Optimization framework for the simultaneous process synthesis, heat and power integration of a thermochemical hybrid biomass, coal, and natural gas facility

A thermochemical based process superstructure and its mixed-integer nonlinear optimization (MINLP) model are introduced to convert biomass (switchgrass), coal (Illinois #6), and natural gas to liquid (CBGTL) transportation fuels. The MINLP model includes simultaneous heat and power integration utilizing heat engines to recover electricity from the process waste heat. Four case studies are presented to investigate the effect of CO2 sequestration (CCS) and greenhouse gas (GHG) reduction targets on the process topology along with detailed parametric analysis on the role of biomass and electricity prices. Topological similarities for the case studies include selection of solid/vapor-fueled gasifiers and iron-catalyzed Fischer-Tropsch units that facilitate the reverse water–gas-shift reaction. The break-even oil price was found to be $57.16/bbl for CCS with a 50% GHG reduction, $62.65/bbl for CCS with a 100% GHG reduction, $82.68/bbl for no CCS with a 50% GHG reduction, and $91.71 for no CCS with a 100% GHG reduction.