Lignin, a component of wood, will be extracted from pulp mill black liquor using the LignoBoost system patented by the Finnish company Metso, after which it is dried, enabling pulverized combustion. The dried lignin could replace 90% of the natural gas currently used as an energy source by Sunila mill’s lime kiln, representing 172,000 MWh per year. This would reduce carbon dioxide emissions by an estimated 33,000 tons per year.
According to Metso, when a recovery boiler is the limiting factor to increasing pulping capacity, LignoBoost is a good solution to the problem. If 25% of the lignin in the black liquor is removed, boiler capacity can be increased to enable 20-25% more pulp production. Metso believes that as the technology becomes commercialized, LignoBoost could be sold to many factories worldwide. One plant has already been sold to the United States.
Sources: Ministry of Employment and the Economy, Stora Enso, Metso