotation, including adjusting agent, trapping agent, foaming agent, flocculant, etc., among which adjusting agent and inhibitor are the hot spots of research. Among the adjusting agents, sodium carbonate and sodium hydroxide are commonly used as pH adjusting agents, often used jointly or in combination with other agents to improve the flotation effect by adjusting the pH value of the pulp. Commonly used inhibitors in the flotation industry are inorganic acids, salts and organic inhibitors, such as phosphoric acid, sulfuric acid, etc., but there are problems such as large dosage and serious calcium formation. Some studies have proposed to replace sulfuric acid and phosphoric acid with sodium fluorosilicate mother liquor to reduce costs and extend equipment life.

As for the capture agent, fatty acids and their derivatives are most commonly used, but they have limitations such as small solubility and poor dispersibility. The performance can be improved by modification and compounding, such as the new anionic modified collector DNG6 has a strong ability to capture apatite, and the flotation effect is improved after the treatment of oleic acid sulfated soap. The combination method is to compound multiple fatty acids or fatty acids with other surfactants to enhance the recovery effect. Amine trappers are used in reverse flotation, which can effectively remove siliceous chalcopyrite minerals, such as the new desiliconisation trapper KDJ to achieve reverse flotation desiliconisation under weak acid conditions, which provides technological support for the use of medium and low grade high silica-magnesium gum phosphorite ores.

In phosphate ore beneficiation, the selection of process and chemicals are interrelated, and need to comprehensively consider the nature of the ore, cost, environmental protection and other factors. In the future, with the continuous progress of technology, phosphorus ore dressing process and chemicals will move towards a more efficient, green, economic direction, and further enhance the use of phosphorus resources, providing a strong guarantee for the development of related industries.