Radioactive tracer measurements, using impulse injections of Ar-41, powdered oxide of Mn-56 and real catalyst particles doped with an oxide of Mn56, conducted at the Advance Fuels Development Unit (AFDU) slurry bubble column (BC) reactor during dimethyl ether (DME) synthesis (reactor pressure of 5.27 MPa, reactor temperature of T = 250 degrees C, inlet superficial gas velocity of 17.1 cm/s, and a catalyst loading of 36wt%) at LaPorte, Texas, are interpreted. The differences in the responses obtained by the catalyst and fine powdered Mn2O3 tracer injections are minimal indicating the validity of the pseudo-homogeneous assumption for the liquid plus solid (catalyst) phase mixtures. The gas-liquid recirculation model [Gupta et al., 2001a. Comparison of single- and two-bubble class gas-liquid recirculation models-application to pilot-plant radioactive tracer studies during methanol synthesis. Chemical Engineering Science 56(3), 1117-1125. 2001b. Hydrodynamics of chum turbulent bubble columns: gas-liquid recirculation and mechanistic modeling. Catalysis Today 64(3-4), 253-269], based on a constant bubble size, describing gas-liquid mass transfer superimposed on turbulent mixing of the gas and liquid phases, is used to simulate the gas, liquid and catalyst tracer responses acquired at the AFDU. The model is able to predict the characteristic features of the experimental responses observed for gas, slurry powder and catalyst tracers at different reactor elevations. The fact, that the same model was previously shown capable of predicting both gas and liquid radioactive tracer responses during methanol and Fischer-Tropsch (FT) synthesis, indicates that this model offers a relatively simple tool for assessing mixing and transport in bubble (BCs) for a variety of gas conversion processes and provides a phenomenologically based framework for BC reactor modeling. (c) 2006 Elsevier Ltd. All rights reserved.