Mass and heat transfer limitations reduce the efficiency of conventional large Fischer-Tropsch (FT) reactors. The use of microchannel technology – a developing field of chemical processing that intensifies chemical reactions by reducing the dimensions of reactor systems – makes it possible to overcome these limitations, and enable reactions to occur at significantly higher rates than in conventional systems.
Velocys microchannel FT reactors consist of reactor blocks (cores) containing thousands of thin process channels filled with FT catalyst, which are interleaved with water-filled coolant channels. Velocys' process channels have dimensions in the range 0.1 – 10 mm compared to channel diameters in the range of 25 – 40 mm in conventional FT reactors. As a result Velocys reactors are able to dissipate the heat produced by the highly exothermic FT reaction much more quickly than conventional systems, so more active FT catalysts can be used, significantly increasing the productivity per unit volume of reactor.
Velocys reactors with four reactor cores, which have a capacity of 175 barrels per day (bpd), have been successfully manufactured and are being deployed at Velocys’ commercial reference plant in Oklahoma City that is currently under construction.
In addition, the company has successfully scaled up its reactor design to individual reactors with capacities in the range 350 to 1,000 bpd by adding further standard reactor cores within a single pressure vessel. The extensive modelling programme carried out on the design has yielded very positive performance data. While the 175 bpd reactor will continue to be used for plant designs of a few thousand bpd, use of larger reactors will substantially reduce the plant footprint and simplify piping in intermediate size GTL plants.