Particles produced from a gas-saturated solution process (PGSS) in a capillary nozzle are assumed to be in steady, 1-D, inviscid, and two-phase equilibrium homogenous flow. Fluid dynamic equations including mass, momentum and energy conservations are established to describe the mixture's pressure, temperature, velocity and density change along the nozzle. The aerosol dynamic equation for crystallization of the natural lipid hydrogenated palm oil (HPO) in the pseudo-single phase is proposed considering that homogenous nucleation, condensation, and coagulation occur simultaneously along the nozzle. Using the Peng-Robinson equation of state for the fluid properties and phase equilibrium, the coupled model equations are numerically solved to describe the PGSS process for the CO2/HPO system. Axial profiles for the concentration of CO2 in HPO, total pressure, temperature, velocities and densities of the two phases, particle size, and particle size distribution inside the nozzle have been calculated. The model also shows that HPO particles produced by rapid expansion of supercritical solutions (RESS) are about 3.5% (in mass) of the total solid production at 18 MPa and 359 K and, therefore, can be neglected. (C) 2004 Elsevier B.V. All rights reserved.