# Experimental and Numerical Investigation of Spray Scrubber Dust Collection Efficiency
## 2 Materials and Methods  
A test stand was designed for the purpose of testing the separation efficiency of a spray scrubber. Below, we present the description of the individual elements of the test stand and the measurement methodology. The main element of the stand was a model of the spray scrubber made in the laboratory. The scrubber was constructed of transparent pipes with a diameter of 200 mm, made of polycarbonate, connectors, and a conical element. The scrubber scheme is shown in Figure 1.  
In the last section of this part, the description and results of the preliminary numerical studies are included. The calculation results show the velocity patterns inside spray scrubber, which leads to better understanding of the phenomena occurring inside the device. Most of the scrubber dimensions are presented in Table 1. The height and width of the rectangle inlet are, respectively, 60 mm and 40 mm. The diameter of the cleaned gas outlet is 60 mm and the diameter of condensate outlet is 30 mm. The scrubber has a central inlet perpendicular to the vertical axis (3) through which the contaminated gas enters the system, the condensate outlet is located at the bottom (1), and the cleaned gas leaves the system through the cleaned gas outlet (10). A water nozzle (6) is mounted in the scrubber, which generates droplets (5), which then collide with the contamination particles (4), and after the coalescence, they leave the system through the condensate outlet (1). At a distance h2 above the water nozzle, the first row of demisters (7) is mounted, which consists of flat blades inclined at an angle of 45\({}^{\circ}\). There is also a second row of demisters higher up, with both demisters manufactured from plastic using a 3D printer. The geometry of the demister is shown in Figure 2.  
Figure 1: Schematic presentation of a spray scrubber in the laboratory (1—condensate outlet, 2—droplet blocking element, 3—contaminated gas inlet, 4—contamination particles, 5—water drops, 6—water nozzle, 7—first demister row, 8—second demister row, 9—demister blade, 10—cleaned gas outlet). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**H** & **h1** & **h2** & **h3** & **h4** & **D** & \(\alpha\) \\ \hline
810 mm & 270 mm & 200 mm & 50 mm & 100 mm & 200 mm & 45\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The dimensions of the scrubber. The 3D model was used to make a 3D print. The demister designed by the authors consists of a body printed from plastic with prepared guides and polycarbonate blades. The blades are placed parallel to each other and are tilted at an angle of 45\({}^{\circ}\). The distance between adjacent blades is 15 mm. Two demisters were manufactured, and during the measurements, they were placed inside the scrubber. The presence of the additional demisters constitutes a unique aspect of the article. The scrubber was mounted on a test stand used to measure separation efficiency, the scheme of which is shown in Figure 3.  
The air flow is generated by the compressor, and its flow rate is measured in the flow meter (5), which was thermal mass flowmeter FCI ST75 of range 0 to 86 \(\mathrm{N}\mathrm{m}^{3}/\mathrm{h}\) with accuracy \(\pm\) 2%. Dust particles in the form of crushed magnesium oxide, previously mixed with air in the fluidized, are supplied to the air channel. The pressure of the air stream with dust particles is also measured by the manometer (7) with Wika S20 (WIKA Polska, Wlodawek, Poland) pressure transducer of range 0 to 6 bar with accuracy \(\pm\) 0.5%. Both air streams mix before entering the scrubber chamber. Then, the contaminated gas flows through the scrubber, where a water nozzle generates drops that collide with the dust particles. The purified gas fraction leaves the upper section of the scrubber and flows through the air filter (4). The filter is weighed before and after each measurement, which allows for measuring the mass of the dust fraction that could not be separated by scrubbing. It was selected due to its good availability and lack of toxic properties.