Clean Filter Research Articles

A Portable Ultrawideband Confocal Raman Spectroscopy System with a Handheld Probe for Skin Studies.

Confocal Raman spectroscopy (CRS) has shown potential in non-invasive skin analysis. However, current CRS systems have various limitations including a narrow detection band, large size, non-flexibility, slowness, and complexity, which hinder their clinical applications. Herein, we developed a portable ultrawideband CRS system with a fiber-based handheld probe to acquire the Raman spectra in both fingerprint and high wavenumber regions in a fast and quasi-simultaneous way. Dual-wavelength excitation with a dual-passband laser cleaning filter and high-speed fiber array multiplexer was adopted instead of a specialized grating and detector to achieve instant switching between the detection regions and improve system robustness. Preliminary in vivo results demonstrated its depth profiling capability in an ultrawide detection range for stratum corneum thickness, natural moisturizing factor, and water content quantification, indicating its great potential in a wide range of clinical and cosmeceutical applications.

Auxeticity in biosystems: an exemplification of its effects on the mechanobiology of heterogeneous living cells

Auxeticity (negative Poisson’s ratio) is the unique mechanical property found in an extensive variety of materials, such as metals, graphene, composites, polymers, foams, fibers, ceramics, zeolites, silicates and biological tissues. The enhanced mechanical features of the auxetic materials have motivated scientists to design, engineer and manufacture man-made auxetic materials to fully leverage their capabilities in different fields of research applications, including aeronautics, medical, protective equipments, smart sensors, filter cleaning, and so on. Atomic force microscopy (AFM) indentation is one of the most widely used methods for characterizing the mechanical properties and response of the living cells. In this contribution, we highlight main consequences of auxeticity for biosystems and provide a representative example to quantify the effect of nucleus auxeticity on the force response of the embryonic stem cells. A parametric study has been conducted on a heterogeneous stem cell to evaluate the effect of nucleus diameter, nucleus elasticity, indenter’s shape and location on the force-indentation curve. The developed model has also been validated with the recently reported experimental studies available in the literature. Our results suggest that the nucleus auxeticity plays a profound role in cell mechanics especially for large size nucleus. We also report the mechanical stresses induced within the hyperelastic cell model under different loading conditions that would be quite useful in decoding the interrelations between mechanical stimuli and cellular behavior of auxetic biosystems. Finally, current and potential areas of applications of our findings for regenerative therapies, tissue engineering, 3 D/4D bioprinting, and the development of meta-biomaterials are discussed.

Analysis of the microstructure and elemental occurrence state of residual ash-PM following DPF regeneration by injecting oxygen into non-thermal plasma

Particulate matter (PM) capture tests were carried out on clean diesel particulate filters (DPFs) under different loads (25%, 50%, 75% and 100%). DPFs were regenerated by a non-thermal plasma (NTP) injection device. Raman spectroscopy and x-ray photoelectron spectroscopy were used to investigate changes in the microstructure and element occurrence state of the sediment in DPF channel before and after regeneration. The order of the PM samples decreased before NTP treatment as the load increased; the amorphous carbon content was high, and the oxidation activity was higher. After NTP treatment, the carbon atoms at the edge of the microcrystalline structure in the ash-PM samples were oxidized, and the structure was reorganized; in addition, the amorphous carbon content decreased, and the structure was more diversified. Before NTP, the C element of PM samples was the main component, and the content of the O element was relatively low. The C element occurred in the form of C–C, C–OH, and O–C=O functional groups, and O atoms were mainly combined with C–O. After NTP, the content of Na, P, S, Ca, and other inorganic elements in ash-PM samples was prominent because C atoms were removed by NTP active substances. There were two forms of S element occurrence (SO4 2− and SO3 2−); the proportion of SO4 2− was approximately 40%, and the proportion of SO3 2− was approximately 60%. Study of the microstructure and element occurrence of the residues in the DPF channels improved our understanding of the mechanism of the low-temperature regeneration of DPF from NTP.

