Optimization-based Process Screening of Biorefinery Pathways at Early Design Stage

In order to increase sustainability of chemical processes, a raw material change from conventional to renewable feedstocks is the key. This opens up numerous novel process concepts. A detailed conceptual design of all of these different pathways is expensive and time-consuming, since the mandatory simulations depend on pre-specified design decisions and commercial simulation software lack robustness. Hence, screening methodologies are required for an initial assessment of the processes. Existing screening methods are restricted to reaction or process design data known in literature, such that the integration of novel pathways requires simulation studies. This is impeded by limited data availability and the lack of profound property models.

Process Network Flux Analysis is introduced as an optimization-based screening methodology to accelerate process development and improvement for existing and novel processes. The method systematically integrates reaction data with the selection of separation processes, the feasibility and efficiency of which are evaluated using thermodynamically-sound separation models. Based on mass and energy balances, the pathways are analyzed according to their economic efficiency and sustainability. Furthermore, the method allows for an initial heat integration potential analysis, considers the influence of the biomass supply chain and identifies suitable product portfolios based on a pragmatic market model. Thus, the method is applicable for single or multiple products as well as for mixtures.

The accuracy of the results is analyzed by a comparison with literature data, Reaction Network Flux Analysis and a conceptual design study. For a complex case study of fuel production from biomass, the applicability of the method is demonstrated. The production of ethanol is most promising, followed by iso-butanol. A profitable production is not achieved, in particular, when the biomass supply chain is included. Profitability is only obtained by a co-production of chemicals. Finally, key improvement factors for future biorefineries are derived. For this purpose, the actual and theoretical potential of selective biotechnological conversion are discussed."