Nitrogen self-recuperation expansion-based process for offshore coproduction of liquefied natural gas, liquefied petroleum gas, and pentane plus

Abstract

In the current scenario of energy challenges, natural gas (NG) and associated liquids such as liquefied petroleum gas (LPG) are considered to be clean energy sources compared with coal and oil. Liquefaction is one of the most feasible and safe approaches for transporting NG from the site of production to the site of consumption. However, NG processing to produce liquefied natural gas (LNG) and LPG is extremely costly in terms of both operating and capital expenses because it requires a tremendous amount of energy, particularly at offshore sites. We have developed a new liquefaction process that uses N2 self-recuperation rather than external precooling with 80% less energy consumption than that required by existing single N2 expander processes. In this work, we evaluate the use of an innovative self-recuperative expander-based integrated process to produce LNG–LPG–pentane plus (condensate) at an offshore site in an energy-efficient manner with minimal capital expenditure. Thermodynamic and economic analyses were performed to evaluate the commercial feasibility of the proposed process. Furthermore, the environmental impact in terms of CO2 emissions was calculated. This study reveals that LNG–LPG can be produced at a specific energy expense of 0.2362 kW with a payback period of 1.38 years.