Development and multi-objective optimization of a newly proposed industrial heat recovery based cascaded hydrogen and ammonia synthesis system

The industrial flue gas emitted to the atmosphere is considered not only harmful to the environment but also a waste of plentiful resources of thermal energy. The thermal energy extracted from the industrial flue gas can be employed for multiple purposes. This study proposes a new configuration to integrate the thermal management of industrial flue gas for thermochemical copper-chlorine (Cu-Cl) cycle based ammonia synthesis. A reverse osmosis desalination unit is employed to supply the freshwater required by the thermochemical Cu-Cl cycle. To recover the heat from high-temperature oxygen stream, thermoelectric generators (TEGs) and organic Rankine cycle (ORC) are integrated with the proposed configuration to utilize the low-grade waste heat for power production. A portion of produced hydrogen through the thermochemical Cu-Cl cycle is supplied to the cascaded system for ammonia production. A double-stage cascaded ammonia synthesis system is integrated with the proposed configuration to achieve high fractional conversion. A multi-objective optimization using genetic algorithm is implemented to the proposed system using the MATLAB to investigate and determine the best-operating temperatures and pressures for the ammonia synthesis system. The proposed configuration produces 518.4 kmol/day of hydrogen and 226.8 kmol/day of ammonia. The overall exergetic and energetic efficiencies are found to be 28.7% and 40.8%. Moreover, the results obtained from the comprehensive sensitivity analyses are presented and discussed.