## 1 Introduction  
With the rapid development of economy and society in China, the enormous amount of energy consumption caused severe air pollution problems [1; 2; 3; 4; 5]. The flue gas emitted by coal-fired power plants contains a variety of fine particles, which are major air pollutants in some big cities. Fine particulate matter with a particle size less than 2.5 \(\upmu\)m is denoted as PM\({}_{2.5}\). Large quantities of toxic substances can be easily transported because of their small sizes and large specific surface areas. These can, therefore, enter the lungs and endanger human health [6; 7; 8; 9]. Traditional dust removers, such as cyclone dust collectors and electrostatic precipitators (ESPs), although with high efficiency in decreasing the mass concentration of particles, exhibit low efficiency in removing PM\({}_{1}\) (85% or less) [10; 11; 12]. Wet electrostatic dust removal devices cover a large area, and they increase equipment operating cost. Therefore, it is particularly important to study the pre-treatment technology of fine particles [13]. There are several pre-treatment technologies for fine particles including acoustic agglomeration [14; 15], electrical agglomeration [16], chemical agglomeration [17], and nucleation condensation growth [18]. In the acoustic agglomeration field, high-intensity acoustic waves act on aerosols, causing fine particles to collide and agglomerate through different vibrations and interactions. As particles become larger, their subsequent elimination with dust removal equipment is improved. The effect of acoustic agglomeration is related to acoustic frequency, sound pressure level (SPL), particle size distribution,action time, and other factors [17; 19; 20]. The vibration of sound waves induces the vibration of the medium, which in turn causes the vibration of particles through the viscous force. Sound waves with different frequencies have different carrying capacities for various sizes of particles; such capacity is related to what is called the entrainment coefficient (up). The vibration of particles in the medium lags behind that of the medium itself because of inertia. This means that a larger particle leads to a greater inertia and a more considerable hysteresis. The change in particle size, therefore, has a significant impact on the vibration of particles in the acoustic field. [PERSON] et al. [21] compared the effects of high-frequency 20-kHz sound waves and low-frequency 1400-Hz sound waves on coal-fired particles. They found that the low-frequency 1400-Hz sound wave was more suitable for coal-fired particles, whereas the high-frequency 20-kHz acoustic wave was more effective for nanometer-sized particles than micron-sized particles. Electrical agglomeration is a pre-treatment technology whereby the chargeability of particles is increased, and the agglomeration effect among particles is enhanced. In this experimental study, a high-voltage narrow pulsed corona discharge is used as an external field. During the corona discharge with a pulse width of several hundred nanoseconds, the electrons have a considerably larger charge capacity than ions. The charge process is mainly reflected in the collision of high-energy free electrons and particles that can significantly improve the charge of particles. The time outside the pulsed corona discharge period is considerably longer than the discharge period. After the discharge period, the impact charge of positive ions on particles through diffusion motion transpires. During the entire agglomeration process, therefore, particles with different electrical charges collide and agglomerate. In previous research, [PERSON] et al. [22] found that the pulsed combined direct current field device has a fine particle removal efficiency that is as high as 90%. For different particle sources, the use of appropriate acoustic and pulse parameters to maximize the agglomeration effect in the coupling field is an important research topic. In previous studies, different particle sources were used.