Monitoring Rheology as a Tool for Measuring the Effective Shear - - PowerPoint PPT Presentation
Monitoring Rheology as a Tool for Measuring the Effective Shear Rate in the Bubble Columns . Presenter: Veena Bobade V.Bobade 1 , J.C. Baudez 2 , Geoffrey Evans 3 , N. Eshtiaghi 1 1 RMIT University, Australia 2 LIST, Luxemburg. 3 The
Presenter: Veena Bobade V.Bobade1, J.C. Baudez2, Geoffrey Evans3, N. Eshtiaghi1 1‐RMIT University, Australia 2 LIST, Luxemburg. 3 The University of Newcastle, Australia.
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Industrial Applications Importance of Aeration Aerated Chocolate Increases the taste and Mouth feel Aerated Food Provides new texture, reduces caloric density and increases satiety. Aerated Gels Aeration decreases the hardness and increases the structural strength of gels. Aerated Pharmaceutical & Cosmetic products Aeration makes its lighter and increases the foam texture and improves the quality of product. Aerated Sludge Improves mixing in the reactor and increases the efficiency of the process (75% of the energy is consumed by the Aeration)
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understand the relationship between changes in physicochemical properties of municipal waste activated sludge and with the stress induced by gas injection.
0,1 1 10 100 1000 10000 0,0001 0,001 0,01 0,1 1 10 100 Viscosity, (Pa.s) shear rate, (1/s) without gas with 3 LPM @20 mins with 3 LPM @40 mins
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Gas injection and time
injection has no impact on viscosity
Impact of gas injection on solid like behaviour of 4.2%WAS at 2 gas flow rate
0,01 0,1 1 10 0,01 1 100 Strain, (%) Step time, (s)
At no gas injection At 0.5 LPM of gas injection At 1.5 LPM of gas injection
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10 100 5 50 500 Storage Modulus G‘ and Loss Modulus G" , (Pa) Time, (s)
G' at no gas injection G" at no gas injection G' at 0.5 LPM of gas injection G" at 0.5 LPM of gas injection G' at 1.5 LPM of gas injection G" at 1.5 LPM of gas injection
Creep test Time sweep Gas injection decreases the elasticity of the sludge. Gas injection impacts
structure
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0,001 0,01 0,1 1 10 0,001 0,01 0,1 1 10 100 Strain, (%) Step time, (s)
with 0.5 LPM of gas at 0.89 Pa with 1 Pa stress for un‐aereated sludge sample
Creep test
0,001 0,01 0,1 1 10 0,001 0,01 0,1 1 10 100
Strain,(%) Step time, (s)
with 1.5 LPM of gas at 0.89 Pa.
with1.2 Pa stress for un‐aereated sludge sample
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0,1 1 10 100 1000 3 30 300 Storage modulus (G') & Loss Modulus (G"), Pa. Time, (S)
G' at 0.5 LPM, and 0.08% Strain G" at 0.5 LPM, and 0.08% Strain G" without gas injection at 0.2% Strain G" without gas injection at 0.2% strain
10 100 5 50 500 Storage Modulus (G') & Loss Modulus (G"), Pa. Time, (s)
G' at 1.5 LPM, and 0.08% strain G" at 1.5 LPM, and 0.08 % Strain G' without gas injection at 0.3% strain G" without gas injection at 0.3% strain
Time sweep
creep test Gas Flow rate (LPM) applied stress for aerated sludge (pa) applied stress for un-aerated (Pa) stress imposed by the gas (pa) 0.5 0.89 1 1-0.89 = 0.11 1.5 0.89 1.2 1.2-0.89 = 0.31 Time sweep test Gas Flow rate (LPM) applied strain for aerated sludge (%) applied strain for un- aerated sludge (%) strain imposed by the gas (%) Equivalent stress imposed by the gas (Pa) = [(%strain)/100] x G* 0.5 0.08 0.2 0.2-0.08= 0.12 (0.12/100)*144 = 0.17 1.5 0.08 0.3 0.3 – 0.08= 0.22 (0.22/100)*144 = 0.31
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Proved that gas injection imposes extra shear on sludge and changes its rheological behaviour
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Gas flow rate (L/min) Gas velocity (m/s) Stress imposed, (N/m2) 3.00% 4.00% 5.00% 5.50% 1 0.00182 4.4564 2.67855 2.42791 1.04614 3 0.00545 7.7987 5.3571 3.884656 3.13842 5 0.00909 10.0269 7.1428 4.85582 4.18456 7 0.0145 14.4833 10.7142 9.71164 5.2307
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P < 0.05 & R Square = 0.89 A simple model based on sludge concentration and gas velocity is developed to predict the stress induced by gas injection
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5 10 15 20 25 30 35 40 6 8 10 12 14 16 18 20 Shear rate, (1/s) Shear stress ,(Pa)
(
shear rate induced by the
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Reference Equation used (Nishikawa, Kato et al. 1977)
(Henzler 1980)
(Babaei, Bonakdarpour et al. 2015, Babaei, Bonakdarpour et al. 2015)
(Schumpe and Deckwer 1987)
Effective shear rate formula used in the literature
A.Zeta Potential B.Soluble COD C.Total Suspended Solids 1 4
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1 2 3 4 5 6 7 8 Zeta Potential,(mV) Gas Flow rate, (L/min) 3% ss 4% ss 5% ss 5.5% ss
C = Fitting parameter = 2.12, (m2/N)
15 20 25 30 35 40 45 50 55 0,002 0,004 0,006 0,008 0,01 0,012 0,014 Suspended solids, (mg/l) Gas velocity, (m/s)
3% 4% 5% 5.50%
a = Fitting parameter = 2.01, (m2/N) Gas velocity (m/s) sCOD (mg/l) 3%Ts 4%TS 5% TS 5.5%TS 4860 5250 5390 5830 0.00182 5340 6030 5750 6190 0.00546 6060 6480 5900 6350 0.0091 7260 6540 6600 6590 0.01274 7410 7230 7070 7470 b = Fitting parameter = 2.75, (m2/N)
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1. Gas injection has negligible impact on viscosity of sludge 2. Gas injection imposes extra shear on sludge was proved 3. Developed a simple equation based on total solids and gas velocity to understand the stress imposed whish is proportional to the shear rate in the bubble column. 4. Stress imposed by gas injection showed a linear relation to percentage change in physical properties of sludge and indicated that rheology can monitor the changes in sludge physical properties
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1. "Impact of gas injection on the apparent viscosity and viscoelastic property of waste activated sewage sludge." Water Research 114: 296-307 (2017). 2. “Influence of gas injection on viscous and viscoelastic properties of Xanthan gum.”. Water Research 134: 86-91 (2018) 2. “Relationship between changes in physicochemical properties of municipal waste activated sludge and its rheology during gas injection”. (Manuscript under review with Water Research )
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I wish to acknowledge
research work.
providing scholarship to carry out the research. 1 9
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