Modelling of Milk Emulsion Drying in Spray Dryers

Question: What is the Modelling of Milk Emulsion Drying in Spray Dryers? Answer: Introduction In this report we will discuss about the concept of modeling of milk emulsion drying in spray dryers. The milk emulsion drying is an industrial process which is used for producing powdered milk. This process is performed with the help of spray dryers. The spray drying process is a method to produce a dry powder from a liquid or slurry by using a hot gas. It is most preferred method of drying. Therefore, in case of milk emulsion drying process to produce milk powder spray drying process is implemented in steps with the help of spray dryers. The purpose of making this report is to discuss background, aims, objectives, literature review and methodologies of modeling of milk emulsion drying in spray dryers. Following is the figure of powdered milk production (Threlfall-Holmes, 2009). Figure: Flow Chart of Powered Milk Production As in above figure we can see use of spray dryers in production of milk powered and it is a complete flow chart of milk emulsion drying in spray dryers. Discussion The delivery of raw milk from farms consists of its inspection and the base of this inspection is legal regulation of chemical, bacteriological composition and sensorial. Once approval is got from this first step then clarification of milk emulsion is done through separators, heat exchangers are used for heat purpose and then storage is done in tanks at 4C. In last step, the ratio of milk fat is adjusted to total solids and final product is developed as per requirements. Now, in next segments of report we will emphasize on above mentioned concepts in detail such as background, aims, literature review etc. It is necessary to thoroughly understand overall process of milk emulsion drying. Background The spray drying equipment and techniques were developed over a period of several decades from 1870s. The technique of spray drying for modeling milk emulsion for drying was come during World War II. The reason for using this technique was sudden need to reduce the weight of transport of food and other materials. While analyzing about milk emulsion for drying in spray dryers, we got to know about some initial assumptions regarding this process and these assumptions have been following for long time (Birchal, Passos, 2005). Those assumptions are listed as below: According to first assumption of milk emulsion drying in spray dryers is that top of the dryer chamber are used to inject hot gas and milk suspension in it at constant rate. Another assumption about process of milk emulsion is that the gas phase that is formed of air and vapor behaves as a perfect mixture and also flows inside the dryers. The suspension under this process of milk emulsion for drying is homogeneous, uniform drops and atomized forming spherical and inside the chamber these are well mixed without interacting with one another. Next assumption regarding milk emulsion is that the flow of heat is from hot air to drops or particles. The gradients of temperature inside the particles are insignificant. The drying rate at individual basis is described by water evaporation and transfer from a single particle to the gas phase (Focus on Powder Coatings, 2003). These above discussed assumptions are considered important to successfully handle this process of milk emulsion for drying in spray dryers. These assumptions are not new for industries those deal in milk emulsion for drying. Before start discussion about aims of milk emulsion drying, we would like to discuss about spray drying process that is used for milk emulsion. Therefore, in next segment we will emphasize on this essential concept. Spray Drying Process for Milk Emulsion There are five major steps of spray drying that are required to follow for milk emulsion and those steps are listed as below: Concentration Atomization Droplet-Air Contact Droplet Drying Separation Concentration: Under this step, prior to introduction feedstock is highly concentrated into spray dryer. Atomization: This is another essential step of spray drying process and at this stage of atomization the optimum condition for evaporation to a dried product that have desired characteristics, is created. (Birchal, Huang, Mujumdar, Passos, 2006). Droplet-Air Contact: Under this step, atomized liquid is brought into contact of hot gas and it results in the evaporation more than 95% of water that is contained in the droplets. Droplet Drying: Under this step, moisture evaporation is done in two stages. During first stage, a sufficient amount of moisture is found in drop to replace the liquid evaporated at the surface and evaporation occurs at constant rate. When there is no longer moisture to maintain saturated conditions at surface of droplet then second stage starts. Lack of moisture causes a dried shell to form at the surface. In this case, evaporation depends on the dissemination of moisture through the shell and it is increasing in thickness. Separation: For final separation stage, cyclones, bag filters and electrostatic precipitators are used. For purification and to cool the air wet scrubbers are used (Nath, Satpathy, 1998). Therefore, by implementing above discussed step, spray drying process is implemented successfully for milk emulsion (Bandhari, 1994). Aims or objectives The process of milk emulsion for drying is not an easy process to perform and the aim of this process is to provide an ideal product with better quality standards such as size of particle, distribution, bulk density, remaining moisture content and morphology. The powdered milk has various application areas where it is used for making food and other confectionary products. To achieve this aim, spray dryers provide appropriate help (Marinos-Kouris, Maroulis, Kiranoudis, 1998). Literature Review As we have discussed above basic information about modelling of milk emulsion drying and from this we got to know that how basic steps are implemented in this process to produce powdered milk. There are various research studies available on this topic that provide lots of essential information about milk emulsion. In literature review, major discussion topics are related to milk emulsion includes spray drying technology, its characterization, modeling and simulation etc. The discussion about these topics will help to understand process of milk emulsion and uses of spray dryers. It is an important segment of this report (Martins, Siqueira, Freitas, 2012). The most important point that is discussed in most of literature review is model development that is used in process of milk emulsion drying for spray dryers. The main things that are involved in development of this model are a set of constitutive algebraic equations and these equations describe mass and transfer of heat between gas and a single particle, drying kinetics of a single particle that is surrounded by gas and the function of particle residence time distribution insider the chamber (Danviriyakul, McClements, Decker, Nawar, Chinachoti, 2002). Besides model development, the literatures