Structure characterization of the clogging process of coarse fibrous filter media during solid particle loading with X-ray micro-computed tomography

Fibrous nonwoven filters are widely used in various air filtration applications. Coarse filters are typically used to protect and extend the lifetime of high-efficiency filters. However, unlike high-efficiency filters, limited work had been carried out to study the evolution of filtration properties and filter structures during the clogging process of coarse fibrous filters due to the lack of non-invasive and non-destructive structural characterization techniques. In this study, a coarse nonwoven filter media with a 94.52% mean porosity value was fabricated. The filtration properties of the studied coarse filter, including pressure drop and filtration efficiency, were found to increase along with the particle loading. The X-ray micro-computed tomography (XMCT) was used to non-invasively characterize the 3D structures of clean and particle-loaded fibrous nonwoven coarse filters at different clogging stages. Although the surface area scanned by XMCT (research of interest, 600*600 µm2) was a tiny spot on the whole filter media, this surface area exhibited good representativeness of the average structural properties of the whole filter media, e.g., porosity in this study. Depth profiles of local porosity and particle solidity across the full thickness of filter XMCT image indicated that at the beginning of particle loading stages, particles were captured and trapped by the top part of filter thickness, which was corresponded to the reported clogging process of high-efficiency filters. Then particles could be found across the full filter thickness. However, during the transitioning from the depth filtration stage to the surface filtration stage, clogging with high particle solidity was found in the bottom part of filter thickness. As more particles were loaded, clogging was found in both the middle and bottom parts. After that, the top part would be clogged, and the surface cake would start forming thereafter. This is the first report of the clogging process of the fibrous nonwoven coarse filter. Pore diameter distribution derived from the pore skeleton network via skeletonization of the 3D particle-loaded filter structures also described the same structure evolution during dust loading.

Nanofibrous Mats for Particulate Matter Filtration

Biomass consumption and fossil fuel combustion are key contributors to particulate matter (PM) pollution, resulting in ecological disturbances, climate change, and an increase in serious global health problems, related to common respiratory and cardiovascular diseases. Strategies have been initiated to curb the filtration of PM. Specifically, nanofibrous mats render high filtration efficiency for removing PM from the gas stream due to their low basis weight, wide area to volume ratio, and small pore size. In this review, we holistically took into account the raw materials and fabrication techniques of nanofibrous filters constituting electrospinning, blow spinning, and natural/freeze-drying. We highlighted the mechanism of PM capture and the basic parameters for PM filtration which entail efficiency removal, pressure drop, quality factor, and reusability. Additionally, challenges in filter cleaning, low airflow rate, and filtration efficiencies, coupled with future perspectives using biobased nanofiber mats still need to be addressed going forward.

Concentrations and size-resolved I/O ratios of household airborne bacteria and fungi in Nanjing, southeast China

This work quantitatively investigated the concentration relationships between indoor and outdoor bioaerosols in residence. We measured bacteria and fungi from air in 28 residential homes throughout Nanjing, southeast China during summer and winter. The culture-based method was applied and the ratios of indoor to outdoor concentrations, expressed in I/O, were calculated. Results revealed that concentrations of indoor bioaerosols were significantly associated with outdoor bioaerosols, and their size distributions showed similar single-peak pattern. Spearman correlation analysis indicated that I/O ratios were positively related to indoor microbial concentration. The I/O ratios differed insignificantly from seasons, but significantly higher I/O ratios were observed in airborne bacteria rather than airborne fungi during the same season. For bacteria, as much as 89% of homes in summer and 67% of homes in winter have I/O ratios >1, while for fungi, more than half of homes have I/O ratios <1, i.e. 50% in summer and 73% in winter. The different size distribution of bacteria and fungi could make a difference in I/O ratios. The greater percentage of I/O > 1 was observed in smaller size of bacteria and greater percentage of I/O < 1 was observed in larger size of fungi. The significant difference of I/O ratios between bacteria and fungi revealed that airborne bacteria being mainly originated from indoor sources, but airborne fungi dominantly from outdoor sources. Among various housing operations, the window opening period per day, the usage of air cleaner, and indoor planting played significant roles on I/O ratios, but the frequency of HVAC filter cleaning and the housing cleaning as well as the occurrence of mold played insignificant roles in this study.

