Intermittent Drying of Nopal (Opuntia Ficus Indica) in a Fluidized Bed Pilot Dryer Adapted with Revolving Chambers

Intermittent drying is a novel method for improving the food drying kinetics, enhancing product quality and reducing energy consumption per unit of moisture removed at the lab scale. However, the drying protocol itself makes it difficult to implement it at the pilot plant scale without important energy loses. Taking this into account, an accessory for a fluidized bed pilot dryer was developed using an arrangement of revolving chambers that could increase the efficiency of the drying process; nopal (Opuntia ficus indica) was employed as a food material. Several drying experiments were conducted at the laboratory scale in order to establish the most appropriate drying condition to be further tested at the pilot plant scale. No statistical difference was observed between the drying curves obtained in the laboratory and pilot plant dryers under conventional and intermittent drying conditions, which means that the arrangement of chambers guarantees equal and consistent treatment of the solid. Interestingly, the results indicate that a drying protocol of nopal size “E” using the adapted fluidized bed dryer with tempering cycles at pilot plant scale can be regarded as an excellent and cost-effective methodology for processing vegetables without chemical quality losses. Practical Applications In this work, the performance of a novel fluidized bed dryer, adapted with an arrangement of revolving chambers specially designed to increase the efficiency of intermittent drying at the pilot plant scale, was evaluated. Cubes of nopal (Opuntia ficus indica) was chosen to take advantage of a biomaterial with high nutrimental characteristics. It was concluded that the arrangement of the equipment was able to maintain an equal and consistent treatment of the solid that in consequence, lead to a high chemical quality of the final dried product, comparable to that obtained at the laboratory scale. Additionally, the results indicate that the scaling of the process in the dryer prototype was highly efficient as it allowed to increase 300% the amount of biomaterial to be processed in one single drying operation. It was proposed that the use of the dryer adaptor has a great potential to increase the efficiency of drying processes of other biomaterials.