This thesis investigates the operational performance and optimization of aGas-to-Liquid plant based on autothermal reforming (ATR) and a multitubular fixed bed (MTFB) reactor together with a cobalt catalyst. This isachieved through simulation of the process in Unisim Design R400. Thesimulations were based on a feed designed for a 17000 bbl/d train and doesnot incorporate the upgrading unit. The work is divided in three main sections;parameter study, optimization on syncrude flow, carbon- and thermalefficiency and optimization with consideration to economics including heatintegration through pinch analysis. The optimized process was found toproduce 19940 bbl/d of syncrude with a carbon efficiency of 82.41% and thermalefficiency of 65.93%, when not taking economics into consideration.The inclusion of economics changed the operational optimum to a syncrudeproduction of 18620 bbl/d and efficiencies of 77.25% and 61.77% respectively.Ultimately a production cost of 16.10 USD/bbl and revenue of 59.89 USD/bbl wasobtained. With current crude oil price at 98.90 USD/bbl it indicates a goodeconomical environment for the Gas-to-Liquid process
