Ice Pigging: Economical and Novel Method for Cleaning-In-Place of Food and Dairy Processing Equipment: a Review
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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 Copyright © Nov.-Dec., 2017; IJPAB 1132 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.