Dynamic hydrogen-intensified methanation of synthetic by-product gases from steelworks

Abstract Steelworks' by-product gases contain significant amounts of carbonaceous species, which can serve as carbon source for Power-to-Gas processes. The COx components from the by-product gases are converted into methane together with renewable hydrogen in a hydrogen-intensified synthesis reaction. Dynamic operation modes of the methanation are discussed to supersede large gas buffer capacities. This paper presents results from a two-stage methanation concept operated with by-product gases from steel industries. The first reactor is designed as heat pipe cooled structured fixed-bed reactor. Both the influence of the volume flow rate and the stoichiometric ratio are examined for different steady-state operating points as well as for dynamic operation modes with repetitive alteration of those two parameters. The two-stage methanation concept provides a consistent product gas quality over a wide syngas power range at slightly over-stoichiometric conditions for both steady-state and dynamic operating conditions. Full methane yield is achieved. The design of the heat pipe cooled structured reactor allows for step changes in syngas power up to 1.6 kW. Catalyst deactivation by coking took place in the first reactor stage during the performed experiments. This happened probably due to unfavourable operating conditions in the carbon formation regime while methanizing CO-rich gases.