Effect of temperature, wall shear stress, and NaOH concentration on cleaning effectiveness

The objective of this research was to evaluate the effect of various operational parameters and their interaction on cleaning rate of NaOH. The parameters include wall shear stress, temperatures, and NaOH concentrations of cleaning fluid. The higher cleaning effectiveness for proteinaceous deposits was achieved at higher wall shear stress. The wall shear stress of 2.42 Pa removed over 90% of foulant after 10 min of operation, which was significantly higher than the removal of lower wall shear stress (0.84 and 0.39 Pa). Similarly, the cleaning rate increased with increase in temperature and concentration of cleaning solution. The use of cleaning solution (0.05% NaOH) at 65°C provided significantly higher cleaning rate than 25°C. A cleaning solution concentration of 0.5% NaOH provided significantly higher removal of foulant than 0% or 0.05% concentrations. However, analysis on the interaction between temperature and the wall shear stress suggested that the temperature above 45°C and wall shear stress above 0.65 Pa did not provide significant improvement in cleaning efficacy. When a cleaning solution temperature was maintained at 45°C, higher wall shear stress provided more rapid removal of the foulant when the cleaning agent concentration was 0.05% or 0.5%. In water rinse conducted without chemical agents, no much improvements in foulant removal were observed with increase in wall shear stress. The change of activation energy (E_a ) indicates that water rinse was sensitive to temperature change at higher wall shear stress. However, cleaning with cleaning agents was less sensitive to temperature variation compared to the water rinse. PRACTICAL APPLICATION: Considering the intense use of water and chemical compounds during cleaning operation, finding operating condition to ensure acceptable cleanness with minimized input is desired. Temperature, cleaning agent concentration, and wall shear stress are the major components to influence the cleaning efficacy. The result of the study demonstrates the potential for optimization of in-place cleaning by appropriate adjustments of the CIP operating parameters.