Executive SummaryThe goal of the U.S. Department of Energy's Bioenergy Technologies Office (BETO) is to enable the development of biomass technologies to: Reduce dependence on foreign oil Promote the use of diverse, domestic, and sustainable energy resource Establish a domestic bioenergy industry Reduce carbon emissions from energy production and consumption. (DOE 2013) To meet these goals, the BETO promotes the development of liquid hydrocarbon fuels that can serve as gasoline, jet and diesel blendstocks.This report describes a proposed thermochemical process for converting biomass into liquid transportation fuels via fast pyrolysis followed by hydroprocessing of the condensed pyrolysis oil. As such, the analysis does not reflect the current state of commercially-available technology but includes advancements that are likely, and targeted to be achieved by 2017. The purpose of this study is to quantify the economic impact of individual conversion targets to allow a focused effort towards achieving cost reductions.
Off-gas 10% of total Carbon AHTL Oil 72% of total Carbon (77% algal carbon recovery) Natural Gas 3.5% of total Carbon in Water & Solids Recycle to Ponds 8% of total Carbon as dissolved CO2 (9% of algal carbon) Reformer & Heater Exhaust 23% of total Carbon (Includes 21% of algal carbon) Natural Gas Drier & Exhaust 3.5% of total Carbon in
The dry basis elemental composition of the feedstock, shown in Table 2, is identical to previous NREL and PNNL design reports [20,21]. The composition was originally assumed to come from pulpwood. Recent feedstock logistics work at the Idaho National Laboratory (INL) suggests that the use of blended material may be required to meet a cost target of $80/dry U.S. ton while still meeting these specifications [22]. For the purpose of this report, it is assumed that any blended material provided to meet this feedstock elemental composition will not adversely affect fast pyrolysis conversion efficiencies. Ongoing studies being conducted jointly by INL, NREL, and PNNL will provide experimental evidence of the impact of blended feedstocks on fast pyrolysis and gasification processes. Future TEA will be modified to reflect conversion impacts inferred from such studies.This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. not considered in this design in order to focus on the core technology of in situ and ex situ fast pyrolysis vapor upgrading. Aspen Plus ModelAn Aspen Plus Version 7.2 simulation was used as the basis for this report. Since the products in pyrolysis are numerous and varied, only selected model compounds were used to represent the product slate. Additional hydrocarbon species were added to represent hydroprocessing products. Many of the desired molecular species in the desired boiling ranges for light and heavy fractions did not exist in Aspen Plus databanks and physical property parameters needed to be estimated. The biomass feedstock, ash, char, and coke were modeled as non-conventional components. Appendix F provides information about compounds selected to represent the process. The Peng-Robinson with Boston-Mathias modifications (PR-BM) equation of state was used throughout most of the process simulation. The ASME 1967 steam table correlations (STEAM-TA) were used for the steam cycle calculations. Combustor/Regenerator Temperature, °C (°F) 650 (1,202) 720 (1,328) 650 (1,202) Pressure, psia (bar) 117 (8.1) 117 (8.1) 113 (7.8) Excess air (%) 20 20 20 Solids temperature before transfer to reactor, °C (°F) 650 (1,202) 720 (1,328) 341 (645) No. of cyclones per combustor 2 2 2 Area 200 Equipment Cost EstimationsCapital costs for the equipment in this area were estimated by Harris Group. A previously developed spreadsheet tool for gasifier costs was leveraged for this exercise. Cost estimates from this tool were compared with order of magnitude estimates from technology vendors and documented in Appendix I of Worley et al.
Glossary of TermsFast pyrolysis -thermal conversion in the absence of oxygen at short residence time, for woody biomass typical conditions are <2 seconds at ~500 °C Hydrothermal -processing in hot pressurized water Bio-oil -liquid product of fast pyrolysis Biocrude -liquid oil product from hydrothermal liquefaction Upgrading -multi-step hydroprocessing to convert bio-oil in liquid hydrocarbon products Hydrotreating -single-step hydroprocessing to convert biocrude into liquid hydrocarbon products Hydroprocessing -chemical reaction with hydrogen gas, typically a catalytic process operated at elevated pressure, usually to remove heteroatoms, remove unsaturation, and reduce molecular weight.Heavy hydrocarbon --hydrocarbon product distilling at temperatures higher than diesel Nth plant -commercial plant operating an established process, not a pioneer plant 14 http://www.fortum.com/en/mediaroom/Pages/fortum-invests-eur-20-million-to-build-the-worlds-first-industrialscale-integrated-bio-oil-plant.aspx 15
The Department of Energy Bioenergy Technologies Office (BETO) invests in research and development of new pathways for commercially viable conversion of biomass into drop-in ready transportation fuels, fuel blendstocks and products. The primary emphasis has been on terrestrial and algae feedstocks, but more recently BETO has begun to explore the potential of wet wastes for biofuel production, with focus on wastewater residuals, manure, food waste, and fats, oils and grease. A recent resource analysis estimates that 77 million dry tons per year of these wastes are generated annually, 65% of which are underutilized for any beneficial purpose. 1 Approximately 14 million dry tons of the total resource is wastewater residuals (sludge and biosolids) generated at the nation's wastewater treatment plants (WWTPs). 2 Conversion of this resource into transportation fuels could significantly contribute to the creation of a new domestic bioenergy and bioproduct industry, while providing an economically and environmentally sustainable alternative for current waste disposal practices.
The dry basis elemental composition of the feedstock, shown in Table 2, is identical to previous NREL and PNNL design reports [20,21]. The composition was originally assumed to come from pulpwood. Recent feedstock logistics work at the Idaho National Laboratory (INL) suggests that the use of blended material may be required to meet a cost target of $80/dry U.S. ton while still meeting these specifications [22]. For the purpose of this report, it is assumed that any blended material provided to meet this feedstock elemental composition will not adversely affect fast pyrolysis conversion efficiencies. Ongoing studies being conducted jointly by INL, NREL, and PNNL will provide experimental evidence of the impact of blended feedstocks on fast pyrolysis and gasification processes. Future TEA will be modified to reflect conversion impacts inferred from such studies.This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. not considered in this design in order to focus on the core technology of in situ and ex situ fast pyrolysis vapor upgrading. Aspen Plus ModelAn Aspen Plus Version 7.2 simulation was used as the basis for this report. Since the products in pyrolysis are numerous and varied, only selected model compounds were used to represent the product slate. Additional hydrocarbon species were added to represent hydroprocessing products. Many of the desired molecular species in the desired boiling ranges for light and heavy fractions did not exist in Aspen Plus databanks and physical property parameters needed to be estimated. The biomass feedstock, ash, char, and coke were modeled as non-conventional components. Appendix F provides information about compounds selected to represent the process. The Peng-Robinson with Boston-Mathias modifications (PR-BM) equation of state was used throughout most of the process simulation. The ASME 1967 steam table correlations (STEAM-TA) were used for the steam cycle calculations. Combustor/Regenerator Temperature, °C (°F) 650 (1,202) 720 (1,328) 650 (1,202) Pressure, psia (bar) 117 (8.1) 117 (8.1) 113 (7.8) Excess air (%) 20 20 20 Solids temperature before transfer to reactor, °C (°F) 650 (1,202) 720 (1,328) 341 (645) No. of cyclones per combustor 2 2 2 Area 200 Equipment Cost EstimationsCapital costs for the equipment in this area were estimated by Harris Group. A previously developed spreadsheet tool for gasifier costs was leveraged for this exercise. Cost estimates from this tool were compared with order of magnitude estimates from technology vendors and documented in Appendix I of Worley et al.
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