Superheated steam drying: Design aspects, energetic performances, and mathematical modeling

Abstract

This paper presents a comprehensive overview of state-of-the-art of design aspects, energetic performances, and mathematical modeling on superheated steam drying (SSD). In fact, SSD is presented as an efficient drying method because of its high energy efficiency, safety, high drying rate, and high quality of final product. In this study, different SSD systems are classified into two classes: fundamental and basic research and applied research. Three main laboratory scale dryers are used in fundamental and basic research: oven dryer, tunnel dryer, and fixed bed dryer. However, five main types of dryers: kiln dryer, rotary drum dryer, fluidized bed dryer, flash dryer, and impingement dryer that find application in industry, are used in applied research. The general design of superheated steam dryers is constituted of: steam generator, fan, heater, drying chamber, and heat exchanger. The study shows that depending of the characteristics of the tested materials and the different purposes of the research, a proper design of the drying chamber is crucial as it is directly linked to the efficiency of the SSD system. The observation of the drying kinetics has shown that mainly the tested material passed through three clear phases: initial condensation–evaporation phase, constant drying rate phase, and falling drying rate phase. Based on these three phases, mathematical modeling is performed in order to predict the behavior of studied material and the efficiency of drying systems. The inversion temperature is one of the main fundamental parameters that should be studied. Over this temperature the performance of SSD is better than that of hot air drying. The research results show that the energy consumption in SSD is lower comparing with hot air drying method. Furthermore, the quality of final products dried using SSD is good with a uniform shrinkage and good rehydration capability.