| 摘要 |
<p>Comminuted salvaged rubber is heated to the reclaiming temperature in a two-stage process such that part of the overall heat required is introduced by way of microwave heating and the remainder by way of convectional heating, e.g. by way of a heating screw. The material preheated during the first stage is tranferred to the second stage in such a way that the position of all the particles relative to one another is maintained with as little change as possible. Since the temperature profile characteristic of microwave heating shows a maximum in the interior and a minimum at the periphery, whereas that of convectional heating is just the reverse, the temperature distribution within the material can be evened out to a great extent by combining these two different methods of heating. Since it is no longer necessary in this case to heat the material to such an extent convectionally, it is possible to avoid caking and the formation of deposits, and thus to considerably improve the quality of the reclaimed rubber. Instead of the self-cleaning double-screw apparatus with intermeshing helices it is possible to use single-screw heat exchangers (single-helix hollow-flight screw heat exchangers). Single-screw apparatuses have the advantage, among others, that screw blades of rectangular cross-section can be employed, that guarantee a more uniform heat supply to all parts of the material being treated than curved ones do.</p> |
