Fischer Tropsch Catalyst Structures & Process Design for JP-5 Fuel Integrated with MFEC
Dokun, Tunde B. A.
Type of Degreethesis
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Modern societies are seeking new sources and corresponding technology as traditional fossil fuels are becoming more difficult to access because of their remote locations. A potentially attractive solution is to convert natural gas to a synthesis gas and then synthesize longer-chain hydrocarbons through a Fischer-Tropsch (FTS) reaction. However, conventional FTS reactors are faced with the challenge of heat removal due to the reaction being highly exothermic. A design framework has been established, which incorporates functionality of the FTS catalyst and its impact on the FTS balance of plant (BOP). Process simulation tools are used in an iterative design to develop a unique plant optimized for the production of JP-5 and other value-added hydrocarbons under process constraints and size limitations. The focus of this work is to evaluate the effects of utilizing a micro-fibrous entrapped catalyst (MFEC) on FTS plant scalability, physical plant design, and critical front-end capital cost in order to design a mobilized Fischer-Tropsch process for the purpose of producing JP-5. The product distribution of the FTS reaction is given by the Anderson-Schulz-Flory distribution. MFEC is comprised of a small grain catalyst entrapped within a sinter-locked network of a metal. With the use of this metal fiber network, we are able to increase the effective thermal conductivity within the reactor by about 90%, and reduce the temperature rise within the reactor as compared to a conventional Packed bed reactor. MFEC are readily manufactured and provide high intra-particle and mass transport properties. The temperature uniformity within the reactor will ensure and enhance JP-5 selectivity. Using an implicit finite integrating scheme, we are able to determine the reactor temperature profile by modeling a plug flow reactor which includes the energy balances on the gas phase. The catalyst temperature will be assumed to be uniform inside the catalyst particles, so all heat of reaction is generated inside the catalyst particles. Moreover, with AspenTM integrated simulation, we are able to simulate an overall GTL plant capable of producing 500 bpd of JP-5. The simulation takes into account a vapor-liquid relationship of the different FTS hydrocarbon products with the intrinsic kinetics of the FTS and a water gas shift reaction for a promoted Iron catalyst, Fe/Cu/K as a basis of development. The application of applied mathematics and numerical methods in solving the sets of differential equations is the key to fully understanding the temperature profile. By effectively designing an FTS reactor that has an effective heat transfer mechanism due to a high effective intra-bed thermal conductivity, a better control on intra-bed hot spots and product selectivity is achieved. A High selectivity towards JP-5 will be observed and thus, we are able to reduce the balance of plant (BOP) requirements for the FTS reactor and downstream operations.