Hydrothermal liquefaction is a promising technology for the conversion of a wide range of bio-feedstock into a biocrude; a mixture of chemical compounds that holds the potential for a renewable production of chemicals and fuels. Most research in hydrothermal liquefaction is performed in batch type reactors, although a continuous and energy-efficient operation is paramount for such process to be feasible. In this work an experimental campaign in a continuous bench scale unit is presented. The campaign is based on glycerol-assisted hydrothermal liquefaction of aspen wood carried out with the presence of a homogeneous catalyst at supercritical water conditions, 400 • C and 300 bar. Furthermore, in the experimental campaign a water phase recirculation step is incorporated to evaluate the technical feasibility of such procedure. In total, four batches of approximately 100 kg of feed each were processed successfully at steady state conditions without any observation of system malfunctioning. The biocrude obtained was characterized using several analytical methods to evaluate the feasibility of the process and the quality of the product. Results showed that a high quality biocrude was obtained having a higher heating value of 34.3 MJ/kg. The volatile fraction of the biocrude consisted mostly of compounds having number of carbon atoms in the C 6 -C 12 range similar to gasoline. In terms of process feasibility, it was revealed that total organic carbon (TOC) and ash significantly accumulated in the water phase when such is recirculated for the proceeding batch. After four batches the TOC and the ash mass fraction of the water phase were 136.2 [g/L] and 12.6 [%], respectively. Water phase recirculation showed a slight increase in the biocrude quality in terms on an effective hydrogen-to-carbon ratio, but it showed no effects on the product gas composition or the pH of the water phase. The successful operation demonstrated the technical feasibility of a continuous production of high quality biocrude.

Biocrude from hydrothermal liquefaction of biomass provides a sustainable source from which to produce chemicals and fuels. However, just as for fossil crude, the chemical complexity of the biocrude impedes the characterization and hence identification of market potentials for both biocrude and individual fractions. Here, we reveal how fractional distillation of a biocrude can leverage biocrude characterization beyond state-of-the-art and uncover the full biocrude potential. By distillation combined with detailed individual analysis of the distillate fractions and distillation residue, more than 85 % of the total biocrude composition is determined. It is demonstrated that a total mass fraction of 48.2 % of the biocrude is volatile below 350 • C, comprising mainly value-added marketable ketones, oxygenated aromatics and prospective liquid fuel candidates, which are easily fractionated according to boiling points. Novel, high resolution pyr-GCxGC-MS analysis of the residue indicates a high molecular weight aromatic structure, valuable for bio-materials production or for further processing into fuels. The distillate fractions are mildly hydrotreated to show the fuel and chemical precursor potential of the volatile components. This results in the formation of mainly hydrocarbons and added-value phenolics. This work takes a significant step by going beyond the biocrude as an intermediate bulk energy product and addressing actual applications and pathways to these.

No abstract

No abstract

No abstract

Feedstock pumpability is one of the main obstacles for continuous processing of biomass through hydrothermal liquefaction, due to their tendency to form heterogeneous slurries. In this work a novel strategy is proposed to ensure lignocellulosic feed pumpability in HTL processing, even while applying elevated biomass loadings. In a first stage, a pumpable feed is prepared by an alkaline treatment of coarse wood chips at 180 °C, 120 minutes reaction time and 0.35 NaOH-to-wood ratio. In a subsequent stage the treated feedstock is converted into a bio-crude in a continuously operated 20 kg/h scale unit. In total 100 kg of wood paste with 25 % dry-matter is processed at 400 °C and 30 MPa, demonstrating the usefulness of this two-stage liquefaction strategy. As an additional advantage liquefaction of such pretreated wood shows increased biocrude yields with approximately 10% compared to the case where non-pretreated wood is liquefied.

No abstract

No abstract