The scientific side of cleaning-in-place D. Ian Wilson Department of Chemical Engineering & Biotechnology PMTC 3 rd Annual Knowledge Day 31 August 2017 1
Cleaning & Decontamination SIG 10 2
Linked activities SIG 10 Fluid mechanics of Cleaning and Decontamination www.sig10-cleaning-decontamination.net/ Fouling and Cleaning in Food Processing 2018 The food-water-energy challenge 17-20 April 2018, Lund, Sweden www.lth.se/membranportalen/english/fcfp2018/ 3
Two questions Q1 Why clean? Q2 How clean is clean? to purge to prevent cross-contamination to restore performance to inhibit microbial growth or deposit accumulation 4
Cleaning is all about surfaces and s Surface 3 Surface 4 Soil 1 Soil 2 5
Interface engineering fluid- interactions fluid/solution (usually water) - interactions 6
How physical scientists see cleaning fluid mechanics normal stresses liquid adhesion mass transfer heat transfer shear stresses surface chemistry surface morphology cohesion: rheology, materials 7
Sinner s Circle The interaction of key process parameters www.glasswashing.biz 8
Sinner-gy fluid mechanics normal stresses liquid adhesion shear stresses etc. surface chemistry rheology 9
Sinner s circle is about cleaning rates Think of reaction kinetics dx dt k C Let X be the extent of cleaning t X k, 0 T, V ph C dt 10
The big question: What is the reaction? There are many different s There are a number of cleaning mechanisms The mechanism determines the chemistry and forces to use 11
the Fryer & Asteriadou cleaning map EHEDG, based on Fryer & Asteriadou (2009) Trends Food Science & Technology, 20, 225 262. 12
Not all s are equal : nurture vs nature Composite (at what length scale?) Aged? 13
Soil structuring Single layer? Composite (at what length scale?) strength Constant wall temperature Aged? wall surface time T wall temperature surface wall 14
Soil structuring Single layer? strength Constant heat flux Composite (at what lengthscale?) Aged? surface wall time T wall,0 temperature wall surface 15
My matrix of mechanisms Mobile Immobile solution Dissolution Bhagat et al. (2017) Food & Bioproducts Proc, 102, 31-54 16
My matrix of mechanisms Mobile solution Roll-up Solution Bhagat et al. (2017) Food & Bioproducts Proc, 102, 31-54 17
My matrix of mechanisms Mobile Immobile Dissolution solution Erosion solution solution Roll-up 18
My matrix of mechanisms Mobile Immobile solution solution Dissolution Erosion Roll-up solution Peeling solution 19
The science behind the matrix Mobile Immobile Dissolution solution Erosion solution Thermodynamics Mass transfer Cohesion Shear stress Roll-up solution Peeling solution Wetting Buoyancy Adhesion Shear and normal stress 20
Forces Roll-up, erosion and peeling mechanisms all require understanding of the forces imposed on layers the rheology chemistry Self-weight/buoyancy Fluid shear Normal forces t M g 21
Doing cleaning.. 1. Identify 2. Characterise 3. Identify chemistry to use 4. Apply agents 22
How do you apply your cleaning agent? Aqueous cleaning solutions or solvents Mode 1 duct flows Mode 2 free surface flows 23
Mode 1 duct flows The flow rate sets the local velocity Scale up lab/trial results if we know the mechanism (key parameters) Guidelines on mean flow velocities: main uncertainty is chemistry/rheology fluid mechanics normal stresses liquid adhesion shear stresses surface chemistry rheology 24
Mode 1 challenges and opportunities Monitoring Optimisation minimising resources Clever flows Overall cleaning rate /g m -2 s -1 Overall cleaning rate g/m 2 s 0.30 0.25 0.20 0.15 0.10 0.05 flow pulsing steady flow 0.00 50 75 100 125 150 175 Protein Coverage coverage /g 25 m g/m -2 2 25
Knowledge-based CIP Patrick Gordon, 2010 Deposit thickness 40 C ph 10.8 PXPS protease Gordon et al. (2011) Chem. Eng. Res. Des. 26
soak & swell release enzyme rinse off 27
Mode 2 jets and sprays Spray balls Lower jet speeds Nozzles Higher jet speeds
Every man s fluid mechanics More complex fluid mechanics Free surface flows 29
The fluid mechanics of impinging jets nozzle wall R g W Key dimensions: R radial flow zone hydraulic action W wetted width - soaking - modest shear - wetting rate m W 30
Impact on cleaning Horizontal coherent water jet on Xanthan gum/zns fluorescent layers Hydraulic forces Draining film modest hydraulic forces: soaking and time 31
Eo dimensionless W The role of chemistry Detergents Concentration of Tween 20 (surfactant) Flow Little effect on R Large effect on W Removal mechanism Promote detachment Soaking Dimensionless flow rate Wang et al. (2013) Chem Eng. Sci., 88, 79-94 32
Simply use higher flow rates? Break-up long jets q 90 short jets Feldung Damkjaer et al. (2017) Food & Bioproducts Proc, 101, 145-156 33
Tank cleaning in practice: moving nozzles & jets Pictures: Alfa Laval Tank Equipment Inc. 34
Moving along. Cambridge petroleum jelly Xanthan gum/zns Hannes Köhler TU-Dresden 35
Modelling : Predicting shape of cleared region weak strong w c 2 1.52a x 3 k' 3 5 m c 3 v 1 nozzle 1/ 4 a x 36
What I haven t talked about Micro-organisms and biofilms Disinfection Non-liquid technologies Monitoring methods Assurance Scheduling Coatings 37
Summary Cleaning is about interfaces Physical ones Between academic disciplines Identifying the and how it got there is key to removing it Time for lunch (and dishwashing) 38