Alternative Index for Interpretation of RTD Curves

Abstract

An alternative approach for the interpretation of the residence time distribution (RTD) curves is proposed. The method has semiempirical basis, supported upon a gross fit of the tracer curve area by two triangles in order to obtain a single parameter (φ index) that indicates whether the system tends to a completely mixed or to a plug flow hydraulic behavior. In order to verify its applicability, 28 experiments were carried out in a laboratory tank (138 L). In these experiments, the influence of aeration, packing, and number of baffles on the tank hydraulic behavior was assessed using the index as well as conventional models. The general results obtained in the laboratory tank experiments showed that mixed tanks tend to have a larger dead volume fraction (DVF) than plug-flow tanks and that packed tanks tend to have a smaller DVF than nonpacked tanks. This index provides a reliable, quick, and simple method for the interpretation of the RTD curves when hydraulic behavior trends or tank modifications for hydraulic improvements are evaluated.