Experimental performance investigation of a 2 kW methanation reactor

Abstract

A 2 kW methanation reactor was designed, built and tested for the gas phase hydrogenation of CO₂ to CH₄. The reactor is a single-stage, fixed-bed reactor. A commercial catalyst with 0.5% wt Ru on an alumina support was applied and characterized using TEM imaging. A thermal model of the process was developed in order to effectively design the cooling system and estimate the temperature gradients within the reactor. The conversion efficiency was investigated experimentally using transmission infrared spectroscopy. The reactor temperature set point was varied from 140 °C to 400 °C, the space velocity ranged from 0.14 s⁻¹ to 0.55 s⁻¹ (corresponding to 0.40–1.55 ml g⁻¹ s⁻¹) and the pressure was set to 5 bar. A maximal conversion of 99% was measured at a temperature of 260 °C and a space velocity of 0.14 s⁻¹. A CO₂ conversion of 97% was reached at a target flow rate of 50 g h⁻¹ H₂ and a temperature set point of 280 °C. Such conversions are very high for a single-stage reactor and are partly due to the inhomogeneous temperature distribution within the catalyst bed, which allowed the balancing of the kinetic and thermodynamic effects. The reactor presented in this paper is installed as a part of the small-scale demonstrator of renewable energy to synthetic hydrocarbon conversion of EPFL Valais/Wallis.