(55b) Novel Municipal Solid Waste to Liquid Transportation Fuels Processes: Mathematical Model of MSW Gasification, Process Synthesis, and Global Optimization Strategies

Authors: 
Onel, O., Princeton University
Niziolek, A. M., Princeton University
Hasan, M. M. F., Princeton University
Floudas, C. A., Princeton University

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. With growing concerns over expensive crude oil prices and increased scrutiny over high levels of greenhouse gas (GHG) emissions, the U.S. transportation sector faces major challenges that must be addressed through the investigation of novel processes to produce liquid fuels. Three feedstocks that have been touted as alternatives to petroleum include coal, biomass, and natural gas. A recent review has illustrated the key contributions in the production of liquid fuels from single and hybrid combinations of these three feedstocks [1]. This study, however, focuses on a fourth type of feedstock: municipal solid waste (MSW).

The United States generates over 250 million tons of MSW each year [2]. Its competitive energy content, as well as its negative cost, make it an attractive precursor to liquid fuels. Facilities normally receive a tipping fee, which varies between $24-$70/ton in the U.S., for the disposal of municipal solid waste [3]. Thus, we seek to determine whether the production of liquid transportation fuels from municipal solid waste is economically viable.

A stoichiometric municipal solid waste gasifier model [4] that was able to predict the effluent to 8.75% when compared with experimental data is incorporated in a thermochemical based process synthesis superstructure to produce liquid fuels from multiple conversion pathways [5-16]. Municipal solid waste is first processed in a refuse derived fuel (RDF) facility that converts the MSW into a higher-calorific fuel (RDF). The RDF is then gasified and the synthesis gas (syngas) effluent is sent to either the scrubbing system or to a dedicated water-gas-shift reactor. Syngas is then directed to either the Fischer-Tropsch reactor section or to a methanol synthesis reactor. The Fischer-Tropsch hydrocarbons are upgraded to fuel-grade products, while the methanol is converted to either gasoline or olefins. The olefins are subsequently converted into gasoline and distillate. Simultaneous heat and power integration will ensure that waste heat is converted into electricity using a series of heat engines.

The optimal plant topology that can produce liquids at the lowest possible cost is determined using a rigorous deterministic global optimization branch-and-bound strategy. The effect of plant capacity and product distribution on the optimal process topology is investigated. The overall cost of the refinery, the total plant cost, and the break-even oil price will also be illustrated. Additionally, the effect that the tipping fee has on the overall cost of liquid fuels is investigated parametrically.

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Biomass to Liquid Transportation Fuels: Process Synthesis and Global Optimization Strategies. Industrial & Engineering Chemistry Research 2014 DOI: 10.1021/ie500505h.