AN OVERVIEW OF PROCESS OPTIONS AND BEHAVIORAL ASPECTS OF THE COPPER VALUES RECOVERED FROM THE COPPER BLEED STREAM OF A COPPER SMELTER DEVELOPED AT THE NATIONAL METALLURGICAL LABORATORY

摘要

In the present research, an effort has been made to prepare copper salt/powder from the copper bleed stream generated during the elec-trowinning of pure copper from the copper anode in a copper smelter. Various approaches have been opted for the complete recovery of copper values such as: evaporation-crystallization, electrolytic process, and direct hydrogen reduction. Physical and chemical properties of copper powder/salt produced from the large-scale experiments from actual plant and model solutions have been evaluated for P/M applications and compared with the standard properties. Thus, mixed crystal suitable for recycling back to the system as a makeup salt containing nickel in a tolerable range could be recovered by evaporation and crystallization of the bleed stream up, to 50 percent. Copper powder recovery by the electrolysis process at a current density of 700 A/m~2 was about 95 percent. Scanning electron microscope examination showed that the powder was dendritic in nature. On annealing, the purity of the copper powder was found to be 99.95 percent. The annealed powder had apparent density of 3.04 g/cc, hydrogen loss 0.72 percent, and acid insoluble as 0.27 percent. On compaction of <104-mu m sized powder, the green density was found to be 8.7 g/cc. Similarly, the recovery of the copper powder obtained from the model copper solution by the hydrogen reduction process was found to be >99 percent and the annealed powder had an apparent density of 3.50 g/cc, flow rate 35.6 g/min, hydrogen loss 0.195 percent, purity 99.8 percent, and green density of 8.57 g/cc while the powder from the actual plant solution was found to have an apparent density of 3.49 g/cc, flow rate 46.0 g/min, hydrogen loss 0.598 percent, purity 99.4 percent, and green density 8.57 g/cc for the powder <100 mu m in size. Thus, the properties of copper powder produced by hydrogen reduction and electrolytic route were compared and were found to be suitable for the P/M applications.