HTL: Hydrothermal Liquefaction for Bio-Oil Production from Lignocellulosic Biomass
In the BIOGO-for-Production project, Spike designed and built a Hydrothermal Liquefaction (HTL) plant dedicated to producing bio-oil from lignocellulosic biomass and organic residues. The plant operates under extreme conditions, up to 350 °C and 250 bar, which allow the biomass to remain in a liquid phase and promote the conversion of organic compounds into a dense, high-energy bio-crude. The facility has a capacity of 15 kg/h of slurry with 10% solids and produces approximately 0.45 kg/h of bio-oil.
Why HTL Technology is Strategic
Hydrothermal liquefaction is a key technology in the development of advanced biofuels. Unlike pyrolysis, it does not require prior drying and can process very wet biomass such as sludge, algae, or organic residues. HTL produces oil with lower oxygen content, higher calorific value, and a composition closer to fossil fuels compared to pyrolysis, due to the removal of oxygen primarily as CO₂ and H₂O.
Reactor and Process Design
The Spike plant uses a high-pressure reactor designed to ensure mechanical integrity, thermal stability, and compatibility with highly corrosive fluids. Design data indicate a maximum allowable pressure of 255 bar and a maximum temperature of 360 °C, while the design pressure and temperature reach 300 bar and 400 °C, respectively. The biomass-water slurry is pumped into the reactor by a dedicated high-pressure pump, one of the most critical components of the system, capable of handling abrasive and viscous slurries. Residence times range from 15 to 60 minutes and can be adjusted via bypass to study conversion kinetics and bio-oil yield.
A Continuous and Compact Configuration
Unlike batch HTL technologies described internationally, the Spike plant was designed as a continuous process, reducing critical components and simplifying operational layout. The system is containerized and integrates preheating, reactor, high-temperature filtration units, storage tanks for bio-oil and process water, as well as a gas vent section. This compact configuration supports future scale-up activities and industrial replication.
Experimental Functionality and Operational Flexibility
The HTL test bench allows experiments on different types of biomass, including high-moisture feedstocks, thanks to the absence of strict water content constraints. The system is fully instrumented to continuously measure flow rates, pressures, and temperatures, enabling evaluation of yield, bio-crude quality, and solid byproduct formation. The plant includes a hot filtration section that allows separation of mineral residues and char directly at the reactor outlet.
Outlook
The facility represents a scalable technology demonstrator, with potential applications in the biofuel industry, organic waste management, and the development of circular value chains based on residual biomass.
Patent application n. FI2015A000127 date:29.04.2015.
Patent n.1429628-PROPERTY: Spike Renewables Srl/RE-CORD