The characteristics of a particle separator were studied with the concept of a uniflow cyclone, which would be used in the coal gasification process. A uniflow cyclone separator was designed and suggested in the current study. The objective is to investigate the characteristics of particle separation and pressure loss when a gas outlet tube length was varied in a uniflow cyclone separator with a wide range of particle sizes (D-p = 0.02-1000 mu m). Dry compressed air was used as a carrier gas and mixed with pulverized coal particles, The total mass flow rate in the separator inlet ((m) over dot(tot)) was fixed at 4.91 g/s and the mass flow rate of the injected coal particles ((m) over dot(P)) was 0.83 g/s in the surrounding temperature and atmospheric pressure (T-infinity = 20 degrees C and P-infinity = 1 bar). The length of the gas outlet tube (L-T) was varied from 125 mm to 210 mm. The efficiency of particle separation (epsilon(P)) was changed with the variation of the length of the gas outlet tube and maximized at 99.7% when L-T = 193 mm. When the gas outlet tube length was fixed at L-T = 175 mm, mean separation efficiency (epsilon(P,m)) increased with dust gas velocity, particle loading, and surrounding pressure in u(m) = 5.2-13.0 m/s, (m) over dot(P) = 0.82-4.10 g/s, and P-infinity = 3-5 bar. (C) 2014 Elsevier B.V. All rights reserved.