The now available second part of a report related to the importance of deep bed filtration during kieselgur filtration deals with the impact of particle size distribution properties of different kieselguhr varieties on particle separation in the filter cake. For these purposes a beer sample with bimodal particle size distribution is filtered using different kieselgur varieties. Furthermore, kieselguhr samples are being modified regarding their particle size distribution by using upcurrent classifying and are also used in the filtration study. The analysis resulted in a high differentiation of particle size distribution of the samples. The poorly filterable beer shows a bimodal particle size distribution with two peaks in the range of 0.8 mum and approx. 6 mum. The well filterable beer shows a peak in the range of 6 mum (characteristic particle size of yeast cells). It can be shown that particles of different particle size can be separated from beer using different mechanisms of kieselguhr filtration: via surface filtration and via deep bed filtration. Particle size distribution and surface condition of kieselguhr impact the separation process. This study is a continuation of a joint project of the TU Bergakademie Freiberg with the Freiberger Brauhaus AG.

The mechanical processing technology differentiates filtration processes according to their working principles by Surface and deep filtration (1). Cake filtration is the process which in the case of the filter cake takes over the job of the filter medium in the course of the process and is classified as surface filtration and as such the usual models (1, 2, 3, 4) hake been studied. However. the authors admit that in this case both working principles can be super-imposed. The kieselguhr filtration of beer is considered to he deep filtration, although the proportion of deep filtration is only given little consideration in literature. Deep filtration generally does not play any role (5, 6, 7) when determining filtration processes. In a joint project of the Technical University Mining Academy Freiberg and the Freiberger Brauhaus AG the significance of deep filtration for kieselguhr filtration of beer has been examined more closely.

Le genie des procedes mecaniques differencie le procede de filtration suivant le principe d'action en filtration superficielle ou filtration en profondeur (1). Dans la filtration sur gâteau, le gâteau occupe la fonction du support pendant le procede. Ce type de filtration est classe dans la filtration superficielle et est considere comme tel dans les modeles courants (1, 2, 3, 4). Les auteurs considerent toutefois que les deux principes peuvent se superposer. La filtration sur kieselguhr de la biere est consideree comme filtration sur gâteau. La litterature porte peu d'attention sur la filtration en profondeur. Pour l'etablissement de procedes de filtration, la filtration en profondeur n'a souvent aucun role (5, 6 ,7). Dans un projet commun avec l'Academie de montagne de Fribourg et le Brauhaus de Freiberg S.A., on a examine de plus pres l'influence de la filtration en profondeur de la filtration sur kieselguhr de la biere.