Environment-friendly, safe, and reliable energy supplies are essential for sustainable development and a high quality of life. Despite the social, political, environmental, and economic challenges involved in energy provision, the need for low-emission and dependable energy sources is more critical than ever. In this context, hydrogen is emerging as a key player in the future energy landscape. With a high energy density of 142 MJ/kg, significantly higher than that of natural gas (52 MJ/kg) and crude oil (45 MJ/kg) - hydrogen shows great promise as a clean and efficient energy carrier. It can be utilized in various sectors, including transportation, electricity storage via fuel cells, and numerous industrial applications. Additionally, hydrogen production can be adapted to different scales - from large central plants and medium-scale semi central facilities to small, distributed units near the point of use, such as refueling stations or stationary power sites. This flexibility, combined with its environmental benefits, positions hydrogen as a vital component in achieving a sustainable and secure energy future. Nowadays, hydrogen production from water is becoming very popular, as water is abundant and hydrogen is its primary component, making it easily accessible on Earth. The use of microwaves as an energy source in experimental processes has also become increasingly popular due to their low energy consumption, enhanced safety, and ease of controlling experimental conditions. During microwave heating, the absorbent material interacts with microwave radiation, leading to a temperature increase based on the material's dielectric properties. When microwave radiation is applied to activated carbon, the temperature rises significantly, enabling the breakdown of water molecules into hydrogen and oxygen on the high-temperature surface.
In this study, fixed and fluidized bed quartz reactors containing activated carbon as the adsorbent is utilized to dissociate water into hydrogen and oxygen under mono-mode microwave conditions. Upon reaching a specific temperature, steam is introduced into the reactor, where it decomposes upon contact with the preheated particles. Additionally, nitrogen is injected into the reactor to transport steam into the reactor and then for sweeping the generated hydrogen and other product gases out of the reactor. Hydrogen levels within the system are monitored using a gas analyzer. The study investigates the effects of different microwave modes E (electric; where H field in nearly zero) and H (magnetic; where H field is nearly zero), temperature variations, water flow rates, and different type of bed on hydrogen production and yield. In addition, a two-level full factorial central composite design of experiment (DOE) method was used to identify the key parameters influencing the process. The DOE method is also used to find optimized conditions for hydrogen yield under different conditions by changing 4 different factors including water flow rate (4-level), temperature (4-level), microwave mode (2-level), and bed type (2-level).
