Background: The Hydrothermal liquefaction (HTL) of the biomass generates two
phases, namely, liquid bio crude & an aqueous phase containing soluble hydrocarbons. Hydrothermal
gasification converts aqueous hydrocarbons into fuel gas containing mainly CH4,
H2 and CO2.
Objective: Objective of the present study is to carry out thermodynamic analysis of sub and supercritical
water gasification of aqueous fraction of HTL for hydrogen rich bio-gas production.
Method: In this study, equilibrium composition calculations for sub and supercritical water
gasification product performed using Gibbs method for aqueous HTL fraction & its constituent
Results: Thermodynamic model was validated with experimental data at different operating
conditions. Sensitivity study of critical process parameters (for individual constituents components
of HTL aqueous fraction and their multicomponent mixture) conducted over broad
range, namely, temperature (300-1000
C), pressure (190-340 bar) and feed concentration (1-
30 wt%) to identify optimum process condition.
Conclusions: Increase in reaction temperature shows the positive effect on hydrogen mole
fraction in product gas mixture. However, increase in pressure leads to decrease in hydrogen
mole fraction in product. Maximum hydrogen concentration in the range of 0.60-0.75 mole
fraction (depending upon selected composition of organics in multicomponent aqueous fraction)
was observed in the bio-gas at temperature of 705
C. Lower feedstock concentration of
aqueous HTL organics is observed to lead to high hydrogen production.