Fischer-Tropsch synthesis is used to convert gaseous carbon monoxide and hydrogen into a variety of hydrocarbons in liquid form, often called "syngas conversion". Both hydrodynamics and chemical reactions are important in determining the amount of syngas conversion that takes place in any given system; hence CFD is ideally suited to model this process and to optimize the equipment.

In the example shown here, FLUENT is used to model the formation of liquid phase products (water and a collection of hydrocarbons in the methylene group) from syngas. The gas is injected through a circular opening with a diameter slightly less than the column diameter. The reaction rate is dominated by mass transfer across the gas-liquid interface. The first figure shows the volume fraction of liquid after 5, 10, 15, 20 and 60 seconds of operation. Red corresponds to pure liquid, and blue corresponds to pure gas. Gas eventually displaces the liquid and causes the liquid level to rise. The second figure shows the mass fraction of hydrocarbons (one of the products in the liquid phase) at 5, 10, 15, 20 and 60 seconds. The increased amount of product near the bottom of the column is the result of recirculation currents that become established during operation, which can be easily identified and predicted with CFD.

Liquid phase volume fraction at 5, 10, 15, 20, and 60 seconds

Liquid product concentration at 5, 10, 15, 20, and 60 seconds