3D image analysis characterization of wastewater sludge extrudates submitted to convective drying

Conference (2003, October)

Non destructive measurement of shrinkage, cracks and moisture profiles by X-ray microtomography : application to wastewater sludge convective drying

Scientific conference (2003, September)

Use of X-ray microtomography to determine internal moisture profiles during convective drying of deformable materials

in Saravacos, G.; Maroulis, Z. B.; Krokida, M. (Eds.) et al Proceedings of the European Drying Symposium - EuDrying03 (2003, September)

Les technologies du séchage de boues de station d'épuration

Conference (2003, April)

Multiscale texture characterization of wastewater sludges dried in a convective rig

in Drying Technology (2003), 21(8), 1507-1526

Secondary sludges from two different wastewater treatment plants are conditioned and dewatered in the same way before drying in a lab-scale convective rig at the same operating conditions. Several ... [more ▼]

Secondary sludges from two different wastewater treatment plants are conditioned and dewatered in the same way before drying in a lab-scale convective rig at the same operating conditions. Several techniques are used to characterize the texture of the dried materials over a wide range of scales from nm up to mm. Texture and porosity of the dried products are studied by SEM imaging, nitrogen absorption isotherms (0.5 < d(p) < 50 nm), mercury porosimetry (7.5 nm < d(p) < 150 mum) and X-ray microtomography (spatial resolution= 41 mum). The image analysis of cross-sections reconstructed by microtomography also allows following shrinkage and textural evolution during drying. [less ▲]

3D imaging of the texture evolution during convective drying of soft shrinkable materials

Poster (2002, August)

Use of X-ray microtomography to follow the convective heat drying of wastewater sludges

in Drying Technology (2002), 20(4-5), 1053-1069

X-ray microtomography is proposed as a new tool to investigate the evolution of size, shape and texture of soft materials during a drying operation. This study is focused on the drying of mechanically ... [more ▼]

X-ray microtomography is proposed as a new tool to investigate the evolution of size, shape and texture of soft materials during a drying operation. This study is focused on the drying of mechanically dewatered sludges from a secondary wastewater treatment. The shrinkage phenomenon is shown to play a crucial role in the control of the drying process. The shrinkage curves are determined by analysing the shape and size of cross sectional microtomographic images of sludge extrudates at different levels of drying. The observation of drying and shrinkage curves allows us to determine 3 critical water content values, which define different drying zones where extragranular, intragranular or mixed limitations prevail. When drying is externally controlled. the decrease of the drying rate observed during experiments can be related to the reduction of the external area of the sample, i.e., to shrinkage. When drying is internally controlled, resistances inside the solid govern the process. Between these two extreme situations, the drying rate reduction is the result of both the external area decrease and the development of internal resistances limiting drying. A multizone model is proposed to describe quantitatively these observations. The analysis of the internal texture of the Sludge extrudates reveal, crack formation at the end of the drying process. The onset of crack formation is clearly related to the appearance of internal transfer limitations. i.e., humidity and temperature gradients inside the material. [less ▲]

Texture characterization of ultramacroporous materials using non-destructive methods

in Studies in Surface Science and Catalysis (2002), 158

Image analysis, impedance spectroscopy and X-ray microtomography have been used as non-destructive methods in order to characterize ultramacroporous materials (pore width > 1 mum). These methods are used ... [more ▼]

Image analysis, impedance spectroscopy and X-ray microtomography have been used as non-destructive methods in order to characterize ultramacroporous materials (pore width > 1 mum). These methods are used to investigate the texture of different kinds of materials, i.e., highly oriented polylactide (PLA) foams prepared by freeze-drying, isotropic polyolefin foams prepared by thermal degradation of a chemical foaming agent and convective heat dried wastewater sludges. The image analysis of SEM micrographs recorded at different magnifications gave information on the pore size distribution and pore morphology. Impedance spectroscopy was used to investigate the transport properties of the three-dimensional porous matrices by measurement of the water ionic conduction. Finally, 3D image reconstruction from 2D cross-sections obtained by X-ray microtomography allowed visualizing the pore structure. [less ▲]

Use of X-ray microtomography to follow the convective heat drying of wastewater sludges

in Proceedings of the 6th World Congress of Chemical Engineering (2001, September)

Étude par microtomographie aux rayons X du retrait associé au séchage convectif d'une boue

in Boudrant, J.; Pons, M.-N. (Eds.) Récents progrès en génie des procédés N°78 Vol.15 2001 : visualisation, image, modélisation (2001, May)