Modeling dissolved air flotation: Fid-Bau Portal

Modeling dissolved air flotation

Liers, Sven / Baeyens, Jan / Mochtar, Indranata

Previously the flotation process was mainly characterized on an empirical basis. A model for dissolved air flotation (DAF) is presented that quantitatively describes the correlations and parameters used in both the contact and separation zones. This model includes two parameters, the bubble‐floc attachment efficiency (α_pb) and the air‐to‐solid volume ratio in the agglomerates(β). The sensitivity of the model for assumptions on physico‐chemical and operational parameters and on the two parameters α_pb and β is thereafter investigated. Experimental flotation efficiencies in a coaxial DAF column under varying operational conditions were in excess of 90% at surface loadings of 15 m/h and in excess of 95% at 10 m/h. The flotation model, combining bubble‐filter and separation efficiencies, was thereafter used to predict the efficiencies, and the model parameters α_pb and β were determined by a best fit‐approach between model and experiment. The model is not too sensitive to values of these parameters. The defined α_pb and β values correspond with previous literature data although the concept of the coaxial DAF improves the efficiencies compared with traditional rectangular DAF‐columns. The model can be used to calculate the efficiency for various possible operating conditions using either parameter values selected within the range of this paper or parameter values determined by fitting a limited number of small‐scale experiments.