Study On Technology And Mechanism Of Reducing Silicon Content Of Sulfur Concentrate

For a long time, because of the low grade of concentrate, pyrite is mainly used for manufacture of sulfuric acid, which results in a large amount of sulfuric acid residue deposits as waste that contaminates the environment seriously and leads to a tremendous waste of resources. Production of high quality pyrite concentrate from pyrite resources directly can not only achieve comprehensive utilization of sulfur and iron, but also produce high value-added products. In this thesis, based on the study of the flotation of pyrite and quartz with xanthate as collector, the impact of metal ions on their floatability and mechanism are systemically examined, and the depression of quartz by sodium silicate and acidified sodium silicate are investigated and analyzed.Based on above-mentioned results, a new process are developed for the direct production of high quality pyrite concentrate from Yunfu pyrite mine. Major conclusions and innovations of this thesis are obtained as follows:(1)In the system of sulfide ore flotation, ions like Fe3+,Cu2+,Pb2+ existing in the pulp can activate the flotation of quartz under certain conditions, which is one of the main causes of higher content of quartz in the sulfur concentrate. Characterizations of Zeta potential and adsorption of PAX show that the Fe3+, Cu2+, Pb2+ can adsorb on the surface of quartz. The activation of quartz is originated from the interaction between xanthate and these ions, which leads to the adsorption of xanthate onto the quarzt surface and then forms a hydrophobic surface.(2)Using PAX as collector for pyrite may enhance the flotation of pyrite, as well as avoid the activation of quartz since no metal ions are added, which enlarges the flotation wettability difference of pyrite and quartz.(3)HSAB principle and the calculation results of group electronegativity show that the interaction between silicic acid radical of the sodium silicate and quartz is stronger than that of PAX and quartz, which is the main reason of the depression of quartz by sodium silicate. Acidified sodium silicate displays stronger depression than sodium silicate on the quartz flotation, because the acidified sodium silicate can form more silica gel on the surface of quartz, thus eliminate the quartz activation by metal ions.(4)A novel technical process called pre-removing impurity strengthening pyrite collecting-selective depression of quartz is developed to produce high quality sulfur concentrate for the Guangdong Yunfu pyrite. Using the raw ore with sulfur content of 25.57%, we obtain high-quality sulfur concentrate with sulfur grade of 51.32%, recovery rate of 54.52% and silica content of 1.38%,and high-grade sulfur concentrate with sulfur grade of 46.64% and recovery rate of 33.17%, respectively. The combined process of flotation column and flotation machine can improve the product quality and simplify the process.