22-03-2014, 03:45 PM
Optimised technologies for cryogenic grinding
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Abstract
The production of finest powders of viscoelastic and plastic materials is often very energy consumptive and therefore
expensive or even not possible at ambient temperatures. At low temperatures, many materials become brittle so that they can be
grinded more effectively. To achieve these temperatures, the materials are presently cooled with liquid nitrogen (lN2), which is
followed by high operation costs.
At Fraunhofer UMSICHT, a low-temperature fine-grinding plant in technical scale was erected for research. Investigations
for optimisation of cooling equipment resulted in the development of an innovative technology based on cooling technology.
With this technology, the usage of lN2 could be dramatically reduced.
The contribution presents some results of our research in the fields mentioned above. A discussion of the new developments
compared to the established techniques will complete the presentation.
D 2004 Elsevier B.V. All rights reserved.
Introduction
Fine grinding or comminution gains increasing
importance. This is reflected in the extensive trend
towards fine structuring of solid materials and the
rapid spreading of research disciplines like micro,
nano, and surface technologies. Whereas the state of
the art of fine grinding technology for brittle materials
is very high, thermoplastic, elastic, or fibrous materials
cannot yet be ground as efficiently as brittle materials.
Calculation of lN2 consumption
The heat to be discharged at cryogenic grinding is
composed of heat, which has been introduced by the
̇ feed) and the heat introduced by the drive
product (Q
̇ mill), provided that the grinding
capacity of the mill (Q
air flow required for the operation of the mill is met by
the condensing nitrogen alone.