Pumping of dewatered sludge: Slipping or flowing behavior?

Baudez, Jean-Christophe; Megnien, J.C.; Guibelin, E.

doi:10.1016/j.cej.2016.03.071

Cited by 7 publications

(2 citation statements)

References 10 publications

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“…All these structural and textural changes impact sludge flowability and raise severe technical issues for handling, pumping and conveying the sludge, in the dryer itself but more often in the whole sludge processing line. But despite this, only few publications are devoted to the rheological characterization of paste-like and plastic sludge, mainly because of the difficulties to carry out relevant measurements [13][14][15][16][17]. Recently, Mouzaoui et al [18] succeeded to investigate the rheological behaviour of sludge up to its plastic limit (TS=43 wt.…”

Section: Introductionmentioning

confidence: 99%

Rheological characterization of sludge in divided granular-like and pasty states using a granular rheometer

et al. 2021

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Structural changes during sludge treatments impact flowability and raise severe technical issues. In this study, the sludge consistency is analysed using the thread rolling test.Transition from pasty to granular-like material occurs at a total solid (TS) content of 43 wt. %. A granular rheometer is used to characterize sludge's flowability over a wide range of TS content. The typical powder-like behaviour is recorded whatever the TS contents. All the shear stresses/consolidations curves exhibit a linear increase, highlighting the contribution of frictional interactions. Fitting the Mohr-Coulomb failure criterion to these curves emphasizes a substantial rise of frictional interactions from 43 wt.%. Flow functions are determined from the Mohr's circle stress analysis. According to the classification of powder flowability, sludge behaviour is analogous to that of very cohesive powders for 25.5 < TS < 43 wt.% while for lower and higher TS contents, the material behaves like cohesive powders.

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Section: Introductionmentioning

confidence: 99%

Rheological characterization of sludge in divided granular-like and pasty states using a granular rheometer

et al. 2021

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“…Until now the literature mostly focused on the characterization of the rheological behavior of sludges at low (TS<4%) and moderate (4 < TS<17%) solid concentration (Baroutian et al, 2013;Baudez et al, 2013;Dong et al, 2011;Eshtiaghi et al, 2013;Farno et al, 2014;Jiang et al, 2014;Keiding et al, 2001;Lolito et al, 1997;Ma et al, 2014;Manoliadis and Bishop, 1984;Moeller and Torres, 1997;Mori et al, 2006;Pevere et al, 2009;Ratkovich et al, 2013;Ruiz-Espinoza et al, 2012;S egalen et al, 2015;Wang et al, 2016Wang et al, , 2012. Limited attention was paid on pasty and highly concentrated sludge mainly because of the difficulties to carry out relevant measurements (Agoda-Tandjawa et al, 2013;Battistoni, 1997;Baudez et al, 2016;Baudez and Coussot, 2001;Chaari et al, 2003;Charlou, 2014;Jiang et al, 2014;Liang et al, 2017). Indeed, as the TS content increases, dominating interactions move from a lubricated regime (indirect contacts) to a frictional regime (direct contact), leading to dilatancy (Bagnold, 1966;Jaeger and Nagel, 1992;Phillips and Davies, 1991;Sosio et al, 2007;Van Damme et al, 2002) and fractures (Baudez and Coussot, 2001;Chaari et al, 2003;Coussot, 2014).…”

Section: Introductionmentioning

confidence: 99%

Experimental rheological procedure adapted to pasty dewatered sludge up to 45 % dry matter

et al. 2018

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Wastewater sludge are characterized by complex rheological properties, strongly dependent on solids concentration and temperature. These properties are required for process hydrodynamic modelling but their correct measurement is often challenging at high solids concentrations. This is especially true to model the hydrodynamic of dewatered sludge during drying process where solids content (TS) increases with residence time. Indeed, until now, the literature mostly focused on the rheological characterization of sludge at low and moderate TS (between 4 and 8%). Limited attention was paid to pasty and highly concentrated sludge mainly because of the difficulties to carry out the measurements. Results reproducibility appeared to be poor and thus may not be always fully representative of the effective material properties. This work demonstrates that reproducible results can be obtained by controlling cracks and fractures which always take place in classical rotational rheometry. In that purpose, a well-controlled experimental procedure has been developed, allowing the exact determination of the surface effectively sheared. This surface is calculated by scattering a classical stress sweep with measurements at a reference strain value. The implementation of this procedure allows the correct determination of solid-like characteristics from 20 to 45% TS but also shows that pasty and highly concentrated sludge highlight normal forces caused by dilatancy. Moreover the surface correction appears to be independent of TS in the studied range.

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