Production takes place 24 hours a day, every day of the year. Machinery and environmental protection equipment are fine-tuned continuously to meet demands concerning product quality and the environment. Manufacturing pulp and paper is complicated. The results depend on the interaction between raw materials, processes and skilled personnel.
1. The sun is the key source of energy
Using the sun's radiation a tree converts carbon dioxide and water into oxygen and carbohydrates. Carbohydrates are needed for the tree to grow. The structure of the fibres that the tree builds forms the base for pulp and paper production.
2. Wood becomes wood chips
When the logs reach the mill they enter the wood room. The bark is removed in a rotating drum. Then the logs are cut into chips and the chips are stored in large silos or piles. The bark is used as fuel. The chips are then sent to the digester.
3. Cooking the pulp
The cellulose fibres in the wood chips must be parted from each other carefully. This takes place by cooking the chips under pressure together with chemicals. The cooking liquid, or white liquor, becomes black during this process. Around half of the wood becomes pulp. The remainder is dissolved in the black liquor and is used as biofuel in the recovery boiler.
4. Washing and screening the pulp
To remove the black liquor and chips that have not dissolved the pulp is washed and screened in several stages to ensure that no impurities remain. The pulp then goes to the bleaching plant or straight to the paper machine if the product is unbleached.
5. Bleaching achieves whiteness
Bleaching is a process that produces a cleaner, whiter and more durable pulp. The process is in several stages and the chemicals used are oxygen, chlorine dioxide, hydrogen peroxide and caustic soda. The bleached cellulose fibres are now ready to become white paper.
6. Chemicals in the eco cycle
The cooking liquid, or black liquor, is dried and then burnt in the recovery boiler. This produces energy for producing steam and electricity, while the chemicals form a solution at the bottom of the boiler. This solution is dissolved in water to produce green liquor. This green liquor is treated with lime and converted into new cooking liquor (white liquor) which can be returned to the pulp digester. This circulation of chemicals in different eco cycles is a key element in the environmental impact and economy of the mill.
7. Paper production
Cellulose fibres are mixed with water and chemicals and ground together. This mixture, or stock, is poured onto the wire of the paper machine where it forms a paper web. The web is then led through the paper machine through a system of filters and rollers where the paper is dewatered, pressed and dried. At the end of the machine the paper is wound onto massive reels.
8. Coating improves printing results
Some of the paper is coated in special coating machines. By adding a thin coat of white colouring the paper becomes smoother and better sealed and thus easier to print on.
9. Packing the finished paper
The large paper reels are cut into smaller sizes and transported to the packing station. There they are packed to protect them during storage and transport to the customer.
10. Wastewater treatment
In addition to measures carried out inside the mill to reduce emissions from the various production stages, wastewater is also treated externally. The wastewater first enters sedimentation ponds where particles (mainly wood fibres) are separated from the water. Then the water is treated in a biological process where micro-organisms break down pollutants.