Evaluation of an airborne alpha and beta particle detection capability using an environmental continuous air monitor system

We evaluate the ability of the Canberra Alpha Beta Environmental Continuous Air Monitor (ECAM) to detect and quantify airborne radiological contamination. The ECAM essentially consists of a passively-implanted planar silicon (PIPS) detector near a particulate filter through which outside air is pulled. Three years’ worth of background measurements on three different systems were assessed and calibrated to compensate for changing conditions and develop an average background response for the systems. The ECAM was also exposed to several radionuclides of interest, including 235U and 239Pu, to measure the response to alpha and beta particle sources. Both standard calibration sources and custom sources consisting of aqueous radioisotope solutions absorbed into clean filters. The ECAM responses to these sources were then scaled to quantities of interest and injected on the averaged background. Various alarm algorithms were evaluated on the source-injected spectra for minimum detectable air concentration for a given false alarm rate. Even in the worst case, the ECAM was able to detect radionuclides of interest at 10% of the Derived Response Level (DRL) for each isotope based on early-phase Protective Action Guides (PAG). Quantification of the radionuclides was also evaluated for the various algorithms, with mixed results, but overall clearly indicating the optimal algorithms for alpha and beta particle alarm and quantification. Finally, a limited evaluation of the beta particle detection efficiency points to a detection energy threshold of approximately 290 keV.

A Novel Methodology for Online Analysis of Amine Solution Degradation Caused by Fly Ash

Two research goals were set for this study. (1) The first goal was to develop a reliable and cost-effective online analytical technique to measure amine solvent concentration, loading, and to quantify the amine degradation process based on Gas Chromatography (GC). (2) The second goal was the investigation of amine degradation in the presence of fly ash, which includes: the identification of proper chemistry of degradation; and, the identification and quantification of the degradation products of the amines. For this study, aqueous monoethanolamine (MEA) and aqueous methyldiethanolamine (MDEA) have been selected. To accomplish the first goal, an online analytical technique to quantify the amine solvent chemistry based on Gas Chromatography (GC) was developed and set up in the lab. An automatic liquid sample injection system was attached to the GC to study the impact of the concentration of fly ash on the degradation process of two well-known amines (MEA and MDEA) by measuring the concentrations of amine, water and carbon dioxide (CO2). The flow system was equipped with filters to avoid the introduction of large particles into the GC column. A solvent back-flush system was used to allow for automated cleaning of the particulate filters. GC was then calibrated for the amine and water using various concentrations of aqueous amines (MEA and MDEA), and various CO2 loaded aqueous MDEA solutions and aqueous solutions of ammonium bicarbonate (NH4HCO3) were used to calibrate the GC for quantification of CO2 using a Total Organic Carbon / Total Inorganic Carbon (TOC/TIC) analyzer. To accomplish the second goal, two kinds of fly ash samples were collected from a coal burning power plant. Fly ash samples collected from the power plant were analyzed by SGS Canada Inc. ASTM methods were used to estimate the ash percentage, moisture content and elemental composition of the fly ash (silica and other metal oxides). A lab scale experimental setup was designed and developed to observe the influence of fly ash on amine-based solvents (MEA or MDEA) degradation.

Study of protective efficiency of respirator with forced air supply

The aim of the work was to conduct experimental studies aimed at determining the protection factor of the filter respirator with forced air supply by volunteers in different modes of operation and to establish the dependence of the amount of air supplied by the fan from the air purification device to the filter’s resistance. Simulation studies to determine the protective effectiveness of the filter respirator on the testers were performed according to the procedure for determining the penetration coefficient of test aerosol – sodium chloride, as the ratio of the submask concentration of test aerosol to the ambient concentration formed in a special chamber that meets the requirements of DSTU EN 13274. Determination of the amount of air supplied by the air purification unit to the submask space and assessment of the value of positive pressure inside the mask was performed according to the procedure described in DSTU EN 12941: 2004. As a result of simulated laboratory tests to determine the protective effectiveness of filter respirators with forced air supply to the testers, it was found that the average result of the protection factor of the test samples ranged from 99.93 to 99.97, which meets the requirements of DSTU EN 12941: 2004. In addition, it was found that the amount of air treated by the fan of the air purification device for clean filters is 165 and 215 dm3/min for operating modes “Normal” and “Turbo”, while for the polluted filters it is reduced to 131 and 185 dm3/min, respectively. During the study, the compliance of the value of excess pressure in the submask space with the requirements of DSTU EN 12941: 2004, which should not exceed 2.5 mbar, was confirmed. It is also determined that the stability of the technical parameters of the air purification device is maintained in the specified range when charging the “Dinogy Li-Pol 11000mAh 14.8V 4S 25C” brand battery not less than 12 V to ensure the current value of not less than 1.6 A. The practical value of the results lies in determining the duration of protective action of the filter respirator, the choice of filter resistance to establish the scope and modes of operation in the developed personal respiratory protection equipment.

