(300h) On a Mathematical Modelling and Optimization Approach for the Systematic Synthesis and Development of Integrated Value Chains for Biorefineries

Kokossis, A. C., National Technical University of Athens
The biorefinery concept addresses the holistic use of biorenewables and is gaining increasing attention with applications that include the production of fuels and chemicals from different resources. The design of product portfolios remains a critical decision that depends on the nature of resources, the processing technologies, the infrastructures installed and the markets available. Energy efficiency and integration across production paths is critical in selecting product portfolios. However, the synthesis of product portfolios accounts for a combinatorial problem of significant complexity as the number of products and feedstocks are large, several alternative technologies are available to choose, and the ways to integrate the processing paths explode in combinatorial manner.

The work highlights a combined use of graph theory and cascade analysis (thermodynamics) to first conceptualize and subsequently formulate the problem using mixed-integer programming technology. Directed graphs are introduced to systematically translate biorefinery value chains into processing networks where thermodynamics is used to define energy containers of integration. The latter is addressed at the process level but, primarily, through patterns of process-to-process integration. The mathematical approach accounts for all available combinations and could accommodate preferences for portfolio profiles (e.g. mix of fuels and chemicals) or particular types of products (e.g. neutraceuticals, polymers). The mathematical approach considers integration for the entire plant each time delivering the product mix to match the minimum (plant) energy or the most profitable production. The research steps are illustrated with small problems but results are presented from three large real-life biorefineries where the approach has been applied to guide developments.