(120b) Simulation, Optimization and Costing of a Fully Integrated Multi-Product Biorefinery

                                                                              Aryan Geraili Nejadfomeshi, Paritosh Sharma, J.A. Romagnoli                                                 

                                                                                       Louisiana State University, Baton Rouge, LA, U.S.A

         Over the last century, the energy consumption has increased progressively owing to the growing demand by the industrialized societies and the rising world population. The current global state of energy supply is highly dependent on fossil fuels. Yet, there are varieties of alternative methods to produce energy from renewable sources. In this project, we study the development, optimization and costing of a fully integrated multiproduct biomass refinery to convert agricultural residue to value-added chemicals and fuels. 

        Within the framework of this project, the present study includes the process simulation, the study of the costing equipment at different scales, and strategic design of supply chain and processing capacity under uncertain market conditions. In this presentation, the focus is on the simulation and optimization of a multiproduct biomass refinery by means of different technology choices and process superstructures.

      For our case study, the prospective product portfolio consists of ethanol, butanol, lactic acid and succinic acid. A fermentation platform is used to convert biomass to products. The potential pretreatment technologies which are investigated include steam hydrolysis, dilute acid (DA), ammonia fiber explosion (AFEX). Fermentation configurations that are investigated include simultaneous hydrolysis with either (1) separate C5 and C6 fermentation, or (2) co-fermentation of C5 and C6 sugars. A multi-period deterministic process superstructure optimization model is used to arrive at the optimal product and technology configuration. AFEX and Co-fermentation are found to be the optimal technologies based on the process yield and capital and operating cost. The optimal product mixture includes ethanol and succinic acid. Once the optimization is performed for this process, the simulation of the optimal process configuration is carried out on different capacities.

     Additionally, waste management technologies are investigated and cost is evaluated through simulation. These technologies are fed back into superstructure optimization model to determine the economic impact of investment in waste mitigation on the biorefinery. Three waste mitigation technologies are simulated; (1) Carbon capture and sequestration of fermentation gas (from ethanol fermentation) into succinic acid fermentation tanks (to improve succinic acid yields), (2) Carbon capture, purification, and transport from emitted flue gas (from power generation) for enhanced oil recovery markets, and (3) Anaerobic and Aerobic digesters to mitigate solid effluents from the production processes. The fermentation gas is essentially pure carbon dioxide which doesn’t require additional purification and improves directly the bottom line of the biorefinery (reduction in raw material costs of CO2). The flue gas is a mixture of gases and impurities which require further scrubbing and compression before commercial usage in enhanced oil recovery (although providing a potentially more lucrative market). Finally, the digesters provide biogas which can be used to improve power generation capabilities of the plant. After doing the superstructure optimization, it was found that anaerobic digestion and fermentation gas sequestration can be incorporated profitably with the production processes.

Keywords:  Multi-Product Biorefinery, Process Optimization, Waste Mitigation, Carbon Capturing and Sequestration