Technology Development and Techno-Economic Analysis of Hydrogen Production by Thermal Decomposition of Methane

The transition to the hydrogen economy has been proposed as a sustainable solution for the simultaneous depletion of fossil fuels and the increase in global energy demand since the 1970s. However, the current fossil fuel-based hydrogen production causes significant CO2 emissions. On the other hand, extensive hydrogen production by water electrolysis powered by renewable electricity requires a remarkable increase in the renewable electricity generation capacity. Therefore, alternative solutions are needed in order to promote the hydrogen economy, develop hydrogen infrastructure, and smoothen the transition to the wide-scale renewable-based hydrogen production in the future.

In this work, thermal decomposition of methane (TDM) was studied as a transition period solution towards the hydrogen economy. In TDM, methane is converted to hydrogen and solid carbon thereby avoiding the direct CO2 emissions. A laboratory-scale test reactor was designed and constructed in this work in order to experimentally study the TDM reaction. The experimental results were combined with mathematical modeling to find a suitable TDM reaction mechanism for reactor design studies. A global reaction mechanism with reaction parameters optimized in this study was found applicable for this purpose.

The TDM product carbon utilization possibilities were evaluated by conducting a market survey. According to the experimental TDM studies in the literature, the product carbon from non-catalytic TDM at temperatures above 1450 K is carbon black. Carbon black is mainly utilized in rubber industry and its market value vary from 500 EUR per tonne to 2,000 EUR per tonne depending on the quality. As a part of the technology development, a design path was outlined to assist the selection of the reaction, reactor, and process parameters for a TDM application. The path was followed in this work when potential industrial-scale technology concepts for hydrogen production by TDM were designed. The economic feasibility of these processes was evaluated and comparison was conducted with two other hydrogen production technologies, i.e., steam methane reforming (SMR) and water electrolysis.

According to the economic analysis, a break-even value for the TDM product carbon was found as 310 EUR per tonne of carbon in the current market situation and 280 EUR per tonne of carbon in a potential market situation in 2030 above which the hydrogen production by TDM would be economically feasible in comparison with SMR. The CO2 emissions from the hydrogen production by TDM were considerably lower than in SMR. Electrolysis could provide an economical option for the production of CO2 -free hydrogen when it is powered by inexpensive renewable electricity, but its availability is expected to remain limited in the near future. By contrast, the feedstock availability through the existing natural gas network provides a possibility for demand-driven hydrogen production by TDM. Thus, the most suitable application for TDM was identified in this work as small or medium industrial scale on-site hydrogen production, which minimizes hydrogen transportation costs. The TDM technology implementation could be further advanced by creating a sufficiently large market for the product carbon and tightening the CO2 emission regulation.