Production of a pure lignin product, part 1: Distribution and removal of inorganics in eucalyptus globulus kraft lignin

Paper in proceeding, 2013

The LignoBoost process is a recently commercialized process for separation of lignin from krafl cooking black liquor. It is believed that future high value lignin-based products, such as carbon fibers, will require a lignin raw material essentially free from inorganic impurities. This work focuses on the effect of different process parameters on the content of inorganic impurities in the final LignoBoost lignin, produced from a black liquor from pulping of Eucalyptus Globulus. Attention has been paid to the distribution of the inorganics Na, K, Ca, Al, Mn, Mg, Si and Fe. It was found that, by applying low precipitation pH, the amounts of Ca, Al, Mn, Mg, Si and Fe in the lignin product could be slightly reduced. By reducing the re-suspension pH and wash pH to low levels the ash content could be greatly reduced, primarily due to the dissolution of Ca-oxalate particles present in the lignin. Repeated re-suspension was followed by washing results in a lignin with considerably lower Na and K content. By slightly increasing the retention time in the re-suspension stage, the content of Mg, Al, Mn, Si and Fe could be reduced by -50%. Copyright © 2013 by the TAPPI Press. All rights reserved.