The influence of fiber on PM2.5 filtration performance

With the rapid development of my country's industrialization, in the residues emitted during combustion during daily power generation, fuel combustion in industrial and mining enterprises, automobile exhaust emissions, and smoking smoke release, there are inhalable particulate matter whose diameter is less than or equal to 2.5 μm (referred to as PM2. 5) The fine particles, due to their large number, slower sedimentation rate, and large specific surface area, can be used as carriers for other pollutants, enriching toxic heavy metals, organic pollutants, germs, acid oxides, etc. Particulates can damage respiratory function, cause inflammation, asthma and other respiratory diseases, increase the prevalence and mortality of heart disease, and have potential carcinogenicity, which has a great impact on human health and the quality of the atmospheric environment [1], so Research on how to effectively remove PM2.5 is of great significance in industrial production and life [2-4]. The current related research shows that the fiber filtration method has a better effect on intercepting PM2.5. Therefore, this paper analyzes its impact on the PM2.5 filtration performance from two aspects of single fiber and fiber assembly. Many scholars at home and abroad have studied the fibers in the fiber filter media based on the two-dimensional model [5-7], but the fibers of the actual fiber filter media are randomly distributed in three dimensions. Baumgartner et al. [8] carried out a three-dimensional numerical simulation of multi-phase dispersed aerosol particles and proposed the concept of deposition spread on filter fibers. Fotovati et al. [9] used the CFD simulation method to study the cross-sectional shape of the single fiber filament and analyzed its filtration performance. This article uses three-dimensional modeling for both single fiber and aggregate. Among them, because the triangular cross-section fiber is widely used in filtration [10-11], the model of 'Y'-shaped cross-section and circular cross-section of different sizes is established for a single fiber to compare and analyze different filament linear densities, flue gas flow rates, and particulate matter. The influence of concentration on the filtration performance of PM2.5, and the law of movement of PM2.5 particles and the law of velocity distribution of the fibers around the flue gas are obtained. Considering that the fiber with a circular cross-section is the research object in the classical filtration theory, and the complexity of the modeling of the special-shaped fiber body, the cylindrical fiber body is used to analyze the linear density, porosity, particle concentration and suction speed of the fiber body. Impact on PM2.5 filtration performance. The fibers in the fiber assembly are randomly distributed, and the gas-solid two-phase flow inside is simulated. The Euler method is used to treat the gas field, and the Lagrange method is used to treat the discrete particle field. Comparing the experimental data with the numerical simulation results can not only verify the reliability and rationality of the numerical simulation, but also provide a certain reference basis for the selection of the shape and size of the filter fiber and the optimization of the internal structure of the aggregate in the future, so as to go further Improve the filtration efficiency. 1 Experimental part 1.1 The experimental method of monofilament The monofilament under different working conditions is fixed on a small holder along the vertical airflow direction, and the fiber filaments are photographed under the microscope at the observation point every 1 minute, and the photographs are taken Binarize the picture of the picture, that is, set the gray value of the pixel on the image to 0 or 255, and the total pixel value of each picture does not change. If the filaments are attached to the particulate matter, the pixel value of the corresponding point changes. Finally, the number of pixels of the black dots covered by the particles is counted, and the ratio of this value to the number of pixels occupied by the fiber filaments is the coverage rate of the particles, which can be used as a reference for studying the filtration performance of single fiber filaments. 1.2 Experimental conditions of single fiber filaments Because the smoke generated during the combustion process of cigarettes contains mainstream smoke aerosols during inhalation and sidestream smoke aerosols during smoldering (static combustion), the experiment uses smoke aerosols Particles, and ELPI was used to measure the concentration of particles produced during a single cigarette’s static combustion. Among them, the three-lobed filaments of the cigarette fiber filter have an angle of 120° at the cross-links of the two slender leaves [12]. 20 filaments are randomly selected and the diameters of the inscribed circle and the circumscribed circle are measured. Different sizes of 'Y'-shaped monofilament yarns are shown in Figure 1. The single fiber filaments of different sizes and linear densities were placed under the conditions of different particle concentration and flue gas flow rate to conduct experiments. The experimental conditions are shown in Table 1. The linear density of monofilament has its own specific definition, and its physical meaning refers to the mass (g) of a 1000 m long monofilament, and the unit is tex. 1.3 Experimental results of monofilament yarn 1.3.1 The influence of linear density on the filtration performance of particulate matter As can be seen from Figure 2, as time increases, monofilament yarns with different linear densities increase the coverage rate of particulate matter correspondingly, and the initial particulate matter coverage rate increases rapidly. , As time accumulates, the coverage rate of particulate matter tends to stabilize. At the same time, the filament with a linear density of 0.27 tex has the best interception efficiency for particulate matter. The greater the linear density of the monofilament, the lower the coverage rate of particulate matter. The difference between the maximum coverage of the monofilament linear density 0.27 tex and 0.38 tex reached 36.7%, and the particle coverage of the monofilament linear density 0.27 tex at the 9th minute was 94.6%. The monofilament linear density 0.30 tex and 0.33 tex have similar trends, and the particle coverage rate of the monofilament linear density 0.30 tex is slightly higher than the linear density 0.33 tex.