A mathematical model was developed and used in conjunction with actual product property measurements during a commercial polyolefin production plant product transition to determine if ideal powder plug-flow is achieved in the linear low-density polyethylene (LLDPE) commercial plant's purge column. Ideal powder plug-flow is desirable in the purge column, to minimize off-specification product during product transitions and to provide optimum residual hydrocarbon desorption from the product powder particles. A mathematical model that uses a theoretical series of continuous stirred tanks (CSTs) to characterize powder flow inside a vessel shows that the purge column is equivalent to over 70 CSTs in series, which renders optimum product transitions and excellent olefin removal. The calculated Peclet number is Pe = 140, which is indicative of very small axial dispersion of the powder as it moves within the purge column.