Energy recovery from effluents of supercritical water oxidation reactors

Abstract

10Supercritical Water Oxidation (SCWO) reactors can process waste effluents achieving high 11 conversions, but the required extreme pressure and temperature operational conditions entail 12 high-energy operational expenditure. SCWO has the potential to be considered a clean energy 13 generation process, as the process effluent is a high temperature, high pressure stream with a high 14 enthalpy content that can be converted to heat and shaft work. This ensures the self-sustained 15 reaction and can generate excess shaft power to drive both the high-pressure pump and the air 16 compressor. On the contrary, an efficient heat and power recovery from SCWO reactors outlet 17 streams using conventional procedures presents several problems. First, Rankine cycles impose 18 indirect heat transfer to the working fluid and are unable to recover the pressure energy and 19 second, direct expansion of the effluents entails costly development of specific, efficient 20 expansion equipment. 21In this work, we investigate the options for energy recovery of SCWO reactors coupled with 22 commercial gas turbines (GT). SCWO outlet streams are mainly composed of water, nitrogen and 23 carbon dioxide. These operating values nearly resemble the well-known and already-implemented 24 GT steam injection procedures. The temperature of the flue gases (approx. 500 ºC) and the direct 25 shaft work usage offers adequate energy integration possibilities for both feed preheating and 26 compression. The wide range of commercially available GT sizes enables process scaling. 27

Analysis of the Energy Flow in a Municipal Wastewater Treatment Plant Based on a Supercritical Water Oxidation Reactor Coupled to a Gas Turbine

“…As an alternative to these problematic energy recovery schemes, a theoretical proposal for the simultaneous heat and power recovery from clean SCWO outflows suggests that it can be directly injected into the hot gas path of a commercial gas turbine (GT) [29]. This GT injection operation is a field-proven technology that is widely used with the aim of reducing NOx emissions and augmenting power production by increased exhaust flue gases (FG) mass flowrate, commonly known as Steam Injected Gas Turbine (STIG).…”

Review on an Advanced Combustion Technology: Supercritical Hydrothermal Combustion

“…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. In order to explore the possibility of using the hydrothermal flame as the way of energy production, the structure and the whole operation system of the reactor were perfected ( Figure 4c) [37,77]. The first modification was its inlet and outlet.…”

Landfill leachate treatment by batch supercritical water oxidation

“…Although the required extreme pressure and temperature conditions could impose a high-energy expenditure, SCWO has the potential to be considered a clean energy process [12]. The heat released by the oxidation reaction could be converted to heat and shaft work, assuring a self-sustained reaction, as well as generate excess shaft power to drive both the high-pressure pump and the air compressor, as shown by García-Rodríguez [13]. Several studies have performed supercritical processes economic assessments through process simulation [14].…”