Corrosion rate determination of vessel walls agitated by double impeller and gas sparging

Abstract

AbstractRecently, multiple impeller gas sparged vessels have found wide application in many industries, such as food, pharmaceuticals, and biofuels. In this study, the rate of diffusion-controlled corrosion of the wall of nitrogen gas sparged-double impeller agitated vessel was studied by the dissolution of copper wall in acidified dichromate solution technique. The variables studied were the impeller rotation speed, the superficial gas velocity, and the clearance between the two impellers. The results were reported in terms of dimensionless number depicting the process conditions, Re, Sc, and the impeller clearance. For the agitated vessel, the corrosion rate correlation was ${\rm{CR}} = 1.6\; \times \;{10^{\; - \;16}}{\rm{R}}{{\rm{e}}_{{\rm{Ag}}{\rm{.}}}}^{0.668}{\left( {{{{C_2}} \over H}} \right)^{0.183}}{\rm{S}}{{\rm{c}}^{0.33}}.$ For the condition: 2800<ReAg.<19,600, 0.19<C2/H<0.58 and Sc=960, with an average deviation of ±2.9%. For the agitated sparged vessel, the data were correlated by ${\rm{CR}} = 2.5\; \times \;{10^{\; - \;15}}{\rm{R}}{{\rm{e}}_{{\rm{Ag}}{\rm{.}}}}^{0.134}{\rm{Re}}_{{\rm{Sp}}{\rm{.}}}^{{\rm{0}}{\rm{.381}}}{\rm{S}}{{\rm{c}}^{0.33}}.$ For the condition: 2800<ReAg.<19,600, 370<ReSp.<1855 and Sc=960, with an average deviation of ±6.7%. These results show that, under these conditions, the rate of corrosion of agitated vessels is controlled by the rate of agitation and the clearance between the impellers. However, when gas sparging is introduced, the rate of corrosion is much more influenced by the gas flow rate, whereas the effect of the clearance between the impellers nearly disappears.