Optimal design and integration of a cryogenic Air Separation Unit (ASU) with Liquefied Natural Gas (LNG) as heat sink, thermodynamic and economic analyses

LNG regasification terminals are the final destination of LNG carriers. This is where the liquefied natural gas is returned to the gaseous state and fed into transmission and distribution grids. While regasification process, cryogenic LNG has a great potential for cold energy recovery. This cold energy can be used in various applications such as power generation, material freezing and sea water desalination. In this study, we used the mentioned cold energy for cryogenic air separation unit to improve the performance of this cycle. Some of the most important results of this integration are 8.04% reduction in the amount of power requirement and also 17.05% reduction in initial capital cost of ASU plant. In this paper, the required LNG flow rate for applied integration was 24.43% of ASU cycle generated oxygen flow rate. Annualized cost of system was chosen as an economic approach. A year reduction of system period of return in relation to the before integration of ASU cycle with LNG, was the most important economic result of this integration. Sensitivity analysis was done on the system economic parameters (electrical energy, oxygen and nitrogen price). The results show that the considered integration will have a more positive impact on the system period of return in higher prices of electrical energy and also in lower prices of oxygen in the market. - Highlights: • The optimal use of LNG cold energy considering regasification on cryogenic ASU cycle. • Applying pinch analysis to design HEN and maximize the use of LNG cold energy. • Applying annualized cost of system (ACS) method for economic analysis. • Sensitivity analysis on the system economic parameters.