Department of Chemical Engineering
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Item Performance Analysis of Heat-Integrated LNG Regasification with Air Separation Units(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2025) Muhammad Naeem Khalid; CIIT/FA23-RCH-005/LHR; Dr. Muhammad Haris Hamayun; LHR TP 10009Pakistan has a strong dependency on natural gas as an energy source to fulfil both the domestic and industrial requirements. Due to depletion of reserves of natural gas in Pakistan, this gas, in the form of liquefied natural gas (LNG), is imported, mainly from Qatar. However, there are several issues associated with this imported LNG. The LNG needs to be regasified before use in the existing infrastructure, the calorific value of imported LNG is higher than the design specifications, and the cold energy/exergy stored in LNG is wasted via the current method of regasification, mixing with the remaining reserves of natural gas. To overcome these issues, there is a need to integrate LNG regasification process with a process that can provide an inert, i.e., nitrogen to lower the calorific value of this LNG to meet the existing design specifications, to extract/use the cryogenic energy of LNG to lower the overall energy requirements, and eventually to regasified LNG for onward use by the users. Cryogenic air separation process appears to be the most suitable process for the integration with LNG regasification that can help in achieving the required objectives. Accordingly, this study aims to integrate the cryogenic air separation process and LNG regasification process, and the model is developed using Aspen HYSYS® V15. To the best of our knowledge, the developed process is examined using exergy, advanced exergy and exergoeconomic analyses, however, so far, optimization via evolutionary algorithm is not reported in literature. Therefore, this research gap is addressed in this study by employing teaching learning self-study-optimization algorithm. The base case model developed in Aspen HYSYS® V15 is integrated with MATLAB and the algorithm is applied to carry out rigorous optimization. The optimization results show an increase in the air processing capacity from 500 tons per hour (TPH) to 638.9 TPH with the maximum utilization of the cryogenic energy of LNG. The overall specific energy consumption is increased by 21.66% keeping the same energy consumption of air. Followed by the optimization, the process is then evaluated thermodynamically using the exergy analysis. The analysis demonstrated that the % exergy efficiency of the optimized process is 72.51% with an exergy destruction of 36.42 MW. The overall optimized process may help in providing a more feasible and sustainable design toward the practical implementation of this integrated configuration in context of Pakistan.