On the Design of a Scaled-Up Pulsed Methane Pyrolysis Reactor for Clean Hydrogen Production

Abstract In a global hydrogen market rapidly growing to satisfy the requests driven by a Net Zero economy, new solutions for clean and cheap hydrogen production are needed. Ekona has developed a pulsed methane pyrolysis (PMP) hydrogen production system based on a constant volume, combustion-driven process. The PMP reactor is non-catalytic and low-cost and mitigates carbon fouling typical of other methane pyrolysis reactor platforms as proved by the 200 kg of hydrogen/day pilot. A scale-up procedure is on-going to meet the needs of actual applications typically orders of magnitude larger than this initial plant size. The enclosed paper describes the computational fluid dynamics (CFD) numerical modeling work performed to enlarge the current reactor and combustors, leveraging the lessons learned, up to commercial sizes. Since the process cycle is quite long and complex, the CFD study was broken into three different sections dedicated respectively to: 1) Combustor Mixing, Filling and Purging, 2) Simulated Hot Products Injection into the Reactor, 3) Reactor Filling and Venting and Interaction with concurrent Combustor Activities. Despite sharing a similar numerical method based on transient multi-species CFD simulations with moving meshes exploiting the overset mesh approach to model the valve movement, each section focused on different parts of the cycle (in time) and reactor (in space). Several geometry variants are tested and ranked in their performance for providing uniform methane/oxygen mixing, obtaining nearly one-dimensional plug flow filling in the combustor, generating adequate mixing between injected combustion products and feedstock in the reactor to uniformly raise pressure and temperature up to pre-pyrolysis conditions, and generating minimal flow anomalies in the reactor to permit smooth feedstock filling and venting due to the interaction with the combustor flow and nozzle tip.