CFD Modeling of Reactor Concepts to Avoid Carbon Deposition in Pyrolysis Reactions

Abstract

Methane pyrolysis in an externally heated tubular reactor inevitably ends with clogging of the reactor. Thin molten metal wall films protect the walls from carbon depositions. A falling film reactor and a rotating film reactor are investigated by CFD simulation. The results show the considerable advantages of a rotating film reactor compared to the vertical film reactor. An alternative route for carbon production from methane is the implementation of an exothermic chlorination reaction. The tubular reactor concept involves the inflow of inert gas at the reactant inlet and through porous walls to ensure that the reaction takes place in the center, thus, largely reducing carbon deposits.

Theoretical Studies on a Rotating Film Reactor for Hydrogen Production from Methane

“…The simulations of the rotating film reactor were made using the computational fluid dynamics (CFD) software ANSYS R19.3. Equivalent to previous studies [21], a rotationally symmetrical model was constructed. For gas phase modeling, the k-e-RNG model with swirl-flow, production kato-launder and Menter-Lechner near-wall treatment was selected.…”

“…The equations of the boundary conditions can be taken in detail from previous work and are briefly summarized below. [21] Film surface velocity w max , inner radius r i and the constant C 1 are given by the following equations:…”

“…The equations of the boundary conditions can be taken in detail from previous work and are briefly summarized below. 21…”

“…In preliminary work, it was theoretically shown for the rotating film reactor that carbon particles with diameters larger than 50 nm hit the liquid film in 90 % of cases and do not enter the downstream piping system [21]. Based on the existing model, this work will investigate various design and operating parameters of the rotating tube reactor and their effect on methane conversion.…”

Analysis and Simplification of Kinetic Models for Methane Chlorination and Pyrolysis

“…Through specially designed flow arrangements, carbon deposits on the reactor wall may also be avoided, which could overcome one of the key challenges facing endothermic methane pyrolysis 2, 3. The heat released by the chlorination of a single methane molecule is much larger than that required for its pyrolysis.…”