Conceptual Design of an Autonomous Once-through Gas-to- Liquid Process with Microchannel Fischer-Tropsch Reactors

Converting remote natural gas to liquid fuel is one possible solution to the problem of transporting remote gas to the energy market. However, the high investment cost of gas-to-liquid (GTL) plants prevents large scale exploitation of remote gas reserves. A lean GTL is suggested based on an autothermal reformer with enriched air as oxidant and a once-through Fischer-Tropsch synthesis. In order to maximize the syngas conversion and the production of heavy hydrocarbons, a staged microchannel reactor path with distributed hydrogen feed and product withdraw is proposed. The hydrogen is produced by steam methane reforming in a heat exchange reformer (gas heated reformer). A verified kinetic model for the Fischer-Tropsch reactor is used. This kinetic model was fitted to kinetic data of a 40 %CO/Al2O3 catalyst which was used in a microchannel reactor. A new chain propagation model was also fitted to the data. The new kinetic and rate propagation models are believed to be specifically suitable for microchannel reactors. The chain propagation model yields high C5+ selectivities. The process is autonomous in the sense that it is self-sufficient with power and water.