A detailed CFD analysis of flow patterns and single-phase velocity variations in spiral jet mills affected by caking phenomena

8siIn this work we present a method to investigate the fluid-dynamics of a 3D, real-scale spiral jet mill when caking is occurring. CFD simulations are employed to deeply study the pressure and the velocity fields of the gas phase when the nozzles inlet pressure and the chamber diameter are varied to mimic the condition generated by the aggregates formation during the micronizaton process. The computational model is built replicating the experimental observation consisting in the fact that most of the crusts form on the outer wall of the chamber. Simulations underline that caking causes the deterioration of the classification capabilities of the system if the gas mass flow rate is kept constant at nozzles, allowing larger particles for escaping the system. It is shown that it is possible to mitigate this phenomenon by gradually reducing the gas mass-flow rate to keep constant the nozzles absolute pressure. This keeps unchanged the fluid spin ratio and the classification characteristics when caking is advancing.openopenSabia, Carmine; Frigerio, Giovanni; Casalini, Tommaso; Cornolti, Luca; Martinoli, Luca; Buffo, Antonio; Marchisio, Daniele L.; Barbato, Maurizio C.Sabia, Carmine; Frigerio, Giovanni; Casalini, Tommaso; Cornolti, Luca; Martinoli, Luca; Buffo, Antonio; Marchisio, Daniele L.; Barbato, Maurizio C

A novel uncoupled quasi-3D Euler-Euler model to study the spiral jet mill micronization of pharmaceutical substances at process scale: model development and validation

In this work we present a novel approach to model the micronization of pharmaceutical ingredients at process scales and times. 3D single-phase fluid-dynamics simulations are used to compute the gas velocity field within a spiral jet mill which are provided as input in a 1D compartmentalized model to calculate solid velocities along the radial direction. The particles size reduction is taken into account through a breakage kernel that is function of gas energy and local solid holdup. Simulation results are validated against micronization experiments for lactose and paracetamol, comparing the model predictions with D10, D50 and D90 diameters values coming from Design of Experiments isosurfaces. The developed model allows for a fair estimation of the outlet particle size distribution in a short computational time, with very good predictions especially for D90 values

Contactless measurement of PET bottles' thickness

The tuning of Injection Stretch Blow Molding (ISBM) process for PET bottles is crucial to lower the production costs, reduce the environmental impact and assure a sufficient quality of the final product. Among the parameters defining PET bottles quality, the thickness is of primary importance for the appearance and mechanical resistance of the final product. Up to date, tuning of the process is demanded to the operator skills through a trial and error process, iterated until the wanted configuration is achieved. Moreover, the process is not controllable because the PET bottles characteristics are not currently measured. This work describes a method for PET bottles thickness measurement; the method could be implemented as part of an active control of the ISBM process. A noncontact method based on infrared transmittance measurement has been developed to evaluate the wall thickness of PET bottles. The method uncertainty is 6% when the nominal thickness ranges between 0.2 and 0.5 mm. A prototype of the measurement system has been developed and validated testing PET specimens with different geometry, pigmentation and composition

Non-contact techniques for the quality analysis of PET bottles

This work was motivated from finding a complementary way of tuning and controlling the machine parameters of Injection Stretch Blow Molding process. In the current approach, a specialized technician detects the bottle defects by visual inspection and corrects the machine parameters using its own experience or indications obtained by previous statistical analyses. As all human based operations, inherent limitations are that the results are influenced by the operator skills; in addition, the experience can be hardly converted into a database, which could be used for the process optimization. The solution investigated in this work is to replace visual inspection with an image processing system. A prototype for offline analyses of PET bottles was designed in order to have a resolution allowing to identify the most common bottle defects. The acquired images were analyzed with algorithms implemented in LabVIEW. Results showed that this system can off-center gate, haze and pearlescence with a repeatability and reproducibility sufficient for the identification of bottles with manufacturing defects

Non-contact measurement of the temperature profile of PET preforms

This paper describes a method for the measurement of the internal and external temperature profiles of PET preforms used in the Injection Stretch Blow Moulding (ISBM) process. Temperature is the most critical parameter for the process quality, but no online measuring system has yet been implemented. The proposed system is based on two thermopiles for the identification of the internal temperature profile and a thermal camera for the measurement of the external temperature profile. The adopted sensors have been individually calibrated and the measurement uncertainty budget proved that the sensor's instrumental uncertainty is not the actual limiting factor for the system accuracy. The main accuracy limitations derive from the emissivity of the materials of PET preforms. The use of average emissivity values increases the measurement uncertainty to 1.4°C, a value that is judged acceptable in this specific application

Non-contact measurement of the temperature profile of PET preforms

This paper describes a system for the measurement of the internal and external temperature profiles of PET preforms used in the Injection Stretch Blow Moulding (ISBM) process. Many works in literature highlighted the importance of these quantities to improve the production quality of PET bottles, but none addressed the development of a measuring system suitable for this scope. A measuring system based on two thermopiles for the identification of the internal temperature profile and a thermal camera for the measurement of the external one has been designed. The adopted sensors were individually calibrated and the uncertainty budget, accounting for both instrumental uncertainties and the effect of multiple reflections, was derived. A prototype of the measuring system was tested on an industrial ISBM machine. The dependence of the preforms temperature profile on the settings of the ISBM machine was investigated. Results evidenced that the minimum variations of the machine settings induced temperature differences significantly larger than the measurement uncertainty, thus proving the effectiveness of the proposed system