Evaluation of alternative processes of methanol production from CO2: Design, optimization, control, techno-economic, and environmental analysis

•Six schemes of the process producing MeOH via CO2 hydrogenation are evaluated.•The best scenario (Scheme 5) has MRSP = 998 USD/Ton-MeOH and CO2-e = −1.314 Ton/Ton.•Use H2 which emits less than 6.554 Ton-CO2/Ton-H2 leads to net decarbonization.•The trade-off between the decarbonization and process economics is revealed.•A suitable control strategy is proposed to the best scenario to reject the feed disturbances. Converting carbon dioxide (CO2) to methanol via direct hydrogenation has been regarded as an essential part of the pursuit of a decarbonized energy economy. This study first explored and evaluated alternative processes for converting CO2 to methanol, in which six schemes based on adiabatic and/or non-adiabatic fixed-bed reactors were focused. The research scope includes rigorous process design, optimization, techno-economic and environmental assessment, and control. The generated results indicate that the two-reactor system (Scheme 5), which employs a non-adiabatic one as the first stage and a adiabatic one follows, has the lowest production cost. This process reveals great potential for decarbonization (i.e. CO2-e = −1.314 Ton-CO2/Ton-MeOH), whereas less economic attractiveness (i.e. minimum required selling price (MRSP) of methanol = 998 USD/Ton, average market price = 378 USD/Ton). Correspondingly, the maximum allowable CO2 emission from utilizing hydrogen (MACEH2) was found to be 6.554 Ton-CO2/Ton-H2. This indicated that using hydrogen produced from steam methane reforming (SMR) with carbon capture on both syngas and flue gas (i.e. 5.7 Ton-CO2/Ton-H2) leads to net decarbonization. Furthermore, if the emission associated with the CO2 feed (specific energy = 2.8 GJ/Ton-CO2) is also considered, net decarbonation would be achieved by using hydrogen produced from biomass gasification (i.e. 3.1 Ton-CO2/Ton-H2). A more comprehensive comparison between various CO2 utilization processes, in terms of the decarbonization ability and economics, was performed. Through this, it is concluded that there has been no existing CO2-based process that is attractive in both aspects. Finally, a suitable control strategy was proposed for the selected scheme, which suitably handles the throughput and composition disturbances.