Large-scale gasifi cation-based systems for producing Fischer-Tropsch (F-T) fuels (diesel and gasoline blendstocks), dimethyl ether (DME), or hydrogen from switchgrass -with electricity as a coproduct in each caseare assessed using a self-consistent design, simulation, and cost analysis framework. We provide an overview of alternative process designs for coproducing these fuels and power assuming commercially mature technology performance and discuss the commercial status of key component technologies. Overall effi ciencies (lower-heatingvalue basis) of producing fuels plus electricity in these designs ranges from 57% for F-T fuels, 55-61% for DME, and 58-64% for hydrogen. Detailed capital cost estimates for each design are developed, on the basis of which prospective commercial economics of future large-scale facilities that coproduce fuels and power are evaluated.
Three process designs for producing ethanol and electricity from switchgrass are evaluated: a basecase technology scenario involving dilute acid pre-treatment and simultaneous saccharifi cation and fermentation, and two mature technology scenarios incorporating ammonia fi ber expansion pre-treatment and consolidated bioprocessing -one with conventional Rankine power coproduction, and one coproducing power via a gas turbine combined cycle. Material and energy balances -resulting from detailed Aspen Plus models -are reported and used to estimate processing costs and perform discounted cash fl ow analysis to assess plant profi tability. The mature technology -designs signifi cantly improve both process effi ciency and cost relative to base-case cellulosic ethanol technology, with the resulting fossil fuel displacement being decidedly positive and production costs competitive with gasoline, even at relatively low prices.
Seven process designs for producing ethanol and several coproducts from switchgrass are evaluated:four involving combinations of ethanol, thermochemical fuels (including Fischer-Tropsch liquids, hydrogen, and methane) and/or power, and three coproducing animal feed protein. Material and energy balances -resulting from detailed Aspen Plus models -are reported and used to estimate processing costs and perform discounted cash fl ow analysis to assess plant profi tability. In these mature technology designs, fossil fuel displacement is decidedly positive and production costs competitive with gasoline.
Detailed process designs and mass/energy balances are developed using a consistent modeling framework and input parameter assumptions for biomass-based power generation at large scale (4536 dry metric tonnes per day switchgrass input), assuming future commercially mature component equipment performance levels. The simulated systems include two gasifi cation-based gas turbine combined cycles (B-IGCC) designed around different gasifi er technologies, one gasifi cation-based solid oxide fuel cell cycle (B-IGSOFC), and a steam-Rankine cycle. The simulated design-point effi ciency of the B-IGSOFC is the highest among all systems (51.8%, LHV basis), with modestly lower effi ciencies for the B-IGCC design using a pressurized, oxygen-blown gasifi er (49.5% LHV) and for the B-IGCC design using a low-pressure indirectly heated gasifi er (48.6%, LHV). The steam-Rankine system has a simulated effi ciency of 33.0% (LHV). Detailed capital costs are estimated assuming commercially mature ('N th plant') technologies for the two B-IGCC and the steam-Rankine systems. B-IGCC systems are more capital-intensive than the steam-Rankine system, but discounted cash fl ow rate of return calculations highlight the total cost advantage of the B-IGCC systems when biomass prices are higher. Uncertainties regarding prospective mature-technology costs for solid oxide fuel cells and hot gas sulfur clean-up technologies assumed for the B-IGSOFC performance analysis make it diffi cult to evaluate the prospective electricity generating costs for B-IG-SOFC relative to B-IGCC. The rough analysis here suggests that B-IGSOFC will not show improved economics relative to B-IGCC at the large scale considered here.Lower heating value (MJ/kg) 17.0Higher heating value (MJ/kg) 18.7
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