Gas to Liquids (GTL) Plants

With the increasing volume of stranded natural gas around the world, gas to Liquids (GTL) technology is evolving as an economic means to create value for gas that otherwise has limited value. It competes well with LNG, Fischer-Tropsch, technology has been the preferred catalytic process. GTL solves stranded gas problems.  Sep-Pro is building a 2100 BPD unit that uses 20MMSCFD of natural gas feed. Synthetic fuels have particular acceptance in diesel and avgas.
            Oryx GTL and Shell Qatar GTL plant are operating or being constructed. Reformer design for syngas production, (CO+H2) is critical to this process. Sep-Pro has licensed a reformer technology since this is the major cost component of the GTL process. Fisher-Tropsch remains the dominant reaction sequence for synthetic fuels manufacturing. Generally there are two technical avenues to produce synthetic hydrocarbon liquids.

1. Direct conversion from gas
2. Indirect conversion using syntheses gas (syngas).

The direct conversion is thermodynamicly too inefficient to be economically viable.  The syngas route is more capital intensive since the syngas production step is required but the efficiency is acceptable in the 60-65% range.
            Syngas production can use steam methane reforming (SMR), partial oxidation or a combination. Since the preferred H2/CO ratio is around 2, a combination, auto-thermal reforming (ATR) is preferred.
            The actual Fisher-Tropsch reactions are carried out using either cobalt based or iron-based catalysts. The reactor designs used are either vertical fixed tube with catalyst in the tubes or a slurry reactor where the catalyst is distributed in liquid wax through which heated syngas is purged for reaction purposes. Since the F-T reactions are highly exothermic it is critical that the heat be removed quickly. The reaction temperatures are a major factor in determining the distribution of hydrocarbon products.
            Sep-Pro Systems is focusing on small GTL applications, namely 2000 to 5000 BPD (20MM to 50MMSCFD natural gas feed) GTL liquids production. Since Sep-Pro modularizes where feasible, significant cost savings can be realized in building such plants. Since syngas production is the major cost component, we have developed a cost effective reformer.