(576b) Modular Gas-to-Liquids Process with Membrane Steam-Methane Reformer, Fischer–Tropsch Reactive Distillation and Integrated Product Refining

Shale/natural gas can be converted to liquid fuels through gas-to-liquids (GTL) processes that are applied commercially in a number of plants around the world. One of the biggest challenges associated with GTL processes is the high capital costs of these plants. Small-scale GTL have the advantages of being less capital intensive, less risk, and with the potential of utilizing gas reserves which previously could not be exploited, i.e. associated and stranded gas reserves. However, the cost per barrel of these processes still remains high, if conventional technology is employed [1]. Novel reactive distillation processes are paving the way for a more sustainable chemical process industry that is profitable, safer and less polluting [2].

Zhang et al. [3] developed an equation-oriented framework for optimal synthesis of integrated reactive distillation (RD) systems for Fischer–Tropsch processes in GAMS which has recently been implemented in PYOMO. To produce synthesis gas at the required H₂/CO ratio for the RD process, we are developing an membrane steam-methane reforming (SMR) model. This optimization-based model provides flexibility in both process design and operation. The excess hydrogen from the reformer is used to optimize gasoline and diesel production in the product refining sections.

The models are developed in Python and the optimization of the integrated flowsheet is implemented in PYOMO. The use of the SMR with internal hydrogen separation greatly improves conversion and lowers operating conditions. This type of modular design and integration of processes, which is suitable for small-scale plants, also has the potential to ease the scalability of the process.

[1] W.D. Shafer, M.K. Gnanamani, U. Graham, J. Yang, C.M. Masuku, G. Jacobs, B.H. Davis, Fischer–Tropsch: product distribution – The fingerprint of synthetic fuels, Catalysts 9 (2019) 259.

[2] C.M. Masuku, L.T. Biegler, Recent advances in gas-to-liquids process intensification with emphasis on reactive distillation, Curr. Opin. Chem. Eng. (2019) https://doi.org/10.1016/j.coche.2018.12.009.

[3] Y. Zhang, C.M. Masuku, L.T. Biegler, Equation-oriented framework for optimal synthesis of integrated reactive distillation systems for the Fischer–Tropsch processes, Energy Fuels 32 (2018) 7199–7209.

Keywords: Equation-Oriented Optimization Framework, Detailed Kinetic Model, Small-Scale GTL, Fischer–Tropsch Synthesis, Process Intensification.