MIXING AND ALUMINUM PRECIPITATION

Aluminum hydrolysis in mixed liquid reactors is a problem with multipl e kinetic and mixing time scales Since some of these times scales over lap, and since aluminum hydrolysis has multiple pathways (some of whic h are slowly reversed), we have modeled aluminum precipitation as a co upled mixing and chemistry problem. For the base neutralization of dil ute aluminum chloride in a standard stirred reactor with Rushton impel ler, mixing submodels are combined with simplified aluminum chemistry models to predict the effect of mixing on steady-state pH at various f ormation or neutralization ratios. Our simulations and experiments cle arly show that mixing speed influences the shape of the pH titration c urve, which suggests that the conversion of aluminum into amorphous an d polymeric species is mixing-sensitive. The experimental and simulate d results show less sensitivity to position of base injection in the r eactor.