Copyright Cl IF AC Intelligent Assembly and Disassembly, Bled, Slovenia, 1998 RECYCLING OF OUlWORN TYRES BY GRINDING AT NORMAL TEMPERATURE A. Tymanok*, B. and D. Goljandin* * Tallinn Technical University ** Tallinn Technical and Cybernetica Ltd.. Tal/inn Abstract: The massive amount of used automobile tyres is a serious problem, causing environmental pollution. In addition the need for recycling this valuable malerial arises. However. no universal solulion exists. This paper reviews the melhods of ulili" .. 1tion. with special emphasis on the CUlling methods of tyres. Three consecutive steps for tyre disintegration arc described, including three different machines designed for this purpose. The CUlling mcchanics is described theoretically based on our experiments. Rccommendations for industrial tyre processing are presented. Copyright © 19981FAC Keywords: lyre recycling. rubber processing, rubber powder size-grading, sepamlive grinding. 1. INTRODUCTION The bulk of outworn automobile tyres is huge, c1ullering up and polluting the environment. Because of lack of suitable technology, only a total of about 17% is utilized (Technical message, 1994). Almost all utilization methods require the preliminary comminution of tyres, i.e., reducing their size, except when burning in cement furnace. The finer the ground rubber, the more reuse applications it has. The destruction of car and truck tyres is carried out in three ways: • by cryogenic destruction (Technical message, 1991). In this case the consumption of liquid nitrogen is more than 1 kg per I kg of rubber, power consumption 150-185 kWh; • by detonation. The tyre is loaded by some explosive substance of about 20 % of its Illass and then exploded. Thus, the explosion wave crushes the tyre, which is sometimes used when utilizing extra large tyres (Kovtun and Drozdovski, 1991); 123 • by means of different mechanical methods. In the rubber industry, a combination of rolling mill and disc mill is used (system Unimax), where the particles of 1-3 nun are obtained, consuming energy 400-600 kWhlT. Some applications are based on scraping of the tyre by sharp-cogged disks (Fiilpcn and Jacobs, 1988), on cutting (Klepsch, 1993), on Wc.1ring by a grindstone-like device (Seuma, 1993), on pressure and shifting (Enikolopov, et al., 1989). None of them has made a brc.1kthrough, and it is difficult to evaluate their energy effeciency from the patent documentation. Mechanical comminution of rubber needs a high rate of energy, which is the main factor, showing non-profitability of recycling of the tyre material. At Tallinn Technical University and at Cybernetica Ltd. Tallinn investigations concerning the mechanics of disintegrating rubber, in particular, that of Ihe tyre material, have been carried out. Having obtained some fundamental resulls, there have been designed and tested some special CUlling tools and invenled different grinding machines, aiming at grinding inlacl lyres to rubber powder