Energetic and exergetic evaluation of methanol synthesis process in a hybridized system of methane cracking, chemical looping combustion, thermal desalination and photovoltaic panels

Abstract

Due to limited energy supply sources and environmental issues, the use of renewable energy to replace fossil fuels and reduce pollution has increased. One of the easiest, safest, and most portable ways to store renewable energy for a long time is to convert it to liquid methanol. In this paper, a novel integrated system is developed for cogeneration of liquid methanol and freshwater using methane cracking unit integrated with chemical looping combustion, methanol production cycle, multi-effect desalination, and photovoltaic panels. The thermal integration of new structures for cogeneration leads to a reduction in the number of equipment used and an increase in efficiency. This integrated structure produces 23.97 kmol h−1 liquid methanol, 204.3 kmol h−1 desalinated water, 42.49 kmol h−1 solid carbon, 58.52 kmol h−1 nitrogen, and 668.9 kmol h−1 hot water. The waste heat of the chemical looping combustion is used to supply methane cracking unit, which produces 84.99 kmol h−1 hydrogen, 7.582 kmol h−1 carbon dioxide, and 24.74 kW power. These products and the excess carbon dioxide supplied from outside are used as input feed for the liquid methanol production cycle. Waste heat from the liquid methanol production cycle is used to supply heat to the thermal desalination cycle and produce hot water. The thermal energy and exergy efficiencies of the integrated structure are 48.64% and 71.68%, respectively. In the hybrid structure, the largest share of exergy destruction belongs to reactors (65.61%), photovoltaic panels (17.73%), and heat exchangers (10.97%), respectively. Sensitivity analysis in different operating conditions is used to investigate the sensitivity and changes in the output and important parameters of the process.