Thermodynamic analysis of a Na-O-H thermochemical cycle coupled to a Gas Turbine Modular Helium Reactor (GT-MHR)

Abstract

Hydrogen (H2) is considered a clean fuel because its combustion releases heat, water and near-zero carbon emissions. This substance can be produced through many routes, including thermochemical cycles in which water molecules are splited into oxygen and hydrogen through specific chemical reactions supported by an appropriate heat source at specific temperature conditions. There are a wide variety of thermochemical cycles under development, many of them require temperatures higher than 1000°C while others, like the cycles U-Eu-Br, Mg-Cl and Cu-Cl can operate below 550°C. The reduction in the temperature levels of a thermochemical process allows the use of various energy options, facilitating H2 production. So, the main aim of the paper is to analyze hydrogen production according to the Na-O-H thermochemical process whose required heat is supplied by a Gas Turbine Modular Helium Reactor (GT-MHR), a nuclear power plant (NPP) with low cost and low carbon emissions. The Na-O-H is a fresh chemical process that can operates at temperatures close to 400°C. The system will be studied in the software Engineering Equation Solver (EES) according to the first and second laws of thermodynamics. The results indicate that such system can produce around 3.654 kg/s of H2 considering a mass flow rate of 500 kg/s of helium coolant at 850°C coming from GT-MHR.