Equipment for pulsed gas-and-chemical regeneration of water wells

The development of new methods for the regeneration and recovery of specific flow rate of water intake wells is an urgent task. Based on many years of the experience in well operation, it has been proved that all wells eventually need to be repaired. The main reason for such work is the chemical clogging of the filter and filter zone with different chemical compounds. The average stable operation period of new wells is 2–4 years. Better cleaning of filters and filter zones in water intake wells is achieved using the combination of hydraulic, impulse and vibration attacks with subsequent or concurrent chemical treatment. At this date, none of the integrated approaches enjoys wide application due to some disadvantages. At the Belarusian National Technical University, the pulse-and-chemical regeneration equipment has been designed for water intake wells. The technology involves electrolysis-induced explosion of a hydrogen–oxygen mixture at the well mouth on ground surface, feed of the mixture to a working chamber in the well filter, filling of a chemical reagent in the filter treatment zone and explosion of the reagent medium. The equipment has successfully passed laboratory and field tests.

Justification of theoretical and methodological aspects of using the tools of system analysis to ensure the protection of atmospheric air

The object of research is the degree of air pollution as a result of the work of enterprises of certain industries and the technology of their purification. One of the priority tasks is to ensure the country's environmental safety, but for its implementation it is necessary to minimize air pollution. For this, it is necessary to establish a full-fledged monitoring system, as well as modernize, maintain the functioning and control of air purification systems, polluted as a result of technological processes of enterprises of various industries. The work carried out the development of a methodology for control and selection of treatment equipment at the enterprise, using the tools of system analysis. Two scenarios of organizational and managerial actions have been identified using this technique. The first scenario – the purification degree of emissions of more than 90% – provides that the equipment available at the enterprise ensures a satisfactory condition of the air entering the environment as a result of production processes. If this scenario is realized, the main task is to maintain a high purification level of the plant's emissions. For this purpose, it is advisable at the enterprise to carry out:- constant monitoring of the operation and condition of air purification systems;- proper maintenance of equipment (timely replacement and cleaning of filters, etc.);- periodic training and advanced training of the personnel of the enterprise responsible for the operation of the equipment and the main technological processes of the enterprise.The second scenario – purification degree of emissions up to 90% – assumes that the equipment available at the enterprise is in an unsatisfactory condition and does not provide adequate air purification. If this scenario is realized, the algorithm of actions of the management and chief specialists of the enterprise should include such managerial and organizational actions– study and evaluation of scientific developments and modern treatment equipment available on the market;– comparison of technological characteristics of alternative equipment models and selection of the best option, taking into account regulatory requirements and production and technological limitations;– making a decision based on the results of a SWOT analysis.The effectiveness of the developed methodology has been established on the example of the meat processing industry.

Adhesion strength of soot particles to cellulose ester membranes determined by centrifuge technique

Adhesion forces between microparticles and substrates is a parameter of fundamental importance in studies of surfaces contamination and decontamination, filter and surface cleaning, non-contact sam...

Precoating for improving the cleaning of filter media clogged with metallic nanoparticles

Filtration of dust nanoparticles emitted from metallurgical processes is currently problematic, due to a rapid increase of the pressure drop and an inefficient filter cleaning, inducing high maintenance costs. This paper investigates the use of precoating technique to overcome the cleaning difficulties caused by the metallic nanoparticles. It consists of protecting the filter surface with a dust layer composed of micron-sized particles that is easily discharged upon cleaning. In this study, the pulse-jet cleaning of flat filters with and without precoating is evaluated. The aim is to determine the effect of operating conditions on the cleaning efficiency and provide guidelines on the application of precoating. Different precoating materials are tested, to determine whether the material choice is of influence. Experimental results highlighted the increase of the collection efficiency and dust holding capacity using precoating. The cleaning efficiency was significantly improved from 10 % without precoating to 90 % with precoating. Clogging/unclogging cycles showed that the use of precoating allowed stabilizing the filtration process.

