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Electrospun Bio Nanofibers for Air Purification Applications
Published in K.M. Praveen, Rony Thomas Murickan, Jobin Joy, Hanna J. Maria, Jozef T. Haponiuk, Sabu Thomas, Electrospun Nanofibers from Bioresources for High-Performance Applications, 2023
Madhura Bhattacharya, Shivam Sinha, K. Anand
An air filtration mechanism involves separating certain impurities and dust particles from air by means of a filtration media. A filtration media or membrane in the filter performs this separation. The sizes of pores (empty structures) on these membranes determine the sizes of particles that are to be transported from the filter. The main requirements for selecting a filter are the accuracy of filtration and the amount of pressure drop (level of air resistance) associated with the filter. The pressure drop varies with size, surface area and other physical parameters of the filtering medium. Removal of particles by fiber-based filters (where the filtering membrane is made of fiber) involves several mechanisms depending on the size of particles to be removed. The mechanisms are as follows.
Particulates
Published in Charles E. Baukal, Industrial Combustion Pollution and Control, 2003
Filters are a mechanical separation device used to remove particles from gas streams. The principle behind filters is simple—the holes in the filter are large enough for gas to pass through but too small for particles to go through (although as discussed below sometimes even the particles could pass through the holes); hence, the particles get trapped on the surface of the filter. The filter is composed of any suitable porous material including granular or fibrous materials. The filter material must be compatible with the gas and particles. Common filter fabrics include wool, cotton, nylon, glass fiber, and polyester. The filters may be arranged in deep beds, mats, or fabric, all having large void spaces. Donovan [42] has written an entire book on using filters to remove pollutants from combustion sources. He notes the difference between fabric and textile filters, including structural and material composition differences. The U.S. EPA has prepared a manual for use in estimating the cost of various air pollution control techniques, which includes a chapter on baghouses and filters for particulate emission control [43].
Filtration: The Underutilized IAQ Asset
Published in H.E. Burroughs, Shirley J. Hansen, Managing Indoor Air Quality, 2020
H.E. Burroughs, Shirley J. Hansen
Life Cycle Cost Assessment (LCCA), widely used in the Green Building movement to express the entire ecological cost impact of a product, is also applicable here. The analysis of the real cost of a filtration system must, therefore, include in addition to its initial cost, its efficacy, labor, life cycle, energy demand, as well as the ecological effect from cradle to grave. The latter may take the form of raw material depletion, environmental effect from manufacturing, cost of solid waste disposal and the inherent energy burden. In certain locations where solid waste disposal is a major issue, filters must be completely disassembled into their components to facilitate recycling.
Filtration of aerosol particles by parallel and staggered filter arrays
Published in Aerosol Science and Technology, 2022
Manabu Nishimura, Yajiao Liu, Masao Gen, Takafumi Seto, Yoshio Otani
As mentioned above, the parallel and staggered filter arrays show distinctive filter performance: the changes in ΔPT in the filter arrays are negligible, and their collection efficiencies are relatively high (∼70%). In contrast, the monolith filter array has a high collection efficiency and a monotonic increase in ΔPT with dust loading. Here, we further discuss the filter performance in terms of the spatial distributions of internal pressure drops between the flow paths, as indicated by ΔP(L) (Figure 2), and the flow resistance across the filter material. Particles can be captured by the filter material when a particle-laden flow passes through the filter material. In the parallel and staggered filter arrays, filtered flow (Ff) is expected to be faster than parallel flow (Fout) when the collection efficiencies are high, as shown in Figure 5b (i.e., Ff > Fout). Note that Fout in the monolith filter array is negligible (Figure 5a).
Modification of the commercial polyester filter media support with electrospun polyethylene terephthalate fibers and its application for air purification
Published in Science and Technology for the Built Environment, 2022
Wei Lin Ng, Lei Zhou, Abu Bakar Sulong, Eng-Poh Ng, Soon Huat Tan
All filters need to be replaced regularly after airborne pollutants clog the filter media. An increment in airflow resistance and filtration efficiency occurs along with many air pollutants loading (Song and Shim 2021). The airflow resistance, which reduces the volume of air in the room, can be overcome by increasing blower speed to maintain the volume of air in the room. However, the increase of air pollutants forms a dust cake on the air filter’s surface and increases the airflow resistance. The air filter should be replaced when the blower cannot overcome the air resistance. If it continues to operate, there will be no adequate airflow into the room, and finally, the air filter will burst.
Evaluation of particle filtration efficiency of commercially available materials for homemade face mask usage
Published in Aerosol Science and Technology, 2021
Taekyu Joo, Masayuki Takeuchi, Fobang Liu, Matthew P. Rivera, Joy Barr, Emily S. Blum, Eric Parker, John H. Tipton, Julia Varnedoe, Bahnisikha Dutta, Ryan P. Lively, Nga Lee Ng
Particle filtration efficiency of different types of filters is shown in Figure 2f. Among the tested filters, HEPA filters report the highest particle filtration efficiency followed by MERV 13 filter and coffee filter. Typically, HEPA and MERV 13 filters are made of fibrous materials. These filters are commonly used in heating, ventilating, and air-conditioning (HVAC) systems. MERV 13 filter is designed to filter 90% of particles in the 3 − 10 µm range, 85% of particles in the 1 − 3 µm range, and 50% of particles in the 0.3 − 1 µm range (ASHRAE 2017). Although the shape of filtration efficiency curve of MERV 13 filter in Figure 2f is different from some previous studies (Azimi, Zhao, and Stephens 2014; Stephens and Siegel 2013), the shape of the curve is dependent on the manufacturers of the filters (Fazli, Zeng, and Stephens 2019). The filtration efficiency of 0.3 − 1 µm particles for the MERV 13 filter tested in our study is 81%, in accordance with the ASHARE rating. HEPA filter, which can be classified as MERV 17 to 20 rating (Hecker and Hofacre 2008), shows overall filtration efficiency of 96%, comparable to N95 respirators (Figure 2 and Supplementary Figure S1). A recent study that tested fibrous materials also reported that the particle filtration efficiency of vacuum bag is comparable to KN95 or N95 respirators (Hao et al. 2020). The coffee filter (Melitta) tested in this study shows decent particle filtration efficiency of 40%, for overall 58% at 300 nm, and a minimum of 31% at 88 nm. Such filtration efficiency is comparable to blue surgical mask, but the size-dependent filtration shows that the coffee filter shows better filtration performance for particles larger than 100 nm but the opposite for the smaller particles (Figure 2f). Coffee filters has other brands (e.g., Natural Brew, Brew Rite, etc.) were tested by Hao et al. (2020). Although filtration efficiency of multiple layers (three layers) of coffee filters was evaluated by Hao et al. (2020), they reported a lower filtration performance, smaller than 30% at 300 nm at a face velocity similar to this study. Therefore, it appears that the filtration performance of coffee filters can be highly dependent on the brand/manufacturer.