(596a) Design Study for Hydrogen Production through Fluidized Bed Heated Steam Methane Reforming (SMR) Combined with Chemical-Looping Combustion (CLC)

Chemical-looping combustion (CLC) of gaseous fuels provides concentrated CO₂ while avoiding the energy penalty of gas-gas separation. The fuel is oxidized in direct contact with an oxygen carrier material in the fuel reactor while the circulating oxygen carrier is re-oxidized with air in the air reactor. Steam methane reforming (SMR) requires relevant heat transfer rates to heat the tubular reformer reactors. If such reformer tubes are designed to be placed in a hot fluidized bed for heat supply, the heat for reforming can be supplied from CLC of additional methane and the off-gas from the pressure swing adsorption (PSA) unit isolating the H₂ product, ideally allowing for 100% CO₂ capture while achieving similar or even higher energy efficiency than common SMR.

The process according to Figure 1 has been modelled in the steady state simulation environment IPSEpro with a customized model library for high temperature gas-solid processes. The necessary gas and solids flow rates are determined and transferred to a bulk design geometry of the fluidized bed system. The fuel conversion performance of the SMR reactor and of the CLC system are set based on the results of previous detailed studies on certain parts of the overall process.

It turns out that relatively high solid circulation rates are needed to keep the temperature differences between the air reactor and reformer heat exchanger reasonably small. A design solution is developed to achieve sufficient solids exchange and still keep the turbulences around the heated reformer tubes reasonable. The geometry is inspired by industrial fluidized bed heat exchanger practice. Pressure balance calculations give some initial confidence about the fluidized bed system design.

In conclusion, despite the high energy-efficiency potential of the CLC-SMR combination, practical implementation of the fluidized bed system comes with challenges. A rational approach towards a possible design has been presented and requires fluid dynamic verification in a cold flow model as possible a next step.