Targeting of the Water-Energy Nexus in Gas-to-Liquid Processes: A Comparison of Syngas Technologies

Abstract

The abundant supply of natural gas and the increasing reserves due to substantial shale gas discoveries are spurring much interest in gas-to-liquid (GTL) technologies that can provide various liquid transportation fuels. A primary GTL route involves the conversion of natural/shale gas to syngas which is subsequently converted to liquid fuels using the Fischer− Tropsch (FT) chemistry. The FT process is both energy and water intensive and has resulted in substantial efforts aimed at improving the design and operation of large-scale GTL facilities within the context of sustainability. Although the process technologies have been proven commercially, little is known about the heuristics involved in the selection, design, and operation of certain core process units. In specific, the choice of syngas production technology has been heavily debated based on various factors such as cost, hydrogen-to-carbon monoxide ratio, compatibility with the rest of the process through mass and energy integration, environmental impact, safety, reliability, and controllability. Despite the variety of these detailed issues, there exist macroscopic insights that can aid the engineer and or investor in the selection process. This work aims to highlight some of these insights as they pertain to heat and electrical energy as well as water and greenhouse gas (GHG) emissions. Process design and simulation was done for three GTL processes using commercially demonstrated syngas technologies. Heat and mass integration techniques were used to benchmark the process and identify potential for reduced GHG footprint as well as power and water generation.

Synthesis of C‐H‐O Symbiosis Networks

“…Although the term liquid transportation fuels can be used to describe a variety of products including: methanol, ethanol, DME, it is mostly used to describe the use of Fischer–Tropsch (FT) technology to produce longer chain hydrocarbon liquid fuels . As described by Gabriel et al, the GTL process consists of three main sections: synthesis gas production and conditioning, FT Synthesis, and FT product upgrading and separation . In this study, the GTL liquids capacity is 25,000 bbl/day and the performance models and data are taken from literature …”

“…As described by Gabriel et al, the GTL process consists of three main sections: synthesis gas production and conditioning, FT Synthesis, and FT product upgrading and separation . In this study, the GTL liquids capacity is 25,000 bbl/day and the performance models and data are taken from literature …”

“…In this case study, the six internal sources (Table ) include: FT tail gas, ethane steam cracking offgas, DME by‐product methanol, biodiesel by‐product, COG reformate, and captured CO 2 . The GTL plant produces a 15,000 kmol/h tail gas stream.…”

“…The GTL plant produces a 15,000 kmol/h tail gas stream. In a GTL plant, the utilization of the FT synthesis tail gas is an important process decision variable . The tail gas can be recycled to the reformer or the FT reactor feed to increase the overall conversion.…”

Optimization of multi-effect distillation process using a linear enthalpy model

“…The results may be in the form of networks integrating several technologies. Furthermore, recent advances in energy-water nexus [58,59] can be used to optimize the selection of the energy sources, desalination technologies, and allocation of desalinated water. …”