(562p) Characteristics of Heat Transfer in Carbon Dioxide Methanation Process

In recent years, there has been great interest in developing carbon capture, utilization and storage (CCUS) technology to mitigate the carbon dioxide emissions and address global warming issue. In a similar vein, the development of the utilization technology for intermittent electrical energy from renewable energy sources, such as solar photovoltaic, wind, wave, geothermal, etc., is considered as a promising research area, and water electrolysis technology for hydrogen production using renewable energy sources is one of viable options. In terms of energy storage capacity and discharge time, the synthesis of hydrogen from water electrolysis and carbon dioxide from carbon capture and storage process into methane, i.e. methanation, is a more favorable process and is carried out by the Sabatier reaction. During the reaction, the carrier of chemical energy is converted from hydrogen with low energy density to methane with high energy density. The CO₂ methanation process can be carried out with high GHSV and steam can be produced with high temperatures using heat exchange system. In power-to-gas process, heat dissipation gradients inside reactors and temperature control are of major interest since the methanation reaction is a relatively high exothermic reaction (ΔH° = −165 kJ/mol) and a renewable electricity could not supplied constantly. Various reactor types have been developed and the fixed bed reactors are most used for the CO₂ methanation. However, the main disadvantages of fixed bed reactor is the hot spots and the poor flexibility with load changes due to fluctuation of renewable energy sources. A fluidized bed reactor is known as a good chemical reactor due to its excellent mass and heat transfer properties. Moreover, a fluidized bed reactor has advantages in easy temperature control and good contacting between reactants compared to the fixed bed reactor. The aim of this study is to investigate the reactor and heat exchange system suitable for the demonstration of the CO2 methanation process and discuss the design factors of the heat exchanger according to the selected reaction system.