Ice Pigging: Economical and Novel Method for Cleaning-In-Place of Food and Dairy Processing Equipment: a Review

Available online at www.ijpab.com Thyarla et al Int. J. Pure App. Biosci. 5 (6): 1132-1138 (2017) ISSN: 2320 – 7051 DOI: http://dx.doi.org/10.18782/2320-7051.2971 ISSN: 2320 – 7051 Int. J. Pure App. Biosci. 5 (6): 1132-1138 (2017) Review Article

Ice Pigging: Economical and Novel Method for Cleaning-In-Place of Food and Dairy Processing Equipment: A Review

Aravind Thyarla1, A. K. Agrawal2, Keerthi Srikanth2*, K. S. Umapati 3 and Suresh Velpula3 1M. Tech Scholar, 2Prof. & Head, Department of Dairy Engineering, College of Dairy Science and Food Technology, C.G.K.V., Raipur, (C.G), India 2Assistant Professor, Department of Dairy Technology, 3Assistant Professor & Head of the Department of Dairy Engineering, College of Dairy Technology, PVNR TVU, Kamareddy, (T.S.), India 3 M. Tech Scholar, Department of Dairy Engineering, SMC College of Dairy Science, AAU, Anand, (G.J), India *Corresponding Author E-mail: [email protected] Received: 11.05.2017 | Revised: 19.06.2017 | Accepted: 26.06.2017

ABSTRACT The effectiveness of cleaning is dependent on „physical action‟ or „force applied‟ by a cleaning solution. Therefore, high turbulent systems are desired for efficient cleaning. For obtaining „physical action‟ at fouled surfaces and smooth flow at normal surfaces, some “smart material” is required that acts like a fluid squeezing through complex geometries but behaves as „tough‟ as it is a solid scraper which cleans the fouled surfaces. The „crushed ice in water‟ or „ice pig‟ is able to achieve many of the desirable characteristics of desired smart material. Ice pigging is an innovative method of removing fouling from topologically complex and demanding ducts. The process involves pumping ice slurry, a mixture of ice particles and liquids containing a freezing point depressant, through the fouled duct. The slurry acts in a similar manner as solid pig, displacing material downstream by applying shear. Hence, mechanical cleaning effect to the duct walls is achieved.

Key words: Freezing Point Depressant, Ice Pig, Ice Particle Size, Ice Slurry and CIP.

INTRODUCTION circulation or by a once thorough mechanical In modern milk processing, cleaning is the cleaning process without dismantling. The primary treatment and this should be carried removal of soil depends on the kind of soil and out immediately after processing work is over. its state, nature of support of soil (surface It is a precondition, for the production of finish) and mechanical action depending on hygienically satisfactory and high quality the velocity of flow, presence of foam etc3. products, that milk and milk product The effectiveness of cleaning is dependent on processing plant is scrupulously clean. Now a „physical action‟ or „force applied‟ by a day, in almost all dairy plants, CIP (Cleaning cleaning solution. Therefore, high turbulent in Place) is used i.e. the plant is cleaned by systems are desired for efficient cleaning.

Cite this article: Thyarla, A., Agrawal, A.K., Srikanth, K., Umapati, K.S. and Velpula, S., Ice Pigging: Economical and Novel Method for Cleaning-In-Place of Food and Dairy Processing Equipment: A Review,

Int. J. Pure App. Biosci. 5(6): 1132-1138 (2017). doi: http://dx.doi.org/10.18782/2320-7051.2971

