Exploring energy efficient pulping

When paper industry increases the use of mechanical grinding of raw materials, both wood consumption and environmental load is reduced. But energy consumption is increased.

The energy saving potential achieved in the Nordic paper industry recent years has been exploited by replacing more chemical pulp with better quality mechanical pulps. (Photo: Crestock)

The Nordic pulp and paper industry has a leading position in research and development of so-called mechanical pulping which implies making pulp from wood in a mechanical process rather than solely using chemicals. Nordic paper manufacturers wish to keep their leading position. Thus, Nordic cooperation is needed to meet requirements for improvements within this area.

Energy expenses challenging market position

Increasing energy expenses forces the Nordic paper industry to improve production operations. A Nordic project seeks to reduce electricity consumption in operations in so-called mechanical pulping. The properties of mechanical printing paper pulps improve with increasing energy consumption. Therefore, continuously rising energy prices reduce the competitiveness for paper producers in the Nordic countries. As a result of this, Nordic Energy Research has financed the project Basic Phenomena in Mechanical Pulping - aiming to reduce specific energy consumption in the process of making mechanical pulps.

Lower costs, lower emissions, less use of raw materials

In addition to a need for lower costs, better knowledge on how to save energy in paper production may reduce the environmental load linked to paper production. Increased atmospheric CO2 being a global challenge, any reduction of electricity consumption is a contribution to the global effort of reducing green house gas emissions. - A huge amount of electricity worldwide is made from fossil fuels. Mechanical pulping also reduces the total amount of raw materials needed to supply the world with paper.

Radical reduction needed

Pilot studies have indicated that energy savings up to 30 to 50 percent might be achieved in mechanical pulping. The main objective of the Nordic Basic Phenomena in Mechanical Pulping project is to show a radical reduction of the specific energy  in the production of mechanical pulp. The project also have other objectives, such as getting to know the wood raw material better in order to show how the fibres correlate with the power consumption. The energy efficiency of mechanical defibration processes is probably quite low. A major part of the electrical energy supplied is transformed into heat in the processes. According to estimates, only some 5 to 20 percent of the energy consumed in the process goes into the actual production of the mechanical pulp. By getting to know the wood raw material better, the outmost goal for the working group is to propose methods for energy savings. 

25 percent of Finnish industrial energy consumption

With rising energy costs, the consequence of saving energy in the mechanical pulping sector has an important impact on the future competitiveness of the Nordic pulp and paper industry. The Finnish industry consumed electrical energy in 2002 was roughly 42 TWh of which close to 25 TWh was consumed by the pulp and paper industry. The share of the mechanical pulp production was some 10 TWh. The Swedish pulp and paper industry consume about 23 TWh of a total industry consumption of 56 TWh. The share of the mechanical pulp production was about 7 TWh. In Norway the amount of energy used for mechanical pulping is lower.

Further reading:

Basic Phenomena in Mechanical Pulping [Nordic Energy Research]

Basic phenomena in mechanical pulping

The project is being conducted as a Nordic cooperation project financed by Nordic Energy Research and paper industry representatives Metsäliitto Group, Myllykoski Corp., Stora Enso, UPM, Holmens, Norske Skog and SCA.  Partners in the project are Mid Sweden University – FSCN, the Finnish forest-industrial research centre (KCL), Norwegian University of Science and Technology (NTNU), Tampere University of Technology (TUT) and Helsinki University of Technology (TKK).

The mechanical pulp project is trying out new techniques and materials at KCL's facilities in Espoo. Scientists at the Mid Sweden University analyze the properties of wood and determinate stress-strain relationships for different wood materials at high strain rate. Researchers at the Tampere University of Technology simulate the mechanical pulping process. Scientists at the Norwegian University of Science and Technology in Trondheim, Norway, study changes in the pulp at fibre level. At the Helsinki University of Technology scientists measure changes at the surface of the individual fibre.

Final conclusions are to be presented in autumn 2009.