(249a) Coal and Biomass to Liquid Transportation Fuels: Process Synthesis and Global Optimization Strategies

The volatility of the global oil market, coupled with increasing levels of greenhouse gas (GHG) emissions, has sparked the search for alternative methods for the production of liquid transportation fuels from domestically available carbon-based resources. The United States has three feedstocks available to gradually replace petroleum as its primary energy source, namely: coal, biomass, and natural gas. The major contributions to the production of liquid fuels from these three feedstocks have been highlighted in a recent review [1]. Hybrid energy systems utilizing coal and biomass have been the center of interest in recent years. Coal has a lower delivered cost than biomass, but conventional coal-to-liquids (CTL) refineries result in almost twice the life-cycle GHG emissions of a petroleum-based plant. Biomass, however, has the ability to reduce greenhouse gas emissions through the capture of CO2 during photosynthesis. The economic and environmental benefits that both these feedstocks offer can be exploited by investigating coal-and-biomass-to-liquid fuels (CBTL) systems.

Using an optimization-based process synthesis framework, the thermochemical conversion of coal and biomass will be presented [2]. Synthesis gas (syngas) will be generated via gasification of the biomass and coal feedstocks through separate gasification units. The syngas can then be directed to either a dedicated water-gas-shift reactor or passed directly to the scrubbing system. Hydrocarbon production will proceed through either Fischer-Tropsch synthesis or methanol formation. The Fischer-Tropsch hydrocarbons can be upgraded over a ZSM-5 reactor or through a series of treatment units that will produce distillate and gasoline-range products. The methanol can be passed to the methanol-to-gasoline (MTG) process or to the methanol-to-olefins/olefins-to-gasoline-and-distillate (MTO/MOGD) processes. Simultaneous heat and power integration is included in the model to convert waste heat into electricity. The optimal process topology that can produce gasoline, diesel, and kerosene at the lowest cost is determined using rigorous deterministic global optimization and process synthesis strategies [3-13].

This study presents a baseline so that a fair comparison between different process alternatives can be made. Multiple case studies are presented to investigate the effect of plant capacity and product distribution on the overall cost of the refinery, the process topology, the total plant cost, and the break-even oil price. The results demonstrate that coal and biomass refineries can become economically competitive with petroleum-based processes while simultaneously reducing life-cycle greenhouse gas emissions.

[1] Floudas, C. A.; Elia, J. A.; Baliban, R. C. Hybrid and single feedstock energy processes for liquid transportation fuels: A critical review. Computers & Chemical Engineering 2012, 41 (6), 24-51.
[2] Niziolek, A. M.; Onel, O.; Elia, J. A.; Baliban, R. C.; Xiao, X.; Floudas, C. A. Coal and
Biomass to Liquid Transportation Fuels: Process Synthesis and Global Optimization Strategies. Industrial & Engineering Chemistry Research 2014 DOI: 10.1021/ie500505h.
[3] Baliban, R. C., Elia, J. A., Floudas, C. A. Toward novel biomass, coal, and natural gas processes for satisfying current transportation fuel demands, 1: Process alternatives, gasification modeling, process simulation, and economic analysis. Industrial & Engineering Chemistry Research 2010, 49, 7343-7370.
[4] Elia, J. A., Baliban, R. C., Floudas, C. A. Toward novel biomass, coal, and natural gas processes for satisfying current transportation fuel demands, 2: Simultaneous heat and power integration. Industrial & Engineering Chemistry Research 2010, 49, 7371-7388.
[5] Baliban, R. C., Elia, J. A., Floudas, C. A. Optimization framework for the simultaneous process synthesis, heat and power integration of a thermochemical hybrid biomass, coal, and natural gas facility. Comp. Chem. Eng. 2011, 35, 1647-1690.
[6] Baliban, R. C., Elia, J. A., Floudas, C. A. Simultaneous process synthesis, heat, power, and water integration of thermochemical hybrid biomass, coal, and natural gas facilities. Comp. Chem. Eng. 2012, 37, 297-327.
[7] Baliban, R. C., Elia, J. A., Misener, R., Floudas, C. A. Global Optimization of a MINLP Process Synthesis Model for Thermochemical Based Conversion of Hybrid Coal, Biomass, and Natural Gas to Liquid Fuels. Comp. Chem. Eng. 2012, 42, 64-86. 
[8] Baliban, R. C., Elia, J. A., Weekman, V., Floudas, C. A. Process Synthesis of Hybrid Coal, Biomass, and Natural Gas to Liquids via Fischer-Tropsch Synthesis, ZSM-5 Catalytic Conversion, Methanol Synthesis, Methanol-to-Gasoline, and Methanol-to-Olefins/Distillate Technologies. Comp. Chem. Eng. 2012, 47 (12), 29-56.
[9] Baliban, R. C.; Elia, J. A.; Floudas, C. A. Biomass to liquid transportation fuels (BTL) systems: process synthesis and global optimization framework. Energy Environ. Sci. 2013, 6 (1), 267-287.
[10] Baliban, R. C.; Elia, J. A.; Floudas, C. A. Novel Natural Gas to Liquids Processes: Process Synthesis and Global Optimization Strategies. AIChE Journal 2013, 59 (2), 505-531.
[11] Baliban, R. C.; Elia, J. A.; Floudas, C. A. Biomass and Natural Gas to Liquid Transportation Fuels: Process Synthesis, Global Optimization, and Topology Analysis. Industrial & Engineering Chemistry Research 2013, 52 (9), 3381-3406.
[12] Baliban, R. C.; Elia, J. A.; Floudas, C. A.; Gurau, B.; Weingarten, M. B.; Klotz, S. D. Hardwood Biomass to Gasoline, Diesel, and Jet Fuel: 1. Process Synthesis and Global Optimization of a Thermochemical Refinery. Energy & Fuels 2013, 27 (8), 4302-4324.
[13] Baliban, R. C.; Elia, J. A.; Floudas, C. A.; Xiao, X.; Zhang, Z.; Li, J.; Cao, H.; Ma, J.; Qiao, Y.; Hu, X. Thermochemical Conversion of Duckweed Biomass to Gasoline, Diesel, and Jet Fuel: Process Synthesis and Global Optimization. Industrial & Engineering Chemistry Research 2013, 52 (33), 11436-11450.