Integrating life cycle assessment for design and optimization of methanol production from combining methane dry reforming and partial oxidation

Abstract

CO2 capture and utilization (CCU) is a potential solution for combating global warming potential. Utilization of CO2 as a renewable raw material for producing methanol has been intensively investigated. Nevertheless, the benefits of CO2 utilization cannot be guaranteed unless the entire production process is rigorously evaluated and optimized. This study attempts to minimize CO2 emissions of the methanol production process via the synthesis of intermediate syngas using the dry methane reforming (DR) method in combination with the partial oxidation (PO) of methane. We noted that the contributions from DR and PO to the overall reaction process depended on the input raw material ratios. Marked differences in desired operating conditions were noted when maximizing syngas and methanol yields, thereby making process optimization difficult. Herein, to find the optimal operating conditions for minimizing overall CO2 emissions, effective process design and simulation, and the cradle-to-gate life cycle assessment (LCA) were integrated. Process CO2 emissions, including those from all sources of indirect and direct CO2 emissions from raw materials, utility production processes, and “end-of-pipe” waste treatment option were evaluated based on noted variations in the identified key variables. Suitable operating conditions for reducing the total process CO2 emissions were proposed. Although the current study results in low level of CO2 utilization, it attains a low CO2 emissions process for producing methanol via syngas (i.e., 0.81 kg CO2/kg methanol). The results obtained herein highlight the significance of implementing LCA method using suitable evaluation boundary to design environmentally friendly CO2 utilization processes.