Experimental Study of the Hydrothermal Flame Formation and Behavior in a Vessel Reactor for Supercritical Water Oxidation

摘要

The supercritical water oxidation (SCWO) is a promising technology for the destruction of wastes, but its commercialization has been delayed by the problems of corrosion and salt deposition associated to this technology and as well for its high energetic consumes. Using reactors working with a hydrothermal flame as a heat source contributes to overcome many of the challenges presented by this technology. Injection of the reagents over a hydrothermal flame can avoid the reagents preheating as the feed can be injected into the reactor at low temperatures, avoiding plugging and corrosion problems in a preheating system. Also the kinetics is much faster allowing complete destructions of the pollutants in residence times much lower than 1s. Next to this the high temperatures associated to the hydrothermal flames contribute to a better energy recovery of the reaction heat for electricity production. Since Franck and co-workers [1] discovered for the first time the existence of hydrothermal flames, several research groups has developed reactors working with a hydrothermal flame as a heat source [2, 3]. The High Pressure Process Group (HPPG) of the University of Valladolid (UVa) has developed several vessel reactors since 1993. It was proved that formation of hydrothermal flames was not possible in tubular reactors at temperatures lower than 350°C [4]. Thus, vessel reactors provide a space where the cold reagents are preheated to the autoignition temperature and brought into contact with the radical formed facilitating flame formation. In this work the ignition of hydrothermal flames is experimentally studied in a cooled wall vessel reactor. The influence of feed flow, injection temperature and geometry of the injection system has been evaluated by studying the temperature inside the reactor and the TOC removal.