Elsevier

Powder Technology

Volume 395, January 2022, Pages 207-217
Powder Technology

Research on the influence of pleat structure on effective filtration area during dust loading

https://doi.org/10.1016/j.powtec.2021.09.062Get rights and content

Highlights

  • The effective filtration area (EFA) percentage decreases as the pleat ratio increases.

  • The threshold friction velocity surges with the decrease of dust particle size.

  • Larger dust particles deposit more easily at the pleat corners.

  • The uneven deposition reduces the decreasing rate of the EFA percentage.

Abstract

Filter cartridges are widely applied in the industrial dust removal system, and pleat structure plays a major role in expanding the filter area in limited space. In this study, the effect of pleat ratio (the ratio of pleat height to pleat pitch) on the effective filtration area (EFA) during polydisperse dust loading was analyzed. The results indicate that the dead zone formed by pleating will increase the structural resistance and reduce the EFA. When pleat ratio is 0.74–1.48, the EFA percentage varies slightly with the dust deposition per unit area (DDPUA). When pleat ratio is 2.22–3.70, the EFA percentage decreases with the increase in DDPUA. The threshold friction velocity surges with the decrease of dust particle size, and the larger the pleat ratio, the more easily for larger dust particles to deposit at the pleat corners, leading to the reduction of the EFA percentage decreasing rate.

Introduction

Due to the requirements for high-quality living environment, dust removal systems are widely adopted in industrial production and people's lives [1,2]. Filter dust removal is widely used in bag filter, HVAC system, air purifier, etc. for its simple structure, good filtering effect and large processing air volume [[3], [4], [5]]. The filter cartridge, which is an important part of the filter dust removal system and is generally made of pleated filter material, determines the performance of the dust removal system [6,7]. Compared with plane filtration, pleated filtration boasts a larger filtration area, a greater dust capacity, a lower filtration velocity and a smaller pressure drop [[8], [9], [10], [11]]. It is applicable to limited space and is widely used in industrial dust removal systems because its pleated geometric structure results in a smaller volume of the filter cartridge for the same filtration area [9,[11], [12], [13]].

The performance of pleated filtration is not only influenced by the pHysical properties of the filter material (thickness, air permeability, etc.) and its usage environment (filtration speed, dust concentration, etc.), but also related to the pleated structure [14,15]. Alilou et al. [16] and Del Fabbro et al. [17] found that the pleated structure had a huge impact on the pressure drop and largely increased the air velocity in the pleated channel. Bourrous et al. [18] studied the effect of filtration velocity on the pleat deformation and the effective filtration area, and reported that under a filtration velocity of 0.04 m/s, the effective filtration area is the largest. Subrenat et al. [13] conducted a three-dimensional numerical simulation study on the flow field of a cylindrical pleated filter and divided the filter bag into three zones (preferential airflow zone, useful zone, and dead zone) based on different filtering velocities. Among them, the dead zone located at the pleats is a region where the filtration velocity approaches 0, which reduces the EFA.

In addition to the influence of filter material pleats on the EFA, the uneven deposition of dust on the filter material surface induced by the geometric structure of pleats also has a certain impact on the EFA. Many scholars have studied the uneven deposition of dust during pleated filtration. Li et al. [2] investigated the pleat bag filter, and reported that the larger the pleat ratio, the smaller the pleat pitch, and the more easily for the dust particles to deposit at the pleat corners. Fotovati et al. [7] theoretically studied the influence of dust deposition on the surface of pleated filter material, and found that a high pleat ratio would lead to a high airflow velocity in the pleat channels, resulting in the uneven deposition of dust. However, none of previous studies has carried out a quantitative investigation on the change of the EFA during the uneven deposition of dust.

In this study, the loss of EFA caused by filter pleats and the influence of uneven deposition of different-sized dust on the EFA were quantitatively analyzed through a comparison between filtrations under different pleat ratios and plane filtration.

Section snippets

Experimental system

The dust filtration experiment system (Fig. 1) fell into three parts, namely a dust generation system, a filtration system and a monitoring system. The dust generation system consisted of an air compressor, a drying tube, a pressure-reducing valve, a flow rate regulation valve R1, a float flowmeter F1, a solid particle dust generator (9309, TSI, the USA), a dust mixing chamber, a centrifugal fan C1, etc. First, high-pressure air from the air compressor was adjusted to constant-pressure

Effect of pleat ratio on pressure drop and EFA percentage

The pressure drops of filter cartridge under different pleat ratios were experimentally measured in the filtering airflow velocity range of 1– 7 cm/s, and the measurement results are shown in Fig. 5. The pressure drop increases linearly with the filtering airflow velocity, and the higher the pleat ratio is, the faster the pressure drop surges. The fitting Eq. is obtained by fitting the data through Eq. (4). The slope of the fitting straight line is the resistance coefficient of the filter

Conclusions

  • (1)

    The resistance coefficient of the filter cartridge ranges from 9.387 to 10.651 Pa·s/cm, and the larger the pleat ratio, the smaller the EFA percentage. At the same time, when the pleat ratio rises, the channel in pleats shrinks, resulting in an increase in both airflow velocity in pleats and structural resistance. The EFA percentages are 93.2%, 91.8%, 88.8%, 88.3% and 88.1% under the pleat ratios of 0.74, 1.48, 2.22, 2.96 and 3.70, respectively.

  • (2)

    The total pressure drop increases with the rise of

Declaration of Competing Interest

The authors declared that they have no conflicts of interest to this work.

We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.

Acknowledgements

This study was supported by the National Natural Science Foundation of China (No. 51774274, 52074279, 51904291), the Fundamental Research Funds for the Central Universities (No. 2017XKQY026, 2020XGYJ08), the Basic Research Program of Jiangsu Province (No. BK20190638), and the Education Department of Hunan Province (No. 17C0429, 17C0453).

References (30)

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