Metsä Group's bioproduct mill in Äänekoski was started up on August 15, 2017. Valmet's delivery to the mill included a recovery boiler, pulp drying line, gasification plant, lime kiln, sulfuric acid plant, and mill-wide Valmet DNA automation system.
All the equipment delivered by Valmet represent the latest technology and are highly energy-efficient. The gasification technology and recovery boiler will maximize the use of bioenergy and make the pulp mill totally fossil fuel-free. The recovery boiler, pulp drying line and lime kiln are the largest in Europe.
The construction of the mill was started in April 2015. The project proceeded as planned and was started up exactly on schedule. Safety was one of the special focus areas in the project. Valmet also emphasized safety onsite with special HSE experts and in contractor cooperation. As a result, Valmet's safety performance onsite was on a very good level for a project of this magnitude.
"This project has been important for us both from the technology and employment perspective. Majority of the technology provided by Valmet was engineered and manufactured in Tampere, Jyväskylä, Ulvila and Raisio. It is our pleasure to rise to the challenge, when a customer like Metsä Group is taking the industry forward with investments of this magnitude. Success in a project like this is made possible by close cooperation between the two parties. Our cooperation has been open and constructive, and we have worked together to find the right solutions," says Bertel Karlstedt, Pulp and Energy Business Line President from Valmet.
"We have a long experience of co-operating with Valmet in our pulp mills in Finland. Throughout the project Valmet has been a good and innovative partner when building the world-class bioproduct mill in Äänekoski," says Timo Merikallio, Project Director, Metsä Group.
The new bioproduct mill in Äänekoski is the largest investment of the forest industry in Finland. Metsä Group's total investment amounted to approximately EUR 1.2 billion. The mill will achieve its nominal capacity approximately a year after start-up. The mill will produce 1.3 million tonnes of pulp per year, along with other bioproducts such as tall oil and turpentine. New bioproducts that already complement the product concept include product gas from bark, sulphuric acid from the mill's odorous gases, and biogas and biofuel pellets from sludge.
Physically the largest of the Valmet delivered equipment is the recovery boiler. The boiler is designed for a capacity of 7,200 tds/d (tonnes dry solids a day). The Äänekoski recovery boiler has multiple high-power features, including patented heat recovery from flue gas to combustion air, enabling the mill to produce 260 MW of electricity and sell 1.4 times more electricity to the grid than it needs for its own operation.
The produced pulp is dried in the pulp drying line, where the pulp web is formed, pressed and dried before being cut into bales.
Individual 250 kg bales are wrapped and consolidated into 2,000 kg units for transportation.
Valmet DNA automation system is the process control and information system for the whole bioproduct mill, and has machine and drive controls for the drying machine. It is also possible to expand the system with additional control and Industrial Internet systems.
At the biomass gasification plant bark is dried using a patented double-layer drying process with material recirculation. Dried bark is gasified to make product gas, which is then used as the fuel in the lime kiln.
Active lime is regenerated in the lime kiln using biofuels. A stationary product cooler is setting new standards for recovering process heat.
The sulfuric acid plant represents Valmet's latest innovations and has been specially developed for this kind of mill. The new technology, which produces sulfuric acid from odorous gases, will enable the bioproduct mill to be nearly self-sufficient in sulfuric acid.