A new device-the rotational particle separator (RPS)-is compared to the cyclone for the removal of ultrafine particles, such as cryogenically condensed contaminant droplets from natural gas. The comparison focusses on identifying for each configuration the smallest size of particle which has a 50% chance of being removed from the gas stream. Whereas a cyclone can only separate 1 mu m droplets at very low-throughputs on the order of 1 MMscfd, at the same energy consumption and device volume, the rotational particle separator removes droplets of that size at throughputs of 300 MMscfd. The advantage of the rotational particle separator, therefore, lies in its compact separation potential for full-scale industrial gas well throughputs. (c) 2007 American Institute of Chemical Engineers.