The natural gas flow fields and particles separation characteristics were numerically calculated with the RNG k - epsilon turbulence model and Discrete Particle Method (DPM) in the supersonic swirling separator. An experimental system was set up for testing the separation efficiency of three new designed separators with wet air. The numerical results showed that the new annular nozzle not only expanded the natural gas to supersonic velocity with resulting in low temperature (-72 degrees C), but also strengthened the swirling flow with the centrifugal field of 640 000g (g is the acceleration of gravity), both of which created good conditions for natural gas dehydration. Under the strong swirling flow field, most particles collided with the walls or entered into the liquid-collection space directly, while only few particles escaped together with the gas flow. The separation efficiency reached over 95%, when the length of the cyclone separation section was about 10 times of the diameter of the wall at throat. The experimental results indicated that the water can be efficiently removed from the wet air. The numerical results were in good agreements with the experimental findings, which demonstrated that the Discrete Particle Method (DPM) was accurate and stable enough to evaluate the dehydration characteristics of the supersonic swirling separator. (C) 2011 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.