Modelling of corrosive trace components in a GTL facility using UniSim

Gas-To-Liquid (GTL) technology, first conceptualized at Shell Amsterdam laboratory in 1973, is a route to make liquid fuels and chemical products from natural gas instead of using crude oil. A large range of products result from the GTL process: base oils, gasoil, kerosene, naphtha, normal paraffins and waxes. The nature of GTL process results in a very pure high-quality synthetic products, allowing the reduction of particulate, NOx, SOx and aromatics emissions which are released during fuels combustion. The emissions levels are lower than those seen when using the liquids fuels produced from crude oil. Corrosive trace components in the effluents of a Fischer-Tropsch unit can be a process safety threat in the downstream section of a gas to liquids facility. Hence, the prediction of the concentrations of these trace components throughout the facility is key as it allows to define the right inspection program or to determine whether other measures are required to reduce risk of loss of containment. The corrosive species are not implemented yet in the integrated simulation model of the GTL process, therefore the aim of this project is modelling the corrosive trace components in the effluents of Fischer-Tropsch unit to predict their concentrations at the plant, including the locations where it is not possible to inspect or take samples. By tracking the species, it is possible to provide data that helps with ongoing research studies or predictive tools. The validation step is carried out by using the available samples from a commercial GTL plant. The model will enable a pro-active monitoring and maintenance of critical areas at GTL plants designed and operated by Shell.