Impact of multilayering on the filtration performance of clean air filter media

AbstractFibrous filter media are commonly used to remove airborne particles that are harmful to human health and the environment. Although filter media are often multilayered for various reasons, no systematic study of the impact of multilayering on filter media performance has been reported. In this paper, direct numerical simulations with the lattice Boltzmann method are used in order to shed light on the impact of multilayering on the performance of clean bimodal fibrous filter media in a Stokes flow regime. Virtual model clean filter media with up to eight layers and various fibre formulations are compared in terms of permeability or pressure drop, capture efficiency, and quality factor. A careful analysis of the results revealed that multilayering had no statistically significant impact on the performance of the clean filter media. At best, the impact of multilayering was similar to that of the inherent variability of such random structures. Fibre formulation was found to be a more efficient way of improving the performance of the filter media. Placing interlayered air gaps between fibrous layers also slightly improved the quality factor by facilitating the flow at the interfaces of the fibrous layers. These findings will guide future studies on the performance of multilayered filters with more complex flow conditions, such as those encountered with inertial or nanofibre‐made filter media and with the fouling of filter media.

Experimental operation and performance evaluation of waste remover in aquaculture ponds

The development of new technologies in automation to increase labor productivity has been increasingly enhanced in recent decades. The problem of cleaning water in shrimp ponds greatly affects the quality as well as shrimp production. Environmental pollution of shrimp farming is a matter of concern because the current waste treatment solutions are not yet thorough. A waste remover of shrimp waste combined with the pond bottom siphon method has been researched and developed to increase the ability to thoroughly handle waste generated in the culture environment. This device helps to automate the manual cleaning of the pond bottom by farmers. The device performs operations to clean waste, suck, filter, and remove waste from the culture environment. This device is self-propelled or manually controlled and operates in all weather conditions. This article introduces the process of testing and evaluating the efficiency of waste extraction equipment in shrimp ponds. The device was tested at a super-intensive shrimp farm and evaluated for operational efficiency. The experimental model consists of a shrimp pond operating a waste suction device, a control pond, an automatic monitoring system of water quality parameters (DO, H2S, NH3, pH, and temperature). Experimental ponds operating waste disposal equipment, control ponds are manually cleaned, other farming conditions of the two ponds are similar. The impacts of waste on the shrimp culture environment are determined through analyzing the results of measuring water quality criteria in the pond, thereby assessing the efficiency of waste removal of the equipment. The measurement results show that water quality parameters reach a value within the threshold if operating a waste suction device once per day. The benefits of waste remover operate to help save the cost of labor to clean the pond bottom, protect workers' health.

Numerical investigation of the impact of washcoat distribution on the filtration performance of gasoline particulate filters

A three-step numerical model sheds light on the impact of three-way catalyst washcoat distribution within the cordierite porous wall of a clean gasoline particulate filter on its filtration performance. The model relies on (1) the numerical reconstruction of porous wall sections with various washcoat distributions and coating amounts, generated using a novel set of morphological image processing operations applied on segmented X-ray computed tomography data, (2) the computation of the flow field using the lattice Boltzmann method, and (3) the prediction of soot capture efficiency by solving the Langevin equation. The impact of washcoat distribution and amount on the pressure drop, permeability, filtration efficiency, and filter quality factor is systematically investigated. For a non-uniform washcoat distribution, an unexpected decrease in filtration efficiency with an increase in washcoat amount is explained and this highlights the complexity of the effects generated by the deposition of washcoat within the porous wall of the filter.

