Methanation of CO2 on Ni/Al2O3 in a Structured Fixed-Bed Reactor—A Scale-Up Study

Due to the ongoing change of energy supply, the availability of a reliable high-capacity storage technology becomes increasingly important. While conventional large-scale facilities are either limited in capacity respective supply time or their extension potential is little (e.g., pumped storage power stations), decentralized units could contribute to energy transition. The concepts of PtX (power-to-X) storage technologies and in particular PtG (power-to-gas) aim at fixation of electric power in chemical compounds. CO2 hydrogenation (methanation) is the foundation of the PtG idea as H2 (via electrolysis) and CO2 are easily accessible. Methane produced in this way, often called substitute natural gas (SNG), is a promising solution since it can be stored in the existing gas grid, tanks or underground cavern storages. Methanation is characterized by a strong exothermic heat of reaction which has to be handled safely. This work aims at getting rid of extreme temperature hot-spots in a tube reactor by configuring the catalyst bed structure. Proof of concept studies began with a small tube reactor (V = 12.5 cm3) with a commercial 18 wt % Ni/Al2O3 catalyst. Later, a double-jacket tube reactor was built (V = 452 cm3), reaching a production rate of 50 L/h SNG. The proposed approach not only improves the heat management and process safety, but also increases the specific productivity and stability of the catalyst remarkably

Elicitation of Membership Functions: How far can theory take us

A taxonomy of interpretations for fuzzy membership functions is given. Depending on each interpretation, the elicitation method and the theory to apply seems to be different. When different interpretations are cast into a measurementtheoretic framework, the difference becomes clearer. However, this raises questions about the validity of the overall measurement-theoretic framework. It is argued that the measurement-theoretic framework imposes an objective account of meaning for fuzzy set theory and implications of this on the practical elicitation of membership functions are commented on.