Kiyoshi Shibata and Yoshio Waseda
Institute for Advanced Materials Processing, Tohoku University, Sendai 980-77
Recycling of materials is a key technology for environmental burden reduction or natural resources conservation in materials production. However, the energy consumption and environmental burden associated with recycling are frequently subject to be very severe. Thus, it is very important to evaluate the performance of the recycling process by obtaining quantitative information in which the condition is the best for covering the original purpose of recycling. This work is to propose a new assessment model for metal production and a recycling system. The model consists of three processes, smelting of ore, cascading of metal scrap and upgrading of metal scrap, and the present approach is to assess the total energy consumption of the metal production system, by introducing two equations for describing the relationships between the critical impurity content and the mass of production or scrap recycling. The upgrading process is requested in cases in which the content of the impurity should be reduced due to the quality demand of the corresponding metal market. According to the model, the total energy consumption in the metal production system can be described as a function of recycling rate and performance of the upgrading process. Model calculation was conducted using the cases of the aluminum and steel production process. The results suggest that the impurity removal efficiency and yield in the upgrading process are essential to reduce the energy consumption in these metal production systems. Especially, such points should be explicitly controlled in the aluminum recycling process. The potential capability of this model may not be overemphasized. It is rather surprisingly effective for the development of beneficial recycling of metals by obtaining several quantitative information required for the process design and its control.
(Received January 27, 1997)
recycling, separation, impurity, aluminum, steel, iron, copper, energy consumption, yield, modeling, life cycle assessment
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