Silica nanoparticles as a tool for fluorescence collection efficiency enhancement

In this work we demonstrate enhancement of the fluorescence collection efficiency for chlorophyll-containing photosynthetic complexes deposited on SiO₂ spherical nanoparticles. Microscopic images of fluorescence emission reveal ring-like emission patterns associated with chlorophyll-containing complexes coupled to electromagnetic modes within the silica nanoparticles. The interaction leaves no effect upon the emission spectra of the complexes, and the transient behavior of the fluorescence also remains unchanged, which indicates no influence of the silica nanoparticles on the radiative properties of the fluorophores. We interpret this enhancement as a result of efficient scattering of electromagnetic field by the dielectric nanoparticles that increases collection efficiency of fluorescence emission.     

不同工况下除尘器粉尘捕集效率模拟分析

旋风式除尘器的粉尘捕集效率一直是生产过程中的重要关注点.模拟计算分析不同工况、不同结构下装置内的压力、粉尘颗粒分布情况,研究其与粉尘捕集效率的关系.结论是:入口风速越大,压损越大;导流叶片的角度越大,压损越大,但压损增加幅度并不大;增加导流叶片,颗粒轨迹流线更加平滑,收尘效率更高.在一定工况条件下,通过增设内部导流叶片...     

The collection efficiency of a particle-loaded single filter fiber

The collection efficiency η(M) of single fibers, both isolated and within a parallel array, was determined as a function of accumulated particle mass for Stokes numbers St=0.3–3 and interception parameters In=0.04–0.32. This regime is dominated by inertia, interception and particle bounce. Measurements were made with an optical in-situ particle counting technique. Monodisperse polystyrene aerosols (1.3, 2.6, 3.6 and 5.2 μm) were deposited onto steel wires of 8 and 30 μm, respectively. Particle accumulation reached values on the order of M=0.5–1 μg/mm fiber, corresponding to 10⁴–10⁶ particles per mm, depending on size.η(M) was found to increase for all operating conditions between about 2 and nearly 50 fold, most strongly however for those conditions were the bare fiber is ineffective as a particle collector, i.e. for very low or very high values of St number, corresponding to low collision or low adhesion probabilities, respectively. The absolute efficiency increased to values approaching or exceeding unity, i.e. the effective fiber collision cross-section exceeded the diameter of the bare fiber. For fibers within an array of parallel fibers (equivalent packing density ∼0.004), the initial efficiency η₀ was higher than for an isolated fiber by almost an order of magnitude. However the increase with loading was substantially smaller, typically by an order of magnitude.The efficiency increase can be described by a power law of the type where b and c are empirical fit coefficients. Within an array, the exponent c is on the order of 0.7±0.05, but lower than reported in earlier work on fiber arrays which suggest a value near unity. For isolated fibers, c→1 as interception becomes dominant (at very low flow velocities) while at high impact velocities and significant particle bounce c≈0.5. The coefficient c correlates with fiber Reynolds number, but not with other parameters. The coefficient b is inversely proportional to η₀ (consistent with earlier work, however with significantly lower values than previously published) and a function of (St/R)².The experimental section of the paper is preceded by a literature review on single-fiber efficiency data and models for the inertia-interception regime, including both information on bare fibers and dust loaded fibers. An improved, general fit function with physically meaningful limits for St→0 and St→∞ is proposed for the efficiency of bare fibers.     

Effect of particle loading on the collection performance of an electret cabin air filter for submicron aerosols

Electret filters are composed of permanently charged electret fibers and are widely used in applications requiring high collection efficiency and low-pressure drop. We tested electret filter media used in manufacturing cabin air filters by applying two different charging states to the test particles. These charging states were achieved by spray electrification through the atomization process and by bipolar ionization with an aerosol neutralizer, respectively. Polydisperse solid NaCl particles with 0.1%, and 1% solutions or liquid dicotyl sebacate (DOS) particles were generated from an atomizer, and they were loaded on the filter media. The amount of charge, the mean particle size, and the particle material significantly affected the collection performance of the electret filter media for submicron particles. The collection efficiency of the electret filter media degraded as more particles were loaded, and showed minimum efficiency at steady state. The electret filter media captured the highly charged particles more efficiently during the transient state. At steady state, the filter media loaded with smaller NaCl particles showed lower collection efficiency. The filter media loaded with liquid DOS particles showed collection efficiency much lower than those loaded with solid NaCl particles.     

过滤除尘技术

讲述了空气粉尘、空气过滤器的特性、袋滤机理、袋滤器的性能及过滤材料的开发。     

Using a solution of the surfactant for increasing collection efficiency of coal dust in the exhaust system

Improved efficiency of aspiration systems in coal preparation shop (CPS) for dust capture during the unloading of coal due to the application of the surfactant solution. Selected optimum pattern of the surfactant and its concentration of the solution.     

