筛分机械中潮湿粒状材性质

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筛分机械中潮湿粒状材性质Physicochemical Problems of Mineral Processing， 42 (2008)， 195210
Fizykochemiczne Problemy Mineralurgii， 42 (2008)， 195210
Piotr Wodziński
CERTAIN PROPERTIES OF HUMID GRANULAR
MATERIALS
Received May 15， 2008; reviewed; accepted July 31， 2008

This study deals with the properties of humid granular materials. The processes involving these mate
rials are very frequently encountered under industrial conditions because in fact the processing of
completely dry materials does not exist. Water vapour is present in the air under any conditions which
means a certain amount of moisture in the granular bed. A general friction coefficient of granular ma
terials has been proposed as contributing to a moisture influence on processing. The friction coeffi
cient constitutes a basic independent variable encompassing an impact of moisture on the behaviour
of a humid granular material in the mechanical process. Furthermore， the function of outflow has
been proposed as an important analyticalempirical parameter to describe the processing of solids.

key words: screening， friction in granular material， granular material， humidity， water capacity
INTRODUCTION
It must be mentioned that dry granular materials do not exist. A certain portion of a
granular material even after its removal from a drier constitutes a twophase solid
liquid system because it is exposed to water vapour present in the air. Hence， analys
ing a mechanical (dry) process with a granular material， e.g. screening， we deal with
such a small amount of moisture that the granular material behaves as if it were dry
though actually it contains some moisture. It is an appropriate increase in a moisture
content in the granular material that influences its behaviour in the mechanical proc
ess.
Thus it is crucial to consider a moisture content in a granular material， in particular
in the case of such mechanical processes as screening or proportioning. This study

Technical University of Lodz， Faculty of Process and Environmental Engineering， Department of
Process Equipment， Institute of Material Classification， wodzinsk###wipos.p.lodz.pl