Recovery of cold energy from liquefied natural gas regasification : applications beyond power cycles

• Main Authors: Khor, Jun Onn, Magro, Fabio Dal, Gundersen, Truls, Sze, Jia Yin, Romagnoli, Alessandro
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Article
• Language: English
• Published: 2020
• Subjects: Engineering::Mechanical engineering; Liquefied Natural Gas; Cold to Cold Applications
• Online Access: https://hdl.handle.net/10356/142255
• Institution: Nanyang Technological University

Liquefied natural gas releases large amounts of cold energy during the conventional regasification process. Currently, most studies have investigated the opportunities to utilize this waste cold for power cycles but few studies considered using this cold directly on other cold applications. In this paper, different cold recovery approaches are considered and compared depending on the energy carriers (i.e. electricity, liquid carbon dioxide, chilled water, liquid air/nitrogen and latent heat storage) used to support a few cold applications (i.e. air separation units, dry ice production, freezing and district cooling). Using different transportation methods, these energy carriers produced using the recovered cold as part or all of their energy input is coupled to these cold applications with different temperature requirements and located 5 km away from the regasification facilities. This paper investigates the change in overall exergy efficiency and carbon dioxide emissions throughout the whole process from energy carrier generation to their consumption in the cold applications when the cold applications are coupled to different alternative energy carriers, compared with the baseline case. With the availability of these alternative energy carriers, conventional cold applications can be modified to reduce their dependency on electricity and improve their performance. The baseline setup has an overall exergy efficiency of ≈13% while using electricity generated by waste cold assisted power cycles as energy carrier yields overall exergy efficiency of ≈13.2%. Using alternative energy carriers charged with recovered cold, such as liquid carbon dioxide/water, latent heat thermal storage and liquid nitrogen, yields lower overall exergy efficiencies of ≈9.7%, 11.5% and 10.2%, respectively which is largely due to the temperature mismatch and thus large amount of exergy destructions during the heat exchange process. For the carbon dioxide emissions analysis, the baseline setup yields carbon dioxide emissions of ≈22.3 kTPA. Using electricity generated with waste cold assisted power cycle yields improvement on carbon dioxide emissions of ≈18.3% while those using alternative energy carriers yield improvements on carbon dioxide emissions of ≈38.0%, ≈37.0% and ≈6.0%, respectively.