Producing pulp requires a lot of energy. Drying the pulp and evaporating water from black liquor – a by-product of pulp production – are especially energy-heavy processes.
“The dryer consumes most of the electricity but most of the heat is used in the evaporation plant, as it evaporates water from black liquor before burning the liquor in the recovery boiler,” says Aleksi Nurmi, Production Manager, Recovery at the UPM Kaukas pulp mill.
As part of its energy saving initiatives UPM has focused on improving the energy efficiency of these phases of the process. The most recent significant investments have been made in an electric boiler and a turbine for the recovery boiler at the Kaukas mill.
Cleaner energy from electric boiler
Although the investment in a new electric boiler actually increases the mill’s use of electricity, the boiler’s increased efficiency improves the pulp mill’s energy consumption and significantly reduces emissions.
“The electric boiler will provide fossil-free auxiliary heat to the different units within the mill integrate when necessary, whereas previously auxiliary heat was produced by boilers fired with natural gas,” Nurmi explains.
In addition, the new turbine on the recovery boiler significantly increases the share of surplus renewable energy produced in the Kaukas mill.
Pulp mills are steady producers of electricity
The surplus energy produced by UPM’s Finnish pulp mills can provide heating for up to 20,000 middle sized detached houses with electrical heating. A pulp mill is a significant power plant, producing energy at a constant rate rather than being dependent on weather conditions.
This energy is around 98-99% renewable – mainly produced by burning black liquor, which is a mixture of spent cooking chemicals and dissolved wood material. Fossil fuel is only needed momentarily during maintenance shutdowns and start-ups.
Aiming to improve energy efficiency every year
In order to constantly improve energy efficiency, UPM has carried out regular energy audits at its pulp mills since 1997. After each review the audit team presents a list of potential energy saving suggestions.
Aleksi Nurmi sees that energy efficiency targets also serve to promote innovative technology solutions and sustainable development practices.
“Our skilled staff is positive about the changes and working together to find ways of operating the pulp mill more efficiently,” he says.
