Coupling of a novel boron-based thermochemical cycle with chemical looping combustion to produce ammonia and power

In this work, a novel thermochemical cycle (Boron-based) to produce ammonia is coupled with chemical looping combustion (CLC) process to produce final primary products of ammonia, CO₂, water, and electricity. Manganese oxide-based CLC provides high purity N₂, water and thermal energy for the carbothermal reduction of liquefied natural gas (LNG) occurring at 1200 °C. Gaseous synthesis gas from the carbothermal reduction is used as a fuel in the CLC's fuel reactor. Ammonia is produced through the hydrolysis of boron nitride (BN) and liquefied at atmospheric pressure. Thermodynamic equilibrium computations are used to predict the conversions of reactions involved in this proposed system. The overall system is then evaluated from energetic and exergetic perspectives to reflect upon the efficiency of reactors and subsystems. The production of approximately 25 metric t/h of NH₃ is achieved while power production reaches 232 MW. The exergetic efficiency of the overall system is calculated to be 53.8%. Moreover, life cycle assessments are performed to assess boron oxide environmental impacts and evaluated the exergy-based allocation of greenhouse gases emission to ammonia at 0.772 kg CO₂ (eq.)/kg NH₃. About 61% reduction in emissions relative to the global average of ammonia synthesis is estimated.