Theoretical study of the expansion of supercritical water in a capillary device at the output of a hydrothermal oxidation process

Frederic Marias (1) , Stéphanie Vielcazals (2, 1) , Pierre Cézac (1) , Jacques Mercadier (1) , François Cansell (2)

1 LATEP - Laboratoire de Génie Thermique Énergétique et Procédés (EA1932)
2 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

This paper deals with the expansion of supercritical water at the output of the reactor of a supercritical water oxidation process. Inside such reactors, a common value of the working pressure is approximately 25 MPa. The fluid exhausting the reactor mainly contains water and carbon dioxide and salts. The operating pressure needs to be dropped in order to separate the different constituent of the fluid and to send back to environment the clean effluents. The behaviour of the salts held within the supercritical water is very specific. Indeed, at high pressure, the salts are present at the solid state, but once some liquid water appears, a part of the salts is dissolved into this liquid. Thus, in order to be separated by classical gas/solid separation at moderate pressure, the process stream needs to be carefully expanded. This paper presents a mathematical model that has been build in order to design a capillary device for this expansion. The governing equations of the model are presented as well as the way it has been solved. Some computations around a nominal operating conditions point are performed. These computations have led us to the design of an experimental device.

Mots clés: Thermodynamic approach; Supercritical water oxidation; Modelling; Expansion; Salts

Domaines: Génie des procédés

Frederic Marias, Stéphanie Vielcazals, Pierre Cézac, Jacques Mercadier, François Cansell. Theoretical study of the expansion of supercritical water in a capillary device at the output of a hydrothermal oxidation process. Journal of Supercritical Fluids, 2007, 40 (2), pp.208-217. ⟨10.1016/j.supflu.2006.07.008⟩. ⟨hal-02383810⟩