Investigating the Microwave Behaviour of Solid Carbon in Natural Gas Pyrolysis under Microwave Irradiation
Creators: Sama Manzoor
Publisher: name: University of Alberta Library
Year: 2024

<p>The rising levels of carbon dioxide emissions stemming from the combustion of fossil fuels necessitate immediate attention to implement sustainable energy solutions. Hydrogen as a fuel, holds significant potential for establishing CO2-neutral systems, and the utilization of microwave pyrolysis of methane is emerging as an innovative and promising approach in this regard. In contrast to conventional hydrogen production methods that generate CO2 by products, the microwave-driven methane pyrolysis process exclusively yields solid carbon and hydrogen gas as its byproducts. To enhance our understanding of this technique and its scalability, it is essential to explore the microwave characteristics of the carbon used and generated during this process. This thesis provides fundamental insights into the microwave heating behaviour of solid carbon and how it translates to cracking of methane into hydrogen. We investigated the microwave properties of two carbon samples (seed carbon; SC and product carbon; PC) from microwave-driven pyrolysis of methane. We employed cavity perturbation technique from room temperature to 1250°C across frequencies of 397, 912, 1429, 1948, and 2467 MHz. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) analysis were conducted for further insight. SC exhibited an initial permittivity decline up to 200°C due to moisture release, confirmed by TGA/DSC showing a 5% mass loss from 100-155°C. Subsequently, permittivity peaked and then decreased due to high conductivity. PC displayed fluctuating permittivities but maintained consistent values. PC, generated at elevated temperatures, showed no moisture loss in TGA/DSC. These findings indicate that the microwaves can penetrate and heat both the samples uniformly across their entire volume, resulting in efficient heating. SC had higher permittivity, making it more responsive to microwaves, but its potential for thermal runaway in microwave-driven pyrolysis applications is a concern. XRD analysis revealed that both SC and PC had amorphous carbon structures, with PC showing some signs of graphitization. Both carbons can serve as effective microwave heat carriers in methane pyrolysis, potentially eliminating the need for costly catalysts and enabling a self-sufficient process.While microwave pyrolysis of methane has proven to be effective in producing a substantial quantity of hydrogen, the reactor&#39;s fluidization process is of paramount importance. Therefore, the second part of the thesis further reviewed the diverse comminution behaviours observed in fluidized reactors concerning carbon materials. This study is essential for understanding the actual combustion rate, thermal efficiency, and particle size distribution of carbonaceous solids during fluidized bed combustion. Factors such as porosity, particle size, volatile content, and bed temperature heavily influence particle fragmentation.The outcomes of this thesis will play a significant role in improving the efficiency and efficacy of microwave pyrolysis of methane and its associated applications, thereby advancing the path towards a more sustainable and economically viable energy solution.</p>