Development of a rigorous and generalized model on the hydrothermal liquefaction (HTL) process for bio-oil production

A rigorous process model for hydrothermal liquefaction (HTL) of microalgae is proposed in this work. This research attempts to uncover a complicated simulation scenario for the characterization of microalgae, the development of suitable reaction pathways, kinetics, and thermodynamics. In this study, 55 model compounds and 41 individual reactions were used to describe an HTL system. The kinetic parameters were regressed using literature data, which reported the results under different operating conditions using the three species of microalgae. The proposed kinetic model revealed acceptable predictivity by predicting 117 published biocrude yields (total 160) to within ± 10 wt% and 28 published HHV (total 39) to within ± 5 MJ/kg. Finally, a continuous HTL process was conceptually designed. The trade-off between the biocrude yield and HHV was investigated via multi-objective optimization (MOO), which yielded the best trade-off between the biocrude yields (37.2–60.0 wt%) and HHV (27.5 and 33.5 MJ/kg). This work presents a satisfactory first attempt to rigorously simulate a very complex HTL process. Its application in the preliminary process design, optimization, and economic analysis is recommended.