# Experimental and Numerical Investigation of Spray Scrubber Dust Collection Efficiency
## 3 Results  
After analyzing the flow patterns from preliminary numerical analysis, the experimental analysis was performed and the test stand was launched. It was decided to determine operational characteristics of the scrubber for different water flow rates generated in the nozzle. At first, measurements were performed for the scrubber without demisters, then a system with one and two demisters was tested. In addition, tests were performed for different air velocities at the scrubber inlet. Each measurement required the use of a procedure consisting of:  
* Starting the compressors and checking the discharge pressure;
* Preparing, weighing, and installing the filter above the scrubber;
* Weighing and introducing the appropriate amount of dust into the fluidizer;
* Adjusting the air speed at the scrubber inlet, where measurements were taken for velocities of 2 m/s and 4 m/s;
* Adjusting the water flow in the nozzle;  
Figure 9: Contours of the velocity inside the spray scrubber. * Opening the valve above the fluidizer;
* Measurement (60 s) with recording the measured parameters with a frequency of 1 Hz;
* Closing the valves with MgO particles, air, and water;
* Drying the filter if necessary;
* Weighing the dry filter and the dust mass that remained in the fluidizer;
* Determining the separation efficiency;
* Repeating the procedure for other configurations of demisters and operating parameters. After completing the measurement procedure, the results were analyzed. The pressures in the system and the air and water flow rates were measured and recorded in real time to ensure the repeatability of the obtained results. Examples of measurement results are presented in Table 3.  
Table 3 shows a measurement example for one of the cases. Based on the results, it can be concluded that the measured parameters were stable during the measurement process, which is visible from their standard deviations in relation to the average value. Dust mass measurements were not performed in real time, but only before and after each measurement session. Estimating measurement errors in such a case is a rather complicated process because:  
* Dust may settle on the scrubber walls;
* Some dust may remain in the inlet pipe;
* Dust may fall off when removing the air filter and placing it on the weighing scale. Therefore, it was assumed that measurements would be started after waiting a certain time for the dust flow in the scrubber to stabilize. After this time, further measurements showed good repeatability. Each measurement was repeated and the extreme values of the determined separation efficiency were rejected. After the test stand was launched, experimental tests were carried out for several configurations of the spray scrubber. First, the operation of the scrubber was analyzed without any demister installed above the water nozzle. Characteristics were made for different mass flow rates of the spray generated by the nozzle. It was found in the system without the demister that some of the water droplets were entrained by the flow and penetrated to the upper part of the scrubber and were captured on the air filter. For higher values of water flows, the wetting of the filter was observed after the measurements and in order to measure its mass, drying was necessary. The air flow rate was regulated on the compressor using a pressure reduction valve and was measured on the flow meter. The obtained flow value was converted in real time to the average velocity on the inlet cross-section of the scrubber. First, the valve was adjusted to achieve an inlet velocity of 2 m/s, and then it was increased to 4 m/s. In the second stage of the tests, a single demister was mounted at a height h\({}_{2}\) above the water nozzle, as shown in Figure 1, and the measurement procedure was repeated. Finally, two demisters were mounted and measurements were taken again. The separation characteristics for both inlet velocities are shown in Figures 10 and 11. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline  & **Air Flow** & \