Design of a Multi-Tubular Catalytic Reactor Assisted by CFD Based on Free-Convection Heat-Management for Decentralised Synthetic Methane Production

Abstract

A simple reactor design for the conversion of CO2 methanation into synthetic methane based on free convection is an interesting option for small-scale, decentralised locations. In this work, we present a heat-management design of a multi-tubular reactor assisted by CFD (Ansys Fluent®) as an interesting tool for scaling-up laboratory reactor designs. The simulation results pointed out that the scale-up of an individual reactive channel (d = 1/4′, H = 300 mm) through a hexagonal-shaped distribution of 23 reactive channels separated by 40 mm allows to obtain a suitable decreasing temperature profile (T = 487–230 °C) for the reaction using natural convection cooling. The resulting heat-management configuration was composed of three zones: (i) preheating of the reactants up to 230 °C, followed by (ii) a free-convection zone (1 m/s air flow) in the first reactor section (0–25 mm) to limit overheating and, thus, catalyst deactivation, followed by (iii) an isolation zone in the main reactor section (25–300 mm) to guarantee a proper reactor temperature and favourable kinetics. The evaluation of the geometry, reactive channel separation, and a simple heat-management strategy by CFD indicated that the implementation of an intensive reactor cooling system could be omitted with natural air circulation.

A Minimum Entropy Production Approach to Optimization of Tubular Chemical Reactors with Nature-Inspired Design

“…Profiles of variables along the reactor tube can be obtained with various realistic geometries, in reference and optimal cases, using computational fluid dynamics (CFD). This method allows also a scaling-up of laboratory reactor designs to larger volumes [103]. A modification of the reactor design for conversion of CO 2 methanation into synthetic methane was, for instance, computed in a free convection multi-tubular reactor, in a CFD simulation of a single reactive channel (d = 1/40, H = 300 mm).…”

“…A modification of the reactor design for conversion of CO 2 methanation into synthetic methane was, for instance, computed in a free convection multi-tubular reactor, in a CFD simulation of a single reactive channel (d = 1/40, H = 300 mm). A hexagonal shaped distribution of 23 reactive channels separated by a distance of 40 mm was proposed [103].…”

Power-to-Methane to Integrate Renewable Generation in Urban Energy Districts

“…Among all the available technologies for CO 2 hydrogenation, the fixed-bed reactors offer the best compromise between compact design and synthetic gas quality [36]. Nevertheless, the temperature control alongside the longitudinal axis is crucial to attain high CO 2 conversion rates; moreover, the average temperature of reaction strongly influences the product gas composition which is crucial for matching the requirements for the subsequent injection of SNG into the gas grid [37].…”