In the present research, multi-objective optimization (MOO) was applied to a natural gas-to-liquids (GTL) process with a multi-stage Fischer-Tropsch (FT) reactor. A CO2 stream was fed into the GTL plant’s endothermic steam reformer (SMR) to adjust the H2 to CO ratio of the SMR effluent. Three objective functions were considered in this paper; minimizing the amount of CO2 released to the atmosphere, maximizing carbon efficiency, and maximizing wax production. The degrees of freedom for the GTL process with single-stage FT reactor were recycle ratio to process and recycle ratio to the FT reactor. In addition, for the GTL process with two-stage FT reactor, the synthesis gas split ratio between the stages was considered as another degree of freedom. Maximizing wax production rate results in lower carbon efficiency and higher CO2 emission to the atmosphere. The amount of CO2 intake to the SMR in all cases was 256 tons/hr. With the same amount of utilized CO2 in the SMR, sectioning of the FT reactor to two similar stages notably increases the carbon efficiency and mass flow of wax compared to the single stage case.

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