  A thermophysical model is developed that can predict the properties of two
lignin mixtures, black liquor and lignosulfonates, up to 50% mass fractions, at
hydrothermal conditions. An uncertainty quantification framework linked with
classic thermodynamical modelling was included to account for the extreme
variability of the raw material. An idealized flow simulation verified the
model, where hot compressed water mixes with a cold, aqueous lignin stream in a
T-piece reactor configuration. The uncertainty quantification procedure
determined that density and heat capacity uncertainty significantly influence
residence time, and viscosity uncertainty mainly affects mixing. Micromixing
time is five-fold and ten-fold higher for black liquor and lignosulfonates
mixtures, respectively, compared to pure water mixing. The uncertainty in all
simulated quantities of interest caused by the thermophysical model is reduced
by increasing flow rates. This study predicted chemical reactor behaviour under
varying thermophysical conditions and their final effect in terms of confidence
intervals.
