Maria Sedin

Correlations for the viscosity of lignin lean black liquor

In this study, experimental results from earlier work on viscosity measurements of black liquors with different lignin contents were used to develop an empirical model describing viscosity as a function of temperature, dry content and concentration of lignin and hemicellulose. The liquors studied were taken from six different lignin extraction runs, according to the LignoBoost process, at different mills. The viscosity data was available at a wide range of temperature (40-130 degrees C) and dry content (30-70 w/w-%): this data was used to calculate the parameters in the model. Furthermore, one of the general correlations was developed by taking the concentrations of lignin and hemicellulose into account. The results of this study showed that a much better fitting of the model could be obtained by taking the influence of the organic content in the black liquor into account.

Improved yield of carbon fibres from cellulose and kraft lignin

Abstract To meet the demand for carbon-fibre-reinforced composites in lightweight applications, cost-efficient processing and new raw materials are sought for. Cellulose and kraft lignin are each interesting renewables for this purpose due to their high availability. The molecular order of cellulose is an excellent property, as is the high carbon content of lignin. By co-processing cellulose and lignin, the advantages of these macromolecules are synergistic for producing carbon fibre (CF) of commercial grade in high yields. CFs were prepared from precursor fibres (PFs) made from 70:30 blends of softwood kraft lignin (SW-KL) and cellulose by dry-jet wet spinning with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) as a solvent. In focus was the impact of the molecular mass of lignin and the type of cellulose source on the CF yield and properties, while membrane-filtrated kraft lignin and cellulose from dissolving kraft pulp and fully bleached paper-grade SW-KP (kraft pulp) served as sources. Under the investigated conditions, the yield increased from around 22% for CF from neat cellulose to about 40% in the presence of lignin, irrespective of the type of SW-KL. The yield increment was also higher relative to the theoretical one for CF made from blends (69%) compared to those made from neat celluloses (48–51%). No difference in the mechanical properties of the produced CF was observed.