Production of Hydrocarbon Fuel Using Two-Step Torrefaction and Fast Pyrolysis of Pine. Part 1: Techno-economic Analysis

As part I of two companion papers, the present paper evaluates the economic feasibility of hydrocarbon biofuel production via two pathways: a one-step production pathway through fast pyrolysis of biomass followed by the catalytic upgrade of bio-oil to a liquid hydrocarbon biofuel and a novel two-step pathway that includes a torrefaction pretreatment step prior to fast pyrolysis and then the catalytic upgrade. These two pathways were modeled using Aspen Plus to process 1000 dry metric tons/day of feed through the fast pyrolysis unit operating at 530 degrees C whereas torrefaction for the two-step pathway was investigated at three different torrefaction temperatures of 290, 310, and 330 degrees C. Three scenarios of producing process heat from natural gas, internal byproducts biochar supplemented with natural gas, and torrefaction condensate were investigated, with additional heat integration considered. Minimum selling price ranged from $4.01/gal to $4.78/gal for the heat-integrated processes whereas the price ranged from $4.70/gal to $6.84/gal without heat integration. Analysis indicated that a one-step pathway and a two-step pathway with torrefaction taking place at 290 degrees C yielded comparable least minimum selling price and it increased with increasing torrefaction temperature. Sensitivity analysis showed that the yield of hydrocarbon biofuel, total project investment, and internal rate of return have the greatest impact.