Experimental Parametric Study of Frequency and Sound Pressure Level on the Acoustic Coagulation and Precipitation of PM2.5 Aerosols

Abstract

The efficiency of particle removal for PM 2.5 aerosols using conventional separation systems is generally low. In this paper, acoustic precipitation and coagulation of aerosols as a preconditioning system is investigated experimentally. The results of experimental study concerning the effect of frequency and sound pressure level (SPL) on the acoustic coagulation and precipitation of PM 2.5 aerosols are presented. An acoustic particle conditioning setup was used to perform experiments at the resonance frequencies of 204, 550, 650 and 749 (Hz), and SPLs 140, 150, 155, 162 dB. All experiments were performed under ambient condition and similar initial concentration. The experimental results showed that the effect of acoustics on filtration efficiency is amplified by increasing the frequency and intensity. Eventually, at the frequency of 749 (Hz) and 162 (dB) the acoustic coagulation and precipitation efficiency reaches about 83% which is significant. The results of this study (experimentally and theoretically) prove the existence of a threshold in SPL (≥ 155 dB) at which the acoustic precipitation and coagulation efficiency increase rapidly, implying the importance of turbulence coagulation interactions at high intensity acoustic waves. In addition, a new empirical correlation was developed for the acoustic coagulation and precipitation efficiency with reasonable accuracy.

Comparison of Coal- and Oil-Fired Boilers through the Investigation of Filterable and Condensable PM2.5 Sample Analysis

“…Fundamentally, PM 2.5 emissions from stationary sources are classified as "filterable" and "condensable'' particulate matter. 10 Filterable fine particulate matter (FPM) is directly emitted from a source as a solid or liquid at stack, and captured on filter media. Condensable particulate matter (CPM) is known as a vapor phase material at stack conditions, but the material can condense and/or react upon cooling in the air to form a solid or liquid PM.…”

“…12−14 Numerous studies have confirmed that CPM contributes significantly to total PM 2.5 emissions from stationary sources. [10][11][12]15 Some studies have evaluated PM 2.5 emissions from industrial coal-fired boilers. 16,17 These studies illustrate characteristics of the emissions from coal-fired boilers, but very few have been carried out to examine emission of oil-fired boilers, 18,19 and to compare the dissimilarities of PM 2.5 emissions and the emission characteristics from coal-and oil-fired boilers.…”

“…Characterization of PM 2.5 from emission sources provides reliable data for identifying their contributions to ambient air and for designing corresponding control measures to follow government rules. Fundamentally, PM 2.5 emissions from stationary sources are classified as “filterable” and “condensable’’ particulate matter . Filterable fine particulate matter (FPM) is directly emitted from a source as a solid or liquid at stack, and captured on filter media.…”

Insights into agglomeration and separation of fly-ash particles in a sound wave field

“…Studies have shown that the agglomeration efficiency and collision efficiency of particles increases with an increase of SPL, 27,48,49 because the velocity of the gas medium correspondingly increases rapidly, which leads to an increase in the relative motion speed between the particles. However, when particles collide and form aggregates under the action of a high-intensity sound wave eld, the aggregates are easily separated if the SPL is too high.…”

Investigation of the Performance of Filtration-charged Particles in a Reversed Electric Field

“…11 illustrates an experiment in which the pressure drop of charged particles in a reversed electric field was 10% lower than that of filtration-uncharged particles and 5% higher than that of filtration-charged particles. The pressure drop declined when electrostatic materials were added to fibrous filters because charged particles tend to form a notably porous dust cake on the surface of the filter bag (Amiri et al, 2016). The negative polarity electric field of the collection stage rejected the negatively charged particles; thus, the pressure drop of charged particles in that reversed electric field was higher than that of filtration-charged particles.…”