Development of an aqueous lignin mixture thermophysical model for hydrothermal liquefaction applications using uncertainty quantification tools

https://doi.org/10.1016/j.ces.2022.117944Get rights and content
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Highlights

  • Thermophysical model developed for aqueous lignin mixtures up to 50% by weight.

  • Novel uncertainty quantification methodology, based on polynomial chaos expansions.

  • Micromixing time increases up to five and ten-fold, depending on the lignin mixture.

  • Temperature and residence time results are similar for the two considered mixtures.

  • No significant impact of the thermophysical properties impact on the RTD curves.

Abstract

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 idealised 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 fivefold 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.

Keywords

Thermophysical modelling
Power law fluids
Lignin mixtures
Hydrothermal liquefaction
Mixing
Uncertainty quantification

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