Pretreatment methods to obtain pumpable high solid loading wood–water slurries for continuous hydrothermal liquefaction systems

Continuous Hydrothermal Liquefaction of Biomass: A Critical Review

“…In general, pumpability of biomass slurries has not received much attention, but recently studies [28,79,103,104] have identified methodologies and tests to identify potentially pumpable slurries from different types of biomass including lignocellulosics, microalgae, and seaweed. A simple test dubbed the "syringe test", in which a biomass slurry is pressed through a standard medical syringe has been shown to be a fast and reliable method to determine whether a slurry is not pumpable [103]: if the slurry destabilizes and separates into a dry and a wet fraction, this particular slurry is most likely not pumpable. If, on the other hand, it stays a homogeneous slurry as it passes through the syringe, there is a good chance but no guarantee that it will be pumpable at relevant HTL pressures.…”

“…For larger systems, a major study [105] carried out by PNNL identified a range of pumps capable of reaching 15% dry matter content for wood particles less than 30 µm in diameter. This was supported by a study by Aalborg University [103], in which wood powder was milled to less than 125 µm in diameter allowing a pumpable slurry of 20% dry matter content to be continuously fed to an HTL plant. Yet, for larger plants such a downsizing is likely to be quite cost intensive and different approaches to use larger input sizes such as wood chips would be necessary.…”

Optimisation of bio-oil production by hydrothermal liquefaction of agro-industrial residues: Blackcurrant pomace ( Ribes nigrum L.) as an example

“…The solids loading at the inlet of the conversion unit is a crucial process variable for hydrothermal liquefaction, since it directly impacts the energy consumption of the process. To date, mass ra tios between dry biomass and water around 0.15 are achievable for continuous feeding of HTL units [3], although pre treatment methods could increase this ratio to 0.2 [36]. Solid loadings around 15 20% mass fraction are generally needed to ensure the economic benefits of the process, while lower concentrations might reduce its economic advantages because of high capital costs and high energy consumption [2].…”

Optimization of Xylose Recovery in Oil Palm Empty Fruit Bunches for Xylitol Production

“…Another study stated that a high SL pretreatment (20% SL) required a combination pretreatment using maleic acid and a saccharification process [46]. Another difficulty in using high solid loading was obtaining a pumpable slurry for the subsequent enzymatic hydrolysis [47].…”