Figure 2 Frequency distribution of microbubble size under nine different conditions
The range analysis of the results shows that the optimal level of each factor is 0.55 MPa of the pressure, 5% of the gas-liquid ratio and 10 cm of the length of the release pipe. The order of the range values of the three factors for the test indexes was length of the release pipe (43.17) > gas-liquid ratio (21.29) > pressure (14.82). The length of the release pipe shows obvious influence on the microbubbles with particle size less than 50 μm in the floating system. The P values of pressure, gas-liquid ratio and length of the release pipe were 0.35, 0.18 and 0.05, respectively. As can be seen from the F-test results, when the confidence level is 95%, only the length of the release pipe is significant to the test index, and there is no significant difference in the influence of pressure (0.35, 0.45, 0.55MPa) and gas-liquid ratio (5%, 6%, 8%) on the test index.