مرکز منطقه ای اطلاع رساني علوم و فناوري - Analysis of Biphasic Cracking of Methane for Hydrogen Production Using Solar Energy

Abstract :

Hydrogen can be produced by many processes, by a series of chemical reactions many of which have been known for centuries. However, most of these reactions raise severe environmental and safety problems, while availability of raw materials is a critical problem. One of the partial solutions is solar hydrogen. It appears that cracking of carbon rich materials is the right solution for this energy. In this context comes this numerical simulation of the methane cracking phenomenon. In the simulation, we have taken in to account the existence of carbon as a homogeneous powder. The mixture is considered to be biphasic formed by a gaseousphase with methane, hydrogen gases and carbon black powder solid phase. This powder is formed by solid particles with same diameter (d=50nm). The cracking phenomenon of the methane into hydrogen and carbon black takes place in a cylindrical cavity of 16 cm in diameter and 40 cm in length under the heat of concentrated solar radiation without any catalyst. A commercial calculation code ANSYS FLUENT is used to simulate the cracking phenomena. Two cases were studied: the first one applying a maximum solar radiation of 16MW/m2 on the side wall of the reactor and the second one a maximum solar radiation of 5 MW/m2. The CH4 flow rate used at the inlet of the reactor is 0.4 L/min and the low Reynolds K - ε turbulence model was applied. A time step of 0.04s has been used.The cracking rate exceeds 90% with a maximum solar radiation of 16MW/m2 and this rate does not reach 85% with a maximum solar radiation of 5MW/m2.The dimensions of the cavity are important and it allows going from the experimental scale to the industrial scale. Working without any catalyst facilitates the separation of the elements after cracking.