Washing Yield: A Novel Method for Assessing Industrial Washing Efficiency

The project will be performed within the national research and educational program Resource Smart Processes that gathers the main industrial and academic actors within the Swedish forest industry and provides a strong collaborative environment with close connection to as well industry as state-of-the-art research infrastructure. As a master-thesis student in this program you will also participate in the networking and scientific events (workshops, conferences, project meetings) and collaborate closely both with the industrial and academic partners involved.

This project is together with: SCA, KTH


Efficient pulp washing successfully balances the highest quality of pulp, the removal of soluble impurities and dissolved solids to the evaporation plant. Optimal usage of washing water minimizes the load for the evaporation plant and simultaneously lowers the need for bleaching chemicals and effluents to the environment. Therefore, measuring the washer’s performance is vital for the kraft pulp mill. Brownstock washer performance can make a significant economic and environmental difference for a kraft pulp mill. However, despite these advantages, there is currently no standardized technique for evaluating washing efficiency. This project will focus on the evaluation of methods and models for assessing industrial washing efficiency, with particular attention to “washing yield.”


• To assess the washing performance industrially as “washing yield” compared to “ideal washing”.
• To investigate the washer’s performance under ideal, traditional, and conventional conditions.
• To review the methods for calculating washing efficiency, including dilution factor, displacement ratio, washing yield, Norden efficiency factor, and wash loss (measured in Na2SO4 kg/ADT).
• To analyze the quality of the wash liquor using analytical techniques.

Measurement methods:

The project will employ a range of analytical techniques, including Conductivity, Total Dissolved Solids (TDS), Total Solids (TS), Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), and Wash Loss measured as Na2SO4.
Washing efficiency will be assessed through the dilution factor, which gauges the volume of water used per ton of pulp, and washing loss, which quantifies the unremovable, washable components in the pulp that are carried over into the bleaching process. Various methods will be used to calculate washing efficiency, including the dilution factor, displacement ratio, washing yield, Norden efficiency factor, and wash loss (measured in Na2SO4 kg/ADT). The quality of the wash liquor will also be characterized. This Master’s thesis project


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.

Planned period:

Spring 2024

Contact details:

Eashwara Raju Snethilkumar, erse@kth.se

Olena Sevastyanova, olena@kth.se
Gunnar Henriksson, ghenrik@kth.se
Tomas Vikström, tomas.vikstrom@valmet.com
Maria Boman, maria.boman@sca.com
Daniel Solberg, daniel.solberg@sca.com