On the development of computational tools for the modelling and simulation of SCWO process intensified by hydrothermal flames

Abstract

Supercritical Water Oxidation (SCWO) has the potential to be considered a clean energy generation process, as the process effluent is a high temperature, high pressure stream with a high enthalpy content that can be converted to heat and shaft work. Even when the state of the art is still far from being ready to build big power station based on this process, as SCWO is a process largely studied as waste elimination technology, the knowledge acquired in that field will allow the rapid development of this technology as a clean energy generation process. Furthermore, when the process is carried out under hydrothermal flame conditions it is intensified by producing higher temperature effluent in extremely compact reactor. In this work, existing proposal of potential heat recovery and power generation using SCWO, both in flame and flameless regime, are reviewed, and the needs on research are remarked. There are two main points in which the technology must be improved to develop energy generation by SCWO. In first place reactors and reaction systems able to process feeds consisting of suspension with high inorganic contents without diluting the effluent reducing its temperature must be developed. On the other hand, the systems of energy recovery must be improved, especially the expanders, in order to recover the pressure work as well as the thermal energy. CFD modeling tools can help in both aspects. But for developing good models a good comprehension of thermal and transport properties of mixtures at supercritical state, as well as oxidation kinetics under that condition are essential data that must be further investigated in order to find energetically efficient processes.

Review on an Advanced Combustion Technology: Supercritical Hydrothermal Combustion

“…Therefore, Wall 3 was adopted in subsequent TWRs [33,74]. On the basis of the previous TWR scheme, the innovative WCHB with excellent cooling performance and durability for hydrothermal combustion has been proposed ( Figure 4b) [31,75,76]. In addition, its simplicity made it easy to instruct the design of the reactor and the study of hydrothermal flame by comparison between experimental results and numerical simulation results.…”

Supercritical water processes: Future prospects

“…We have calculated that it is possible to operate with air as the oxidant, or to use enriched air through the direct expansion of the effluent in a turbine, and thus produce net energy [51][52][53]. Even when the option of direct expansion of the effluent is, by far, the most energetically efficient, it will be not applicable in the short term.…”

“…Thus, technical issues concerning the expansion of two-phase streams prevent the effective implementation of direct expansion in the short term. Furthermore, the detailed design of a dedicated, effective turbine would be costly and would take some time to implement [51][52][53][54].…”

“…Flame simulation contours of new cooled wall reactor with two outlets: (a) IPA mass fraction, (b) reaction rate[52].The SCWO processes with hydrothermal flames have a number of advantages over the flameless processes. Some of these advantages could overcome the traditional challenges that make a successful and profitable commercialization of SCWO technology difficult.…”

“…Some of these advantages could overcome the traditional challenges that make a successful and profitable commercialization of SCWO technology difficult. The advantages include the following[52]:…”