Advancements in hydrothermal liquefaction reactors: Overview and prospects

S. N. Sahu, N. K. Sahoo, S. N. Naik, D. M. Mahapatra

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

20 Scopus citations

Abstract

In the past few decades, increasing environmental pollution and rapid depletion of conventional fossil fuels has necessitated a need for an alternate renewable source of fuels. In this context, biomass-based biocrude has received much interest as a renewable and sustainable alternative to crude petroleum potentially contributing to meeting the growing demands for petrochemical and fuel. Out of the two conversion processes, namely thermochemical and biochemical, the former is the most attractive option for biocrude production. Examples of thermochemical conversion processes include direct combustion, pyrolysis, gasification, and liquefaction. In contrast to the first three options, which require dry biomass, hydrothermal liquefaction (HTL) is suitable for handling wet biomass with varying moisture contents, thus avoiding drying related throughput. Usually, HTL operates under mild conditions of temperature (250°C-350°C) and pressure (10-20MPa). During the HTL process, water in its subcritical stage reacts with macromolecules involving a variety of reactions such as dehydration, hydrolysis, deoxygenation, fragmentation, and aromatization, resulting in solid biochar, liquid biocrude, and aqueous and gaseous fractions. Biocrude production is hardly dependent on the lipid content of biomass. Under suitable conditions, carbohydrate, protein, and fibers also yield biocrude. The nonselectivity of feed broadens its application for the inclusion of wastewater-borne mixed algal biomass. By standardizing the various conditions affecting the process such as feed quality, liquid-solid ratio of the feed, reaction time, mixing, temperature, pressure, catalyst, and solvent biocrude yields can be optimized. For the success of HTL in commercial realization, a continuous flow process needs to be established. Accordingly, advancements and innovations in this field are imperative for establishing the sustainability of the technology.

Original languageEnglish
Title of host publicationBioreactors
Subtitle of host publicationSustainable Design and Industrial Applications in Mitigation of GHG Emissions
PublisherElsevier
Pages195-213
Number of pages19
ISBN (Electronic)9780128212646
DOIs
StatePublished - 1 Jan 2020
Externally publishedYes

Keywords

  • Biochar
  • Biocrude
  • Biomass conversion
  • Hydrothermal liquefaction
  • Value-added products

ASJC Scopus subject areas

  • General Energy

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