Process Simulation and Optimization of Alternative Liquid Fuels Production A techno-economic assessment of the production of HEFA Jet Fuel

Kurzfassung

Climate change has its origin in human activities, and particularly due to the combustion of fossil fuel. Therefore, politics have set ecological targets for the transport sector and especially for the aviation sector. For example, the International Civil Aviation Organization Assembly (ICAO) set in 2013 that the net aviation CO2 emissions should be reduced by 50% until 2050, relative to 2005. This amount corresponds to a demand of approximately 10 million tons of alternative jet fuel in 2050 in Germany. In order to achieve these objectives, bio jet fuels coming from renewable sources are required. For the past few years, first generation biofuels that comes from food crops like sugar and vegetable oils have been investigated and promoted. However, some concerns about the future availability of their feedstock and thus their ability to reach these targets have been raised. That is why second generation biofuels producing from biomass and waste have been focused on in the recent years. Among all of these biofuels, a few have already been approved by the ASTM International for aviation applications, like sustainable fuels from Fischer-Tropsch Synthesis and HEFA jet fuel (Hydroprocessed Esters and Fatty Acids). Both can be mixed with fossil fuel up to 50% vol. While sustainable fuels from Fischer-Tropsch have not yet been commercially produced in large quantities, the HEFA process is state-of-the-art and worldwide applied. That is why the focus of this thesis is on the HEFA process and the potential of HEFA process in Germany, since no production capacities for HEFA exists so far in this country. HEFA-process is based on the hydrogenation of vegetable oil, followed by hydrocracking and isomerization reactions. The obtained products are hydrocarbons, with similar boiling range as conventional diesel, jet fuel and naphtha, though, the later mentioned was internally used to cover the significant hydrogen demand. The technical potential and the economic feasibility of HEFA process have been estimated afterwards, through a preliminary literature survey, secondly a simulation study with the commercial software Aspen Plus® and finally a techno-economic assessment with the Techno-Economic Process Evaluation Tool (TEPET). The technical potential of suitable raw materials applicable in the HEFA process has been analyzed for Germany, whereby rapeseed oil was identified as favorable feedstock with an availability of 1.3 million tons in 2015. However, it is noticeable that this available potential is in competition with food industry and biodiesel, which is also made from vegetable oils. Animal fats and used cooking oil could be also interesting feedstocks for this process, but their real potential can currently not been foreseen. Nevertheless, it was found that they can amount to 358,974 tons in 2020 and 210,853 in 2010, for animal fats and used cooking oil, respectively. With the availability of rapeseed oil in 2015, almost 1 million ton of HEFA jet fuel could be then produced in Germany. This will cover only 10% of the demand of sustainable jet fuels in 2050 in Germany. Moreover, the potential of rapeseed oil is considering being available for HEFA process, but there is obviously a competition with biodiesel and food industry. The techno-economic assessment presented in this thesis is based on the HEFA production from rapeseed oil. As a result, a net production costs (NPC) of 1.08 €/l (or 1.53 €/kg) and a “rapeseed oil to liquid” efficiency of 94.6% were calculated. These results have to be taken carefully, since the production and pretreatment of vegetable oils are not taking account. The sensitivity analysis shows that rapeseed oil is the most sensitive parameter and the economic results prove that it is also the expensive one. This thesis shows that HEFA process could be competitive with conventional kerosene, if cheaper feedstocks are developed, such as used cooking oil and animal fats. However, the technical potential of HEFA in Germany is very limited and only 10% of the future kerosene demand can theoretically be replaced by HEFA. The application of HEFA in aviation sector has a future only if it is combined with other sustainable jet fuel.