Development and assessment of concentrated solar energy driven ammonia synthesis from liquefied natural gas

The proposed system targets the production of carbon dioxide-free hydrogen from liquefied natural gas through a solar-driven catalytic thermal cracking process integrated into the ammonia synthesis unit. The catalytic material is being regenerated in an adjacent vessel by burning the deposited coke. As a result, pure carbon dioxide stream is obtained and can be used directly in urea synthesis, sequestration or other related applications. It is expected that the system will reduce the amount of fossil fuel consumption in the ammonia synthesis and mitigate the associated environmental impacts. The energetic and exergetic analyses are carried out to assess the performance of the developed system and to identify the optimum operating conditions. At an operating temperature of 900 °C of thermocatalytic cracking, the optimum pressure for optimal production of hydrogen is determined to be 23.8 bar. The corresponding overall energy and exergy efficiencies are calculated as 35.8% and 37.4%, respectively. At the same conditions, the energy and exergy efficiencies of the thermal cracking unit reach 61.8% and 59.3%, respectively. Several parametric studies are conducted to evaluate the effects of operating conditions at the cracker, irradiance day-night ratio, and consideration of CO₂ for transport and sequestration activities on the overall performance and production of the system. Ammonia production can reach 974 Metric Tons per Day (MTPD) and 893 MTPD considering operating conditions of 900 °C and 800 °C, and inlet LNG flow rate of 688 MTPD and 630 MTPD, respectively.