An advanced automation system is helping a Swedish pulp mill to generate enough fossil-free energy to meet its own process requirements and produce a huge 550 gigawatt-hour surplus - enough to meet the needs of 24,000 Swedish homes.
Over the past 10 years Swedish pulp producer Södra Cell has transformed its Värö pulp mill in Sweden from a conventional large-scale consumer of electricity and fuel to an ultra-efficient producer of environmentally friendly fossil-free energy.
Not only does the mill produce enough electricity to power the production of 425,000 tons of high-quality chlorine-free pulp a year, it also produces 550 gigawatt-hours (GWh) of surplus energy in the form of electric power, district heating and biofuels.
Of this energy, 100 GWh is sold to the national power grid as green electricity, 150 GWh is district heating for the nearby town of Varberg (population 27,000), and 300 GWh is biofuel that is sold to power plants and industrial users.
All of this energy is provided by the waste bark, branches and wood chips that cannot be sold as sawn timber or used in the pulp-making process. The heat that is converted to district heating comes from the mill’s wastewater and the recovery boiler’s flue gases.
Over the past few years Södra Cell has invested around $300 million in reducing the mill’s energy consumption. The investments include a new evaporation plant to improve energy efficiency, feed water preheating to increase the production of electricity, flue gas cooling to raise the output of district heating, and bark drying to optimize the fuel quality for district heating.
Those investments have been so successful that they have generated new revenue streams for Södra Cell and boosted the company’s competitive strength. In addition the mill now has one of the smallest carbon footprints in the pulp industry and has won worldwide recognition as 'the world’s first fossil-free pulp mill.'
At the heart of Södra Cell’s operations is ABB’s Extended Automation System 800xA, which controls, optimizes and seamlessly integrates every component in the entire pulp and energy production processes at the mill.
System 800xA has an unparalleled capacity to integrate enterprise and plant systems, applications and devices. It improves operations, engineering, control and maintenance, and provides a collaborative environment where real-time decision making is a reality.
One example is its integration of the mill information system with the distributed control system, which enables an unbroken chain of information to run from the customer order through production and into process control. This minimizes manual handling, secures product quality and increases process safety and availability, with minimal consumption of energy and raw materials.
Södra Cell is a long-standing and highly valued ABB customer. The production and energy generating processes at all five Södra Cell pulp mills in Sweden – which together produce 2.1 million tons of pulp and generate 1.8 terawatt-hours of energy - are equipped with System 800xA.
"ABB has supplied the control systems for all the mill processes. The systems are connected in a common interface, which enables us to control what is happening in the various parts of our operations. I would say that ABB is involved in every project we undertake." Ola Walin, maintenance manager, Södra Cell Värö.
