There are quite a few steps to the process of turning trees into premium office paper. We take pride in doing it with great devotion and attention to details – two out of many ways in which the Multicopy staff ensure that the raw material turn into premium-quality paper, every time. Once the wood is harvested and transported to Nymölla Mill (most of it from less than 100km radius) it’s time to turn the raw material into pulp.
Pulp is the foundation of paper. The mission with the pulp mill is to separate the cellulose fiber from the lignin and other wood substances, which is done in large pressure vessels called digesters. Lignin is a complicated chemical compound which connects wood fibers to each other.
There are two types of processes that can be used to remove the lignin from the wood chips; sulphite or sulphate. At Nymölla mill where Multicopy is produced we are using the magnesium based sulphite process. A great benefit of the sulphite process is easier bleaching methods. Both the sulphite and the sulphate processes are chemical pulping, combination of wood chips and chemicals.
The wood raw material consists of roundwood (mostly spruce, pine, beech and aspen) and sawmill chips. In the woodroom, the wood is debarked in 25 metre-long barking drums and chipped. The bark is collected, dewatered and burned in the boilerhouse to produce energy. It is essential that each chip is the right size and is cut at the correct angle. Everything is carefully calculated so that the lignin that holds the wood fibers together is dissolved to just the right extent during cooking.
Soft wood chips must be stored in chip piles for about 6 weeks to break down resin and other extractive substances. The huge pile of chips is used up section by section, to ensure that we are using chips that have been stored for the requisite length of time. After storage, the chips are transported to the digester.
During the cooking of the chips, the cellulose fibers are separated from the lignin and other wood substances, which are dissolved in the digester liquor. This consists of magnesium bisulfite, which is why the pulp is called magnefite pulp. Cooking is done in batches, each of which cooks for approximately eight hours.
After the chips have cooked to paper pulp, the pulp is screened and washed. The digester liquid, with its content of dissolved wood substances and digester chemicals, is separated from the pulp in a form known as weak liquor.
The recovery process for digester chemicals includes the evaporation of the weak liquor to thick liquor, combustion of the thick liquor in two recovery boilers and the preparation of new cooking liquor from the recovered chemicals. The recovery rate for digester chemicals is at least 95%. In addition to the recovery boilers, there is a solid fuel boiler. In this, bark, twigs, screening rejects, fuel chips, ultrafiltration concentrate and sludge from the wastewater treatment plant, as well as oil and LPG, are burned. The steam from the boilers is transported to two back-pressure turbines that produce approximately 30 MW of electrical power.
After screening and washing, the pulp is bleached. Oxygen, sodium hydroxide and hydrogen peroxide are used as bleaching chemicals. All the pulp produced at Nymölla is thus totally chlorine-free (TCF) pulp, since no chlorine-based chemicals are used for bleaching. The bleaching process takes from 8-12 hours. After bleaching, the pulp is screened one last time.
Keep an eye out for ”From wood to fine paper, part 2: Paper making”, it will be presented shortly/later this season.
You might think that a paper producing company would look upon digitalisation as a threat. There sure has been much talk about “digital vs print” the last decade. In Stora Enso’s case, that assumption is as wrong as can be. We see the bigger picture. Digital solutions are helping us make the most out of every tree we use, and they are taking us closer to the goal of a safer and more efficient industry.
As the renewable materials company, Stora Enso is leading the way towards a fossil free future. Sustainability is at our very core and in every part of our business. The workplace environment is one important area. Because no company, no matter how green and clean, is truly sustainable if it fails to safeguard the health, safety, and welfare of its employees.
Jonathan Bakewell has been at Stora Enso for 34 years. He quite often gets questions like “What’s the biggest difference since you started out?” and “Was it better in the past?” and yes, he also gets a few “three decades at the same company, what’s wrong with you?!” However, Jonathan is still glad to be a part of this company’s mission to lead the way towards a fossil free future. Proud and inspired after all this time. That says a lot, doesn’t it? This is his Stora Enso-story and some thoughts on the major changes in our business area since 1987.