Supercritical water oxidation: Fundamentals and reactor modeling

Supercritical water oxidation (SCWO) is a technology that takes advantage of the special solvation properties of the water above its critical point (374?C, 22.1 MPa), to achieve a complete destruction of organic wastes. The oxidation of the organics dissolved in supercritical water (SCW) can be carried out in an homogeneous phase due to the complete miscibility of oxygen with SCW. If the temperature is high enough (above 650?C) a complete destruction of a large variety of organics can be achieved with residence times lower than one minute. Although the energy consumption of the SCWO is very high, with an appropriate heat integration system, the process can be energetically self-sufficient or even produce an excess of energy. The two main challenges of the SCWO are corrosion problems and salt deposition. These problems can be overcome by the use of special construction materials and adequate reactor designs. Due to the high cost of the construction and operation of these reactors, the development of simulations is of great interest. This work gives a brief description of the process and its present challenges, focusing on the calculation of the physical properties of the water and its mixtures, and on the description of the kinetics from an engineering point of view, to finish with a short general description of the state of art in SCWO reactor modeling.