The existing demonstration plant—which is jointly operated by the Oxford Catalysts Group and SGCE—incorporates an FT microchannel reactor comprising more than 900 full-length microchannels. This reactor has been performing effectively at Güssing since July 2010. The demonstration plant produces more than 0.75 kg of high quality synthetic FT liquids per liter of catalyst per hour and exhibits productivities 4 to 8 times greater than conventional systems.

The significant performance indicators achieved in the demonstration unit include:

• Near isothermal reactor temperature profile. An isothermal temperature profile indicates that the catalyst bed of a reactor is operating at an even temperature throughout, and that the temperature control system (in this case the microchannels) is working efficiently.

• Pressure drop as expected. Pressure drop describes the difference between pressure upstream and downstream of the catalyst bed. Minimization of the pressure drop over a catalyst bed is important to minim ise process costs for a given throughput.

• High quality synthetic fuel being produced (alpha value >0.9). Volumetric productivity is the amount of product that can be produced per liter of catalyst per hour. The alpha value measures the probability of a hydrocarbon chain propagating rather than terminating (producing a shorter hydrocarbon); optimized FT catalysts should achieve an alpha value of 0.90 or above.

• Robust responsiveness to shutdowns and start-ups. Robust responsiveness to planned and unplanned shutdowns and start-ups is required to ensure that activity and productivity can be recovered quickly and completely after an outage.

Microchannel reactors are designed for economical production on a small scale. FT microchannel reactors are compact and have channels with diameters in the millimeter range. Conventional reactors are many times larger and have channel diameters in the centimeter range.

Because the smaller diameter channels in microchannel reactors dissipate heat more quickly than those in conventional reactors, more active catalysts are used to boost the conversion rates to an economic level.

When used with a new FT catalyst developed by Oxford Catalysts, the Velocys microchannel FT reactor exhibits conversion efficiencies in the range of 70% per pass. A single microchannel reactor block, measuring 60 x 60 x 60 cm, might produce around 30 barrels (bbls) of liquid fuel/day, the company says.

In contrast, conventional FT plants typically exhibit conversion efficiencies in the range of 50% or less per pass, according to the company. They are designed to work at minimum capacities of 5,000 bbls/day, and function well and economically only at capacities of 30,000 bbls/day or higher.

Resources

• Microchannel GTL Technology; Demonstration through to Commercialisation: Presentation given by Oxford Catalysts Group at SMI Gas-to-Liquids (27-Oct-10)