The effect of husbandry shortcomings on oxygen supply in pet fish tanks

In order to investigate the suitability of standard fish tank setups for permanent keeping of ornamental pet fish, oxygen consumption and exchange rates were measured in a group of standard aquariums with a volume of 54 litres. The effects of defined disturbances on oxygen partial pressure in fish tanks were measured. These simulated typical beginners' errors such as a high stocking density, excessive feeding, insufficient filter cleaning, lack of water movement, and plant coverage of the water surface. Quantitative changes in oxygen partial pressure were measured in the tank as well as in a simplified model tank. Oxygen uptake rate of the tank (substrate, aquatic plants, bacteria, reduced substances) was not quantifiable in the experiment. The metabolism of the fish, which increased sharply with the feeding dose, exhibited the greatest effect on oxygen consumption in the fish tank. Oxidative conversion of nitrogen from ammonia to nitrate also caused a decrease in oxygen content, however to a lesser extent. Oxygen uptake from the atmosphere was significantly modulated by water flow rate and size of the diffusion area of the water surface. These results allow quantitative predictions concerning the interaction of fish stocking density and oxygen balance in standard commercial aquarium setups. Even under conditions of high stocking density, poor filter hygiene and excessive feeding, all tested tanks demon strated their suitability for permanent keeping of ornamental fish. Care is warranted, however, that water flow is maintained and its surface is not covered by plants. Ideally, the fish should be fed several small portions during daytime rather than a single large ration.

Regeneration of dust filters challenged with metallic nanoparticles: Influence of atmospheric aging

The aim of this study was to evaluate the regeneration efficiency of fibrous filters clogged with metallic ultrafine particles, as several complaints have been made by industrials in the metallurgical field about difficulties linked to the cleaning of filters. Aging of the dust deposits on the filters surface was also reported to be problematic. In this work, the metallic nanoparticles were generated by a pilot thermal spraying process using electric arc. Experiments were conducted on flat filters and the cleaning was performed using reverse pulse-jet. The regeneration efficiency was evaluated according to the residual pressure drop, the removed mass and the cleaned surface. Experiments revealed, under different conditions, a patchy inefficient cleaning of the clogged filters. The cleaning efficiency did not exceed 30 % according to the removed mass. Clogging/unclogging cycles showed that the filtration process is highly instable as the residual pressure drop kept increasing very rapidly. The influence of atmospheric aging, i.e. exposure to different humidity conditions over time, on the filter cakes was investigated. Results showed that in presence of humidity a chemical reaction was responsible for making the deposit more adherent. The regeneration efficiency was reduced to 10 % according to the removed mass after aging for 15 days under 80 % humidity rate.

Effects of relative humidity and particle hygroscopicity on the initial efficiency and aging characteristics of electret HVAC filter media

Because of the low pressure drop, electret filter media are widely used in indoor environments to remove particles for air quality control. The effects of water soaking, air relative humidity (RH), and particle hygroscopicity on the filtration performances of fresh and aged media, i.e., size-fractioned efficiency, however remains unclear. Electret media from a commercial high-efficiency particulate air (HEPA) filter, a commercial Heating, Ventilating, and Air Conditioning (HVAC) filter with minimum efficiency reporting value of 13 (MERV13) and a homemade filter (CM) were investigated in this work. In the initial test, the performance of above three media were evaluated at 10, 60 and 90% RHs. In the aged test, the media performances were characterized at 30, 60 and 80%, and using three different sample particles, i.e., hygroscopic NaCl, non-hygroscopic SiC, and NaCl + SiC mixture). In addition to clean filters, the collection efficiency and pressure drop of used MERV13 electret media, which had been utilized in a house for few months, were evaluated. SEM analysis was conducted to examine particle loading characteristics. The major finding of this study is that operating the filtration systems having electret media at ~60% RH can greatly enhance the particle holding capacity and minimize the efficiency decline. The result of this study provides the insights of the RH effects on the performance of electret media.

EXPERIÊNCIAS DE VISITA DOMICILIÁRIA EM ENSINO TEÓRICO PRÁTICO

This article aims to report experiences lived during home visits to residences in the city of Niteroi, located in the State of Rio de Janeiro, considering the social, structural and health specificities of each household investigated. Objective: to describe home visiting activities carried out by nursing students in the practical dimension of the collective health discipline offered to the undergraduate nursing course, with a view to highlighting possible risk factors for the illness of the studied public. Method: three visits were made in two different neighborhoods, two of them in the Atalaia neighborhood and one in Inga, to collect information regarding the health of the residents of these neighborhoods. Conclusion: a series of elements potentially harmful to the health of individuals was found, including clean filters, infiltrations, and exacerbated dust, which were observed in the visited homes. The presence of these factors ends up validating the importance of the practice of home visits, reflecting positively on maintaining the population's health and well-being.