Polygeneration process design to recover waste cold energy in LNG regasification terminals: simulation-based optimization approach

Abstract Liquefied Natural Gas (LNG) has emerged as a key energy vector owing to its lower carbon footprint. Calorific value specifications at regasification terminals necessitates pre-processing of LNG prior to regasification. Cryogenic distillation for heavy hydrocarbon removal (HHR) from LNG to lower the calorific value utilizes a portion of the available LNG cold energy. However, substantial amount of cold energy remains unutilized in HHR process. To reverse this wastage, a polygeneration process encompassing Organic Rankine Cycle (ORC) for power generation along with diverse refrigeration strategies is proposed following the HHR process. A simulation-based optimization framework is developed to maximize the net present value (NPV) of the proposed polygeneration process and investigate its performance across different LNG feed conditions. Irrespective of LNG feed conditions, the proposed process is found to be technoeconomically feasible resulting in a positive NPV. The optimal process not only generates electricity but also refrigeration sufficient to cool 1,200 data center racks at <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:mrow> <m:mo>−</m:mo> <m:mn>10</m:mn> </m:mrow> </m:math> ${-}10$ °C and a cryogenic warehouse of 2,000 m 3 at <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:mrow> <m:mo>−</m:mo> <m:mn>50</m:mn> </m:mrow> </m:math> ${-}50$ °C. The polygeneration process recovers substantial amount of the remaining cold energy after the HHR process resulting in a CO 2 avoidance of 12.8 kg-CO 2 /ton-LNG, thereby significantly augmenting the technoeconomics and sustainability of LNG value chain.