Abstract
This study aims to reduce greenhouse gas emissions to the atmosphere and effectively utilize wasted resources by converting methane, the main component of biogas, into hydrogen. Therefore, a reactor was developed to decompose methane into carbon and hydrogen using solar thermal sources instead of traditional energy sources, such as coal and petroleum. The optical distributions were analyzed using TracePro, a Monte Carlo ray-tracing-based program. In addition, Fluent, a computational fluid dynamics program, was used for the heat and mass transfer, and chemical reaction. The cylindrical indirect heating reactor rotates at a constant speed to prevent damage by the heat source concentrated at the solar furnace. The inside of the reactor was filled with a porous catalyst for methane decomposition, and the outside was surrounded by insulation to reduce heat loss. The performance of the reactor, according to the cavity model, was calculated when solar heat was concentrated on the reactor surface and methane was supplied into the reactor in an environment with a solar irradiance of 700 W/m2, wind speed of 1 m/s, and outdoor temperature of 25 °C. As a result, temperature, methane mass fraction distribution, and heat loss amounts for the two cavities were obtained, and it was found that the effect on the conversion rate was largely dependent on a temperature over 1000 °C in the reactor. Moreover, the heat loss of the full-cavity model decreased by 12.5% and the methane conversion rate increased by 33.5%, compared to the semi-cavity model. In conclusion, the high-temperature environment of the reactor has a significant effect on the increase in conversion rate, with an additional effect of reducing heat loss.
Highlights
As the problems of global warming, caused by the use of fossil fuels, have increased, it has become necessary to expand the use of renewable energy to reduce greenhouse gas emissions
The optical distribution, heat and transfer, and chemical reaction are numerically calculated according to the cavity model, for the development of a methane decomposition solar reactor using an indirect catalyst heating method
The cavity model is divided into a full cavity and a semi-cavity, and the heat loss and methane conversion are compared for the two models, under the same heat source and ambient conditions
Summary
As the problems of global warming, caused by the use of fossil fuels, have increased, it has become necessary to expand the use of renewable energy to reduce greenhouse gas emissions. Among these renewable energies, hydrogen is attracting attention as an eco-friendly energy source that does not generate pollutants during combustion. Hydrogen is generally produced through methane reforming, water electrolysis, and thermal decomposition, among various other processes. When fossil fuels are used to supply heat or electricity, carbon dioxide is emitted. The thermal decomposition of methane requires high-temperature heat, as shown in Equation (1).
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