8 AM003 Conceptual Design and Preliminary Testing of a Superheated Steam Spray Dryer Prototype Maelada Fuengfoo 1 *, Chalida Niumnuy 2 , Sakamon Devahastin 1 , Somchart Soponronnarit 3 1 Advanced Food Processing Research Laboratory, Department of Food Engineering, Faculty of Engineering, King Mongkut’s University of Technology Thonburi, 126 Pracha u-tid Road, Tungkru, Bangkok 10140, Thailand. 2 Center of Advanced Studies in Industrial Technology, Department of Chemical Engineering, Faculty of Engineering, Kasetsart University, 50 Ngam Wong Wan Road, Chatuchak, Bangkok 10900, Thailand. 3 Division of Energy Technology, School of Energy, Environment and Materials, King Mongkut’s University of Technology Thonburi, 126 Pracha u-tid Road, Tungkru, Bangkok 10140, Thailand. Corresponding author: Maelada Fuengfoo. E-mail: fengmdf@ku.ac.th Abstract It is well recognized that using hot air as the drying medium leads to many adverse changes in terms of the dried product quality, including discoloration, losses of nutrients and other negative changes due to the oxidation reactions. To alleviate some of the above-mentioned limitations, superheated steam has been proposed and tested in this work as an alternative medium for spray drying. A superheated steam spray dryer prototype was designed and fabricated. The prototype, compared with a traditional hot air spray dryer, consists of an extra superheated steam generation unit and a powder separation unit, which was specially designed to avoid condensation of exhaust steam in the powder collector. This dryer prototype was then tested for its performance in terms of the percent powdery product recovery. The dryer was operated at the superheated steam pressure of 20 kPa (gage), inlet steam velocity of 15 m/s and temperatures of 150 and 170  C. An aqueous solution of NaCl (20% w/v) was used as the test liquid feed at a flow rate of 3 mL/min. The percent powdery product recovery was noted to be in the range of 30.5 to 46.7%, which was still lower than that obtained in the case of hot air spray drying conducted in the same set-up. Keywords: Powder collection; Product recovery; Steam condensation; Superheated steam drying. 1 Introduction Although hot air is typically used as the drying medium in most spray dryers, it is well recognized that hot air drying leads to many adverse changes in terms of the dried product quality, including discoloration, losses of nutrients and other negative changes due to the oxidation reactions, among others (Devahastin and Mujumdar, 2014). To alleviate the above-mentioned problems, superheated steam has been proposed and tested as an alternative medium for spray drying since superheated steam drying results in negligible oxidation reactions which, in most cases, are undesirable. Besides, superheated steam exhibits superior thermal properties to hot air in both constant and falling rate periods under certain conditions and hence an improved thermal efficiency of the spray drying process (Ducept et al., 2002). So far, the idea of superheated steam spray drying has been verified mainly only via theoretical analysis or numerical modeling. Crowe et al. (1985) numerically assessed the performance of a superheated steam spray dryer using a model for gas-particle flows in a conical cylindrical, concurrent spray chamber. The numerical predictions suggested that steam is a more effective drying medium because of its higher heat transfer coefficient and specific heat. Frydman et al. (1998) later employed commercial software to simulate the most important features of both superheated steam and hot air spray dryers, including fields of gas temperature and velocity. The simulations were validated by comparing the experimental and numerical values of temperature inside the chamber in the case of water drying (Frydman et al., 1999) and later in the case of a real product (Ducept et al., 2002). The most recent study on superheated steam spray drying was that of Islam et al. (2016) who proposed the use of vacuum superheated steam spray drying to dry orange juice. Physicochemical properties of orange juice powder with different combinations of juice solids: