Concepedia

Mass and Energy Balances of Wet Torrefaction of Lignocellulosic Biomass

Yan Wei, Jason Hastings, Tapas C. Acharjee, Charles J. Coronella, Victor R. Vásquez

Energy & Fuels · 2010 · 256 citations · 16 references

TL;DR

Handling diverse lignocellulosic biomass for thermochemical conversion is challenging, but wet torrefaction pretreats it into an energy‑dense solid fuel with more uniform handling characteristics. Wet torrefaction reacts biomass with hot compressed water at 200–260 °C, and mass and energy balances—including heat of reaction estimates—were established for these conditions. The solid’s fuel value can rise by up to 36 %, its mass decreases while gas production increases with temperature, and the process yields pretreated solid, precipitates, volatile acids, and gases, with the heat of reaction nearly zero and only slight temperature dependence.

Abstract

Solid handling of diverse lignocellulosic biomass feedstock is very challenging for thermochemical conversion to renewable fuels. Wet torrefaction is a pretreatment process to convert biomass to energy-dense solid fuel, with relatively uniform handling characteristics. The fuel value of the produced solid may be as much as 36% higher than that of the original biomass. In the process, biomass is reacted with hot compressed water at the temperature of 200−260 °C. The mass and energy balance in wet torrefaction were established for these conditions. Products include pretreated solid, precipitates (simple sugars and sugar derivatives), volatile acids, and gases (carbon dioxide). With increasing temperature, the mass of the solid decreases, the fuel value of the solid increases, and the quantity of gas increases. The heat of reaction for each temperature was estimated from an energy balance. The uncertainty analysis also showed that the temperature slightly affected the heat of reaction, which is very close to zero.