Process Simulation and Techno-Economic Evaluation of Alternative Biorefinery Scenarios

biorefinery is a complex processing facility that uses sustainably produced biomass as feedstock to generate biofuels and chemical products using a wide variety of alternative conversion pathways. The alternative conversion pathways can be generally classified as either biochemical or thermochemical conversion. A biorefinery is commonly based on a core biomass conversion technology (pretreatment, hydrolysis, pyrolysis, etc.) followed by secondary processing stages that determine the specific product, and its recovery.;In this study, techno-economic analysis of several different lignocellulosic biomass conversion pathways have been performed. First, a novel biochemical conversion, which used electron beam and steam explosion pretreatments for ethanol production was evaluated. This evaluation include both laboratory work and process modeling. Encouraging experimental results are obtained that showed the biomass had enhanced reactivity to the enzyme hydrolysis. The total sugar recovery for the hardwood species was 72% using 5 FPU/g enzyme dosage. The combination of electron beam and steam explosion provides an improvement in sugar conversion of more than 20% compared to steam explosion alone. This combination of pretreatments was modeled along with a novel ethanol dehydration process that is based on vapor permeation membranes. The economic feasibility of this novel pretreatment-dehydration technology was evaluated and compared with the dilute acid process proposed by NREL in 2011. Overall, the pretreatment-dehydration technology process produces the same ethanol yields (81 gal/bdton). However, the economics of this novel process does not look promising since the minimum ethanol selling price (MESP) to generate an internal rate of return of 10% is of 3.09 ;To enhance the economic potential of a biorefinery, the isolation of value-added co-products was incorporated into the base dilute acid biorefinery process. In this case the work focused on the ethanol extraction of the non-structural components of switchgrass prior to pretreatment and enzymatic hydrolysis. Promising results obtained with an Aspen PlusRTM model showed that a MESP of 2.5 ;In a second series of studies biomass fast pyrolysis and the bio-oil upgrading for the production of drop-in fuels was analyzed. Again, an Aspen PlusRTM based process model was used to evaluate the impacts of different biomass feedstock composition on the biofuel product. In this case the biofuel produced both a gasoline and diesel fraction. Model results showed that both the carbon and ash content of the biomass had an impact on the amount and price of the biofuel products. The highest biofuel yield were obtained with the hardwood (red maple) and perennial (switchgrass) feedstocks at about 48 gal/bdton of biomass, while the softwood (loblolly pine) provided 46 gal/bdton. Bark (acacia), the feedstock with the highest ash content, only provided 39 gal/bdton. But when the cost of these feedstocks was included the softwood is predicted to provide the lowest cost fuel, followed by the bark. As expected overall cost of the biofuel was dramatically impacted by the cost of the feedstock, and also by the use of a fraction of the intermediate bio-oil as the source of the hydrogen needed for upgrading the bio-oil to a hydrocarbon fuel product. Using hydrogen from natural gas instead of hydrogen from reforming the intermediate bio-oil reduced the estimated cost of the fuel product by...