Mini Review Volume 4 Issue 4 - March 2018 DOI: 10.19080/RAPSCI.2018.04.555644 Recent Adv Petrochem Sci Copyright © All rights are reserved by Nuno Soares Domingues Screw Expander for Energy Production in Natural Gas Pressure Reduction and Mesurement Stations João Reis, Jorge Mendonça e Costa and Nuno Soares Domingues* Departamento de Engenharia Mecânica, Instituto Superior de Engenharia de Lisboa, Portugal Submission: February 27, 2018; Published: March 19, 2018 *Corresponding author: Nuno Soares Domingues, Departamento de Engenharia Mecânica, Instituto Superior de Engenharia de Lisboa, Lisboa, Portugal, Email: Abstract The current energy paradigm requires a strong need not only to use sustainable energy sources but also to make better use of existing energy resources. This last category, represented, mainly, by fossil fuels, needs new and better practices where they are fully used. Within fossil fuels, natural gas has a relevant role, mainly because of its low levels of pollutant emissions, with respect to other fuels, and its abundance in nature and in coping with consumption variation. However, this resource is not fully utilized, since during natural gas pressure reduction processes a great amount of energy is wasted that otherwise could be harnessed and converted into electrical energy. The aim of this paper is to qualitatively define and evaluate the performance of a screw-type expansion machine to be installed in natural gas pressure reduction and measurement stations (GPRMS) in order to take advantage of the higher enthalpy level available in the gas in order to generate electrical energy during the expansion process. After a definition of the expander, it is intended to discuss if it exceeds the classical solution corresponding to a conventional turbine for the purpose of energy generation, allowing an effective response to the strong daily variation of flow in the gas line. Keywords: Pressure reduction; Natural gas; Expansion; Screw expander; Energy Introduction The current process of natural gas pressure reduction leads to a loss of the gas total available energy, transforming its harvestable portion into heat, during the throttling process in the regulator valve used for the pressure reduction purpose. Using an expander, instead of a valve, induces a distinct pressure reduction process which leads to work production through the expander by means of a change in the flow’s enthalpy, instead of a change in the flow’s entropy as occurs in a valve throttling process [1-3]. Up till now the use of a turbine as the expander is the most common solution, if not the only one. This solution, as good as it may sound, presents its fair share of downsides resulting in a small application throughout the gas pressure reduction and measurement stations (from now on called simply by their acronym, GPRMS) worldwide. These downsides are mainly economic, and even the ones regarding the process or the expander, show themselves, ultimately, as economic. Therefore, in order to suppress some of the main disadvantages of the conventional turbine, we can adopt another machine, in an effort to completely harness natural gas pressure energy, thus rendering it more profitable and consequently increase its worldwide use. Efforts in study and implementation of screw machines as expanders may become a reality, provided that these machines successfully surpass the disadvantages inherent to a turbine [4,5]. Literature Review Literature about screw machines is very scarce, although some interest in these machines is starting to show. This is mostly due to the fact that until now most of the proprietor knowledge and data about these machines is out of the scope of academic institutions, worldwide, that do not promote their understanding and development. Additionally, building on the few published studies and information to this equipment, a big portion of printed material is not readily available in English, according to [6]. Despite the obstacles presented in the last paragraph there are still some insightful references about screw machines and the application of screw expanders in Organic Rankine Cycles (ORC’s). In these fields of study, we would like to highlight two main authors, namely Ian Smith and Nikola Stosic whose work consists in a substantial amount of publications that provide ground knowledge to almost all the remaining authors that tackle this subject. References [1] and [5] tackle some aspects of gas expansion power production and the main aspects to take into account, Recent Adv Petrochem Sci 4(4): RAPSCI.MS.ID.555644 (2018) 0082