In this work, the effect of reaction time and biomass-to-H2O ratio on the structural
evolution of hydrochar and kinetic of by hydrothermal processing of corn Stover with hot
compressed H2O, have been systematically investigated. The experiments were carried out at
250 °C, heating rate of 2.0 °C/min, biomass-to-H2O ratio of 1:10, and reaction times of 60, 120,
and 240 minutes, and at 250 °C, 240 minutes, heating rate of 2.0 °C/min, and biomass-to-H2O
water ratio of 1:10, 1:15, and 1:20, using a pilot scale stirred tank reactor of 5 gallon. The
characterization of solid phase products performed by thermo-gravimetric analysis, scanning
electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction, and elemental
analysis (C, N, H, S). The physical-chemistry properties of solid phase analyzed in terms of dry
matter (DM), total organic content (TOC), and ash. The yields of solid and gas phases decrease
linearly with decreasing biomass-to-H2O ratio, while that of liquid phases increases linearly.
For constant biomass-to-H2O ratio, the yields of solid, liquid, and gaseous reaction products
varied between 52.97 and 35.82% (wt.), 44.84 and 54.59% (wt.), and 2.19 and 9.58% (wt.),
respectively. The yield of solids decreases exponentially by decreasing the reaction time, while
the yields of liquid and gas phases increase exponentially. For constant biomass-to-H2O ratio,
TG/DTG curves shows that reaction time of 60 minutes was not enough to carbonize corn
Stover. For constant reaction time, TG/DTG curves shows that increasing the H2O-to-biomass
ratio worse the carbonization of corn Stover. For constant biomass-to-H2O ratio, the SEM
images show the main morphological structure of the corn Stover remains practically
unchanged, while for constant reaction time, SEM images show that plant microstructure
retains part of its original morphology, demonstrating that a decrease on biomass-to-H2O ratio
worse the carbonization of corn Stover. For constant biomass-to-H2O ratio, the EDX analysis
shows that the carbon content in hydrochar increases with reaction time, while for constant
reaction time, the carbon content decreases with increasing biomass-to-H2O ratio. The kinetic
of corn Stover degradation was correlated with a pseudo-first order exponential model,
exhibiting a root-mean-square error (r2) of 0,996, demonstrating that degradation kinetics of
corn Stover with hot compressed H2O, expressed as hydrochar formation, is well described by
an exponential decay kinetics.
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