An Investigating on Parameters Affecting the Size and Size Distribution of the Precipitated Oxalate Particle Size in a Stirred Tank Reactor

In the thorium nuclear fuel cycle, precipitation of of thorium oxalate using oxalic acid is one of the main stages of processing. In this research, the aim of the study was to investigate the effects of sedimentation temperature, concentration and flow rate of the reactants, mixing rate, time and temperature of the digestion on the size of the thorium oxalate particles their distribution in a stirred tank reactor in a batch process. It was observed that with increasing concentrations and material fluxes, the particle size was reduced and the particle size distribution narrowed. By increasing the mixing rate, larger particles produced, but the uniformity of the particles increased first and then became smaller. With increasing the reaction and digestion temperature, the particle size was larger but the particles became even more uniform. Increasing the time of the digest resulted in the production of coarse particles but more uniform distribution. By analyzing the results, the optimum temperature was determined 10 °C, the optimal oxalic acid concentration and flow rate were 1.5 M and 10 ml / min respectively , and the optimum mixing speed was determined 150 rpm. The optimum time and temperature of the digestion were determined at 6 hr and 75 °C, respectively.