Zur Verfestigung von Schüttgütern – Mikroprozesse und Kinetikmodelle

Abstract

Storage tanks are important elements of a self‐operating closed processing system. The reliability and availability of storage equipment essentially depends on the flow behaviour of particulate solids in storage containers. A wide residence time distribution (i.e. too long a storage time at rest) in silos, bunkers or transportation containers, respectively, can lead to the hazardous problem of so‐called “time consolidation” of particulate solids. During this hardening process, solid bridges are forming with resulting solidification and solid properties of bulk material. In principle, there are four main physico‐chemical effects in bulk materials storing and handling which can produce solid briding between the particle contacts due to crystallisation, chemical reactions, solidification of high‐viscous bonding agents and sintering. Generally, new adhesion force based models are presented to describe the consolidation kinetics of particulate solids. Preliminary solutions of kinetic model equations are discussed and compared with new test results and practical conclusions are drawn concerning the reliable processing, storage and transportation of bulk materials.

The Effect of Process Conditions on Powder Flow Properties for Slow Flow Regimes

“…1. A common representation of flowability is presented in terms of a plot of f c vs σ 1 , referred to as flow function, which can be compared to the flowability class bounded by constant values of the flow factor, ff c = σ 1 /f c , according to the classification proposed by Jenike (1964) and completed by Tomas and Schubert (1985) (Fig. 2).…”

Development of a new dem contact model for hygroscopic bulk solids

“…On the basis of the determined liquid-bridge radii and the storage time to be investigated, the bond radii R B can be calculated using the time parameter t 63 according to Tomas [11]:…”

Simulation of sheared, caking powder

“…This time dependence describes the formation of a solid bridge for example by a chemical reaction or by crystallization of solute (see [5]). In general it does not apply for sintering processes, where the identity of particles gets lost after coalescence.…”