The amount of municipal solid waste (MSW) generated in the United States has increased from 208.3 million tons in 1990 to over 250 million tons in 2011.1 The majority (53.6%) of MSW in the U.S. was discarded in landfills in 2011, while a third (34.7%) was recycled, and the balance (11.7%) was combusted to recovery energy.1 As the world population continues to grow and the amount of MSW produced gradually increases, developing novel routes for the utilization of MSW becomes a matter of great importance. To address this concern, we investigate novel processes for the production of liquid fuels and high-value chemicals, such as aromatics and olefins, from municipal solid waste.
The competitive energy content of MSW, as well as its negative cost, make it an attractive precursor to high value products. Facilities normally receive a tipping fee, which varies between $24-$70/ton in the U.S., for the disposal of municipal solid waste.2 In our previous studies, we developed the first novel stoichiometric municipal solid waste gasifier model that was able to predict the effluent to 8.75% when compared with experimental data.3 We have also incorporated it in a thermochemical based process synthesis superstructure to produce liquid fuels from multiple conversion pathways and showed that the break-even oil price for a waste-to-liquids facility can become as low as $47 per barrel.4 In this study, we utilize a superstructure-based approach to determine the economic viability of producing liquids, aromatics, and olefins from MSW.5-11
Olefins and aromatics are valuable petrochemical products and in high demand. In 2007, the worldwide consumption of ethylene was 115 million tons and the global demand of propylene was 73.5 million tons.12 Between 2005 and 2008, the global demand for benzene, para-xylene, ortho-xylene, and meta-xylene was approximately 40, 26, 6, and 0.4 million metric tons per year, respectively.12Additionally, the United States consumes over 18 million barrels of petroleum-based products per day, with the transportation sector representing the majority (nearly 70%) of this consumption. Thus, a refinery utilizing municipal solid waste has the potential to penetrate an extremely large market.
The optimal plant topology that can produce high-value chemicals and liquid fuels at the highest possible profit is determined using a rigorous deterministic global optimization branch-and-bound algorithm within a process synthesis superstructure. Several commercial olefins and aromatics production, upgrading, and separation technologies are included. Simultaneous heat and power integration will ensure that waste heat is converted into electricity using a series of heat engines. The effect of plant capacity and product distribution on the optimal process topology is investigated. The overall profit of the refinery and the total plant cost will be illustrated. Additionally, the effect that the tipping fee has on the overall profit of liquid fuels, aromatics, and olefins production is investigated parametrically.
1. EPA, Municipal Solid Waste Generation, Recycling and Disposal in the United States: Facts and Figures for 2011. Document Number: EPA530-R-13-001, http://www.epa.gov/osw/nonhaz/municipal/pubs, 2013.
2. Valkenburg, C.; Walton, C.; Thompson, B.; Gerber, M.; Jones, S.; Stevens, D. Municipal solid waste (MSW) to liquid fuels synthesis, Volume 1: Availability of Feedstock and Technolog. Richland, WA: Pacific Northwest National Laboratory 2009.
3. Onel, O.; Niziolek, A. M.; Hasan, M.; Floudas, C. A. Municipal solid waste to liquid transportation fuels–Part I: Mathematical modeling of a municipal solid waste gasifier. Computers & Chemical Engineering 2014, 71, 636-647.
4. Niziolek, A. M.; Onel, O.; Hasan, M.; Floudas, C. A. Municipal solid waste to liquid transportation fuels–Part II: Process synthesis and global optimization strategies. Computers & Chemical Engineering 2015, 74 (0), 184-203.
5. Onel, O.; Niziolek, A. M.; Elia, J. A.; Baliban, R. C.; Floudas, C. A. Biomass and natural gas to liquid transportation fuels and olefins (BGTL+C2_C4): Process Synthesis and Global Optimization. Industrial & Engineering Chemistry Research 2014, 54, 359-385.
6. Niziolek, A. M.; Onel, O.; Elia, J. A.; Baliban R. C.; Floudas, C. A. Coproduction of Liquid Transportation Fuels and C6_C8 Aromatics from Biomass and Natural Gas. AIChE Journal 2015, 61, 831-856.
7. 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.
8. 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.
9. 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.
 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.
 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 , 53, 17002-17025.
 de Klerk, A. Fischer-Tropsch Refining; Wiley-VCH Verlag & Co. KgaA: Weinheim 2011
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