also have reviews for spray drying technology. According to Gharsallaoui, Spray drying process have some advantages that it can be designed according to any capacity required. The operation of spray drying technology is continuous and can adapt full automatic control (Gharsallaoui, Roudaut, Chambin, Voilley, Saurel, 2007). Both heat-resistant and heat-sensitive products can be used for spray drying technology. There are also some limitations that are found by researchers in case of spray drying technology. According to Katta Gauvin, the concerned limitations are limited flexibility in producing structures with complex morphologies and quick drug release rates that exhibit a burst effect. While researching about spray drying technology for milk emulsion, we have found critical parameters of spray drying. In this report, it is essential to discuss about those critical parameters that makes spray drying process important (Gauvin, Katta, 1976 ). Inlet Temperature of Air This critical parameter of spray drying technology, researcher Michael defines that as much as higher the temperature of inlet air, the moisture evaporation will be faster. But in this case, powder is exposed to higher temperature and this will alter the both chemical and physical properties of products that are heat sensitive (Michael, 1993). Outlet Temperature of Air About this critical parameter, Maury defines that sizing of powder recovery equipments are governed by outlet temperature of air. As much as temperature of outlet will higher, larger the size of powder recovery equipment. The final moisture content of powder is controlled by outlet air (Maury, Murphy, Kumar, Shi, Lee, 2005). Viscosity The high viscosity delays correct drop formation. As much as velocity will lower, lesser the energy. Also, pressure is required to form a pattern for spray. Solid Content According to this critical factor of spray drying, care is required in this process with high solid loadings and it is necessary to maintain proper atomization that can ensure correct droplet formation. Surface Tension The addition of a small amount of surfactant has potential to lower the surface tension. This provide result in a wide spray pattern, higher drop velocity and smaller droplet size. Like above discussed elements, Feed Temperature, Volatility of Solvent and Nozzle Material are also considered as critical element of spray drying process. In this way, by using these critical elements spray drying process performs milk emulsion drying. The process of milk emulsion has now improved. Various new technologies and techniques have introduced to enhance process of milk emulsion drying in spray drying and these innovative techniques include spray drying for stable injectable liquid formation, encapsulation, granulation, bioavailability and inhalation and controlling of release products. Methodologies In previous sections of this report, we have discussed various essential concepts regarding milk emulsion drying in spray dryer such as its background, development model, aims and literature reviews. From this information we got to know that how spray drying technique is used for milk emulsion and how and when it was started. Now in this segment of report, we are going to discuss about methodologies that are used for milk emulsion. It is an essential topic that is required to discuss in this report. According to analysis, we got to know that numerical methods are highly preferred for solving model equations that are used in model development for implementing milk emulsion process (Klinkesorn, Sophanodora, Chinachoti, Decker, McClements, 2006). Numerical methods are highly preferred due to complexity of the differential-algebraic equation system i.e. DAE. According to authors, serious convergence problems were found while simulating the beginning of drying process. On the behalf of t hese arguments it was sufficient to support the proposal of a new method that can solve problem of DAE system directly. In this new method DASSL code is applied. By using the backward differential method, it was possible for DASSL code to transform DAE system into set of algebraic equations and solution for these algebraic equations is obtained by Newton methods. The code was developed in FORTRAN language that was integrated into FORTRAN program and it contains initial conditions. In this way, by using numerical methods, the computation for implementing spray drying for milk emulsion was done. This computation is cumbersome and required appropriate use of numerical methods (Birchal, Huang, Mujumdar, Passos, 2006). Conclusion In this report, we have done detailed study of milk emulsion drying in spray dryers and on the behalf of above study we obtain some results. On the behalf of above study we can say that the development model satisfactorily describes the response variables and this is done under continuous operations. Besides this appropriate use of numerical methodologies will help to perform numerical tasks in spray drying process and better outcomes can get. This study provides insight about characteristics of spray drying and how by using its critical factors, this technique is implementing milk emulsion. Beside these current impact of spray drying process, its future impacts will also be better, because in future multistage processes, temperature-gradient systems and new spray techniques will be used. The designs of traditional equipments will become more and more advanced. In future, the versatility, output capacity, continuous operations and controllability all desire features will be availabl e in spray drying and due to this it will become easier to modeling milk emulsion drying. Presently this technique is most exciting technology in case of pharmaceutical industry and other industries. The reason for this is its quality standards for complying end product (Schuck, Mjean, Dolivet, Jeantet, 2005). References Threlfall-Holmes, P. (2009). Spray Dryer Modelling (1st ed.). Heriot-Watt University. Birchal, V., Passos, M. (2005). Modeling and simulation of milk emulsion drying in spray dryers. 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European Journal Of Pharmaceutics And Biopharmaceutics, 59(3), 565-573. https://dx.doi.org/10.1016/j.ejpb.2004.10.002 Martins, R., Siqueira, S., Freitas, L. (2012). Spray Congealing of Pharmaceuticals: Study on Production of Solid Dispersions Using Box-Behnken Design. Drying Technology, 30(9), 935-945. https://dx.doi.org/10.1080/07373937.2011.633251 Michael, JK (1993). Spray drying and spray congealing of pharmaceuticals. In: Encyclopedia of pharmaceutical technology. Marcel Dekker INC, NY,14, 207-221. Klinkesorn, U., Sophanodora, P., Chinachoti, P., Decker, E., McClements, D. (2006). Characterization of spray-dried tuna oil emulsified in two-layered interfacial membranes prepared using electrostatic layer-by-layer deposition. Food Research International, 39(4), 449-457. https://dx.doi.org/10.1016/j.foodres.2005.09.008 Danviriyakul, S., McClements, D., Decker, E., Nawar, W., Chinachoti, P. (2002). 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