At the cutting edge
We have big ambitions; we don’t want to simply keep pace with the new and ever tougher demands that we face.
We want to stay ahead of them. We are constantly striving to reduce water and air pollution, as well as decrease energy consumption and waste at our facilities.
A tonne of wood makes a half tonne of paper
The raw materials used in Korsnäs’ production come either directly from the forest in the form of round timber or as chips, a residual product of sawmills. The first step is to debark and chip the round timber. Chips are the basic input of the pulping process that follows. The bark is incinerated to produce energy.
In the digesting houses, the chips are cooked at high pressure together with pulping liquor. Wood can be described as a composite material in which the cellulose functions as reinforcing fibres and the lignin as glue. In the digesting process, the wood fibre used
in the end products is released. About half of the wood is dissolved out in the digester – primarily the lignin – and is pumped, along with the digesting chemicals, to the soda recovery boilers. This liquid is called black liquor. En route to the soda recovery boilers, residual black liquor soap is skimmed off and used to produce tall oil.
The lignin is burned in the soda recovery boilers, producing energy that can be recovered and used in the process. Energy produced in the soda recovery boilers covers all of our steam needs and provides much of the electricity we need for pulp production. The pulping liquor in the black liquor are returned to the process in a closed circulation.
In order to minimise emissions of particulates, acidifying sulphur compounds and eutrophying nitrogen compounds, flue gases are treated by a comprehensive system of scrubbers and electrical filters before being released into the atmosphere. This keeps airborne emissions at low levels.
The result of this process is that a tonne of raw material – wood – becomes 500 kg of paper. And a great deal of energy has been extracted along the way. Wastewater from various parts of the process contains residual fibres and dissolved wood substances. In the external treatment facilities, microorganisms break the dissolved substances down into activated sludge, which is composted or recycled.
The wood fibres that have been extracted are washed and screened. Washing is a multistep process. Pulp is washed so carefully because it is used to make paper and board for food packaging. It has to be extremely clean and free of odours and flavours.
After it is washed and screened, some of the pulp is bleached to the desired brightness. White and brown pulp is pumped through the storage towers to paper and board production. The production
process includes shaping, pressing, drying, rolling to produce smooth surfaces and coating in extremely advanced, high capacity machines.
The resulting rolls of paper and board can weigh over 50 tonnes. They are divided into smaller rolls or cut into sheets depending on what the customer wants.