Panu Tikka re-visited his patent issued back in mid 90’s entitled “Process for preparing kraft pulp”. Panu shortly describes his invention and how it affects current pulp mills processes:
SciTech was asked to make a fundamental study on a kraft displacement cooking process which was newly discovered and taken in use in the first mill-scale process applications in Finland, USA and Canada. The development had found its initiative and motivation in finding a much better heat economy, but the changes in the cooking chemistry and pulp fiber physics and paper technical properties were not known.
SciTech work and co-operation with the client led to the discovery of a “treasure” of advantages: Up to 50% higher tear-tensile pulp strength, significantly less fiber damage, very efficient kraft cooking step to extremely low residual lignin concentration (low kappa number) by re-using the hydrosulfide in the hot black liquor. In addition, the first displacement batch cooking laboratory-pilot digesters were build. The new invention was the re-use of the black liquor’s residual sulphur and heat-treatment as part of the displacements before the cooking phase.
Patent was applied, granted and used in tons of pulp mill cooking plant projects all over the world – over 20 million tons of kraft pulp is made with this new “SuperBatch” process in 150 digesters. Later, Scitech developed other patented versions of the process: a pre-hydrolysis-neutralization-kraft cooking for dissolving pulp and polysulfide-pretreatment-SuperBatch for paper pulp with higher yield and hemicellulose content.