Heat Recovery From a Liquefied Natural Gas Production Process by Means of an Organic Rankine Cycle

In the last years, the increased demand of the energy market has led to the increasing penetration of renewable energies in order to achieve the primary energy supply. However, natural gas is expected to still play a key role in the energy market, since its environmental impact is lower than other fossil fuels. It is mainly employed as gaseous fuel for stationary energy generation, but also as liquefied fuel, as an alternative to the diesel fuel, in vehicular applications. Liquefied Natural Gas is currently produced mainly in large plants directly located at the extraction sites and transported by ships or tracks to the final users. In order to avoid costs and environmental related impact, in previous studies Authors developed a new plant configuration for liquefied natural gas production directly at filling stations. One of the main issues of the process is that in various sections the working fluid needs to be cooled by external fluids (such as air for compressor inter and after-cooling or chilling fluids), in order to increase the global performances. As a consequence, an important amount of heat could be potentially recovered from this Liquefied Natural Gas production process. Thus, based on the obtained results, in this study the integration between the liquefaction process and an organic Rankine cycle is proposed. In fact, the heat recovered from the Liquefied Natural Gas production process can be used as hot source within the organic Rankine cycle. The aim of the work is the identification of the optimal integrated configuration, in order to maximize the heat recovery and, as a consequence, to optimize the process efficiency. With this purpose, in this study different configurations — in terms of considered organic fluid, architecture and origin of the recovered heat — have been defined and analyzed by means of a commercial software. This software is able to thermodynamically evaluate the proposed process and had allowed to define the optimal solution.