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Producing pulp in a digester

RISE Bioeconomy’s test bed for pulp production is frequently used by both joint R&D projects and bilateral projects involving individual companies.

The 1 kg flexible forced-circulation digester system can perform all types of pulping processes.

In our test bed for pulp production, all modern cooking processes can be simulated, including production of cellulose for textile fibres and other products. We can also produce sugar from wood and black liquor, as well as lignin from black liquor. Using ultrafiltration with a membrane it is possible to achieve good separation between various components.

We have a flexible digester that consists of several different digester systems. A digester system consists of a digester which delignifies 1 kg of wood. There are also four tanks in the system that can be used for simulating various cooking processes. The process conditions can be varied, based on time, temperature, displacement of cooking liquids, cooking liquid amounts and cooking methods. During the cooking process, both batch and continuous digesting can be simulated.

In this digester system we can also simulate the importance of shearing and compression in order to imitate the conditions the chips are exposed to in the digester. You can also study how the distribution of chip size affects the pressure drop during delignification. This can be done thanks to a specially constructed insert inside the digester. 

In our bioreactor we can work on a large scale, processing up to 40 kg of wood per batch. It is also possible to carry out traditional digestion in order to produce large quantities of pulp. The bioreactor is also used to release various wood substances and refine them, for example production of hemicellulose and lignin from digestion liquors.

The unbleached pulp can also be oxygen-delignified and bleached in our bleaching plant in order to produce specific highly reactive pulps with textiles as the end purpose.

Rise Bioeconomy’s concept also includes producing highly reactive cellulose for textiles in existing pulp processes through customised cooking and bleaching sequences, dissolution of cellulose, regeneration and spinning. In addition, the concept includes recycling chemicals from pulp production, dissolution and spinning, as well as simulating various scenarios from a technical and financial perspective.



A comparison of fibre deformations from mill like and laboratory kraft cooking of softwood
Salmén L, Hornatowska J
Nordic Pulp Paper Research J. 29(2014):2, 211-217


Sulphur-free process for dissolving pulp
Karlström K, Sjögren B, Kulander I
5th Nordic Wood Biorefinery Conference (NWBC), Stockholm, Sweden, March 25-27, 2014, Proceedings pp 253-254


Environmental performance of modern ECF bleaching
Axegård P, Bergnor E
Int. Pulp Bleaching Conference, Portland, OR, USA, Oct. 5-7, 2011, Proceedings pp 31


Salmén L. and Lundqvist F. (2011)
Effects of mechanical forces on strength delivery in softwood kraft cooking
Appita 64(1): 89-94.


Effects of mechanical forces on strength delivery in softwood kraft cooking
Salmén L, Lundqvist F
Appita 64(2011):1, 89-94


Impact of ionic strength on alkalinity during kraft cooking and impact on process economy
Lundqvist F, Olm L, Tormund D
ABTCP 2008, Sao Paulo, Brazil, Oct. 13-16, 2008


Continuous kraft cooking: research and applications
Annergren G, Lundqvist F
STFI-Packforsk, Stockholm 2008, 82 pp (ISBN 9789186018160)