Enhancing foam drainage using inclined foam channels of different angles for recovering the protein from whey wastewater

For comprehensive knowledge of enhancing foam drainage using the inclined foam channel (IFC), the effect of the tilt angle was investigated experimentally and theoretically with the diluted whey wastewater as the model system. The IFC allowed the interstitial liquid to release quickly to its wall and then returned the liquid phase along it. The theoretical analysis presents that the velocity for the drained liquid reflux increased with increasing the tilt angle from 0° to 45° and then decreased. The net liquid flux in the IFC decreased to its minimum at 45° and then increased. Thus the IFC of the tilt angle 45° had the greatest ability to enhance foam drainage. The experimental results consisted well with the theoretical analysis. The IFC of the tilt angle 45° was adopted to improve the protein enrichment ratio and its performances were evaluated under various conditions. Under the suitable conditions, a best protein enrichment ratio of 10.2 was achieved using the IFC of 45°, which was 1.93 times of that obtained using the vertical column.