Economic evaluation of a new small-scale LNG supply chain using liquid nitrogen for natural-gas liquefaction

- A small-scale natural gas supply chain using liquid nitrogen is suggested.
- The supply chain is evaluated in terms of life cycle cost and life cycle profit.
- The profit of the supply chain is maximized when the pressure of LNG is 7 bar.
- The liquefaction process is economical when the flowrate of LNG is under 27 ton/h.

This study proposed a new LNG (liquefied natural gas) supply chain using liquid nitrogen (LN2) to liquefy natural gas on a small scale, and analyzed the life cycle cost (LCC) and the life cycle profit (LCP) for the supply chain. Natural gas was liquefied with the latent heat of LN2 without any turbo-machines. The LNG was transported to an LN2 production site, where LN2 was produced with the cold (cryogenic) energy of the LNG. Then, LN2 was transferred to the LNG production site again, completing the cycle. To verify the economics of this supply chain, the LCC and LCP were estimated with different design and operation conditions. This supply chain was found to be significantly profitable because it efficiently used the cold energy of both LNG and LN2, eliminating the required cost for the regasification process. The results of LCC and LCP showed that the profit of the supply chain was maximized when the pressure of the LNG product was approximately 7 bar, irrespective of the transportation distance. This was because the latent heat and density of LNG were different from those of LN2. The distance between the LNG and LN2 production sites was the dominant parameter that governed the economics of this supply chain.