Phosphate rock is an important non-renewable resource and an important component of fertilizers and phosphorus-based chemicals. According to their **, phosphate deposits can be divided into three main categories: 1 — sediments from marine sediments; 2 — igneous and metamorphic deposits; 3 — Biological sediments, most of the world's phosphate resources are sedimentary deposits.
Phosphate rock needs to be processed to reduce the content of gangue minerals such as carbonate, silicate, feldspar, mica, calcite, dolomite and clay to meet the requirements of the phosphate industry.
Depending on the release size of phosphate and gangue minerals and other ore specifications, effective beneficiation can be achieved through a variety of processes such as screening, washing, heavy media separation, washing, roasting, calcination, leaching and flotation.
Crushing and screening are used to remove coarse hard siliceous materials, and friction washing and desliming are used to remove fine parts of clay. If silica is the main gangue material, flotation is the conventional beneficiation technique used. Igneous ores are also suitable for flotation, which is the best way to process such phosphate ores.
Free carbonates are present in phosphate rocks, and additional acids are often required in the production of phosphoric acid and superphosphate by the "wet" process. In addition, the carbon dioxide produced during the acid addition process causes more foaming and results in the formation of smaller-sized gypsum crystals, which can clog downstream phosphogypsum filters. As a result, low-quality phosphoric acid is produced.
Carbonate-rich phosphate deposits can be treated by calcination and acid leaching methods. Calcination is used in areas with low energy costs and limited water resources, such as the Al-Jalamid phosphate mine in Saudi Arabia, which has a carbonate content of 40-50%, organic matter of 8-10%, and P2O5 of 16-25%. It is processed by calcining at 850 for about 1 hour, then leaching the lime with water and quenching it with 5 nh 4 no 3 to remove the magnesium. Calcination is the thermal decomposition of calcareous materials. Depending on the process conditions, calcination may result in the almost complete elimination of the carbonate gangue present in the phosphate rock. In view of the problems of sedimentary phosphate rock, acid leaching is a promising method for treating calcareous phosphate rock.