Expansion of chemical recovery capacity by 64%, case study

The massive upgrade of the Södra Cell Värö mill in Sweden was recently completed. The mill's capacity has been increased by 64%, with a new maximum at 700,000 ADMT/year of Northern Bleached Softwood Kraft. This new capacity allows development and reinforcement of Södra's market position. Besides capacity, environmental performance has been a key focus area for improvements, including water consumption being significantly reduced through a combination of 100% reuse of evaporation condensates in the mill and the installation of high consistency wash presses in the upgraded fiberline. The use of fossil fuels had already been eliminated through the installation of a new lime kiln, but with the completion of the expansion project the mill has become even more energy efficient. This allows an increase in production of renewable power and biofuels, which helps the surrounding region to further reduce its use of fossil fuels.

Södra Cell Väro rebuild project scope

A white paper found HERE reviews changes made to the evaporation and chemical recovery boiler area as part of the project and their role in the production capacity increase, improved environmental performance, as well as increased efficiency of the upgraded mill. Valmet supplied almost all the process equipment for the complete pulp mill. The white paper reviews changes made to the evaporation and chemical recovery boiler area as part of the project and their role in the production capacity increase, improved environmental performance, as well as increased efficiency of the upgraded mill.

All given parameters, including information not traditionally shared by the customer, should be evaluated in a plant optimization. With everything taken into account, the evaporators and recovery boiler can be optimized within the context of overall mill upgrade, to meet customer requirements, including optimal energy solutions, the lowest possible environmental impact on air and water, and high availability. The Södra Värö mill upgrade of the recovery island has demonstrated that:

• Increased and more stabilized product solids lower emissions as well as improved the energy efficiency of the recovery island.
• Many different mill effluents can be incorporated in the black liquor evaporation plant to reduce the outflow from the mill and/or allow destruction and chemical recovery in the recovery boiler.
• With hot water production integrated in the upgraded evaporation plant, overall energy efficiency can be increased significantly - here exemplified as hot water that is led to the mill's secondary heating system and also to Södra's nearby sawmill.
• Recovery boiler design upgrades continues to show the potential for additional incremental gains in capacity compared to what was believed to be ultimate limits before.

For more information on optimizing your recovery boiler operation, contact your Valmet representative.