Abstract
The present report summarizes the theoretical modelling and experimental investigation results of the study on the direct thermal methane cracking. This work is a part of the LIMTECH-Project (Liquid Metal Technologies) funded of Helmholtz Alliance and was carried out from 2012 to 2017. The Project-part B5 “CO2-free production of hydrogen” focused on experimental testing and particularly on modelling the novel methane cracking method based on liquid metal technology. The new method uses a bubble column reactor, filled with liquid metal, where both the chemical reaction of methane decomposition and the separation of gas fraction from solid carbon occur. Such reactor system was designed and built in the liquid metal laboratory (KALLA) at KIT. The influences of liquid metal temperature distribution in reactor and feed gas flow rate on methane conversion ratio were investigated experimentally at the temperature range from 930°C to 1175 °C and methane flow rate at the reactor inlet from 50 to 200 mLn/min. In parallel with experimental investigations, a thermochemical model, giving insight in the influence of the above mentioned parameters has been developed at KIT and a CFD model was developed at LUH to get an overview about the bubble dynamics in the reaction system. The influence of different bubble sizes and shapes, multi-inlet coalescence effects as well as the potential of electromagnetic stirring have been investigated.
Highlights
The carbon dioxide emission (CO2) from human activities influences the earth’s ecosystem significantly
The methane cracking reaction occurs in a vertical bubble column reactor filled with liquid metal
The main objective of the presented work was to better understand the influence of some major influencing parameters on the direct thermal methane cracking within a liquid metal bubble column reactor
Summary
The carbon dioxide emission (CO2) from human activities influences the earth’s ecosystem significantly. The methane cracking reaction occurs in a vertical bubble column reactor filled with liquid metal. Thereby, methane is heated up to liquid metal temperature level and split into gaseous hydrogen and solid carbon. As the bubble radius is kept constant, volume expansion due to the pressure drop and the chemical reaction along the liquid metal reactor length is not included in the model. Given by mass conservation, the sum of all components present in the chemical reaction leave the reactor In this process, the carbon stays inside of reactor, which reduces the total mass and the total molar flow of the product gas. With the new GC molar flow rate, the calculation of the methane conversion, using GC mole fraction data and Equations (14) - (18), result in
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