With the goal of reducing its environmental impact, Sunila mill has implemented an additional component to its evaporation plant able to greatly reduce its COD (chemical oxygen demand) emissions and water intake while generating more green energy from its process.
The “Duct Stipper” technology, provided by Andritz, collects condensates from the evaporation process and sprays them into a secondary vapour duct, in an evaporator train, in order to strip organic volatile gases out from the liquid. Purified condensates are then re-used in the Pulp process, keeping them from being rejected into the effluent. The secondary condensates from evaporation contributed to 20% of the mill’s COD load. By applying this state-of-the-art technology, Sunila will be able to reduce effluent flow from the evaporators by about 60% (with a 75% reduction of methanol flow) while also reducing the water intake.
The evaporation plant handles considerable volume of water every day. Thanks to this investment, Sunila will reduce its process consumption of fresh water by 5.5m3 per tonne of pulp. On a yearly basis, this will represent a fresh water reduction of over 2 million m3.