Thyarla et al Int. J. Pure App. Biosci. 5 (6): 1132-1138 (2017) ISSN: 2320 – 7051 Adequate physical action can be ensured by partially closed valves, pumps, and the selection and utilization of proper pumps contractions/expansions by realigning to provide sufficient turbulence of the cleaning aggregate‟s shapes to fit the shape of solution through the pipelines and equipment equipment. to achieve maximum efficiency1. For obtaining There is no need to change layout of „physical action‟ at fouled surfaces and smooth pipe lines for ice pigging. Ice pigs can easily flow at normal surfaces, some smart material pass through large diameter pipes, bends, is required that acts like a fluid squeezing valves sockets etc. Only limiting thing is that through complex geometries but behaves as ice slurry produces higher pressure drop in the „tough‟ as it is a solid scraper which cleans the pipes when compared to cleaning or fouled surfaces. The „crushed ice in water‟ or disinfecting solutions at the same velocity. „ice pig‟ is able to achieve many of the Properties of Ice Slurry desirable characteristics of the smart material. The main factors in ice pigging intended for The ice pig can traverse through very complex cleaning process are ice fraction, ice particle topologies for cleaning and can recover and size and freezing point depressant separate products. Further, it does not get concentration. Ice fraction can be estimated by stuck, and even if it did, it will be melt into measuring the temperature of the ice slurry water, which can then be easily drained12. solution and initial concentration of freezing Importance of Ice Pigging point depressant9. The size of ice particle Pushing a piston like object through a pipe to mainly depends upon the method employed for clean the pipe walls is known as pigging. In its storage and length of time since its ice pigging, the „pig‟ consists of crushed ice in formation. The particle size increases with water with a freezing point depressant. The time elapsed11. The ice fraction and particle void fraction is carefully controlled so that the size, both contribute to the rheological ice/water mix move like a solid plug in free properties of slurry. The higher the ice flow areas, but is able to flow like a fluid in fraction, the more the pig behaves like a solid, constricted areas12. The ice pig is capable of thus exerting larger cleaning forces on the pipe being injected through a small diameter inlet wall and generating larger pressure drops per and expanding to fill a pipe, which can be up unit length. However, there is also the risk of to 200 times larger in area. This results in blocking the pipe work with larger ice minimum engineering work required on fractions13. existing pipelines to accommodate ice pigging Performance of Ice Pigging 2 as a fouling removal solution . Several trials are performed in food industries It offers to be innovative de-fouling where the ice pigging process provided not technology. The non-Newtonian behaviour of only cleaning of pipes but also resulted in ice pig gives it a special flow characteristic; it efficient product recovery12. In some appears to achieve plug flow whenever it can. investigating trials, the ice pigging has Plug flow means that there is little mixing achieved up to 90% recovery for a viscous through the ice pig. The ice slurry acts in a product at ambient temperature pipe line. manner of displacing material downstream of These trials were carried out over a range of it by applying shear and hence mechanical pipe diameters and lengths 1 cm to 10 cm and cleaning of all surfaces comes into its contact2. up to 100 m in length. It has demonstrated its Why Ice Pigging can be used ability to pass and clean various process Ice pigging is a process for the removal of equipment i.e. inline mixers, extruder, lobe fouling, deposition, dirt particles etc. from the pumps, dosing units and mono pumps2. pipes, ducts, narrow spaces in a pipe or In their experiment on ice pigging2, network of pipes. Ice pig can navigate used four-way manifold to demonstrate the ice obstructions such as bends, T‟s, valves, pig‟s ability to flow through diameter changes Copyright © Nov.-Dec., 2017; IJPAB 1133