旋风收尘器的收尘效率和生料粒度分布关系

旋风收尘器所分离的固相颗粒大小对分离效率的影响非常显著,通常情况下只对10μm以上的颗粒保持很高的分离效率,对直径小于6μm的细颗粒的分级效率相对较低。本文分析了不同公司的生料粒度分布情况,通过计算生料的粒级效率、中位粒径,并对C1旋风筒技改后的生产线收尘效率进行对比,分析旋风筒收尘器与生料粒度的关系。     

锌精矿焙烧收尘的设计

介绍了锌精矿酸化焙烧和高温氧化焙烧沸腾炉的设计特点 ,炉气冷却降温、焙尘收集及焙砂冷却设备的选用及设计实例。锌精矿酸化焙烧的焙烧强度一般选取 5 5～ 6 5t/ (m2 ·d) ,高温氧化焙烧取 7 0～ 7 5t/ (m2 ·d) ,两种焙烧形式的沸腾炉风帽密度、风帽小孔气速基本一致 ,分别为 6 5～ 75个 /m2 、40～ 5 0m/s     

Mechanical and electret properties of polypropylene unwoven fabrics reinforced with POSS for electret filter materials

A novel polypropylene/Polyhedral oligomeric silsesquioxanes (PP/POSS) composite unwoven fabric with permanent electret was prepared through melt-blown process with corona charging. Field-emission scanning electron microscope (FESEM) and wide-angle X-ray diffraction (WAXRD) were employed to investigate the morphology of the composite fibers and the distribution of POSS nanoparticles on the surface of the fibers, respectively. POSS acted as nucleating agent and accelerated the crystallization process during nonisothermal cooling. The utmost stable charge density of PP/POSS melt-blown unwoven fabric was improved by 78.4% compared with the neat PP unwoven fabric. The maximum value of collection efficiency measured by monodisperse polystyrene aerosol (PSL) (particle size: 0.3 μm) collection could reach 97.36% for PP/POSS composite melt-blown unwoven fabric, which improved by 9% compared with neat PP melt-blown unwoven fabric. Moreover, both stress and elongation at break of the PP/POSS melt-blown unwoven fabrics were improved compared with PP unwoven fabric.     

The Effect Of the dust collection system on the flowpattern and separation efficiency of a gas cyclone

The influence of the presence of a hopper section, consisting of a dust hopper and swirl attenuator, under gas–solid cyclones has been investigated by numerical simulation. Inclusion of this configuration in the simulations was found to have a significant influence on both flowpattern and separation efficiency. Moreover, predicted axial gas velocity profiles agreed better with independent experimental measurements. The cyclone separation was predicted to be better with the hopper section included than without, a physical reason is proposed. Comparison of simulated grade-efficiency curves with experimental data indicates improved agreement, in some cases substantially so.     

Evidence for enhancing charge collection efficiency with an alternative cost-effective binary ionic liquids electrolyte based dye-sensitized solar cells

To mitigate the mass transfer limitations of a highly viscous room temperature ionic liquid (RTIL) electrolyte, systematic characterizations of viscosity, ionic conductivity, apparent triiodide diffusion coefficient and photovoltaic response of an alternative cost-effective and highly conductive binary RTIL mixture of 1-ethyl-3-methylimidazolium trifluoroacetate (EMIATF) and 1-methyl-3-propylimidazolium iodide (PMII) were investigated. An emphasis was placed on the dynamics of electron transport and charge recombination processes; specifically, a focus was placed on the effective electron diffusion length and charge collection efficiency in the devices. Notably, the introduction of perfluorinated anions, with a strong delocalization of the negative charge over the anion backbone, was able to weaken the hydrogen bonding with the imidazolium cations and, thus, decrease the viscosity and increase the ionic conductivity of the electrolyte. A sealed device that employed the binary RTIL achieved an overall conversion efficiency of 5.22% under irradiation of 100 mW cm⁻², which increased the value by 30% compared to a device with a blank PMII-based RTIL electrolyte. Electrochemical impedance spectroscopy and intensity-modulated photovoltage/photocurrent spectroscopy analysis revealed that employment of this alternative binary RTIL electrolyte system was able to significantly decrease the diffusion resistance of triiodide species in the electrolyte and retard the charge recombination between the injected electrons with triiodide anions in the electrolyte, thus improving the effective electron diffusion length and charge collection efficiency in the device. The charge collection efficiency was certified to be the dominant parameter governing the short-circuit photocurrent density and the overall conversion efficiency of devices with RTIL electrolyte.     

