A series of dilute phase pneumatic conveying experiments using two different types of plastic pellets has led to the determination and development of distinguishing flow characteristics. Separate experiments on polystyrene and polyolefin pellets captured pressure-drop fluctuations and values at two different measuring points-one at the lower horizontal section of the transporting pipe and another at the upper section and at two different solid-loading ratios for each material. Also, comparison and analysis of the pressure-drop fluctuations and values obtained from the experiments were carried out under the same solid-loading ratio and blower rotational speed for both materials. Basic pressure drop calculations were made to find pressure drop due to pure gas, and that due to the presence of solids using a solid friction factor. In addition, the power spectral density analysis, and the wavelet analysis were conducted for both materials to evaluate the flow characteristics. (c) 2008 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.