Thyarla et al Int. J. Pure App. Biosci. 5 (6): 1132-1138 (2017) ISSN: 2320 – 7051 and multiple paths and successfully scoured fine grain sand, representative of loose small particulate fouling. It has been reported that the largest volume of fouling material approximately 160 kg removed by using the 4.5 Tons of ice slurry. These processes have also been tested on several different pipe materials like cast iron, PVC and stain less steel. In a study, satisfactory cleaning Fig. 1: Variation of ice to brine proportion with properties of ice slurry was reported on temperature (3% NaCl2) different industrial heating units namely plate heat exchanger (Model: C6-SR, Make: The principal effect of the depressant is to Tetraplex) and tube in tube heat exchanger produce an ice-water mixture which is stable (Model: MTC70/W-3, Make: Tetra Spirflo)13. over a range of temperatures. The above figure Modelling of Ice Pigging explains the percentage of ice to brine For cleaning process4, developed a model for variation with temperature for a 3% sodium chloride (NaCl ) solution12. predicting the flow and melting behaviour of 2 It decreases the viscosity while ice slurry passing through stainless steel thermal conductivity of the fluid phase pipelines. However, in a study carried out of increases. It replaces corrosive behaviour of using ice pigs in a plate heat exchanger and acid/alkali solutions used in CIP with gentle tube heat exchanger, it was reported that effect on adjacent metal surfaces. FPD‟s pressure drop increased exponentially with ice prevents agglomeration of ice crystals used in fraction and with the square of the velocity13. CIP by ice pigging. Freezing point depressant Ice slurry, Ice particle size and The Freezing Point Depressants (FPD) is manufacturing 10 added in order to maintain the slurry condition, Peter and Kauffeld , explained ice slurry is preventing the ice particle from fusing together nothing but fine–crystalline ice particles with and forming a solid block of ice. Typically, an average characteristic diameter, which is equal or smaller than 1 mm. Nowadays, sodium chloride is used due to low cost, mostly ice slurries produced by mechanical minimal health and safety implications and scraped type generators, which produces ice small concentrations required. Other FPD‟s are particles of approximately 200 µm size. also used which includes sugar, sorbitol, However, the particle sizes were hydrochloric acid, sodium hydroxide, sodium approximately one to four millimetres before nitrate and poly ethylene glycol. growth occurred. The effect of this crystal The selection of freezing point depressant growth behaviour is that physical properties mainly depends on the ideal solution or are time dependent. Storage and mixing of ice product which is already present in pipeline. slurry lead to a decrease of the rheological The chemicals such as acids, alkali, anti- parameters (the viscosity and the critical shear corrosion and pacifier‟s agents are added as stress) up to 60%. In simple terms, the ice slurry from part of freezing point depressant. This is being pumpable and conforming to different particularly important for materials such as topographies like a liquid, and yet behaves in “yoghurt or curd” where cleanliness and pipe as a solid, providing an enhance shear hygiene are important in determine the safety stress on the pipe walls and therefore more and product stability. efficient cleaning of the pipe walls. Copyright © Nov.-Dec., 2017; IJPAB 1134

Thyarla et al Int. J. Pure App. Biosci. 5 (6): 1132-1138 (2017) ISSN: 2320 – 7051 Controlling and maintaining the ice slurry Mechanical type Ice slurry generator consistency is important. A good quality of ice In mechanical – scraper type ice slurry is subject to Ostwalds ripening where by ice generator, the refrigerent evaporates in a crystals tend to stick together and form a solid double – wall cylinder. Through the inside mass as the ice ages. To overcome these space, bounded by the inner cylinder, the problems a freezing point depressant and water or brine solution flows. In their mechanical agitation is used. experiment2 generated ice pig by circulation of The ice pigging technology requires 5% sodium chloride brine solution through a an ice making facility (Scraped Surface Heat rotating screw, scraped surface ice generator Exchanger), flow analysis unit, storage tank, and stored in a 700 liter stirred tank. and delivery pump, conductivity meters etc. Depending upon the ice fraction required, the The ice is generated with portable water, a ice machine was turned off when a set freezing point depressant, table salt etc. temperature was reached.

Fig. 2: (a) Mechanical scraped surface ice generator, (b) Ice pig

Ice fraction in ice pig for lower temperature applications because the Ice fraction is more important in behaviour of lower freezing point requires a higher the ice slurry. It affects flow behaviour and concentrations of additives or FPD‟s, which rheological properties of ice slurry8. A simple increases the density difference between the and repeatable method is used with a standard liquid phase and the ice particles, except for coffee press (a container with mesh plunger). alcohols and ammonia7. The ice slurry is fully filled in this container The density of ice slurry can have derived as and then mesh plunger is slowly inserted. follows:

Finally, the plunger is pushed slowly ρ = m/ Vi+Vw+Va downwards, until no more travel can be Where, achieved. The ice fraction was calculated as ρ = density of ice slurry (kg/m3) 3 ratio of volume of water to the total volume of Vi = volume of ice (m ) 3 coffee press. Vw = volume of water (m ) 3 Thermo – physical properties of ice slurry Va = volume of additive (m ) 1. Density 2. Viscosity The ice slurry contains ice with a density In cleaning by ice pigging, the shear force on lower than the liquid phase, the difference the pipe wall is generally carried out through between densities gives a buoyancy force to the use of an effective viscosity. A number of ice particles. Due to this phenomenon, the experiments show that ice slurry behaves as a density cause stratification of the fluid in the Newtonian fluid at low ice fractions, and as a pipes and in storage tanks ducts. We need to non-Newtonian fluid at high ice fractions. agitate continuously for preventing the Many relationships between the ice fraction stratification more significant with ice slurry and effective viscosity have been developed14.

