Identifying Material and Device Targets for a Flare Gas Recovery System Utilizing Electrochemical Conversion of Methane to Methanol

摘要

Natural gas flaring causes enormous damage to the environment, in addition to the wasted energy. The importance of this problem is highlighted by an initiative by the United Nations to end flaring by 2030. There exists an immediate need for identifying routes for converting flare into usable energy. In this study, we propose a scheme that at the core utilizes an electrochemical cell to convert methane into methanol, an easily transportable fuel. The electrochemical cell uses electricity provided by solar photovoltaics to power the electrochemical cell. We carry out a detailed techno-economic analysis of the entire system and analyze the merits and demerits of the proposed approach as compared with other flare gas recovery systems, gas-to-liquid (GTL), electricity generation with gas turbine, gas compression system, and electricity generation by solid oxide fuel cell (SOFC). The developed model shows that the current state-of-the-art materials available for different system components, proton conductor, and electrocatalysts are inadequate to make the scheme practical. We outline the minimum performance metrics, i.e., input voltage at the cell level of ～0.5 V that corresponds to an overpotential of ~1 V and a current density of 0.5 A/cm~2 that requires a proton conductor that can conduct from 10~(-1) to 10~(-2) S/cm in the temperature range of 100-250 ℃, required for the system to become financially competitive. Of note, improvements in the conductivity of proton conductors at intermediate temperatures and identification of active and selective electrocatalysts for the conversion of methane to methanol are the key parameters that determine the overall viability of the proposed scheme. We discuss the environmental impacts of the proposed scheme and provide an outlook on directions required in materials research that could meet the outlined performance metrics.