Conceptual Process Design and Techno-Economic Assessment of Ex Situ Catalytic Fast Pyrolysis of Biomass: A Fixed Bed Reactor Implementation Scenario for Future Feasibility

Abstract

Ex situ catalytic fast pyrolysis of biomass is a promising route for the production of fungible liquid biofuels. There is significant ongoing research on the design and development of catalysts for this process. However, there are a limited number of studies investigating process configurations and their effects on biorefinery economics. Herein we present a conceptual process design with techno-economic assessment; it includes the production of upgraded bio-oil via fixed bed ex situ catalytic fast pyrolysis followed by final hydroprocessing to hydrocarbon fuel blendstocks. This study builds upon previous work using fluidized bed systems, as detailed in a recent design report led by the National Renewable Energy Laboratory (NREL/ TP-5100-62455); overall yields are assumed to be similar, and are based on enabling future feasibility. Assuming similar yields provides a basis for easy comparison and for studying the impacts of areas of focus in this study, namely, fixed bed reactor configurations and their catalyst development requirements, and the impacts of an inline hot gas filter. A comparison with the fluidized bed system shows that there is potential for higher capital costs and lower catalyst costs in the fixed bed system, leading to comparable overall costs. The key catalyst requirement is to enable the effective transformation of highly oxygenated biomass into hydrocarbons products with properties suitable for blending into current fuels. Potential catalyst materials are discussed, along with their suitability for deoxygenation, hydrogenation and C-C coupling chemistry. This chemistry is necessary during pyrolysis vapor upgrading for improved bio-oil quality, which enables efficient downstream hydroprocessing; C-C coupling helps increase the proportion of diesel/jet fuel range product. One potential benefit of fixed bed upgrading over fluidized bed upgrading is catalyst flexibility, providing greater control over chemistry and product composition. Since this study is based on future projections, the impacts of uncertainties in the underlying assumptions are quantified via sensitivity analysis. This analysis indicates that catalyst researchers should prioritize by: carbon efficiency [ catalyst cost [ catalyst lifetime, after initially testing for basic operational feasibility.

Lowering greenhouse gas (GHG) emissions: techno‐economic analysis of biomass conversion to biofuels and value‐added chemicals

“…The TEA fast pyrolysis of biomass using an ex situ fast catalytic process was investigated by Dutta et al . The TEA included the production of upgraded bio‐oil via fixed bed ex situ catalytic fast pyrolysis followed by final hydroprocessing to hydrocarbon fuel (HGF).…”

Formate‐assisted pyrolysis of biomass: an economic and modeling analysis

“…The material balances of pine sawdust gasification were determined using correlations presented by Dutta and Phillips . Remaining unit processes were simulated following procedures detailed in reports on process and economic analysis of RGD fuel production processes that are similar to FAsP process …”

“…The material and heat balances were used to size the process equipment. The individual process equipment cost of RGD fuel production process via FAsP, not including the process equipment cost of calcium formate regeneration section, was calculated using the previously published cost estimates of similar equipment . The rule of six‐tenths was employed to adjust the equipment cost to the corresponding equipment size.…”

“…The catalytic pyrolysis process has been proposed to address the shortcomings of RGD fuel production from cellulosic feedstock via fast pyrolysis . In the catalytic pyrolysis process, oxygen is removed as carbon dioxide by physically contacting biomass with the ZSM‐5 group of catalysts at temperatures between 400°C and 500°C.…”

“…Some of the drawbacks of producing RGD fuel via fast pyrolysis process can be overcome by formate‐assisted pyrolysis (FAsP) . In the FAsP process, cellulosic feedstock is pre‐treated with the calcium formate before it is pyrolyzed in a fluidized bed reactor that is operated at atmospheric pressure and a temperature of 500 °C; the operating conditions of FAsP process are similar to those of fast pyrolysis . In the FAsP process, carbon monoxide, hydrogen, and calcium carbonate are formed from the decomposition of calcium formate .…”