Thyarla et al Int. J. Pure App. Biosci. 5 (6): 1132-1138 (2017) ISSN: 2320 – 7051 Theoretically, this effective viscosity could be the solid pipe until the pipe appeared clean. used to predict the desired ice friction for Cleaning factor was defined as follow: fouling with a known adhesion to the pipe Cleaning factor = Time taken to clean with wall. 20˚C water/Time taken to clean with ice plug 2 µe = µ L (1+2.5 C + 10.005 C + 0.0027 x 1016.6 C) Table 1: Comparison of cleaning factors Where: S. Fouling Cleaning factor Cleaning factor No. materials for ice pigging for hot water µe = effective viscosity of ice slurry i.e. ice 1. Jam 10 3 water mix (Pa.s) 2. Salad cream 5 4 µ = viscosity of water (Pa.s) 3. Margarine 15 10 4. Toothpaste 15 - L = volume of water (fraction) The above table represents the result of the C = volume of ice (fraction) experiments with jam, salad cream, margarine 3. Thermal properties: low viscosity, and toothpaste smeared on the pipe walls. The high ability to transport energy by at least 20% higher the cleaning factor value, the better the of ice at -35˚C with a freezing point of -25˚C7. system is at cleaning the fouling material off 4. Chemical characteristics: pH 7 – 9.5 the walls. The ice pig or ice slurry is better at 5. Environmental impacts: non-toxic, cleaning soil of the tube wall than an non- polluting, without use of any chemical equivalent volume of hot water and much 6. Material compatibility: chemically better than cold water. stable, non-corrosive, compatible with iron, Ice pigging to plate heat heat excahngers in copper, aluminium, stainless steel and jam industry polymers. In an experiment12 the ice pig was pumped 7. Freezing point: -2˚C to -20˚C. through very complex geometries including a Cleaning efficiency plate heat exchanger, with an average gap The cleaning ability of the ice pig was width of 3 mm between the corrugated plates. measured on a straight 20 mm diameter length With smaller ice particles, beside a set of of glass pipe12. Different materials were plates, the other geometries included 90o bend, smeared on the inside wall of the pipe. The T-junction and orifice plate with area ratios of ambient water (20˚C) and then ice pig was 12:1 (contraction), 1:9 (expansion). circulated throughout the pipe at constant mass flow rates. The fluids were pumped through

