Catalysis Today, Vol.369, 12-18, 2021
Circumventing carbon formation in CO2 reforming of methane by an adiabatic post conversion reactor
Feasible process conditions for reforming of gas mixtures of CH4 and CO2 into CO-rich synthesis gas are dictated by the risk of carbon formation. To overcome this risk, a minimum steam requirement exists for the process as determined by thermodynamic considerations. This work describes an approach for using a well-known nickelbased catalyst system to enable production of CO-rich synthesis gas at low steam-to-hydrocarbon-carbon (S/C) ratios. The concept utilizes a two-reactor approach where traditional steam reforming is done initially, followed by CO2 addition to the hot synthesis gas and subsequent conversion in an adiabatic reactor, a so-called Adiabatic POst Converter (APOC). This allows for operating at overall S/C ratios of below 1.5; which is much lower than what is possible in a conventional fired reformer. The central element of the APOC is that the temperature is kept higher than 700-800 C to circumvent the carbon limits. The process elements were demonstrated by a combination of thermodynamic calculations, process calculations, and laboratory experiments. The concept allows for design of significantly more compact reformers (up to 30 % reduced size), which in turn also reduces firing and thereby CO2 emissions. The concept can also be used in existing plants where the capacity can be boosted by adding an APOC.