Exploration of alternative reactor configurations for the Fischer-Tropsch (FT) reaction via direct hydrogenation of carbon dioxide

Background

Converting CO₂ into various fuels (e.g., light hydrocarbons, gasoline, jet fuel, diesel) through the Fischer-Tropsch (FT) reaction is a promising option in a future decarbonized economy.

Method

Four scenarios characterized by different chain propagation probabilities (α) described by the Anderson-Schultz-Flory (ASF) distribution were developed, corresponding to the production of light hydrocarbons (α=0.3), gasoline (α=0.65), jet fuel (α=0.75), and diesel (α=0.85). Deviations from the standard ASF distribution for lower carbon numbers at high ɑ values were considered. For each scenario, alternative configurations utilizing different reactor structural parameters, employing various heat transfer methods, were investigated through mathematical modeling. Multi-objective optimization, aiming to maximize conversion and minimizing costs, was conducted to determine the optimal design and operating conditions.

Significant Findings

Overall, compared to single-stage configurations, dual-stage configurations offer opportunities for cost reduction and process intensification across all four scenarios. When utilizing counter-current heat exchange, higher conversion can be achieved at a lower cost with moderate conversion levels. In contrast, configurations with co-current heat exchange tend to enhance conversion by extending the reactor length once conversion exceeds 30 %. Furthermore, when using a dual-stage configuration to produce longer hydrocarbons, it is not appropriate to produce shorter hydrocarbons as intermediates that exit from the first reactor.