Fig. 3: The ice pig successfully passed through PHE

Thyarla et al Int. J. Pure App. Biosci. 5 (6): 1132-1138 (2017) ISSN: 2320 – 7051 The ice pig was found successfully scouring 9. In expensive, “single use” and reduce man through these complex topologies and – time. appeared to do so as a plug. Even the most 10. It is environmental friendly as it reduces complex geometries appears to generate very the need of expensive and potentially little disruptions or mixing in the ice. hazardous cleaning chemicals. After the arranging of the plates in 11. Reduction in cleaning water and effluent plate heat exchanger, initially mains water at processing costs. 15˚C was circulated through the heat Benefits vs. other cleaning techniques: exchanger at 0.11m/sec velocity, it removes Ice pigging can be considered as an alternative small amount attached jam from plate to traditional flushing, uni – directional and surfaces. After the circulation of water, the ice CIP. Compared to these alternatives ice pig or ice slurry 20 – 30% volume to the total pigging provides the following benefits: circulated geometry volume, it removes the 1. More effective than flushing for removing majority of the reaming fouling of jam. This sediment and biofilms. circulation is continues for several times for 2. Ice pigging can easily and efficiently efficient cleaning, with the ice slurry contains remove „soft‟ fouling; using a volume of ice fraction ( is 50% by coffee press. i ice pig less than one tenth of the volume of The ice pig was cleaned to superior water6. level, when compared to water, with no 3. Can be used in locations where flushing is change in flow velocity or the volume of fluid not practical or possible. used. This is due to the effective viscosity of 4. Can navigate obstructions such as bends, the ice slurry increasing with ice fraction. The partially closed valves, butterfly valves, gap between the plates in plate heat and changes in pipe diameter. exchangers is 3 mm. it was found that best 5. No need of chemicals usage as in CIP. results were obtained when the ice particle sizes were optimized. Benefits of ice pigging: CONCLUSION Ice pigging can be considered as an alternative In some investigations ice pigging technology to traditional flushing. Ice pigging provides the has proved to be successful in food processing following benefits: operations. Based on their findings, food 1. Ice pigging is more suitable technology industry is also using ice pigging technology than other cleaning methods because it for CIP purposes. Looking to the similarity uses significantly less water during the with food processes, ice pigging has a great cleaning process5. potential in dairy processing also. This would 2. The waste can be easily collected and result in lower material cost, lower operational dispensed of eliminating contamination of cost but require other infrastructure for nearby steams or ponds. manufacture of ice pigs in dairy processing 3. It is more effective than flushing for plant itself. removing sediment and biofilm. 4. It is possible to add treatment materials REFERENCES (chemicals such as acids, alkali, anti- 1. Ahmad, T., Cleaning in Place. In. Dairy corrosion, and pacifier agents) as part of Plant Engineering and Management, Kitab the freezing point depressant. Mahal, Allahabad. 285-302 (2006), 5. Increase in product recovery within the 2. Ainslie, E.A., Quarini, G.L., Ash, D.G., processing lines. Deans, T.J., Herbert, M. and Rhys, T.D.L., 6. Reduction in down time required for Heat exchanger cleaning using ice cleaning. pigging. Proceedings of International 7. Use less water than flushing Conference on Heat Exchanger Fouling 8. Efficient removal of loose material at slow and Cleaning, Schladming, Austria. 433- speeds (high wall shear). 438 (2009). Copyright © Nov.-Dec., 2017; IJPAB 1137

Thyarla et al Int. J. Pure App. Biosci. 5 (6): 1132-1138 (2017) ISSN: 2320 – 7051 3. Anantakrishnan, C.P. and Simha. N.N., ice to estimate ice concentrations and Technology and Engineering of Dairy enthalpies of ice slurries, International Plant Operations, Laxmi Publications, Journal Refrigeration. 28: 13-19(2005). Delhi. 403-415 (1987). 10. Peter, W.E. and Michael, K., From 4. Evans, T.S., Quarini, G.L. and Shire, physical properties of ice slurries to G.S.F., Investigation into the industrial ice slurry applications. transportation and melting of thick ice International Journal of Refrigeration. 4- slurries in pipes. International Journal 12 (2005). Refrigeration. 145-151(2008). 11. Pronk, P., Hansen, T.M., Ferreira, C.A.I. 5. Friedman, M., Brian, L. and Randy, M., and Witkamp, G.J., Time dependent Best practices cleaning mains: clean, pig, behviour of different ice slurries during or dig. www.awwa .org/opflowgriffin storage, International Journal (2012). Refrigeration, 8: 27-36 (2008). 6. Griffen, J., Ice pigging new water, sewer 12. Quarini, J., Ice-pigging to reduce and pigging method offers unique benefits. remove fouling and to achieve clean-in- www.pgjonline.com (2013). place. Journal Applied Thermal 7. Hagg, C., Ice slurry as secondary fluid in Engineering. 747-753 (2002). refrigeration systems, M. Tech. Thesis. 13. Shires, G.S.F., Quarini, G.L. and Evans, School of Industrial Engineering and T.S., Pressure drop of flowing ice slurries Management, Stockholm (2005), in industrial heat exchangers, Journal of 8. Hansen, T.M., Radosevi, C.M. and Applied Thermal Engineering, 29: 1500- Kauffeled, M., Behavior of ice slurry in 1506 (2008). thermal storage systems, ASHARE 14. Thomas, D.G., Transport characteristics of Research Project RP1166, Danish suspension: VIII. A note on the viscosity Technological Institute (2002). of Newtonian suspensions of uniform 9. Melinder, A. and Granyard, E., Using spherical particles. Journal of Colloid property values of aqueous solutions and Science. 20: 267-277 (1965).