ISBN 9783843943956

978-3-8439-4395-6, Reihe Energietechnik

Sebastian Fendt
Experimental Investigation of a Combined Biomass-to-Gas / Power-to-Gas Concept for the Production of Synthetic Natural Gas (SNG)

258 Seiten, Dissertation Technische Universität München (2019), Softcover, A5

Zusammenfassung / Abstract

This thesis contributes to the research and development efforts aiming at the thermochemical production of Synthetic Natural Gas (SNG) from lignocellulosic biomass. In order to enhance the carbon yield in the SNG, the Biomass-to-Gas (BtG) process is coupled to an electrolysis unit, integrating renewable hydrogen in a Power-to-Gas (PtG) approach. The combined BtG/PtG concept represents a chemical long-term storage technology connecting the sectors power, heat, and mobility, via the existing natural gas grid.

The proposed concept favors a decentralized approach necessary for the sustainable use of biomass, which requires a robust plant design and a limited plant complexity. The central point of this work is the construction and commissioning of a pilot-scale test rig, as well as the respective experimental investigations of the combined BtG/PtG process with a focus on the most critical process steps. The experiments aim to derive correlations and long-term effects, which can be used for the design and optimization of BtG/PtG concepts.

The investigated allothermal gasifier proves to meet original design criteria, with realistic syngas compositions and a cold gas efficiency of up to 78.6 %. The catalytic tar reforming shows high conversion levels for tars but also degradation phenomena, highlighting the importance of long-term testing. The Ni-based methanation catalysts show a reasonable activity, especially at higher temperatures, while low-temperature performance is limited. A simple polytropic two-zone reactor design is applied and shows the expected performance with a distinct hot spot at the gas inlet and an effective equilibrium temperature of around 350 – 370°C. Methanation can be enhanced by H2 addition up to an amount, at which subsequent CO2 separation might not be necessary anymore.

The experimental findings of this work provide the basis for a continuing process optimization and concept development in the future.