Volume 9 • Issue 1 • 1000373 J Chem Eng Process Technol, an open access journal ISSN: 2157-7048 Research Article Open Access Gai et al., J Chem Eng Process Technol 2018, 9:1 DOI: 10.4172/2157-7048.1000373 Research Article Open Access Journal of Chemical Engineering & Process Technology J o u r n a l o f C h e m i c a l E n g i n e e r i n g & P r o c e s s T e c h n o l o g y ISSN: 2157-7048 *Corresponding author: Helen H Lou, Dan F Smith Department of Chemical Engineering, Lamar University, Beaumont, USA, Tel: 409-880-8207; E-mail: Helen.lou@lamar.edu Received January 11, 2018; Accepted February 09, 2018; Published February 20, 2018 Citation: Gai H, Zheng K, Lin J, Lou HH (2018) Process Simulation, Economic and Environmental Sustainability Assessment of a Gas-To-Liquids Process. J Chem Eng Process Technol 9: 373. doi: 10.4172/2157-7048.1000373 Copyright: © 2018 Gai H, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Process Simulation, Economic and Environmental Sustainability Assessment of a Gas-To-Liquids Process Huilong Gai, Kailiang Zheng, Julia Lin and Helen H Lou* Dan F Smith Department of Chemical Engineering, Lamar University, Beaumont, USA Abstract Natural gas is recognized as one of the cleanest and most abundant fossil fuels. In the past decades, the price ratio of crude oil to natural gas has continuously fuctuated. The gas-to-liquid industry has received continuous interest due to the abundant supply of conventional and unconventional natural gas (shale gas, etc.), as well as the environmental advantages of FT technology. The GTL process chemically converts natural gas to long chain hydrocarbons (naphtha, diesel, wax, etc.) through three main steps, i.e., natural gas reforming, Fischer-Tropsch synthesis (FTS), and products upgrading. In this work, a rigorous simulation model including gas sweetening, syngas production, FTS, and product fractionation is provided. Among different routes for natural gas reforming and different reactors for FTS in a GTL process, autothermal reforming (ATR) and slurry bubble column reactor (SBCR) were chosen respectively, due to their advantages over other solutions. Meanwhile, the economic and environmental analyses were also conducted for the sustainability assessment of provided GTL process using Aspen Icarus and WAR software. Keywords: Natural gas; GTL process; FT technology; Sustainability; Process simulation Introduction Natural gas is recognized as one of the cleanest and most abundant fossil fuels. Te price ratio of crude oil to natural gas has continuously [1,2] fuctuated in the past decade as shown in Figure 1. Due to the abundant supply of conventional and unconventional natural gas (shale gas etc.), the gas-to-liquid industry has received continuous interest. Furthermore, the continuous development of shale gas has made the fare problem an increasingly serious, worldwide issue. GTL processes will open up new resources, such as capturing gases and making proft, while minimizing fare problems. Te GTL process converts natural gas to longer-chain hydrocarbons (naphtha, diesel, wax, etc.). Tese conversions take place through reforming of natural gas to syngas and Fischer-Tropsch (FT) synthesis of syngas to higher hydrocarbon products, i.e., long-chain hydrocarbon molecules. GTL provides a good method of utilizing many “stranded gas resources”, which are located too far from potential markets for economically feasible transportation. Tere are also environmental advantages for using FT-based GTL technology. Compared to conventional fuels derived from crude oil, FT fuels contain low concentrations of sulfur compounds, NO x , and aromatics. Tese properties, along with a high cetane number (approximately 70) result in superior combustion characteristics for the FT diesel fuel. As the market normally requires a cetane number of at least 45, the FT diesel can be used in both areas where there are very tight constraints on diesel quality and as a blending stock to upgrade lower quality diesel fuels [3]. Additionally, GTL technology can also help suitable countries achieve a more secure energy supply. Several GTL plants are operated or under construction in places like South Africa, Nigeria, Qatar, United States, etc. In addition to the 14,500 bbl/day GTL plants in Malaysia, which began operation in 1993, Shell has also built a world scale GTL plant (Pearl GTL plant) with a capacity of 140,000 bbl/day in Qatar, which started production in 2011. In addition to its plants in South Africa, Nigeria, and Qatar, Sasol announced a new GTL plant in the United Sates with a capacity of 96,000 bbl/day and began construction in 2013. Furthermore, several GTL plants have been under construction since 2015 worldwide. In addition to the large-scale plants in South Africa and Uzbekistan, multiple companies have been investing in small scale GTL plants in Russia and US to convert natural gas resources instead of faring [4]. Another hotspot of GTL process is modular design of small-scale GTL plant. Much of the remaining natural gas resource is in the form of associated or stranded gas which is hard to monetize due to its low volume and lack of supporting infrastructure. Modular GTL plant provides a way to take advantage of this potentially abundant energy resource economically and in an environmentally responsible way. Essentially, these technologies involve pre-manufacturing unit which is compact and can be shipped to site of interest and easy to assemble and dis-assemble. Tese technologies are currently in the early stages of commercialization by several companies, such as Compact GTL, Verdis Fuels and Velocys [5]. A GTL process mainly comprises of three steps, as shown in Figure 2, which are the reforming of natural gas to syngas, Fischer- Tropsch reaction of syngas to hydrocarbons (also called syncrude), and upgrading of syncrude by fractionation, hydro-treating, hydro- cracking, and hydroisomerization to yield products that meet the petroleum product market’s specifcations. Acid Gas Removal and Syngas Production Modeling If the sour gas content is high, the frst step of a GTL process will be an acid gas removal unit, where CO 2 and H 2 S are removed, as