The Behavior And The Pilot-Scale Technology On Recovering The Protein From Whey Wastewater Using Inclined Foam Column

For comprehensive knowledge of enhancing foam drainage using the inclined square foam channel (IFC), the effect of the tilt angle was investigated experimentally and theoretically with the diluted whey wastewater as the model system. Though building the inclined foam drainage model, the theoretical analysis presents that the velocity for the drained liquid reflux increased with increasing the tilt angle from0°to45°and then decreased. The net liquid flux in the IFC decreased to its minimum at45°and then increased. Thus the IFC of the tilt angle45°had the greatest ability to enhance foam drainage. The experimental results consisted well with the theoretical analysis. The IFC of the tilt angle45°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 of10.2was achieved using the IFC of45°, which was1.93times of that obtained using the vertical column.Gas distributor is an essential component of the IFC and its pore diameter directly affects the bubble size. Studying on the effects of pore diameter of the gas distributor on the foam fractionation, the results present that the decrease in the pore diameter resulted in smaller bubble size and larger bubble number, so the amount of adsorbed proteins at bubble surfaces increased. However, the bubble size in the foam was smaller and the liquid flux out of the column was larger. This increased the resistance for foam drainage. Therefore, for the protein solution of a low concentration, foam drainage is more critical and thus large pore diameter of a gas distributor contributes to high enrichment. For the high-concentration protein solution, small pore diameter of the gas distributor will improve recovery percentage if a high enrichment ratio is available.It is difficult to avoid the protein denaturation in the foam fractionation process. Studying on the effects of foam fractionation on the functional properties of the soy protein, the results present that the soy protein had poor thermal stability, and the higher the tempreture, the longer the heating time, the larger the protein denaturation in the whey wastewater. Moreover, the main reason of the protein loss in the process was atmospheric oxidation, and the secondary was microbial fermentation. Therefore, NaHSO3was added in the process in order to anti-oxidation corrosion. The dosage of additive NaHSO3was0.01% (W/V) which was referred to the effect of the ionic strength on the enrichment ratio of soy protein.The scale-up of the inclined square foam column, the design of the experimental technology and the optimization of operation conditions were conducted to debug the pilot experiments. A set of suitable operating conditions was loading liquid mass150kg, NaHSO30.01%(W/V), liquid tempreture48℃, foam tempreture55℃, gas flow rate1.0-1.2m3/h, liquid reflux of the foamate2kg/h and operating time6-8h.Therefore, studying on the behavior and the pilot-scale technology on recovering the protein from whey wastewater using inclined foam column, we can lay the theoretical and experimental foundation for extracting the soy protein by foam fractionation.