Characteristics of the collection efficiency for a double inlet cyclone with clean air

Two single inlet cyclones and a double inlet cyclone were designed and fabricated to evaluate, and compare, their collection efficiencies. Two single inlet cyclones had different inlet sizes and vortex finder diameters. The double inlet cyclone had two inlet parts that divided the cyclone inlet in two. Clean air was introduced to the inlet near the cyclone wall, and particle-laden air was introduced to the inlet away from the cyclone wall. This double inlet made the clean air swirl in the region near the vortex finder, and the particle-laden air swirl in the region close to cyclone wall. The performance of the double inlet cyclone was evaluated at various clean air flow rates, keeping the particle-laden air flow rate constant.The collection efficiency of the double inlet cyclone was found to be 5–15% greater than that of the single inlet cyclone with the same inlet size and vortex finder diameter. As the flow rate of clean air was increased, the collection efficiency increased. This result indicates the possibility of achieving higher collection efficiencies with a double inlet cyclone.     

Waste heat recovery from flue gases with substantial dust load

Heat recovery is accomplished in a newly developed heat exchanger THERMOWIR. THERMOWIR consists of a large number of channels. Vortices are generated within the THERMOWIR and the dust is thrown to the walls of the THERMOWIR, thus keeping the center of the channels dust free, where the heat transfer tubes are located. A demonstration unit with 1 MWe capacity is being installed at present in a cement factory.     

Fabrication of cordierite filter by in-situ solidification for high temperature dust collection

Cordierite ceramic filters have been shown a potential candidate for a high temperature dust collection, owing to its very low thermal expansion coefficient characteristic as an attribute of excellent thermal shock resistance. It is preferable that a design of porous cordierite filter should have low pressure drop with high permeability while keeping the structural integrity. This study describes a simple and direct approach for fabricating a porous cordierite filter with honeycomb-type structure by introducing various non-through holes into mechanically foamed slurry, which is subsequently in-situ solidified by polymerization reaction. The gelcasting cordierite-based slurry was mechanically foamed in nitrogen-filled chamber. The resulting foamed slurry was cast directly into circular molds equipped with a cover having different number of pins. The gelled-bodies were carefully dried at 25 °C with a controlled humidity, followed by sintering under optimized condition. The dust collection performance, pressure drop, and gas permeability were evaluated as a function of the number of non-through holes in porous cordierite. Based on the results of the tests, the holey porous cordierite filter offered a better filter design for dust collection application.     

Effects of an external electric field on the collection efficiency of air filters: Filtration mechanisms with an external e-field

An external electric field was applied on the filter to improve its collection efficiency, and the collection efficiencies of the different filters under various conditions were evaluated. Dominant electrical filtration mechanisms for each condition were investigated using experimental and theoretical approaches. Four types of air filters were used as test filters: a charged fiber filter, a low-grade filter with 50% collection efficiency in the most penetration particle size (MPPS) zone, and two high-grade filters with more than 95% collection efficiency in the MPPS zone. Three different particle charge states—neutralized, single-charged and uncharged—were considered. For neutralized particles, the external electric field led to a 14.5%p. and 2.5%p. increase in the collection efficiencies of the low-grade filter and charged fiber filter, respectively. With the electric field, the collection efficiency of the low-grade filter increased by 30%p. for single-charged particles. The electric field also affected the collection efficiencies of the charged filter and high-grade filters, but the effect was not significant. For uncharged particles, the electric field did not lead to a remarkable increase in the collection efficiencies of any of the filters. Through experimental and theoretical analysis, it was found that the polarization force imposed on the charged fiber was the dominant factor for the charged fiber filter regardless of application of the external electric field. The Coulombic force imposed on the electric field was the dominant factor for the low-grade filter, while both the Coulombic and the polarization forces affected the collection efficiency of the high-grade filter.

Copyright © 2017 American Association for Aerosol Research     

聚丙烯中空纤维膜气体除尘性能

以气体除尘为研究背景,采用平均孔径为0.22 μm的聚丙烯（PP）中空纤维膜为过滤介质,考察了粉尘浓度、过滤气体流速、膜组件装填率、膜壁厚对膜组件除尘性能的影响。结果表明,气体通量随粉尘浓度变化较小,除尘率随粉尘浓度增大而提高、随过滤气体流速增加而减小;气体通量和除尘率均随膜壁厚增大有所增加,并随装填率增加而减小。PP中空纤维膜用于气体除尘其除尘率高达99.9%以上,其中对0.3 μm以上粉尘的截留率均可达到100%,对0.3 μm以下粉尘的除尘率可达99%。     

立窑除尘技术的现状和电除尘技术的进展

我国立窑厂有生产许可证的和无生产许可证的已近万家,年产水泥量占我国年产水泥总量的80％以上。以1998年我国水泥总产量5．3亿吨计算,立窑厂的产量约4．2亿吨以上。立窑粉尘的排放量如按立窑产量的4％计算,则立窑粉尘的年总排放量就高达1600万吨,据不完全统计立窑的粉尘排放量达到标准的不足2％。虽然国家经贸委已决定1997年淘汰3500多台直径小于2．2m的立窑,