Zero-cost partial decarbonization of natural gas via molten salt pyrolysis

Abstract

Partial decarbonization of natural gas has the potential to kickstart the hydrogen economy. Up to 20% hydrogen volume can be safely accommodated in existing natural gas networks, removing the problem of insufficient distribution and end-use infrastructure for pure hydrogen. The present work investigates a technological pathway for producing such partially decarbonized gas (PDG) at zero or negative cost: molten salt pyrolysis. When producing PDG with 20% H2 instead of pure hydrogen, the demands on the pyrolysis process become considerably lighter: The pyrolysis reactor can be operated at lower temperatures, alleviating challenges with salt evaporation and reactor corrosion, there is no need for a hydrogen purification step, and the smaller quantities of carbon produced from pyrolysis will not rapidly oversaturate high-value carbon markets. Techno-economic assessments showed that the pyrolysis pathway can produce PDG at a CO2 avoidance cost of only 11 €/ton compared to 135 €/ton for conventional autothermal reforming. When the reactor temperature is increased from 800 °C to 900 °C or additional natural gas preheating is done, the CO2 avoidance cost can fall to about −50 €/ton, making PDG production profitable even without climate policies. This promising economic performance combined with the alleviation of multiple technical and political barriers highlights the strong commercial potential of PDG production via molten salt pyrolysis.