Solar methanol by hybridizing natural gas chemical looping reforming with solar heat

Abstract

Liquid sunshine is a concept for converting solar energy into liquid fuel. Methanol is an attractive candidate as the liquid fuel due to the long-period experiences in large-industrial scale of methanol production. Solar driven chemical looping process is considered as a way to produce raw materials of methanol synthesis. To achieve the transformation from solar energy to the chemical energy of liquid fuel, an integrated system based on the solar-driven chemical looping process using methane for methanol production is proposed. During the chemical looping process, solar heat is absorbed by the reaction to convert methane into syngas with a reasonable hydrocarbon ratio. The syngas as raw materials would be sent into a two-tower tandem methanol synthesis sector. The obtained crude methanol would be rectified and stored as the product. A preliminary parameter analysis helps to get the optimal reaction conditions of the chemical looping process, as the reaction temperature of 600 °C, CH4-to-NiO ratio of 1.25 and H2O-to-CH4 ratio of 0.7. In addition, the system was simulated and the energy analysis and exergy analysis are examined. The results show that energy efficiency is about 62%, and exergy efficiency is about 65%. In addition, the stored chemical energy in methanol can be released by employing solar energy again. The solar heat at around 250 °C driven methanol cracking process can be further released and coupled with an internal combustion engine for power generation. The net solar to electricity efficiency is evaluated and reaches around 23%. In this study, by solar-driven natural gas chemical looping process coupled with methanol synthesis, we would expect to provide a new pathway for further development of liquid sunshine.