Takuya Yoshida*, Yasuo Koseki*, Chihiro Fukumoto** and Tatsuya Koizumi**

* Hitachi Research Laboratory, Hitachi Ltd.
** Industrial Processing Division, Hitachi Ltd.

+ Correspondence should be addressed to Takuya Yoshida:
(7-1-1 Omika, Hitachi-shi Ibaraki 319-1292 Japan)

Abstract

Air-sorting is widely used for solid wastes separation for its low-cost and easy-operation. However, it has the disadvantage of unstable performance due to fluctuation in the properties of fed materials, such as particle size and shape. Yet,little is known about the characteristics of air-sorting, and factors which affect separation efficiency have not been clearly reported. This paper presents some findings on the basic characteristics of air-sorting, and a new method for separating shredded aluminum and copper with a high separation efficiency. Preliminary tests to examine the relationship between recovery ratio and wind velocity showed that recovery ratio can be described as an integral calculus of normal distribution as a function of wind velocity. Experiments using rectangular block samples to study the effect of particle shape showed that the wind velocity whereat the particles are blown-up depends on the thickness of particle. This characteristic was supported by a calculation based on a terminal velocity equation. Based on these findings, three alternative air-sorting methods were suggested and tested. A proposed method to roll feeds before sorting showed high separation efficiency with a maximum aluminum and copper recovery ratio of 98-99%, which is higher than 87% of the conventional method.

Key words: recycling, air-sorter, aluminum, copper, home appliances