Commissioning and operation of a Fischer-Tropsch pilot unit based on SBCR technology

Abstract

Biomass-based Fischer-Tropsch (FT) synthesis offers the possibility to produce sustainable biofuels and chemicals from synthesis gas. This thermochemical process involves catalytic polymerisation reactions, where the synthesis gas components CO and H2 react to form a product primarily composed of hydrocarbons. Products that can be produced within an FT plant are diesel, gasoline and waxes. At the research site of Bioenergy and Sustainable Technologies GmbH (BEST) in Simmeringer Haide, a 300 kWth FT pilot plant based on the slurry bubble column reactor (SBCR) technology was commissioned to produce second-generation biofuels. The SBCR design offers improved heat and mass transfer, enhanced catalyst performance and high feedstock flexibility. A commercial cobalt-based catalyst was chosen for the low-temperature Fischer-Tropsch (LTFT) synthesis. The synthesis gas was generated in the 1 MW dual fluidised bed gasification unit using woody biomass. The aim of this thesis is the scientific monitoring of the first commissioning of the FT pilot plant and the evaluation of the first continuous operation. Despite some start-up difficulties, the plant was in operation for 144 hours, and 357 kg of FT product, including the aqueous phase, were produced. The FT plant was equipped with suitable measurement devices to monitor and control the operation. Therefore, the carbon monoxide conversion, methane selectivity, carbon chain distribution, as well as the temperature profile of the reactor could be evaluated.The results indicate a per-pass carbon monoxide conversion above 80% and a methane selectivity between 40-60%. A comparison with previously conducted trials was performed to investigate possible factors influencing the process performance. The first commissioning of the FT SBCR pilot plant showed promising results, and further investigations are planned to find optimum process conditions for the reactor.