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Spouted Bed Reactors (SBRs) are currently receiving a lot of attention due to their properties: thanks to the enhanced mass and energy transfer rates and the unique configuration of these reactors, solid particles can be handled with very high efficiency, making them suitable for several applications, such as biomass gasification. Spouted Bed Reactors can also give positive responses to the problem of segregation, which strongly compromises the efficiency of processes involving the handling of heterogeneous mixtures. The aim of this work is to study the behaviour of a spouted bed facility, both experimentally and via simulations performed with the CFD program ANSYS FLUENT, in view of a possible employment of it to assess the scale up criteria or segregation phenomena in spouted beds. The solid phase is simulated enabling the DDPM-DEM model (Dense Discrete Phase Model - Discrete Element Method), commonly known as the Eulerian-Lagrangian approach. The influence of the following physical properties of the particles on the onset velocity was assessed: diameter, sphericity and density. The results of the simulations were compared with those obtained experimentally, for a single solid phase using three different types of inert material (glass, sand and PET) and also for a binary mixture. The model has been proved to be a useful tool to evaluate the performance and estimate the onset gas velocity of the spouted bed.

Cryosurgery is a rapidly developing discipline, alternative to conventional surgical techniques, used to destroy cancer cells by the action of low temperatures. Currently, the refrigeration is obtained via the adiabatic expansion of gases in probes used for surgeries, with the need of inherently dangerous pressurized vessels. The proposed innovative prototypal apparatus aims to reach the cryosurgical temperatures exploiting a closed-loop refrigeration system, avoiding the hazardous presence of pressurized vessels in the operating room. This study preliminarily examines the technical feasibility of the cryoablation with this machine focusing the attention on the cryoprobe design. Cryoprobe geometry and materials are assessed and the related heat transfer taking place during the cryoablation process is simulated with the aid of the computational fluid dynamics software ANSYS®Fluent. Parametric analyses are carried out varying the length of the collecting tubes and the inlet velocity of the cold carrier fluid in the cryoprobe. The values obtained for physical quantities such as the temperature reached in the treated tissue, the width of the obtained cold front, and the maximum pressure required for the cold carrier fluid are calculated and discussed in order to prove the effectiveness of the experimental apparatus and develop the machine further.

Agricultural activities produce an estimated amount of 32.7 MToe/year of residues in EU countries. They are mostly disposed in landfills, incinerated without any control, or abandoned in fields, causing severe impacts on human health and environment. Rice is one of the most consumed crops worldwide with an annual production of 782 million tons according to the Food and Agriculture Organization of the United Nations database. In this context, the EU-funded project LIFE LIBERNITRATE promotes the use of renewable residual sources (i.e., rice straw) to obtain new materials with an added value. The methodology is based on the incineration of rice straw in an own-designed and constructed valorization system. Rice straw/wood pellets are burned in optimized conditions to produce a maximized quantity of ashes with high silica content. These materials will be then used to treat water polluted with nitrates, representing an optimal example of circular economy strategy. In this work, the own-designed valorization unit is described, with special focus on its main constituting elements. The theoretical study of the co-incineration of rice straw and wood pellets identified the optimised combustion conditions. Experimental tests using the theoretical inputs confirmed the most adequate operational conditions (10 g rice straw pellets/min + 10 g wood pellets/min, 6–7 Nm3/h of air, T = 500 °C) and helped in the definition of improvements on the experimental plant.