Abstract
Cold thermal energy of LNG that is usually rejected into sea-water can be effectively utilized in an air separation unit (ASU) to reduce power consumption and carbon footprint. ASU producing liquid oxygen, which is the most saleable of its products, consumes 47.9% lower power with the utilization of LNG cold energy. However, it poses a finite fire safety concern for flammable hydrocarbon such as LNG in presence of oxygen in the same heat exchanger. An ASU becomes safer if LNG cold energy is extracted by nitrogen in a separate heat exchanger though it consumes 4.4% higher specific power. A further step towards a more reliable plant is taken by producing and storing a small quantity of liquid nitrogen that is used to keep the plant cold when the LNG supply is disrupted. The proposed modified ASU, that is simpler in design, more reliable in operation, has a lower power consumption and capital investment, is safer and can withstand LNG supply shut down for sufficient duration, and environment-friendly, meets the major criteria of sustainable energy planning. With the use LNG cold energy, the plant requires between 15% and 17% lower investments compared to the one without LNG cold utilization.
Published Version
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