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Heat Exchanger Fouling and Cleaning – 2011 June 05 - 10, 2011
Influence of soluble polysaccharides
on the adherence of particulate soils
Y. Touré, P.G. Rouxhet, C.C. Dupont-Gillain and M. Sindic
II- Experimental procedures
Presentation outline
III- Results and discussion
I- Introduction
IV- Conclusion
I- Introduction
Who is concerned ?
• Particulate soils• Microorganisms
Why ?
The cleaning efficiency influences:
• final quality of the products,• absence of cross-contaminations,• batch integrity.
Background
Understanding the interactions in order to :
• reduce equipment fouling,
• reduce interruptions of production process for cleaning,
• improve the efficiency of cleaning and disinfection,
• develop easy-to-clean surfaces.
I- IntroductionBackground
Study of soluble macromolecules associated with a suspension of particles:
• may give practical information on the interaction of surface nature and particle surface properties
• may give an insight into the physico-chemical mechanisms involved
• may clarify the role of the soluble macromolecules involved in particles adherence
• may open the way to designing and evaluating easy-to-clean surfaces
I- IntroductionBackground
Assess the influence of soluble polysaccharides on particulate soils adhesion
Improve:
• understanding of mechanisms affecting soiling
• cleanability
I- IntroductionObjectives
Material
Model of soluble polysaccharide: dextran from Leuconostoc mesenteroides; PM: 500 000 Da
Model of surfaces :
• glass (hydrophilic),
• polystyrene (hydrophobic)
Model of particulate soils : quartz (10-30µm)
Surfaces
PolystyreneGlass
Immersion dextran 80mg/l, 1h
Immersion (RBS50 2% à 50°C), 10 min
Sonication, 10min + MQ rinse
Washing, alcohol + immersion, 30 min + MQ rinse
Immersion, piranha mixture 10min + MQ rinse
Fouling
Drying, nitrogen
Redrying, nitrogen
Conditioned ?
No
Yes
Substrate pretreatment
Yes
Quartz particles (10-30µm)
Suspension à 15% without dextran)
Suspension (15%) with dextran (80 mg/l)
3 cycles , washing-decantation (MQ) – supernatant elimination
surfaces pretreated fouling
Suspension (15%) reconstitution
Gentle agitation
Storage, 72 h , 4°C
Dextran present ?
Yes or no
Suspension (15%) with dextran and washed
Soil preparation andtreatment
FLOW
Radial-flow cell (90 ; 190 ; 390 ml/min)
Drying, 30 min in dark, 19 ± 5°C, 39% H
Picture I
Cleaning method
Excel
Drying after cleaning
Pretreated surfaces
Drying, 30 min in dark, 19 ± 5°C, 39% H
OK ?
Soiling
LUCIAResult
Particulate soils
Yes
No
Radial-flow cell (90 ; 190 ; 390 ml/min)
Picture II
MATLAB
picture I
Data processing
Methods of characterization
• Contact angle
• Scanning electron microscopy (SEM)
• Individual size measurements
• Size measurements on a large population
Wetting properties
Contact angles on the substrates in the indicated state
Glass ≠ Polystyrene, whatever substrate treatment
Histograms (% in number) of the lateral size of the soiling entities formed on glass and polystyrene (equivalent diameter of the contour)
0
5
10
15
20
25
30
35
40
45
0 10 20 30 40 50 60 70 80 90
Heig
ht (µ
m)
Eqdiameter (µm)
Polystyrene Glass
Height of the soiling entities formed on glass and polystyrene plotted as a function of their lateral dimension (equivalent diameter of the contour)
• Height and lateral size, larger on polystyrene than glass
• No distinction between samples involving the same substrate
NB: Larger population, density • glass: 51±4 drops/mm2, • polystyrene: 33±4 drops/mm2
D50% were:• 30µm on glass,• 55µm on polystyrene
• Adhering much more firmly on glass compared to polystyrene
• Substrate influence: polystyrene with dextran increased slightly the adherence, while the opposite was observed with glass
• Influence of particles conditioning: no effect on adherence, whatever substrate and particles are conditioned or not with dextran.
Critical detachment radius
Bare surfaces surfaces with dextran Quartz without dexran
Quartz with dextran Quartz with dextran and whased
IV- Conclusion
• Surface hydrophobicity influences aggregates morphology and adherence.
study of wider range of concentrations is in progress
• Presence of dextrane (80mg/L) :
- Conditioning polystyrene substrate: slightly increases the adherence
- Conditioning glass substrate: slightly decreases
- Conditioning powder…presence in the suspension: no effect