Carbon Dioxide to Methanol Valorisation by Process Intensification

Abstract

The social and scientific effort to transition from fossil fuels to renewables or other eco-friendly energy alternatives is not enough to satisfy the increasing global energy demand. That leads to the continued use of fossil fuels, which causes a rising CO₂ concentration into the atmosphere. Carbon capture, utilisation, and storage (CCUS) techniques are being developed to mitigate its negative consequences because fossil fuel consumption is still required. The methanol (MeOH) production from the collected CO₂ is an industrial example of carbon utilisation. This process is currently carried out in three steps. In the first step, the CO₂ in the monoethanolamine (MEA) solution is thermally liberated (thermodynamically non-spontaneous). The first step is the thermal liberation of the CO₂ trapped in the MEA 30 wt.% aqueous solution. After that, the reactor is fed with H₂ and the released CO₂ to initiate the MeOH reaction (thermodynamically favourable). The MeOH is finally collected using distillation (thermodynamically non-spontaneous). The energy consumption of a process decreases when it combines a thermodynamically favourable process with a non-favourable process. The aim of this study is to examine, through rigorous simulation, the possibilities of process intensification. The performance of CO₂ desorption and hydrogenation in a single step is analysed with Aspen Plus®. The capacity to combine the two units creates a new field of inquiry for this method's energy-saving potential. After experimental analysis of its viability and its optimisation for maximising energy savings, the industrial impact is assured. Further research is needed to achieve reducing energy since the resultant energy of the overall system (the Reactive-Desorber Column plus two distillation columns) consumes 70 GJ/t MeOH. Nevertheless, the first simulation presented in this study indicates that a desorption-reaction column may be feasible, providing an alternative path for investigation into how to enhance the CO₂ hydrogenation to MeOH process.