(583a) A Reactive Distillation Optimization Model for Low- and High-Temperature Fischer–Tropsch Syntheses for Multiphase Product Recovery

Liquid fuels and chemicals are predominantly produced from crude oil. The abundance of shale gas has attracted attention for alternatives to be sought since natural or shale gas can be converted to the same liquid fuels and chemicals through integrated gas-to-liquid (GTL) processes. Biomass and carbonaceous wastes as well can also be converted to liquid fuels and chemicals through biomass-to-liquids and waste-to-liquids processes respectively. However, natural/shale gas is the most hydrogen-rich carbon source and can provide the most carbon-efficient route to fuels.

GTL processes require high capital cost but the main detractor of widespread adoption is investment risk linked to feed and products price volatilities. The decision to build a gas-to-liquid plant has to be based on the perceived future prices of oil and gas; and the prices of specialty chemicals produced from downstream processes. Therefore, robust technology that can offer product flexibility in response price volatilities is desirable to mitigate the investment risk.

Process intensification where syngas conversion in multiple reaction zones and product separation are combined in one unit can lead to smaller overall plants with lower capital and running costs. Consequently, we have developed an equation-oriented framework for optimal synthesis of integrated reactive distillation (RD) systems for FT processes in GAMS in which the phase equilibrium is given by a cubic equation of state, the reaction rate expressions are expressed in terms of fugacities, and the product selectivity of catalysts are based on the Anderson–Schulz–Flory distribution and experimental data. Comparing the RD for FT synthesis against conventional slurry reactors, provided results show that RD has a potential edge in industrial processes.

To explore the potential of producing a predominantly wax product on a low-temperature FT process, we are expanding the FT-RD optimization model to optimize tray numbers, feed tray location and catalyst loading on trays. We are also implementing the FT-RD optimization model within the PyOMO optimization framework. To produce a high gasoline fraction, light olefins, and some oxygenates (mainly alcohols) on a high-temperature FT process, we are developing a more detailed kinetic model to account for the various products.