Wall deposition occurs in spray dryers when dried or partially dried particles contact and adhere to the walls during operation, thus reducing the yield of product collected. Wall deposits also present a product conta...Wall deposition occurs in spray dryers when dried or partially dried particles contact and adhere to the walls during operation, thus reducing the yield of product collected. Wall deposits also present a product contamination risk and a fire or explosion risk when spray drying products that oxidize exothermically, such as milk powder. Re-entrainment is the resuspension of spray dryer wall deposits into the main gas stream for collection as product. Literature suggests that the process for re-entrainment of particles from spray dryer wall deposits is strongly dependent on particle size and gas velocity.展开更多
Particle interactions play a significant role in controlling the performance of dry powder inhalers （DPIs）, which mainly arise through van der Waals potentials, electrostatic interactions, and capillary forces. Our ...Particle interactions play a significant role in controlling the performance of dry powder inhalers （DPIs）, which mainly arise through van der Waals potentials, electrostatic interactions, and capillary forces. Our aim is to investigate the influence of electrostatic charge on the performance of DPIs as a basis for improv- ing the formulation of the particle ingredients. The mixing process of carrier and active pharmaceutical ingredient （API） particles in a vibrating container is investigated using a discrete element method （DEM）. The number of APl particles attaching to the carrier particle （i.e., contact number） increases with increas- ing charge and decreases with increasing container size. The contact number decreases with increasing vibrational velocity amplitude and frequency. Moreover, a mechanism governed by the electrostatic force is proposed for the mixing process. This mechanism is different from that previously proposed for the mixing process governed by van der Waals forces, indicating that long-range and short-range adhesive forces can result in different mixing behaviours.展开更多
Residence time distributions （RTDs） in horizontal fluidised beds have a huge effect on solid product properties and are infuenced by the internal design of the apparatus, e.g. the separation into different compartme...Residence time distributions （RTDs） in horizontal fluidised beds have a huge effect on solid product properties and are infuenced by the internal design of the apparatus, e.g. the separation into different compartments by weirs. Weirs can be passed in or against the overall solid transport direction, with the back-flow resulting in axial dispersion, which is a measure of the spread of the RTD. Therefore, the ratio of exchange rates at weirs under different fluidisation conditions provides information on axial dispersion. In this work, a methodology based on particle tracking velocimetry is presented to obtain information on the exchange rates of particles at weirs in horizontal fluidised beds. The internal recirculation is studied for over-flow weirs with respect to different fluidisation conditions, providing a first step towards determining the effects of weirs and fluidisation conditions on axial dispersion and RTDs in horizontal fluidised beds.展开更多
Dry deposited particles, larger than 1.3 μm, were collected under clear, cloudy, and foggy conditions during a cruise, traversing the Yellow Sea and the East China Sea from 23 March to 8 April 2011. In these areas, a...Dry deposited particles, larger than 1.3 μm, were collected under clear, cloudy, and foggy conditions during a cruise, traversing the Yellow Sea and the East China Sea from 23 March to 8 April 2011. In these areas, air masses are influenced by pollution outflows from the Asian continent. The size and elemental composition of dry deposited particles were investigated using a scanning electron microscope. Number-size distributions of these particles were approximately lognormal. Under clear conditions, the mode size was about 5.0 μm, with a mean diameter of 6.9 μm. Under cloudy and foggy conditions, the mean diameters were 5.7 and 6.0 μm, respectively, but the mode sizes were vague. Non-mixed mineral particles, sea salt, and mixed mineral-sea salt particles were the major particle types. Correspondingly, Al and Si were the most frequently detected elements. Frequencies of K-, Ca-, and S-containing particles were highest under foggy conditions, while the frequency of Na-containing particles was lowest. These results indicate that fog favored sulfate production on the particles and led to the deposited mineral particles more abundant in secondary salt, suggesting the importance to consider the dependence of the comoosition of deoosited mineral narticles on weather as well as narticle size.展开更多
文摘Wall deposition occurs in spray dryers when dried or partially dried particles contact and adhere to the walls during operation, thus reducing the yield of product collected. Wall deposits also present a product contamination risk and a fire or explosion risk when spray drying products that oxidize exothermically, such as milk powder. Re-entrainment is the resuspension of spray dryer wall deposits into the main gas stream for collection as product. Literature suggests that the process for re-entrainment of particles from spray dryer wall deposits is strongly dependent on particle size and gas velocity.
文摘Particle interactions play a significant role in controlling the performance of dry powder inhalers （DPIs）, which mainly arise through van der Waals potentials, electrostatic interactions, and capillary forces. Our aim is to investigate the influence of electrostatic charge on the performance of DPIs as a basis for improv- ing the formulation of the particle ingredients. The mixing process of carrier and active pharmaceutical ingredient （API） particles in a vibrating container is investigated using a discrete element method （DEM）. The number of APl particles attaching to the carrier particle （i.e., contact number） increases with increas- ing charge and decreases with increasing container size. The contact number decreases with increasing vibrational velocity amplitude and frequency. Moreover, a mechanism governed by the electrostatic force is proposed for the mixing process. This mechanism is different from that previously proposed for the mixing process governed by van der Waals forces, indicating that long-range and short-range adhesive forces can result in different mixing behaviours.
文摘Residence time distributions （RTDs） in horizontal fluidised beds have a huge effect on solid product properties and are infuenced by the internal design of the apparatus, e.g. the separation into different compartments by weirs. Weirs can be passed in or against the overall solid transport direction, with the back-flow resulting in axial dispersion, which is a measure of the spread of the RTD. Therefore, the ratio of exchange rates at weirs under different fluidisation conditions provides information on axial dispersion. In this work, a methodology based on particle tracking velocimetry is presented to obtain information on the exchange rates of particles at weirs in horizontal fluidised beds. The internal recirculation is studied for over-flow weirs with respect to different fluidisation conditions, providing a first step towards determining the effects of weirs and fluidisation conditions on axial dispersion and RTDs in horizontal fluidised beds.
基金This study was supported by the Education Bureau of Hebei Province for Excellent Young Scholars （YQ2014020）, the Natu- ral Science Foundation of Hebei Province （D2016402120） and the National Natural Science Foundation of China （41541038）. The Chinese Scholarship Council （CSC） supported Wei Hu＇s research at the Prefectural University of Kumamoto, Japan. We thank Ms. Jin-hui Shi and Ms. Cheng-cheng Chen for their assistance with particle collection, and Nicholas James O＇Connor for his assistance with editing.
文摘Dry deposited particles, larger than 1.3 μm, were collected under clear, cloudy, and foggy conditions during a cruise, traversing the Yellow Sea and the East China Sea from 23 March to 8 April 2011. In these areas, air masses are influenced by pollution outflows from the Asian continent. The size and elemental composition of dry deposited particles were investigated using a scanning electron microscope. Number-size distributions of these particles were approximately lognormal. Under clear conditions, the mode size was about 5.0 μm, with a mean diameter of 6.9 μm. Under cloudy and foggy conditions, the mean diameters were 5.7 and 6.0 μm, respectively, but the mode sizes were vague. Non-mixed mineral particles, sea salt, and mixed mineral-sea salt particles were the major particle types. Correspondingly, Al and Si were the most frequently detected elements. Frequencies of K-, Ca-, and S-containing particles were highest under foggy conditions, while the frequency of Na-containing particles was lowest. These results indicate that fog favored sulfate production on the particles and led to the deposited mineral particles more abundant in secondary salt, suggesting the importance to consider the dependence of the comoosition of deoosited mineral narticles on weather as well as narticle size.
