Demonstration of creep during filtration

Morten Lykkegaard Christensen, Thomas Vistisen Bugge, Anders Løvenbalk Kirchheiner, Kristian Keiding

Publikation: Konferencebidrag uden forlag/tidsskriftPosterForskning

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Resumé

The classical filtration theory assumes a unique relationship between the local filter cake porosity and the local effective pressure. For a number of compressible materials, it has however been observed that during the consolidation stage this may not be the case. It has been found that the production of filtrate also depends on the characteristic time for the filter cake solids to deform.

This is formulated in the Terzaghi-Voigt model in which a secondary consolidation is introduced.
The secondary consolidation may be visualized by plots of the relative cake deformation (U) v.s. the square root of time. Even more clearly it is demonstrated by plotting the liquid pressure at the cake piston interface v.s. the relative deformation (to be shown). The phenomenon of a secondary consolidation processes is in short called creep.
Provided that the secondary consolidation rate is of the same magnitude as the primary consolidation (defined by the hydraulic retardation), the creep phenomenon may occur during filtration. This will lead to Ruth's plots characterized by a concave with two (more or less) distinct slopes. The slopes are defined by the relationship between the porosity and the hydraulic resistance before and after the collapse of the solids structure. This has been observed and modelled for dewatering experiments with activated sludge. It will be argued that although a strong resemblance between blinding and creep exists, these two effects may readily be distinguished by virtue of their dependency of the solid content. Finally a comment on the problem of the scaling of soft materials will be given, in which it will be suggested that the scaling problems may well be related to the existence of creep.

OriginalsprogEngelsk
Publikationsdato2007
StatusUdgivet - 2007
BegivenhedEuropean Congress of Chemical Engineering - København, Danmark
Varighed: 16 sep. 200720 sep. 2007
Konferencens nummer: 6

Konference

KonferenceEuropean Congress of Chemical Engineering
Nummer6
LandDanmark
ByKøbenhavn
Periode16/09/200720/09/2007

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creep
consolidation
porosity
hydraulics
dewatering
activated sludge
liquid
experiment
material
filter cake

Citer dette

Christensen, M. L., Bugge, T. V., Kirchheiner, A. L., & Keiding, K. (2007). Demonstration of creep during filtration. Poster præsenteret på European Congress of Chemical Engineering, København, Danmark.
Christensen, Morten Lykkegaard ; Bugge, Thomas Vistisen ; Kirchheiner, Anders Løvenbalk ; Keiding, Kristian. / Demonstration of creep during filtration. Poster præsenteret på European Congress of Chemical Engineering, København, Danmark.
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Christensen, ML, Bugge, TV, Kirchheiner, AL & Keiding, K 2007, 'Demonstration of creep during filtration' European Congress of Chemical Engineering, København, Danmark, 16/09/2007 - 20/09/2007, .

Demonstration of creep during filtration. / Christensen, Morten Lykkegaard; Bugge, Thomas Vistisen; Kirchheiner, Anders Løvenbalk; Keiding, Kristian.

2007. Poster præsenteret på European Congress of Chemical Engineering, København, Danmark.

Publikation: Konferencebidrag uden forlag/tidsskriftPosterForskning

TY - CONF

T1 - Demonstration of creep during filtration

AU - Christensen, Morten Lykkegaard

AU - Bugge, Thomas Vistisen

AU - Kirchheiner, Anders Løvenbalk

AU - Keiding, Kristian

PY - 2007

Y1 - 2007

N2 - The classical filtration theory assumes a unique relationship between the local filter cake porosity and the local effective pressure. For a number of compressible materials, it has however been observed that during the consolidation stage this may not be the case. It has been found that the production of filtrate also depends on the characteristic time for the filter cake solids to deform. This is formulated in the Terzaghi-Voigt model in which a secondary consolidation is introduced.The secondary consolidation may be visualized by plots of the relative cake deformation (U) v.s. the square root of time. Even more clearly it is demonstrated by plotting the liquid pressure at the cake piston interface v.s. the relative deformation (to be shown). The phenomenon of a secondary consolidation processes is in short called creep. Provided that the secondary consolidation rate is of the same magnitude as the primary consolidation (defined by the hydraulic retardation), the creep phenomenon may occur during filtration. This will lead to Ruth's plots characterized by a concave with two (more or less) distinct slopes. The slopes are defined by the relationship between the porosity and the hydraulic resistance before and after the collapse of the solids structure. This has been observed and modelled for dewatering experiments with activated sludge. It will be argued that although a strong resemblance between blinding and creep exists, these two effects may readily be distinguished by virtue of their dependency of the solid content. Finally a comment on the problem of the scaling of soft materials will be given, in which it will be suggested that the scaling problems may well be related to the existence of creep.

AB - The classical filtration theory assumes a unique relationship between the local filter cake porosity and the local effective pressure. For a number of compressible materials, it has however been observed that during the consolidation stage this may not be the case. It has been found that the production of filtrate also depends on the characteristic time for the filter cake solids to deform. This is formulated in the Terzaghi-Voigt model in which a secondary consolidation is introduced.The secondary consolidation may be visualized by plots of the relative cake deformation (U) v.s. the square root of time. Even more clearly it is demonstrated by plotting the liquid pressure at the cake piston interface v.s. the relative deformation (to be shown). The phenomenon of a secondary consolidation processes is in short called creep. Provided that the secondary consolidation rate is of the same magnitude as the primary consolidation (defined by the hydraulic retardation), the creep phenomenon may occur during filtration. This will lead to Ruth's plots characterized by a concave with two (more or less) distinct slopes. The slopes are defined by the relationship between the porosity and the hydraulic resistance before and after the collapse of the solids structure. This has been observed and modelled for dewatering experiments with activated sludge. It will be argued that although a strong resemblance between blinding and creep exists, these two effects may readily be distinguished by virtue of their dependency of the solid content. Finally a comment on the problem of the scaling of soft materials will be given, in which it will be suggested that the scaling problems may well be related to the existence of creep.

M3 - Poster

ER -

Christensen ML, Bugge TV, Kirchheiner AL, Keiding K. Demonstration of creep during filtration. 2007. Poster præsenteret på European Congress of Chemical Engineering, København, Danmark.