Techno-economic assessment of the effect of torrefaction on fast pyrolysis of pine

Techno-economic assessment of bio-oil production from fast pyrolysis of pine was explored through process simulation. In this work, bio-oil production via a one-step pyrolysis route and a two-step pyrolysis which included a torrefaction step before fast pyrolysis were modeled to process 1000 MT/day of dry feed (dry basis) through the pyrolyzer at a temperature of 530 °C while two-step -pyrolysis was investigated at three different torrefaction temperatures of 290, 310, and 330 °C. Different scenarios that included the use of fossil energy to produce process heat as well as use of renewable energy either through the combustion of char or a portion of the condensates from -torrefaction were also investigated. Economic analysis indicates that a torrefaction step results in a reduction in the minimum selling price of bio-oil produced which reduced further with -torrefaction -temperature with lowest bio-oil price of $1.04/gal obtained for a two-step pyrolysis at torrefaction -temperature of 330 °C in comparison to $1.32/gal for a one-step process. Minimum selling price of bio-oil on an energy basis however suggests a higher price of about $22.19/GJ for a two-step in -comparison to $16.89/GJ for a one-step. There could be a trade-offs between the higher quality and the higher selling price considering the downstream upgrade step to hydrocarbon fuel.