Carbon Dioxide Methanation: Design of a Fully Integrated Plant

Abstract

A new, fully integrated process has been designed to evaluate the feasibility of the CO2 methanation reaction according to the Sabatier reaction. This approach has two environmental advantages: (i) the conversion of CO2 into a regenerated fuel or platform chemical and (ii) the chemical storage of H2 to allow its long-range transport using a well-established distribution network. Two kinetic models for the Sabatier reaction, reviewed from the literature, were used to design a multistage plug-flow reactor. The outflowing gas was then purified from unreacted CO2 and water, and proper recycles were foreseen to achieve an overall 100% conversion of CO2, given that, without water or methane withdrawal, at least four reactive stages are needed to get >75% conversion. Either adiabatic or cooled catalytic beds can be used, operating at atmospheric pressure below 400 °C. This methanation process was set to a size of 105 Nm3/day of synthetic methane. Process simulation under steady-state conditions was used to calculate the stream compositions and the inner reactor thermal profile (9.2 MW, as determined by the reaction heat). The dehydration of the produced methane was accomplished by pressure-swing adsorption over a commercial basic zeolite and dynamically simulated. All the foreseen vapor-liquid equilibria have been carefully revised from literature data in order to establish the separation sections on a firm basis. Two further calculations were given for the main energy recovery options and a possible downstream liquefaction.