centrifugal fractionation of ultra ne particles by means
TRANSCRIPT
Centrifugal fractionation of ultra�ne particles by means of geometric and material
separation characteristics in a strong centrifugal �eld.
Marvin Winkler*, Hermann Nirschl*
*Institute for Mechanical Process Engineering and Mechanics
Karlsruhe Institute of Technology (KIT); Straÿe am Forum 8, 76131 Karlsruhe
Goals
Fractionation is an important unit operation in solids process engineering and describes the
separation of a collective into several fractions with prede�ned characteristics. The process
makes use of di�erences in the geometric properties (particle size and shape) and materi-
al properties (density, surface functionalization) of a given particulate solid-liquid system to
achieve the desired separation result. The aim of the project is to develop a basic model for
the multi-dimensional fractionation of ultra�ne particles in strong centrifugal �elds based on
experimental measurements. The �eld of application reaches beyond the laboratory scale and
therefore a capable in-situ measuring technique needs to be included in the process. The pursu-
ed optimization in separating e�ciency increases the attractiveness for industrial applications.
On a process engineering scale, tubular bowl centrifuges are suitable for this task as they com-
bine high throughput rates with high centrifugal accelerations.
Particle Systems
Initially the focus lies on tailor-made, carefully synthesized model systems with narrowly distri-
buted property functions of density, grain size and shape. Subsequently, suitable combinations
of mineral, pigment, metal (-oxide) or polymer-based particle systems are to be characterized
and separated into fractions with regard to wider property distributions. Stable suspensions of
easily dispersible solids are suitable for this purpose, which di�er su�ciently from each other
with regard to their characteristic absorption spectra and their sedimentation rate.
Tabelle 1: Overview of particle systems
system substancedensity
/g · ccm−1 shapemean particle size
/µmdistributor
micromer® polysterene (PS) 1.03 spherical 0,1 � 1
sicastar®-red silica (SiO2) 2.0 spherical 0,1 � 1
micromod Partikel-
technologie GmbH
MICAVI-10silica (50%)
aluminium oxide (33%)2.8 tabular 2.8
SILMIKRON 805-10/1 silica (99%) 2.35 angular 0.5
TREMIN 939-600silica (50%)
calcium oxide (47%)2.85 acicular
aspect ratio
(L/D) = 7/1
Quarzwerke GmbH
Methods
In its core, the setup used for the fractionation experiments consists of a high-performance, fast-
rotating tubular bowl centrifuge (GLE, Carl Padberg Zentrifugenbau GmbH, Germany (CEPA)
or a Centrifuge prototype presented in [1], Institute for Mechanical Process Engineering and
Mechanics (KIT)). If a preceding classi�cation step is required, the same process centrifuge
can be used e�ectively as shown in a previous work [2]. The upstream includes a continuous
desagglomeration step (Soni�er 450 D, Branson Ultrasonics Corporation, USA) to ensure the
fractionation of single particles rather than particle compounds. Finally, a quantitative, multi-
wavelength setup via UV-VIS spectrometry (FLAME-S-XR1, Ocean Optics USA) needs to be
implemented in order to determine the particle concentration of multiple components in the
centrifuge over�ow live during operation.
Primary Characterization Techniques
As already mentioned, it is necessary to determine several key factors of each particle system
since they in�uence sedimentation. These include particle size and shape distribution, solid
density and density of the continuous phase respectively. Solids concentration and state of
stabilization are also taken into account. Image analysis using transmission electron microsco-
py provide information on particle shape. Particle size distributions can be measured using a
CPS 24000 disccentrifuge (CPS Instruments, USA). In addition, several conventional measu-
ring techniques (light di�raction, small-angle X-ray scattering, dynamic light scattering) help to
compare, validate and discuss the distribution data. Zeta potential measurements with a Zetasi-
zer Nano ZS (Malvern Panalytical GmbH) are used to analyze the stability of a suspension or a
de�ned fraction. Statements on particle sedimentation can be made by evaluating transmission
spectra generated by a LUMiFuge manufactured by LUM GmbH. In order to determine the
separation e�ciency, the concentration of the �ne fraction is analyzed gravimetrically (o�ine)
and via signal processing of UV-VIS spectra (online).
Graphical Abstract
[1] Manuel Konrath, Julie Goren�o, Nils Hübner, and Hermann Nirschl. Application of magne-
tic bearing technology in high-speed centrifugation. Chemical Engineering Science, 147:65
� 73, 2016.
[2] Manuel Konrath, Ann-Kathrin Brenner, Elias Dillner, and Hermann Nirschl. Centrifugal
classi�cation of ultra�ne particles: In�uence of suspension properties and operating para-
meters on classi�cation sharpness. Separation and Puri�cation Technology, 156:61 � 70,
2015.