Reactive Comminution

Ulrich Hoffmann, Christian Horst and Ulrich Kunz 14.1 

The utilization of mechanical energy in solid transformations can be divided into four clusters  

Integrated Chemical Processes. Edited by K. Sundmacher, A. Kienle and A. Seidel-Morgenstern Copyright 2005 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 3-527-30831-8 

Most of the technical raw materials used in solid reactions are polycrystalhne, and these - when in solid form - undergo a range of modifications during milling. The first observation is the fracture of the solid into smaller pieces. The fracture mechanics are a topic of discussion, and fracture can be divided into two steps, namely crack formation and crack propagation . Depending on the ability of the material to undergo plastic deformation before fracture, either brittle or ductile fracture can be defined  

Steinicke and Linke [17] refer to several microscopic and macroscopic states of mechanically stressed solids. Short time effects can be described by stochastic means or nonequilibrium thermodynamics. Long-lasting effects can be measured by calorimetry. The chemical potential and activity of the stressed solid can be measured depending on the induced defects. These defects include  

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Reverse-flow reactors Reactive distillation Reactive extraction Reactive crystalization Chromatographic reactors Periodic separating reactors Membrane reactors Reactive extrusion Reactive comminution Fuel cells... 

In the future, it is likely that reactive comminution will be used as a tool for the preparation of novel materials and precursors for catalysts, membranes, high-performance ceramics, hydride storage media, raw material for powder metallurgy, and nanoparticles. The emerging applications in organic synthesis reactions and environmental protection will undoubtedly also lead to broader applications. 

In Chapter 14, Hoffmann and colleagues provide a survey on the status and directions of reactive comminution. In this type of process integration, mechanical stress exerted in mills is used to enhance the chemical reactions of solids with fluids. Simultaneously, chemical reactions can generate cracks in solid particles and thereby enhance their comminution. 

Heat-integrated reactors Reactive separations Reactive comminution Reactive extrusion Fuel cells... 

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