ModDD - Process modeling and new technical solutions for increased production rate

The aim of the project is to provide knowledge on how double disk refining in papermills can be more energy efficient.


To increase the process efficiency it is important to have a high production flow through the refiner and also apply larger forces on the fiber material in the refiner gap. This to reduce hysteresis losses.

Today, the possibility to utilize high production rates in double disc (DD) refining is limited by the design of the refiner inlet but also by the various operational strategies that are used for the process. The research will be developed through modeling and optimization of the refiner inlet, and by finding new technical solutions and process strategies.

Part 1 Modelling of DD refining

We will use these different methods to work with modelling of DD refining: SPH (smoothed particle hydrodynamics), DEM (discrete element method), DPFD (dissipative particle fluid dynamics) and MD (molecular dynamics). The research project is developed through literature studies, modeling of a chips fragmentation, modeling of the system with several wood chips, development of model for refining in DD refiner and validation of validation models. The research will be developed by a PhD student for four years.

Part 2 New solutions for increased production flow

We will in parallel with the modeling project work together with the supplier company Valmet to develop technical solutions and operational strategies. The aim is to make it possible to increase the production flow in commercial full scale refiners. First part of the project will also focus on providing input data for the modeling work, e.g. pressures, temperatures, geometries, etc. Both measuring and filming in DD-refiner-inlets are planned.


Project period



Project leader

Birgitta Engberg


010-142 88 97

Project members

Johan Persson


010-142 78 94