Modeling and optimization of phenol hydrothermal oxidation in supercritical water Benmakhlouf Nadjiba, Outili Nawel * , Meniai Abdesslam Hassen Environmental Process Engineering Laboratory, Process Engineering Faculty, Constantine 3 University, Algeria article info Article history: Received 2 August 2016 Received in revised form 3 November 2016 Accepted 7 November 2016 Available online xxx Keywords: Supercritical water oxidation Wastewater treatment Energy recovery Process modeling Design of experiments abstract The hydrothermal oxidation is an efficient and clean way for wastewater treatment; it is also an energy self sufficient process under certain conditions, by the mean of the highly exothermic reaction of oxidation. In this present work, we studied the modeling of hydrothermal oxidation of phenol in polluted water using supercritical conditions. First we apply a simple mathematical model for tubular reactor, resulting from mass, momentum and energy balances, which is often difficult to solve in its general form. According to adequate simplifications, the profiles of temperature and concentration of chemical species are computed along the reactor. Finite differences numerical method was used to solve the obtained system of equations and a MathCAD program was developed for this purpose. The results are close to experimental works from the literature. To study the influence of some operating conditions on the efficiency of the treatment and the amount of heat generated by the reaction and which will be recovered to heat the inlet flows, we exploited the modeling results to perform a full factorial design of experi- ment (DOE). The results allow fixing the optimal conditions for the studied factors on the efficiency and energy recovery of the process treatment. © 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Introduction Hydrothermal oxidation in supercritical water (SCWO) is a technology of high interest to treat organic liquid wastes and is a promising technology to eliminate a wide range of wastewaters from a broad variety of industries [1]. Supercritical water oxidation is defined as an oxidation process which occurs in water above its critical point (Tc ¼ 374  C and Pc ¼ 22.1 MPa) [2]. At supercritical water oxidation conditions, organic spe- cies, oxygen, and water form a single homogenous phase. The presence of a single phase and high temperatures in supercritical water allows the oxidation to proceed rapidly by an elimination of potential interface mass transport limitation. Indeed, properties of supercritical water such as the com- plete miscibility in all proportions with oxygen, negligible surface tension, high diffusivity, low viscosity, and low solu- bility of inorganic salts, are very unique especially in disposal of toxic compounds [3]. The main advantage of these processes is that products are non toxic. Indeed, organic material (C, H, and O) is exclusively converted into carbon dioxide and water. In the same condi- tions the gasification which occurs for the conversion of the same type of effluent and, generally the same type of reactors used to produce, in addition, hydrogen and methane [4], hence * Corresponding author. E-mail address: out.nawel@gmail.com (O. Nawel). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2016) 1 e8 http://dx.doi.org/10.1016/j.ijhydene.2016.11.046 0360-3199/© 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Nadjiba B, et al., Modeling and optimization of phenol hydrothermal oxidation in supercritical water, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.11.046