Life Cycle Optimization for Sustainable Design and Operations of Hydrocarbon Biorefinery Via Fast Pyrolysis, Hydrotreating and Hydrocracking

Life cycle optimization for sustainable design and operations of hydrocarbon biorefinery via fast pyrolysis, hydrotreating and hydrocracking

Berhane H. Gebreslassie, Maxim Slivinsky, Belinda Wang, Fengqi You*

Submitted to session 23B20 Biofuels Production: Design, Simulation, and Economic Analysis

Abstract

As world energy demand grows despite finite fossil fuel reserves, the development of new sources of energy is becoming ever more critical, especially with growing concerns about climate change.  Biofuels provide a promising alternative to fossil fuels for transportation due to their compatibility with current infrastructure.  Hydrocarbon biofuels can be used in gasoline and diesel engines, providing vehicle performance similar to that of fossil fuels.  They also can use the current fuel distribution and utilization infrastructure, including pipelines and pumping stations.  The advantage of biofuels lays in their sustainability and lower life cycle greenhouse gas (GHG) emissions than conventional fuels [1].  A larger share of a nation's energy portfolio from biomass has the added benefit of increasing energy independence.  Fast pyrolysis is a high temperature thermochemical conversion in the absence of oxygen; it can potentially produce biofuels at lower production cost and environmental impact than other biomass conversion pathways.  This work addresses the design and optimization of biomass conversion to biofuels through fast pyrolysis under two objectives: maximizing net present value (NPV) and minimizing project global warming potential (GWP) [2].  This work presents the first mathematical programming model for rigorous optimization of a hydrocarbon bio-refinery via fast pyrolysis, hydrotreating, and hydrocracking.

In this work a multi-objective nonlinear programming model (NLP) is used for the optimal design and operation of hydrocarbon bio-refinery using hybrid poplar as the feedstock.  This NLP is solved using the ε-constraint method, using varying ε values to determine Pareto-optimal solutions given the two objectives [3].  The economic objective takes into account feedstock and utilities costs, selling price of biofuels, demand for products, and processing limits [4, 5, 6].  The environmental objective uses life cycle analysis (LCA), considering gate-to-gate environmental impact analysis of the bio-refinery.  GWP is calculated using the 100 year timeframe per the Kyoto Protocol [7]. 

The hydrocarbon bio-refinery is composed of the following units: pyrolysis, hydrotreating, separation and hydrocracking, and steam reforming for hydrogen production [8, 9].  Gallon of gasoline equivalent (GGE) is the functional unit for the bio-refinery products, namely naphtha and diesel.  The optimization results show unit production costs to be $2.31/GGE for the maximum NPV solution and $3.67/GGE for the minimum GWP solution, and the resulting Pareto curve shows the tradeoffs between the two objectives.  

References

[1]        Hsu, D. D. (2012), “Life cycle assessment of gasoline and diesel produced via fast pyrolysis and hydroprocessing,” Biomass and Bioenergy, Vol. 45, Pages 41–47

[2]        Gebreslassie, B. H., Slivinsky, M., Wang, B., & You, F. (2013). Life Cycle Optimization for Sustainable Design and Operations of Hydrocarbon Biorefinery via Fast Pyrolysis, Hydrotreating and Hydrocracking. Computers & Chemical Engineering, 50, 71-91

[3]        Gebreslassie, B. H., Yao, Y., and You, F. (2012) "Design under uncertainty of hydrocarbon biorefinery supply chains: Multiobjective stochastic programming models, decomposition algorithm, and a Comparison between CVaR and downside risk," AIChE Journal, vol. 58, pp. 2155-2179.

[4]        Wang, B., Gebreslassie, B. H., & You, F. (2013). Sustainable Design and Synthesis of Hydrocarbon Biorefinery via Gasification Pathway: Integrated Life Cycle Assessment and Technoeconomic Analysis with Multiobjective Superstructure Optimization. Computers & Chemical Engineering, 52, 55–76

[5]        Gebreslassie, B. H., Waymire, R., & You, F. (2013). Sustainable Design and Synthesis of Algae-Based Biorefinery for Simultaneous Hydrocarbon Biofuel Production and Carbon Sequestration AIChE Journal, 59, 1599–1621

[6]        You, F., & Wang, B. (2011). Life Cycle Optimization of Biomass-to-Liquids Supply Chains with Distributed-Centralized Processing Networks. Industrial & Engineering Chemistry Research, 50, 10102–10127

[7]        Gian-Kasper, P., Stocker, T., Midgley, P., & Tignor, M. (2009). IPCC expert meeting on

the science of alternative Q5 metrics.

[8]        Jones, S. B., Valkenburg, C., Holladay, J. E., Stevens, D. J., Walton, C. W., Kinchin, C.,

et al. (2007). "Production of gasoline and diesel from biomass via fast pyrolysis,

hydrotreating and hydrocracking: A design case," In DE-AC05-76RL01830: Pacific

Northwest National Laboratory and National Renewable Energy Laboratory.

[9]        Wright, M. M., Daugaard, D. E., Satrio, J. A., Brown, R. C. (2010) “Techno-economic analysis of biomass fast pyrolysis to transportation fuels,” Fuel, Vol. 89, Supplement 1, 1, Pages S2–S10.

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* Corresponding author. Email: you@northwestern.edu