Experimental Analysis of Non-Catalytic Methane Pyrolysis in a Tubular Reactor
Student: David Aguerrebere Jr
Year: 2023
Supervisors: Guðrún Arnbjörg Sævarsdóttir, Jason Olfert, Ehsan Abbasi Atibeh
Abstract:
One leading strategy for developing net-zero carbon emission technologies is to avoid burning fossil fuels by using alternative renewable fuels or using them as source material to produce hydrogen as a non-carbon-based fuel. This strategy mitigates global climate change by preventing the emission of new carbon in the form of carbon dioxide.
In this work, the decomposition of methane for hydrogen production under atmospheric and low partial pressures is investigated. The experiments are conducted in a continuous-flow reactor design based on a tube furnace with an inner diameter of 28mm and a heated section of 650mm. The effect of temperature, residence time, and dilution on hydrogen production, methane conversion, and the production of other hydrocarbons, such as ethane, ethylene, acetylene, and benzene is explored using a methane stream or diluted methane in nitrogen at flow rates between 0.1 to 5 standard L/min. The temperature is measured using an R-type thermocouple at the exit of the heated section.
The resulting exhaust gas composition is measured using a gas chromatograph calibrated for the targeted species in the exhaust, and the exhaust volumetric flow rate is measured using a DryCal flow calibration system, allowing for the measurement of the mass of each species at the exhaust. The results show that minimal methane conversion occurred at 600◦C, but significant hydrogen production started to occur at 800◦C. In these experiments, the largest values of methane conversion and hydrogen production were found when high temperatures were combined with large residence times. The largest amount of hydrogen was yielded when the composition of the feedgas was 100% methane, and in nearly all experiments, the methane conversion and hydrogen production were largest when the feed was 100% methane. The results also indicate that after a certain residence time, the reaction reaches equilibrium, which occurs between 0.1 and 0.01 SLPM in this setup.
This work enhances the fundamental understanding of methane pyrolysis and aims to develop proof-of-concept decomposition reactors in the future. The experimental work is completed in parallel with numerical modeling and provides the data to develop and validate pyrolysis models for analysis and design. Overall, this research provides insight into the potential for using methane as a source material for hydrogen production, which has important implications for the development of net-zero carbon emission technologies.