Interview with Per Engstrand of Mid Sweden University

10 February 2010

Interview with Per Engstrand of Mid Sweden University, the Chair and a speaker at Pira's Refining and Mechanical Pulping conference

Q: You are chairing the session on improving energy efficiency in refining. Why has this area become so important in recent years?
As energy prices have increased rapidly during the recent years the cost of energy can in some cases correspond to close to 50%of the production costs. The raw materials used for paper making - wood and recycled paper can also be utilized as energy. This means that we can expect rapidly rising pulp wood and recycled paper prices. Especially, once capacity to use these materials for energy production (outside the pulp and paper industry) will be large enough, which seems to be happening very soon. There are large investments already in UK and Germany in this area.

Q: What changes can industry make to the refining process to increase energy efficiency?
This is a very difficult question. My experience in this area tells that there is not one solution to this. The things we have been working with for a while and that seems promising are the following:

• Wood chip pre-treatment strategies involving very well controlled disruption of the wood chips combined with well optimized chemical strategy. (Work published at IMPC2009 by Jan Hill Norske Skog, Marc Sabourin Andritz and Johan Aichinger Andritz and Lars Johansson PF)
• There are many studies published by suppliers on energy efficiency in chiprefining with a large extent related to improving understanding of refiner plate designs. There is also study on increased chip refining temperature in combination with increased intensity by means of plate design (Dino Muhic presentation at the PIRA meeting).
• In the area of second stage refining and reject refining there is a project in the area of LC-refining adapted to mechanical pulps. It was started many years ago but lately more forceful development work is done by Holmen Braviken's investment in a LC-machine from Andritz within a large R&D-Demonstration project (mentioned at the previous PIRA meeting by Christer Sandberg - Holmen). Hans Höglund of FSCN - Mid Sweden University, while being Research Director at SCA, has shown already how second stage HC-refining could become twice as efficient as conventional by raising the refining temperature from 140 to about 180C at the same time as the gap distance is reduced.
• If fractionation (screening and cleaning) is optimized correctly with reject refining, it can also be used to reduce energy consumption, plus enhance the pulp quality.
• Even the optimization of the paper or paperboard production processes has an influence on what energy consumption we need to use in the mechanical pulping plants.

Q: What are the biggest challenges to increasing energy efficiency?
A difficult issue is that the investment cost to perform changes suggested above can be too high for the internal prioritizing policies within the pulp and paper companies. It is often important to understand how to combine the need for improved product quality, production efficiency etc, with the courage and knowledge to dare to invest in new solutions. Another common problem is that energy issues, despite the high pricing, are not discussed as much as it should be in the mills / production lines. It is difficult enough to reach the targets regarding quality and production.