Method combining exergy and pinch analysis for the optimisation of a methanol production process based on natural gas and recovered CO₂

Laboratoire de Génie Chimique, Département PSI – 4 Allée Emile Monso, 31400 Toulouse, France

Abstract

Following the third part of the IPCC report (GIEC, 2022), carbon capture and utilisation of CO₂ emitted by fossil fuel represents one of many ways to curb an increasingly alarming global warming. Reaching this goal implies the transition from a fossil fuel dependant and energy-intensive society to a sober and carbon-free one. According to the (ADEME et al., 2020), steam methane reforming, main production path for syngas, still generates 11 kg CO₂/kg H₂. Countless scientists have already studied different solutions aiming to lower these emissions, including through the design of innovative CO₂ recovering processes. Among these solutions, the integration of CO₂ within natural gas based methanol (MeOH) production processes appears to be promising (Nami et al., 2019 ; Wang et al., 2021). Contributing to the development of these more sober and sustainable production sectors involves the implementation of innovative conceptual approaches, along with the design of processes with excellent energetic performances. To this end, there has been a growing interest in exergy analysis in the last few years. This technique is able to identify and characterise a process’ thermodynamic inefficiencies, thus assisting the engineer in the development of innovative processes (Dincer and Rosen, 2015; Gourmelon et al., 2017). The COOPERE method (COmbiner Optimisation des ProcédEs, Récupération et analyse Exergétique), developed in the Laboratoire de Génie Chimique de Toulouse (Gourmelon, 2015), lies on the combined use of exergy analysis, a case based reasoning approach (Roldan Reyes, 2012) and pinch analysis. This method enables to design processes as energetically sober as economically viable. In this paper, the latter is applied to a MeOH production process based on natural gas and recovered CO₂, described by (Yang et al., 2018).