CFD approach for the moisture prediction in spray chamber for drying of salt solution A. Salem *, M. Ahmadlouiedarab, K. Ghasemzadeh Mineral Processing Technology Research Center, Chemical Engineering Department, Sahand University of Technology, 53317-1111 Tabriz, Iran 1. Introduction The basic principle of spray drying process was proposed at the end of 19 century [1]. Nowadays, there is a great demand for using this drying method in ceramic, food, pharmaceutical and chemical industries because important designs were carried out to improve the quality and quantity of products [2]. It is foreseen that this demand will considerably increase in other industrial areas. One of the spray drying applications is production of salt from solutions. The development of manufacturing technology in the salt industry is aimed to find more efficient and cost effective ways to produce high quality products from salt solutions. An assessment about the role of different processing steps has shown that evaporation and crystallization processes comprise a great part of energy cost. However, an additional cost of energy can be attributed to the crashing, powder preparation and dissolving of salt in water. The first cost can be significantly reduced through the use of spray drying technology which produces acceptable quality and quantity of final product using a minimum number of steps. In the design of spray chamber the estimation of moisture and temperature patterns become more desirable to improve the production capacity [3]. There is a clear requirement for a robust economical procedure and the accurate moisture prediction in spray dryers. Such a procedure can be useful in estimating dimensions and performance of drying system. Also it may be used to examine various process parameters that are difficult, if not impossible, to examine experimentally. Since the moisture and temperature profiles have not already been predicted with sufficient accuracy, suitable fundamentals for estimating the moisture and temperature patterns during spray drying of salt solution have been lacking up to now. In the spray drying process a hot core in the center of chamber was observed. This circumstance is due to a lack of knowledge about the temperature and moisture profiles. Notably, Bimbenet et al. studied heat balance of a multistage spray dryer and experimentally tested various operating condition on drying on skim milk. They showed that the enthalpy diagram of air proves the fast estimations necessary for heat, mass balances and energy consumption [4]. Huang et al. used CFD method to investigate air flow pattern, temperature and humidity profiles at different positions in the spray drying chamber. The experimental data and calculated values were compared in this research and good agreement was found between experimental data and computational values [5]. The model of agglomeration during spray drying process was presented by Verschueren et al. [6]. The obtained results by authors showed that the use of some known relation and several developed approaches predict the post collision properties of different colliding particles and droplets. Kieviet et al. proposed the air flow pattern in a co-current spray dryer and compared the calculated data with experimental results. This profile was obtained by CFD method. They concluded that CFD Journal of Industrial and Engineering Chemistry 17 (2011) 527–532 ARTICLE INFO Article history: Received 30 June 2010 Accepted 3 October 2010 Available online 7 May 2011 Keywords: Spray drying Moisture CFD Salt solution ABSTRACT This investigation describes and demonstrates the effectiveness of computational fluid dynamics, CFD, method to predict the moisture changes during drying process of salt solution in co-current spray dryer. In order to prove the validity of predicted profiles, the obtained results were compared by reported experimental data. The moisture profile calculated by two dimensions model confirmed the sharp change in moisture pattern close to the center of drying chamber. It is proven that the moisture reaches to constant value as radial distance increases up to 20%. The model was also employed to investigate the influence of operating parameters such as, salt concentration, feed rate, hot air flow rate and temperature, inlet air moisture, and outlet suction pressure on moisture distribution. It was found that the feed rate and suction pressure significantly affect the moisture profile in radial and axial directions. The obtain results can be used in industrial practice. ß 2011 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry. * Corresponding author. Tel.: +98 4123459159; fax: +98 4123444355. E-mail address: salem@sut.ac.ir (A. Salem). Contents lists available at ScienceDirect Journal of Industrial and Engineering Chemistry journal homepage: www.elsevier.com/locate/jiec 1226-086X/$ – see front matter ß 2011 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry. doi:10.1016/j.jiec.2010.10.023