(617de) Hotspot Mitigation in an Annular Microchannel Reactor (AMR) for Hydrogen and/or Syn Gas Production

Authors: 
Butcher, H., Texas A&M University
Wilhite, B., Texas A&M University
Bossard, P., Power and Energy Inc
The potential economic impact of a portable, modular and efficient technology for converting logistical fuels (e.g., natural gas, methanol or ammonia) into hydrogen on-site or in-the-field processing of natural gas to liquid fuels via syngas production is significant. Heat-exchanger microreactors provide novel process intensification routes through breakthrough heat transfer rates per reaction volume, enhancing the capacity and thermal efficiency of heat-transfer limited reactions including methane steam reforming or ammonia decomposition. In both applications, supplying heat from a separate combustion reaction (e.g., pairing methane steam reforming with methane combustion) promises autothermal operation for maximum portability.

This study focuses on a way to mitigate local hotspot formation when coupling methane steam reforming with catalytic methane combustion in a heat-exchanger microreactor. Previous studies have shown that the annular microchannel reactor (AMR), originally developed by Power + Energy, can be powered by catalytic combustion of methane achieving up to 67% overall thermal efficiency. However, hotspot formation was found to be an issue for catalyst stability. The addition of reforming catalyst to the inlet region of the AMR acts as a reaction heat sink providing hotspot control and adding further reforming capacity. Different catalyst thicknesses ranging from 30-60 microns were used and catalyst length ranged from 10-30 mm. The additional catalyst results in a temperature drop of over 100°C at the inner wall of the annulus, as well as lowering peak temperature in the reactor by over 70°C. Despite the temperature drop, the reactor performance is maintained.