Proof of concept and modelling of a gas-fluidized bed reactor

Methane as the main component of natural gas is conventionally burned for energy or converted to hydrogen with a side product of CO2. In thermocatalytic decomposition of methane (TCD) two valuable products are formed: carbon nano fibers (CNF), and hydrogen. CNF is a very valuable product with different applications in industry. Therefore, TCD is economically and environmentally promising technology. However, because of catalyst deactivation, solid formation on the catalyst particles, TCD is a very complex process and there are still technical challenges to optimally design and operate this process. In order to overcome these challenges, more knowledge should be gained via experiments and models.

In this project we built a special setup and perform about 200 hundred TCD experiments in the fluidized bed reactor. The effects of operating conditions on the lifetime of the catalyst, conversion and yield of the process were evaluated and the kinetic model of reaction and deactivation were quantified and derived.

A Computational Fluid Dynamic- Discrete Element Method- Multi-Grain Model (CFD-DEM-MGM) was developed to capture these multi-scale phenomena and model TCD in a fluidized bed reactor. The model includes of heat and mass and momentum transfer in the fluid phase, Interactions particles with fluid and each other, and heat and mass transfer and reaction inside each catalyst particle, together with mass and size change. This model is used to compare a batch and continuous fluidized bed reactor and can be used to design better reactors for TCD.