Supercritical Water Oxidation of Isopropanol under Conditions of both Oxidant Deficit and Excess

Treatment of a wide variety of aqueous organic wastes by means of supercritical water oxidation (SCWO), [T > 374 degrees C and P > 220 bar], is well known to be very effective. However, in some cases (e.g. biomass slurries, obsolete chemical weapons, etc.) the addition of an auxiliary fuel such as methanol (MetOH), ethanol (EtOH) or isopropanol (IPA) is beneficial to overcome certain SCWO limitations and to accomplish an autothermal operation. The main objective of this work is to implement a set of laboratory tests, at different temperatures (T), oxidant coefficient values (n = /oxygen(supplied)/oxygen(stoichiometric)) and residence times (t), needed to know the behavior of IPA in the SCWO process and its suitability as a make-up fuel in comparison to EtOH and MetOH. All assays were carried out in a continuous flow reactor system, at a constant pressure of 250 bar and temperatures ranged from 400 degrees C to 500 degrees C. The amount of oxygen supplied ranged from total defect (pyrolysis) to oxygen excess. The concentration of make-up fuel was settled around 10 g/l at the reactor entrance. Results obtained from pyrolysis experiments show that this reaction can not be neglected, since up to 11.68 % of the total chemical oxygen demand (TCOD) removal was attained at 500 degrees C. Operating with oxygen excess (n = 2), TCOD removal is clearly enhanced by the temperature from 38 % at 400 degrees C to > 99 % at 500 degrees C. Results in terms of total organic carbon (TOC) removal are in accordance with TCOD removal. Considering T = 460 degrees C and t approximate to 12 - 40 s, results of this work show that the highest level of TCOD removal is attained for SCWO of EtOH, followed by MetOH and then, by IPA.