Selective CO Methanation in H2-Rich Gas for Household Fuel Cell Applications

Panagiota Garbis,Andreas Jess

doi:10.3390/en13112844

Abstract

Polymer electrolyte membrane fuel cells (PEMFCs) are often used for household applications, utilizing hydrogen produced from natural gas from the gas grid. The hydrogen is thereby produced by steam reforming of natural gas followed by a water gas shift (WGS) unit. The H2-rich gas contains besides CO2 small amounts of CO, which deactivates the catalyst used in the PEMFCs. Preferential oxidation has so far been a reliable process to reduce this concentration but valuable H2 is also partly converted. Selective CO methanation considered as an attractive alternative. However, CO2 methanation consuming the valuable H2 has to be minimized. The modelling of selective CO methanation in a household fuel cell system is presented. The simulation was conducted for single and two-stage adiabatic fixed bed reactors (in the latter case with intermediate cooling), and the best operating conditions to achieve the required residual CO content (100 ppm) were calculated. This was done by varying the gas inlet temperature as well as the mass of the catalyst. The feed gas represented a reformate gas downstream of a typical WGS reaction unit (0.5%–1% CO, 10%–25% CO2, and 5%–20% H2O (rest H2)).

Highlights

IntroductionProton-exchange membrane fuel cells (PEMFCs), known as polymer electrolyte membrane fuel cells, cogenerate electricity and heat (heated water) from hydrogen or H2 -rich gases (and O2 /air)
Proton-exchange membrane fuel cells (PEMFCs), known as polymer electrolyte membrane fuel cells, cogenerate electricity and heat from hydrogen or H2 -rich gases.In order to generate the demanded amount of both heat and electricity, the PEMFCs are mostly combined with a traditional furnace
The H2 -rich gas produced by the steam reforming of natural gas followed by a water gas shift (WGS) unit still contains small amounts of CO

Summary

Introduction

Proton-exchange membrane fuel cells (PEMFCs), known as polymer electrolyte membrane fuel cells, cogenerate electricity and heat (heated water) from hydrogen or H2 -rich gases (and O2 /air). In order to generate the demanded amount of both heat and electricity, the PEMFCs are mostly combined with a traditional furnace. A connection to the electrical grid is available to cover the heat and electricity not produced by the fuel cell. Renewable energy sources like solar energy, biomass and environmental (geothermal) heat are already often used in power and heat generation systems. PEMFCs are already developed and commercially available for providing power and warm water to households but have to get more efficient and cost-effective in order to be enforced. The H2 -rich gas produced by the steam reforming of natural gas followed by a water gas shift (WGS) unit still contains small amounts of CO at the outlet due to limitation by thermodynamic constraints, typically in a concentration of approx

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Conclusion