1997 TMS Annual Meeting: Monday Abstracts

GENERAL RECYCLING: Session I: Theory

Session Chairpersons: James C. Daley, Daley & Associates, 1020 W. Cactus Wren Drive, Phoenix, AZ 85021; John M. Rapkoch, Davy International, 2440 Camino Ramon, San Ramon, CA 94583

8:30 am

USE OF PVC AS A CHLORINATING AGENT IN THE RECYCLING OF METALS: F. Tailoka, D.J. Fray, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB2 3QZ, United Kingdom

The standard free energy of formation of the oxides of the ferrous metals is generally more negative than that for the chlorides whilst the reverse is true for the equivalent compounds of the non-ferrous metals. As a source of chlorinating agent PVC has been used. PVC has the nominal formula C2H2HCI. On combustion in air, considerable heat is generated and hydrogen chloride, water vapor and carbon dioxide are evolved. It can be regarded as a free source of heat and a chlorinating agent if scrap PVC is used. In this work, this gas has successfully been used to separate zinc, lead and copper from residues such as Jarosite, EAF dust and waste materials containing copper. Dioxins were not detected either in the residues or the condensed chlorides.

8:55 am

RECOVERING MAGNESIUM FROM SOAPSTONE AND ASBESTOS TAILINGS: V.A. Leão, C.A. Silva, M.G. Menenzes, J.C. Pires, L.G. Macedo, School of Mines, Federal University of Ouro Preto, Praca Tiradentes, 20; Ouro Preto, MG, 35400-000, Brazil

Asbestos industry produces large amounts of serpentine (magnesium silicate) tailings. The effect of this on human health is well-known. Besides this, the processing of a Brazilian rock known as "Pedra sabão" (soap stone) generates powders that are discharged in the environment. This material is also a potential resource of magnesium. Magnesium oxide is used in many industries like refractory, waste water treatment, among others. The applicability of hydrochloric leaching for the recuperation of magnesium oxide from those materials has been investigated. The effect of time, temperature, particle size and solid/liquid ratio, on the leaching of magnesium and impurities, is discussed.

9:20 am

THE RECOVERY OF TELLURIUM FROM COPPER ANODE SLIME BY HYDRO-METALLURGICAL PROCESSES: K.-I. Rhee, C.-K. Lee, Korea Institute of Geology, Mining and Minerals, P.O. Box 14, Taejon, Korea 305-350; H.S. Kim, T.H. Kim, C.S. Yoo, H.J. Sohn, Y.-J. Kim, Dept of Mining & Petroleum Engrg., Seoul National University, 151-742 Seoul, Korea

The recovery of tellurium from pretreated copper anode slime was carried out by a series of hydrometallurgical processes. These include leaching of cemented Te at high temperature with oxygen purging in NaOH solution, precipitation of TeO2 from leach liquor, leaching of TeO2 in alkaline solution, precipitation of impurities by Na2S, and electrowinning of tellurium. The optimum conditions of each process were determined and discussed in terms of various parameters associated with each step to maximize the recovery and purity of tellurium.

9:45 am BREAK

10:00 am

PRODUCTION OF NON-FERROUS METALLIC CONCENTRATES FROM ELECTRONIC SCRAP: Jorge Alberto Soares Tenorio, Ricardo Perez Menett, Arthur Pinto Chaves, Department of Metallurgical and Materials Engineering, University of Sao Paulo, 05508-900, Sao Paulo, Brazil

Electronic components have metals with important valor like Au, Ag and Cu. These metals have a high performance in electric conductance. The recycling of scrap, however is too difficult because we have the presence of other metals like Fe, Al, Zn, Sn, more ceramics and plastics, all together in electronic components. This work had for subject define one way for physical separation. We have researched methods that obtained metallic concentrates non-ferrous. By the way we have used three types of scrap. We have used equipment of mineral processing. The metallic concentration make more easy the recuperation of metals because short the volume of material used. We have obtained, since of types studied an middle compassion of plastic, ceramic and metals.

10:25 am

DESIGN AND CONSTRUCTION OF A SMALL-SCALE USED BEVERAGE CAN RECYCLING UNIT: Jim S-J. Chen, Frederick Higgins, Joseph Vinch, James Kelly, Steven Smigiel, Center for Environmental Studies, College of Engineering, Temple University, Philadelphia, PA 19122

A small-scale recycling unit for used beverage cans is designed, constructed and tested. The unit consists of a rotary kiln for delacquering, a gas-fired furnace crucible for melting, a baghouse for pollution control and an air recirculating system for heat recovery and oxygen control. The delacquering kiln utilizes a counter flow thermal decoating process and the optimized operating condition was found to be at 1000°F, 6-7% O2 and a residence time of 15 minutes. In melting, a special salt mixture is made by combining cryolite and sodium chloride. The salt mixture has a low melting temperature (<1250°F) and is effective for demagging and degassing. The yield of the small-scale unit is about 90% and the energy efficiency matches those reported for large-scale facilities.

10:50 am

OPTIMIZATION OF SALT COMPOSITION IN THE RECYCLING OF ALUMINUM CANS: Jorge Alberto Soares Tenorio, Fabio Delgado, Department of Metallurgical and Materials Engineering, University of Sao Paulo, 05508-900, Sao Paulo, Brazil

During the melting processing of aluminum can scrap there is a considerable loss of metal due of metal trapping in the dross. Among all techniques available to recover this kind of scrap, the one using saline fluxes, based on NaCl / KCl equimolar composition and fluorides addition is outstanding. The investigation into the melting of AA3004 and AA5182 alloys (materials which the body and the lid of beverage cans are made of), the effect of delacquering, and the influence of different fluxes and the temperatures on the process yield are the main objectives of this work. Melting tests were carried out in order to access the effect of fluorides and the melting temperature on the recycling process yield. The fluoride efficiency for the temperature of 750°C was: CaF2 < NaF < Na3AlF6 < KF.