(639e) Systematic Design and Synthesis of Integrated Multi-Product Biorefinery Processes

Authors: 
Yuan, Z., Auburn University
Lousada, B., Auburn University
Li, P., Auburn University
Eden, M. R., Auburn University

Depletion of petroleum sources combined with fluctuations in the global oil market, and increasingly strict environmental requirements prompt the need to discover alternative fuel/chemical-production technologies. In this presentation we systematically design and synthesize a cost-effective and environmentally-benign multi-product biorefinery process. Besides the production of traditional liquid transportation fuels, propylene production is also included as a platform chemical that has a gap between demand and supply. In the designed conversion process, biomass (hybrid poplar) is firstly directly or indirectly gasified to syngas which, after treatment and cleanup, is subsequently converted to liquid hydrocarbons and methanol through Fischer-Tropsch (FT) synthesis and methanol synthesis, respectively. Gasoline, kerosene, and diesel are obtained from upgrading of the FT raw liquids via ZSM-5 [1] and hydro-processing approaches, while propylene is obtained from the “on-purpose” methanol-to-propylene (MTP) process. Any light gas products are recycled and reformed to make additional syngas to improve the overall carbon conversion. Finally, all generated CO2 is converted to produce acetic acid.

We initially develop a biorefinery superstructure, which considers multiple alternatives for certain conversion sections, and formulate a mixed integer nonlinear programming (MINLP) model. Global power, heat, and water networks [2-4] are contained within the formulated framework to minimize the utility requirements and wastewater discharge. Data-driven techniques [5,6] are used to generate simple surrogate models with high accuracies for the indirect/direct heated-gasifier to reduce the computational complexity. The bilinear, trilinear, quadrilinear, and concave terms are reformulated for enhancing the MINLP model to be solved to global optimality [7,8]. Through solving the optimization model, we present parametric/structural analyses to better elucidate the optimal topology under various scenarios with respects to volatile feedstock/product prices, market requirements as well as constraints on waste emissions. We then check the relationship between process profit and ratio of syngas towards the FT and methanol synthesis units, respectively. The total process profit, when the produced CO2 is converted to acetic acid vs. when it is sequestrated, is also discussed.

References:

[1]. Bechtel. Baseline design/economics for advanced Fischer-Tropsch technology. Contract No. DE-AC22-91PC90027. 1992.

[2]. Duran MA, Grossmann IE. Simultaneous optimization and heat integration of chemical processes. AIChE J. 1986; 32: 123-138.

[3]. Bruno JC, Fernandez F, Castells F, Grossmann IE. A rigorous MINLP model for the optimal synthesis and operation of utility plants. Trasn IChemE, 1998; 76: 246-258.

[4]. Ahmetovic E, Grossmann IE. Global superstructure optimization for the design of integrated process networks. AIChE J. 2011; 57: 434-457.

[5]. Schmidt M, Lipson H. Distilling free-form natural laws from experimental data. Science. 2009; 324: 81-85.

[6]. Cozad A, Sahinidis NV, Miller DC. A combined first-principles and data-driven approach to model building. Comput Chem Eng. 2015; 73: 116-127.

[7]. Gounaris CE, Misener R, Floudas CA. Computational comparison of piecewise-linear relaxations for pooling problems. Ind. Eng. Chem. Res. 2009; 48: 5742-5766. 

[8]. Cafieri S, Lee J, Liberti L. On convex relaxations of quadrilinear terms. J Glob Optim. 2010; 47: 661-685.