One of the main challenges in the power and chemical industries is to remove generated toxic or environmentally harmful gases before atmospheric emission. To comply with stringent environmental and pollutant emissions control regulations, coal-fired power plants must be equipped with new technologies that are efficient and less energy intensive than status quo technologies for flue gas cleanup. While conventional sulfur oxide (SO x ) and nitrogen oxide (NO x ) removal technologies benefit from their large-scale implementation and maturity, they are quite energy intensive. Given this, development of lower cost, less energy intense technologies could offer an advantage. Significant energy and cost savings can be realized using advanced adsorbent materials. One of the major barriers to the development of such technologies remains development of materials that are efficient and productive in removing flue gas contaminates. In this review, adsorption-based removal of SO x /NO x impurities from flue gas is discussed while focusing on important attributes of the solid adsorbent materials as well as implementation of the materials in conventional and emerging acid gas removal technologies. The requirements of effective adsorbents are noted with respect to their performance, key limitations and suggested future research directions. The final section discusses some key areas for future research and provides a possible roadmap for development of more efficient and cost-effective technologies for removal of flue gas impurities than status quo approaches.
The production of particles with shape-specific properties is reliant upon the separation of micro-/nanoparticles of particular shapes from particle mixtures of similar volumes. However, compared to a large number of size-based particle separation methods, shape-based separation methods have not been adequately explored. We review various up-to-date approaches to shape-based separation of rigid micro-/ nanoparticles in liquid phases including size exclusion chromatography, field flow fractionation, deterministic lateral displacement, inertial focusing, electrophoresis, magnetophoresis, self-assembly precipitation, and centrifugation. We discuss separation mechanisms by classifying them as either changes in surface interactions or extensions of size-based separation. The latter includes geometric restrictions and shape-dependent transport properties.
We performed a numerical analysis to study the orientation distribution of a dilute suspension of thin, rigid, rod-like nanoparticles under shearing flow near a solid boundary of weak confinement. Brownian dynamics simulation of a rod was performed under various ratios of shear rate and rod diffusivity (Peclet number), as well as the center-of-mass position (wall confinement). We discuss the effects of Peclet number and wall confinement on the angle distributions, Jeffery orbit distribution and average orientation moments. The average orientation moments, obtained as a function of Peclet number and wall confinement, can be used to improve a previous shear-induced migration model. We demonstrate that the improved model can give excellent prediction of the orientation moment distributions in a microchannel flow.
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