Improving Productivity and Energy Efficiency in Copper Electrowinning Plants
This paper presents strategies to improve energy efficiency and productivity in copper electrowinning (EW) plants. Plant modeling is based on updated technical data and specific measurements obtained in a tankhouse during a complete production cycle (four to five continuous days). The industrial EW plant site examined produces 180 000 ton/year with an operating current density of 300 A/m2 and a current dispersion of 8.5%. Proposals are based on the use of Optibar intercell bars and the reduction of distance between electrodes. Due to these changes, an improvement of +4.3% in energy efficiency combined with an increase of +3.4% in production can be accomplished. The productivity improvement projected for the plant is U.S.$ 10 million/year.
On the Efficiency and Reliability of High-Current Rectifiers
Industrial electrolytic rectifiers work with high currents (in the order of kilo Amps) and very low dc voltage levels (few hundred Volts). The preferred industrial solutions for this type of application are thyristor-based double-bridge and four-star multi-pulse rectifiers. A number of alternative more advanced rectifiers have been recently proposed presenting improved electrical properties, such as reduced harmonic distortion and reduced reactive power consumption. The various tradeoffs existent between these topologies have been evaluated only partially. This paper presents a full evaluation method based on standards. It should become a valuable tool for the plant design engineer offering quantitative figures to support the electrical project. The proposed method is based on the reliability, electrical performance, efficiency and required equipment investment for these rectifiers. The IEEE standards 493-1997 and IEEE C57.18.10 for reliability and efficiency are the basis of this method, being used specifically to configure the evaluation platform. Complete results are presented for the conventional double-bridge and four-star rectifiers, and for, "late harvest" rectifier topologies including the chopper-rectifier, the sequential rectifier, and the filterless rectifier. From these, it is concluded that the modular multi-cell technology used in the chopper high-current rectifier is capable to challenge thyristor-based industrial solutions
Degradable polymers : principles and applications
1. Why Biodegradable Polymers? G. Scott. 2. An Overview of Biodegradable Polymers and Biodegradation of Polymers S.H. Huang. 3. Degradation and Stabilization of Carbon-Chain Polymers G. Scott. 4. Techniques and Methods of Polymer Degradation S. Karlsson, A.-C. Albertsson. 5. Biodegradation of Aliphatic Polyesters Suming Li, M. Vert. 6. Starch-Polymer Composites C. Bastioli. 7. Polymers from Renewable Sources E. Chiellini, et al. 8. Sustainable Poly(Hydroxyalkanoate) (PHA) Production G. Braunegg. 9. Polyhydroxyalkanoates: Properties and Modification for High Volume Application I. Chodak. 10. Biodegradable Polymers in Medicine E Piskin. 11. Environmentally Biodegradable Water-Soluble Polymers G. Swift. 12. Plastics and the Environment J. Guillet. 13. Degradable Hydrocarbon Polymers in Waste and Litter Control G. Scott, D.M. Wiles. Subject Index.