Design of dividing wall columns for butanol recovery in a thermochemical biomass to butanol process

• DWCs for biobutanol recovery from a thermochemical biobutanol process are assessed.
• A design technique using shortcut methods and derivative-free optimization is shown.
• Kaibel DWC yields good energy and cost savings over conventional distillation columns.

In this work, ternary and quaternary dividing wall column (DWC) configurations for the separation of a multicomponent feed stream from a novel thermochemical lignocellulosic biomass to butanol process are designed, modeled and assessed. The goal is to separate the feed into four major products, with a key product being a biobutanol rich stream. Due to the complexity of DWC models, a shortcut modeling approach based on the minimum energy mountain method (also called the “Vmin diagram method”) is used to determine good initial values for the decision variables for the rigorous simulation of the DWC configurations. Furthermore, each DWC configuration is optimized to minimize the total annualized cost with the use of a derivative free algorithm coupled with a process simulator. The results show that the quaternary DWC configuration achieves up to 31% energy savings, and 15% capital savings in comparison to a conventional distillation sequence, and is thus a better option for implementation in the biofuel process.