Resources Recovery From Ultrafine Material

Ultrafine material is material whose disseminated particle size is small, useful components are difficult or even impossible to monomer dissociate, or the material is over-grinded in monomer dissociation process and some useful components occur as ultrafine form, and adopting conventional separation techniques is difficult to achieve resource recovery. Three types of ultrafine material are taken as research objects in this thesis, and the technical route and process conditions of recovering iron resources from the oolitic hematite and recycling molybdenite resources from the ultrafine tailings, are studied, respectively. Meanwhile, for waste printed circuit board resources, monomer dissociation between valuable metals can not be achieved by physical grinding methods, and pneumatic separation, electrostatic separation, magnetic separation were applied to the relative enrichment of valuable metals.Firstly, mineral or metal composition, dissemination size, occurrence and other features of those materials were characterized in detail by some methods, such as SEM, XRD, XRF, AAS, ICP-AES, chemical composition and laser particle size analysis. On this basis, through the research on separation methods like magnetic roasting, magnetic separation, direct and reverse flotation, oil agglomeration flotation, pneumatic separation, electrostatic separation, the separative technology for the three materials can be determined, respectively, and the resources in ultrafine material were recoveried.About80%hematite occurs in the form of oolitic aggregate in the oolitic hematite, whose iron grade is48.36%. The grinding fineness of less than0.01mm is needed to achieve full dissociation, which is impossible for the actual process. The right technology solutions is magnetization roasting process that can increase magnetic differences between the components, so pre-enriched iron ore concentrate can be gotten. Orthogonal test was carried out to investigate effects of multiple factors during the magnetization roasting-magnetic separation process, and opportune conditions is determined as follow:size is less than3mm, roasting temperature850℃, time40min, ratio of reducing agent mcoal/more=12%and magnetic field intensity1800Gs, iron ore concentrate whose grade and recovery are52.53%and95.28%, respectively, is obtained. Moreover, a qualified iron concentrate can be gotten through benefication on the magnetic concentrate, i.e. closed-circuit test including regrinding, desiliconize reverse flotation by adding GE-609and dephosphorize reverse flotation by adding RAP-138.Molybdenum tailings involved in this thesis containing1.04%molybdenum is mainly in the form of molybdenite, and particles that is less than0.038mm in the tailings is account for68.06%, in which over90%molybdenum metal is distributed. The oil agglomeration flotation tests showed that satisfactory result can be gotten when transformer oil is taken as agglomeration oil, and it can be found the bigger the50, the smaller the50, and the higher the recovery of molybdenite. E.g. Average particle size of the aggregates reachs0.68mm, average particle size of the captured particles decreases to2.05μm, and the molybdenite recovery is over90%. The dosage of0.5kg/t frother, natural pH and stirring time of3min, stirring intensity of400-600r/min are considered as the appropriate conditions. And94.88%of the molybdenum is recovered with a satisfied grade of22.62%in the industrial experiment.For waste printed circuit board (PCB), monomer dissociation between metal and nonmetal can be obtained by crushing, but for the monomer dissociation among valuable metals. Even crushed to less than0.074mm, each size fraction is still a multi-metal compound. Crushed PCB product is the typical disseminated unevenly, and the physical separation only can make part of the valuable metal relative enriched. The performed investigations of PCB showed that pneumatic separation is suitable for0.6～0.9mm grain size relatively, and electrostatic separation is suitable for0.15～0.3mm,0.3～0.6mm and0.9～1.25mm3size fractions. And the whole process that involves crushing, electrostatic and magnetic separation has formed a closed cycle that can return material and provide salable product.