1. Let it Flow? A Comparative Study Between a Batch Reactor and a Continuous Flow Reactor for Hydrothermal Liquefaction
M. Klemmer, A. J. Mørup, P. S. Christensen, K. Houlberg and B. B. Iversen
Department of Chemistry, Aarhus University
Introduction
Hydrothermal liquefaction (HTL) is a promising technique to convert wet biomass into bio-oil using the unique properties of subcritical water.1
Most studies on HTL are conducted on batch reactor systems, limiting the amount of reacting material as well as the heating and cooling rates. The continuous bio-oil reactor system at Aarhus University (CBORS) provides the possibilities of well-defined heating and cooling rates and regular product sampling, allowing a detailed statistical analysis.2 Moreover, it is a relevant pilot reactor and thus a step closer to industrial scaled HTL reactors.
The HTL experiment results in four product fractions: the bio-oil, an aqueous phase containing polar water soluble organics (WSO), a gas phase and solid residues (SR).
Yields
Elemental Content
Batch Reactor
Continuous Bio-Oil Reactor System (CBORS)
25 mL slurry per experiment
Heating rate: 0.6 °C/s
Experiment: T = 350 °C p = 250 bar t = 15 min
Feedstock: 20 wt% DDGS 2 wt% K2CO3 78 wt% H2O
400 mL slurry per injector
Heating rate: °C/s
Experiment: T = 350 °C p = 250 bar t = 15 min
Feedstock: 20 wt% DDGS 2 wt% K2CO3 78 wt% H2O
Conclusion
The continuous bio-oil reactor system produces higher bio-oil and WSO yields and less SR. However, the elemental analysis of the bio-oil revealed higher carbon and lower oxygen contents suggesting a higher bio-oil quality. This can be explained by the different separation techniques of the bio-oil from the aqueous phase, involving solvents in the case of the batch reactor.
The continuous flow reactor shows superiority in experiment conditions and yield distribution. Further analysis of the bio-oil also sugges-ted a good quality despite the high water content.
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