Cohesive powders are troublesome in terms of flow reliability, consistency and accuracy, posing great challenges in manufacturing. In this article the current understanding of rheological behaviour of powders, considering bulk friction and apparent shear viscosity, is reviewed. Flow rules accounting for particle properties, process dynamics, and their interactions have been proposed in literature, but require rigorous experimental validation. The suitability of state-of-the-art instruments for this purpose is critically reviewed. The current understanding of the influence of particle properties, fluid drag and shear strain rate on the dynamics of powder flow is summarised, including the topical subject of powder spreadability for additive manufacturing.
The recent pandemic of COVID-19 brings the topic of vaccines and the urgency with which they are required into the popular literature. This article focuses on the merits of using nanovaccines to establish mucosal immunity in the respiratory tract the primary site of infection and transmission for a variety of infectious diseases. Targeting the innate immune response which is mediated by airway macrophages, the host cell for some pathogens, can be achieved with a variety of nanoparticle technologies conferring protection from the disease.
The article reviewed the solid collection performance and scale-up methodology of gas-solid cyclones at high solid density conditions based on experimental and numerical studies mainly published after 2007. The models to predict pressure drop of cyclone, the non-uniform distribution of gas-solids flow, and scale-up methodology, the phase graph of the stability of uniform distribution/maldistribution of solids in parallel cyclones, and recent progress in high-solid loading cyclones are summarized.
With increasing quantity of waste generated and fast growing concerns about climate change, there has been renewed impetus recently to develop advanced thermochemical processes using waste biomass as a feedstock. This is because these processes have the potential to add value to cheap and abundant materials by converting them into advanced biofuels and chemicals. This reviews paper is concerned principally with newest applications of fluidised bed reactors for waste treatment, with particular attention given to those processes aimed at the production of clean syngas for the subsequent synthesis of high-value products, including bio-hydrogen, synthetic natural gas, and liquid fuels.
Understanding particle properties and powder behavior during handling and processing requires the characterization of the inner-core and surface properties. Most routine characterization methods involve the former. However, the dynamic behavior of large collections of particles, even if they are much larger than the nanoparticle scale, are dominated by their surface energy at the bulk (square meter, not microscopic) level. Bulk-surface energy of powder blends can differentiate between uniform mixing and the system’s inability to reach mixing equilibrium. Single-particle microscopic characterization techniques, while excellent complement to bulk-level methods, are not ideal for assessing surface energy in connection to properties like powder flow. However, microscopic techniques are invaluable in predicting some bulk-level properties of powders, such as the specific type of surface exposed when powders are subjected to processes such as milling.