## 3 Results
### Experimental Results
#### 3.1.1 Dispersant Effectiveness
Additionally, the experiments were carried out at two different scales, namely a laboratory scale using the 1000-mL baffled flask (working volume of 360 mL), followed by a pilot-scale container of volume 41 L, and working volume of 30 L. Additionally, the container sizes, mixing blade size, and mixer rpm were used to calculate power and energy dissipation for each experimental case according to the equations presented in Section 2, which were then correlated on a single graph of energy dissipation versus power of mixing. For the entirety of this set of experiments, Petroclean was used as the dispersant. The first graph in this set of experiments presents (Figure 4) the DE levels as measured at five different mixing speeds (impeller mixing, 50 to 200 rpm) in the 1000 mL baffled flask. The results indicate relatively low but generally increasing DE levels, from less than 1% up to 14%, as the speeds rise from the 45 to 200 rpm. All results in this subset of experiments are for DE readings taken after 20 min of mixing. The next two graphs (Figures 5 and 6) present the time-based progression of DE levels at four different mixer speeds at the pilot scale using a 4-inch paddle impeller (Figure 5) and a 4.2-inch helical ribbon impeller (Figure 6). In these sub experiments, samples for determination of DE were collected at four time intervals, namely 0.5, 1.0, 1.5, and 2.0 h. In both cases, the DE rose abruptly at the higher speeds, and gradually at the lower speeds, except for the case of the lower speed of 45 rpm for the 4-inch paddle impeller, where the DE stayed at virtually zero for all time points measured. The final DE levels attained at the two highest speeds of 175 and 250 rpm were roughly all the same, at approximately 90%, regardless of mixer type. At the intermediate speeds of 100 rpm (paddle) or 85 rpm (helical), the DE levels increased but in a different manner, abruptly (paddle) versus gradually (helical). The results observed at the shorter time point of 0.5 h are directly in line with the previous results presented in Figures 2 and 3, as only low DE levels were achieved at mixing speeds of 100 rpm or lower, while quite high (90%) DE levels were achieved with mixing speeds above 150 rpm. Finally, Figure 7 presents a graph of the calculated average particle size, determined using Equation (1), as a function of mixing speed for all dispersant effectiveness data described above. The calculated particle sizes range from a low of approximately 200 \(\upmu\)m for the highest speed at the lab scale (200 rpm) to approximately 5000 \(\upmu\)m for the lowest speed (50 rpm) at the pilot scale with the helical impeller. An apparent disadvantage of the helical impeller indicated in Figure 7 is that its use results in a larger particle size as compared to the paddle impeller at the same rpm. Figure 4: Dispersant effectiveness in a 1000-mL baffled flask (lab scale) at five different impeller 2.5-inch diameter) speeds at the laboratory ambient temperature (approximately 25 \({}^{\circ}\)C). (Power number results for this test are included in Table S2). Figure 5: Dispersant effectiveness at the pilot scale (30 L) using a 4-inch paddle impeller at the laboratory ambient temperature (approximately 25 \({}^{\circ}\)C). (Power number results for this test are included in Table S3). Figure 6: Dispersant effectiveness at the pilot scale (30 L) using a 4.2-inch helical impeller at the laboratory ambient temperature (approximately 25 \({}^{\circ}\)C). (Power number results for this test are included in Table S4). Figure 7: Calculated dispersed oil particle sizes as a function of mixing speed. The final figure from this set of experiments depicts all of the DE results from Figures 4-6 above, plotted as individual points on a graph of energy dissipation \(\varepsilon\) versus power of mixing (Figure 8).