## 2 Design of the Swirling Curtain Dust Collection Device  
Figure 1 displays the illustrative diagram of the swirling curtain dust remover proposed in the study. The device is supported by four landing legs and mainly composed of a dust collector box, a spray device, a bidirectional swirling-dedusting-dewatering device and a dust slurry collector. As detailed in Figure 1, the body of dust collector box is composed of an upper chamber and a lower one. The upper box is composed of an air inlet, a dust collecting chamber and a collecting port. The lower box is a cleaning room, and the side edge of the clean room is provided with an air outlet. The spray device is installed in the dust collecting room. The atomizing device consists of several ultrasonic atomizers and pressure spray according to the air volume of the dust collector. The dirty air enters the dust catcher from the intake port. The fine gaseous water mist produced by the ultrasonic atomizer captures and condenses the dust in the dust catcher, so that the particle size and weight of the dust increase, so it settles down. In order to increase the effect of dust removal and fog removal, fine particles of water mist produced by the pressure sprayer on the bottom part of the upper box further capture dust particles and water mist particles. Figure 2 shows the image of the swirling curtain dust collector. The dust slurry collector is arranged at the lower part of the cyclone, and the settled slurry is discharged through the drainage hole. The two-way cyclone dewatering device is set in the cyclone. Under the action of centrifugal force, the droplets entering the cyclone are swiftly thrown to the cylinder wall to form a water film. The water film further adheres to the dust on the cylinder wall and discharges the dust collector with water. The operating principle of the proposed dust collector was listed as below:  
1. Firstly, dust airflow enters the ultrasonic atomizer and is fully mixed with the water spray from the ultrasonic atomizer. Because of the small particle size, large contact area and high evaporation rate of the water mist emitted by the ultrasonic atomizer, the water vapor in the dust-bearing area can be saturated quickly. Additionally the wetting condition of fine dust can be effectively improved. In order to increase the effect of dust removal and fog removal, the fine mist produced by the pressure sprayer on the upper part of the upper box further catches dust particles and water mist particles. This greatly strengthens the centrifugal separation and capture ability of dust. 2. Then, the droplets and dust particles enter the cyclone through the collecting port along with the airflow. Swirling blades of the same shape but in opposite directions are installed at the intake and exhaust outlets of the swirl drum respectively. The swirling blades form a double swirl form, which keeps the airflow rotating until it is discharged. Besides, it forms an axial non-return  
Figure 1: Illustrative diagram of the SCDC. Figure 2: Image of the SCDC. swirl structure to prevent the dust from bouncing back. This greatly improves the effect of dust separation by centrifugation. The dust adhering to the wall of the cylinder is discharged from the dust collector along with the water through the slurry collector. The swirling curtain dust collector is a kind of comprehensive wet dust collector. When dust airflow enters the dust collector, the movement characteristics of dust with different particle sizes in airflow space are different. The water curtain produced by ultrasonic nebulizer and pressure sprayer is combined with three mechanisms of collision, interception and diffusion to gather dust and form a mixture of dust and water. Then, the dust-water mixture is thrown into the wall of the cyclone and removed under the action of the centrifugal force of the cyclone. The water curtain is produced by an ultrasonic atomizer and pressure sprayer.