Hydrothermal liquefaction (HTL) is a promising technology for better utilizations of lignin residues from paper and pulp production. In the process of HTL, hot water and high pressure (374oC, 22.1 MPa) are used to convert lignin to bio-oil (HTL oil). Rapid heating during the process (fast HTL) helps improve the oil production and quality.
At NTNU, Department of Energy and Process Engineering, we have developed a reactor technology for fast HTL. The goal of this project is to further develop and optimize this technology using theoretical and experimental approaches.
An improvement of the HTL technology will make it more competitive and increase the utilizations of lignin residues. The project will contribute to strengthening Norway's role in bioenergy, biorefinery and circular bioeconomy.
This project deals with CFD (Computational Fluid Dynamics) study, optimization, and experimental validation of a reactor and process, based on the concept of nozzle reactor, for continuous non-catalytic fast hydrothermal liquefaction (HTL) of lignin residue, in conditions relevant for industrialization.
A nozzle reactor is essentially a pipe-in-pipe concentric setup in which the internal pipe has an open-ended nozzle. A hot stream of pure water is fed through the internal pipe, reaching out at the exit end (nozzle) of the pipe. A cold stream of biomass solution is fed through the outer pipe. At the nozzle exit, the hot and cold streams impinge to each other causing a forced mixing process. As a result, very good mixing and thus high heating rates can be achieved in the reactor. In addition, the reactor is capable of creating strong net downstream flow/eddies for rapid transport of particles out of the reactor, to prevent particle accumulation and deposition within the reactor. Therefore, the reactor is very suitable for fast HTL.
ANSYS Fluent will be employed for the CFD study, focusing on the mixing dynamics in the reactor and how to optimize the mixing of the hot and cold streams at different scales. An experimental setup will be optimized accordingly for empirical validations of the result from the CFD study, employing water soluble lignosulfonates as lignin residue. Results from the CFD study and experimental validation will be used for a techno-economic assessment employing Aspen Plus software.
This is a 3-year project developed under collaboration between established researchers from Norwegian University of Science and Technology - Department of Energy and Process Engineering and the University of Valladolid - Department of Energy and Fluid Mechanics, supported by Borregaard AS as industrial partner and potential user.