Establishment of the LignoBoost technology has enabled recovery of kraft lignin on an industrial scale and opened up for increased utilization of lignin building blocks in materials and chemicals. The essence of this technology is a CO2-precipitation of lignin followed by dewatering and a final wash after an additional acidification (Fig 1). Filtration properties of lignin are of central importance from both the process efficiency and product quality perspective. Interestingly, initial trials point out improvement of filtration properties upon a heat-treatment of the acidified lignin slurry prior to the final wash (dashed square in Fig. 1). While highly desirable, this effect is not understood. Being able to relate it to specific structural and/or colloidal changes of the lignin particles in the slurry would allow for tailoring of filtration properties and a more efficient process design. The main task of this work is to reveal the structural changes in lignin associated with the heat-treatment of the acidified lignin slurry and evaluate them in the light of changed filtration behaviour.
Stora Enso is the world leading producer of LignoBoost lignin and is together with Valmet (providing the LignoBoost technology) the initiator of this project, that will be performed in close collaboration between these companies and Chalmers (Forest Products and Chemical Engineering) equipped with experience and analytical tools for lignin characterization.
Aim and objectives
The aim of the project is to understand the changed
filtration properties of the heat-treated lignin in
terms of colloidal and structural changes of lignin
The specific objectives are to account for following changes as a result of the heat treatment:
– Particle size distribution of the treated lignin
– Particle surface properties (e.g. porosity, roughness)
– Molecular weight distribution of the treated lignin
– Structural characteristics (linkages, functionalities).
1. Heat-treatment of the lignin slurry will be preformed by Valmet.
2. Treated lignin will be characterized and compared to a non-treated reference lignin in terms of particle size distribution (by means of Focused Beam Refraction Measurements, FBRS), porosity and surface characteristics of the particles (by means of BET and electron microscopy), molecular weight distribution (GPC in DMSO/LiBr) and molecular structure (2D NMR). The work will be performed at Chalmers, Forest Products and Chemical Engineering.
3. Complementary work (subject to time): Mimic the Valmet treatment in a laboratory set up (a simple reaction vessel) while in situ monitoring both agglomeration (by an FBRM probe) and changes in the dissolved compounds (by an FTIR probe).
4. Evaluation of the results will be performed in close collaboration with SE and Valmet.
The applicants should preferably have a background in chemical engineering, wood chemistry and process technology with a collaborative approach. The project can be performed in pair.
January 2024 or according to agreement