Hydrothermal oxidation is an alternative process to conventional methods for wastewater treatment. The purpose of this study was to valid the PROSIM software's for the scale-up of industrial unit in order to minimize the amount of energy supplied to the system and to optimize the energy generated by the oxidation of organic wastes. A new reactor concept with oxygen multi-injection was used to carry out the oxidation of methanol as model compound. Different experiments have been carried out in quasi-adiabatic conditions, with a feed temperature of 430 degrees C at the reactor inlet, leading to temperatures up to 700 degrees C at the reactor outlet. The temperature profiles along the reactor have been registered and compared to the simulation of the process performed with PROSIM. (C) 2006 Elsevier B.V All rights reserved.