Technology analysis of integrated biorefineries through process simulation and hybrid optimization A. Geraili, P. Sharma, J.A. Romagnoli * Chemical Engineering Department, Louisiana State University, Baton Rouge, LA 70803, United States article info Article history: Received 6 January 2014 Received in revised form 29 May 2014 Accepted 31 May 2014 Available online 4 July 2014 Keywords: Process synthesis Hybrid optimization Process integration Renewable energy Lignocellulosic biorefinery abstract This work investigates the design and modeling of fully integrated processes which utilize renewable feedstocks as raw materials by evaluating alternative technology options and possible process in- tegrations to select the optimal configuration according to calculated process yields and economic profit criteria. The analysis is carried out by exploiting the advantages of process simulation and a novel hybrid optimization framework which includes a two layer optimization strategy composed of strategic and operational level decisions. Additionally, an integrated software platform is developed to incorporate experimentally-derived kinetics of complex biological reactions in process simulation. To demonstrate the effectiveness of the proposed approach, an advanced biofuel production facility which has alternative technology choices for each section of the plant is utilized. The results prove the efficiency of the pro- posed approach, and an optimal configuration for a lignocellulosic biorefinery is obtained. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction As the world has recognized the importance of diversifying its energy resource portfolio away from fossil resources and more towards renewable resources such as biomass, there arises a need for developing strategies which can design renewable sustainable value chains that can be scaled up efficiently and provide tangible net environmental benefits from energy utilization [11,13,23,24,37]. Biobased fuels and chemicals can be derived from any form of biomass such as plants or organic wastes. After a boom in the U.S. corn-based ethanol (first-generation biofuel) in the early part of the 21st century [48], the interest has gradually shifted towards more viable renewable resources such as lignocellulosic feedstocks since the viability and sustainability of first generation biofuels are un- certain and questionable [33,43]. Negative impacts of first genera- tion biofuels might lead to the risk of deforestation by overuse of lands, environmental risks by the widespread use of fertilizers and pesticides, and decreasing food security by the risk of creating a competition between food and fuel production. Cellulosic ethanol is an example of such alternative fuel which is considered as a second-generation biofuel and is derived from cellulose instead of starch. The fuels and chemicals produced from lignocellulosic feedstocks are extremely attractive owing to the fact that the raw materials can be composed of “left-over” wastes of food crops and forest harvests that do not interfere with the human food chain. It also can provide new income and employment op- portunities in rural areas. Further, due to the large variety of lignocellulosic materials and their abundance, these types of pro- duced fuels and chemicals (second-generation) can overcome the challenge of limited feedstock availability that first generation biorefineries have to contend with. There are two main conversion platforms in a biorefinery pro- cess: (1) the biological conversion pathways based on fermenta- tion, and (2) thermo-chemical conversion pathways based on heat- based technologies such as gasification and pyrolysis. The main difference between these two conversion mechanisms is the pri- mary catalysis system [9]. In biological conversion pathways, bio- catalysts such as enzymes and microorganisms are utilized. However, in thermochemical production routes, heat and physical catalysts are utilized to convert biomass to biofuels and chemicals. By considering the fact that conversion technologies in second generation biorefineries are relatively immature and recalcitrance of lignocellulosic materials can cause major barriers to the economical production of biofuels [6,18], process synthesis by analyzing alter- native technology options, considering possible process integrations, and developing mathematical optimization methodologies can be useful for designing more cost-effective configurations with improved techno-economic and environmental characteristics. Many frameworks have been proposed for designing technological flowsheets with improved performance. Some research studies * Corresponding author. Louisiana State University, Chemical Engineering Department, 220 ChE Building, Baton Rouge, LA 70803, United States. Tel.: þ1 225 5781377. E-mail address: jose@lsu.edu (J.A. Romagnoli). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy http://dx.doi.org/10.1016/j.energy.2014.05.114 0360-5442/© 2014 Elsevier Ltd. All rights reserved. Energy 73 (2014) 145e159