Äänekoski – A mill for the 21st century

Metsä Group’s Äänekoski bioproduct mill has been the talk of the global pulp and paper industry for some time now with its outstanding environmental efficiencies and ambitions for new products derived from wood. Starting up in August 2017, ANDRITZ supplied crucial technology to help make the bioproduct mill a showcase production site for the 21st century.

The environmental and sustainability statistics coming from Metsä Group’s new bioproduct mill at Äänekoski in Finland are truly impressive: the mill will produce 1.3 million tonnes of pulp a year from 6.5 million cubic meters of wood with zero use of fossil fuels at the same time as using only 10 m3 of water per tonne of pulp.

Timo Merikallio, Project Director, has been leading the charge at Äänekoski as the 1.2 BEUR project went from planning to fruition at start-up on August 15, 2017. Merikallio says, “The decision to call Äänekoski a “bioproduct mill” was almost a natural occurrence. At the outset of this project, we started looking at a wider scope and looking deeply into what other products could be made, in addition to, of course, our leading bioproduct, which is pulp.

ANDRITZ was chosen to supply major, critical technology at the mill to ensure that the Metsä Group’s sustainability and environmental demands were met across the board. The order included the very latest, world-class technology for the woodyard, fiberline, evaporation plant, and recausticizing plant. The core equipment supplied by ANDRITZ originated largely from Finland - domestic content was nearly 80% - and thus had a significant positive employment impact on ANDRITZ’s engineering staff located in Kotka, Lahti, and Varkaus as well as on the ANDRITZ workshop in Savonlinna where a big part of the core equipment was fabricated.

L to R): Mika Mäkelä, ANDRITZ Project Director for the bioproduct mill; Camilla Wikström, Mill Manager; and Timo Merikallio, Project Director from the bioproduct mill.

© Behrend & Rausch


Metsä Group was adamant that it wanted the very best and most efficient equipment when it came to energy savings for this mill. Johan Engström, Chief Technology Officer, ANDRITZ PULP & PAPER, says, “A major source of revenue for the bioproduct mill is bioenergy production, so any energy saved in the process means extra revenue directly onto the bottom line.

“We accepted this challenge and looked very closely at every area where energy savings could be made; for instance, for the first time, we integrated a separate evaporator unit – Digester Evaporator (DeVap) – into the fiberline. This makes a big difference to energy efficiency, as 100% of the direct steam to the digester top is replaced by secondary vapor from the DeVap. The DeVap increases dry solid content of the black liquor and therefore less evaporation capacity is needed in the evaporation plant."

ANDRITZ also installed a new type of bark press – the HQ-Press – which increases the dry solid content of the bark. Engström says, “What the new, highly efficient bark press does, mechanically saves a lot of energy in the subsequent processes.”

ANDRITZ latest technology for water management is also implemented into the mill, which has resulted in emission reductions but also increased energy savings. Engström adds, “To deal with emissions, it makes sense to reuse the condensates and filtrates we already have in the loop. This not only minimizes the emission problems, but is also great for energy savings as there is no fresh water that needs to be heated up.”

The woodyard order consisted of a complete wood processing plant with three debarking and chipping lines, chip handling systems with three stacker reclaimer-type chip piles, and complete bark handling and storage. Each debarking line processes both hardwood and softwood and is designed for world record capacities using pine, spruce, or birch.

The softwood and hardwood fiberline comprises a TurboFeed chip feeding system, a two-vessel Lo-Solids cooking plant and brownstock and bleaching plant based on DD-Washers. The softwood capacity of the line is the highest in the world at 3,900 tonnes per day.

ANDRITZ delivery included the world’s most energy-efficient black liquor evaporation plant. The evaporation plant has the highest capacity in Europe, at 1,650 tonnes per hour and is one of the world’s largest single line recausticizing plants with a white liquor production of 16,000 m3 per day.


 “We are proud to say that the Äänekoski mill is using the same environmental permit that was granted for the original mill it replaced – even though the mill is two and a half times bigger,” adds Wikström.

Metsä Group is also encouraging other bioproduct companies to join the mill, forming a cluster of biotechnology expertise that can make use of the side streams, as well as take advantage of the onsite energy and water management facilities. Wikström concludes, “EcoEnergy SF Oy is using our sludge as a raw material to make biogas for use as fuel for cars, as well as solid fuels that are produced in the form of pellets. I am quite sure we will see a lot more innovation in bioproducts around the Äänekoski mill in the future.”

© Behrend & Rausch
© Behrend & Rausch