(666g) Total Site Integration As a Synthesis Tool to Select Biomass Valorization Paths and Schedule Multiple-Feedstock Operations
Lignocellulosic biorefineries are based on the exploitation of the three fundamental chemical components: C5 and C6 sugars and lignin. Though products of value chains remain the same with changes in the type of lignocellulosic material â wheat straw, rice, poplar or birch, they all include sugars and lignin â changes appear in process capacities and energy consumption due to seasonal variations in capacities and yields in sugars and lignin for each biomass type. Accordingly, heat interactions and recovery among processes based on the valorization of each component change by switching feedstocks during the year.
The combinatorial process synthesis and integration problem is formulated by the mass balances along value chains (selection of paths) and energy balances at each interval of the proposed transshipment (evaluation of selected paths). The problem also assumes changes in biomass capacities at discrete time periods for each candidate type of biomass. Accordingly, the domain of flowrates along value chains is expanded by the indexes of biomass type and the time period that is applied. Large deviations in common chemicals flows and processes capacities at different periods are not industrially accepted. Likewise, the domain of heat flows in the transshipment model and utilities is also expanded by time and biomass index and limited for logic deviations. The MILP model combines selection of value chain paths with integration in transshipment model to evaluate energy savings at each period and thus, to synthesize the seasonal feedstocks plan and select the processes portfolio that minimize energy cost of the biorefinery site.
A.C. Kokossis, M. Tsakalova, K. Pyrgakis, Design of integrated biorefineries, Computers & Chemical Engineering, 2015, 81, 40â56