定在波音場を用いた産業廃棄物分別方法の開発

Abstract

In recent years, more than 10 million tons of industrial wastes are discarded annually. Those wastes are mainly composed of plastic, glass and metals which are the materials massively used in automobiles, electric and electronic products. It is well known that industrial waste contain precious metals like gold and have a great value of reutilization. Therefore, technology to properly separate the waste by their types of subject is very important for recycling industry. In this study, we have developed a new separation method by use of acoustic levitation phenomenon in a standing wave field. Unlike the conventional methods such as centrifugal particle separation or magnetic separation, this method enables to sort subjects by their densities, without relying on other material properties including size, magnetism and weight. First described in this paper is a theoretical analysis of levitation force exerted on an object to derive its trajectory in a standing wave field. It is found that the motion of the object is governed by its density and the strength of acoustic field. Based on this finding, we developed a prototype of separation system with twin-transducers and a belt conveyer. As a result of test to separate a mixture of SiO2 and Fe particles, 62wt% SiO2 is captured at node side while 72wt% Fe is captured at anti-node side. Finally, the prototype is used to repeatedly separate the chipped waste of actual OA equipment. Its density was increased about 150%.