Mass production of polyacrylonitrile sub-micron fibrous webs with different aligned degrees via free surface electrospinning for air purification

Atmospheric pollution has emerged as causing irreversible harm to the ecosystem and people. Sub-micron fibrous filters play an incomparable role in effective air purification, owing to their excellent internal connectivity. Herein, three-dimensional sub-micron fibrous webs with various aligned degrees were conveniently fabricated via free surface electrospinning with different rotation speeds of the roller with a large diameter in large quantity, applied in air filtration. The influence of the orientation degrees of fibers on the performances of the fibrous filter was analyzed systematically. Results showed that the filtration performance of fibrous filters was inversely proportional to the orientation degree of the sub-micron fibers. Random fibrous webs with areal densities of ≤2.0 g m−2 exhibited high porosity (∼90%), ensuring qualified air permeability and outstanding filtration efficiency from 92% to 99.5% for ultra-fine aerosol particles (∼0.26 µm) under a higher air velocity of 14.1 cm s−1. The internal aperture channels were twists and turns with irregular polygon shape for random fibrous webs, while they were a narrow strip in the horizontal and straight in the longitudinal for aligned ones, which influenced the filter’s performances. Fibrous webs with better orientation of fibers and larger pore size are beneficial for energy efficiency and exhibited good filtration performance, better air permeability, and an improved mechanical property along the longitudinal direction. A cost-effective uniform sub-micron fibrous filter with different aligned degrees could be produced rapidly via free surface electrospinning with a mass production rate, which is beneficial for industrial production and commercial applications in respiratory protection and indoor air purification for precise purification of air pollution.

Laboratory Determination of Coal Dust Cleaning Efficacy of a Fibrous Filter for Flooded-Bed Dust Scrubber

Fibrous-type dust filters are used in flooded-bed dust scrubbers to capture dust from underground room and pillar mining atmospheres. They have 10–30 layers of finely woven strands that trap particles through the interception and impaction process. A full-cone water spray is installed upstream of the filter, which floods the screen. A scrubber’s efficacy is usually measured and reported in terms of reduction in gravimetric dust concentration at a known location in a mine. This paper reports the particle-size-dependent dust removal efficiency of a fibrous filter obtained from an instrumented test-set up. A variable frequency drive and an inline flow control knob were used to control the airflow through the filter and water flow onto the filter. Optical particle counting of coal dust particles upstream and downstream was carried out to determine the cleaning efficacy. Experiments showed an increase in cleaning efficiency for all the dust particles with their size. A progressive decrease in dust concentration downstream of the filter with an increase in water flow through the nozzle affirmed the capture of dust particles by water sprays.

Method for analisis of the structure and properties of regenerated polimer fibrous filter for thin cleaning of airl

Stricter requirements for the quality and reliability of manufactured products, as well as the need to increase the service life of machines, mechanisms and various devices, the operation of which is associated with the use of liquid or gas-air media, is the reason for the emergence of new and improvement of traditional methods for obtaining filter materials with higher performance characteristics. A method for a comprehensive analysis of the properties of regenerated filter materials for fine air purification is proposed. The overwhelming majority of filters, after their service life is exhausted, cannot be regenerated, since this, as a rule, is associated with high energy costs. At the same time, the development of methods for such regeneration is quite relevant from the point of view of resource conservation. In this regard, the purpose of this work is to use a number of physical research methods for the purpose of a comprehensive analysis of polymeric fibrous filter materials for air purification that have undergone regeneration. Filtration materials obtained by the «melt-blowing» method from polymer granules by processing the granulate in an extruder, aerodynamic spraying of the melt and the formation of a fibrous-porous layer on a forming mandrel were selected for research. The main filtration characteristics of the original and regenerated filter materials (breakthrough coefficient, aerodynamic drag),as well as the electrophysical properties of the primary and secondary filter materials, the presence of a spontaneous electret charge have been investigated. The main stages of regeneration and evaluation of physicochemical, mechanical and operational properties of fibrous-porous materials that have undergone secondary thermo-aerodynamic processing in comparison with the original ones are described. It is shown that the studied materials retain their basic properties, while the structure of the fibers changes and the electret effect is enhanced.