Research On The Beneficiation Technology For The Low Grade Collophane From Dayukou Mine

Phosphate rock is an important raw material for industry and agriculture.The Ministry of Land and Resources listed 20 minerals that cannot meet the demand of China’s domestic economic development after 2010,phosphate rock is one of them.Only a small number of phosphate ores belongs to the free-milling ores in China,and over85%of them belong to the refractory shallow marine sedimentary phosphorite rock which is specially named as collophanite.The low-grade phosphate rock in Dayukou is a collophanite,its mineral and rock composition is extremely complex,and the size distribution of mineral particles is very fine,mineral liberation is difficult.Collophane in Dayukou also contains dolomite,a mineral with similar flotation nature to collophane.Therefore,it is very difficult to beneficiation.In order to improve the recovery rate of Dayukou phosphate rock,new collectors C1and JVC for direct flotation and reverse flotation respectively were used in the direct and reverse flotation process.Laboratory and commercial tests were carried out.The effects of grinding fineness and pulp temperature on direct flotation using new collector C1 were evaluated through orthogonal flotation tests,and optimum operation parameters were determined through open circuit and closed circuit test.In the reverse flotation,new collector JVC was compared with the present used collector SR,and much better flotation performance could obtained;the optimal dosage of the reverse flotation depressant was also determined.Commercial tests further proved that the new collector C1 is an excellent collector for direct flotation of low grade Dayukou phosphate（containing P₂O₅ 18.77%,MgO4.33%）at a fineness of 91.0%minus 200 meshes,and slurry temperature of 55℃,and a flotation concentrate containing P₂O₅ 29.18%,MgO 2.86%could be obtained at a recovery of 93.07%and concentrate yield of 59.49%using the one roughing,two cleaning,middle re-flotation process.The reverse flotation is carried out through a process of one roughing and one scavengering process,and a final phosphate concentrate with P₂O₅ 31.62%,MgO 0.60%,yield 49.02%and recovery of 82.59%could be obtained by using new collector JVC.The results show that JVC is also an excellent flotation collector for Dayukou phosphate rock in the reverse flotation.Through the analysis of the reaction mechanism,it is clear that using water glass and an efficient carbonate depressant named DYK in alkaline medium,the depression of silicate minerals and some carbonate minerals with poor floatability were enhanced,the positive flotation collector C1 shows relatively better selectivity and collecting power,so that the phosphorus mineral was fully floated ensuring a higher recovery of phosphorus,and achieving a maximum separation of phosphate minerals from silicate minerals.After the pulp pH of direct flotation concentrate was adjusted to a weak acidity using sulfuric acid,a high efficiency phosphate mineral depressant DPS and the new reverse flotation collector JVC were added.The DPS depresses the flotation of phosphorus mineral while the carbonate in the acidic medium will form CO₂ microbubbles on its surface,thus increase the adhesion of carbonate particles to bubbles in the flotation process,strengthening the collection of dolomite,which is conducive to the reverse flotation.The role of sulfuric acid in reverse flotation of phosphate minerals is adjusting the medium pH to the better range for floatability of dolomite and dissolving the CO₃^2-on the carbonate surface to exposing Ca²⁺preferentially,so showing an anion activation characteristics,which is favorable for the adsorption of the collector.The separation between phosphate rock and dolomite is much more completed using JVC,and the MgO content in the concentrate can be reduced to below 1%,qualified phosphorus concentrate obtained.The new collectors have successfully application in Dayukou low-grade phosphate rock and high quality concentrate of P₂O₅≥30%,MgO≤1%can be produced,ensuring its using both in the production of high-quality products of DAP and high concentrations of NPK compound fertilizer.It can also be further used for the development of fine phosphorus chemical products,thereby increasing the added value of phosphate rock resources,achieving a higher economic efficiency.