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Fischer–Tropsch Reactor Skid

Fischer–Tropsch Reactor Skid
Pressurized syngas exiting the EERC's fluid-bed or entrained-flow gasifier can be routed to several back-end systems, one of which is a Fischer–Tropsch (FT) reactor with a theoretical liquid production rate of 4 liters (1 gallon) a day per reactor bed. The FT reactor system meters up to 100 slpm (3.5 scfm) per bed of clean, pressure-regulated syngas through a preheater and then into a set of downflow, parallel-packed shell-and-tube reactor beds. The reactor beds can operate at up to 70 bar (1000 psig) and 300°C (570°F), allowing the possibility of methanol or mixed alcohol synthesis in addition to FT catalyst testing.

The shell-and-tube reactor beds are initially heated to temperature using a countercurrent flow of DOWTHERM™ through the external (shell-side) tube. Syngas passing through the beds is then slowly brought to operating pressure, which begins the exothermic FT reaction. As pressure builds and the beds begin to heat under exothermic reaction, the DOWTHERM heater is turned down and the DOWTHERM begins to function as a coolant. Because the packed-bed design lends itself to runaway exotherms, single-pass conversion is kept low, and product gas exiting the beds is recycled through preheater coils to the bed inlets. This dilutes incoming syngas and achieves higher overall conversion efficiencies. Liquid exiting the bottom of the packed beds is collected in a heated wax trap before passing through a set of water-cooled condensers to remove lighter organic material and water. Hot liquid in the wax trap can be recycled to the top of the reactor to provide further syngas dilution and catalyst cooling, thus bringing the inlet to the packed beds closer to outlet conditions. This design allows the packed beds to function similarly to slurry bed designs more commonly used in large-scale FT synthesis. Unrecycled product gas is depressurized and measured through a dry gas meter, and a slipstream is passed to a laser gas analyzer to provide online comparison of inlet syngas and outlet product gas composition.

Because the entire FT unit is compact and skid-mounted, it can be readily moved to any of the different gasification systems located at the EERC or can be loaded onto a truck and coupled to an off-site gasifier. This design flexibility in terms of recycle ratio, operating conditions, heat load or heat removal, and placement makes the FT reactor system a valuable tool for testing catalysts under a wide variety of scenarios.

Useful Links

Fluid-Bed Gasifier

Entrained-Flow Gasifier