Lignin from pulp mill black liquor

A LignoBoost plant needs two vertical plate pressure filters to dewater and wash the lignin. Metso developed these filters for the high demands of the mineral industry. This means the equipment successfully combines top performance and high-level automation with easy maintenance and low total cost. LignoBoost works in conjunction with evaporation, first by precipitating lignin and sodium from the black liquor by lowering the pH with CO2. The precipitate is dewatered by using a filter press. LignoBoost then overcomes conventional filtering and sodium separation problems by re-dissolving the lignin with wash water and acid. The resulting slurry is once again dewatered and washed to produce virtually pure lignin cakes. The lignin can be exported or,after final drying, used as fuel in the lime kiln.

LignoBoost represents a technology that extracts lignin, a component of natural wood,from the chemicals used in the pulping process. The extracted lignin can be used as biofuel, replacing coal and oil, e.g. in pulp mill power generation or in lime kilns. The potential saving is 50 l of fuel oil per ton of pulp (5,000 m3 of oil per 100,000 tons of pulp).LignoBoost gives Metso’s customers the possibility to increase pulp mill capacity and turn pulp mills into significant energy suppliers. At the same the extracted lignin is also of interest to other process industries as a raw material for plastics, carbon fibers and chemicals.