Abstract
In this paper, an innovative fluidized bed dryer with inert particles is presented. The system can be used for drying of solutions, suspensions and pastes in order to obtain a powdered product. The experiments were performed in a pilot-scale dryer with a cylindrical column 0.215 m in diameter and 1.2 mm height, with glass spheres as inert particles. The material used for drying was CuSO4 solution. The effects of operating conditions on the dryer throughput and product quality were investigated. Main performance criteria, i.e. specific water evaporation rate, specific heat consumption and specific air consumption, were quantified. Nearly isothermal conditions were found due to thorough mixing of the particles. The energy efficiency of the dryer was also assessed. Simple heat and mass balances predicted the dryer performance quite well.
Highlights
Many processes in chemical, pharmaceutical and food processing industries involve drying of solutions, suspensions and pastes in order to obtain the final product in the form of powder
A relative comparison of sizes of different dryers with the fluidized bed dryer is illustrated in Figure 10, i.e. for suspension with 65 % water content and for capacity of 8 t of dry powdered product per day, it is required: the tunnel dryer with 240 trays 2x1 m in size, spray dryer of 7 m in diameter and fluidized bed dryer of 0.8 m in diameter
Suspensions and pastes in a fluidized bed of inert particles is a simple and very effective technique for all materials that do not adhere to the inert particles
Summary
Pharmaceutical and food processing industries involve drying of solutions, suspensions and pastes in order to obtain the final product in the form of powder. Drying of slurries on inert particles is a relatively novel technology to produce powdery materials It was originally developed for drying of pigments, chemicals and some biomaterials to eliminate constrains of spray, drum and paddle dryers. With respect to the main efficiency criteria, i.e. specific water evaporation rate, specific heat consumption and specific air consumption, a fluidized bed dryer with inert particles represents a very attractive alternative to other drying technologies. During the drying process the size of aggregates decreases due to elutriation of dried particles from the bed surface (Fig. 2b). In this case, a more homogenous and stable bed can be obtained by incorporation of a low-speed mechanical mixer. Due to the intensive mixing of inert particles during fluidization the bed temperature is approximately uniform
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