# Experimental and Numerical Investigation of Spray Scrubber Dust Collection Efficiency
## 1 Introduction
[PERSON] [14] performed emission measurements on a container vessel retrofitted with a wet scrubber, running on heavy fuel oil (HFO) during a journey from Tacoma to Anchorage. The scrubber was installed on a full-scale container ship. The primary pollutants examined were SO\({}_{2}\) and PM2.5 and emissions were measured before and after the scrubber. In this case, SO\({}_{2}\) removal exceeded 95%, while particulate matter (PM2.5) reduction was limited to about 10%, likely due to the formation of small sulfuric acid particles in the scrubber fluid. [PERSON] [15] analyzed gaseous and particulate emissions using Fourier Transform Infrared Spectroscopy (FTIR), condensation particle counters (CPC), and a soot particle mass spectrometer (SP-AMS) during ship operation. Testing was conducted on two medium-speed marine engines on a modern diesel-electric cruise ship. The primary contaminants were sulfur oxides (SO\({}_{\mathrm{x}}\)), nitrogen oxides (NO\({}_{\mathrm{x}}\)), and particulate matter. Real-time chemical composition analysis was performed for fresh and non-volatile aerosols. The hybrid scrubber effectively reduced sulfur dioxide emissions, but its efficiency varied for other pollutants, such as particulate matter. [PERSON] [16] analyzed the environmental impact of animal farms through key indicators like climate change, acidification, eutrophication, particulate matter formation, and others. The study gathered real-time emission data from field trials conducted on animal farms and used scaling methods to simulate the impact across whole farm systems. During this study, both wet and dry scrubbers were analyzed. Wet scrubber was installed in Spain and dry scrubber was tested in Italy. The study primarily focused on ammonia (NH\({}_{3}\)) and particulate matter (PM10, PM2.5), which are significant pollutants in livestock farming due to animal waste. The wet scrubber used a citric acid solution to neutralize ammonia, converting it into ammonium salts. The dry scrubber relied on mechanical filtration to capture dust particles. The ammonia removal efficiency reached 79% in the Spanish farm and 59% in the Italian farm. [PERSON] [17] studied the impact of demister geometrical parameters on its performance of wire demister. He evaluated the efficiency of a demister with a thickness of 100 mm and wire diameters ranging from 0.15 mm to 0.5 mm across a pressure range of 20 bar to 140 bar and for droplet diameters of 5 \(\upmu\)m, 10 \(\upmu\)m, 20 \(\upmu\)m, 30 \(\upmu\)m, 50 \(\upmu\)m, and 100 \(\upmu\)m.  
[PERSON] [18] developed a new construction of rotary demister. The demister consisted of a helicoidal element made of a metal sheet wound into a spiral and was designed to rotate at high speed within a cyclone body. Larger droplets were separated in the cyclone housing, while smaller droplets were carried by the gas into the rotating helicoidal path. The dry gas exited the system through a central channel in the spiral element, while smaller droplets were driven toward the walls by centrifugal force. These studies collectively highlight the ongoing advancements in spray scrubber technology, particularly in enhancing their efficiency for a wide range of industrial applications. However, in the analyzed publications, the effect of using demister on particle collection efficiency was not investigated. The optimization of scrubber inert geometry and determining the impact of additional elements on separation efficiency is a complex task, which must be considered on a case-by-case basis. The purpose of this paper is to determine the dependency between collection efficiency and water mass flow rate and the impact of scrubber inert geometry. Two demisters were designed by the authors, after which they were manufactured with the use of 3D printing process, and finally, they were placed inside scrubber. The authors investigated experimentally the scrubber of 1 m height and 0.2 m diameter, where the working fluid is air and the contaminant introduced to the system is magnesium-oxide powder.